贺兰山汝箕沟地区及中卫探区上三叠统烃源岩初步评价?

贺兰山中卫探区是中国石化胜利油田分公司2002年8月登记的勘探新区，迄今为止，探区内还没有钻井资料，总体的勘探程度非常低。为研究中卫探区上三叠统烃源岩的生烃能力，对探区以北汝箕沟地区上三叠统露头区暗色泥岩进行了取样分析，结果表明：该泥质岩的有机碳含量为3.03%，总烃含量0.0025%；干酪根显微组分以镜质组为主，类型指数-72.5，属Ⅲ型干酪根；Ro值为0.93％，有机质热演化已达到成熟阶段。与探区以东鄂尔多斯盆地延长组、石炭系-二叠系煤系地层相比较，汝箕沟地区上三叠统泥质岩样品的有机质丰度较高，成熟度好，可作为较好的气源岩。晚三叠世时期，中卫探区和汝箕沟地区同属滨浅湖相沉积环境，中卫探区更靠近湖盆中心，为更有利的生烃沉积相带。中卫探区上三叠统烃源岩应具有较好的生气能力，应以该套烃源岩为基础，加强中卫探区内天然气的勘探。

Preliminary evaluation of the Upper Triassic source rocks in Rujigou area and Zhongwei prospecting area of Helan Mountains

The Zhongwei area of Helan Mountains is a new prospecting area that was registered by the Shengli Oilfield Company of SINOPEC in August 2002. So far, no drilling data concerning the Zhongwei prospecting area has been obtained and the exploration degree is quite low as a whole. To study the hydrocarbon-generating capability of the Upper Triassic source rocks in Zhongwei prospecting area, the Upper Triassic dark mudstones in Rujigou area in the north of Zhongwei prospecting area have been collected and analyzed. The results indicates: 1) The content of organic carbon is 3.03%, and the total HC content is 0.0025% ; 2) The kerogen maceral are mainly vitrinite, and the type of organic matter in the mudstones is type-Ⅲ kerogen whose index is -72.5. The vitrinite reflectivity of the samples is 0.93%, and the thermal evolution of the organic material has reached maturity degree. Compared with the Yanchang Formation and the Carboniferous - Permian coal measures in the Ordos Basin, the organic matter of the Upper Triassic dark mudstone samples in Rujigou area has a higher abundance and has reached a high maturity, which can become better gas source rocks. The Zhongwei prospecting area and Rujigou area was dominated by the shore-shallow lacustriine facies during the Late Triassic, and Zhongwei prospecting area is closer to the lake center, and thus the sedimentary facies is more favorable. The Upper Triassic source rocks in Zhongwei prospecting area have higher gas generating ability, and the gas exploration in this area should be strengthened on the basis of the source rock evaluation.