Evaluation Of Source Rocks In Qinshui Basin And Zuoquan Block

Organic matter is the material base of hydrocarbon generation for source rocks.This paper focus on the comprehensive evaluation of source rock in sedimentary,stratigraphic sequence, geochemical characteristics and so on by data collection andtesting of samples collected in the study area.Through analyzing columnar maps of single wells in study area combining withthe former research results, the author summarized the sedimentary andpalaeogeographic characters of Qinshui basin. The results show: there are sandstone,siltstone mudstone, allite, carbonatite and coal bed to form the6lithofacies and21facies types. Carbonatite continental shelf-barrier-lagoon delta depositional systemdevelops here in the Qinshui basin. Multiple sedimentary facies as tidal flat facies,lagoonal facies, mud continental shelf facies, carbonatite continental shelf facies,delta plain facies and delta front facies are developed. Belts that are rich in coal ofTaiyuan group lie in the northern subaqueous delta plain area and southern barrier bararea of the basin, the interdistributary embayment area in the northern part of Shanxigroup is also an important part of source rocks.Three Class-3sequences are divided and they are SS₁, SS₂and SS₃whichcorrespond to Benxi group, the middle and upper part of Taiyuan group and Shanxigroup. Three sets of high quality transgressive system tract source rocks aredeveloped in Carboniferous and Permian formations in study area which correspondto the condensed seams of SS₁, SS₂and SS₃and they are mainly composed ofmudstone and limestone. Source rocks deposited in the upper part of Benxi groupwhich are lagoon deposition have the best quality.Mudstone and limestone samples in Zuoquan block in the eastern part of Qinshuibasin are collected. Rock-Eval, organic carbon determination, chloroform bitumen Acontent analysis, carbon isotope analysis, sedimentary rock vitrinite reflectancedetermination and kerogen maceral and type determination tests are proceeded onthese samples. With the tested geochemistry data, the source rocks are evaluated inthree aspects which are organic matter abundance, organic matter type and organicmatter maturity. The TOC content is relatively high in the carboniferous coal,mudstone and limestone in the study area. Source rocks are mainly Ⅱ₂-Ⅲ kerogenwhich are high in geothermal evolution degree and enter postmature stage. They mainly generate gaseous hydrocarbon and are good gas source rocks.The study on sedimentary facies, sequence stratigraphy characteristics andgeochemistry characteristics of Qinshui basin shows that high quality source rocksdevelop in the study area. Coal, mudstone and limestone are very good gas sourcerocks. Particularly the coal and mudstone are widely developed and large in thicknessand so it has high development potential.