中国东部陆相断陷盆地成熟探区油气勘探新领域分析*

经过50多年勘探开发,中国东部陆相油气田均已进入勘探中后期阶段,受石油地质认识局限性和勘探技术的限制,待发现目标日趋隐蔽,油气勘探难度日益增大。针对中国东部陆相断陷盆地深层低孔渗—致密砂岩储集层评价方法的局限性、深部砂砾岩储集体成因模式问题以及基岩风化壳形成和分布的复杂性问题,作者经过近几年的探索和总结,取得以下主要研究进展: (1)基于砂岩储集层物性演化动力学原理,提出了致密砂岩储集层动态评价的新思路和新方法,指出过去评价较低的深部凹陷带低孔渗—致密砂岩体仍然具有较大的勘探潜力; (2)运用地震地层学方法,通过建立断陷盆地陡坡带斜向大型扇三角洲沉积模式,指出斜向大型扇三角洲砂砾岩是断陷盆地深层有利的储集体,可以作为下一步有利勘探方向; (3)根据基岩风化壳双层结构新模式,结合风化壳储集层改造—破坏—保存机理的动力学新模型,指出断陷盆地中低部位是最有利风化壳储集层发育带,断陷盆地缓坡内带(洼槽区)风化壳是下一步油气勘探的重要新领域。文中提出的上述3大勘探新领域不仅是对断陷盆地油气成藏模式的补充和发展,更重要的是展现出中国东部断陷盆地深层常规和非常规油气勘探领域的巨大潜力,为深化东部成熟盆地油气勘探指出了明确的方向。

Analysis of new fields for oil and gas exploration in mature exploration areas of continental rifted basins in eastern China

After more than 50 years of large-scale exploration and development,onshore oil and gas fields in eastern China have entered the middle and late stage of exploration. Due to the limitations of petroleum geological knowledge and exploration technology,the targets to be discovered are increasingly hidden,and the difficulty of oil and gas exploration is increasing day by day. In view of the limitations of evaluation methods for deep low-porosity and low-permeability tight sandstone reservoirs,the genetic models of deep glutenite reservoirs and the complexity of the formation and distribution of bedrock weathering crust in continental rifted basins in eastern China,the author has carried out systematic analysis and summary and made the following research progress: (1)Based on the dynamic principle of physical property evolution of sandstone reservoirs,a new idea and method for tight sandstone reservoirs dynamic evaluation are put forward and it is pointed out that low-porosity and permeability tight sandstones in deep sags with low evaluation in the past still have exploration potential;(2)Using the seismic stratigraphy method,the sedimentary model of oblique large fan deltas in the steep slope zone of rifted basins is established. It is suggested that the large-scale fan delta glutenites be favorable reservoirs in deep rifted basins and can be used as the next favorable exploration direction;(3)According to the new model of two-layer texture of bedrock weathering crusts and combined with the new dynamic model of weathering crust reservoir transformation-destruction-preservation mechanism,it is pointed out that the middle and low parts of the rifted basin are the most favorable zones for weathering crust reservoir development,and the inner gentle slope zone(subsag areas)of the rifted basin is also the favorable exploration zone for bedrock weathering crust reservoir. The above three new exploration fields proposed in this paper not only the supplement and develop the hydrocarbon accumulation models of rifted basins,but also show the great potential of conventional and unconventional oil and gas exploration in deep-layer rifted basins in eastern China,and point out a clear direction for deepening the oil and gas exploration in mature basins in eastern China.