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Summary Multiple hydraulic fractures are often generated simultaneously from a wellbore to increase efficiency of reservoir stimulation. Numerical modeling of such a system of fractures is computationally costly, especially if the goal is to simulate numerous stages, each containing multiple fractures, on different wells, which is the current trend in the petroleum industry. To address the challenge, this study defines a method and a workflow to represent the simultaneous propagation of multiple fractures with a reduced number of equivalent fractures that accurately describes the overall fracture geometry, the created surface area, the propped surface area, the fluid leakoff, and the resulting induced stresses, as resulting from the original configuration. A hybrid approach is used, in which a combination of physical modeling and data science is involved. We first develop a database of numerical solutions using a fully coupled hydraulic fracturing simulator. The equivalent fracture representation is quantified for each set of problem parameters presented in the database. Then, the results of the database solutions are used to tackle more general cases with field pumping schedules and rock properties. Several numerical examples are presented to validate and illustrate the developed concept.
Abstract Many engineers today do not have the training needed to fully understand the importance of fracture mechanics principles and are easily overwhelmed in trying to deal with proper proppant and fluid selections, perforation design and strategy, and on-site quality control of the fracturing process. The unfortunate reality is that many fracture designs are improperly engineered with critical reservoir and hydraulic fracture parameters either ignored or improperly addressed. Many completions are either marginally economical or produce at reduced commercial rates. Regardless of reservoir type, it is critically important to achieve a highly conductive hydraulic fracture that provides connectivity between the reservoir and the wellbore. Since its inception, fracturing and completion knowledge has expanded exponentially allowing the oil and gas industry to develop ultra-low permeability unconventional reservoirs. During the 1980's and 1990's technology pioneers such as Holditch, Nolte, Warpinski, Veatch, and others, further developed the principles of fracturing which recognize the importance of critical fracture parameters and their effect upon initial productivity and ultimate recovery. These gains in expertise have resulted in unprecedented activity in the Bakken, Eagle Ford, Barnett, Haynesville, and Marcellus with increasing activity in new reservoirs such as the Utica, Niobrara, and Mississippian. Although each of these reservoirs is unconventional, each is uniquely different with respect to lithology, permeability, and hydrocarbon chemistry and interaction. This paper will challenge the industry notion that infinitely conductive fractures are being placed in many unconventional completions. It further addresses the critical fracturing parameters required to achieve a high conductivity fracture, why they are important, and how to achieve proper proppant and fluid treatment designs. The importance of these fundamental principles is documented and illustrated by several case histories which demonstrate the value of achieving high conductivity fractures and the effects of improper design. This paper should be of great value to completion and operations engineers to help further their knowledge with regard to the importance of fracture conductivity and connectivity in all hydraulic fracturing applications.