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深水底流改造砂是海相盆地重要的储集层之一。与海相盆地相比,陆相湖盆深水区是否存在大规模底流改造砂及其沉积特征、识别标志、形成机制、分布规模、外部形态、与深水重力流砂体的差异性及其油气勘探价值都值得去探索。利用松辽盆地的岩心及青海湖卫星照片资料,对上述问题进行了探讨和深入研究。陆相湖盆底流改造砂由泥质粉细砂岩和粉细砂岩组成,单层厚度为0.5~280cm;发育冲刷面和截切等底面侵蚀构造,常见的层理有交错层理、平行层理、透镜状层理及饥饿层理等。湖泊底流改造砂具有与湖相暗色泥页岩呈互层展布、细粒、发育牵引流构造和常与重力流交替出现这4个基本特征。研究表明,风驱底流对三角洲前缘和深水重力流砂体的再改造是形成深水底流改造砂的主要成因。深水底流改造砂在沉积特征、展布方向及成因机制等方面与深水重力流砂体存在显著差异。底流改造砂体在陆相盆地深水区广泛分布,厚层的底流改造砂可以形成致密油气藏,同时底流改造砂的广泛分布提高了泥页岩脆性矿物的含量,其分布区也是泥页岩油气藏勘探的甜点区。研究结果对于拓展我国陆相盆地非常规油气藏的勘探领域具有重要的意义。
Deep-water inflow reform sand is one of the important reservoirs in the marine basin. Compared with the marine basin, whether there is a large-scale underbalanced remolded sand and its sedimentary characteristics, identification mechanism, distribution mechanism, external shape, and the difference with the deep-water gravity flow sand body and its exploration value are all worthwhile To explore. Using the core of Songliao Basin and Qinghai Lake satellite photos, the above problems were discussed and further studied. The bottom sand flow of the continental lacustrine basin consists of argillaceous fine sandstone and fine siltstone, and the thickness of the single layer is 0.5-280cm. The erosion facies such as scouring surface and truncation are developed. The common bedding includes staggered bedding, parallel bedding, Stratification and hunger layering and so on. The recalcitrant lacustrine sediments of the lake have four basic characteristics: interlayered distribution of fine mud shale with lacustrine facies, the development of traction flow structures and alternation of gravity flow with each other. The research shows that the reformation of the delta front and the deep-water gravity flow sand body by the wind-driven inflow is the main reason for the formation of deep-water inflow sand. The characteristics of deep-water inflow reform sand and deep-water gravity sand body are significant differences in sedimentary characteristics, distribution direction and genetic mechanism. Bottom flow retrogressive sand bodies are widely distributed in the deep basin of the continental basin. The thick underflow stream can form tight reservoirs. At the same time, the widespread distribution of underflow stream can increase the content of shale brittle minerals. The distribution area is also shale oil and gas Tibetan exploration of the dessert area. The research results are of great significance to the exploration of unconventional reservoirs in continental basins of China.