Hydraulic-mechanical analysis of induced stress change in unconventional reservoirs using a novel fundamental solution of poromechanics in a half space

The production of fractured unconventional reservoirs induces stress changes, which will affect the production performance of neighboring wells. To quantify such effects, the analytical solution is a convenient yet accurate tool. In this work, we have developed an analytical solution of the transient pressure and stress variation induced by the production of a point/line/plane source in a semi-infinite poroelastic reservoir with a traction-free surface boundary. We have benchmarked the derived solution with both analytical solution and numerical program. The solution demonstrates excellent accuracy. Moreover, the analytical approach reduces the computational time of numerical approaches from hours to seconds. We then apply the solution to study the surface subsidence control and stress interference between fractured horizontal wells. Results show that the derived solution is capable of quantifying complex hydraulic-mechanical processes during the recovery of shallow water as well as deep shale reservoirs. Upon investigation, we have found that infill wells can effectively reduce the surface subsidence induced by the production of shallow horizontal wells. Furthermore, shale reservoirs with lower permeability are more sensitive to pressure-stress changes. The range of stress reorientation can also be efficiently quantified by the developed approach. Also, normal stresses and shear stresses behave differently during fracture driven interactions. The above findings potentially benefit the decision-making in the asset development. The major novelty of our work lies in the extension of existing approaches that are limited to axisymmetric problems to line and plane sources problems, so that the solution can be used in unconventional reservoirs with fractures.