鄂尔多斯盆地上古生界灰岩烃源岩生烃潜力评价
Hydrocarbon Generation Potential Evaluation of Upper Paleozoic Limestone in Ordos Basin

对于鄂尔多斯盆地上古生界海陆过渡相灰岩能否生烃及生烃潜力有多大，目前研究较少.通过岩石热解、总有机碳测定、干酪根碳同位素及有机显微组分的测定实验，同时结合镜质体反射率的测定，综合评价了灰岩烃源岩，并分析了其生排烃特征.结果显示：从有机质丰度角度，本溪组为差的烃源岩，山西组为差－一般的烃源岩、太原组为一般－好的烃源岩；从有机质类型角度，本溪组为Ⅲ型，山西组以Ⅲ型为主同时混有少量Ⅱ2型，太原组为Ⅱ2-Ⅲ型；从有机质成熟度角度，本溪组处于成熟－高成熟阶段，太原组及山西组均处于高成熟阶段.根据排烃门限理论，认为Ro为1.6%时，天然气大量生成.考虑到灰岩烃源岩的特殊性、成熟度及其排烃特征，综合认为太原组灰岩可以成为天然气的有效烃源岩.
There is little research on whether hydrocarbon generation from limestone in the transitional phase of the Upper Paleozoic in the Ordos basin can be made, and on how much the hydrocarbon can be. Using rock pyrolysis, determination of TOC, carbon isotope of kerogen, organic maceral and Ro experiment, we analyzed the limestone source rocks and characteristics of hydrocarbon generation and expulsion. The results show that: (1)The source rocks from Benxi Formation, Shanxi Formation and Taiyuan Formation is poor, poor-fair, and fair-good respectively according to organic matter abundance. (2)The organic matter type of Benxi Formation, Taiyuan Formation and Shanxi Formation is Ⅲ, Ⅱ2-Ⅲ and Ⅲ mixed with a small quantity of Ⅱ2 respectively. (3) The maturity of source rocks from Benxi Formation is mature-high mature stage, and Taiyuan Formation and Shanxi Formation is high mature stage. According to hydrocarbon expulsion threshold theory, we consider large amount of natural gas generated when Ro is above 1.6%. Considering the particularity of limestone source rocks, maturity and characteristics of hydrocarbon expulsion, we comprehensively consider that the limestone of Taiyuan Formation can be the effective source rocks of natural gas