Determination of Fracture Geometry Using Field Data Coupled With a Fracture Simulator

Abstract

SPE Members Abstract A practical analysis technique for the determination of fracture geometry using actual treatment signals has been developed using a commercial 3D fracture simulator. This simulator allows the use of treatment data as well as reservoir and fluid properties to be incorporated into the determination of fracture geometry. This analysis has been applied to typical, water-based fluid treatments using readily available surface treatment data. Although the simulator has the option to incorporate energized and foam fluids, we have not yet used it to analyze these type jobs due to the lack of treatment bottom hole pressures and temperatures. The analysis technique has been applied to several treatments in various parts of the United States. The process involves taking treatment data (injection rate, proppant concentration, etc.) and obtaining a history match of the surface treating pressure. Several practical analysis techniques are employed to enhance the confidence in the resulting fracture geometry. In the case where mini-fracture data is available, the minifracture treating and falloff pressure responses are matched with the simulator to determine the corresponding reservoir parameters. Using the mini-fracture defined parameters, the main treatment is analyzed and history matched. Based on the resultant fracture geometry obtained from the simulator, future treatment designs can be altered or refined to obtain the optimum fracture geometry for the reservoir. Introduction The industry has long sought better methods for calculating actual fracture geometries than the typically used fixed height approximation models. The Gas Research Institute (GRI) has conducted several staged field experiments in an effort to develop more representative models of fracture propagation. The model used in this analysis technique was developed from this GRI research with Industry involved research. The characteristics of this commercially available, PC based, lumped-parameter, 3D, completely integrated hydraulic fracturing model include: leading edge effects (non-linear rock dilatancy); multiple stress and permeability layers; relative insensitivity of fracture width to frac fluid rheology; proppant addition effects; and pipe and perforation friction effects. This model also allows the use of digitized data from the actual treatment for history matching which improves the quality of fracture geometry predictions. This paper outlines a practical analytical process to determine actual fracture geometries with the aid of the above mentioned fracture simulator. The analysis technique involves the following steps coupled with the use of actual treatment data:Establishing the frac fluid parameters n' and K'.Matching the total friction pressure.Matching the pressure falloff at the end of pumping, which is indicative of leakoff. P. 631^