鄂尔多斯含硫气井绒囊压井流体暂堵能力测试

Fuzzy-ball plugging fluid technology for sulfur-containing low-pressure gas well in Ordos

鄂尔多斯下古奥陶系低压气井测试环节地层漏失严重,利用绒囊修井液封堵结构抗温耐酸性突出,暂堵地层后为气井测试提供安全稳定井筒环境。室内利用直径38 mm、长60 mm岩心柱塞中高0.5 mm贯穿型不规则裂缝模拟地层漏失通道,模拟温度110~150℃,连续注入绒囊修井液至驱压达20 MPa后,反向注入H_2S含量0.1%的酸性气体,测定48 h内驱压衰减幅度小于5%,表明高温酸性环境下承压结构稳定。实验测定绒囊流体返排后天然灰岩基质与裂缝渗透率恢复率87.15%、96.52%,储层保护效果良好。现场应用绒囊修井液于S-2X井、S-4Y井套管腐蚀检测暂堵,两口气井H_2S含量约1 000 mg/m^3,反循环泵入绒囊修井液64 m^3、68 m^3后,井口12h检测无气体,暂堵成功。补充清水33 m^3、20 m^3后见液,套管腐蚀检测作业顺利,气井产气效果恢复快速。该暂堵工艺为鄂尔多斯盆地下古奥套系气井安全测试作业提供了技术支撑。

In Ordos Basin,severe lost circulation was observed during workover operation in high-temperature sulfur-containing low-pressure gas wells in Lower Paleo-Ordovician.The temporary plugging structure formed by fuzzy-ball workover fluid entering the formation leakage channel exhibits considerable high-temperature and acid resistance,it provides a safer and more stable wellbore condition for gas well testing after the formation has been temporarily plugged.In laboratory experiment,formation fluid loss channel was simulated by an irregular-shaped fracture with an aperture of 0.5 mm through a core sample with a diameter of 38 mm and a length of 60 mm.The test temperature was 110~150℃.The temporary plugging structure was formed after continuous injecting fuzzy-ball workover fluid until the driving pressure reached 20 MPa.Then the acid gas containing 0.1%H 2S was injected backward.The driving pressure reduction was less than 5%in 48 h,indicating that the pressure bearing structure was stable under high temperature and acidic environment.The permeability recovery rate after fuzzy-ball fluid flowback were 87.15%and 96.52%for natural sandstone matrix and the fracture,respectively,indicating satisfactory formation protecting effect.Field test of fuzzy-ball workover fluid was carried out in S-2X well and S-4Y well in the central and western Ordos Basin,where the H 2S content was more than 1 000 mg/m 3 for each well.No acid gas was detected at the wellhead for each well for 12 hours after 64 m 3 and 68 m 3 of fuzzy-ball workover fluid was reversely circulated through the casing annulus,implying successful plugging.The wellhead fluid was seen after the follow-up replenishment of 33 m 3 and 20 m 3 clean water.The workover project was successfully accomplished.The daily gas production rate of the gas wells recovered to the pre-operation level after production resumption.This technique provides technical support for gas well testing intervention in Lower Paleo-Ordovician of Ordos basin.