A 3D Finite Element Model for History Matching Hydraulic Fracturing in Unconsolidated Sands Formation

摘要

Field hydraulic fracturing tests data provide valuable information regarding the mechanical and hydraulic behaviours of the reservoir formation. By history matching the field bottom-hole pressure vs. time curve from hydraulic fracturing tests, a set of field-calibrated geomechanical models can be obtained, which is an important asset for any further works on utilizing geomechanics to enhance the injection and production performance. This paper presents a 3D finite element model for history matching the complete bottomhole pressure vs. time curve generated during hydraulic fracturing tests, considering the injection rate as input. To simulate the hydraulic fracturing process in unconsolidated sands formation, a poro-elasto-plastic constitutive model, together with a strain-induced anisotropic full permeability model, are formulated and implemented into a 3D finite element geomechanical simulator. Unlike the conventional simulation of hydraulic fracturing in hard rock, hydraulic fracturing in an unconsolidated sands reservoir is simulated as a large area of shear dilated plastic zone, inside of which the effective stresses are low and hydraulic conductivities are high. It is shown that the proposed numerical model can capture the hydraulic fracture initiation and propagation in unconsolidated sands formation and matches the field pressure vs. time curve.