复合欠饱和盐水钻井液体系在顺北志留系复杂地层的应用

Application of the composite under-saturated brine drilling fluid system in drilling of Silurian complex formation in Shunbei

摘要:

顺北52A井是顺北油气田5号断裂带南部的一口探井，钻遇志留系复杂地层，成井难度大、施工风险高。该志留系地层存在盐水层，密度窗口窄，易发生漏塌共存的现象；地层裂隙发育，漏失风险高；发育大段泥岩，水敏性强，易井壁失稳。针对这些问题，顺北52A井使用了KCl-NaCl复合欠饱和盐水钻井液体系，增强了抗盐水侵的能力；且通过加入聚胺等抑制剂，共同抑制泥岩水化膨胀，增强了体系的抑制性；同时加入堵漏剂和随钻堵漏材料，预防井漏，增强了体系的封堵性。现场使用表明，该复合欠饱和盐水钻井液体系，既降低了井漏风险，又很好地维护了志留系地层井壁的稳定性，使得顺北52A井安全快速钻进，为顺北油气田5号断裂南部志留系地层的钻井施工提供了宝贵的经验和技术支持。

Abstract:

The Shunbei-52A well is an exploratory well deployed in the southern part of the 5# fault zone in the Shunbei Oil and Gas Field， and is difficult to complete with high drilling risks due to complex Silurian formation encountered. A salt water layer is present in the Silurian stratum； thus， the density window is narrow， and leakage and collapse may happen concurrently； the formation has developed fissures with high risk of leakage； there are large intervals of mudstone with strong water sensitivity， and the wellbore is easy to lose stability. Therefore， the KCl-NaCl composite under-saturated brine drilling fluid system was used for the Shunbei-52A well to enhance the ability to resist salt water intrusion； inhibitors such as polyamines were added to work together to inhibit hydration swelling of the mudstone， and enhance the inhibition of the system； in addition， the plugging agent and the plugging-while drilling material were used to prevent lost circulation， and enhance the plugging performance of the system. Field use showed that the composite under-saturated brine drilling fluid system not only reduces the risk of lost circulation， but also maintains the wellbore stability of the Silurian formation well. It enables safe and quick drilling of the Shunbei-52A well in the Shunbei Oil and Gas Field， providing valuable experience and technical support for the drilling operations in the Silurian strata in the southern part of the 5# fault.