河坝飞仙关气藏储层应力敏感性及其对产能的影响

河坝飞仙关气藏是一个裂缝孔隙型异常高压气藏,地层压力系数高达2.3。试采过程中,气井产能下降明显,表现出一定的应力敏感。通过对河坝飞仙关气藏储层岩石渗透率应力敏感、压差对渗透率应力敏感影响、渗透率可恢复性等室内岩心试验研究,结果表明:河坝飞仙关气藏储层渗透率敏感性强,渗透率损害率高达60%;渗透率永久性变形率较大,可恢复程度低;压差对渗透率敏感影响大,压差越大,渗透率敏感性越强,永久变形率越大。结合现场生产分析表明:应力敏感对河坝飞仙关气藏开发的影响大,气井产能下降快,地层压力降到20MPa时,产能下降了66%;对于河坝异常高压气藏开发,确立合理生产压差,减缓应力敏感对储层渗透率及气藏产能的损害,确保气藏在合理生产压差及合理产量下生产十分必要。

Gas reservoir stress sensitivity and its effect on productivity in Feixianguan of Heba block

Gas reservoir in Feixianguan of Heba block belongs to a fracture-pore-type reservoir with abnormally high pres sure and the formation pressure coefficient is high up to 2.3.During producing process,the productivity dropped quickly,showing some stress sensitivity.Through coring laboratory analysis,such as rock stress sensitivity analysis,differential pressure effect on permeability stress sensitivity analysis and permeability recoverability analysis,the permeability of the gas reservoir is found to be characterized by strong sensitivi ty and a high degree of formation.Besides that,the permea-bility damage rate is high up to 60%.In combination with practical production analysis,the result indicates stress sen sitivity has a good effect on reservoir development and when the formation pressure drops to 20 MPa,the productivity will decrease 66%.Therefore,it is necessary to select a rea sonable drawdown pressure so as to slow down the damage of stress sensitivity to reservoir permeability and reservoir productivity,and finally ensure the gas reservoir is under reasonable drawdown pressure and reasonable production status.