Qin Jianzhong

Main Controlling Factors of Organic Matter Richness in a Permian Section of Guangyuan, Northeast Sichuan

ABSTRACT A complete Permian section in Guangyuan, Northeast Sichuan, has been investigated, to explore the variation in organic matter richness and its main controlling factors. The research results of the detailed lithological description and organic/inorganic geochemical analysis of about 325 samples indicate that a high content of total organic carbon (TOC) occurs in calcareous mudstones and laminated marls or thin-bedded limestones. In carbonate rocks, the TOC content is negatively related to the thickness of the massive beds; the thinner the bed is, the higher the TOC content is. Marine organic matter is enriched in the outer shelf and relatively shallow basin floor environments with the maximum TOC contents of 5.07% and 14.6%, respectively. The main factors that affect the quantity and quality of marine organic matter include primary productivity, depositional processes, and redox conditions during deposition and the early diagenesis stage. Three intervals of marine good quality source rocks are identified in this section; they are lower Chihsia Formation, topmost Maokou Formation, and the middle segment of the Dalong Formation. They are formed in anoxic environments, in association with high primary productivity. Among these, high productivity in the lower Chihsia interval may originate from an upwelling flow area, whereas, in the rest of the intervals, it is inferred to be related to hot fluid activity due to volcanic eruption. The results of this study suggest that good quality marine source rocks in the Permian strata offer significant hydrocarbon potential.

Geochemical characteristics of crude oils from Well Zheng-1 in the Junggar Basin, Xinjiang, China

Well Zheng-1 is located in the combined area of the central uplift and the north Tianshan piedmont depression in the Junggar Basin. Two oil-bearing beds are recognized at 4788–4797 m of the Lower Cretaceous Tugulu Formation (K1tg) and 4808.5–4812.5 m of the Lower Jurassic Sangonghe Formation (J1s). The geochemical characteristics of family composition, carbon isotopic composition, saturated hydrocarbons, sterane and terpane biomarkers and carotane of two crude oils are described in this paper. The results show that the geochemical characteristics of the two crude oils are basically similar to each other, indicating they were all derived mainly from the high mature, brine, algae-rich lake facies sediments. Oil-source correlation revealed that crude oils of the two beds were derived mainly from the source rocks of Permian and mixed by the oil derived from the source rocks of Jurassic and Triassic. This is consistent with the geological background with several sets of source rocks in the area studied.

Kinetics of the hydrocarbon generation process of marine source rocks in South China

Abstract The kinetics of hydrocarbon generation of different types of marine source rocks and planktonic algae in South China were analyzed using the Rock-Eval 6 instrument and the Optkin kinetic software. The average activity energy of marine source rocks has the characteristics of E AI E AII1 E AII2 E AIII , in the effective hydrocarbon generation period, with the kerogen transformation being from 10% to 90%. The variation of the hydrocarbon generation activity energy (Δ E ) is Δ E III >Δ E II2 >Δ E II1 >Δ E I , the hydrocarbon generation speed is V mI > V m II1 > V mII2 > V mIII , while the planktonic algae has a very low activation energy for hydrocarbon generation and can generate a great abundance of heavy oil during the immature –low mature period. According to the results of kinetic experiments on thermal simulation experiments and simulation residue samples, the kinetic hydrocarbon generation process of marine source rocks can be described by four stages: (1) heavy oil generation, where the vitrinite reflectance (Ro) is 0.3%–0.6%, and the average activation energy is about 220 kJ/mol; (2) normal oil generation, where the vitrinite reflectance is 0.6%–1.2%, and the average activation energy is approximately 250–270 kJ/mol; (3) condensate and gas generation, where the vitrinite reflectance is higher than 1.2% and the average activation energy is higher than 270 kJ/mol; and (4) gas “dead line” of kerogen, where the vitrinite reflectance is higher than 4.21% and the average activation energy is higher than 320 kJ/mol.

Discovery of lipitobiolite in suqiao area—On the discrimination of coal-generated gases and oils and their prospects

Based on the fluorescence microscopic study, organic compositional analysis and simulating experiments on core samples and cuttings in the Suqiao area, it is found that the Carboniferous-Permian coal-bearing formations have substrata rich in spore, cuticle, resin and bark. These substrata have high potential for hydrocarbons, with S1 + S2 high up to about 200, high productivity of liquid hydrocarbons (73.5 mg / g or more) and natural gases (up to 194 ml / g). The substrata are thought to be an important source for natural gases and condensates found in this area.According to biomarker compounds and carbon and hydrogen isotope data from the Suqiao natural gas-condensate field, the coal and its simulating products, characteristics of coal-generated gases and oils from a special kind of coal and their correlation methods are discussed in the paper.In terms of the geochemical conditions of formation the distribution regularities of paralic coal rich in hydrogen, the commercial prospects of Carboniferous-Permian coal-generated oils have been evaluated as well.