Characteristics Of The Soluble Organic Matter And Sedimentary Organic Facies Of Deep Source Rocks In The Dongying Depression

Dongying depression, which lies in the southeast of Jiyang depression of Bohai basin, is a Meso-cenozonic downfault lake basin after complex tectonic movements on the palaeozoic ancient landform. Heterogeneity is widly distributed in this area. At present, oil and gas explorations are concentrated on the middle-shallow layer. Along with the increasing demand for resources, the exploration of deep oil and gas resources has become a new aspect of petroleum resourece exploration.Samples are collected from Feng 8,Fengshen 1 and Fengshen 2 wells.By application of advanced technique analysis of organic geochemistry,including:Total organic carbon content,Extraction of soluble organic matter,Group composition of soluble organic matter,GC and GC-MS of saturated hydrocarbon,Thermal pyrolysis experiment,Palynofacies and Grain size analysis of organic matter,characteristics of organic matters and differences of depositonal environment and preservative conditions of deep source-rock in Dongying deppresion were described in detail.It was indicated that:(1) From viewpoint of organic richness of source-rocks,most of them are relatively high,and the organic matter types are good as well.Based on the maturity,organic matter richness,organic type of source-rocks,following order have been propsed:Es4shang>Es4xia>Ek.(2) Combined with the characteristic of rich in gyprock in deep source-rocks in Dongying depression, based on comparison of the potential hydrocarbon generation S1+S2 and palynofacies and grain size of organic particales, three sedimentary organic facies were divided: reducing deep-moderate depth lacustrine sedimentary organic facies; highly reduced salt lake sedimentary organic facies; weak reducing alluvial fan sedimentary organic facies.Among these facies, the first is the best.(3) Further study on the soluble organic matter in different facies, including content and component of chloroform extraction and the variation of parameters, indicated that the type of the source-rocks and its depositonal environment are important factors to the potential hydrocarbon generation of the source-rocks.(4) Differences of content and composition of soluble organic matters between whole rock and clay-sized sediments show that soluble organic matter is the mainly substance combined with the clay size sediments.Moreover, in the group composition analysis, aromatic hydrocarbon and nonhydrocarbone are dominant in the extraction.(5) Based on the analysis of normal alkane,isoprenoid,sterane,hopanoid,oleanane and other biomarkers,the origin of the organic matter and its dipositional environment were studied synthetically.It was indicated that primary substance of the organic matter is the determinative factor of the variation of the biomarkers. It can be used to identify the evolutional process and the difference of their dipositional environment if the primary organic matter were similar.(6) According to these parameters right in different strata,it can be seen that biomarker can be used as an effective indicator to divide diversity sedimentary organic facies,but multiple factors affect the changes of biomarker should be pay attention.