微生物碳酸盐岩“三因素”控储地质认识和分布规律

“Three-factor” driven microbial carbonate reservoirs and their distribution

沈安江 胡安平 张杰 王小芳 王慧

Anjiang Shen Anping Hu Jie Zhang Xiaofang Wang Hui Wang

微生物碳酸盐岩是非常重要的油气储层，针对叠层石和凝块石碳酸盐岩比其他类型微生物碳酸盐岩和非微生物碳酸盐岩具有优质储层发育潜力这一科学问题，通过现代微生物碳酸盐沉积特征和现代盐湖碳酸盐沉积特征研究、微生物有机质早期低温降解和晚期热解生酸模拟实验、早期沉淀和交代白云石成因模拟实验，揭示了微生物碳酸盐岩因沉积物和沉积环境的特殊性，储层成因也有其特殊性，提出了“三因素”控储地质认识。①与其他类型微生物碳酸盐岩和非微生物碳酸盐岩相比，叠层石和凝块石碳酸盐岩具有更高的初始孔隙度和微生物有机质丰度，为储层发育奠定了物质基础；②微生物有机质早期低温降解和晚期热解生酸使初始孔隙在沉积后得以保存和进一步扩溶，这是叠层石和凝块石碳酸盐岩储层发育的关键；③早期白云石化有利于孔隙的保存，碳酸盐岩-膏盐岩体系微生物碳酸盐沉积易于发育早期沉淀和交代两类低温白云石，这是叠层石和凝块石白云岩储层主要发育于碳酸盐岩-膏盐岩沉积体系中的原因。这些认识为微生物碳酸盐岩储层分布预测提供了依据，也揭示了微生物碳酸盐岩储层比非微生物碳酸盐岩储层具有更佳的储层发育潜力。碳酸盐岩-膏盐岩沉积体系叠层石和凝块石发育相带是微生物碳酸盐岩储层有利分布区。

Microbial carbonates are very important hydrocarbon reservoirs. Stromatolite and thrombolite carbonates are commonly suggested to be better hydrocarbon reservoirs than other microbial and no-microbial carbonates. To check the truth of the suggestion， this study characterizes some modern microbial deposits and salt lake deposits， and performs simulated experiments of early degradation and buried pyrolysis of microbial organic matter， and genesis of dolomites by early precipitation and replacement. The results confirm the suggestion and reveal the uniqueness of microbial carbonate reservoirs with their special sediments and depositional setting. Three factors that control the formation of the reservoir are also proposed. （1） Compared with other microbial and no-microbial carbonates， stromatolite and thrombolite carbonates contain more original pores and microbial organic matter and therefore have a better material basis for becoming hydrocarbon reservoirs. （2） The production of organic acid by early degradation and later pyrolysis of microbial organic matter helps preserving and enhancing the original porosity， serving as a key factor for the development of stromatolite and thrombolite carbonate reservoirs. （3） Early dolomitization favors the preservation of pre-burial porosity and two types of low-temperature dolomitization （early deposition and replacement） tend to occur in carbonate-evaporite sedimentary sequences， which result in the development of stromatolite and thrombolite reservoirs in these sequences. The understanding is of great significance to the prediction of distribution of microbial carbonate reservoirs， based on which stromatolite and thrombolite zones are suggested to be promising hydrocarbon reservoirs in carbonate-evaporite sedimentary sequences.

10.11743/ogg20220308