摘要
酸性气藏水平井完井方式优选与井壁稳定性密切相关,而井壁稳定性则受地应力、岩石力学参数和井眼轨迹等约束。以Drucker-Prager准则为屈服判据,利用等效塑性应变判别井壁稳定性,模拟了酸化前后、地应力衰竭前后和不同生产压差下原地应力对沿不同方向延伸的井眼井壁稳定的影响。结果表明:川东北海相储层段岩石力学强度较高,生产过程中井壁稳定性较好;随着生产压差逐渐升高,井壁岩石的等效塑性应变量逐渐增加,但变形量相对较小;酸化和地层压力衰减后,井壁出砂可能性显著增强。考虑到酸性气田的特点:当井眼轨迹延伸方向与水平主应力方向一致时,采用裸眼完井;当井眼轨迹延伸方向与水平主应力夹角小于、等于30°时,可以采用裸眼完井,但必须严格控制生产压差;夹角大于30°时,采用套管固井射孔完井。研究成果在普光气田6口水平井中得到很好的应用。
The design of the appropriate completion technique for a horizontal wellbore in sour gas field is dependent on borehole stability,which is constrained by in-situ stress,rock mechanical parameters and well trajectory.It is feasible to recommend the appropriate completion method for sour gas fields in the northeast Sichuan based on the relationship between in-situ stress and well trajectory.A predictive model was established,which useed the Drucker-Prage criterion and equivalent plastic strain theory.Influence of in-situ stress on horizontal borehole stability with different trajectories and drawdown pressures were numerically simulated,which took the effect of strength reduction and pressure depletion into consideration.Results indicated that rock strength of the northeast Sichuan marine strata is high enough to maintain borehole stability during production.With the increase of drawdown pressure,equivalent plastic strain increased gradually,but the total strain was relatively small.Gas reservoir pressure depletion and strength reduction caused by acidification played an important role in well stability and sand production tendency.Base on the study,appropriate completion method for sour gas fields in the northeast Sichuan was recommended.1）If well trajectory was coincident with direction of horizontal stress,open-hole completion was recommended,2）If angle between well trajectory and direction of horizontal stress was less than 30°,open-hole completion could be used,but drawdown pressure should be strictly controlled,and 3）if the angle was more than 30°,cased completion should be used.The results have been applied in Puguang for 6 horizontal wells.
出处
《吉林大学学报（地球科学版）》
EI
CAS
CSCD
北大核心
2011年第4期1233-1238,共6页
Journal of Jilin University：Earth Science Edition
基金
中国石化集团公司科研项目(JP08006)
中国石化中原石油勘探局博士后科研项目(JP08006博)
关键词
地应力
井壁稳定
水平井
井眼轨迹
完井
碳酸盐岩气藏
in-situ stress
borehole stability
horizontal wells
well trajectory
well completion
carbonate gas reservoir
