An Experiment-Based Study of Formation Damage Using a Microetching Model Displacement Method.

Area of Science:

• Petroleum Engineering
• Geosciences
• Materials Science

Background:

• Drilling fluid is vital for oil and gas exploration, controlling pressure and removing cuttings.
• Drilling fluid infiltration into rock pores causes formation damage, reducing oil and gas recovery.
• The microscopic mechanisms of fluid-induced formation damage remain unclear.

Purpose of the Study:

• To investigate the microscopic mechanisms of formation damage caused by oil-based drilling fluid.
• To elucidate the roles of solid particles and fluid interfaces in damaging low-porosity, low-permeability sandstone.

Main Methods:

• Development of a novel microetching model (MEM) with displacement equipment.
• Laser etching of rock pore networks from thin-section images onto aluminum sheets.
• Observation of oil-based drilling fluid displacing stratum water in the MEM, supplemented by core flooding, permeability tests, and SEM.

Main Results:

• Identified solid damage and liquid damage as primary forms of formation damage.
• Solid damage results from 0.1–30.0 μm solid particles blocking small pores and narrow throats.
• Liquid damage is attributed to water lock and hydrocarbon lock effects at oil-water, gas-water, or oil-gas-water interfaces.

Conclusions:

• Formation damage in low-porosity, low-permeability sandstone by drilling fluid is a dual process of solid and liquid effects.
• Solid particles in drilling fluid obstruct pore structures, while fluid interfaces impede hydrocarbon flow.
• These findings provide critical insights for mitigating formation damage and enhancing oil and gas recovery.