断陷湖盆斜坡区油气富集理论与勘探实践——以黄骅坳陷古近系为例

Hydrocarbon enrichment theory and exploration practice in the slope of fault lake basin-a case study of Paleogene in Huanghua depression

斜坡区是中国东部断陷湖盆的主要构造单元,是渤海湾盆地重要的油气规模增储区带。在斜坡区多年综合研究和勘探实践的基础上,提出了斜坡区(大型缓坡带)具有高、中、低分异性的新认识,即高、中、低斜坡在沉降速率、沉积相序、储层物性、生烃演化、地层压力、流体性质、油气藏类型等七方面的地质差异性,形成了断陷湖盆斜坡区优势相油气富集理论,其理论内涵为:高斜坡沟槽控砂,优势运移汇聚相富集;中斜坡坡折控砂,优势构造岩性相富集;低斜坡远扇控砂,优势源储耦合相富集。以此理论为指导,开展斜坡区精细勘探与钻探部署,斜坡区地层岩性油气藏勘探取得重要勘探成果,近5年来新增三级石油地质储量超过3×10~8t,发现了4个千万吨级效益建产区块和3个亿吨级规模增储区,证实了斜坡区优势相油气富集理论在规模效益增储及高效建产区块中的重要指导意义。

Slope is a major structural unit of fault lake basin in eastern China, and also an important zone in the Bohai Bay Basin for increasing oil and gas reserves. Through years of comprehensive studies and exploration practices in slopes, it is newly proposed that the slopes （or large gentle slopes） show a high-moderate-low differentiation. To be specific, the geologic differentiation of high, moderate and low slopes in subsidence rate, sedimentary sequence, reservoir physical property, hydrocarbon generation and evolution, formation pressure, fluid property and reservoir type results in the theory of hydrocarbon enrichment in dominant facies belts in slope of fault lake basin. Essentially, in high slope, channel/trough controls sand, and oil and gas enrich in dominant migration and preservation facies. In moderate slope, slope break controls sand, and oil and gas enrich in dominant structural-lithologic facies. In low slope, distal fan controls sand, and oil and gas enrich in dominant source-reservoir coupling facies. According to this theory, fine exploration and drilling operations have been carried out in the slopes. As a result, remarkable achievements were made in stratigraphic-lithologic reservoirs in the slope zone. During the past five years, additional 3P oil reserves exceeded 3×10^8t, and four 10 million-ton class profitable productivity construction blocks and three 100 million-ton class blocks with the potential of significant reserves increased. Thus, it is demonstrated that the theory of hydrocarbon enrichment in dominant facies belts in slope plays an important role in directing the large-scale profitable reserves increase and high efficient productivity construction.