Semi-analytical model of the transient pressure behavior of complex fracture networks in tight oil reservoirs

- Based on Ozkan's plane source function, a semi-analytical model was established to analyze the transient pressure behavior of horizontal well with complex fracture network.
- The process of fluid flow in tight oil reservoir with complex fracture network can be divided into five flow regimes: linear flow, fractures interference flow, first radial flow, cross flow and pseudo-radial flow.
- The flux distribution in multi-stage hydraulic fractures, orthogonal fracture network and un-orthogonal fracture network has several common characteristics.

Unconventional resources have been successfully exploited with technological advancements in horizontal drilling and multi-stage hydraulic fracturing, especially in North America. Due to pre-existing natural fractures and the presence of stress isotropy, several complex fracture networks can be generated during fracturing operations in unconventional reservoirs.Based on Ozkan's plane source function, by virtue of equivalent conversion and coordinate transformation, a new plane source function was derived that can handle the fluid flow behavior in an inclined fracture in dual media, anisotropic, tight oil reservoir. Using the superimposing method, a semi-analytical model was established to analyze the transient pressure behavior of horizontal wells with complex fracture networks. Using this method, we defined five flow regimes: Linear flow, fractures interference flow, first radial flow, cross flow andpseudo-radial flow. The influences of some of the critical parameters on the transient pressure behavior were studied, including the fracture number, distribution of the fractures, storage ratio, and so on.This paper provides a useful tool for reservoir engineers regarding fracture design as well as for estimating the performance of horizontal wells with complex fracture networks.