Study on Improving Recovery of Highly Heterogeneous Reservoirs by Unsteady Water Injection Technology

Lun Zhao, Wenqi Zhao (), Meng Sun, Jincai Wang, Hongfei Ma, Yi Li and Xiaoliang Zhao
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Lun Zhao: PetroChina Research Institute of Petroleum Exploration & Development, China National Petroleum Corporation, Beijing 100083, China
Wenqi Zhao: PetroChina Research Institute of Petroleum Exploration & Development, China National Petroleum Corporation, Beijing 100083, China
Meng Sun: PetroChina Research Institute of Petroleum Exploration & Development, China National Petroleum Corporation, Beijing 100083, China
Jincai Wang: PetroChina Research Institute of Petroleum Exploration & Development, China National Petroleum Corporation, Beijing 100083, China
Hongfei Ma: PetroChina Research Institute of Petroleum Exploration & Development, China National Petroleum Corporation, Beijing 100083, China
Yi Li: PetroChina Research Institute of Petroleum Exploration & Development, China National Petroleum Corporation, Beijing 100083, China
Xiaoliang Zhao: College of Petroleum Engineering, China University of Petroleum, Beijing 102249, China

Energies, 2025, vol. 18, issue 1, 1-14

Abstract: Unstable water injection can effectively improve the recovery ratio of reservoirs with strong heterogeneity. However, the oil displacement mechanism and the determination method of unstable water injection parameters still need to be clarified, especially for complex fracture reservoirs, which greatly restrict the popularization and development of unstable water injection technology. This paper studies unstable water injection technology in highly heterogeneous reservoirs from the core and reservoir scales, utilizing many displacement experiments and numerical simulations. The differences in oil displacement efficiency, remaining oil distribution, pressure field, and streamlines between continuous water injection and unstable water injection are compared and evaluated. Five flow stages of unstable injection and production are precisely divided, and the microscopic and macroscopic displacement mechanism is clarified. A numerical model of two injection wells and one production is established to determine the best time to implement unstable water injection technology. Based on the principle of pressure superposition, the expression of pressure field distribution between injection and production well in each period of unstable water injection is analytically solved. This formula has provided a new development parameter optimization method aiming at the maximum pressure fluctuation range and optimized the development technology parameters in the water injection process. The results show that precise control injection and production parameters can expand water swept volume, effectively improve the degree of reserve utilization, and improve the recovery of complex reservoirs by 3–7%, which provides a reliable basis for the practical implementation of unstable water injection technology.

Keywords: unstable water injection; oil displacement mechanism; swept range; pressure field; injection and production parameter optimization (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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