顺北油气田碳酸盐岩破碎性地层防塌钻井液技术

Anti-Collapse Drilling Fluid Technology for Broken Carbonate Formation in Shunbei Oil and Gas Field

为了解决顺北油气田奥陶系碳酸盐岩破碎性地层易发生井壁坍塌的问题,从地质构造特征、地层裂缝发育及充填程度和井壁岩块受力等方面分析了井壁坍塌的原因,发现造成井壁坍塌掉块的主要原因是强挤压段应力集中、地层微裂缝发育和定向井段受重力影响。虽然地层破碎、应力集中无法改变,但可以提高钻井液的封堵性能,通过有效充填、封堵微裂缝阻止压力传递,同时钻井液保持较高的密度支撑井壁,从而解决井壁坍塌问题。为此,综合考虑强化钻井液封堵能力、控制钻井液高温高压滤失量和优化钻井液动塑比等,优选了防塌钻井液配方,并保持较高的钻井液密度以支撑井壁,形成了防塌钻井液技术。该技术在顺北X井进行了现场试验,钻进中扭矩稳定,机械钻速较高,井径扩大率较小,防塌效果良好,可为其他油气田破碎性地层的高效、安全钻井提供借鉴。

In order to solve the problem of wellbore collapse in broken carbonate formation of Ordovician in Shunbei Oil and Gas Field,this paper analyzed the cause of wellbore collapse from the characteristics of geological structure,the development and filling of fractures in the formation,and the stress on the wellbore block.It was found that the stress concentration in the strong compression section,the development of micro fractures in the formation and the influence of gravity on the directional interval were the main causes of wellbore collapse.According to the analysis,since the formation fragmentation and stress concentration could not be changed,the problem of wellbore collapse could only be solved by improving the plugging performance of the drilling fluid through effective filling and plugging of micro fractures,preventing the transmission of pressure and maintaining a high density for stress support.Therefore,the anti-collapse drilling fluid was prepared from the aspects of strengthening the plugging ability,controlling the filtration at high temperatures and pressures,optimizing the yield point and plastic viscosity ratio of the drilling fluid,etc.,so as to improve its anti-collapse performance.The field test of Well Shunbei X showed that after adopting this anti-collapse drilling fluid technology,the drilling torque was stable,the ROP was high,the hole diameter enlargement ratio was small,and the anti-collapse effect was good,which could provide reference for efficient and safe drilling under the similar conditions.