Abstract
Uncontrolled growth of hydraulic fractures and initiation of secondary multiple fractures may occur due to execution of a fracture treatment with inappropriate values for various treatment parameters: fracturing fluid viscosity, injection rate, injection time and proppant concentration. Such uncontrolled fracturing is not only uneconomic due to increased treatment cost but may also damage the formation irreversibly, resulting in productivity lower than even unfractured wells. Also excessive pressure drawdown during production from hydraulically fractured wells may result in sand production due to mechanical failure of perforation tunnels. This paper presents an integrated model to optimize treatment parameters in order to achieve maximum possible Net Present Value (NPV) while the above mentioned formation damage aspects are avoided by satisfying various constraints. These constraints are formulated as functions of treatment parameters, fracture geometry and mechanical and petrophysical properties of the reservoir so that the critical conditions that induce the formation damage in different modes do not become active. Additional constraints are also formulated to ensure that the optimally designed treatment can be executed in the field by using the specified surface equipment, and fracture width restriction does not occur. A genetic-evolutionary computing algorithm is integrated to solve the constrained treatment design problem such that it finds optimum values for treatment parameters and fracture geometry that are formation compatible. The capability of the model is demonstrated in the paper by application to a gas reservoir.
