DAMAGE-CONTROL TECHNOLOGY OF OIL-BASED DRILLING FLUID FOR SHALE AND TIGHT SANDSTONE: CURRENT SITUATION, CHALLENGE AND SOLUTION

In drilling fluid systems, oil-based drilling fluid have advantages of protecting reservoir and keeping borehole stability in traditional recognition, it also have advantages of high temperature resistance, salt and calcium resistance, good lubricity and low damage, these all let oil-based drilling fluid as an important mean of complex formation drilling for high temperature deep well, high angle directional well, horizontal well and so on.But oil-based drilling fluid has the following damage: drilling fluid invade into formation and cause wettability change of rock surface; oil phase enter into formation and cause the reduce of effective flow area; emulsion block formation; migration of oil-wet solid-phase particles, solid-phase particle invasion and so on would also bring many damages to formation.This study analyzed the current situation and challenge of oil-based drilling fluid, put forward solutions, and provided some references for reservoir protection of oil-based drilling fluid.