塔里木盆地柯坪地区上震旦统白云岩储层特征与成因

塔里木盆地上震旦统奇格布拉克组白云岩埋藏较深、较少被钻井揭露,研究程度和勘探程度较低。通过在塔里木盆地柯坪地区震旦系露头剖面开展密集取样(1.28个/m),对奇格布拉克组白云岩的岩性、物性和储层成因机理开展了系统研究。明确了奇格布拉克组含5种主要的储集岩类:亮晶藻凝块白云岩、岩溶角砾白云岩、残余颗粒白云岩、细晶白云岩和灰质(含灰质)白云岩。落实了储层的纵、横向展布规律,其垂向上主要发育3个储层段,总厚度为65.7～95.9 m,孔隙度为5.1%～5.3%,储地比为0.42～0.53。奇格布拉克组的顶部储层段在区域上展布较为稳定,中部—底部储层段在柯坪—塔北地区分布不连续。沉积相、风化壳岩溶作用及热液溶蚀作用是优质储层形成的主控因素,裂缝对改善储层物性起建设性作用。震旦系白云岩与上覆玉尔吐斯组黑色泥页岩构成优质的源-储-盖组合,是超深层勘探潜在的新领域,而塔北地区是该领域的现实勘探区带。

Characteristics and genesis of Upper Sinian dolomite reservoirs in Keping area,Tarim Basin

The dolomite of Upper Sinian Qigebulake Formation in Tarim Basin is deeply buried and rarely exposed by drilling, and is less explored and studied. Through dense sampling (1.28 sample/m) on the Sinian outcrop profile in Keping area, Tarim Basin, the lithology, physical property and genetic mechanism of dolomite in Qigebulake Formation are systematically investigated. It is clarified that Qigebulake Formation has five major reservoir types, i.e., sparry-spongiostromata dolomite, karst-breccia domomite, residual-grain dolomite, fine crystalline dolomite and calcite dolomite. The vertical and lateral distribution regularity of reservoirs is confirmed as below: three reservoirs are mainly developed vertically with the total thickness of 65.7~95.9 m, the porosity of 5.1 % ~5.3 % and the reservoir-layer thickness ratio of 0.42~0.53. The distribution of top reservoirs in the Qigebulake Formation is relatively stable, while the mid-bottom reservoirs are distributed discontinuously from Keping to Tabei area. Sedimentary facies, weathering-crust karstification and hydrothermal dissolution are the main controlling factors for forming high-quality reservoirs. Fractures play a constructive role in the improvement of physical properties. The high-quality source-reservoir-cap assemblage consists of Sinian dolomite and the overlapping black shale in Yuertusi Formation, which is a new ultra-deep exploration field, and Tabei area is a realistic exploration area in this field.