Photo: Marc Durand
Here is a text reproduced with the permission of the author, Marc Durand, doct-ing geologist
Retired Professor, dept. Earth sciences, UQAM
"Following the publication on the canvas of my text" Gas Shale - a few reflections of a geologist "I received many comments, including the issue of Claude Pare:
J would love that Mr. Durand clarify two points. I know he has knowledge of the concrete. - What he said is the life of a well as built by the industry. If faults occur in these wells, they can become conduits for liquids and gases. - The water and salt water fracturing buried in the basement they can weaken the concrete. "
I have not read all the submissions to the BAPE, but those that I read there in which no one is asking or dealing with your question, I would rephrase this: "What is the lifespan of a well - including its effectiveness in time to serve as a" cap "on the drilling to the end of time ... and what happens when the underground portion of the well loses its effectiveness due to corrosion and other damage? " 
There must be a deadline; it is longer for books inspected and maintained and shorter for temporary structures and all the engineers know this basic fact, eg the estimate to stabilize and cover the roof of a subway tunnel is not the same as for a temporary gallery in a mine. In the case of the subway, there was no choice but to build very strong and durable, in addition to adding a program of inspection and maintenance for the duration of use. We saw recently with the viaducts and bridges end-of-life and preferably before, they should demolish and rebuild nine. It should not take any chances of seeing a work beyond the end of life of its structure. Some bridges with proper maintenance will last for centuries, others poorly suited for the use and exposure conditions have an end of life after half a century only. For a temporary building or a structure in which man has no access, safety and life are designed with much lower construction criteria.
Everything we know about shale gas wells is that these are books whose design is optimized for a very short life: the years of operating the wells. After one mouth (the term is more descriptive:
cementing), they bury the top of the structure and the site is revegetates (memory QOGA). There is virtually nothing published to respond to the questioning of Mr. Pare, the life of the underground structure. Yet the question is
importantly, because for 20 000 wells that will one day end of life, and that will just "masked" before being donated to the local geography, it will cost how much per year in 20 or 30 years? It's total silence on this issue, because any time in the mining and petroleum, which happens to drilling has never been a concern. The industry has never planned to spend a dollar for it, the most recent legislation in the world does not create obligations for site remediation at the end of the operation. It requires companies to provide for the rehabilitation of the surface sites, but almost nothing for what is buried. Drilling
who arrived at the end of life, which have become dangerous, especially since we had forgotten their location, having just been hidden in the landscape surface, there are thousands. In the U.S. it is reported more and more victims
explosion due to gas back through these old wells. In most cases, these former exploration drilling (Appalachian Mountains, Colorado) from the beginning of last century. The problem will take an entirely different magnitude in the near future, with the end of life of gas wells in strata that have been extensively modified by the technique of hydraulic fracturing. Newly applied technology will allow large-scale abandonment of thousands of
drilling in populated areas, without offering anything about the impacts that will arise at the end of life works.
specify what we mean by the end of life of gas wells and shale. The book as pit has a life of 3 to 5 years. It is a device optimized to extract gas as quickly and cost effectively. The flow that delivers the newly fractured shale is very high at first, then decreases in a logarithmic or exponential. We abandon the well at a rate deemed not profitable at this stage about 20% of the gas is picked up. In conventional gas reservoirs, up to 95% of natural gas can be recovered "In the case of shale, we expect a recovery rate of 20% due to the low permeability and despite the high horizontal drilling density and extensive use of hydraulic fracturing "National Office of Energy, The ABCs of shale gas (
http://www.neb.gc.ca/clf nsi/rnrgynfmtn/nrgyrprt/ntrlgs/prmrndrstndngshlgs2009/prmrndrstndngshlgs2009
-eng.pdf)
At the end of this period is converted briefly the pit into another type of structure, whose sole function of stopping the gas flow into the well. By shutters, plugging cements the tubing, etc.. we must transform a temporary structure extraction permanent structure for a very different function. In reality, almost nothing changes in the structure and composition of the well except the addition of a permanent cap. Whatever the design of the cap, the new book, the well-call-blocking, can have a life drastically changed. Yet these caps will withstand the pressure of life at which methane will continue to pull away from the fractured shale. Let us not forget that 80% of the gas remains in the shale at the end of extraction.
Under the plain inhabited the Utica will become a highly permeable reservoir, still containing the remains of methane after skimming (20%). This enormous volume, 100 m thick x 10000 Km2 be connected directly to the surface by 20 000 wells in slow corrosion of the steel casing and grout sealing in the presence of a highly saline environment will deteriorate. This can be done at varying speeds from one well to another, depending on the quality of development drilling, casing and grout, etc.. The life of each of these wells is the time before the degradation is such that major leaks forced the authorities to intervene. Obviously from there it will cost. This cost may appear very early in the process to some wells, as seen in Quebec on wells for which the operation not even begun, but at this moment is the responsibility of the industry that owns the well. It shows that leakage does exist, even on a brand new wells.
Figure 1 summarizes the various ways that gas may follow to reach the groundwater surface and drinking water wells (p). The light blue letters (A, B, C) show the circulation in a case where drilling intersects a fault or fracture of great extension. This case may happen in a proportion of wells that is difficult to estimate because the detailed geological mapping is not really available in the overburden in the Lowlands St. Lawrence.
Figure 1: The various possible leaks to a pit - a well-plugging. Once there
presence of such a discontinuity, the injected liquid penetrates and opens the way far away (A) in the strata of Lorraine. Traffic is therefore constantly open to continue in the lenses of sandstone and other more permeable layers. Gas leaks will occur in artesian wells and homes that are located near the fault. Note that the fracturing fluid also opens much farther than expected discontinuity in the underlying limestone strata (A '). The Trenton is more permeable than the shale and contains high salinity waters. A path is also open for salt contamination. Some analysis indicates that well water already this type of problem has probably already been encountered in wells. Between the casing and the drilled rock, and between the production tubing and casing protection, quality of implementation of the grout can be left empty ring fractures may also be formed during the intensive use of the well . This is a possible origin of gas leaks that occur in the same wells (E and K).
In addition to these opportunities leaks, there will be at the end of the wells, probably between two and five decades after the end of operations, more widespread leaks that will occur gradually, and a growing population of abandoned wells. The primary causes are: 1 - the degradation of steel and cement patching 2 - gas pressure that will certainly slow, but surely do more and more pressure on these works-caps 3 - rebalancing of pressure (more precisely, stress state) in the fractured rock will slowly readjust, shearing or deforming locally sections of tubing. Strata in the Utica tend to inflate the air free; the same property at depth will tend to flow and to close some time with open fractures. The mass will thus move towards a decrease in its permeability, but it will not be enough to bring it back to its original impermeability. These micro-breaks will instead contribute to release yet more methane over time.
We are dealing with structures that will deteriorate in the midst of extreme salinity, deep in the bedrock of any possibility of inspection and maintenance in an environment transformed by hydraulic fracturing operations. The circulation of fluids, saline water and methane will be affected. All structures between the surface transformed Utica will sooner or later reach a level of advanced decomposition. The wells will reach a state where they function as puitsbouchants no longer operational. What does that mean in plain language: the mega problems in each of these wells, means of mitigation to implement, complex studies to be undertaken to try to find a solution,
BAPE commission for each site? see my analysis of the case of Mercier in my previous text. There will be many of the 20 000, perhaps between 250 and 500 new cases per decade in a generation. Billions to be budgeted in Quebec.
If we kept in perpetuity wellheads accessible rather than restore the sites we already have a less complex task, because you could listen and see the catastrophe coming, but no one offers this anywhere. It says it will "restore the site at the end of extraction. In fact it just means to bury the problem and forget about it until we broke out in the face. Finding a solution to this problem at this point will be an impossible task, while
as it is impossible to erase a well. The hole remains there, even if we try to plug up with something else, something that will never intact shale properties were drilled and fractured. The Utica shale gas has kept for more than 400 million years. All our present and future technical never able to do as well.
Figure 2: Business plan including a diagram of the life of the wells.
Figure 2 above shows the income and expenditure for Quebec as a global entity, that is to say the entire community. The business plan of the gas industry stops with steps 1 and 2, it takes end with cessation of operations and the time required to restore the land surface. During the first phase (exploration), the community receives annual revenues by paying modest exploration permits, eg: 10 ¢ / acre + $ 100/puits drilled. Quebec has cons cost analysis, monitoring, displacement of inspectors, etc.. This is certainly a negative balance at this stage for the community. During the operations, monitoring expenses and others continue, but they are largely offset by the payment of royalties on gas extracted. At the end of operation, gas companies, stop paying royalties. They may also cease to pay the cost of mining rights, which they have interest in; full ownership of the gas field returns to the government. The chart shows that the lifespan of structures-mouth remains unknown, but the question of whether there is life: it is yes without hesitation. In the current business plan, if you look at the lessons of the past, the community will bear the costs that will inevitably occur at some time or another.
Wells-mouth does not go get all the same length life. For a small number, the deterioration will occur soon enough, the bulk of the squad later and a last batch could miraculously show no sign
for generations. Overall costs may appear early, with a curve was increasing constantly, especially about the time that corresponds to the average lifespan of structures (Figure 2).
Whatever the parameters, the business plan of Quebec Gas Inc, is to tell us the community in this case, an operation will be strongly negative. Only one winner: the gas companies that we have had a Christmas tree And is the official name of the wellhead (Christmas tree) and it is no accident: it is a sign of destiny that tells us to turn on the lights for which there is still time ... "
Marc Durand , doct-ing geologist
Retired Professor
dept. Earth sciences, UQAM
Shefford, February 2011
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