Optimization of Stimulation Design Through the Use of In-Situ Stress Determination

Voegele, M.D., Abou-Sayed, A.S., and Jones, A.H.
Presented at Paper JPT 10308 in the SPE Journal of Petroleum Technology, 1071, 1983.


The role of in-situ stresses in controlling hydraulic-fracture geometry and extent has been widely recognized. This paper describes the results and applications of several research programs carried out over the past few years to optimize the design of hydraulic-fracture stimulation treatments using information pertaining to in-situ stress action within the reservoir. Begun as fracture-mechanics-based theoretical studies of propagation and containment of hydraulically induced fractures, these programs have grown into full-scale field demonstrations of the deduced principles. A review is provided of field-measured in-situ stresses in the pay and confining formations. The existence of in-situ stress contrast between the pay zone and the bounding layers has been demonstrated in these field demonstrations. Furthermore, the results also showed the significant role of the in-situ contrasts in fracture containment. Unfortunately, however, great variability in the stress contrast from site to site has been observed. The field programs have been performed in both openhole and cased wells. Laboratory studies of hydraulically fractured large block samples have been carried out. Cubic samples up to 3.3 ft per side were subjected to triaxial stresses as high as 2,175 psi. The results of these tests have been used to support the field efforts. The programs described in this paper indicate that successful stimulation design requires a knowledge of the in-situ stress field and contrasts within relatively narrow ranges at well depth where the stimulation treatment is performed. A general knowledge of the approximate regional stress fields and gradients is not a sufficient data base for design. Stimulation designs must be adapted to the in-situ stress contrasts to obtain deeply penetrating fractures. To minimize the costs of in-situ stress determinations on a well-by-well basis, a wireline-operated hydraulic-fracturing tool has been designed. The tool does not require a rig on the well; and because it is entirely self-contained, considerable cost savings will be possible compared with the costs of standard techniques of stress determination by hydraulic fracturing.