No abstract

Although a variety of precursors have been proposed for the formation of high molecular weight hydrocarbons (HMWHCs) in crude oil, their precise origin remains elusive. Quantitative studies of macrocrystalline wax and microcrystalline wax content of source rock extracts from the Damintun depression, Liaohe Basin, a typical high wax producing area, coupled with microscopical maceral composition studies and pyrolysis-GC analysis indicate that oil shale enriched in lacustrine biomass makes a primary contribution to wax in oil. The main precursors of high wax oil are lacustrine alginites and their amorphous matrix, which are highly aliphatic in nature and have high generative potential for HMWHCs. Wax generation efficiency could be affected by organic material abundance and maturity. The high abundance and low maturity of organic material are favorite for the formation of high quantity of wax, which declines with decreasing organic abundance and increasing thermal maturity. This suggests that wax is derived from organic-rich lacustrine biomass at early stages of maturation (R o = 0.4%-0.7%). Although the contribution of high plant cuticular wax and sporopollen cannot be ruled out, lacustrine biomass is more important in the formation of high wax oil.

In the development of conventional oil and gas projects, inter-well sandstone prediction and facies evolution provide benefit by reducing the number of wells drilled, optimizing well location and maximizing the performance of the wells. However, several particularly thorny issues were encountered in our study. Multi-bedded thin sandstone reservoirs were vertically stacked with thin coal seams. The main sedimentary facies of sandstones in areal and vertical directions varied quickly. This paper summarizes one multidisciplinary integration methodology to predict the distribution of inter- well sandstone and sedimentary facies in the South Sumatra Basin in Indonesia. To overcome the aforementioned disadvantages, this method included the following steps. First, it made use of multidisciplinary knowledge including mineralogy, sedimentology, lithology, geology, petrophysics and geophysics based on cores, well logs, and seismic data of various source data. Second, sequence strata division and correlation were studied with eleven target layers in order to describe this multi-stack reservoir. Then sedimentary facies system including braided channel and braided delta were identified based on reliable data from sedimentary structure of lithology, facies sequence, Formation Micro scanner Image data (FMI), and sedimentary characteristics of core samples such as: rock color, lithological features, mineral composition, and rock sedimentary structure. Fourth, a sandstone identification assessment standard was established to improve the precision of the reservoir prediction. Fifth, logging data and sedimentary facies were used to establish the facies log patterns. Favorable reservoir facies in strata were outlined based on the study of properties of sedimentary facies. Sixth, a four step procedure including seismic data partitioning, seismic attribute analysis, normalized seismic attributes of three compartments and sandstone thickness calculation was used to identify sandstone inter-well distribution. Seventh, multidisciplinary integration was used to understand facies and facies evolution to arrive at favourable facies and properties distribution which could then be used for geomodel building. This methodology constitutes a systematic and effective way to delineate the distribution of sandstones and sedimentary evolution for future well planning.