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Oriented Drilled Sidewall Cores for Natural Fracture Evaluation

1999; Linguagem: Inglês

10.2118/56801-ms

Stephen E. Laubach, ELOISE DOHERTY,

Seismic Imaging and Inversion Techniques

Abstract A procedure to orient drilled sidewall cores and to evaluate large natural fractures using microfracture indicators was successfully tested in three gas wells in Silurian Medina Group, Appalachian basin. Microfractures from these cores document the strike of fractures that control production. By running well bore image logs after coring, sidewall core holes can be detected and core azimuth determined. The main challenge to orienting the 1-inch-diameter cores is determining "up" direction, because sedimentary facing indicators are rarely visible, and currently deployed sidewall coring devices do not mark (scribe) cores. To find core tops we used fracture surface marks induced on core ends during recovery and examined image logs. Success rate for this core-orientation procedure is remarkably high, in these examples close to 85 percent. This shows that cost-effective sidewall core orientation is feasible. Oriented core, along with useful indicator microfractures, is a practical source of information on the attributes of large fractures.