资阳东峰场地区须家河组须五段气藏产能影响因素及稳产对策

Xujiahe 5 Gas reservoir in Dongfengchang area,Ziyang,central Sichuan Basin:Productivity controls and production-stabilizing strategies

针对四川盆地资阳东峰场地区上三叠统须家河组须五段气藏试采中表现出的单井天然气产能差异大、稳产效果差等问题,综合地质、动态监测、实验分析等资料,开展了产能主控因素及递减原因分析,提出了稳产对策。研究结果表明:①气井产能主要受井型和优质储层发育程度影响,水平井产能明显高于直井,优质储层越发育,气井产能越高;②气井稳产效果较差,稳产期平均为10个月,日产气量递减指数平均为0.0017,储层有效渗透率低、供气范围有限;③气井初期高配产带来大生产压差引发储层应力敏感伤害,地露压差小易析出凝析油造成储层反凝析伤害,使储层渗透率损失,导致气井产能迅速递减;④压裂砂回流使人工裂缝导流能力下降并在近井地带堆积造成砂堵,压裂液返排困难使气井积液甚至水淹,均会导致气井停产;⑤控压开采可有效降低储层渗透率的损伤,液氮助排、优化生产管柱有利于气井排液,延缓气井产能递减。该研究成果可以为类似地区致密砂岩气藏开发技术对策制订提供参考。

During west testing,there exists large difference in single-well productivity and poor effect in stable production for gas reservoirs of the fifth member of Xujiahe Formation(Xujiahe 5 Member)in Dongfengchang area.So,the main controls on the productivity and reasons on production decline were discussed in the light of geological,dynamic monitoring and experimental data.And some countermeasures were made for stabilizing production.Results show that(i)the productivity is principally affected by both types of gas wells and extensional degree of quality reservoirs.The productivity in horizontal wells is significantly higher than that in vertical ones.The more developed the quality reservoirs,the higher the productivity;(ii)for these wells,the stabilizing effect is poor with the average stable period of 10 months,and the production decline index of 0.0017 per day on average,creating low effective permeability and finite gas supply;(iii)induced from big production pressure difference caused by high proration in the early days of development,the reservoirs feature strong stress sensitivity.Moreover,small dew-point pressure difference results that condensate oil is easy to be precipitated to cause anti condensation damage,to bringing about permeability loss,and finally the rapid productivity decline;(iv)fracturing sand’s backflow results in the decrease of the conductivity in induced fractures and these fractures accumulated near wellbore area.And it’s hard for fracturing liquid to flow back,resulting in liquid accumulation or even water flooding and well shutdown;and(v)the managed-pressure production can effectively reduce the permeability loss.And liquid nitrogen cleanup and production-string optimization are conducive to liquid drainage.As a result,the productivity decline may be put off.All results may provide important reference on technical measures made for the development of tight sandstone gas reservoirs in similar areas.