The Water Flooding Seepage Mechanism in the Inter-Fractures of Horizontal Wells in Tight Oil Reservoirs
Xinli Zhao1,*, Qianhua Xiao2, Xuewei Liu3, Yu Shi4, Xiangji Dou1, Guoqiang Xing1
1 School of Petroleum and Natural Gas Engineering, Changzhou University, Changzhou, 213164, China
2 School of Oil and Gas Engineering, Chongqing University of Science & Technology, Chongqing, 401331, China
3 Research Institute of Petroleum Exploration & Development, PetroChina Company Limited, Beijing, 100083, China
4 College of Petroleum Engineering, Xi’an Shiyou University, Xi’an, 710065, China
* Corresponding Author: Xinli Zhao. Email: 
Fluid Dynamics & Materials Processing https://doi.org/10.32604/fdmp.2024.052646
Received 10 April 2024; Accepted 24 July 2024; Published online 12 November 2024
Abstract
Tight oil reservoirs face significant challenges, including rapid production decline, low recovery rates, and a lack of effective energy replenishment methods. In this study, a novel development model is proposed, based on inter-fracture injection following volumetric fracturing and relying on a high-temperature and high-pressure large-scale physical simulation system. Additionally, the CMG (Computer Modelling Group Ltd., Calgary City, Canada) software is also used to elucidate the impact of various single factors on the production of horizontal wells while filtering out the interference of others. The effects of fracture spacing, fracture half-length, and the injection-production ratio are studied. Results indicate that under rejection pressures of 6.89, 3.45, and 1.88 MPa, the times to establish stable flow are 50, 193, and 395 min, respectively. Higher injection pressures lead to an increased oil recovery efficiency, with the highest observed efficiency at 16.93%. This indicates that, compared with conventional medium and high permeability reservoirs, tight oil reservoirs exhibit similar pore throats and larger capillary forces when oil and water flow in both phases. Higher pressures reduce capillary forces, displacing more oil droplets, thus enhancing oil recovery efficiency. Moreover, under inter-fracture displacement conditions, the pressure gradient at both the injection and production ends remain consistent, with minimal pressure loss near the wellbore. This feature ensures that the crude oil in the middle of the reservoir also possesses displacement energy, thereby enhancing overall crude oil displacement efficiency.
Keywords
Tight oil reservoir; volumetric fracturing; inter-fracture injection and production; oil drive efficiency; waterflooding
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