准噶尔盆地腹部断裂控油的物理模拟实验及其成藏意义

Experimental Simulation of Faults Controlling Oil Migration and Accumulation in the Central Part of Junggar Basin and Its Significance for Petroleum Geology

根据准噶尔盆地腹部地区二维和三维地震断裂构造样式解释、深浅层断裂生长指数和活动速率计算及声发射各主要构造运动期最大主应力值测试,结合盆地区域构造演化与油气成藏等研究成果,研究了盆地腹部地区断裂系统的形成演化、基本特征及其控油模式,并转化为实验模型,模拟了单一相(油相)连续、稳态流体运动条件下,深、浅两套断裂输导体系中石油的运移和聚集过程.结果表明盆地腹部地区受周缘板块的相互碰撞产生的挤压和走滑构造作用及多期次构造运动的影响,断裂发育,纵向上明显存在深、浅层两套不同性质的断裂系统,深层为基底卷入式压扭性逆冲断裂系统,浅层为盖层滑脱型张扭性正断层系统,其分别形成于海西运动中晚期和燕山运动早中期等强烈构造活动时期;高渗透性断裂带的确是油气快速运移的优势通道,盆地腹部地区深、浅层断层均是石油向上运移的主要输导体,断裂带渗透率大小决定着石油运移的方向和路径.在断层带顶部存在盖层封闭的条件下,石油在断层带中的运移呈不均匀地向上运动,断层带中含油饱和度自上而下增加,在向下增加的过程,石油倾向于在区域性盖层之下储层物性好的砂层中运移,而且是优先进入断裂上盘渗透率较大的砂层中,随着断裂带含油饱和度的不断地增加和断裂上盘储层物性好的砂层中进油量不断增多,进行侧向运移,最终聚集成藏,尔后再进入断裂下盘相应的砂层中,进油量较少;而物性较差的砂层中很少有石油进入.该实验结果得到了盆地腹部地区断裂两侧储层流体地球化学分析测试数据的佐证,对深化断裂输导体系下石油运移聚集成藏的理论认识与指导该地区的油气勘探实践均具有重要意义.

Based on the studies on the faults system in the central part of Junggar basin such as the 2D and 3D seismic faults structural style interpretation,deep and shallow layer fault growth index,fault activity rate calculation,and maximum principle stress test in various tectonic events analyzed from acoustic emission data,as well as study on the regional structural evolution and hydrocarbon migration and accumulation,the faults system formation,evolution,basic characteristics and hydrocarbon-controlling model are studied through experiments,which simulate continuous,stable and single phase hydrocarbon （oil phase） migration and accumulation process,respectively in deep and shallow faults system. Results show that central part of Junggar basin experienced compression and strike-slip resulted from collision by Peripheral plates,leading to well-developed faults. There occur two types of faults system in vertical with different property in the deep and shallow layers. The deep one is basement-involved thrust-type pressure-shear fault system; the shallow one is seal detachment transtension normal fault system,respectively formed in the middle-late Hercynian and early-middle Yanshan. High permeable fault belt is truly hydrocarbon predominant migration pathway. Deep and shallow fault system in the central part of Junggar basin is main pathways for hydrocarbon migration. The permeability of fault belts determines the direction and pathway of hydrocarbon migration. With the seal from the top of fault system,hydrocarbon moves up heterogeneously within the fault,with oil saturation increasing downward. Hydrocarbon tends to migrate within the reservoir with good prosperity under regional seal,and enters prior reservoir with high permeability in the upper wall of fault. With the hydrocarbon saturation within fault and hydrocarbon volume increasing in the upper hand of fault,hydrocarbon flows horizontally and accumulates somewhere,and then goes into lower wall of fault with small amount of oil accumulation,thus almost no oil enters the poor prosperity reservoir. This experiment result proves to be correct by the fluid geochemical analytical data of both sides of the fault,which is significant for understanding the oil migration and accumulation in the fault system in the central part of Junggar basin,and is useful for guiding oil exploration and development.