湖相碳酸盐岩成因及其石油地质意义——以东濮凹陷沙河街组四段为例

Origin of lacustrine carbonate rocks and its significance to petroleum geology: taking fourth Member of Shahejie Formation in Dongpu Sag as an example

王义武 蒋飞虎 慕小水 王晋娟 董琳1

北京大学地球与空间科学学院，北京 100871 中国石化中原油田分公司勘探开发研究院，河南 濮阳 457001

School of Earth and Space Sciences, Peking University, Beijing 100871, China Research Institute of Exploration and Development, Zhongyuan Oilfield Company, SINOPEC, Puyang 457001, China

选取了东濮凹陷卫146井沙河街组四段，进行详细的沉积学以及地球化学特征分析。结果表明：在沙四段下亚段沉积时期，δ13C（碳13同位素）较低，湖水温度较低，化学沉积为碳酸盐岩组分的主要来源；在沙四段上亚段沉积时期，δ13C较高，湖水整体温度较高，此时碳酸盐岩组分质量分数受到湖水化学组分和生物生产力2个因素的共同控制。此外，沙四段上亚段沉积时期，由于温度相对较高，有利于生物的大量生长，生物死亡后残留在沉积物中的生物碎屑较多，在经过淡水冲蚀等后期成岩变化时，可以增加岩石孔隙度，有利于形成优质的油气储层。由于温度在地理范围内的扩展性，对于更大范围的优质储层预测也有重要意义。

In order to understand the formation mechanism of lacustrine carbonate and its significance as a reservoir in oil and gas field, the core of Well Wei-146 located in Dongpu Sag is investigated. The study interval is the Member IV of the Shahejie Formation(Es4). Based on detailed sedimentological and geochemical analysis, it suggests that in the lower part of Es4(Es4L), the carbonate composition mainly came from chemical deposition in the lake that is related to the weathering of the clastic rocks, and the temperature of the environment was relatively low. In contrast, in the upper part of the formation(Es4U), the temperature became higher, which caused the increase of primary production. Thus the formation of the Es4U carbonate is controlled by both primary productivity and water chemistry. Furthermore, because of the high productivity, the bioclasts in the Es4U sediments dramatically increased, which is prone to be dissolved during diagenetic processes, and thus raise the porosity of the rock and make an excellent reservoir. Since the factor of temperature could be applied in a broad geographical scale, our study showing high temperature during the formation of Es4U may provide guidance for further reservoir prediction in this region.

10.6056/dkyqt201805005