An integrated model for multiobjective design optimization of hydraulic fracturing

An integrated novel model for hydraulic fracturing design optimization is presented, which recognizes complex interactions between a hydraulically coupled fracture geometry module, a hydrocarbon production module and an investment-return cash flow module. Free design variables are identified and various design constraints are formulated, which must be satisfied so that an optimum design obtained is executable in the field using the specified surface equipment (pump, tubing, etc.) and that the treatment does not cause any undesirable formation damage by uncontrolled fracture growth and/or multiple secondary fracture initiation. The model is formulated within the framework of a multivariate and multiobjective optimization method, which is based on the combined features of Genetic Algorithm and Evolutionary Operation. A 2D fracture model is used to establish relationships between treatment parameters and fracture growth. The potential for hydraulic fracturing design improvement is demonstrated by application to a tight gas reservoir. Results show that the proposed model is instrumental in improving hydraulic fracturing design and achieving a goal-oriented optimum design in a conflicting environment. About 12% compromise with maximum possible production, or net present value (NPV), over 10 years can save up to 44% of initial hydraulic fracturing treatment cost. Furthermore, the 88% production, or net present value, as a result of an optimum treatment program is significantly higher than any arbitrary design. The issues of real-time design modification, however, are not included in this study.