Monday, August 31, 2009

Indian Monsoons, hydropower, and the supply of natural gas to the USA

I recently wrote about the increasing volumes of natural gas that were coming available as LNG from countries such as Qatar, just as the development of the gas shales in the United States was creating a glut of gas in the United States. We have seen the impacts of the glut in the drop in prices, a fall that still continues and the long-term decline in the number of rigs being used to drill for NG. Interestingly, and a comment on the growing preponderance of wells in the gas shales, the number of horizontal well drilling rigs has fallen, this year, less than the number of vertical rigs. However there is now a slight resurgence in drilling (up 7 horizontal and 13 vertical rigs). Given the potential that a global surplus of LNG might bring more to American shores, undercutting the price of the shale-sourced gas that rise in the number of active rigs might seem a little odd. But there are a couple of thoughts that should be born in mind.

The first is that the world needs natural gas as an energy source, and this is particularly true in Asia, where the potential partial failure of the monsoon with 40% of India being declared drought areas, means that there will be less hydro power available than in normal seasons. So far the rains are 25% below normal (an event which I noted earlier has been tied to El Nino events. One of the ways that India is hoping to solve its chronic shortage of electric power has been by a greater commitment to hydro-generation.

Hydropower is viewed as more flexible than most other sources of fuel, which is important to India, where much of the demand is domestic.
As an illustration, if the approximately 150 million households in India were to turn on two 100 watt light bulbs at 7 pm, the power system would experience an instantaneous surge in demand of about 30,000 MW! Today, this peak demand is often met by households turning on small gasolene and diesel generation units, which, in addition to being polluting, are a serious health hazard in congested areas. And, with rising wealth, households are switching on a lot more than two light bulbs. Although hydropower plants are subject to daily and seasonal variations in water flows (which affects the production of electricity at that point in time), they are not subject to the fluctuations in fuel costs that trouble thermal power plants.
Thus the country is negotiating with the World Bank for increasing support for hydro projects. But they need rain.

Unfortunately, at the moment, power supplied from existing plant is down 10% from last year, while demand has risen. The water levels in the reservoirs, for example, should normally rise by about 5% over a monsoon week, last week it was only 3% . Given that hydropower provides about a quarter of the nations generation capacity this could put further strain on the national economy, where the back-up bill is estimated to be $26 billion a year, and the cost of the outages alone totals some $9.2 billion.

So where can additional power be obtained. One solution is through increased use of natural gas and Qatar’s RasGas has just agreed to increase LNG supplies by 50% starting in November, upping the tonnage from 5 million to 7.5 million tons per year. This comes at a time when India is developing its own gas supplies , but while they equate to 880 – 1,000 mcf/day, demand rose to 9,800 mcf/day last year (up 25%). Thus the increased need for the LNG cargoes, and the current purchase raises the shipping to 120 cargoes a year.

At the same time Turkey has been visiting Qatar seeking to improve its imports of natural gas (currently via LNG) but with the hope, down the road, of seeing the gas shipped by pipeline. The current target is some 140,000 mcf over the course of a year (average of 383 mcf/day). Some of that supply will come from production originally aimed for the UK where demand has fallen.

But if it also reduces the volumes that might otherwise be targeted toward the US this winter it will potentially stop the continued slide in US prices and help the industry, though not the consumer. Perhaps it is in that hope that rig numbers are beginning to creep up.

The second thought is that the production from gas shale wells is very short lived (60% production in the first year) and thus starting up new production to replace the older declining wells is a smart thing to do, and someone is probably tailoring that into their calculations as they place new well orders.

Read more!

Sunday, August 30, 2009

Oil well pressures - what brings out the oil

Michael Lynch would have it believed that those who follow this site are relying purely on “anecdotal information, vague references and ignorance of how the oil industry goes about finding fields and extracting petroleum,”, so I’m here again proving him wrong. Here, on Sundays I give a little of the technical background so that those interested can understand more about the realities of production. The posts are a simplification of what goes on, but give enough detail that, hopefully, it is understandable (and if not then you should ask questions). The posts build on an original set I wrote for The Oil Drum four years ago, but are a bit expanded. Interestingly four years ago Michael was spouting the same sort of stuff and getting it wrong back then too.

This post is going to deal with some of the problems that a driller encounters as he reaches the layer of rock (the reservoir) in which the oil or gas is being held. And what I want to talk about is something called Differential Pressure, but to explain that, I need to drag you back to High School for just a minute.

Let's, in fact, go back to Newton's Three Laws. And, for those who slept through that part of the Physics class in school, don't be too ashamed - I have seen the desk where Newton whittled his name, being similarly bored. Let's start with the first law, which is probably the most relevant.
Every object in a state of (rest or) uniform motion tends to remain in that state of (rest or) motion unless an external force is applied to it.
Except that I want to change external force into pressure (which is force divided by area) since it is the way we normally think of it. (Note: I added rest which is a special case of uniform motion since that is specific to the oil we want to talk about). In other words, nothing is going to move unless something pushes it. It is what does the pushing and what does the moving that this is all about.

And now our drill, is down through the casing, drilling the well open hole and using the circulating mud to carry away the cuttings as it continues to go deeper. I had stopped progress last week just before we went down to total depth (TD) of the well, or into the pay. And the reason I did has to do with this differential pressure. But first, the bit about how you calculate pressure.

As you go deeper into the earth, the rock at any layer is carrying the weight of all the rock vertically above it. For rough calculations we generally consider that this rock weighs 144 lb a cubic foot. So that 10 ft down the weight of the overlying column on a square foot would be 144 x 10 = 1,440 lb/sq ft. But through convention we reduce the area that we talk about to a square inch (144 sq in= 1 sq ft) so with this division the weight on a square inch would be 10 lb. A remarkable resemblance to the depth number (grin). This means that we can assume, as we go deeper into the earth, that the pressure on the rock increases by 1 lb/sq. inch (psi) for every foot we go deeper. This means that at 6,000 ft, the rock is under a pressure, from the rock above it, of 6,000 psi.

Now water does not weigh as much as rock, but can be approximated to roughly half the weight. So that, by the same argument, under water, for every foot of depth the pressure goes up roughly half-a-psi. So that at 6,000 ft under water the pressure is 3,000 psi (roughly twice the water pressure in the wand you use at a car wash). Now because we have increased the density of the fluid in the well (the mud) to help lift the cuttings out of the hole it weighs a bit more than water, but for the sake of working the example I'm going to use the half-psi measure for now. We are now at the point where the actual amount that it weighs becomes important.

Simplified sketch of an oil bearing layer in the ground.

I have made a very simple sketch of the layer of rock that we are going to drill into. In order to trap the oil it is shaped into a dome, and the sketch shows a vertical slice through that dome, viewed from the side. It has a layer of oil in it (the reddish layer), but above that is a layer of gas that has diffused from the oil (brownish), and below it is water (bluish) which may have been there when the algae died and which has stayed with the remains as they turned into oil under the temperatures and pressures deep in the rock. Oil floats on water, and gas is lighter than oil, so we have the three layers. At the moment the well has not arrived and all three fluids are sensibly in equilibrium at the same pressure.

Now why do we need to know this before we reach our layer of oil-bearing rock? Well first let's go and interpret that first law a little more.

If a person on either side of you pushed you with equal force at the same time, you don't move, because the two forces balance out. It is only if there is one force, or if one of the two pushes harder, that you move. In other words, where there are a number of forces acting on a body, it is the size of the difference in pressures, and the direction of that difference, that controls the movement.

Consider, here we are drilling merrily away (and have cased the well near the surface, and hit no more fluids on the way down) and at 6,000 ft. we penetrate the rock that is capping the well, and enter the rock with the oil in it. The oil (in the rock) is at some fraction of the overburden pressure, since it is trapped in the rock, and for the sake of this example I am going to say that it is at 5,000 psi , the fluid in the well is at 3,000 psi, the height of the mud column.
There is a difference of 2,000 psi. We are drilling a hole some 6-5/8th inches in diameter. That has an area of about 34.5 square inches. The total force we have suddenly applied to the bottom of the well (bit and fluid) is thus (area x pressure difference) 34.5 x 2,000 = 69,000 lb (or 35 tons). Oops!

Oil rig blowout in Turkmenistan (Energy Industry Photos)

Sadly most catch fire and the rig is destroyed (there are more pictures of such damage at the EIP site)
It's called a blow-out, and they still happen.

This is why we approach the oil/gas producing zone of the rock with caution. And bear in mind that the driller that is controlling the progress of this well is at the surface, trying to guide the bit at the bottom of the hole, with, historically, little immediate information to help.

Based on the surveys that brought the crew to the site in the first place he knows roughly how thick the layers of rock are, and probably what rock they are, but the only real information on where the bit is in that sequence, is from the returns (cuttings) that come out of the well, and there is the lag, we mentioned before, while those chips make their way up the 6,000 ft pipe. (This is why Measurement While Drilling [MWD] has been such a relatively recent boon to the industry ( though not all rigs have it).
By monitoring a number of pressure gages the driller can gain a sense of what is happening at the bottom of the well.

If he senses that there is going to be a problem, then he can do one of several things, based on the way the well is set up.
The first thing is to increase the density of the mud. By making the fluid in the well weigh more, the difference in the pressure across that face is reduced, and the change in conditions is easier to handle. However weighting up the hole has the disadvantage that it becomes much slower to drill with a heavier mud (it is a poor bottom-hole cleaner among other things). And, if done during drilling, bear in mind that once the heavier mud is added to the well it won't be fully effective until it has had time to get down to the bit and then fill back up the annulus between the drill string and the casing all the way to the surface.

So that is an expensive and slow option. Let us take the game a little more interesting and say that there is a gas pocket above the oil, and that the hole is going to go into the layer at A. Gas will enter the well at the down-hole pressure, but as the bubble rises, that pressure is reduced, and the gas expands, pushing the mud above it out ahead of itself. Another potential source for big-time trouble. And this one (which is known as a kick in the well) happens much faster, so there is less time to react.

How do we handle this? The answer is to invert the problem. Gas or oil flows into the well because the well is at a lower pressure than the fluid in the rock. The fluid in the well is, initially at the pressure created by the depth, and by the weight (density) of the mud in the hole. However, if we put a restriction on the flow of fluid out of the well (such as when you put your finger over the end of a garden hose so that the stream becomes smaller and shoots out further) we can increase the pressure in the well.

For those who want to know why, if the same volume has to go through a smaller hole in the same amount of time it has to go faster. This means it has to be pushed harder. Bernoulli explained it, and there is an animation available that helps explain it.
What it means is that by adjusting the flow out of the hole, the driller can adjust the internal pressure, and thus "kill the kick", or if gets to be too much of a problem, “kill the well”. But it is not completely that simple. Bear in mind that there is all the drilling and rotating equipment on the rig floor connected to the drill pipe at the top of the well. None of this can stand much pressure. So we need to place another piece of equipment between the drilling rig, and the top of the well.

Blow-out preventer (Schlumberger )

This is the Blow-out Preventer(BOP), which is essentially a ram that very rapidly shuts off fluid flow at the top of the well. These have to be well designed, since they are generally the line of last defense against a blowout, and when they fail as the pictures show serious problems arise. They also form the basis for the well-known structures, often referred to as Christmas Trees, that sit at the top of producing wells. By themselves, however, these aren't enough, since their main function is just to slam the door shut, before all the oil gets out and we have a gusher.

The more critical tools are the chokes on the well. (Below the rams in the picture above). There are generally several, both hydraulically operated and manual (in case the power dies) which are simply large valves that can be turned to increase or reduce the size of the flow path out of the well over to the mud pits. By adjusting these, in real time, the driller can control the well pressure, and thus the dynamics of the behavior at the bottom of the well. And after the rig leaves, an operator can adjust well pressure, and thereby the production from the well and its long-term performance.

If the operator is well trained (and you find drilling simulator equipment in Petroleum Engineering Departments so that students can understand how to do this (I last tried some decades ago) the well pressure will be controlled, so that any kicks can be handled, and the drill can now penetrate safely into the rock containing the oil/gas, which we call the reservoir, or the pay.

And you think the hard part is over?

Once the drill has penetrated through the layer, and the well has been completed, it is the controlled difference in pressure between the fluid in the rock and that in the well that will move the oil into the well, up and out into the pipeline. But we’ll talk about that when we talk about well completions and production in future posts.

As usual comments, questions and criticisms are welcomed. BTW if you're impatient with the speed of these posts, there is a lecture series on all this available from Rigzone, with videos. I haven't seen it, but I noticed it while looking for sources of pictures.

Read more!

Saturday, August 29, 2009

Water problems in Nepal

There is a growing tendency to assign the cause of weather events that badly impact different populations to climate change, and thereby to add additional “evils” to those who generate “greenhouse gases.” I noted this last week about the story of the Nile Delta and the causes of erosion and lack of fertility that farmers are now seeing. As I showed the events have nothing to do with climate change or AGW, despite the bits of the story that implied that they were.

The events don’t even have to have happened yet. This week Oxfam International were pointing to the change in climate threatening the livelihood of the people of Nepal.
Nepal will likely suffer more frequent droughts because of climate change, Oxfam International said in a report released in Kathmandu. River levels will decline due to the reduced rainfall and glacial retreat, making it harder to irrigate crops and provide water for livestock.
Now here is the problem that I have with that last sentence. When there is precipitation in the mountains, it is either retained in the mountains as ice and snow, or it goes into the rivers where it is available for irrigation. If glaciers grow then less of that precipitation is available for irrigation, if glaciers retreat, that means that they are melting and not only not capturing the precipitation but are also providing some of their stored water to be available for irrigation. This supply of more water is a resource critically needed in China as well as Nepal, and provides the great rivers that flow from the Himalayas and are relied on by millions of people.

The report itself is a integrated mix of things that might happen if the global temperature increases by 2 degC by 2050 (35% of the Himalayan glaciers are projected to disappear) and a recent winter drought that has left many farmers without adequate food supplies.

However this has been a poor year for the monsoon in India, and Kumar et al have shown that the failure of the monsoon correlates with El Nino events – something that we are now moving into.

Thus the actual events that are reported in the Oxfam report have a cause that is likely not due to global warming but to a predictable and regular other cause. However, by combining the effects of the drought and the poor weather, with the predicted events that might occur with a dramatic increase in global temperature, a confusing picture of contradictory predictions has been built. Monsoons, sadly, have failed before, and for the same reason.

It is understandable that folk seek to find a scapegoat when the weather is inhospitable, however, as with other countries, an additional part of the problem in Nepal arises from the increase in population, particularly in the Kathmandu Valley. To solve the problem the government has just laid the foundation stone for a 26.5 km long tunnel to bring 170 million liters of drinking water a day (MLD) into the valley. It is known as the Melamchi Drinking Water Project and is due to be completed in 2013. The work is being carried out by a Chinese contractor. The valley needs some 240 MLD and can supply only 90 MLD, for the 2 million inhabitants of the valley. Most of the rain (it gets about 1.5 m/year) comes in the monsoon season between June and August.

It has not met with universal approbation and does not help those living in the hills. However they have other problems since while the communities live on the tops of the hills, the water is in streams in the valleys and so women and children can spend up to 4 – 6 hours a day just carrying water. There has recently been an innovation – called the Large Fog Collector (LFC)
The Large Fog Collectors (LFC) are constructed using 4 x 8 meter sheets of polypropylene mesh, which when suspended on a ridgeline resembles a large volleyball net. Warm air from the Bay of Bengal moves inland during the monsoon, where it intercepts the varied topology of the Himalayan foothills. As the air moves up into valleys at higher altitudes, it mixes with cooler air and condenses, forming fog. As fog passes through the fog collectors, water droplets cling to the weave of the mesh, and filter down into a discharge system that stores the water in 20,000 liter ferro-cement tanks. Water quality testing found that all parameters meet WHO guidelines. . . . . . . . Here six large fog collectors produce an average of 1700 liters of water per day for the villages 75 inhabitants.
Although relatively cheap they do require both maintenance and frequent fog which they get in Nepal, Peru and Chile.

The glaciers in the Himalayas occupy some 193,000 sq miles and at present the melting and retreat of the glaciers, which has been been going on since the end of the Little Ice Age, has accelerated since 1970. It is the melting of the glaciers that provides the water for the rivers and people that they serve, and provide a supply of water in the seasons that the rains don’t fall. It will be interesting to see if the changing global climate conditions of this century have any impact on the melt rate.

The nations that are served are thus in a bit of a cleft stick, since during the Little Ice Age the glaciers grew, and thus supplied less water to their dependants than they do now, so the current melting does have some benefits, that should be recognized.

But if it continues too long then the water resource will be gone - depending on how the temperature actually continues to rise, if it does, this is going to lead to a difficult conumdrum, though likely over a longer time period than is currently being used as a discussion point.

On the other hand (h/t Marc Morano) when Asia gets hotter, then in the past the glaciers have started growing again.
A group of Himalayan glaciers grew six-fold during much hotter summers, when temperatures rose steeply by six degrees Celsius in Asia, baffling geologists.

Read more!

Wednesday, August 26, 2009

Camelina - a relatively new US biodiesel source

So what the heck is Camelina? Until I read that it was used as the greater source of the biofuel component for the test flight of the Japanese Airlines plane in February I must confess I had never heard of it. So since it has obviously got some legs (there was a greater percentage of it than of the algae derived fuel) herewith some thoughts picked up as I wandered through some Web pages, seeking more information.

Camelina in a Montana test plot

Apparently it came to the United States out of Europe, though it started out in Central Asia and the Mediterranean. In Europe much of the early cultivation of the crop has been replaced with canola fields, and it appears to compete with it as a crop. It arrived in Montana in about 2004 where it appealed both to farmers – as a source of omega-3 fatty acids, and to researchers who were looking for a source of biodiesel. The early work suggested that it could be sold more cheaply ($2 a gallon in 2005) than soy-generated biodiesel ($3 a gallon), but a cheaper price is hardly guaranteed to induce farmers to grow it. The oil has historically been used for cooking, with the meal fed to animals.

Recent interest in the plant was spurred by the omega-3 content
there is renewed interest in Camelina for its oil which is rich in the omega-3, alpha-linolenic acid (ALA).Ironically, this quality had contributed to its decline, due to difficulties with hydrogenating the highly unsaturated oil for margarine. Linseed (60% ALA) and Camelina (45% ALA) oils are by far the richest plant sources of omega-3.Rapeseed has lower levels of ALA (10%) and sunflower almost none. Camelina oil is more stable than linseed, due to its natural antioxidants, which also have health benefits in their own right.
It is a branch of the mustard family, and has the benefit over canola in that it is resistant to flea beetles, which are a problem for canola in Montana. Like canola it prefers cooler climates;for greatest yields being planted before the 15th – 20th March in Montana with harvesting in Late June to late July. (Similar dates hold for planting and harvesting in Wales.) Thus in 2006 there were somewhere between 7,000 and 20,000 acres planted in Montana, in 2007 this grew to 24,000 acres. It also has the benefit, over canola, of being able to survive drought and spring freezing. Further there is a winter variety that can be grown in areas with mild winters. The report from Montana State describes the oil content as:
Camelina oil has unique properties. The oil contains about 64 percent polyunsaturated, 30 percent monounsaturated, and 6 percent saturated fatty acids. Importantly, camelina oil is very high in alpha-linolenic acid (ALA), an omega-3 fatty acid which is essential in human and animal diets and has important implications for human health. The oil also contains high levels of gamma-tocopherol (vitamin E) which confers a reasonable shelf life without the need for special storage conditions.
In comparison to canola (rapeseed) which produces some 127 gal/acre camelina is reported to produce in the 62 to 100 gal/acre range.

Field trials of production showed a wide range of results from 330 to 1700 lbs of seed per acre, with oil content varying between 29 and 40%. There are however a significant number of varieties of the plant and thus tests have been carried out to determine which might yield the better crop given the Montana growing conditions. Optimal seeding rates seem to be in the 6-8 lb/ acre range, because the small size of the seed (400,000 seeds per lb.) apparently make it more difficult to ensure germination and achieve an optimal plant density of around 9 plants/sq. ft. It does apparently grow better when the ground nutrients are supplemented with nitrogen up to levels of 80 lb/acre.

The Montana report ends with the following
At this point there are many more questions than answers when it comes to camelina production and use. Early experience in Montana has shown that with good management, and timely planting, good crop yields can be attained. As a broadleaf cool season crop, camelina could become a good complementary crop to wheat, providing a needed break from cereals in wheat production. Crop rotation is a great way to reduce disease and insect pressure for any crop, and there are few good economic crop rotation options for wheat in Montana. Weed control is a major limitation to camelina production. Currently there are no herbicides registered for use with this crop, which means rescuing a field that becomes infested with weeds is difficult.
However varieties of the plant produces its own herbicide.

Data on crop production is still somewhat limited since the USDA did not start data collection until 2007, and the 2008 report was issued this April. Production in Montana in 2008 was significantly down (at 12,200 acres) over that of 2007. The average yield was 569 lb/acre, down 4.8% over 2007, though the range from 400 to 1000 lb/acre makes it unlikely that any conclusion can be drawn from those numbers.

The Welsh report comments on the current extraction process
Camelina typically contains approximately 35% oil. Cold pressing is not 100% efficient, the proportion of oil extracted being dependant on the type of seed and how well the press is set up.

As an example, a tonne (1000 kg) of Camelina will contain 350 kg of oil, of which the press will extract 250 kg. Cold pressing (400C) is required, because high temperatures will damage the antioxidants. Drought, lack of sunshine during seed formation, herbicide desiccation applied too early, and downy mildew infection may all lower the oil content of the seed.
In Wales they can get up to 1 t/acre.

Oregon is considering growing the crop after looking at trials in nearby states
Under dryland conditons in Montana, camelina is expected to yield 1,800 to 2,000 pounds of seed per acre in areas with 16 to 18 in hes of rainfall and 900 to 1,700 lb/acre with 13 to 15 inches of rainfall. Under irrigation, seed yields of 2,400 lb/acre have been reported. Three years of yield trials at Moscow, Idaho show a 2,100 to 2,400 lb/acre seed yield potential with 25 inches of rainfall.
. At present there are restrictions on the growing of canola in Oregon
Oregon officials in 2005 restricted canola-for-oil production in the valley to protect the valley's high-value vegetable seed crops. Officials recently announced they are going to renew the prohibitions.

"I would like to grow canola, but the state interferes with that, too," Van Leeuwen said.

Fears are canola will attract insect pests common to canola and brassica crops and that canola will cross pollinate with cauliflower and broccoli, lowering seed purity and eventually driving vegetable seed contractors out of the valley.
Camelina may overcome some of those concerns.

So my quick look suggests that it about on a par with canola (rapeseed) with some survival benefits over that plant as a crop, that it is only just being introduced into the United States as a crop and that, while it has potential, and there are some productive strains identified, it is still a little early in the game to know if it will pan out quite as well as the Biofuels Digest suggests.

Read more!

Tuesday, August 25, 2009

Promising signs and a gentle cough toward Michael Lynch (again)

Another monthly Traffic Volume Trends this time for June, is now out and confirms the uptick in driving that I have been noting for the past three months is continuing and beginning to gain a little momentum.

The trend is now consistent across all regions, with the West up 2.5%; North Central up 1.6%; North-East up 0.8%; South Gulf up 2.8%; and South Atlantic up 1.8%. When the 12-month rolling total is plotted, the trend is now definitely upwards.

June 2009 12-month rolling total of miles travelled (FHWA)

The report breaks the miles travelled down into rural and urban sectors, and while the rural number has been above last year for a couple of months, it is only this month that the urban miles has also risen above last year.

June 2009 Travel on US Urban Highways by month (FHWA)

This is, again, a somewhat encouraging sign that the economy is in a state of turn around, although, apropos my post yesterday, the big question of what happens when not only the U.S. but all the other countries, including Western Europe also begin to pick up steam and look to additional fuel supplies may be answered more rapidly than had at first been feared. (Although the result of finding out may not be pleasant either).
UPDATE: I changed the plot below of US gasoline demand to the new plot that TWIP published today.

A quick look over at the TWIP shows that gasoline demand has really not changed much – if any, relative to last year, but the volume demand would have to increase quite a bit for that number to detectably change on the plot (the numbers show we are still around 300,000 bd short of last years demand at this time). (Number went up 100,000 bd relative to last week with the new data).

U.S. gasoline demand though August 22, 2009 (TWIP)

As I mentioned last week I expect that OPEC will be able to cope with the increase in demand next year, but will start to strain at the demand in 2011, and have difficulty meeting it towards the end of that year and into 2012.

Now that is not what you will hear from the cornucopians and Michael Lynch had an editorial in the NYT excoriating those of us who doubt.
A careful examination of the facts shows that most arguments about peak oil are based on anecdotal information, vague references and ignorance of how the oil industry goes about finding fields and extracting petroleum.
His main target at the moment happens to be Fatih Birol, the Chief Economist at the International Energy Agency (IEA) whose predictions I wrote about with concern at the beginning of the month. The particular one of concern is that the decline rate that has been reported for older oilfields is now at 6.7%, rather than the 4.5% which has been historically assumed and which models for future supply have been based on. Over a year ago Sam Fourcher in The Oil Drum showed in two graphs (one at the top of the post and the more worrying one, hidden in comments what a difference a change from 4.5% to 5.2% had on the time at which global production would peak (it moved it forward in time about 3 years) and in the steepness of the resulting decline. Now (and Fatih Birol is by no means the first to report these higher numbers) declining production is shown to be 1.5% worse that the second graph assumes. This is not “anecdotal information, or a vague reference.”

Unfortunately when the facts don’t support his argument our good cornucopian carefully changes his topic so that he can tar those of us concerned about the future supply of oil with a set of arguments that he can shoot down, vide:
for the most part the peak-oil crowd rests its case on three major claims: that the world is discovering only one barrel for every three or four produced; that political instability in oil-producing countries puts us at an unprecedented risk of having the spigots turned off; and that we have already used half of the two trillion barrels of oil that the earth contained.

Actually, at the moment none of my immediate concerns and the subjects of recent posts include any of those points. Yes there is a longer concern about the state of reserves – The graphs that are assembled from the Megaprojects database come from the predicted times of planned projects coming on-stream. These are projects that are of significant size, and thus take time to bring to fruition and, at that scale, receive significant coverage in the technical press (Rigzone and the Oil & Gas Journal spring immediately to mind as sources I look at every week among more than a dozen others).

Declining production from different countries (such as the UK and Mexico – as I pointed out yesterday) is a matter of public record, and the amounts that are disappearing from the world stage are not trivial. And when, as I reported yesterday, the major Russian oilfield at Samotlor now finds itself are producing at 90% plus water cut this significantly impacts production (pumps can only physically move certain volumes at a time and if most of it is water you can’t speed up your pump much to increase the oil flow for simple fluid mechanics reasons– a point that seems to be lost on our cornucopian.)

Yes the world continues to find oil in new fields, but they are not as easy to find and develop and they don’t last as long as the old giants. In Russia successive oilfields moved further East as the original fields wore out, and they have now reached as far East as Sakhalin Island.

Sequence of Major Russian oil discoveries and developments (after Grace shown on a Google Earth map )

So, according to Michael Lynch, we should anticipate that if they go North and East of Sakhalin Island they will make their next discoveries and we can all relax.

Oops! There is only one slight flaw in the argument – you see that new area is known as Alaska – Russia sold it some years ago, and I believe that somebody else has already been there and got that oil!

Read more!

Monday, August 24, 2009

The Changing oil supply perspective - opening lecture class note changes

It’s the start of a new Semester, and at the beginning of my Power class I spend the first lecture reviewing where I think we stand on the Energy supply to the United States. This has changed a bit since last year and so I thought I would run through some of the changes that I made to my lecture this year, in the same way as I did on TOD last September. Since the greatest impact is likely to come from the changing sources of supply that the US has had to go to, with the change in levels of production, I began with this slide:

Sources of Oil imported to the US in May 2009 (EIA)

It is interesting to see the relative amounts from Mexico, Saudi Arabia and Russia and the first thing to note is the decline in Mexican supply, brought about by the dramatic drop in production from Cantarell. (H/t Nate Hagens).

The peak and decline of Cantarell – where Mexico got most of its oil.

That drop has already shown up as a decline in Mexican exports to the US of over 800,000 bd. At this point I introduce them to the Export Land Model (ELM) of Jeffrey Brown, which basically points out that after a nation’s economy has grown (and oil consumption with it) during the high production years, then as oil production declines (as above) it is the export market which suffers more, as the country retains more of its product for its own use.

Export Land Model (ELM) of Jeffrey Brown, showing the more rapid decline of exports, as production falls in a country, yet internal demand continues to rise.

While Mexico is the most dramatic example of this at the moment, it is important to consider Russia next. We used not to get much oil from Russia, but as the table above shows, that situation is changing. (Russia to the Rescue was the theme of a made for TV movie Oil Storm back in June of 2005, where they sent us a couple of oil tankers which “saved the day”. At the time $75 a barrel for crude and $4 per gallon for gas was considered to only happen if the US was damaged by a hurricane and the Saudi terminal at Ras Tanura was attacked.) Well now they are sending more and regularly, but the question relative to the ELM is how long can they keep this up.

Exports from Russia dropped 5.2% in 2008, but have crept up some 0.2% since January, with Russia exporting about half its production. The big question about that, however, is that a pipeline is going in at the moment that will start shipping 300,000 bd of oil from Russia to China and to Japan. Given that overall Russian production is expected to decline (one of their major fields at Samotlor is now producing at 750,000 bd, when at peak it produced 3.2 mbd, and now that it is 80% depleted the water cut is 90%.)

A well at Samotlor (TNK-BP )

So with increased amounts of internal consumption (it is using about 2.8 mbd internally it is becoming another example of the ELM.

Russian production, consumption and exports (note that according to Rosstat Russia is now exporting around 5 mbd) (from the EIA)

With both these countries exports declining, the question is becoming who will be the next to step in and provide additional oil for us. Saudi Arabia has dropped production to 8 mbd to keep the price up, and there are some questions about the future production – and I refer to the pictures from Satellite over the Desert that I have used before to question Saudi long term production ability. I also note that Saudi Arabia is now consuming 2.2 mbd of oil and demand is rising. There is, for example, this
Estimates on how much crude it is burning differ, but the kingdom's own data show it has risen in recent years, and it could be as high as 470,000 bpd of crude this year, up 62 percent from 2008, consultancy FACTS Global Energy says.

A Saudi source familiar with the kingdom's energy sector said the maximum it could burn at power stations would be 300,000 bpd, although another 120,000 bpd could be burned to power refineries and other facilities related to upstream production
Aramco claim to have the capability of producing 12 mbd of oil, but again I remind the class that this includes the oil from Manifa, which cannot be produced until it can be refined and that won’t be until 2013 at the earliest.

And thus one comes to Canada, and so there is the quote from the Wicks Report that the Alberta oil sands will provide half of North America’s imports. The level of those imports is shown in the first table, and the oil sands are not now predicted to get to 2.7 mbd until somewhere around 2018, up from the current 1.3 mbd. So with the oil sands being the increasingly major supplier of oil to Canada as the conventional reservoirs deplete, it does not look as though Mr Wicks Report will prove realistic, and we will need to look elsewhere to make up supply shortages for ourselves.

At which point it is timely to point out that the UK will be competing with us for the remaining world supplies of oil, and that China and India, with their burgeoning car sales, will also be adding an mbd or so to their demands for oil next year.

The one bright hope that I end the oil section of the lecture with is that, with ethanol production at around 750,000 bd there is a new candidate supplier of jet fuel. The Japanese airliner that tested fuel this past winter used Camelina as the source for the jet fuel. It seems to have more going for it than corn or cellulosic based ethanol, at this point in the evaluation.

It is nice to end the section on an optimistic note, and the message from the above is that there are going to be jobs for the students when they graduate, and it will likely remain so for the length of their careers.

Read more!

Sunday, August 23, 2009

Casing a well

There has been some concern (that among other things has led to the actions in the House to bring hydrofracing fluid under the Safe Drinking Water Act) about the use of different fluids in oil and gas wells and the risk that they can get into and contaminate surface ground waters that may be used as drinking water. So I thought that I would write a little about well casing today.

Not that well casing is the only thing in the local environment that has to be protected or designed for. Because the odds are that where you want to drill does not sit right next to a highway. That means that you are going to have to install some sort of a road to get to where you want to put the drill. That may sound fairly straightforward in somewhere like Texas, (though it got some folks upset in Wyoming), but it becomes a lot more complicated if your oil patch is in the middle of the North Slope of Alaska, or the Empty Quarter in Saudi Arabia.

In the North Slope, for example, they make the roads out to the sites out of ice. Because the ice must carry the weight of the units that haul the rig into place, the road has to be of a certain thickness, and it has to be at a certain level of coldness to give it strength, (which means winter which is also dark). This means that they can only move rigs at certain times of the year and that restricts the rate at which they can develop new fields and wells. As a result the season is only about four months long, I believe (though have not been up there at that time of year to check).

Having got to the site then it has to be prepared, among other things we need to have a way of getting the cuttings that come out of the hole separated from the drilling mud, and then having a place to put both them, and to store the mud until it can be drawn back into the pumps and circulated back into the hole. And we need to create an initial hole, or cellar, where we can start the drilling pipe into the ground. I will cover all the different things that go into the surface layout in another post, let’s for now concentrate on that hole, that is going to head down for up to several miles in order to get to the oil or gas.

This initial part of the well has to be fairly large, for reasons explained below. Let us begin the well with a fairly large sized drill bit, say 9-7/8 inches in diameter. So we thread this into the drill collar, lower it to the rock surface and start to rotate the string. As the bit advances we can monitor the rock that it drilling through by looking at the cuttings that come out of the hole. We have some idea of what rocks are down there from the surveys that convinced us to drill here in the first place, but it helps to have this confirmed. Plus we need to know if there are any unpleasant surprises down at the sharp end. As the hole gets deeper the time for these cuttings to reach the surface, and be cleaned and examined, the lag for return, gets longer, and so it gets a bit trickier to know what is happening at the bottom of the well.

This can lead to short-term problems. Bear in mind that the hole is being drilled as an open hole. In other words, once the drill goes beyond the conductor pipe, it is drilling in rock, with only the rock walls on either side of the well holding it open. This can be a problem in drilling through weak or jointed rock, since bits can fall into the hole behind the bit, and if enough of those fall they can jam the bit in place (since they fall on the bit above the cutting surfaces).

As the bit goes deeper we add additional lengths of drilling pipe to form the drill string, and the bit penetrates through rocks that are of different types and some of these will have fluid in them. Water, whether fresh, which might be the supply for a local community, or salt, is quite common. The hole cannot be left open any longer, because the water flowing from the surrounding rock into the well will dilute the mud, so that it no longer works as it was supposed to, plus, we might start losing some of the drilling fluid into the surrounding rock. Plus different layers of non-drinkable water can work back up the well into the drinking water aquifer.

To stop this from happening we have to stop drilling and seal off the rock on the sides of the well from the well itself. This is known as casing the well, and running casing will hopefully (but not always) be only needed once before we get to the bottom of the well.

So we pull all the drill string out of the hole, remove the drill and lower steel pipe into the well to encase the well, from the bottom of the conductor pipe down to where the bit has found (and hopefully drilled through) the rock that is giving us the problem. (Hence the name casing). Having this continuous length of casing in the hole will likely stop, say water, from getting in and diluting the drilling mud, but if this was all that we did, then it would still leave a problem, since the steel pipe does not completely fit up against the rock wall created by the drilling bit. In other words there will be a gap between the casing and the rock wall, that will allow fluids to travel up or down. This gap has to be filled, and the filler is normally a special form of cement.

The way that the cement is placed is simple in principle, but a fair bit more difficult to do properly and effectively. Think of the long thin tube of casing, filled with a cement that acts something like toothpaste. This cement has to be pushed down the tube so that it squeezes out of the bottom and then flows back up between the casing and the rock wall, filling all the gaps as it is pushed back up to the top or surface. (Hence the name surface casing). Particularly when this casing is run, it is important that the gap is fully filled. This is because this is the casing that seals the well from local groundwater, used for domestic and industrial supply. Since the cement will move more easily thorough a larger passage, than a very narrow one, this gap has to be above a certain minimum size. Small centralizers will be attached at points down the steel casing to keep it in the middle of the hole, rather than pressing up against one of the walls (since this might leave an open channel up through the cement). There are also “scratchers” which are put on the casing so that when it is rotated in place it will scratch the walls of the borehole and remove any mud cake that might have formed, so as to give a better bond between the cement and the rock wall.

Cementing plugs

A small plastic plug (the bottom plug) is put into the casing ahead of the cement. This separates it from the mud that is already in the hole. It is fitted with wipers, that clean mud from the walls of the casing, and it is pushed down to the bottom of the casing by the cement that is pumped into the well behind it. There are some pictures of some of the tools and descriptions of the process here, here and here.

Once the bottom plug gets to the end of the casing, there are ports it passes that allow the cement to flow out of the casing and back up the outside. Once the cement has been pumped into the casing a second, top plug, also fitted with wipers, is put into the casing and this is then pushed down by the conventional drilling mud. As it is pumped down it forces the plug down, and the cement out and back up to the surface. Because of possible variations in hole size and other possible problems, perhaps about 50% more cement might be pumped into the well than the calculations might suggest. When the top plug hits the bottom plug, then there is a pressure spike at the pumping station, telling the operator that it is finished. The rig then waits on cement (WOC) until the cement is hardened. The drill pipe can then be put back in the hole and drilling can restart.

Illustration of a cased well

But whoops, the bit won't fit in the hole any longer! For the sake of discussion lets say we ran half-inch thick casing. And that we had an inch of cement behind it all around the casing. Then the hole we have available to get the drill through down to the bottom is now only 6-7/8th inches in diameter. So we now might use a 6-5/8th inch diameter bit to continue drilling (since we don't want it rubbing against the casing wall).

If we run into another layer of problem rock as we drill down to the bottom of the hole, then we are going to have to run another set of casing. This is known as intermediate casing, and the process is the same, and it leaves us with an even smaller hole through which to get a drill bit through.

So that, when you get toward the bottom of the well you may end up drilling with a bit that is only 3-3/4 inches in diameter. These drill with a smaller thrust than the larger bits, and so, although you may have a very powerful drilling platform, with thousands of horsepower available, you may end up, as you approach the pay zone where the oil is, using only a fraction of that power.

We'll discuss what happens when you hit oil next time, but perhaps by now you might begin to understand why, in drilling a well that might cost $1.25 million, the actual drilling part alone may be no more than a third of the cost.

As usual I welcome comments, questions or criticism. But to catch the obvious one - yes, after running casing, the first thing you have to drill through are the two plugs and the remaining cement in the bottom of the well, before you can reach and start drilling through the rock again.


Read more!

Saturday, August 22, 2009

The Nile, The Guardian and disaster without climate change

There are times when the corruption of the press by the mantra of “climate change” becomes a little more obvious than usual. So it is with the piece that appeared in the Guardian last Friday concerning the coming disaster to Egypt from the changes going on in the Nile Delta. To condense the story into a nutshell, it deals with the declining prospects of the Delta - the main agricultural resource for Egypt - both as it is currently evolving and looking forward from that into the future. You can see the influence of the Nile, and the Delta, (the green bits) in this overview shot of Northern Egypt (mostly the brown bits) from Google Earth.

Nile Delta and Egypt from Google Earth

The story begins with the story of the farmer Maged Shamdy, and his perceived fate.
"We are going underwater," the 34-year-old says simply. "It's like an occupation: the rising sea will conquer our lands."

Maged understands better than most the menace of coastal erosion, which is steadily ingesting the edge of Egypt in some places at an astonishing rate of almost 100m a year. Just a few miles from his home lies Lake Burrulus itself, where Nile flower spreads all the way out to trees on the horizon. Those trunks used to be on land; now they stand knee-deep in water.

Maged's imperial imagery may sound overblown, but travel around Egypt's vast, overcrowded Delta region and you hear the same terms used time and again to describe the impact climate change is having on these ancient lands.

The only problem is that the rest of the story documents how it is everything but climate change that is causing the problem – which doesn’t of course stop the author of the piece, Jack Shenker, from making the claim. So let me, as I did for the Bangladesh Delta, explain, with the aid of the odd peer-reviewed journal article, what is causing the problem – it isn't climate change - but in a word or four it comes down to overpopulation and the Aswan High Dam.

Let’s start by explaining how a delta system works –whether in Egypt, Bangladesh or Louisianna. The delta lies at the seaward end of a long river that picks up eroded soil carried into it from its feeding and surrounding tributaries, or eaten away from upstream by its own passage. Seasonally the river floods over the delta, and in so doing, as the water slows, it deposits soil on the surface of the delta. You can actually see effects of previous climate change by the changing nature of these sediments. In the case of the Nile, the floods come about following heavy rains in the Ethiopian highlands and Sudanese basin typically in July. August and September. Lands could be flooded to a depth of up to 5 ft, and would be inundated for about a month and a half. In that time the sediment in the water would settle out as silt, the water would flush out any residual salts in the soil, and would prepare the soil for the subsequent planting of crops. This process has provided fertility and water to the Delta for thousands of years. On average the rains in the headwaters of the Nile removed around 0.2 mm/yr of soil and this was deposited in the Delta to an average thickness of around 1 mm/year. Interestingly across the Mediterranean at Venice, Day et al showed that this type sedimentation is anticipated to provide enough land build-up over the next 100 years to mitigate even the sea rise anticipated by the IPCC at some sites.

However, as the article notes, in 1970 the High Dam at Aswan was built, and this captures all the Nile sediment (between 40 and 132 million tons a year) which is now filling Lake Nasser behind it. Although, with the Lake being some 300 ft thick, and 500 miles long, it may take a long time to do so. But now that fertile material is denied the Delta.

So that is the first part of the problem. The second part is that the sediment of a delta will normally compact over time, forcing water out of the lower members, and thus gradually lowering the top of the overlying surface. Where the land is regularly flooded that sinking is matched by the new soil that floods over it, but it is now about 40 years since the soil stopped flooding over the land, and the amount of soil missing is becoming significant. Hence, as the quote above notes, the gradual sinking of the trees into the water of the lake.

The lowered land levels also make the land more vulnerable to sea erosion. Smith and Kader showed that this can be tied to the reduction in sedimentation.
Although coastal erosion is a serious problem along the Egyptian Mediterranean Coast, it is localized at specific areas. These areas have undergone slow to moderate erosion since the turn of this century as a result of natural decrease of the River Nile flow and as a result of increased number of structures across the Nile. In a post High Dame phase, these areas eroded at accelerated rates (3-5 times the rates before the Dam).

Lake Nasser from Google Earth – at the other end of Egypt (the yellow line is the border) The High Dam is at B, and this used to be Nubia.

And to get back to the original article for the remaining problems
Today, however, Nile water barely reaches this corner of the Delta. Population growth has sapped its energy upstream, and what "freshwater" does make it downriver is increasingly awash with toxins and other impurities. Farmers such as Maged now essentially rely on waste water – a mix of agricultural drainage and sewage – from the nearby town of Sidi Salim.

The result is plummeting fertility; local farmers say that whereas their fathers spent just a handful of Egyptian pounds on chemicals to keep the harvests bountiful, they now have to put aside between 25 and 80% of their profits for fertilisers just to keep their crops alive.
As the article itself notes the increased population is taking the water that used to irrigate the lower parts of the Delta. This has nothing to do with climate change (except in that the milder conditions of a Warming Period has historically led to population surges) But that doesn’t stop the charge being made.
Experts believe the problem is only going to get worse. "We currently have a major water deficit in Egypt, with only 700 cubic metres of freshwater per person," explains Professor Salah Soliman of Alexandria University. "That's already short of the 1,000 cubic metres per person the UN believes is the minimum needed for water security. Now, with the population increase, it will drop to 450 cubic metres per person – and this is all before we take into account the impact of climate change."

Much before any problem that might be related to climate change shows up, Egypt has a much larger problem, which is the root cause of the above, and which the article points out
With Egypt's present-day population of 83 million set to increase to more than 110 million in the next two decades, the seemingly unstoppable spread of bricks and mortar over the soil is both the most visible symptom of the country's demographic time-bomb and an inevitable response to it.
Perhaps that should, more logically, be addressed first?

Ah, well, enough said.

Read more!

Tuesday, August 18, 2009

Can Saudi Arabia and OPEC meet future demand

Looking forward to a return to more normal times for the global economy (something perhaps allowed by the improved health of some countries in Europe, and some stability in the U. S. housing market and increases in the miles driven in the United States) leads to a small wonder about what we will find when we get there. Doing some simple projection on Asian demand growth, non-OPEC declines and a rebounding economy suggests that we might only have a year's breathing space before we're back in trouble.

At the present OPEC is predicting that world demand for its crude will be at around 1.65 mbd below last years demand for the rest of this year and is anticipating that demand will fall another 0.5 mbd to 28 mbd next year. However that assumption is apparently also based on non-OPEC production will increase, and the world economy will rise only slowly. There is some evidence to suggest that change may be a bit more dramatic.

Of course in recognizing the above number OPEC has also recognized that they have actually been quietly increasing production and that is already back to some 28.57 mbd, with further increases predicted. Back in January the cuts were supposed to be 4.2 mbd, were actually only about 2.62 mbd down from the 31.2 mbd of last year. The odd thing is looking at those numbers and taking the 2.62 from the 31.2 gives 28.58 mbd, which is reported as the current figure. Yet after the initial cut there has been a slow relaxation in enforcement that has seen some production gains to date. The answer is that not everyone did the relaxing. Saudi Arabia increased the level of their cuts to match the increased production elsewhere, for example cutting production 320,000 bd in April down to a level of 8.04 mbd, though it has since crept back up to 8.11 mbd. Using the EIA tables indicates that total OPEC production may, in fact, already have reached 30.31 mbd, which is only down 900,000 bd from last year.

The reason that I bring this up is that the Chinese and Indian economies are continuing to sell cars. China has now reached and surpassed US car sales. VW sold 128,000 cars in China in July. To fuel those cars Chinese demand for oil has increased to 7.8 mbd, with the prediction for next year being that it will rise an additional 0.6 mbd to 8.4 mbd. Chinese demand in 2008 was 6.92 mbd.

Indian demand will also rise, since car sales have also been steadily rising over the last six months, with the introduction of cars such as the Tata Nano that started off selling 100,000 cars a month. (Total car sales in India last year were about 1.4 million – sales this July were 115,067 up from 87,901 last July). Indian consumption has increased so far this year by about 320,000 bd. Now if that trend continues through next year then the combination of Chinese and Indian demand alone will raise demand by close to 1 mbd.

If non-OPEC production has peaked and is falling, as we see from reports from Mexico, which may drop 300,000 bd over the next year; Russia which will slightly drop: and the UK, then we might assume at best that the production drops 500,000 bd next year in total.

So if non-OPEC goes down 500,000 bd and global demand goes up 1 mbd from India and China (not to mention the increase in demand as the rest of the world starts to come out of recession) then OPEC will have to raise production by at least 1.5 mbd next year just to meet this change in the supply:demand balance.

With the cuts that Saudi and friends made that amount is likely available and could be relatively easily produced if desired. If the supply is controlled, as it now is, to ensure that we don’t get back into a slight oversupply, this means that OPEC will control the price over the next year, but that the supply will be adequate.

What becomes interesting is what happens after next year. If Asian demand continues to rise by say another 1 mbd, the world, coming out of recession also increases demand back by say 1 or 2 mbd, where does it all come from? Because declining oil fields will continue to do so, and we may well see another drop of 500,000 bd from non-OPEC.

This is thus going to be an imposition of another 2.5 – 3.5 mbd demand on OPEC, over the 1.5 mbd demand increase for 2010. Bearing in mind the 6.5% decline in production reported from older fields as more and more of them contain horizontal wells in significant proportion, I don’t think they will be able to do it. Which means that 2011 and 2012 could turn out to be very interesting years indeed.

Read more!

Sunday, August 16, 2009

Of Scrubbers, Bag Houses and Flue Gas Cleanup

The problem that Governments face is that, while they can take political and idealistic stances about issues, when the chips start to fall they are in charge of governing. Which means that, regardless of idealism, they have to recognize the reality of (among other things) providing energy to their nation. Thus, while we see a considerable public posture by the British Government over Climate Change, they are moving ahead with plans for increased coal mining activity. In the short term the industry is to be awarded permission to mine an additional 15 million tons, and production is rising by 15% from surface mines (opencast) as imports also go up. (In the UK surface mining now accounts for more coal than does underground production). Some 54 new mines have been approved in the past four years. It is a recognition that idealism or not, power must be provided.

Carbon capture and sequestration is still perhaps ten years away from large scale application, but the flue gases produced from the combustion of the coal are already being cleaned of some of their content gases, and I thought that I would talk today about scrubber technology and what is currently done to flue gases before they are released.

While I will describe how a modern power plant works in another post, suffice it to say for now that coal is used to heat water to steam, and that steam then turns turbines that spin generators, that produce electricity. After the coal is burned, the combustion gases are released to the atmosphere and are referred to as flue gases. But, because of the chemicals and particles that are left in these gases, they are first cleaned or “scrubbed” to remove some of the noxious ones. The most infamous of these is sulfur dioxide (SO2) which, if released into the air can combine with water vapor in the air to form sulphuric acid. The vast majority of the sulfur dioxide in the air comes from electricity generation and at historic levels, the acid that was produced and precipitated as a rain which could not only cause damage to surfaces it fell on, but also posed a health hazard. Hydrogen chloride might also be formed, and some of the nitrous oxides that are emitted also combine with water to form nitric acid, and commonly the combination is referred to as acid rain. To prevent it, it is easier to remove the acid forming gases at the power stations before they are released.

U.S. Sulfur dioxide emission levels in 2002 (EPA)

Formation of acid rain (EPA)

So how do we capture a gas that is coming out of a tall chimney? Simple answer is at the bottom, before it goes up the chimney. In a more complex answer the gas is fed into a chamber where either hydrated lime is sprayed as a fine particulate into the flue gas (known as dry injection) or the limestone/lime is sprayed through nozzles in a slurry form (the wet scrubbing). Efficiency of removal of the sulfur dioxide is in the 95 to 99% range. Wet scrubbing is the most widely practiced of the two with limestone being the preferred absorbent over lime. (Mainly because of cost).

Simplified scrubber schematic (Source Penn State)

The result is a wet mixture of calcium sulphate and calcium sulphite (the heat of the flue gas is supposed to dry the particles in some designs). In the process the reaction also releases carbon dioxide.

SO2 + CaCO3 = CaSO3 + CO2

Or, where the remaining air in the flue gas is supplemented

SO2 + CaCO3 + 1/2O2 + 2H2O = CaSO4.2H2O + CO2

With the gypsum being a saleable product into either wallboard manufacture, cement making or agricultural products. The solid must be removed from any residual liquid (often using hydrocyclones) and then is ready for processing. The process can also pick up some of the mercury in the flue gas, and in that case the circuit may be modified to strip that from the waste water.

Waste water treatment at the Merrimack Power Plant (Siemens)

In an alternative version of scrubber technology, the Chinese have used salt water, rather than lime or limestone, as the scrubbing agent. In the schematic of the process the dust collector is the bag house and the Absorbers are the scrubbers:

Schematic of the cleaning circuit at the Mawan Power Plant

Mawan Seawater Scrubber Power Plant Layout

But at the same time the power plant will also capture the fine particles of ash left over from the combustion and some of the lime particles may get picked up in the cleaned flue gas and they need to be captured before the gas is released to the atmosphere.

The fine residue from the furnace is called fly ash, and because of its small but regular size and some of its chemical properties it has some commercial value (when mixed into cement it can significantly improve it, for example). Thus up to 45% of the fly ash that is collected can be used in this and other ways, and the EPA is hoping that up to 50% will find a use in the next couple of years, since that which has no use must be land-filled.

Because the fly ash is small in size (5 – 100 micron ) and hot (about 140 deg C) as it comes out of the boiler it is trapped as the gas passes through fine filter bags of a special weave that collect this residue, and at intervals the filters are shaken, loosening the ash, which drops into hoppers and can be collected and removed. This operation takes place in what is known as a bag house. On rare occasions bag houses can catch fire, if all procedures aren’t followed properly. The filter weave must, obviously be smaller than the particles if it is to trap them.

Typical baghouse construction

Rules for flue gas emissions are being tightened, and as a result emission levels continue to fall
Sulfur dioxide emissions were down 24 percent compared to the first half of 2008, much more than would be expected due to the recession and lower electricity demand, the power industry data provider said in its quarterly review of energy trends.

"The industry is clearly going through a dress rehearsal for the implementation of the Clean Air Interstate Rule (CAIR) in 2010, and judging by allowance prices as well as the fundamental data, it is a stellar performance," Genscape said.
The change in rules requires scrubbers in plants where there was no need before, since the rule caps emissions of SO2
But the decline in SO2 is largely because of the new rules coming in 2010 and an allowance scheme that favors early implementation, the power data provider said.

"Most of the decline in sulfur emissions is not due to the recession or even to the switch from high-sulfur coal to lower sulfur grades and to gas," Genscape said, noting many plants have installed equipment to remove SO2 from emissions.

"It makes sense to start cutting emissions early if the equipment is in place since pre-CAIR vintage allowances will retain their full face value of a ton of SO2, while from 2010 onward, each permit will be worth only half a ton," Genscape said.

Well this is fairly brief review of what a scrubber and baghouse are and what they do when attached to a Power Station. As with all Tech Talks I have had to simplify and condense things, perhaps a little more than is clear. In which case please ether comment if you know more, or ask if something is not clear.

Read more!