河坝构造复杂工程地质问题与安全优快钻井技术对策

河坝构造钻井工程难度大,存在漏、塌、卡、涌、毒、硬、斜等问题,钻井效率低、周期长,需要在工程地质特征基础上,提高钻井工程工艺的针对性。本文在岩石力学实验基础上,建立工区岩石力学参数剖面,表明该构造地层岩石致密,抗压强度、抗剪切强度、硬度大,可钻性差。根据地层孔隙压力、坍塌压力、破裂压力剖面,开展井壁稳定性分析,表明该区纵向多压力系统,陆相地层坍塌压力高,易井壁失稳;海相地层异常高压,安全钻井液密度窗口窄,井壁力学稳定性差。结合工程地质特征,提出优化井身结构设计,优选气体钻井、泡沫钻井、垂直钻井、复合钻井、旋转导向钻井等钻井技术,优选钻头型号,优选钻井液,优选防漏堵漏技术等钻井对策。现场实钻证实,上述对策大幅提高了机械钻速,有效减少了钻井复杂情况,大幅缩短了钻井周期,实现了河坝构造海相超深气井优快钻井。

Complex Engineering Geological Problem and Safe Optimal-fast Drilling Countermeasures of Heba Structure

Drilling engineering is difficult in Heba structure for the problems of well leakage,wall collapse, the card drilling,wells kick,containing hydrogen sulfide,hardness,borehole inclination and so on.Drilling efficiency is low and drilling cycle is long.It needs to make the target of drilling engineering process be more accurate based on the study of engineering geological characteristics.In this paper ,it shows that this structure is hard to drill for dense rock,great compressive strength,shear strength and hardness based on the experimental rock mechanics.According to the profiles of pore pressure,collapse pressure and fracture pressure,side-wall stability is analyzed.It shows that there are multiple pressure systems in the vertical of the area.In the terrestrial formations,sidewall is easy to become unstable for the high collapse pressure ;in marine strata,mechanical stability of the sidewall is not good for abnormal high pressure and narrow safe drilling fluid density window.Combined with the engineering geological characteristics of the structure ,drilling countermeasures was proposed including optimizing casing design,optimizing gas drilling,foam drilling,vertical drilling,composite drilling,rotary steering drilling and other drilling techniques.And enhancing bit selection,optimizing drilling fluid and optimizing leak-proof sealing technology was proposed as well as.The actual drilling site confirms that the application of these countermeasures brings a substantial increase on the rate of penetration ,effective reduction on the complexity of drilling and substantial reduction on the drilling cycle.It achieved optimal-fast drilling in marine ultra-deep wells of Heba structure.