Mexia, Texas — In an east Texas cow pasture recently, scientists and engineers tried something of an energy experiment. It didn't involve solar power, synthetic fuels, biomass, or any of the other evolving energy sources -- just good, old-fashioned natural gas.
Mitchell Energy & Development Corporation pumped a foam mixture of nitrogen, water, and sand into an old well to fracture the underground formation so it would release more natural gas. The use of foam is a recent development in fracturing technology.
The Mitchell Energy project illustrates the risks involved with emerging enhanced-recovery techniques. The plan was to pump more than a million pounds of sand, mixed in a foam solution, into the well. Then the solution was extracted from the well after the underground formation was fractured, leaving the sand to keep the fracture propped open and allowing an increased flow of natural gas.
The cost of the one-day project was estimated at $500,000. The increase in natural gas production from the well as a result of the fracture was expected to be from 50,000 cubic feet a day to 2.5 million cubic feet a day. That would have allowed the project to pay for itself in about 40 days.
However, a mechanical failure forced the project to shut down early, well before the full amount of sand had been injected.
Now the company is unsure how much production will increase, since the magnitude of the fracture was reduced.
Still, there is no loss of enthusiasm for the technology, and Mitchell Energy plans additional foam fractures for other wells in the area.
The project demonstrates a generally accepted notion in the American energy industry: New techniques for "enhanced recovery" of oil and natural gas from difficult geologic formations and older wells with flagging production could unlock vast new supplies of these most traditional forms of energy.
Consider: There is almost three times as much oil left in the ground in the United States as has been produced since the early 1900s. Industry knows where the oil is, but has not been able to exploit it. Crude and recoverable US natural gas reserves of 200 trillion cubic feet are effectively doubled when gas from "tight sand" formations, which has been for the most part uneconomical to produce, is included. The amount of gas contained in Eastern Devonian shale rock, also largely unexploited, is on the order of 880 trillion cubic feet, the US Department of Energy estimates.
The high cost of exploiting these reserves, which for a variety of reasons are more difficult to produce than conventional oil and gas, has kept them trapped in the earth. But higher energy prices, in general, and certain incentives tailored to these hard-to-get fuels have made them more attractive. The wind-fall-profits tax measure being considered by Congress gives favorable treatment to oil recovered through enhanced technology, and gas from tight sand formations was recently granted a 50 percent higher price than conventional natural gas by the federal Energy Regulatory Commission.
J. Hugh Liedtke, chairman of the Pennzoil Company, which is very active in producing oil from old fields in Pennsylvania, said in a recent Monitor interview that it will be five years before enhanced oil recovery adds significantly to the nations's energy supplies. After that, though, it will become a substantial energy source, he predicts.
Although the economics of enhanced recovery has improved in the last few years, Mr. Liedtke said there is still considerable risk in using a new technology.
"There are enormous front-end capital costs with [enhanced] recovery. Then you just have to sit back and wait to see the results," he said.
In oil wells, the most common methods for stimulating more production employ the injection of chemicals or carbon dioxide. These help restore pressure in a well and loosen more oil for production.
The US Department of Energy has estimated that enhanced-recovery techniques could ultimately add 25 billion to 40 billion barrels of oil to US supplies, roughly doubling the current crude reserves. The US produces an estimated 300, 000 barrels of oil daily through enhanced recovery, out of a total domestic output of 5.5 million barrels a day.