RPN-0085复杂地层高压气井固井技术

A cementing technology for Gas Well RPN-0085 of high pressure in complex strata

RPN-0085井是委内瑞拉ANACO油气田EL ROBLE区块的一口气井。三开?311.2 mm井眼,油基钻井液密度1.48g/cm^3,自上而下钻遇多套高压气层和漏失层,钻井液安全密度窗口窄,多次发生严重井漏和气侵,边堵漏、边压井完成三开进尺,下入?244.5 mm技术套管3 127.13 m。套管到底开泵循环发生严重气侵,出现溢流,低排量压井,节流循环13周,钻井液密度逐渐调整到1.51 g/cm^3,建立脆弱平衡,但井下开始出现漏失迹象。针对又溢又漏的井下复杂情况,固井采用防漏、堵漏、改善水泥界面胶结强度的硅酸钠固井前置液,双凝双密度机体抗侵防气窜水泥浆体系及低排量施工和关闭井口环空候凝等系列措施,完成固井施工作业。固井检测水泥浆返至设计高度,封固质量优质,满足气井封固要求。

Well PN-0085 is one gas well which is located at Block EL ROBLE,in ANACO Oil and Gas Field,Venezuela.In the third section of■311.2 mm borehole,the density of oil-based drilling fluid is 1.48 g/cm3,and the safe density window of drilling fluid is narrow.During the drilling of this section,multiple sets of high-pressure gas reservoirs and leakage zones were dilled from top to bottom,and serious leakage and overflow happened frequently.As a result,the drilling of the third section was completed by carrying out plugging and killing simultaneously.Then,■244.5 mm intermediate casing was run to the depth of 3 127.13 m.During the circulation after the casing was run to the bottom,serious gas invasion and overflow happened.In this situation,well killing of low displacement was carried out and after 13 cycles of circulation with choke,the density of drilling fluid was adjusted to 1.51 g/cm3 and the fragile balance was established,but the tendency of mud loss occurred in the borehole.Considering the complicated borehole situation that overflow and leakage coexisted,a series of measures were taken to complete the well cementing operation,such as taking sodium silicate as the cementing prepad to prevent and control leakage and improve the interface bond strength,applying dual-cementing,dual-density,anti-gas channeling and invasion cement slurry system,conducting low displacement operation,and waiting on cement with the wellhead annulus closed,etc.It is shown from the cementing inspection results that the top of cement slurry reaches the designed height and the cementing quality is good,satisfying the cementing requirements of gas wells.