页岩水基钻井液用高性能纳米封堵剂室内研究与评价

Laboratory Research and Evaluation of High-performance Nano-plugging Agents for Shale Water-based Drilling Fluids

页岩中的纳米孔隙居多,且一般为亲水性,钻井液中的水在压差和毛管力等力的作用下,会通过纳微米孔缝侵入页岩内部,故对微纳米孔缝的有效封堵是防止页岩水化膨胀、维持井壁稳定的重要措施。以苯乙烯、乙二烯和甲基丙烯酸等为主要原料制备了纳米封堵剂BDJ,其粒径主要集中在130 nm左右。通过页岩抗压实验测试了其致密封堵性能,探究其作用机理。结果表明:待测液为含3%BDJ的基浆时,岩心末端压力降低至2.34 MPa后趋于稳定,相较于岩心顶端压力6.9 MPa压力损耗下降了66.04%,表明封堵剂BDJ具有很好的承压封堵能力;压入硬度实验结果表明:含3%BDJ封堵浆封堵后,岩心压入硬度平均值为450.90 MPa,相比基浆作用后岩心压入硬度提高了58.09%。结合岩心封堵评价结果可知,封堵剂BDJ可在一定程度上封堵页岩微纳米孔隙,阻缓液相侵入和压力传递,降低水和压力对岩石的破坏性,从而使岩心压入硬度表现出一定程度的提高。

Nanopores in shale are predominant and generally hydrophilic,and water in drilling fluid will invade into the shale interior through nano-micron pores under the action of forces such as pressure difference and capillary force,so effective plugging of micro-nano pores is an important measure to prevent shale hydration and swelling and maintain well wall stability.In this paper,BDJ,a nano plugging agent,was prepared with styrene,ethylene and methacrylic acid as the main raw materials,and its particle size was mainly concentrated in about 130 nm.The dense plugging performance was tested by shale pressure test to investigate its mechanism of action.The experimental results showed that the pressure at the end of the core decreased to 2.34 MPa and stabilized when the base slurry containing 3%BDJ was used as the test solution,and the pressure loss decreased by 66.04%compared with the pressure at the top of the core of 6.9 MPa,indicating that BDJ had good pressure-bearing and sealing ability.The experimental results showed that the average compressive hardness of cores sealed with 3%BDJ plugging slurry was 450.90 MPa,which was 58.09%higher than that of cores after the action of base slurry.Combined with the core plugging evaluation results,it was seen that the plugging agent BDJ could seal the shale micro-nano pores,retard the liquid phase intrusion and pressure transfer,reduce the destructiveness of water and pressure on the rock,and thus the core indentation hardness showed a certain degree of improvement.