Research on Waterproof Locking Polymer Water-based Drilling Fluid System in Shale Reservoirs
A water-based drilling fluid system suitable for shale reservoirs was developed to optimize shale stability and waterproof locking effect during drilling.The linear expansion rate test of shale rolling recovery rate was used to evaluate the effect of different treatment agents.Experimental results showed that the 0.5%WEDM+1.5%SFTH compound system could significantly improve the recovery rate of shale,while the maximum linear expansion rate was reduced from 37.6%to 16.80%.The plugging agent CMS had excellent performance in controlling fluid loss,and the coating agent KPAM had a significant effect in improving the stability of drilling fluid and reducing fluid loss.The waterproof and water-locking base drilling fluid formula was as follows:4%base slurry + 1.0%WEDM + 1.5%SFTH + 1.5%CMS + 0.3%KPAM + 2.0%op-10.The system exhibited excellent rheological properties and filter loss control capabilities under high temperature and high pressure conditions,especially in terms of temperature resistance and pollution resistance.This system maintained good stability at a high temperature of 150℃ and had strong anti-pollution ability against NaCl and CaCl2.In terms of reservoir protection,this system could effectively reduce the damage caused by drilling fluid to the reservoir,to achieve a permeability recovery rate of up to 85.69%and form a mud cake of good quality.The research results of this article are of great significance for shale gas exploitation.
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