鄂尔多斯麻黄山西区中生界过剩压力与油气关系

通过泥岩压实研究,结合油气分布,探讨鄂尔多斯盆地麻黄山西区中生界过剩压力与油气关系.研究表明,麻黄山西区中生界过剩压力平面上分布于东部稳定带和中央凹陷带,剖面上主要发育于长7段和延7段.油源断裂和较深的下切古河谷作为油气运移通道,起泄压汇源作用,使得延长组烃源岩生成的油气在延安组高效成藏;延安组区域过剩压力带增强了区域盖层的封盖能力,阻止油气向上运移或散失,使油气在其下圈闭中聚集成藏;小断层和裂缝系统对延<,7>段区域过剩压力带有一定的泄压作用,这也是目前东部稳定带延安组区域过剩压力带之上发现少量油气的原因.麻黄山西区中生界在东部稳定带发育与过剩压力有关的下组合、中组合,上组合3种油气分布模式;而中央凹陷带和西部断裂带发育与过剩压力有关的中组合油气分布模式.

Relations of overpressure and hydrocarbons in the Mesozoic of western Mahuangshan, Ordos Basin

The mudstone compaction research, in combination with hydrocarbon distribution, reveals that the Mesozoic overpressure in western Mahuangshan is horizontally distributed in the eastern stable belt and the central depression belt, vertically mainly in the Chang 7 and Yan 7 members in western Mahuangshan. Oil source faults and deeply undercut river valleys act as migration pathways for the discharge and accumulation of oil and gas in the Yan'an Formation. The Yan'an Formation regional overpressure belt strengthens the sealing ability of the regional cap rock, preventing upward migration or dissipation of the oil and gas, and the oil and gas can only accumulate below the overpressure area. Minor faults and the crack system have a certain decompression function to the Yan'an Formation overpressure area, and this is the reason why some oil is currently discovered above the overpressure's region of the Yan'an Formation in the eastern stable belt. Three patterns of oil and gas distribution associated with overpressure are developed in the Mesozoic in the eastern stable belt; they are lower combination, middle combination and upper combination. The middle combination pattern is developed in the central depression belt and western fracture belt.