Abstract: Fault-controlled carbonate fracture-cavity reservoirs are developed in the Shunbei area of Tarim Basin. Due to the impact of multi-stage large-scale tectonic movements in the strike-slip fault zone, the fault-controlled reservoirs have complex internal structure and extremely strong heterogeneity. However, there is still no targeted modeling approach, which brings difficulties for oil reservoir development. The paper is a case study of Shunbei No. 4 fault zone for example. Different reservoir levels were divided according to the tectonic levels, and the targeted modeling approach was adopted to merge the models at different levels, so as to obtain a 3D geological model of Shunbei No. 4 fault zone. The results show that the study area mainly develops the fault-controlled fracture-cavity reservoirs controlled by large strike-slip fault zones, which are divided in terms of development levels, including five stages of strike-slip fault zone, fault-controlled body, fault-controlled body-cavelikebody-disordered body, internal filling in fault-controlled body and cavelike body, as well as micro fracture, and the higher levels can restrain and control the lower ones. The strike-slip fault zone has a wide range of influence, so it is difficult to define its boundary, and its main product is fault-controlled body. As the main reservoir space, fault-controlled body is composed of three parts, i.e., fracture body, cavelike body and disordered body, and the fault-controlled body can be identified by characterizing the three parts separately. For fracture body, cavelike body and disordered body, the scale is far beyond 25m, indicating a higher identification accuracy as compared with the earthquake technique; on the seismic section, they demonstrate the characteristics of linearly weak reflection, beaded reflection and messy reflection, and can be characterized by structure tensor, coherent energy gradient and seismic variance attribute data, respectively. The appropriate threshold is determined by the combination of well and seismic data, and the truncated thresholding is achieved by deterministic modeling approach, so as to establish the contour model of fracture body, cavelike body and disordered body. With regard to the development mode of the grille cluster in fracture body and cavelike body, a 3D model of the inner grille cluster structure was established level by level by means of the improved object-based modeling approach under the constraints of fracture body and cavelike contour models. In both fracture body and cavelike body, micro fractures with varying scale and density can be found. On this basis, an improved discrete fracture network simulation method was adopted to establish a micro fracture network model of the conjugated and bending fractures that conform to the actual morphology of field outcrops. The models at different levels are further merged by priority to get the 3D geological model of Shunbei No.4 fracture zone. The verification results show that the error between the oil and gas reserves predicted based on the geological model and the reserves analyzed dynamically is 6.54 %, and that for the numerically simulated cumulative oil production and pressure fitting is within 10 %.

Key words: strike-slip fault zone, fault-controlled body, 3D geological modeling, Shunbei No.4 fault zone, Tarim Basin

摘要： 塔里木盆地顺北地区发育断控型碳酸盐岩缝洞储集体,受多期次大型走滑断裂带构造运动影响,断控体储层内部结构复杂,非均质性极强,尚无针对性建模方法,给油藏开发带来困难。以顺北4号断裂带为例,根据发育构造级次划分不同的储层级次,针对不同的层级,采取针对性的建模方法,将不同层级模型进行融合,得到顺北4号断裂带三维地质模型。研究结果表明,研究区为受大型走滑断裂带控制的断控型缝洞储集体,从发育层次上可以划分为走滑断裂带、断控体、断裂体-类洞穴-杂乱体、断裂体-类洞穴内部充填以及微裂缝共5个层级,高层级对低层级具有约束和控制作用。对于走滑断裂带,其波及影响范围较大,难以确定其边界,其主要产物为断控体,断控体作为主要储集空间,由断裂体、类洞穴与杂乱体3部分构成,分别对三者进行表征,完成断控体的识别。对于断裂体、类洞穴以及杂乱体,其规模远超25 m,大于地震可识别精度,在地震剖面上分别呈现出线性弱反射、串珠状反射以及杂乱反射特征,分别采取结构张量、相干能量梯度以及方差地震属性体对其进行表征,以井震结合的方式确定合适的阈值,使用确定性建模方法进行阈值截断,建立断裂体、类洞穴以及杂乱体轮廓模型。针对断裂体与类洞穴内部栅簇发育模式,以断裂体与类洞穴轮廓模型为约束,采取改进的基于目标的建模方法逐层建立内部栅簇结构三维模型。在断裂体与类洞穴内部,发育规模与密度不等的微裂缝,采取改进的离散裂缝网络模拟方法,建立包含共轭裂缝、弯曲裂缝等符合野外露头中实际形态的微裂缝网络模型。将不同层级的模型按照优先级融合,得到顺北4号断裂带三维地质模型。检验结果表明,基于地质模型预测的油气储量与动态分析储量误差为6.54 %,数值模拟累积产油量、压力拟合误差在10 % 以内。

关键词: 走滑断裂带, 断控体, 三维地质建模, 顺北4号断裂带, 塔里木盆地