鄂尔多斯盆地南部深层致密砂岩气藏成藏特点及产能主控因素

Hydrocarbon Accumulation Characteristics and Main Productivity Control Factors of Deep Tight Sandstone in the South of Ordos Basin

针对鄂尔多斯盆地南部QT1地区上古生界深层致密单一砂岩储层如何有效开发这一难题,利用石油地质学理论和油气成藏原理,结合地球化学特征,对其烃源岩分布、生烃能力,储集层特征进行系统剖析,明确了研究区成藏特征,并对产能主控因素进行研究。研究认为:区内主力烃源岩的本溪组完全缺失,减薄的太原组地层和山西组山2段煤系地层仍不失为良好的烃源岩;山西组山1段发育一套薄层砂岩储层,是纵向唯一的优势储集层段,其上石盒子组盒8砂体不发育,其间发育的细-粉砂岩和泥岩共同构成区域盖层;由于储层致密,岩性及储层含气饱和度对产能的影响最为强烈,且与苏里格气田相比,具有"含气饱和度有效下限低、单位饱和度产气量高,以中、低产量为主"的特点。以上认识指导了研究区水平井适应性评价并快速建成2亿m3/a产能。

In order to effectively develop the tight single sandstone reservoir in the deep layer of Upper Paleozoic in QT1 area of the southern Ordos Basin,the source rock distribution,hydrocarbon generation capacity,reservoir characteristics and hydrocarbon accumulation characteristics of the study area are systematically analyzed,and the main control factors of production capacity are studied.The results show that the Benxi Formation of the main source rocks in the area is completely absent,but the thinned Taiyuan Formation and the Shan2 coal bearing strata of Shanxi Formation are still good source rocks.A set of thin sandstone reservoir is developed in Shan 1 member of Shanxi formation,which is the only dominant reservoir section in vertical direction.The He 8 sand body of upper Shihezi Formation is not developed,and the fine siltstone and mudstone developed in the upper Shihezi Formation constitute the regional cap rock.Due to the tight reservoir,the lithology and gas saturation of the reservoir have the strong impact on productivity,and compared with Sulige gas field,the reservoir has the characteristics of "low effective lower limit of gas saturation,high gas production per unit saturation,mainly medium and low production".The above understanding guides the adaptability evaluation of horizontal wells in the study area and the rapid construction of production capacity of 200 million m^3/a.