Influence of Discrete Fracture Network Geometry on Well Test Behavior

Well tests are a fundamental characterization tool for oil and gas reservoirs and for groundwater investigations. Several common geometric models exist within conventional well testing practice. These models are based on porous continua. In particular, two dimensional radial flow has been used as an indicator of porous medium flow. On the other hand the infinite conductivity hydraulic fracture model of Gringarten, which has a one-dimensional flow geometry (all flowlines parallel), has been used as an indicator of fracture flow. The main point of this paper is that the geometric models of well tests are not unique to fractured or porous media. Discrete fracture network models are useful to show that well test responses associated with porous media can also be produced in discrete fracture networks. Two dimensional flow behavior may be produced by a space filling fracture network in a layered system. One-dimensional flow is easily produced where there is a strong single fracture set orientation, and three-dimensional flow can be developed from a layered system with out of plane faults.