CAJ | 학술논문

鄂尔多斯盆地奥陶系马家沟组五段中组合中下段为该盆地天然气勘探新发现层系。主要发育膏溶孔型和晶间孔型白云岩储层，其空间分布主要受沉积环境控制。综合分析表明，中组合中下段的气源为上古生界煤型气与下古生界海相烃源气的混源气，但以煤型气为主。加里东末期，由于盆地整体抬升造成古隆起地区马家沟组五段遭受强烈剥蚀，致使其东侧中组合中下段储层与上古生界煤系烃源岩直接接触，且海退沉积旋回中的局部洼陷也能提供一定的烃源，从而构成了良好的源-储配置关系。两类白云岩储层中，由于膏溶孔或晶间孔发育，因此物性明显好于周围白云岩体，空间上可形成岩性圈闭，当上古生界煤系烃源及下古生界海相烃源运移至中组合中下段圈闭内，即可聚集成藏。整体上这种气藏具有“多层系叠合，混源成藏”的特点。
악이다사분지오도계마가구조오단중조합중하단위해분지천연기감탐신발현층계。주요발육고용공형화정간공형백운암저층，기공간분포주요수침적배경공제。종합분석표명，중조합중하단적기원위상고생계매형기여하고생계해상경원기적혼원기，단이매형기위주。가리동말기，유우분지정체태승조성고륭기지구마가구조오단조수강렬박식，치사기동측중조합중하단저층여상고생계매계경원암직접접촉，차해퇴침적선회중적국부와함야능제공일정적경원，종이구성료량호적원-저배치관계。량류백운암저층중，유우고용공혹정간공발육，인차물성명현호우주위백운암체，공간상가형성암성권폐，당상고생계매계경원급하고생계해상경원운이지중조합중하단권폐내，즉가취집성장。정체상저충기장구유“다층계첩합，혼원성장”적특점。
The Lower Ordovician Majiagou Formation can be divided into the Lower, the Middle and the Upper assemblages from the lower to the upper and the Middle Assemblage can be further divided into three sections. The Middle and Lower Sections of the Middle Assemblage are the good gas reservoirs that are discovered recently in Ordos Basin. The dolostone reservoirs with gypsum-dissolution pores and intercrystal pores are common and the spacial distribution of these dolostone reservoirs is controlled by sedimentary environment. Comprehensive analysis shows that the gas in the Middle and Lower section reservoirs is the mixed gas that derives mostly from the coal-related gas in the Upper Paleozoic source rock and less from the marine-facies gas in the Lower Paleozoic source rock. Due to uplifting of the whole Ordos Basin at the end of Caledonian movement, Majiagou Member-5 strata were subjected to intensive denudation, which led to direct contact of the Middle and Lower section reservoirs of Middle Assemblage of Majiagou Member-5 with the overlying Upper Paleozoic coal-series source rock and so a good source-reservoir relationship was set up. Owing to development of gypsum-dissolved and intercrystal pores, these dolostone reservoirs obviously are of better physical property than the surrounding dolostone bodies so that they are favorable to form lithologic traps and hydrocarbon accumulation in them as the mixed coal-related and marine-facies gases migrated into the Middle and Lower section traps from the Upper Paleozoic and Lower Paleozoic source rocks. These gas reservoirs are characteristic of multi-layer superimposition and mixed source accumulation.