Effects of Fracture Fluid Invasion on Cleanup Behavior and Pressure Buildup Analysis

Abstract

Abstract A hydraulic fracture treatment is the most common method used to stimulate the gas flow rate of a well completed in a low permeability gas reservoir. Hydraulic fracturing is accomplished by pumping a proppant laden fluid into the formation at high injection rates.' Once the minimum principle stress in the formation is overcome, a fracture is induced and begins to grow. The vertical fracture will continue to grow until pumping is stopped. After the fracture treatment, fracture fluid will leak off and imbibe into the formation around the fracture as the fracture closes. After the fracture has closed, the well will be placed on production in order to clean up the fracture fluid around the fracture and begin producing gas. Prior to performing a hydraulic fracture treatment, a complete reservoir description should be developed by the engineer and geologist. The reservoir description should include properties such as formation permeability, porosity, net pay, reservoir pressure, skin factor, and other information needed to properly describe oil and gas flow from the reservoir.2,3 In addition, the mechanical properties of the formation layers above and below the productive zone should be evaluated. The mechanical properties are needed to compute the estimated shape and dimensions of the hydraulic fracture that will be created. After the reservoir description has been completed, the hydraulic fracture treatment can be designed and pumped. During the fracture treatment design, the engineer should optimize the fracture length and the fracture conductivity based upon the pre-fracture reservoir description. In order to improve the productivity of future wells, each existing well should be analyzed after the fracture treatment to determine how to improve the fracture treatment design.2,3