储集层非均质性对蒸汽辅助重力泄油开发效果的影响

Impact of Reservoir Heterogeneity on Ultra-Heavy Oil Development Effectby SAGD Process

在蒸汽辅助重力泄油(SAGD)开发过程中,生产效果主要取决于蒸汽腔的大小,储集层非均质性对蒸汽腔发育具有重要的影响。以克拉玛依风城油田重32井区和重37井区SAGD试验区典型非均质地质模型为基础,利用数值模拟方法详细研究了储集层渗透率、夹层物性及夹层空间分布对SAGD开发的影响。结果表明,注汽水平井上方的夹层主要影响SAGD生产阶段蒸汽的垂向上升,阻碍了蒸汽腔正常的垂向发育,迫使蒸汽腔沿夹层底部横向扩展,推迟产油峰值时间;注采井井间的夹层导致水平段动用程度低,影响循环预热效果,增加预热时间,导致热流体无法正常采出,生产效果较差。为获得较好的开发效果,SAGD水平井组应部署在水平段渗透率级差小于3.0的位置,以避开渗透率小于100 mD的夹层,确保不连续夹层距离注汽水平井上方3 m以上,注采井间夹层以及注汽井上方夹层的夹层闭合度分别小于40%和50%.

The ultra-heavy oil development effect by steam assisted gravity drainage （SAGD） process mainly depends on the size of steam chamber,which is greatly influenced by reservoir heterogeneity.Based on the typical heterogeneous geological model of Wellblock-Z32 and Wellblock-Z37 pilot areas in Fengcheng oilfield of Junggar basin,the influences of reservoir permeability,intercalation physical properties and intercalation distribution on the SAGD process was studied using numerical simulation approach.The results show that the intercalations above the horizontal gas injector mainly affect the vertical migration of steam during the production stage of SAGD,and impede the normal vertical development of the steam chamber,and lead to a lateral extension of the steam chamber along the bottom of the intercalation and postpone the peak of oil production.The intercalations between injectors and producers would cause low producing degree of the horizontal section and lower the efficiency of circulation preheating,increasing the preheating time.As a result,the hot fluid can not be recovered as expected and the production effect is poor.In order to obtain a better result,the SAGD horizontal well groups should be deployed in horizontal sections where permeability difference is less than 3.0 and avoid intercalations with a permeability less than 100 mD;moreover,the discontinuous intercalations should be more than 3.0 m away from horizontal injectors,the intercalation closures between injectors and producers should be less than 40％,and those above the gas injectors less than 50％.