259 / 2019-06-30 23:11:26

Sedimentary Simulation of Large Area Sandstone Sedimentation Simulation in Lake Basins Under Multisource Supply

Key words: sedimentary simulation;large-area sandstone; formation mechanism；genetic model

China's oil and gas resources are mainly distributed in the continental lake basin , in which large area connected sandstone is an excellent reservoir. Using the simulation experiment to visually observe the sedimentation process and results, and the formation mechanism and genetic model of large area sandstone distribution in the lake basin were analyzed comprehensively. Three sources were designed to simulate river delta, gentle slope fan-delta and steep slope fan-delta with different slopes and terrains. Six rounds of experiments were carried out to represent six deposition periods, and each period set different experimental conditions. The evolution process of large area sandstone deposition was reproduced in the experimental device by controlling the main parameters such as the settlement of movable floor, the height of lake surface, the sand content and the flow of water. The experimental phenomena reveal the formation mechanism from various aspects. It is found that the open lake basin makes it easier for coarse clasts to enrichment and form a larger thickness ratio of sandstone to formation ;A large area of sand body is more developed in shallow river deltas. Different system tract cause multi-stages sand body to form superimposition on the plane. The interaction between sedimentary systems enlarges the sand body contiguous area. Adequate supply of provenance is a good material guarantee; the combination of different water flows controls and reforms the distribution of sand body. The experimental results show that tectonic subsidence, original landform, slope of delta front and change of lake level are the main controlling factors affecting the formation, development and evolution of large area sandstone. According to the comprehensive study, there are two main modes for the formation of large area sandstone in the experiment, namely, the genetic model of multi-stages sediments superposition large area sandstone in low accommodation space and the model of late transformation of sediments in high accommodation space.