Hydraulic fracture optimization model with intelligent moving object algorithm to maximuze gas production in petroleum industry

As the demand for natural gas increases worldwide, tight and deeper gas reservoirs are becoming the target for development. However, for such reservoirs the usual approach of simply fracturing the formation will not stimulate the well adequately. Because most available commercial software may lack proper optimization tools in them and they might not have taken into consideration realistic design constraints and proper measures of merit in them. An integrated but constrained model to optimize hydraulic fracture treatment parameters has been developed to maximize gas production with minimum fracturing treatment cost. A dual objective function has also been incorporated to satisfy operator's economic constraints and also to investigate trade-off between two conflicting design objectives. Model couples both the industry experience and design constraints based on hydraulic fracture mechanics. Realistic design constraints based on field experiences are formulated mathematically and are incorporated in the model. The optimization scheme in the model is driven by an intelligent moving-object algorithm, which is basically developed based on Genetic algorithm and Evolutionary operation. The reasoning and action sequence of this algorithm is presented in simplified formulations rather than as complex mathematics. By simple reasoning and action, the algorithm improves an initial given design towards a compromised best possible design satisfying the constraints. The algorithm is capable of handling any degree of non-linearity, non-differentiability and discontinuity in the objective and constraint functions. Important design parameters are included as the free design variables which are randomly varied during optimization. Model has been applied to a hypothetical deeper gas formation to demonstrate its merits. Results show that the proposed model improves hydraulic fracturing design and provides an objective-oriented optimum design in a conflicting environment. The optimum treatment design indicates a significant incremental production (by 300% compared to production from non-fractured gas well) at lower treatment cost. With dual objective function, about 11% compromise with maximum possible production or net present value over 10 years can save up to 44% of initial treatment cost. A company may prefer such a design because it offers immediate cash saving compared to marginal NPV sacrifice over 10 years that may encounter uncertainties. This model needs further refinement for transverse fracture design in horizontal well.