THE USE OF STRESS TRAJECTORY IN PREDICTING FRACTURE PROPAGATION PATH AROUND INJECTOR AND PRODUCER WELLS

Abstract

It is well documented both in the field and in laboratory experiments that hydraulic fracture could deviate from its original plane of propagation, typically parallel to the direction of the maximum principal stress, due to varying stress and pore pressure conditions. It has also been observed that due to possible stress reversal around a previously fractured well, refracturing a well may lead to new fractures, orthogonal to the original fracture.

This work considered two problems. First, the possible path of propagation of a fracture in the neighborhood of unfractured fluid injector-producer pair using the stress trajectory concept was re-examined. A fracture initially equidistant between the wells was shown to likely propagate in the direction of the injection well as indicated by the maximum principal stress trajectories around the fracture-well system, provided a particular dimensionless fracture toughness is small. Additional parameters such as the far field stress deviator and the production/injection times were shown to have significant impact on the stress field perturbation. A modified stress trajectory equation that incorporate fracture toughness effect in order to approximate the fracture propagation direction was also introduced.

The second problem examined the stress reorientation around an unpropped fractured producer. The extent of the orthogonal segment of the refracture half-length as a function of production time and far-field stress deviator for a purely poroelastic case as well as the relevant parameters influencing the extent of stress reversal around the fractured well was examined. Adequate knowledge of the stress field will be quite helpful in future re-development of existing fields with fractured wells.