断裂活动中的瞬时流场及断裂的输导性研究:以库车前陆盆地克拉苏冲断带为例

发布时间：2018-11-14 19:40

【摘要】：活动期的开启断裂会影响地层流场的分布。如何恢复断裂活动中的瞬时流场,如何定量评价活动期断裂的输导性,依然是断裂与流体运移关系研究中的薄弱环节。尝试利用数值模拟的方法,在非均一地质模型建立的基础上,在断裂活动前初始流场与断裂活动后末流场已知的情况下,通过不断调整影响地层流场的关键参数——渗透系数,最终获得与末流场吻合的瞬时流场及断裂活动期的渗透率。以库车前陆盆地克拉苏冲断带为例,模拟结果表明,活动期断裂的顶部出现相对高气势的凸起区,流体倾向于向围岩运移,是流体的释放区;断裂的底部出现"U"字形相对低气势的下凹区,为流体的吸入区;断裂带纵向的气势梯度减小,流体垂向运移的动力减弱,但由于断裂带的高渗性,可弥补动力的不足;在如此的"泵吸"作用下,深部天然气可向断裂顶部地层运移;不同断裂的"泵吸"作用强度不同,决定了哪些断裂会成为主要的"气源断裂"及以断裂为运移通道的气藏的富集程度;克拉2气藏下伏F2-k断裂在活动期的渗透率为24.9μm2,明显高于大北1气藏下伏F3断裂的渗透率5.78×10-3μm2,是引起2个气藏富集程度差异的主要原因。
[Abstract]:The open fault during the active period will affect the distribution of the formation flow field. How to restore the instantaneous flow field in the fault activity and how to quantitatively evaluate the conductivity of the fault during the active period is still a weak link in the study of the relationship between the fault and the fluid migration. This paper attempts to use the numerical simulation method, on the basis of the establishment of heterogeneous geological model, under the condition that the initial flow field before fault activity and the final flow field after fault activity are known, the permeability coefficient, which is the key parameter that affects the formation flow field, is constantly adjusted. Finally, the transient flow field and the permeability of the fault active period are obtained, which are consistent with the final flow field. Taking the Klassou thrust belt of Kuqa Foreland Basin as an example, the simulation results show that relatively high gas uplift appears at the top of the active fault, and the fluid tends to migrate to the surrounding rock, which is the release area of the fluid. At the bottom of the fault, there is a "U" zigzag concave with relatively low gas potential, which is the suction area of the fluid, the vertical gas potential gradient of the fault zone decreases and the dynamic force of the vertical migration of the fluid weakens, but because of the high permeability of the fault zone, it can make up for the lack of the dynamic force. Under the action of pump suction, deep natural gas can be transported to the top of the fault. The different action intensity of "pump suction" of different faults determines which faults will become the main "gas source faults" and the enrichment degree of gas reservoirs with fault as the migration channel. The permeability of the underlying F2-k fault in Kela 2 gas reservoir is 24.9 渭 m ~ (2), which is obviously higher than that of the low F _ 3 fault of Da Bei _ 1 gas reservoir 5.78 脳 10 ~ (-3) 渭 m ~ (2), which is the main reason for the difference of enrichment degree between the two reservoirs.
【作者单位】：西北大学大陆动力学国家重点实验室;西北大学地质学系;
【基金】：国家自然科学基金项目(41672121) 西北大学大陆动力学国家重点实验室开放课题基金项目
【分类号】：P618.13

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