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鄂尔多斯地区奥陶系马家沟群中部发育一套厚层块状白云岩。在西部地区定边至鄂托克旗一带 ,这套块状白云岩连续厚度达数百米。定探 1井揭示的最大厚度为 431m。自西向东 ,白云岩体由厚变薄 ,并与石灰岩呈指状交织。这套块状白云岩由粗粉晶—细晶白云石组成 ,斑状结构发育。常见云斑的边界为缝合线 ,这表明斑状白云石化明显受缝合线控制。白云岩有序度平均值为 0 .85 ,CaCO3 摩尔含量平均为 5 0 .6 5 g/mol。δ13 C的平均值为 0 .6‰ (PDB) ,δ18O的平均值为 - 7.4‰ (PDB)。主体细晶白云石中液态包体常见 ,最低均一温度为 10 4℃ ,包体成分中含有大量的有机成分CH4 和无机成分H2 S。上述特征表明 ,这套白云岩是由深埋藏白云岩化作用形成的 ,它显示出良好的储集性能 ,是重要的后备储集岩。
A set of massive massive dolomite developed in Ordovician Majiagou Group in Ordos. In the western region Dingbian to Etuoke Banner area, the block of dolomite continuous thickness of several hundred meters. The maximum thickness revealed by Well Ding 1 was 431 m. From west to east, the dolomite body is thinned by thickness and intertwined with limestone. This massive dolomite consists of coarse-grained crystalline dolomite and macular structure. The common border of clouds is suture, indicating that the macular dolomitization is clearly dominated by sutures. The average order degree of dolomite is 0.85, and the average molar content of CaCO3 is 50.65 g / mol. The average of δ13C is 0.6 ‰ (PDB) and the average of δ18O is -7.4 ‰ (PDB). The main liquid crystal inclusions in fine crystalline dolomite are common, with the lowest homogenization temperature of 10 4 ℃. The inclusion contains a large amount of CH4 and H2S as the organic component. The above characteristics indicate that this dolomite is formed by deep-burial dolomitization, which shows good reservoir properties and is an important reserve reservoir.