What We Are Learning From Shale Drilling – Earth Sciences
Analysis by S. Tom Bond, Retired Chemistry Professor and Resident Farmer, Lewis County, WV
Geologists and petroleum engineers are learning that the earth is really much more complicated than the simple conceptual diagrams that are in their textbooks and that they put out to the companies that want to drill. Those diagrams are a bit like a layer cake. They appear to have uniform thickness and consist of uniform, homogenous, single component layers.
However, buried landscapes, compression and extension, lateral thrusts, percolating waters of various compositions, often highly corrosive or oxidizing, radioactivity, an immense amount of detail which changes unpredictably in a few yards vertically or a few tens of yards horizontally are left out.
They have to be, because every location is different. Fracking gives an opportunity to find details which don’t appear in published diagrams. Things like abandoned wells, cracks large enough for migration at depth, variations in the thickness and quality of the target rock. Terry Engelder is quoted here as saying certain joints in the source rocks may “break out of the gas shales and populate the rock above these gas shales. [This] joint set may appear about 1000 feet above or even as much as 4000 feet above the gas shales.” The industry vigorously denies this. The economic value of shale varies tremendously within a few miles. Nobody (almost) says anything about this.
Chesapeake Energy began selling investments with the assumption all drilling locations were more or less identical, and the wells would provide economic amounts of gas for 30 or 40 years, like conventional wells. This has not proven true.
Something petroleum geologists and petroleum engineers are learning that they did not suspect is the rapid decline in production and the spottiness of production within a field. Look up graphs of decline rates for various shale fields here.
Much more information for a sample of the Marcellus is printed here, but the graphs are harder to read. Each diamond shape indicates a well’s production decline as of June 30, 2013. The months it has been in production is along the horizontal axis and the percent decline is a long the vertical axis. For example, the extreme right upper diamond represents a well in production for 48 months (just a little left of the 50 months line) and it has lost 79% of its production in that time. Another, the diamond shape lowest in the left has lost 58% of its production in 12 months time. The beauty of this reference is that the information reported to Pennsylvania DEP (which by law is open to the public) is printed along with the graphs. No argument can be made with this!
If you read much about shale drilling, you are already aware of the rapid decline in production of shale wells, compared to drilling in conventional reservoirs. James Stafford quotes Arthur Berman: “… nobody thinks very much about is the decline rates shale reservoirs. Well, I’ve looked at this. The decline rates are incredibly high. In the Eagleford shale, which is supposed to be the mother of all shale oil plays, the annual decline rate is higher than 42%. They’re going to have to drill hundreds, almost [thousands of] wells in the Eagleford shale, every year, to keep production flat. Just for one play, we’re talking about $10 or $12 billion a year just to replace supply.” What this means is illustrated in an article about the Barnette in The Oil Drum. Instead of drilling wells and being able to sit back and relax and count on initial production to hold up for years at nearly the initial level, tens of billions of additional investment will be required to maintain initial levels.
Another big thing discovered is what happens when pressures of thousands of pounds per square inch are applied to liquids pumped down disposal wells in volumes equal to several houses day after day, with only cracks and pores the size of a grain of sand in them to receive it. Rumble, rumble! It takes about 4.0 on the Richter Scale to cause damage, but one in South Texas got up to 4.8. The Richter is a logarithmic scale so 4.8 is 6.3 times the magnitude of 4.0. Definitely connected with the well, as many small quakes have between verified to be connected to disposal wells.
Cliff Frohlich, speaking at WVU, recently identified one of 5.7. He thinks injection wells shouldn’t be sited in cities, but out in the country is OK. (The “country hicks” don’t care if they are injured or their property is destroyed? The insurance companies will compensate them for their losses?) Earthquakes don’t happen at all disposal wells, but when one considers the facts above, then one has to wonder just where these toxic waste liquids do go and how long they will stay put.
Frohlich has the life expectancy of the Marcellus field down to less than 30 years (to 2040). That’s assuming future wells do as well as the present wells, no doubt, in spite of the fact drillers avidly seek out the “sweet spots” and highest returns first. And, assuming the investors are willing to cough up money to drill and drill and drill.
Then there will be all those wells to plug. Any body willing to say this generation of drillers will be more responsible about plugging their wells than those in the past? What do you suppose it takes to plug a well that takes 3 to 8 million to drill? Don’t you think that expense will be left for the public, just as wells and mines worked in the past must be remediated by government money, our taxes, or not at all?
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