东方1-1气田浅层大位移水平井钻井液优化与实践

东方1-1气田在垂深为1 350 m左右的大位移水平井钻井过程中，表层乐东组、莺歌海组一段地层极易出泥球；水平段储层莺歌海组二段钻进摩阻扭矩大，且存在压力衰竭，极易发生井漏；储层埋深浅，地层成岩性差，井壁易失稳。针对以上钻井难题，经过多年摸索与实践，在非储层段改变以往钻井液作业模式，探索性地使用海水聚合物体系，保证非储层段泥岩充分水化；在储层段引入纳米可变形封堵剂PF-Greenseal优化无固相钻井液屏蔽暂堵性能，同时配合使用成膜封堵剂PF-LPF及高效润滑剂PF-Greenlube，成功解决了泥球、井漏、摩阻扭矩大、井壁失稳等难题，形成了一套东方1-1气田浅层大位移水平井钻井液作业模式。现场3口调整井应用结果表明，非储层段钻进机械钻速由41~64 m/h提高到85 m/h左右，同时可降低50%钻井液成本；储层段井壁稳定，井径扩大率低于3%，扭矩低，储层保护效果好，3口井测试表皮因数接近0。研究结果可为类似油气田钻井作业提供钻井液技术参考。

Optimization and application of drilling fluid in the shallow extended-reach horizontal well in Dongfang 1-1 Gasfield

When the extended-reach horizontal well with vertical depth of 1 350 m is drilled in Dongfang 1-1 Gasfield, mud balls tend to occur in the surface layer (i.e., Ledong Formation and Yinggehai Formation). During the drilling of the horizontal section in the second Member of Yinggehai Formation, the torque and drag is high and the pressure is depleted, so the mud is lost very easily. Besides, the reservoir is shallow with poor diagenetic property, so the borehole tends to be instable. To deal with these drilling difficulties, a series of exploration and practice have been conducted for many years. The previous operation mode of drilling fluid in non-reservoir intervals is transformed and sea-water polymer system is exploratorily used to ensure the sufficient hydration of mudstone in non-reservoir intervals. Nano-scale deformable blocking agent PF-Greenseal is introduced into reservoirs to optimize the shielding-temporary blocking property of solid free drilling fluids, and combined with film blocking agent PF-LPF and efficient lubricant PF-Greenlube, the following drilling difficulties are solved successfully, such as mud ball, circulation loss, high torque and drag and borehole instability, and a set of drilling fluid operation mode for the shallow extended-reach horizontal well in Dongfang 1-1 Gasfield is established. This operation model is applied on site in 3 adjustment wells. It is shown that the rate of penetration (ROP) in non-reservoir intervals increases to 85 m/h from 41-64 m/h, and the cost of drilling fluid is reduced by 50%. Furthermore, the borehole in reservoirs is stable with hole enlargement ratio less than 3% and low torque. In addition, reservoir protection effect is good and the skin factor of the three wells is close to 0. The research results can be used as the technical reference of drilling fluid for the drilling operation in similar oil and gas fields.