克拉苏构造带超深盐下大斜度井钻井关键技术

Key techniques for drilling ultra-deep pre-salt highly-deviated wells in Kelasu tectonic belt

克拉苏构造带深部地层地质条件复杂,前期多口钻探断层带油气藏井被迫提前完井。为了提高钻井成功率,提出了采用大斜度井避开部分断层,降低事故复杂的钻井技术思路。结合区域地质特征,分析了超深层盐下大斜度井面临的套管必封点不确定性、井眼轨道设计及轨迹控制难、盐底卡准层位难度大、盐层大斜度井段套管下入摩阻大等技术难点,基于克拉苏构造带膏盐岩蠕变实验结果,优化原七开直井井身结构为五开盐下大斜度井身结构,探索了“旋转导向+同心扩眼器”BHA组合在膏盐层定向钻井方法,试验了“常规卡层技术+GLASS前视技术”盐底卡层组合形式,分析制定了大斜度膏盐层套管安全下入关键技术措施,形成一套适合于克拉苏构造带的超深盐下大斜度井钻井关键技术。克深A、克深B等6口井现场应用表明,该技术可以解决克拉苏构造带超深盐下大斜度井钻井存在的技术难题,钻井成功率100%,满足勘探开发的需求。

The Kelasu tectonic belt presents complex geological conditions in deep formations,leading to premature completion of multiple wells due to encountering fault zones during drilling.To enhance drilling success rates,a strategy employing highlydeviated wells to bypass certain fault zones and to mitigate drilling complexities was proposed.Considering the regional geological characteristics,the technical challenges faced in drilling ultra-deep pre-salt highly-deviated wells,including uncertainties in casing shoe sealing points,difficulties in wellbore trajectory design and control,challenges in precise positioning at the salt bottom,and significant friction encountered during casing running in highly-deviated sections in salt layers,were analyzed.Based on rheological experiments on salt rock creep in the Kelasu tectonic belt,the original seven-section vertical wellbore design was optimized into a five-section design for pre-salt highly-deviated well structure.The directional drilling method in salt formations using a“rotary steering+concentric reamer”bottom hole assembly(BHA)was explored,a new combination of“conventional pipe stick techniques+GLASS forward-viewing technology”for salt bottom pipe stick was tested,and key technical measures for safe casing running in highly-deviated salt formations were analyzed and formulated,leading to the development of a set of crucial drilling techniques tailored for ultra-deep pre-salt highly-deviated wells suitable for the Kelasu tectonic belt.Field applications in six wells i ncluding Well Keshen A and Well Keshen B demonstrate that this technology can effectively address the technical challenges encountered in drilling ultra-deep pre-salt highly-deviated wells in the Kelasu tectonic belt,which may achieve a drilling success rate of 100%,meeting the exploration and development demands.