Browsing by Author "Li, Zheng"

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    On Hydraulic Fracturing of Tight Rock
    (2021-04-19) Li, Zheng; Gates, Ian; Chen, Shengnan; Hejazi, Hossein; Zhou, Qi; Xia, Chaohui
    Hydraulic fracturing is widely used in the modern oil and gas industry for stimulating petroleum reservoirs that have low permeability (<0.1 mD) at original reservoir conditions. Without hydraulic fracturing these reservoirs are impossible to be produced commercially. In recent decades, the number of published papers on hydraulic fracturing has exploded – they span experimental work, modelling work, field work, and data mining. All aim to provide more understanding of hydraulic fracturing and to generate new insights on how to improve operations and petroleum volume produced while minimizing cost and environmental impacts. Despite the work done, rigorous understanding of hydraulic fracturing remains obscure. The research presented here studied hydraulic fracturing from multiple angles. The first part used transparent gelatin blocks to simulate a rock formation and explored hydraulic fracturing under different conditions and the results are compared with a basic model and field data. The second part used both finite element method and lab experiments to test the stress shadow effect during multistage hydraulic fracturing. The third part discussed the behavior of hydraulic fractures extension in naturally fractured reservoirs by physical and numerical simulations. The last part evaluated a dilation and unloading model which is used for simulating field hydraulic fracturing operations and make optimizations. The research reveals the following results: 1. Using transparent gelatin to conduct hydraulic fracturing laboratory experiments is feasible, where the whole cracking process at different conditions can be clearly observed and used for analysis. 2. Stress shadow effect impacts in multistage hydraulic fracturing and sets a length scale for the optimal spacing. 3. Pre-existing fractures have obvious influences on the extensions of the main hydraulic fractures. 4. Dilation-unloading fracture model is useful and efficient in numerically simulating field hydraulic fracturing operations, especially when the fracture geometry is unknown.
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    Thermal Maturation Regime Revisited in the Dongying Depression, Bohai Bay Basin, East China
    (2021-09-24) Huang, Haiping; Zhang, Hong; Li, Zheng; Liu, Mei
    To the accurate reconstruction of the hydrocarbon generation history in the Dongying Depression, Bohai Bay Basin, East China, core samples of the Eocene Shahejie Formation from 3 shale oil boreholes were analyzed using organic petrology and organic geochemistry methods. The shales are enriched in organic matter with good to excellent hydrocarbon generation potential. The maturity indicated by measured vitrinite reflectance (%Ro) falls in the range of 0.5–0.9% and increases with burial depth in each well. Changes in biomarker and aromatic hydrocarbon isomer distributions and biomarker concentrations are also unequivocally correlated with the thermal maturity of the source rocks. Maturity/depth relationships for hopanes, steranes, and aromatic hydrocarbons, constructed from core data indicate different well locations, have different thermal regimes. A systematic variability of maturity with geographical position along the depression has been illustrated, which is a dependence on the distance to the Tanlu Fault. Higher thermal gradient at the southern side of the Dongying Depression results in the same maturity level at shallower depth compared to the northern side. The significant regional thermal regime change from south to north in the Dongying Depression may exert an important impact on the timing of hydrocarbon maturation and expulsion at different locations. Different exploration strategies should be employed accordingly.