Predicting the Hydraulically Created Fractures in the Cotton Valley Formation of East Texas

Abstract

The tight gas sandstones of the Cotton Valley Formation of East Texas require massive hydraulic fracture treatments to achieve economic rates of production. Engineering data indicate a well will efficiently drain a maximum of 160 acres. Optimization of well spacing will require a knowledge of induced fracture orientation. At the present time there is not reliable method where by this orientation can be measured. Oriented caliper data obtained from dipmeter logs run in fifty wells were used to investigate the borehole geometry through the Cotton Valley sandstones. it was found that quite often the sandstones when drilled through would "spall" or "wash-out" and that the borehole would be elliptical in shape with the major axis always oriented in a NW/SE direction. The opinion of the authors is that the consistency in orientation is due to in-situ stresses within the rock, and a prediction can be made that hydraulically induced fractures in the Cotton Valley sandstones of East Texas will be oriented in a NW/SE direction.

Comparison of Hydraulic-Fracture Orientation Techniques

“…Consequently, we have also investigated the accuracy and reliability of using stress relief,6 thermal expansion, and sonic velocity measurements on oriented sandstone cores. The predictive technique of borehole elongation 7,8 was also investigated, but these results are not presented in this paper. These predictive techniques have been investigated in several fields in east and west Texas and in Alaska.…”