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Organic matter (OM) and carbonate are the important organic and inorganic components, respectively, in the shales of the upper fourth member of the Eocene Shahejie Formation, Dongying Depression, Eastern China. Their enrichment affects the hydrocarbon generation capacity and reservoir development of shales. The development mechanism of sequence stratigraphy and the influence of sequence stratigraphy on OM enrichment and carbonate deposition are investigated in this study. Based on the petrological, mineralogical, and geochemical analyses, a third-order sequence is recognized, including the lowstand systems tract (LST), transgressive systems tract (TST), and highstand systems tract (HST). The total organic carbon (TOC) content is 0.11–9.05 wt% (average 2.2 wt%), and the carbonate content is 3–95 wt% (average 51 wt%). Organic matter and carbonate are enriched in TST and gradually reduced in HST and LST. The decrease in the relative lake level in LST results in the deposition of abundant siltstone, leading to both poor OM preservation and carbonate precipitation. The rapid rise in the relative lake level in TST may be triggered by marine transgression, promoting OM enrichment in terms of both production and preservation. Seawater input brought abundant Ca2+ and Mg2+, which facilitated the precipitation of carbonates. The enrichment of OM and carbonate improves the capacity of hydrocarbon generation and reservoir performance of shales in the TST. The decrease in the relative lake level in HST causes a slight increase in the terrigenous clastic content, which, on the one hand, accelerates the sedimentation rate and OM deposition and, on the other hand, reduces carbonate precipitation. This study not only explains the differential distribution of OM and carbonate but also helps to improve the accuracy of the evaluation of shale oil sweet spots. [ABSTRACT FROM AUTHOR]

Water production from unconventional reservoirs especially shale reservoirs has always been considered as the major challenges for petroleum industries that needs special requirements and facilities to treat the flow-back water and reinject to the reservoirs. The objective of this paper is to statistically measure the provided freshwater from treated water that is produced from reused water. The treated water is provided from different processes such as hydraulic fracturing, chemical enhanced oil recovery methods (such as polymer, surfactant, and foam flooding that are the main important techniques in recovery processes) from eight wells in Bangestan field in South of Iran. Moreover, photofenton-flotation separation methods are used in this field to treat the produced water from different processes. As a result, saving water percentage in the studied field for hydraulic fracturing processes is about 82% and therefore, the required fresh water is about 18%. Moreover, saving water percentage in the studied field for chemical recovery techniques is about 70% and therefore, the required fresh water is about 29%. The findings of this study can help for better understanding of the required fresh water for 1000 inhabitants can be saved through this system. [ABSTRACT FROM AUTHOR]