Numerical Simulation Study On The Controlling Factors Of Muddy Delta Sedimentation Of Damoguaihe Formation In Wubei Sub Sag Of Wuerxun Depression

As an important oil-gas depositional system in the world,Delta has always been the focus of previous geological research,but for many years,the study of delta is mainly coarse-grained deposition,in recent years,it gradually began to study the delta of fine-grained deposition,but at present,there is still a lack of overall understanding of fine-grained delta deposition.The Damoguaihe Formation in Hailaer basin shows obvious sedimentary characteristics of the muddy Delta.Therefore,based on the previous studies,this paper studies the sedimentary process of the Damoguaihe Formation in the Wubei sub-sag of the Wuerxun depression in Hailaer Basin through numerical simulation,establishes the dynamic evolution process of the muddy Delta sedimentation of the Damoguaihe Formation,and analyzes the influence of different control factors on its sedimentation.It provides a new way of thinking and research means for more accurate characterization of muddy Delta,theoretically complements and improves the understanding of the characteristics and classification system of muddy Delta in sedimentology,and provides guidance for oil-gas exploration and development.In the research process,in the isochronous sequence stratigraphic framework established by the predecessors,according to the high-resolution seismic data,we trace the isochronous accretion units of different periods and deltas,and identify five periods of precursors in the Damoguaihe Formation of Wubei sub sag of Wuerxun depression,which are distributed in sequence in the form of lobed oblique basin boundary.Through the plane distribution map of sand/land ratio in the study area,it is known that the area with low sand/land ratio is the most widely distributed in the muddy Delta area.According to previous research data,determine the top and bottom strata age(126ma-131ma)of the Damoguaihe Formation,determine the thickness of each sand formation of the Damoguaihe Formation in combination with logging data,core data and seismic data,and estimate the strata age of each sand formation of the Damoguaihe Formation Based on the assumption that the sedimentation rate of each sand formation is certain.The paleo thickness of each sand formation of the Damoguaihe Formation is restoredby decompressing and correcting the formation,and the initial base water depth and lake level change curve of the Damoguaihe Formation are determined.On the basis of the above geological model,using the dionisos numerical deposition simulation platform,this paper analyzes the sedimentary control factors of the muddy Delta in the study area.By controlling a single variable,the main control factors of the muddy Delta,such as hydrodynamic conditions,sediment supply rate and source sand content,are studied.The results show that:(1)It is one of the important factors for the formation of muddy Delta that fine-grained material flows into the river with high load and low density for a long time and low energy from the gentle provenance outlet;(2)the provenance supply of fine-grained sediment is an important factor for the formation of muddy Delta.Under the same provenance supply,the lower the content of sandstone,the easier it is to form mud;(3)The results show that when the sand content of provenance is fixed,when the supply rate of provenance increases greatly,but there is no corresponding increase of accommodation space and current drive,the muddy sediment is difficult to input into the basin,and the muddy delta is not developed at this time;(4)the wave action takes away the sandstone in the muddy delta precursor and transforms it,and deposits in the center of the lake basin again,which affects the development of the muddy Delta Education.Generally speaking,the muddy delta is formed in a stable environment with low energy and sufficient supply of fine materials.The sedimentary numerical simulation technology can reappear the sedimentary process of the argillaceous triangle well,which can not only directly reflect the development and evolution characteristics of the sedimentary body,but also provide relevant quantitative data for geological research.It can be seen that as a new technology,it has important significance for the future sedimentological research and is an important tool for the theoretical research of sedimentology from qualitative to quantitative.