Pressure transient analysis of naturally fractured reservoirs: a case study

The characteristic pressure behavior of naturally fractured reservoir systems has been extensively researched in petroleum engineering literature. In a naturally fractured system, reservoir fluids exist in two interconnected systems, the matrix system which provides the bulk of the reservoir volume, and the fracture network which provides the conductive pathway for transmitting fluids to the producing wells. If the flow between adjacent matrix blocks and fluid transport from the matrix blocks to the wellbore is only through the fracture network, then the system is considered dual-porosity. When there is possibility of fluid flow directly between the neighboring matrix blocks and to the well through the matrix in the unfractured region, the system is considered to be dual-permeability. However, the pressure responses from actual field data display similar characteristics for both dual-porosity and dual-permeability reservoirs. Field data that display the classical dual permeability behavior are not very common in the petroleum literature. This paper presents some field pressure transient tests from a naturally fractured Saudi Arabian reservoir that display the classical dual-permeability characteristics and the analyses performed on them.