塔里木盆地寒武系白云岩构造裂缝发育特征

Development Characteristics of Structural Fractures in Cambrian Dolostone, Tarim Basin

采用加权有效裂缝面密度参数,可以反映研究层段有效裂缝的整体发育情况。基于塔里木盆地牙哈、英买力、塔中和塔东等四个地区28口井的岩心观察,对寒武系上、中、下统的白云岩构造裂缝分别进行了统计分析。结果表明:构造裂缝发育程度方面,内幕型裂缝发育区(塔中地区和塔东地区)加权裂缝平均面密度明显大于潜山型裂缝发育区(牙哈地区和英买力地区);有效裂缝发育程度方面,塔中地区和牙哈地区上寒武统加权有效裂缝平均面密度较大,反映了裂缝对白云岩储层有较好的改造作用;英买力地区中寒武统有效裂缝相对发育;塔东地区各统有效裂缝基本不发育。有效裂缝发育程度的差异,与潜山区和内幕区构造活动强度、流体活动类型及裂缝充填的差异有关。

The method of weighting areal density of effective fractures can be used to reveal the development characteristics of effective fractures in whole target strata. Based on the observation of the dolostone cores from 28 wells in Yaka, Yengimahalla, Tazhong and Tadong areas in Tarim Basin, statistics and analysis have been done respectively to the dolostone structural fractures in the Upper, Middle and Lower Cambrian strata. It is indicated that as for the development of structural fractures, the average weighting areal density of fractures in the inner buried-hill fracture zones （in Tazhong and Tadong areas） is larger than that in the buried-hill zone （in Yaka and Yengimahalla areas） . As for the development of effective fractures, the average weighting areal density of fractures is large in Upper Cambrian strata in both Tazhong area and Yaka area, which emerges preferable reformation of these fractures to dolostone reservoirs. The effective fractures are relatively developing only in Middle Cambrian strata in Yengimahalla area while are not in Upper, Middle and Lower Cambrian strata in Tadong area. It is concluded that the difference in areal density of effective fractures is closely related with local tectonic activities, fluid activities and fracture fillings in the buried-hill zone and the inner buried-hill zone.