Simultaneous initiation and growth of multiple radial hydraulic fractures from a horizontal wellbore |
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| Institution: | 1. Schlumberger, 1 cours du Triangle, Paris La Défense, France;2. Geo-Energy Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland;1. Unconventional Natural Gas Institute, China University of Petroleum, Beijing, 18 Fuxue Road, Changping, Beijing, China;2. College of Petroleum Engineering, China University of Petroleum, Beijing, 18 Fuxue Road, Changping, Beijing, China;3. PetroChina Research Institute of Petroleum Exploration and Development, Langfang, China;1. Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77845, USA;2. Texas A&M Energy Institute, Texas A&M University, College Station, TX 77845, USA;3. Department of Petroleum Engineering, Texas A&M University, College station, TX 77845, USA;1. Langfang Branch of PetroChina Research Institute of Petroleum Exploration & Development, Langfang 065007, China;2. The Key Laboratory of Research Stimulation, PetroChina, Langfang 065007, China;3. PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, China;4. PetroChina Exploration and Production Company, Beijing 100007, China;5. PetroChina Zhejiang Oilfield Company, Hangzhou 310023, China |
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| Abstract: | Multi-stage fracturing is the current preferred method of completion of horizontal wells in unconventional hydrocarbon reservoirs. Its core component consists in simultaneously initiating and propagating an array of hydraulic fractures. We develop a numerical model for the initiation and growth of an array of parallel radial hydraulic fractures. The solution accounts for fracture growth, coupling between elastic deformation and fluid flow in the fractures, elastic stress interactions between fractures and fluid flow in the wellbore. We also take into account the presence of a local pressure drop (function of the entering flow rate) at the connection between the well and the fracture, i.e., a choke-like effect due to current well completion practices, also referred to as entry friction. The partitioning of the fluid into the different fractures at any given time is part of the solution and is a critical indicator of simultaneous (balanced fluid partitioning) versus preferential growth. We validate our numerical model against reference solutions and a laboratory experiment for the initiation and growth of a single radial hydraulic fracture. We then investigate the impact of stress interaction on preferential growth of a subset of fractures in the array. Our results show that a sufficiently large local entry friction provides a strong feedback in the system and thus can counteract elastic stress interaction between fractures, thereby ensuring simultaneous growth. We propose a dimensionless number capturing the competition between stress interaction and local entry friction. This dimensionless number is a function of rock properties, fracture spacing and injection parameters. We verify that it captures the transition from the case of simultaneous growth (entry friction larger than interaction stress) to the case of preferential growth of some fractures (interaction stress larger than entry friction). We also discuss the implication of these results for multi-stage fracturing engineering practices. |
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| Keywords: | Hydraulic fracturing Fracture shielding Fluid–solid interaction Numerical modeling System modeling |
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