稠油油藏直井侧钻重力火驱开发效果的数值模拟研究

Numerical simulation study on development effect of gravity fire flooding with vertical well sidetracking in heavy oil reservoirs

火烧油层作为接替蒸汽吞吐后的稠油开发方式,在厚层稠油油藏中常面临纵向波及效率低、易发生窜槽型燃烧等诸多问题。针对该类油藏的特点及开发历程,提出一种利用已有的蒸汽吞吐开发井网,对采油直井开窗侧钻水平段,变平面火驱为重力火驱的方法。从油藏地质因素和开发工程因素2方面考虑,分析了不同因素对直井侧钻重力火驱开采效果的影响,进一步研究了该方法的内在增产机理,并采用多元线性回归方程建立了采收率与主控因素之间的评价模型。结果表明,直井侧钻重力火驱对于厚层稠油油藏的采收率提高幅度达42%;直井侧钻长度约为井距的1/2时可获得较好的开采效果;建立的采收率评价模型与数值模拟得到的结果吻合度达到85%以上,能够为矿场转换开采方式时机及中长远规划提供一定的指导。

As an alternative for steam stimulation in heavy oil reservoirs,in-situ combustion often faces many problems in thick heavy oil reservoirs,such as low vertical sweep efficiency and channeling combustion.In view of the characteristics and development history of this type of reservoirs,the existing development well pattern based on steam stimulation was used to sidetrack the horizontal section of the vertical oil production wells,and the plane fire flooding was changed to gravi⁃ty fire flooding.Considering the geological and engineering conditions in the reservoirs,the influence of different factors on the development effect of gravity fire flooding with vertical well sidetracking was analyzed.In addition,the internal stimula⁃tion mechanism of this method was studied,and the evaluation model between the recovery factor and the main controlling factors was built with the multiple linear regression equation.The results show that the gravity fire flooding with vertical well sidetracking improves the recovery factor of thick heavy oil reservoirs by 42%.When the sidetracking length of the ver⁃tical well is about 1/2 of the well spacing,efficient production can be obtained.Moreover,the evaluation model of recovery factors agrees with the numerical simulation result by more than 85%,guiding the timing of converting production modes and medium-and long-term planning for the field.