Open Access

ARTICLE

Mechanisms and Mitigation of Heavy Oil Invasion into Drilling Fluids in Carbonate Reservoirs

Yang Yu^1,2, Sheng Fan^1,2, Zhonglin Li^1,2, Zhong He^1,2, Jingwei Liu^3,*, Peng Xu^3,*

1 Sinopec Group Northwest Petroleum Branch, Urumqi, 650100, China
2 Key Laboratory of SINOPEC Ultra Deep Well Drilling Engineering Technology, Beijing, 102206, China
3 National Engineering Research Center for Oil & Gas Drilling and Completion Technology, School of Petroleum Engineering, Yangtze University, Wuhan, 430100, China

* Corresponding Authors: Jingwei Liu. Email: ; Peng Xu. Email:

(This article belongs to the Special Issue: Fluid and Thermal Dynamics in the Development of Unconventional Resources III)

Fluid Dynamics & Materials Processing 2025, 21(8), 1875-1894. https://doi.org/10.32604/fdmp.2025.066404

Received 08 April 2025; Accepted 23 June 2025; Issue published 12 September 2025

Abstract

Drilling operations in carbonate rock heavy oil blocks (e.g., in the Tahe Oilfield) are challenged by the intrusion of high-viscosity, temperature-sensitive formation heavy oil into the drilling fluid. This phenomenon often results in wellbore blockage, reduced penetration rates, and compromised well control, thereby significantly limiting drilling efficiency and operational safety. To address this issue, this study conducts a comprehensive investigation into the mechanisms governing heavy oil invasion using a combination of laboratory experiments and field data analysis. Findings indicate that the reservoir exhibits strong heterogeneity and that the heavy oil possesses distinctive physical properties. The intrusion process is governed by multiple interrelated factors, including pressure differentials, pore structure, and the rheological behavior of the heavy oil. Experimental results reveal that the invasion of heavy oil occurs in distinct phases, with temperature playing a critical role in altering its viscosity. Specifically, as temperature increases, the apparent viscosity of the drilling fluid decreases; however, elevated pressures induce a nonlinear increase in viscosity. Furthermore, the compatibility between the drilling fluid and the intruding heavy oil declines markedly with increasing oil concentration, substantially raising the risk of wellbore obstruction. Simulation experiments further confirm that at temperatures exceeding 40°C and injection rates of ≥0.4 L/min, the likelihood of wellbore blockage significantly increases due to heavy oil infiltration. Based on these insights, a suite of targeted mitigation strategies is proposed. These include the formulation of specialized chemical additives, such as viscosity reducers, dispersants, and plugging removal agents, the real-time adjustment of drilling fluid density, and the implementation of advanced monitoring and early-warning systems.

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Keywords

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