内核纳米乳液用于塔西南地区钻井液的优化

Laboratory Study on Optimization of Drilling Fluid Used in Southwest Tarim Basin with Nanoemulsion

塔西南地区油气资源丰富,具有良好的勘探开发潜力,但由于地质条件复杂,钻探过程中普遍发生井漏、卡钻、划眼、坍塌、遇阻、溢流等复杂情况,其中井漏发生高达30余次,卡钻发生10余次,钻井周期最长达719 d,严重制约了该区油气资源的勘探开发进程。为了改善塔西南地区复杂频发的情况,分析了该区井壁失稳的主要原因,在此基础上通过对比筛选,最终采用自主研制的钻井液用内核纳米乳液,其是以纳米SiO2为内核的纳米乳液,粒径D50分布在100 nm左右。其油相可以抑制黏土矿物的膨胀,并且在孔隙以及裂缝中形成"软+硬"封堵体系。室内实验表明,当添加5%的纳米内核乳液进行优化时,钻井液高温高压滤失量为3.8 mL;压力传导法显示优化后较优化前平衡时间缩短了125 min,压力减小0.337 MPa;回收率实验得到优化后钻井液回收率达到85%。证实内核纳米乳液是可以作为水基钻井液的添加剂,实现对钻井液的优化。

The southwest Tarim Basin has plenty of oil and gas resources,rendering this area excellent exploration and development potential.However,the complex geological condition in this area seriously restricts the exploration and development potential.Mud losses,pipe sticking,reaming,borehole wall collapse,resistance to the tripping of drilling tools and well kick have often been encountered during drilling.Among these,mud losses happened for more than 30 times and pipe sticking more than 10 times.The longest drilling time of a well was as long as 719 d.To deal with these problems,the main factors affecting the stability of the borehole wall was analyzed,and based on the analysis,a core nanoemulsion developed by the China University of Petroleum(Beijing)was selected as borehole wall stabilizer.The core nanoemulsion is a nanoemulsion with nano SiO2 as the core,and the D50 of the cores is about 100 nm.The oil phase of the nanoemulsion can be used to inhibit the swelling of clays,and form"soft+hard"plugging system in pores and fractures.Laboratory experiment showed that a drilling fluid optimized with 5%core nanoemulsion had HTHP filtration rate of only 3.8 mL.Pressure transmission test showed that time for the balance of pressure transmission was reduced by 125 min after optimization,and the pressure was reduced by 0.337 MPa.In hot rolling test,the percent recovery of shale cuttings was 85%when tested with the optimized drilling fluid.All these facts prove that the core nanoemulsion can be used as a water base mud additive for optimizing the mud performance.