Physical Deposition Simulation Experiment Of Hyperpycnal Flow In Lacustrine Facies

Hyperpycnal flow is one of the important sedimentary processes in lacustrine environment.It can transport fine-grained debris and organic matter in shallow water for a long distance,which is conducive to the formation of sweet spots in shale oil.Based on the analysis of the sedimentary structure and sequence characteristics of the core in the study area of the Lucaogou Formation in the Jimsar Sag,this study determined that the relatively coarse-grained sediments in this area are mainly heavy flow deposits,and carried out physical simulation experiments to find out the dynamic mechanism of the lacustrine heavy flow.At present,although the fine-grained deposition simulation experiment has made great progress in the dynamic mechanism,there are few discussions on the formation mechanism and long-distance transport of the hyperpycnal flow,and there is a lack of relevant physical experimental devices.In order to solve this problem,this study established an annular glass sink and developed a corresponding monitoring system,which realized the experimental simulation and process monitoring of the formation of hyperpycnal flow and long-distance transportation in the laboratory.Finally,based on the background of the study area,the factors affecting the hyperpycnal flow were identified according to the experimental results.It provides technical support for fine-grained sedimentary dessert reservoir prediction.The main conclusions of the study include :(1)Hyperpycnal flow is a common natural phenomenon:a single variable experiment was carried out from four key factors affecting the formation of hyperpycnal flow : sediment composition ratio,slope,total sediment and background water depth.Through the analysis of the results,it can be seen that the formation conditions of hyperpycnal flow are not harsh and often occur in both laboratory conditions and nature.(2)In the experiment,by changing the proportion of viscous sediments,it can be found that when the content of viscous sediments increases,viscous sediments are more likely to wrap the coarse particles in the experimental fluid so that they will not settle quickly,so that the transport distance of the hyperpycnal flow is significantly longer and the duration is longer,indicating that viscous sediments are more conducive to the long-distance transport of the hyperpycnal flow..(3)The transport process of hyperpycnal flow requires a certain amount of fine particle support : Through the observation of multiple sets of experimental processes,it is found that the relative coarse particles of each group of experiments are distributed in the experimental slope section and the front section,and the relative fine particles are distributed in the middle and rear sections.The analysis shows that fine particles can support the long-distance transport of hyperpycnal flow.(4)The duration of the hyperpycnal flow is an important controlling factor for long-distance transport,that is,when the source area can provide a large amount of debris or the occurrence of periodic floods,the hyperpycnal flow will gain more power when it enters the water body,so as to carry out longer-distance transport.