Abstract

In order to fully understand the performance of waterflooding in Spraberry Trend Area reservoirs, large scale reservoir simulation using a dual-porosity simulator is necessary. The most important input data required by the simulator is the directional fracture permeability and the anisotropy of the reservoir permeability.

This paper reports a new method for estimating directional fracture permeabilities from pressure data recorded during single-well tests. In this study, a new, dual-porosity, dual-permeability, mathematical model has been developed for single phase flow in reservoirs that are naturally, vertically fractured. Fracture spacing is explicitly considered in the model. The model consistently fits a set of single-well-test data obtained from a Spraberry well before and after hydraulic fracturing. The on-trend and off-trend fracture permeabilities before hydraulic treatment have been estimated to be kx = 30 md and ky = 0.09 md, respectively. The anisotropy of the fracture permeability is kx / ky = 322. The on-trend and off-trend fracture permeabilities after treatment have been estimated to be kx = 39 md and ky = 0.9 md, respectively. The anisotropy of the fracture permeability is kx / ky = 43. These results indicate that the hydraulic fracturing treatment significantly improved (10 fold) fracture permeability in the off-trend direction.

This paper provides reservoir engineers with a useful tool for estimating fracture permeability anisotropy and other properties of naturally fractured reservoirs from single-well tests.

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