克拉苏构造带盐下超深层储层裂缝组合模式及分布规律

Fracture Combination Patterns and Distribution of Ultra-deep Reservoirs beneath Salt in the Kelasu Structural Belt

克拉苏构造带盐下超深层储层属于裂缝性低孔砂岩储层,构造裂缝普遍发育,分布复杂且对单井产量影响较大。目前针对该地区储层裂缝的研究已投入大量的工作,主要体现在裂缝的描述、表征和预测等方面,但由于该地区地震资料分辨率低、岩心资料少、成像测井多解性强,裂缝的研究受到一定程度的限制,生产中仅应用了裂缝密度、开度等统计数据。笔者综合野外露头、岩心和测井等资料,从裂缝组合的角度出发,系统开展了该地区储层裂缝及其组合特征研究。发现构造裂缝存在主次之分,主裂缝规模相对较大,一般垂直于地层,多为张性或张剪性,次级裂缝一般是主裂缝的伴生缝。裂缝之间存在多种接触关系,主要表现为"T"、"λ"、"y"、"τ"字等形状。依据裂缝之间的排列接触关系,建立了该地区储层裂缝四种组合模式,即"平行状"、"扫帚状"、"调节状"、"雁列状"。结合各裂缝组合成因的差异和断背斜形成过程中的构造演化过程,划分了裂缝组合平面三类成因区,即调节成因区、褶皱成因区、断裂成因区,与之对应的是高产井部署的一类区、二类区、三类区。

The ultra-deep reservoirs beneath salt in the Kelasu structural belt belong to low porosity and fractured sandstone reservoir.Tectonic fractures are common in this area and show a complex distribution pattern. These widely distributed tectonic fractures have large influence on single-well production of Kelasu structural belt. At present, research on reservoir fracture in this area is mainly focused on description, characterization, and prediction of fractures. However, due to low resolution of seismic data, limited core data and uncertainties in interpretation of images of well logging, the study of is limited. Only some statistical data such as fracture density and fracture opening are applied in the process of hydrocarbon exploration. Outcrop, core, and well logging data were used. In this study,research on reservoir fracture and combinations of fractures is carried out in this area. It is found that there are primary and secondary cracks. The scale of main cracks is larger than that of the secondary cracks. The primary cracks are generally perpendicular to the strata,and are mostly tension cracks or tension-shear cracks. The secondary cracks are generally associated the main cracks. There are many different contacts between the cracks, mainly in'T','λ','V','y', and'τ'shapes. According to the distribution of contacts between cracks, four combination modes of reservoir cracks have been established in this area including'parallel mode','broom like mode','adjust mode','echelon mode'. Together with the tectonic process of the formation of faulted anticline and the difference between crack combinations, three types of genetic regions of crack combination have been identified, i.e., are tectonically transitional region, folding-related area, and fault formation area, corresponding to the first, second, and third category of high yield wells,respectively.