Applications of the Net Present Value (NPV) in the Optimization of Hydraulic Fractures

Abstract

Abstract The concept of the net present value (NPV) has been introduced as a systematic approach in the optimization of hydraulic fractures. The scheme combines reservoir and well performance, rock mechanics principles, fracture propagation models, fracturing fluid rheology, proppant transport, and stimulation treatment variables. The method involves the graphing of a range of fracture lengths (or other treatment variables) against the NPV. The optimum length corresponds to the maximum NPV. Two field cases (one for an oil and another for a gas well) are used for fracture treatment optimizations. Studies for each well show the impact of parameter variation, including the choice of proppant, fracturing fluid, pump rate, treatment pressure (controlled by tubular selection), and volumes of fluid and proppant injected. Variables affecting fractured well performance are also examined, e.g., tubing size and wellhead or bottomhole flowing pressure. The optimization technique also shows the cost of uncertainty and the importance to know—before the treatment—the reservoir permeability, height, and porosity. In particular, an order of magnitude variation in the permeability results in a substantial difference in the optimum fracture length (several hundred feet) and the implied maximum NPV. A study on the effect of the closure stress on proppant performance and the resulting NPV ratio also is included. This systematic approach to hydraulic fracture design is an important tool in the identification of the crucial parameters affecting a particular job, and allows their control before and during the treatment.