Modelling and optimization of multiple fracturing along horizontal wellbores in tight gas reservoirs

The pre-calculation is required for planning and optimization of multiple fracture systems to enhance oil and gas recovery from tight reservoirs. However the fractures in a multiple-fracture system are often individually treated in the conventional semi-analytical simulators, such that the influence between individual fractures is completely neglected. By contrast the 3D FDM-Program FLAC3D is able to simulate multiple-fractures more realistically. With the newly developed method in FLAC3D the fracture orientation and type are not anymore assumed, which is mainly the difference with the one in phase I. For the optimization of a multiple fracture system the distance between the single fracture and the borehole direction plays the most important role in fracture design. Generally transverse multiple fractures are better than the longitudinal ones, because they are little influenced by the neighboring fractures. In case of longitudinal multiple fractures it is recommended that the boreholes should not be drilled exactly in the direction of maximal horizontal stress, sigma(H)