Coupling of Production Forecasting, Fracture Geometry Requirements and Treatment Scheduling in the Optimum Hydraulic Fracture Design

Abstract

There are a number of considerations to be made in the process of designing a fracturing stimulation treatment. The reservoir deliverability, well producing systems, fracture mechanics, fracturing fluid characteristics, proppant transport mechanism, operational constraints and economics should be considered and integrated in order to obtain the most cost-effective design and to maximize the benefit of a well stimulation treatment. The main purpose of this work is to develop an analytical scheme which mathematically couples each elements as described above. The criteria used to determine the optimum size of the treatment are:optimize reservoir deliverability,maximize propped fracture penetration,optimize pumping parameters,minimize treatment cost, andmaximize economic returns of the well. Firstly, an analytical inverse algorithm has been derived based on 2-D PKNC (Perkins, Kern, Nordgren and Carter) and KZGD (Khristianovic, Zheltov, Geertsma and de Klerk) formulations. It allows us to calculate the fluid and proppant volume needed for a desired fracture geometry and conductivity. Secondly, a technique to search for optimal pumping parameters and to maximize the proppant coverage for a given hydraulic penetration is developed. This allows us to optimize the propped geometry taking into account the operational constraints. Thirdly, a coupling algorithm is developed to link the reservoir producibility, well producing systems and the optimized fracture geometry. This enables us to optimize the wellhead deliverability based on the balance between the reservoir and the fracture characteristics. Finally, the overall economic analysis is performed to calculate the net present value for various design options. The most cost-effective treatment design can then be determined based on the point of diminishing return on the well's net present value. Introduction Hydraulic fracturing has been recognized to be an effective means for enhancing well productivity and recoverable reserves, especially for low permeability reservoirs. Over the years, a significant amount of effort has been directed to the understanding of the physics involved in such complicated processes. As a result, new techniques have been developed to enhance our abilities to optimize the fracturing stimulation treatment. The fracture design procedures currently practiced in the industry include:the prediction of well producibility from various fracture penetrations and conductivities;parametric studies on the fracture geometry requirements;the selection of appropriate types of fracturing materials; andthe determination of fracture design criteria based on maximum economic returns of the well. Various reservoir simulators, hydraulic fracture propagation simulators and economic models are often run on a trial-and-error basis until the desired design criteria are met. This is a time-consuming and ineffective exercise. Ideally, the reservoir deliverability, well producing systems, fracture mechanics, fracturing fluid characteristics, proppant transport mechanism, operational constraints and economics should be considered and integrated in order to obtain the most cost-effective design. The following outlines the key design parameters for each of the elements under consideration. P. 485^

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