Jiang Fujie

Quantitative Analysis Model and Application of the Hydrocarbon Distribution Threshold

Hydrocarbon source rock obviously controls the formation and distribution of hydrocarbon reservoirs. Based on the geological concept of “source control theory”, the concept of a hydrocarbon distribution threshold was put forward. This means the maximum range for hydrocarbon controlled by the source rock conditions to migrate in the hydrocarbon basins. Three quantitative analysis models are proposed on this basis, namely the hydrocarbon accumulation probability, maximum hydrocarbon scale threshold and reserve distribution probability, which respectively refer to the probability of forming a hydrocarbon reservoir, the possible maximum scale of the hydrocarbon reservoir and the percentage of reserve distribution in a certain area within the hydrocarbon distribution threshold. Statistical analysis on 539 hydrocarbon reservoirs discovered in 28 hydrocarbon source kitchens from seven sedimentary basins and sags of eastern China shows the maximum reservoir scale possibly formed in the hydrocarbon basin, hydrocarbon accumulation probability and oil and gas reserve distribution probability are all controlled by the characteristics of the hydrocarbon source rock. Generally, as the distances from the hydrocarbon source rock center and hydrocarbon discharge boundary get longer and the hydrocarbon discharge intensity of hydrocarbon source rock center gets smaller, there will be lower probability of hydrocarbon accumulation. Corresponding quantitative models are established based on single factor statistics and multivariate analysis. Practical application in the Jiyang Depression shows that the prediction from the quantitative analysis model for the hydrocarbon distribution threshold agree well with the actual exploration results, indicating that the quantitative analysis model is likely to be a feasible tool.

Quantitative evaluation of hydrocarbon resource potential and its distribution in the Bozhong Sag and surrounding areas, Bohai Bay Basin

Abstract The Bozhong Sag is the biggest hydrocarbon rich sag in the Bohai Sea area. However, hydrocarbon resource potential and its distribution are not clear, which restricts petroleum exploration. According to the material balance principle and the hydrocarbon accumulation threshold theory, the resource potential and distribution characteristics of hydrocarbons were evaluated quantitatively with hydrocarbon accumulation systems as evaluation units. The upper and lower plays in the Bozhong Sag and surrounding areas each can be divided into six hydrocarbon accumulation systems. The total afforded accumulation hydrocarbon quantity in the Bozhong Sag and surrounding areas is 60.265×108 t of oil (43.185×108 t in the upper play, 17.080×108 t in the lower play) and 27.03×1011 m3 of gas (17.76×1011 m3 in the upper play and 9.27×1011 m3 in the lower play). The Shijiutuo (I) and Bodong (II) accumulation systems are the further exploration areas with the greatest afforded accumulation hydrocarbon quantity.

Comprehensive assessment of source rocks in the Bohai Sea area, eastern China

The Bohai Sea area, offshore of the Bohai Bay Basin, is one of the most petroliferous regions in China, with proven original oil in place of approximately 2.4 × 109 m3 (150.94 × 108 bbl) and proven original gas in place of over 5 × 1012 m3 (1.76 × 1013 ft3). Cumulative oil production is over 50 million tons (3.5 × 108 bbl). In this study, using the limited data on source rock thickness, core samples, and Rock-Eval pyrolysis along with sedimentary facies analysis, source rock characteristics of different depositional settings were identified, and the thickness, richness, organic matter type, and thermal evolution of four sets of source rocks in the Bohai Sea area— the second member of Dongying Formation (E3d2), the third member of Dongying Formation (E3d3), the first and second members of Shahejie Formation (E2s1-2), and the third member of Shahejie Formation (E2s3)—were predicted and evaluated. Subsequently, the intensity and history of hydrocarbon expulsion for different sags was systematically compared and analyzed. The greatest thickness of the four sets of source rocks in the Bohai Sea area is 400–800 m (1300–2600 ft). The average richness of the organic matter of these source rocks is 1.74%–2.87%. The E2s3 set has the highest organic matter abundance; E2s1-2 has the lowest. The organic matter of these source rocks is mainly type I and type II, but their evolutions differ. The vitrinite reflectance of E3d2 is 0.5%–1.0%, that of E3d3 is 0.7%–1.25%, that of E2s1-2 is 0.75%–1.75%, and that of E2s3 is 0.75%–2.0%. The cumulative hydrocarbon expulsion of the four sets of rocks is 4.14 × 1010 t (2.90 × 1011 bbl). The E2s1-2 set has the greatest expulsion amount: 1.75 × 1010 t (1.22 × 1011 bbl). The peak stages of hydrocarbon expulsion of the four sets of source rocks were during Neogene Minghuazhen Formation (12.2–2.0 Ma) and Neogene Guantao Formation (16.6–12.0 Ma). The Bozhong sag expelled the most hydrocarbons, followed by the Liaozhong, Qikou, and Huanghekou sags.

Evolution and movement of source kitchens and their control of oil and gas in the Tarim Cratonic Basin, China

The cratonic region of the Tarim Basin contains two main Lower Paleozoic source rocks–the Middle-Upper Ordovician and Lower-Middle Cambrian. However, few research focus on the relation between the evolution of hydrocarbon kitchens and its role in controlling oil and gas. Based on previous research results, this paper applies geochemical parameters of rock pyrolysis, hydrocarbon expulsion threshold theory and hydrocarbon-generated potential methods to identify the effectiveness of source rocks from the Lower Paleozoic while quantitatively calculating the hydrocarbon expulsion intensities and amounts for the two sets of source rocks. The above result is used to analysis the distribution of the effective hydrocarbon kitchen in each primary history stage and the controls on oil and gas. This study shows multiple phases of oil and gas generation and expulsion from the Cambrian-Ordovician source rocks with four oil-generating peaks with large-scale oil migration and accumulation. According to the changes in hydrocarbon expulsion intensity within different stages, we can elucidate the evolution of the source kitchens, because the hydrocarbon kitchens from the two sets of source rocks migrated in time and space, and there are multiple hydrocarbon expulsion centers. Based on the concept of the oil/gas threshold distribution model, the relation between the quantitative characterization of the hydrocarbon kitchen controlling function, and quantitative prediction of reservoir formation probability is studied, and the result shows that oil and gas reservoirs are located in more than 50% probability of controlling area. However, different periods and different layers of stacked hydrocarbon kitchen is complex and causing the main mixing of oil and gas. All these hydrocarbon expulsion centers had control over the distribution of oil and gas in the basin. From a macro and quantitative point of view, this discovery will provide certain guide for oil and gas exploration.