普光气田绒囊修井液结合固相堵剂暂堵深部低压气层

Application of fuzzy-ball workover fluid combined with solid plugging agent to the temporary plugging of deep low-pressure gas layers in Puguang Gas Field

普光气田深部碳酸盐岩地层天然裂缝、溶洞与改造后人工裂缝结构共存,井筒液柱与地层形成压差时成为漏失通道,需实施暂堵。绒囊修井液封堵低压气层可行,但封堵大尺度通道用量过大,为此,引入固态堵剂辅助绒囊修井液降低流体用量。室内串联直径38 mm、长60 mm,含缝宽5.0 mm贯穿裂缝的人造岩心,模拟大尺度漏失通道。绒囊修井液复合质量分数0.1%~1.5%的碳酸钙颗粒和纤维,对比单一体系与复合体系注入裂缝至驱压达20 MPa时流体用量;封堵后,注入破胶液解除暂堵,重复测定清水流速恢复效果。实验结果表明,相同承压所需绒囊修井液体积随固态堵剂加量增大而下降12.3%~60.5%,与固态堵剂加量正比关系较明显;破胶后,裂缝中清水流速恢复率达98%,伤害程度较低。S-3X井、P-2Y井分别试验绒囊修井液与纤维、绒囊修井液与颗粒复合封堵技术,计算提高地层承压26 MPa、32 MPa,复合体系用量相对单一体系降幅超过30%。绒囊修井液复合固相堵剂满足普光气田深部气层大尺度漏失通道中封堵性与经济性双重要求,扩展了绒囊流体应用领域。

In Puguang Gas Field,natural fractures,vugs and hydraulic fractures coexist in the deep carbonate formation and they will become leakage channels when there is pressure difference between wellbore fluid column and formation.Therefore,temporary plugging is needed.It is feasible to apply the fuzzy-ball workover fluid to plug low-pressure gas layers,but its consumption is too high while plugging large-scaled channels.The solid plugging agent was introduced to assist fuzzy-ball workover fluid,so as to decrease the fluid consumption.In the laboratory,the artificial cores(diameter 38 mm and length 60 mm)containing through-going fractures of 5.0 mm wide are connected in series to simulate large-scaled channels.After the fuzzy-ball workover fluid was added with calcium carbonate grains and fibers with the mass fraction of 0.1%-1.5%,the fluid consumption of single system in the fracture to reach the displacement pressure of 20 MPa was compared with that of complex system.After plugging,gel breaker was injected to remove the temporary plugging and then the recovery effect of the flow velocity of clear water was measured repeatedly.It is experimentally indicated that under the same pressure,the needed volume of fuzzy-ball workover fluid decreases by 12.3%-60.5%with the increase of the dosage of solid plugging agent and it is obviously in a direct proportion to the dosage of solid plugging agent.After gel breaking,the recovery rate of the flow velocity of clear water in fractures reaches 98%,indicating lower damage degree.The complex plugging technology of fuzzy-ball workover fluid and fiber and that of fuzzy-ball workover fluid and grain were tested in Well S-3X and Well P-2Y,respectively.According to the calculation results,the formation pressure was increased by 26 MPa and 32 MPa,respectively and the consumption of complex system is 30%less than that of single system.In conclusion,the fuzzy-ball workover fluid combined with solid plugging agent can meets the plugging and economic requirements of large-scaled leakage channels in Puguang Gas Field and it expands the application fields of fuzzy-ball fluid.