陆相页岩气水平井固井技术——以延长石油延安国家级陆相页岩气示范区为例

鄂尔多斯盆地伊陕斜坡的上三叠统延长组及下二叠统山西组具有良好的页岩气成藏条件,陕西延长石油(集团)有限责任公司采用水平井分段压裂技术对该区页岩气进行开发。针对水平井固井过程中存在的油基钻井液清洗困难、长水平段套管难以居中、固井过程中易发生漏失、水平井及分段压裂对水泥环要求高、长封固段固井附件易失效等技术难题,开展了相关技术研究,获得了解决上述问题的技术措施:1在该示范区通过采用清油型前置液多级冲洗工艺,有效地冲洗界面残留油膜,提高油基钻井液冲洗效率;2新研制的水平井专用扶正器能有效降低管柱下入摩擦阻力,保证套管的居中度;3通过提高地层承压能力、优化浆柱结构实现平衡压力固井;4优选韧性材料提高水泥环的耐冲击能力,较好地满足了页岩气水平井分段压裂工艺对水泥石性能的要求;5研制的高性能固井附件,保证了长封固段水平井施工安全。所获成果已在该示范区的4口页岩气水平井中进行了应用,固井一次成功率达100%,固井质量优良率达100%,取得了良好的固井效果。

Cementing technology for horizontal wells of terrestrial shale gas:A case study of the Yan'an national terrestrial shale gas E&P pilot area

The Yanchang and Shanxi Fms in the Ordos Basin are endowed with excellent shale gas accumulation conditions. Horizontal well staged fracturing technologies were taken by the Shaanxi Yanchang Petroleum (Group) Co., Ltd. for shale gas exploration and production. This paper focuses on discussing many technological problems in cementing, e.g., it is difficult to clean oil-based drilling fluid and align long horizontal interval casing, fluid loss is prone to occur in cementing, the requirement of horizontal well and staged fracturing for cement sheath is very strict, and the casing accessories are easy to fail in long cementing section. Relevant technical measures were also discussed here: (1) oil-cleaning preflush and multi-stage flushing process were adopted to effectively rinse the residual oil film on the interface and improve the cleaning efficiency of oil-based drilling fluid; (2) new casing centralizers developed for horizontal wells effectively reduced the friction of string run-in and keep the casing at borehole center; (3) the formation pressure was balanced in cementing by improving formation loading capacity and optimizing fluid column structure; (4) ductile materials were selected to improve the impact resistance of cement sheath and meet the cement performance requirement of shale gas horizontal well staged fracturing; (5) high-performance casing accessories were developed to ensure the construction safety in long cementing section of a horizontal well. The above technical measures have been applied in four shale gas horizontal wells in the pilot area and good cementing results have been achieved with a once-cementing success rate of 100% and a cementing quality excellence rate of 100%.