银额盆地哈日凹陷白垩系云质泥岩气藏特征与成藏条件

Characteristics and accumulation conditions of Cretaceous dolomitic mudstone gas reservoir in Hari Sag,Yin'e Basin

近年来,银额盆地哈日凹陷白垩系云质泥岩的天然气勘探获得了重大发现。为了研究泥岩气藏的储层特征、成藏条件、气藏分布规律及其控制因素,开展了构造背景分析、岩石学特征研究、物性分析、烃源岩有机地化测试和封盖条件评价等,并利用地震资料进行有利勘探区预测。结果表明:(1)哈日凹陷为一经历了断-坳运动单断箕状凹陷,在持续沉降的构造背景下形成了泥岩气藏;(2)烃源岩主要为大套富含有机质且处于过成熟阶段的含灰或灰质泥岩、含云或云质泥岩。部分泥岩储集层中发育多种类型的微孔隙和微裂缝,为天然气的成藏提供了良好的储集空间;(3)稳定的构造背景和良好的封盖条件有效阻止了油气的散失,使得大量天然气在源内聚集成藏,天然气储量约为243.2亿m^3,单断箕状断陷的深凹带为泥岩气藏勘探的有利区。该研究成果对银额盆地泥岩气藏勘探具有指导作用。

In recent years,great discoveries of natural gas exploration have been made in Cretaceous dolomitic mudstone in Hari Sag. For revealing the reservoir characteristics,accumulation conditions,gas reservoir distribution and its controlling factors of mudstone gas reservoirs,the studies on tectonic setting,petrologic features,physical properties,organic geochemical test and sealing conditions evaluation of source rock were carried out,and favorable exploration areas were predicted by using seismic data. The results show that(1)Hari Sag was a half graben-like basin which experienced multiple tectonic activities. On the background of continuous subsidence,mudstone reservoir formed.(2)Source rocks were composed of lime mudstone and dolomitic mudstone with abundant over-maturity organic materials. There were many types of micropore and microfracture in part of mudstone reservoir,which supplied good reservoir space for natural gas accumulation.(3)Stable tectonic setting and excellent sealing conditions prevented the loss of oil and gas effectively. Abundant natural gas was accumulated in the source and its reserve was approximately 243.2×10~8 m^3. The deep region of half graben-like basin was the favorable area for the mudstone gas reservoir exploration. The research results have important implications for exploration of mudstone gas reservoirs in Yin’e Basin.