Geomechanical Factors Affecting the Hydraulic Fracturing Performance in a Geomechanically Complex, Tectonically Active Area in Colombia

摘要

The Cusiana and Cupiagua fields are located in a tectonically active, geologically complex and highly faulted region in the Colombia foothills. These features lead to unusual complex hydraulic fracturing performances which can not be taken into account by conventional models and practices. To reduce risks and associated costs related to unsuccessful hydraulic fractures, it is imperative to identify the primary factors and mechanisms affecting the hydraulic fracturing performance in this geomechanically complex environment. In this study, the main factors affecting the hydraulic fracturing performance in geomechanically complex oil and gas fields have been investigated. To achieve this objective, it was necessary to compile, interpret and process of a wide set of data relevant to hydraulic fracturing performance from previous successful and unsuccessful hydraulic fractures from several fields and formations. Geomechanics models were constructed for each well and the actual performance for each hydraulic fracture was simulated to study the effect of the following factors: initial failure type (shear or tensile), wellbore orientation, stress anisotropy, stress continuity with depth, near-well faults, natural fractures, rock strength, geomechanical properties, pore pressure and stress path. This paper refers to the first four factors (initial failure type, wellbore orientation, stress anisotropy and stress continuity with depth). The remaining factors will be subject of a future publication. Results show that the factors having the strongest effect on fracturing performance are initial failure type and well orientation, which are highly correlated. In past successful hydraulic fracturing operations, tensile failure occurred prior to shear failure. Conversely, unsuccessful hydraulic fracturing operations are associated with shear failure having occurred prior to tensile failure. Thus, it is imperative to select well orientation and fractured interval such that tensile failure is guaranteed to occur prior to shear failure to assure a successful fracture. Additional observations show that stress continuity with depth and stress anisotropy favors fracture performance. Application of the new findings and best practices obtained from this study has led to improve the hydraulic fractures geomechanics performance in Cusiana and Cupiagua fields.