Coalbed methane is playing an increasingly important role in meeting the energy needs of the United States. According to one estimate, this unconventional gas may supply 4-5% of the domestic natural gas in 1994. In the San Juan Basin, Fruitland Formation coal beds contain an estimated 43 to 49 trillion cubic feet (Tcf) of methane. This basin is the most active area of coalbed methane development and production in the United States.
Low recovery efficiencies of sandstone reservoirs in the Jackson-Yegua Barrier/ Strandplain Sandstone play mark it as a large hydrocarbon resource target for advanced recovery techniques. Prado field, Jim Hogg County, South Texas, has produced more than 23 million barrels of oil and more than 32 billion cubic feet of gas from structural-stratigraphic traps in barrier/strandplain sandstones of the Eocene lower Jackson Group. Recovery efficiency is 34 percent from the primary oil reservoir and 72 percent from the primary gas reservoir.
An active diapir forcefully intrudes its overburden, driven by diapir pressure that overcomes the resistance of the overburden strength. Possible causes of the driving pressure are differential loading of the source layer and a density contrast with the overburden. Resisting forces derive from the mass of the roof block and resistance to the faulting and folding that accommodate the intrusion.
ow-permeability ("tight") reservoir sandstones of the lower Missourian Cleveland formation produced more than 435 billion cubic feet (Bcf) of natural gas through December 1990, mostly from Ochiltree and Lipscomb Counties in the northeastern Texas Panhandle. Although large-scale gas production started in1956, the regional stratigraphic, depositional, and structural setting of the Cleveland is poorly known.
