Seismic technology pinpoints fracture pathways in tight reservoirs

LARGE volumes of natural gas are being tapped from the tight rocks of the San Juan Basin in Rio Arriba County, New Mexico using a new technology developed by the US Department of Energy (DOE).

In this cost-shared project sponsored by DOE, GeoSpectrum Inc, of Midland, Texas, is using 3D seismic in four new wells to locate fractures that allow access to millions of cubic feet of untapped natural gas.

One of these wells is now producing up to 2 million cubic feet per day, according to DOE National Energy Technology Laboratory geophysicist Francis Toro.

"The key innovation in this project is the integration of technologies that map previously unseen fracture lineaments and perturbations in seismic data, and then target 'sweet spots' where multiple fractures intersect," Toro said.

The Energy Department awarded the contract in 1999 to spearhead the development of technologies and methods to locate known resources of natural gas contained in naturally fractured tight reservoirs.

The US is estimated to have about 460 trillion cubic feet of natural gas — almost three times the amount of the country's existing gas reserves — in these low-permeability reservoirs.

The key to producing this vast resource is to pinpoint and drill areas where natural fractures form pathways for gas flow .

By drilling in those locations, greater supplies of natural gas can be accessed and recovered.

To find these natural fractures, GeoSpectrum, along with Burlington Resources and Huntington Energy, have applied an innovative technology that combines seismic analysis, petrophysical analysis, and analysis of existing wells to identify potential fracture sweet spots, where gas is concentrated and able to flow to a well bore.

The DOE claims this project shows that the technology can locate natural fractures in gas-bearing formations while reducing the risks associated with drilling in tight reservoirs. The ultimate benefit will be the location and recovery of vast new energy sources to meet increasing needs for clean-burning natural gas.