鲁西地区太古界裂缝类型与发育规律

Fracture types and distribution of Archaean rocks in west Shandong,China

依据露头观测和成像测井数据,揭示鲁西地区太古界裂缝系统的成因及类型,将裂缝产状数据与区域构造背景结合分析,同时依据典型断裂-裂缝剖面的观测统计,对太古界构造裂缝的形成时期及发育规律进行剖析。结果表明:鲁西地区太古界裂缝系统主要由区域构造裂缝和局部构造裂缝组成;区域构造裂缝形成时期主要为中—新生代,其中低角度裂缝形成于印支期,高角度裂缝形成于燕山—喜山期;局部构造裂缝的发育虽不具有普遍性,但对局部地区太古界储集性能的改善意义重大;规模相近但力学性质不同的断裂对储层的改造程度和影响范围存在差异;压性断裂最好,压扭性断裂次之,张扭性断裂最差;断裂影响范围内裂缝面密度的显著增大主要表现为区域构造裂缝的加密或派生新的构造裂缝,新生裂缝通常与断裂平行或小角度斜交。

Based on outcrop observations and image logging data,the origin and types of Archaean rocks fracture were revealed in west Shandong. Integrating a large amount of measurements for fracture properties,this research focuses on the genetic type,the formation date and the characteristics of Archaean fracture systems in the region. Formation period and distribution of structural fracture were studied by drawing connection between the regional tectonic setting and the fracture occurrence inferred from observations of screened section from the typical faults and the associated fractures. The results show that the Archaean fracture system in west Shandong consists of two genetic types. One is the regional tectonic joint,which was formed in the Meso-Cenozoic era. The formation of low and high angle joint was in the Indo-Chinese epoch and the YanshanHimalayan period,respectively. The other type is local structure fracture,which is not typical but of great significance in improving the Archaean reservoir quality in some areas. Faults with similar length scale but different mechanical properties have different influences on reservoir properties： the tenso-shear faults seem to have minimal effects,the compressive faults have the maximum effects,and the compresso-shear faults are in the middle. The increase of the fracture areal density within the influenced fault mainly causes more infill of regional tectonic joints or new structure fractures,which are generally parallel to or at a small angle oblique to the fractures.