Work

Effects of drilling fluid intrusion on the strength characteristics of layered shale

Year: 2025

Type: article

Abstract: Drilling fluid intrusion into shale has a significant effect on its strength characteristics, and related research has great significance for the safe and efficient development of shale reservoirs. By improving the conventional immersion method, this paper proposes an experimental method for drilling fluid intrusion into shale. This method can simulate the real downhole pressure system and the intrusion direction, and closer match the actual working conditions of downhole drilling fluid-shale interaction, with the intrusion depth in the layer joints obtained by nuclear magnetic resonance (NMR) scanning as an indicator to exclude the interference of drilling fluid solids in weighing, the results show a good linear fit between the depth of drilling fluid intrusion and the magnitude of compressive strength reduction. In addition, through the triaxial compression experiments on the shale cores, it is found that the strength characteristics of the shale damaged along the stratigraphic plane are much smaller than that of the shale damaged in the main body, and the intrusion of drilling fluid has a greater influence on the shale damaged along the stratigraphic plane. Finally, the reaction mechanism of amphiphilic more lipophilic shale with different types of drilling fluids is analyzed: OBDF(oil-based drilling fluid) is mainly the lubrication of filtration fluid to the laminar surface and the hydraulic spike effect, which is dominated by the physical action; the intrusion depth of WBDF(water-based drilling fluids) is slightly smaller than that of OBDF, but the filtration fluid induced hydration of illite surface causes the shale to be dispersed seriously, and the strength deterioration is controlled by both physical and chemical effects. The results of this research can give some guidance to the design of drilling fluid density, drilling fluid performance and fracturing development design when developing shale reservoirs.

Source: Heliyon

DOI: 10.1016/j.heliyon.2025.e42878

Authors: Heyuan Wang, Fuping Feng, Jianwei Zhang, Xu Han, Yuhao Zhang, Kun Zhang

Institutions: Northeast Petroleum University, China National Petroleum Corporation (China)

Language: English

Topic: Drilling and Well Engineering

Subfield: Ocean Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,270

Funder: Natural Science Foundation of Heilongjiang Province