文昌气田抗170℃无固相钻井液技术

珠江口盆地文昌9-2/9-3/10-3气田珠海组水平储层段高温至165℃,且为低孔低渗透的储层。室内在对中海油常规油气田使用的无固相PRD钻井液研究的基础上,通过对抗温降滤失剂、抗温增黏剂、抗温淀粉以及防水锁剂的优选复配,并加入超细碳酸钙、聚胺抑制剂以及高温稳定剂等,开发了新型无固相钻井液体系。该体系有可抗温170℃,高温稳定性强,在150℃的页岩滚动回收率达95.3%,经系列流体污染后其渗透率恢复值大于90%,同时其形成的滤饼易破胶降解,储层保护效果及环境保护性能好,所优选的防水锁剂起泡能力低,加入2%时钻井液滤液的气-液表面张力降低到30.0 m N/m左右,油液界面张力降到5 m N/m以下,储层防水锁效果显著。现场应用表明,该钻井液能控制珠海组低孔低渗和高温层段钻遇的储层保护问题,可作为海洋低渗储层高温水平段的钻井完井液使用。

Study on Solids-free High Temperature Drilling Fluid Used in Wenchang Gas Field

Three blocks, Wenchang 9-2, Wenchang 9-3 and Wenchang 10-3, are gas fields located in the Zhujiangkou Basin. Gas reservoirs in this basin are characteristic of high temperature (165℃) and low permeability. Laboratory studies had been performed on PRD, a solids free drilling fluid used by CNOOC in oil and gas well drilling, to improve its high temperature performance. PRD was optimized with high temperature filter loss reducer, high temperature viscosifier, high temperature drilling starch, water block preventing agent, ultrafine calcium carbonate, polyamine, and high temperature stabilizer. The new formulation was stable at 170℃, and percent shale core sample recovery rate was 95.3%. Return permeability of fluid-contaminated cores was greater than 90%, while the mud cake formed on the cores was very easy to remove. The selected water block preventer, when added at a concentration of 2%, reduced the surface tension of the gas-liquid interface of mud filtrate to less than about 30.0 mN/m, and that of oil-water interface to less than 5 mN/m, a very good water block preventer for reservoir protection. This new formulation is suitable for use in offshore drilling where low permeability and high temperature reservoirs are horizontally drilled.