鄂尔多斯盆地西缘延安组陆相页岩油气选区评价关键参数值的确定

SELECTION OF KEY PARAMETERS IN EVALUATING YAN'AN FORMATION CONTINENTAL SHALE OIL-GAS POTENTIALS OF WESTERN MARGIN OF ORDOS BASIN

对鄂尔多斯盆地西缘侏罗系延安组低成熟页岩样品进行热模拟实验和岩石热解实验,分析岩石热成熟度(R_o)与生烃率及热解烃率(S_2)之间的变化规律,以及热解烃量与生烃量的关系。研究表明,陆相低成熟页岩气态烃产率随R_o的升高呈线性增加,液态烃产率随R_o的升高先增加后下降。产烃率随R_o的上升呈指数增加,热解烃率随R_o上升呈指数减少。热解烃率与产烃率之间具有良好的线性负相关,产烃率在热解烃率下降的过程中呈线性增加。陆相页岩生烃演化可分为3个阶段:游离烃释放及初期热降解的未成熟阶段、热降解-热裂解的成熟阶段和热裂解的过成熟阶段。根据生烃模拟中气态烃增长率和液态烃产率突增,以及第一个生烃高峰时所对应的R_o值,确定了鄂尔多斯盆地西缘侏罗系延安组陆相页岩油气有利区和目标区的关键参数R_o和TOC的下限。

Thermal simulation and rock pyrolysis experiments of the low maturity shale samples from Jurassic Yan＇an formation of western margin of Ordos basin help find the relation between rock thermal maturity （ Ro ） and hydrocarbon production rate ＆ pyrolysis hydrocarbon rate （S2 ）, and relation between S2 and hydrocarbon production rate. Results show that gaseous hydrocarbon production rate of the low maturity continental shale increases linearly with Ro, liquid hydrocarbon production rate increases firstly and then decreases with Ro, hydrocarbon production rate increases exponentially with Ro, and S2 decreases exponentially with R,,. S2 is linearly negative with hydrocarbon production rate, which linearly rises while $2 falls. The evolution of continental shale hydrocarbon generation can be divided into three stages： immature stage with releasing free hydrocarbon and initial kerogen thermal degrading, mature stage with kerogen thermal degrading and liquid hydrocarbon thermal cracking, and over-maturity stage with gaseous hydrocarbon and liquid hydrocarbon thermal cracking. According to the gaseous hydrocarbon increment rate and an abrupt rise of liquid hydrocarbon production rate in the hydrocarbon generation simulation, and to the R. corresponding to the first hydrocarbon production peak, this paper determines the lower limit of Ro and TOC of Jurassic Yan＇an tbrmation continental shale in the favorable and target areas in the western margin of Ordos basin.