Development and application of anti-sloughing agent QYJ

The hydrate expansion and mud-making of mudstone is the main reason for borehole wall sloughing.According to the mechanism of polymer on mudstone stabilization,a new type of anti-sloughing agent QYJ was developed,which was a type of branched chain drilling fluid auxiliary synthesized by olefin monomer and natural high polymer.Laboratory experiments were conducted to test its performance.The test result shows that the apparent viscosity of bentonite drilling fluid increases 25% when 1% QYJ is added,which is better than kalium polyacrylate,amphion coater FA367 and 10%KCl.The shale recovery rate of QYJ is apparently higher than MMH,SJ-1,CAL and KPAM.QYJ will increase the viscosity of fresh water drilling fluid and 4% NaCl drilling fluid,but the increasing scope is small because the molecular weight of QYJ is between 30000~50000.The filter loss control of QYJ is apparent while being adding to 4% NaCl drilling fluid,and 3%QYJ could decrease the API filter loss of 4% NaCl drilling fluid from 98 mL to 17.5 mL.QYJ could work well under 150℃ temperature.The field application shows that this new type of anti-sloughing agent could effectively inhibit wellbore sloughing,increase lubrication of drilling fluid and protect the oil reservoir.