高效驱油清洗液的研制与现场应用

Research and Field Application of High Efficiency Oil Displacement Preflush Fluid

页岩气水平井油基钻井液施工过程中,泥饼和油膜清除困难,易出现固井质量差、甚至环空带压等工程技术难题。基于微乳增溶原理,以脂肪醇、环氧乙烷和环氧丙烷为原料制备了改性聚氧乙烯-聚氧丙烯嵌段共聚物表面活性剂,并与十二烷基苯磺酸钠复配制得驱油清洗剂QX-1。将QX-1与隔离剂GL-1、加重剂重晶石粉(23μm)和水混合制得高效驱油清洗液。评价了该清洗液的沉降稳定性、清洗效率、界面胶结强度及相容性等,并在涪陵页岩气井产层固井进行了现场应用。结果表明,高效驱油清洗液在60~90℃下的沉降稳定性良好,驱油清洗效率高。QX-1加量为20%时,高效驱油清洗液对模拟固井一界面的清洗效率达93.94%,对模拟固井二界面的泥饼去除效率达91.16%;且清洗后的界面具有润湿反转特性,有效增大了界面的胶结强度。现场应用结果表明,高效驱油清洗液与涪陵页岩气田油基钻井液和固井水泥浆的配伍性良好,固井合格率100%,固井优质率达92.73%,可改善由于界面胶结质量差导致的套管环空带压问题。

During the process of oil-base drilling fluid in shale gas horizontal well,it is difficult to remove mud cake and oil film,leading to poor cementing quality and even sustained casing pressure.Based on the principle of micro-emulsion solubilization,a modified polyoxyethylene-polyoxylpropylene(PEO-PPO)block copolymer surfactant was prepared by using fatty alcohol,ethylene oxide and propylene oxide as raw materials.Then the oil displacement agent QX-1 was developed by the block copolymer surfactant and sodium dodecyl benzene sulfonate.The high efficiency oil displacement preflush fluid was prepared by mixing QX-1 with isolating agent GL-1,weighting agent barite powder with 23μm(600 mesh)and water.The sedimentation stability,cleaning efficiency,interface bonding strength and compatibility of this prefluish fluid were evaluated,and it was applied on shale gas production layer cementing in Fuling area.The experiment results showed that the high efficiency oil displacement prefluish fluid had good sedimentation stability at 60-90℃and excellent performance of cleaning efficiency.When the dosage of QX-1 was 20%,the cleaning efficiency at the simulated casing-cement interface was up to 93.94%and the mud cake removal efficiency at the cement-formation interface was 91.16%.And these two interfaces had reverse wetting properties after modified by high efficiency oil displacement preflush fluid,which effectively increased the interface bonding strength.Field application results showed that the compatibility of high efficiency oil displacement preflush fluid with oil-based drilling fluid and leading cement slurry in Fuling shale gas field was good.The cementing pass rate and the cementing quality rate was 100%and 92.73%respectively,which could improve the sustained casing pressure caused by poor interface cementing quality.