南襄盆地泌阳凹陷与南阳凹陷油气地质特征类比及勘探启示

Comparison in petroleum geology between Biyang Depression and Nanyang Depression in Nanxiang Basin and its exploration significance

泌阳凹陷和南阳凹陷均属于南襄盆地次级构造单元,两者被唐河低凸起分隔,有效勘探面积相近,但凹陷资源量、已探明地质储量、石油天然气产量差异很大,油气分布具不均衡性。以两个凹陷的地震、钻井、测录井、地球化学资料为基础,立足于已有的勘探地质认识,从大地构造、含油气盆地要素分析、石油地质学的角度深入分析了两凹陷的相似性和差异性。研究结果表明,两凹陷在大地构造背景、构造演化阶段、凹陷平面形态、地层系统等方面具相似性。两凹陷的差异性主要表现在基底性质、边界断裂特征、沉降特征、地温特征、烃源岩特征、沉积体系、储集层物性、生储盖配置、圈闭特征、油气成藏期次及成藏模式10个方面。其中,基底性质和凹陷地质结构差异导致的油气成藏要素和成藏作用不同是油气分布不均衡性的决定因素。油气地质特征类比表明,南阳凹陷勘探程度相对较低,只要借鉴泌阳凹陷的成功勘探经验,创新地质认识,配套勘探关键技术,开展多领域、多层次、多油藏类型的立体勘探,仍具有较大的勘探潜力。

Biyang Depression and Nanyang Depression are secondary structural units of Nanxiang Basin.They are separated by Tanghe low uplift and have similar effective exploration areas.However,the resources,proven geological reserves and oil productions of the two depressions are quite different.Based on the seismic,drilling,logging,geochemical data and current exploration knowledge of the two depressions,we compared their similarities and differences from the prospective of geotectonics,basin analysis and petroleum geology.We have found they share the following points:geotectonic setting,tectonic evolution stages,depression plane modality and stratigraphic systems.However,they are different more remarkably in basement properties,boundary fault characteristics,subsidence characteristics,geothermal characteristics,source rock characteristics,sedimentary system,reservoir physical properties,source-reservoir-seal rock associations,trap conditions,petroleum accumulation mechanisms and preservation patterns.Among these aspects,the overwhelming important factors for controlling the oil and gas distributions are the basement properties and geological framework that control the accumulation factors and effects.The analogy of petroleum geological characteristics shows that the exploration degree in Nanyang Depression is relatively low.Our understanding of the successful exploration experience of Biyang Depression,our geological knowledge,and key exploration technologies,and multi-domain,multi-level,and multi-reservoir type stereoscopic exploration,suggests that the depression still have great exploration potential.