Study On Fluid Flow Mechanism Of Low-permeability Reservoirs With Segregated Fracturing Horizontal Wells

Segregated fracturing horizontal well is one of the most effective technologies to develop low permeability petroleum reservoirs. Physical and numerical simulations were both used to study segregated fracturing horizontal well flow mechanism of low permeability reservoir. Natural outcrop sandstone rocks were used in physical simulations. A novel physical simulation method was finally established in this paper in which the large low permeability rock models can be used. Non-linear flow simulation software independently developed by our research group was used in numerical simulations. Optimal fracture parameters and fluid flow mechanism in segregated fracturing horizontal well were thoroughly studied. The main research results are summarized as follows:1. Selection and evaluation methods of large-scale rock models were established in this research. Three important petrophysical parameters were included in the new selection method. They were rock pore throat, clay minerals and non-linear flow parameter. Consequently, the outcrop rock models selected by the new method not only have the same petrophysical properties with the subsurface reservoir rock, but also have the analogous fluid flow mechanism.2. Well-pattern combined with horizontal and vertical wells were simulated with plat models. Depletion and water flooding experiment were conducted to study fluid flow mechanism and production characteristics. Factors influencing effective driving such as fracture length, displacement pressure and well type were studied. Based on pressure-gradient field, effective pressure coefficient was proposed to evaluate effective driving. Research indicates that larger displacement pressure and longer fractures are preferred to effectively drain the reservoirs.3. Numerical geologic model was set up to study the production characteristics of horizontal well pattern. Depletion and water flooding development simulation were conducted aiming at reservoirs with different permeability. Research shows that more segments, longer fractures and higher conductivity were preferred for lower-permeability reservoirs. Parameters were optimized and development plan were raised.4. Fracture distribution was studied with numerical simulation method to evaluate its impact on effective driving. Study shows that cross-distribution fracture can better drain the reservoir.