The Research Of The Prediction Of Hydrocarbon Source Rock In Manghan Depression Of Songnan Basion

Based on the analysis of structural characteristics, the paper has mainly studied on the law of source rock development in Songnan fault depressions, analyzed source rock characteristics, distribution and control factors of Manghan fault depression in Songnan Basin. It reveals the structural characteristics of prototype basin, the controlling factors of source rock development, the distribution and exhibition of high-quality source rock in Jiufotang Formation.According to the rock association, logging and electrical characteristics, based on the unity of outcrops, wells, seismic data and geochemical data, the paper determined the stratigraphic division, established standard geochemical comprehensive column according to different fault depressions, combined with the hydrocarbon source rock indicators (organic matter abundance, type and maturity). Using seismic data, combined with geology, hydrocarbon source rock evaluation results, based on the seismic labeling in fine well, the paper studied the source rock seismic facies features, set up seismic facies models of hydrocarbon source rocks of different development degrees. Thus it can forecast hydrocarbon source rock distribution characteristics. Combined with the prototype basin structural characteristics and controlling factors of source rock development, the paper studied the distribution and exhibition of high-quality source rock in Jiufotang Formation.The first condition of oil and gas accumulation in sedimentary basin is to have favorable source rocks. The basis of source rocks evaluation is to find out the distribution characteristics of source rocks. In order to solve this problem, it came out a way using seismic data to predict the distribution of source rocks, including three aspects:use sequence stratigraphic framework and system tract analysis to identify source rock section; use seismic facies analysis to determine the source rocks distribution range in the plane; use lithology analysis method and seismic velocity to predict mudstone index in source rocks, and then get the thickness of the source rocks.1Using geological analysis method, according to drilling and coring date, outcrop observation and laboratory analysis data, the paper studied the characteristics of reservoir sedimentary sequence and measured laboratory parameters, including the type of organic matter, abundance and maturity of the rock samples or cuttings.2Using geophysical logging, based on the study of key coring wells, through the establishment of the database of logging data, using the method of mathematical geology, the vertical resolution of the logging information and special response of organic matter on well log curve, the paper established hydrocarbon source rocks content model, and then calculated the value of continuous distribution of organic carbon content in source rock sections, which undoubtedly made up for the shortage of laboratory measurements and provided more accurate, reasonable parameter values for the evaluation of source rocks3Using seismic methods, well seismic combination marking accurate synthetic seismogram and calibrating the target source rock layer in the vertical direction, the paper studied the seismic facies in the place of source rocks, and established a relationship model of seismic facies and source rocks qualities. Through lateral tracking of the seismic data, we can determine the distribution of high quality source rocks accurately, which made up the logging horizontal resolution and low comparability Then use mathematical relationships, we can get the effective thickness at the macro level and achieve the purpose of predicting the spatial distribution.The study indicates that, the development degree of fault depression is mutually influenced by pervious EW fault, contemporaneous NE fault and properties of basin basement, which resulted in no clear rules in development degree and scale of depression in the spatial distribution and relative development of depressions along EW fault.Based on the combination of drilling, logging and seismic date, the paper established a model of distinguishing high-quality source rocks by using seismic and logging date. High-quality source rocks in Jiufotang Formation were continuous and concentrated reflected, of high GR, high RT and high interval transit-time in logging and separable between RT and AC in logging curve.High-quality source rocks of Jiufotang Formation in Songnan Basin were mainly distributed in the deep depression area, with a high source rock thickness. But the distribution range was relatively limited in the depression, with high organic matter content. The oil shale developed in some of depressions, with III type the prior one and source rock maturity on the low side, which became the key factors that restricted prospecting potential of Songnan fault depression.Finally, based on the source rock maturity of Jiufotang Formation, combined with source rock thickness, organic matter content, distribution scope or area size, formation depth, the paper concluded that exploration potential in Jiufotang Formation is not high. It reveals the prototype basin structural features, controlling factors of source rocks development and distribution of high-quality source rocks in Jiufotang Formation. The paper has important theoretical and practical significance in the next oil and gas exploration and clear direction in this block.