Alteration of solid bitumen by hydrothermal heating and thermochemical sulfate reduction in the Ediacaran and Cambrian dolomite reservoirs in the Central Sichuan Basin, SW China

Thermal evolution behavior of the organic matter and a ray of light on the origin of vitrinite-like maceral in the Mesoproterozoic and Lower Cambrian black shales: Insights from artificial maturation

“…For example, the pyrobitumen in the Sinian Dengying and Cambrian Longwangmiao reservoir dolomites from Sichuan Basin has a strong anisotropy and different coke structures (including mesophase) (Fig. 14), however, the insource solid bitumen/pyrobitumen in the Precambrian-Silurian shales displays a relatively low anisotropy (Gao et al, 2018;Luo et al, 2018;Yang et al, 2018;Zhang et al, 2019;Luo et al, 2020). The pyrobitumen in the reservoir carbonate rocks and in the mudstones/shales were mainly formed from the expelled oil and the retained oil, respectively (Goodarzi et al, 1993;Stasiuk, 1997;Luo et al, 2018).…”

Fluid Inclusion Evidence for Oil Charge and Cracking in the Cambrian Longwangmiao Dolomite Reservoirs of the Central Sichuan Basin, China

“…We also found in well MX39, there were some fluid inclusions including "solid bitumen+gas" (Figure 10), i.e., the result of ancient oil inclusion reset, and its synchronous aqueous is relatively lower than oil-cracking temperature. We presume the reason is as follows: there was TSR reaction (i.e., thermochemical sulfate reduction, a process that occurs at elevated temperatures (>120 °C) and involves the reaction between sulfate and hydrocarbons to produce hydrogen sulfide, elemental sulfur, calcite, carbon dioxide, and organic sulfur compounds [39, 40, [41] appearing in the Longwangmiao Formation [7,8,29], and TSR could improve the occurrence of oil cracking [42], J. E. Dahl et al [43] also once published a paper which demonstrated that TSR begins oil cracking at about 120-130 °C, so albeit the temperature was relatively lower, a small amount of oil could also begin to crack due to the TSR. The second phase of pure gas and bitumen inclusions was trapped in Middle Jurassic to Early Cretaceous.…”

“…Oil Charge and Gas Accumulation. Studies of diagenetic minerals and fabrics in the reservoir, the petrological evaluation of bitumen, fluid inclusion measurements, and U-Pb dating have been integrated as an effective proxy to temporally constrain the processes of hydrocarbon charge in the Longwangmiao Formation in the Gao-Mo area[8,[22][23][24][25][26][27][28][29]. Unfortunately, there are still several inconsistencies in the timing of hydrocarbon charge, which is partly a result of the selection of different samples and the application of different methodologies.…”

Trace and Rare Earth Element Partitioning in Organic Fractions of Mudstones during the Oil Formation

“…Dengying Formation developed a large suit of dolomite sediments, which can be subdivided into four members from bottom to top based on the enrichment degree of algae and structural characteristics: Z 2 dn 1 , Z 2 dn 2 , Z 2 dn 3 , and Z 2 dn 4 . Reservoir solid bitumens are widely developed in the Dengying dolomite in Sichuan Basin and its peripheral areas [39][40][41]. Reservoir solid bitumens in this study were collected from Z 2 dn 4 dolomites.…”