塔里木盆地深层走滑断裂差异变形与控储控藏特征——以顺北油气田为例

Structural styles of deep strike-slip faults in Tarim Basin and the characteristics of their control on reservoir formation and hydrocarbon accumulation: a case study of Shunbei oil and gas field

在走滑断裂精细解析的基础上,综合利用成像测井、试井和生产动态资料,探讨了顺北油气田顺北1号、顺北5号、顺北4号走滑断裂带的分段差异变形对规模储集体发育和油藏分布的控制作用。顺北地区主干走滑断裂带在几何学、运动学及活动特征方面差异显著,具有“一带一世界”的特点。其中,顺北1号断裂带在三维工区内发育9个左阶斜列展布的几何分段,分段间均发育叠接拉分段;顺北5号断裂带北段以发育压隆段—平移段为主,中段以发育平移段和分支断裂为主,南段发育“两侧地堑断面+中部主走滑断面”复合构造样式;顺北4号断裂带在三维工区内呈“S”形展布,根据走向变化可划分北段、中段和南段,具有“南北挤压、中部拉张”的分段结构特征。顺北地区走滑断裂的内部结构受断裂活动强度控制,随着活动强度增大,碳酸盐岩断裂带内部结构由发育程度较低的裂缝带逐步演化为发育程度较高的破碎角砾带-裂缝带,储集体规模也逐渐增大。顺北1号断裂带的断控规模储集体分段发育,不同分段的储集体内部结构差异明显且多不连通,同一分段的储集体相互连通,具有“一段一油藏”的特征。走滑断裂的差异变形控制了油气差异成藏,其中,受控于晚期活动“北强南弱”的差异,顺北1号断裂带北部分段井组的气油比普遍大于南部井组;顺北5号断裂带南段的中部主走滑断面直接沟通烃源岩层,具有“控储、控藏、控富”特征,而地堑断面未直接沟通烃源岩层,其钻揭的储集体与油气藏规模远小于中部主走滑断面。走滑断裂的断面具有垂向非均质性,受断面活动强度和地层能干性的控制,同一断面不同深度的靶点钻遇储集体的规模差异显著,具有“一点一规模”的特征。研究结果深化了对塔里木盆地内部走滑断裂差异变形特征的认识,可为走滑断裂断控缝洞型油气藏的勘探评价提供重要借鉴。

Based on fine analysis of strike-slip faults and comprehensive use of imaging logging, well testing and production performance data, this paper explores the control effect of the segmented differential deformation of Shunbei No.1, Shunbei No.5 and Shunbei No.4 strike-slip fault zones in Shunbei oil and gas field on the development of large-scale reservoir bodies and the distribution of oil reservoirs. There are significant differences in geometry, kinematics and activity characteristics of the main strike-slip fault zones in Shunbei area, showing the characteristic of “one zone as one world”. Specifically, there are 9 geometric segments with left-stepped diagonal distribution in the 3 D working area in Shunbei No.1 fault zone, where spliced and pull segments are developed. The north section of Shunbei No.5 fault zone is dominated by the development of uplift and translation segments, translation segments and splay fractures are mainly found in the middle section, and the south section shows the compound tectonic development pattern of “graben section on both sides and main strike-slip section in the middle”. Shunbei No.4 fault zone is distributed in an “S” shape in the 3 D working area and can be divided into north section, middle section and south section according to the strike changes. It is characterized by a segmented structure of “north-south compression and middle tension”. The internal structure of the strike-slip faults of Shunbei area is controlled by the intensity of fault activity. With the increase of activity intensity, the internal structure of carbonate fault zone has gradually evolved from a fracture zone with low development degree to the broken gravel zone and fracture zone with high development degree, and the scale of reservoir bodies is expanded accordingly. Shunbei No.1 fault zone witnesses the segmental development of the large-scale fault-controlled reservoir bodies. The internal structures of reservoir bodies in different segments are significantly different, and most of them are disconnected. The reservoir bodies in the same segment are interconnected, characterized by “one reservoir for one section”. The differential accumulation of oil and gas is controlled by the differential deformation of strike-slip fault. In detail, the gas-oil ratio of the northern segmented well group of Shunbei No.1 fault zone is generally higher than that of the southern well group, which is controlled by the difference of late activities with the characteristic of “being strong in the north and weak in the south”. The middle main strike-slip section of the southern section of Shunbei No.5 fault zone is directly communicated with source rocks, characterized with “reservoir control, accumulation control and enrichment control”. The graben section is not directly communicated with source rocks, and the scale of the drilled reservoir body and oil-gas reservoir is much smaller than that of the middle main strike-slip section. The section of strike-slip fault is vertically heterogeneous. As controlled by activity intensity of the section and competency of the formation. The scale of the targets drilled into the reservoir bodies with different depths in the same section is significantly different, which shows the characteristic of “one target for one scale”. The study will deepen the understanding on the differential deformation characteristics of the strike-slip faults in Tarim Basin and serve as an important reference for the exploration and evaluation of fracture-controlled and fractured-vuggy type reservoirs in strike-slip faults.