Multivariate Fracture Treatment Optimization for Enhanced Gas Production from Tight Reservoirs

An excessive high treatment pressure may be required to execute a production enhancing hydraulic fracture treatment in a tight-gas reservoir, particularly if the treatment is designed with inappropriate values for treatment parameters: fracturing fluid viscosity, injection rate, injection time and proppant concentration. Such a high treatment pressure may not only exceed the delivering capacity of specified surface equipment (pump, pressure rating devices and downhole tubing), but may also cause multiple fracture initiation. Multiple fracture initiation may cause near-wellbore tortuosity complexities and large fluid loss, and thus may damage the formation irreversibly that results in productivity lower than even unfractured wells. This paper presents an integrated model for multivariate fracture treatment optimization with adequate trade-offs between production enhancement, equipment capacity and formation compatibility requirements. The model considers both fracture geometry (length, height, width etc.) as well as treatment parameters as free design variables. Compatibility relationships between reservoir properties, treatment parameters and fracture growth are formulated using a modified pseudo-3D fracture model. Design constraints are formulated to ensure that the final optimum design is compatible with specified equipment and formation characteristic to avoid the above-mentioned fracture complexities. The optimal design of fracturing treatments to maximize cumulative production is demonstrated in the paper by a series of applications of the model to a tight-gas reservoir. Sensitivity results of various parameters are also presented in the paper.