Study On The Technology Of Horizontal Well Anti-sloughing Drilling Fluid In Yi45

Jilin Yitong area tried to use horizontal well technology to develop efficiently lowpermeability and trouble reservoir. But the construction well in this area appeared seriouscollapse phenomenon in Sheling and Shuangyang section. It affected construction safety andcomplete exploration work.This paper aims at studying horizontal well anti-sloughing drilling fluid technology in Yi45. According to indoor experiment results, in Sheling and Shuangyang layers, there are theaverage53.85%of clay mineral, which mainly have illite smectite mixed layer, illite andkaolinite but no montmorillonite. And there are a large number of micro cracks. So theselayers belong to weak expansion, weak dispersion and high dispersion speed friable hardshale. Besides, this area original ground stress data display that the maximum principal stressis vertical ground stress. Therefore, the safety Horizontal well drilling is the direction of theminimum horizontal ground stress. Formation collapse mechanism is when mud filtrateinvades into layers along cracks, the clay mineral produce hydration. Due to expansion rate ofillite and montmorillonite in illite smectite mixed layer is different, stress concentration iscaused. It leads to the spalling of friable hard shale.According to the above situation, in this paper, through improving the mud cake quality,examining field use drilling fluid and a large number of indoor experiments, BSD a mud shaleborehole wall blocking agent is determined to join in drilling fluid. The anti-sloughing drillingfluid system which is suitable for Yi45is formed. Formula is:4~5%bentonite+0.5%sodiumcarbonate+1.5%ammonium salt+0.3~0.5%potassium polyacrylate KPA+1.5%valchovite+1.5%phenolic resin-Ⅱ+2%resistant compound salt fluid loss additive KFH+1%KCl+2%resistant salt and efficient sealing fluid loss additive-120+2%HQ-1+3%lubricantYDRH-1+3%lubricant ORH-101+2%consistent lubricant+3%white oil+1%mud shaleborehole wall blocking agent BSD. Then there are indoor evaluations for two kinds of drillingfluid.Indoor experimental results show that the optimized drilling fluid has a stronger sealingcharacteristics for cracks. Its filter loss decrease obviously. Mud cake is more compact,tougher and has better compressibility. It is not easy to be drilling fluid break and scoured off.Drilling demand can be better satisfied.