The Transformation of Hydrofracked Reservoirs to Thermal Energy Production

Organic rich low permeability formations in many locations throughout North America contain significant volumes of natural gas, but not until the early 1990s was it deemed practical to extract this gas resource in economic quantities. Hydrofracturing, pioneered by Mitchell Energy Company on the Barnett Shale in East Texas demonstrated the technical feasibility of developing these tight formations along with horizontal drilling techniques that resulted in high-volume yields from wells that previously did not flow at rates sufficient to recover the initial investment of drilling. Development of these tight formations using hydrofracturing and horizontal drilling has transformed the North American natural gas industry, and has added, by some estimates, at least another 200 years of reserves at the present rate of natural gas consumption. Individual wells, however, in most circumstances, do not have an extended economic lifetime as yields from these fracture-stimulated wells generally decline quickly and new wells must be drilled and fractured. The substantial investment in well design, installation and reservoir stimulation should not be abandon, however, as many of these wells can be converted into thermal mining wells, yielding geothermal energy on a sustainable basis for as long as the well casing and well integrity can be maintained. Parametric analysis of typical wells indicates that each well cluster contains and can yield from ten million to eighty million barrels of oil equivalent in extractable thermal energy, and there are several thousand promising candidate wells for this procedure. As important as is demonstrating the extractable thermal energy from these wells is that these thermal yields are renewable over reasonable time frames making the potential energy production from these wells in geothermal energy many times greater than the BTU content of the natural gas originally produced from the wells.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California