东方13-1高温高压气田全寿命多级屏障井筒完整性设计

Design of life-cycle multi-barrier wellbore integrity in Dongfang 13-1 HTHP Gas Field

东方13-1气田目的层温度高达141℃,压力系数1.90~1.94 g/cm^3,天然气中CO_2含量14.63%~50.04%,属高温高压高含CO_2天然气藏,实际开发中极易造成固井窜槽、油套管强度下降及腐蚀失效,给井筒安全造成隐患。为此设计采用了具有防漏、防窜、防腐蚀、防应变、防温变功能的"5防"树脂水泥浆体系及油气响应型自修复水泥浆体系,实现全井段水泥封固;并提出了"尾管树脂水泥浆+尾管顶部封隔器+回接插入密封+回接管柱顶部封隔器+自修复水泥固井+树脂水泥固井"六级屏障设计技术,形成多级屏障的安全系统。现场应用结果表明,东方13-1气田各生产井?177.8 mm尾管及回接段固井质量优良,而且从投产至今,各生产井井口压力监测均未发现有环空带压问题。该套技术可以有效封固高温高压高含CO_2产层,保障从钻完井至后期开发生产整个周期过程中的井筒完整性,降低了环空带压风险。

The target layer in Dongfang 13-1 Gas Field is a natural gas reservoir with high temperature (141℃), high pressure (pressure coefficient 1.90-1.94 g/cm3) and high CO2 content (14.63%-50.04%). When it is actually developed, cementing channeling,tubing and casing strength decline and corrosion occur easily, so the wellbore safety suffers from potential danger. To solve this problem,the “five-control” (lost circulation control, channeling control, corrosion control, strain control and temperature change control) aqueousresin drilling fluid system and the petroleum/gas-response self-repairing aqueous drilling fluid system were designed, depending onwhich, the whole wellbore cementing was realized. Besides that, six-level barrier design technology (aqueous resin drilling fluid at liner+ packer at the top of liner + tieback inserted sealing + packer at the top of tieback string + self-repairing cementing + resin cementing)was proposed to provide multi-barrier safety system. Field application results show that the cementing qualities of ?177.8 mm liner andtieback sections in all production wells in Dongfang 13-1 Gas Field are satisfied. Since they were put into production, no annulus pressure has been recorded in any production well when wellhead pressure is monitored. By virtue of this technology, HTHP pay zones with high CO2 content are cemented effectively, the wellbore integrity from drilling and completion through the whole process of development and production is guaranteed and the risk of annulus pressure is mitigated.