Prediction of minimum principal in-situ stress by comparison and verification of four methods

摘要

This paper evaluates the correlation between values of minimum principal in-situ stress derived from four different models which use data obtained from triaxial core tests or sonic logs. The first method utlilizes a normalized form of the Mohr failure envelope equationfit different lithologies. The second method utilizes sonic log data to predict Posisson's ratio which is used to calculate the minimum principal in-situ stres. The third method uses a fit to the Mohr failure envelope as a function of average rock grain size, which was obtained from detailed microscopic analyses. The fourth method uses the Mohr-Coulomb failure criterion which uses an average angle of internal friction to predict the minimum principal in situ stress. The minimum principal in situ stress values obtained from the four different methods are then compared to actual field mini-frac test data which is known to be the most accurate method to determine the minimum principal in situ stress. The cores and the mini-frac stress tests were obtained from two wells, the Gas Research Institute's (GRI's) Staged Field Experiment (SFE) #1 well through the Travis Peak Formation in the East Texas Basin, and the Department of Energy's (DOE's) Multiwell Experiment (MWX) well located west-southwest of the town of Rifle, Colorado, near the Rulison gas field.