塔河油田深侧钻井防塌钻井液技术

塔河油田深部巴楚组和桑塔木组地层为以伊/蒙混层或伊利石为主的硬脆性泥页岩地层,水化分散性较强且发育有微裂缝,钻井过程中易因泥页岩水化而导致井壁失稳,为此,提出了"抑制表面水化-物化封堵-有效应力支撑"三元协同防塌对策,并构建了三元协同防塌钻井液。室内性能评价试验结果表明:三元协同防塌钻井液抗温达170℃、抗盐5.0%、抗钙0.5%~1.0%、抗劣土8.0%,泥页岩膨胀率和滚动回收率分别为5.05%和91.33%,能封堵宽400 μm的裂缝,承压能力达到4 MPa。三元协同防塌钻井液在塔河油田20余口井进行了应用,均未发生由于井壁失稳造成的井下故障,桑巴楚组和桑塔木组地层的井径扩大率平均降低63.4百分点,建井周期平均缩短4.3 d。这表明,三元协同钻井液防塌技术可有效解决塔河油田深侧钻井巴楚组和桑塔木组地层的井壁失稳问题。 

Anti-Sloughing Drilling Fluid Technology for Deep Sidetracking Wells in the Tahe Oilfield

The deep Bachu and Sangtamu Formation in the Tahe Oilfield are composed of an illite-montmorillonite mixed layer or hard brittle shale formations dominated by illite with strong water dispersion and development of micro-fractures.During drilling operations, wellbore instability can be encountered due to shale hydration.To eliminate these problems, a coordinated anti-collapse program with three elements was developed:sealing and consolidating the side well, inhibiting surface hydration and providing the effective stress support by reasonable drilling fluid density.In addition, anti-collapsing drilling fluids were developed.The evaluation results showed that the newly developed three-element anti-collapse drilling fluid had a temperature tolerance of 170℃, preferable contamination resistibility (5%NaCl, 0.5%-1% CaCl2, and 8% poor clay) strong anti-collapsing capacity (5.05% of shale swelling ratio and 91.33% rolling recovery rate) and favorable well-sealing performances (4 MPa of pressure-bearing capacity for 400 μm simulated fractures).Successful field applications were carried out in the Tahe Oilfield more than 20 wells.There were no downhole problems induced by wellbore instability.The average expansion rate was reduced by 63.4% compared with completed adjacent wells in the same block.The construction period was shorted by 4.3 d.Results showed that the wellbore instability problems of deep sidetracking wells in the Tahe Oilfield can be overcome through the effective deployment of a three-element anti-collapse drilling fluid technology.