塔里木盆地克深气田现今地应力场特征

Characteristic of current in-situ stress field in Keshen gas field, Tarim Basin

利用钻井诱导缝走向及井壁坍塌方位对克深气田现今地应力方位进行判断,并通过测井资料计算关键井现今地应力的数值。在此基础上,通过确定岩石力学参数并建立有限元模型,对克深气田现今地应力场进行数值模拟,并分析气田开发过程中地应力的变化及其对气井产能的影响。研究结果表明:克深气田现今水平最大主应力在西部为北北西向,向东部渐变为北北东向。水平最大主应力在气田中部表现为低值,向东西两侧呈条带状增加,水平最小主应力自北向南减小,垂向主应力与构造形态有较好的相关性,在背斜高点处为低值区。在气田开发过程中,地层压力的下降使总地应力随之呈线性下降,而地层有效地应力线性增加,导致储层裂缝开度降低,使孔渗性变差,从而影响气井产能,因此,在克深气田的开发过程中,应采取一定的储层保护措施,以保证气井的高产与稳产。

By referring to the strike of drilling inducing fracture and direction of hole-wall collapsing, the direction of current in-situ stress of Keshen gas field was judged, and the value of current stress was calculated by logging data. Based on the above, the horizontal distribution of current in-situ stress field was analyzed by numerical simulation with confirming rock mechanical parameters and building finite element model. Meanwhile, changes of total in-situ stress and efficient in-situ stress in exploitation process and its effect on well productivity were analyzed. The result shows that the current horizontal maximum principal stress is NNE on east while it is NNW on west and shows low value in the middle while increases to both east and west direction. Horizontal minimum principal stress decreases from north to south, and vertical principal stress has well relativity, which means it shows low value on top of anticline. In exploitation process, total in-situ stress drops linearly and efficient in-situ stress increases linearly with the decrease of formation pressure,which might lead to the reducing of reservoir fracture aperture, porosity, and permeability and thus well productivity. Therefore, reservoir protecting measures should be taken in exploitation process to stable productivity of gas wells.