Open Access

ARTICLE

Water Huff-n-Puff Optimization in High Saturation Tight Oil Reservoirs

Zhengyang Zhang^1,2, Jing Sun^1,2,*, Xin Shi³, Dehua Liu^1,2

1 School of Petroleum Engineering, Yangtze University, Wuhan, 430100, China
2 Cooperative Innovation Center of Unconventional Oil and Gas (Ministry of Education & Hubei Province), Yangtze University, Wuhan, 430100, China
3 Engineering Cost Department of PetroChina Changqing Oilfield Company, Xi’an, 71000, China

* Corresponding Author: Jing Sun. Email:

Fluid Dynamics & Materials Processing 2025, 21(3), 509-527. https://doi.org/10.32604/fdmp.2025.060393

Received 31 October 2024; Accepted 15 January 2025; Issue published 01 April 2025

Abstract

High saturation pressure reservoirs experience rapid pressure decline during exploitation, leading to significant changes in crude oil phase behavior and a continuous increase in viscosity after degassing, which adversely affects oil recovery. This challenge is particularly acute in tight sandstone reservoirs. To optimize the development strategy for such reservoirs, a series of experiments were conducted using core samples from a high saturation tight sandstone reservoir in the JS oilfield. Gas-dissolved crude oil was prepared by mixing wellhead oil and gas samples, enabling the identification of the critical point where viscosity changes as pressure decreases. Oil-water relative permeability experiments under varying viscosities revealed crude oil mobility trends with declining production pressure. Additionally, physical and numerical simulations of water huff-n-puff processes were performed, while nuclear magnetic resonance methods explored the effects of soaking time on oil-water imbibition. Key findings include the following optimal parameters for water huff-n-puff: (1) initiating the process when formation pressure is 75% of its original level, (2) a soaking time of 48 h, (3) an injection volume of 0.6 pore volumes per cycle, and (4) a 5 MPa pressure reduction per production stage. Numerical simulations further recommend initiating water injection after one year of depletion, with an optimal cumulative injection volume of 18,000 cubic meters, a soaking time of 10 days, and a producing pressure difference of 5 MPa.

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Keywords

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