MS1井超深海相地层取心实践与认识

Practice and Recognitions of Coring in the Super Deep Marine Strata of Well MS-1

为了落实川东北地区复杂地质构造情况,获取储层地质资料,MS1井是中石化勘探分公司在马路背构造高部位部署的超深预探井,完钻井深8 418 m,先后在洗象池群组、龙王庙组、灯影组等超深海相地层实施了多次取心作业。在缺乏邻井资料,面临"三高"超深井未知因素多、井控风险大、井底高温高压、裂缝发育、地层软硬交错可钻性差、工具易失稳等多重技术难题情况下,该井综合采用优化钻井液性能,合理选择取心工具及钻头,数值模拟计算优化取心钻具组合及参数,制定并严格执行详细的技术方案等措施,较好完成了取心任务,取心收获率达83.9%。MS1井超深海相地层的取心实践表明,取心工具悬挂轴承失效、取心筒临界钻压偏低,是影响取心收获率和取心进尺的主要原因。采用小复合片PDC钻头及多种适用于高研磨性地层的取心钻头,优化钻具组合和取心参数以提高工具、钻头的稳定性,在保证井控和井下安全的前提下使用井下动力钻具配合水力加压工具进行超深井取心作业,可有效提高取心收获率。

In order to figure out the complex geological structure of the northeast Sichuan basin and obtain the relevant reservoir geological data,well MS1 is an ultra-deep pre-exploration well deployed by Sinopec Exploration Company in the high part of the roadway back structure with drilling depth of 8418 m.Several drilling coring operations were carried out in formations of Xixiangchiqun,Longwangmiao and Dengying.In the absence of offset well data,and facing such several technical problems of"three high"ultra-deep wells as unknown factors,high well control risk,high bottom temperature and pressure,well developed cracks,poor drillability,tools instability,etc.,by optimizing drilling fluid performance,tools and bits optimization,simulation of BHA and drilling parameters,developing and implementing detailed technical schemes,finally the coring operation is completed successfully with core recovery rate of 83.9%.The coring practice in super deep marine strata of well MS1shows that the failure of the suspension bearing of the coring tool is the main influence reason for core recovery rate and core footage,which affects the coring harvest rate and the coring footage.Using small composite PDC bit and a variety of coring bits suitable for high abrasive formation,optimizing the drill assembly and coring parameters to improve the stability of the tool bit,and using downhole power drilling tools combined with hydraulic pressure tools for ultra-deep well coring under the premise of ensuring well control and downhole safety,can effectively improve the core recovery rate.