Journal of Canadian Petroleum Technology, Vol.49, No.6, 53-67, 2010
New Method of Well Test Analysis in Naturally Fractured Reservoirs Based on Elliptical Flow
Up-to-date well test analysis in naturally fractured reservoirs is based on the radial flow model. The radial flow model is only applicable to purely homogeneous systems and is a long-term solution in general. It cannot provide complete formation analysis in reservoirs that exhibit anisotropy. This study, therefore, presents a new method of estimating permeability anisotropy in naturally fractured reservoirs. Maximum and minimum permeability are obtained from a single well test. The maximum permeability is attributed to the large-scale fractures in the system, while the minimum permeability may be caused by the small-scale fractures orthogonal to the large-scale fractures. In a situation where the fractures are oriented in one direction, the minimum permeability will reflect the matrix permeability. The type of flow path developed (narrow or wide flow path) can also be predicted. This is useful in predicting the direction of fluid-flow. Application was made to four field examples, among which was an interference test. The interference test was used as a validation process. The results obtained are in agreement with that of the interference test method of analysis.