Horizontal Exploitation of the Upper Cretaceous Austin Chalk of South Texas

BORKOWSKI, RICK, Oryx Energy, Dallas, TX

Horizontal drilling in the fractured Austin Chalk of south Texas has proven to be a viable technology for exploiting reserve opportunities in mature trends as well as frontier areas. Success to date has been the result of an interdisciplinary approach to the regional analysis of structure and stress regimes combined with studies of the depositional characteristics of the Austin Chalk and Eagleford Shale. Productive characteristics of the Austin Chalk indicate the influence of regional fractures on the preferential flow direction and partitioning in the Pearsall field area of the trend.

Well-bore orientation and inclination are designed such that multiple fracture swarms at several stratigraphic layers are intersected with a single horizontal well bore. This in turn leads to a significant increase in in the ultimate recovery of hydrocarbons in place as a result of the greater frequency of fracture contacts with the well bore. Conventional vertical drilling techniques frequently are ineffective at encountering these laterally partitioned fracture sets, resulting in lower volumes of recoverable hydrocarbons. Additionally, horizontal well bores may increase ultimate recovery of hydrocarbons by lowering the pressure gradient to the well bore and maximizing the reservoir energy.

AAPG Search and Discovery Article #91011©1991 AAPG Southwest Section Meeting, Abilene, Texas, February 9-12, 1991 (2009)