深层致密碎屑岩储层超压成因及其对储层质量的影响——以松辽盆地长岭断陷龙凤山次凹营城组—沙河子组为例

Genesis of overpressure in deep tight clastic rock reservoirs and its effect on reservoir quality:Case study of Longfengshan sub-sag in Changling Fault Depression,Songliao Basin

深层致密砂岩气是近些年来油气勘探的热点,明确深层致密碎屑岩储层超压的成因机制对于深层油气勘探具有重要意义。以松辽盆地长岭断陷龙凤山次凹营城组—沙河子组致密碎屑岩储层为研究对象,针对超压成因认识不清、对储层质量的影响研究匮乏等问题,利用铸体薄片、常规物性测试、测井超压成因判别及包裹体古压力恢复等方法,对研究区营城组—沙河子组超压成因及其对致密碎屑岩储层质量的影响进行了分析。结果表明,龙凤山次凹营城组—沙河子组超压主要是由生烃增压作用产生。古压力恢复结果表明,2期油气充注时期,营城组都存在明显的超压,说明成藏期存在由生烃增压作用产生的超压。超压控制微裂缝的产生,未被充填的微裂缝增加了储层的连通性,改善了储层的渗透率。

Deep tight sandstone gas is a hot spot in oil and gas exploration in recent years,and it is of great significance to clarify the genetic mechanism of overpressure in deep tight clastic rock reservoirs for deep oil and gas exploration.Taking the tight clastic rock reservoirs in the Yingcheng Formation-Shahezi Formation of the Longfengshan sub-sag in the Changling Fault Depression of Songliao Basin as the research object,in view of the unclear understanding of the causes of overpressure and the lack of research on its impact on reservoir quality,using the methods of casting thin section,scanning electron microscope,well logging overpressure identification and inclusion paleo-pressure recovery,the formation of overpressure in Yingcheng-Shahezi formations and its influence on tight clastic rock reservoirs are studied.The results show that the overpressure of the Yingcheng-Shahezi formations in the Longfengshan sub-sag is mainly caused by the hydrocarbon-generation pressurization.The paleo-pressure recovery results show that there was obvious overpressure in the Yingcheng Formation during the two periods of oil and gas charging,indicating that there was overpressure caused by hydrocarbon-generating pressurization during the accumulation period.The overpressure controls the episodic hydrocarbon expulsion process,which makes the micro-fractures open in stages in the reservoir,and the unclosed micro-fractures increase the connectivity of the reservoir and improve the permeability of the reservoir.