In-Situ Stress State Eastern Cordillera (Colombia)

Abstract

Abstract Knowledge of the regional state of in situ stress direction and magnitude is required to delineate stress provinces, to analyze intra plate earthquakes, to optimize petroleum recovery and for the development of civil projects in rock masses. This paper on rock mechanics and reservoir geomechanics studies the stress state including the pore pressure that operates in the rock mass and the mechanical behavior of the rock, to create an integrated model to study the in situ state of stress in the Eastern Cordillera, Colombia. Several measurement techniques were used, which include strain-relief overcoring, hydraulic fracturing techniques, shear fractures in the walls of the boreholes knows as breakouts, leak off test and induced drilling tensile fracture in the walls of the boreholes. Rock mechanics properties are required for the application of these methods and laboratory tests were carried out to find elastic constants. The orientation of the maximum horizontal principal stress σHmax is parallel to that of tensile failures (tensile wall fractures) and perpendicular to that of compressive failures (breakouts). The magnitude of the minimum principal horizontal stress σhmin is determined from leak off tests (LOT) and hydraulic fracturing, while the magnitude of the vertical stress σV is simply calculated based on the density data collected in several representative wells in the Cusiana field. From recent tectonics results are clear that the region in the Eastern Cordillera is characterized by an active strike-slip / thrust faulting regimen. The actual regional state of stress found means that the minimum principal stress σhmin (0.65 psi/ft to 0.77 psi/ft) oriented in a NE-SW direction, is less than the vertical stress (1.07 psi/ft), and the maximum principal stress σHmax (1.2 psi/ft to 1.7 psi/ft) in NW-SE compressional direction is significantly greater than the vertical stress, which therefore is the intermediate principal stress.