Title: Semi-analytical evaluation for water-alternating-CO₂ injectivity in tight oil reservoirs

Authors: Fankun Meng; Yuliang Su; Wendong Wang; Qun Lei; Dongbo He

Addresses: Department of Gas Filed Development, PetroChina Research Institute of Petroleum Exploration and Development, Beijing, 100083, China ' School of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong, 266580, China ' School of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong, 266580, China ' Department of Unconventionals, PetroChina Research Institute of Petroleum Exploration and Development, Beijing, 100083, China ' Department of Unconventionals, PetroChina Research Institute of Petroleum Exploration and Development, Beijing, 100083, China

Abstract: This paper presents a new semi-analytical model to estimate the bottom-hole pressure drop for a water-alternating-CO₂ injection well in a horizontal, linear, homogenous tight oil reservoir with constant-pressure boundary. In this model, the conventional Buckley-Leverett (B-L) equations are modified to consider the interaction between CO₂ and oil or water. The Laplace transformations and Stehfest inversion algorithm are employed to solve the model. Through the comparison of pressure profile between proposed and numerical models at different times, and the match of pressure drop with experiments and numerical simulation data collected from published paper, the model accuracy is validated. The sensitivity analysis indicates that with the reduction of CO₂-oil interfacial tension and the increase of CO₂ slug size, the water injectivity will be improved. The water injectivity strongly depends on the reservoir permeability. When the formation permeability is lower than 0.075 mD, the injectivity will decline drastically. [Received: December 12, 2017; Accepted: June 6, 2018]

Keywords: water-alternating-CO₂ flooding; injectivity; modified B-L equations; tight oil reservoirs; sensitivity analysis.

DOI: 10.1504/IJOGCT.2020.106704

International Journal of Oil, Gas and Coal Technology, 2020 Vol.24 No.1, pp.62 - 84

Received: 04 Dec 2017
Accepted: 06 Jun 2018
Published online: 20 Apr 2020 *

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