塔中北斜坡碳酸盐岩岩溶储层油气差异富集特征

塔中北斜坡下奥陶统岩溶储层基本为低孔低渗储层,主要的储集空间为溶蚀孔、洞和断裂活动产生的裂缝。储层呈现“横向连片,纵向分层”特点,优质储层主要呈层状叠合分布在不整合面下0~200m范围内的垂直渗流带和水平潜流带。岩溶储层具有大面积、多储集段含油气的特点,平面上整体表现为“西油东气,内油外气”的分布特征。鹰山组直接盖层良3—5段致密灰岩平面上具有“东厚西薄,北厚南薄”的分布特点,剖面上呈现“块状分布,横向相连,纵向叠置”的展布特征。鹰山组内部多套高阻层相互叠置,与下伏含油气层构成良好的配置关系,形成一套或多套储盖组合,控制油气的分层聚集。塔中北斜坡发育着一系列NE向左行走滑断裂,以之为边界,可以分为若干个构造区块。区块内油气水正常分异,相对高的部位聚集油气、低部位出水。块体内部油气多富集在距主干走滑断裂0.5~4.0km范围内。 

Differential enrichment of oil and gas in carbonate karst reservoir on northern slope of Tazhong uplift, Tarim Basin

The lower Ordovician karst reservoirs on the north slope of Tazhong uplift are basically those of lower porosity and small seepage, and the major reserving spaces of the reservoirs are corrosion holes and caves as well as fissures led by faults. The reservoirs are featured as horizontally continuous layered but vertically separated layered. The high quality reserving-layers are overlapped layer by layer and distributed in the vertical vadose zone and horizontal undercurrent zones between the depths of 0~200 m below the unconformity. Karst reservoirs are of the characteristics such as great in area, containing oil and gas in multiple reserving sections and appearing “oil to the west and gas to the east, oil at the center and gas along the surrounding area” in plane view as a whole. As the cap rock layer, the section 3 to section 5 dense limestone layers of the Yingshan Formation are of the characteristics as “thick in the east and north, but thin in the west and south “in plane view, and appearing “blocky distribution, linked with each other horizontally and superimposed vertically “in the section. Superimposition of multiple high-resistive layers in the Yingshan Formation well configured with the underlying oil and gas reserving layers, which leads to the formation of one or more set of reservoirs and cap-layers that controlling the enrichment of oil and gas. Several tectonic blocks can be divided with boundaries formed by a series of NE strike-slip faults that developed on the north slope of the Tazhong uplift. The oil, gas and water separate normally with each other, i.e. Gas and oil enriched at higher place and water at lower place. And the oil and gas mainly enriched within the scope of 0.5~4.0 km from the major strike-slip fault in the interior of the blocks.