Research On A New Membrane Shielding Drilling Fluid

Wellbore stablizing and reservoir protecting technology are indispensable technicalmeasures in modern petroleum exploration and development process. The commonly useddrilling fluid systems that have the wellbore stablizing and reservoir protecting properties areMMH drilling fluid,polyols drilling fluid,techniques of auto-adapting shielding and temporaryplugging drilling fluid and oil-based drilling fluid. But there are some limitations of thesedrilling fluids. For instance, superfine calcium carbonate does not have the flexibility anddeformability and its adaptability to the formation is poor. It doesn't have inhibiting abilityeither. Alcohol polymer is easy to blister, ultra-low permeability products has remarkablethickening effect while their inhibiting ability is poor.For the existence of limitations of current additives, we developed a new membraneshielding additives.The new product has better high temperature resisting property, and thevery low permeability shielding films can be quickly formed in the groud.Laboratoryexperiments show that temperature resisting property of the membrane shielding agent is upto 120℃. The anti-collapsing and reservoir protecting properties are evaluated in this papervia the expansion experiment,shale recovery experiment and the core immersion experiment.The results shows that the new membrane shielding agent has good inhibiting andanti-collapsing properties. Meanwhile the results of prmeability recovery and sand-bedfiltration experiments show that plug the reservoir quickly and adaptively.Through the process of paper research and micro-visualization research. We find out thatthe membrane shielding agent protect the reservoir and the stability of wellbore through theeffects of chemical adsorption, physical plugging and bridge plugging.Through single dose and formulation optimization study,the paper study out two formulaof the new membrane shielding drilling fluid which have good inhibit properties,rheologicalproperties,anti-pollution properties and protect reservoir properties, We cunducted severalfield applications in Xinjiang with this new agent and the results showed that this agent hadgood reservoir protecting and anti-collapsing properties. All wells achieved good applicationresults.