Search

Gold and petroleum are also strategic resources of great importance to national security. With the increasing demand for energy, multi-energy cooperative exploration has become an inevitable trend of resource development and utilization. Petroleum and hydrothermal gold deposits may form together, with similar evolutionary trends in their formation, migration, and enrichment. Petroleum reservoirs and gold deposits are closely coupled under certain geological conditions. The solubility of gold in crude oil and its forms of occurrence are important in determining the mechanisms of interaction between gold and petroleum and in facilitating the recovery of gold from gold-bearing petroleum. In this study, the occurrence of gold in crude oil from the Linnan Depression in the Bohai Bay Basin, China, was studied using inductively coupled plasma–mass spectrometry and X-ray photoelectron spectroscopy. Concentrations of gold in crude oil from the Linpan and Shanghe oilfields averaged 44.5 ppb, which is well above the minimum concentration required for hydrothermal gold mineralization. Gold has an affinity with carbon, oxygen, and sulfur, and its concentration in crude oil is positively correlated with total acid and sulfur contents. We speculate that gold may exist in crude oil as complexes with organic acids or thiols, with crude oil thus being a transport medium for gold. [ABSTRACT FROM AUTHOR]

The origin of Precambrian dolomites has attracted research interest as a result of their association with petroleum resources. The long diagenetic history of these dolomites and multiple periods of hydrothermal activity mean that dating and identifying different periods of dolomite formation is challenging. This study focuses on dolomites in the Precambrian Dengying Formation of the Sichuan Basin, central China, and presents new petrographic, in situ laser ablation inductively coupled plasma mass spectrometry U–Pb and trace element, and Sr–C–O isotopic data to characterize three types of dolomite and constrain their age and origin. In situ U–Pb dating of type I dolomite yielded a lower intercept age of 637 ± 35 Ma. The rare earth element (REE) patterns, 87Sr/86Sr ratios (0.70827–0.70903), and δ13C VPDB (0.8‰–1.0‰) and δ18O VPDB (−1.5‰ to −1.0‰) values of type I dolomite indicate their derivation from seawater or a precursory source with seawater characteristics. Type II dolomite yielded an age of 636 ± 15 Ma and has lower ΣREE and slightly higher δ13C VPDB (1.2‰–1.5‰) and δ18O VPDB (−0.9‰ to −0.3‰) values than type I, as well as similar 87Sr/86Sr ratios and parallel REE patterns that are indicative of formation by reflux seepage dolomitization. The type III dolomite is characterized by large crystals, unique REE patterns, high 87Sr/86Sr values (0.70942–0.70975), and negative δ18O VPDB values (−6.4‰ to −3.1‰) that indicate a hydrothermal origin. The relationships between hydrothermal dolomite and bitumen indicate that the paleo-oil charging within the Dengying Formation reservoir occurred after the hydrothermal activity at 516 ± 49 Ma. The early hydrothermal activity provided space for the subsequent fluid movement, and oil and gas charging. Our integrated approach, incorporating petrographic, geochemical, isotopic, and geochronological data, constrains the ages of different dolomite phases and an oil-charging event within the Dengying Formation reservoir and provides new insights into the evolution of petroleum systems in general. • We identified three types of dolomites of Dengying Formation matching with the age of diagenesis and fluid activity. • The LA–ICP–MS in situ U–Pb dating of Dengying Formation dolomite yields a lower intercept age of 637 ± 35 Ma. • The dating results suggest an extensional event existed at 516 ± 49 Ma, and accounted for the deposition of hydrocarbon source rocks. • This study outlines potential approaches for furthering our understanding of dolomites and ancient petroleum systems. [ABSTRACT FROM AUTHOR]

In view of the miniaturization and decentralization characteristics of agricultural equipment factories in China, agricultural equipment manufacturing is well suited to the cloud manufacturing model, but there is no specific research on cloud services optimization for it. To fill the research gap, a cloud service optimization method is proposed in this paper. For the optimization model, the dynamic coefficient strategy and the reliability feedback update strategy are added to the mathematical model to strengthen the applicability of farming season. As optimization algorithm, a dynamic artificial ant-bee colony algorithm (DAABA) based on artificial ant colony algorithm and bee colony algorithm is presented. The optimal fusion evaluation strategy is used to save optimization time by reducing the useless iteration, and the iterative adjustment threshold strategy is adopted to improve the accuracy of cloud service by increasing the size of bee colony. Finally, the performance of DAABA is verified to be more superior by comparing with other algorithms. [ABSTRACT FROM AUTHOR]

A detailed correlation of Hetianhe condensates versus typical source rocks from the Tarim Basin was established. Moreover, the genetic relationship between the condensates and their associated gases was also studied based on their geochemical compositions and fluid inclusion data. Hetianhe condensates are characterized by high pristine/phytane (Pr/Ph) ratios, high relative abundances of C regular steranes, C-C triaromatic steroids, and triaromatic dinosteranes, and relatively heavy stable carbon isotopic compositions. They geochemically correlate well with the Cambrian source rocks, indicating that these condensates are derived from the Cambrian rocks. Based on several molecular maturity parameters, the condensates are recognized as being moderately to highly mature, which are too low in maturity to extensively crack into gases. The gases and condensates of the Hetianhe Field are derived from the same source rocks and the gases are from oil-cracking; however, clear evidence indicates that the gases were not cracked from their associated condensates and that the gas generation from oil-cracking did not occur in the present reservoirs. The liquid condensates produced from wellheads were likely dissolved in their associated gases underground and carried into the reservoirs by the gases. [ABSTRACT FROM AUTHOR]

• A distinct oil group was discovered in the Dongying Depression. • Related source rock of the distinct oil group has abundant bacteria/algae inputs. • Norcholestanes and triaromatic steroids are effectively used in oil classification. • This oil group has a higher abundance of nordiacholestanes than norcholestanes. • This oil group contains extremely high abundances of 4-methyltriaromatic steroids. The lower third and upper fourth members of the Eocene Shahejie Formation (lower Es3 and upper Es4) are known as two sets of effective source rocks in the Dongying Depression, Bohai Bay Basin. In this study, the saturated and aromatic steroids of 20 crude oil samples from the Dongying Depression were systematically investigated using gas chromatography–mass spectrometry (GC–MS) and GC–MS metastable reaction monitoring. Based on the distribution patterns of the steranes, norcholestanes, and triaromatic steroids, the Group I and II oils were clearly identified and shown to be derived from the lower Es3 and upper Es4 source rocks, respectively. Significantly, it was discovered that three oil samples collected from the Eocene Kongdian Formation and the Ordovician reservoirs exhibit completely different steroid and isotopic compositions from those of the Group I and II oils. These oils, as a distinct oil group (Group III), have the characteristics of abnormally high concentrations of C 29 steranes, 24-nordiacholestane, 27-nordiacholestane, C 28 triaromatic steroids, C 27 4α-methyltriaromatic steroids, and C 29 4α-methyl-24-ethyltriaromatic steroids, and low concentrations of 24-norcholestane, 27-norcholestane and triaromatic dinosteroids, and 13C depletion. Although the related source rock of Group III oils needs to be further clarified in the study area, the 13C depletion, abundant C 29 steranes, and low 24-norcholestane content may suggest greater bacteria/algae inputs (e.g., green algae rather than dinoflagellates) than both the lower Es3 and upper Es4 source rocks. Identification of the Group III oils indicates that the norcholestanes and triaromatic steroids may be more effective molecular fossils for the classification of crude oils in complicated petroleum exploration fields. [ABSTRACT FROM AUTHOR]

The Qiyugou deposit, in the Xiong’er terrane, Qinling Orogen, is an auriferous breccia pipe developed in continental collision setting. The breccia pipe exhibits variable-sized clasts and clast mixing, which are typical of fluidized breccias. Brecciation, alteration, and gold mineralization are related to granite porphyry emplaced at c. 134 Ma. However, the relationships of the CO2-rich ore-forming fluids with the tectonic setting, structural control, granite magma evolution, and hydrothermal brecciation have not been clearly discussed. New fluid inclusion data presented in this paper indicate that the formation of the Qiyugou deposit includes: (1) an early stage defined by K-feldspar-epidote-quartz-pyrite assemblage; (2) a middle stage of quartz-polymetallic sulphides; and (3) a late stage typified by quartz-carbonate±adularia. Alteration and mineralization resulted from escape of hot (>320 °C), high-salinity (>40 wt% NaCl eq.) magmatic fluid exsolved during the final stage of crystallization of the granite porphyry. Significant pressure drop from 85–90 to 20–38 MPa resulted in breccia formation and precipitation of quartz, sulphides, and gold. A vapour phase was produced at 355–403 °C due to fluid boiling, and then was cooled and condensed under near-critical conditions to a moderately saline, warm liquid. Aqueous-carbonic inclusions were formed by trapping of heterogeneous fluids unmixed from the original H2O-CO2-NaCl fluid. Late magmatic-hydrothermal fluid mixed with meteoric fluid, and was cooled and diluted to produce lukewarm, low-salinity fluid that precipitated clear quartz and calcite with little or no mineralization. Our review of the literature suggests that the brecciation and mineralization likely coincided with sinistral transtensive faulting during 140–120 Ma. Therefore, synthesis of the foregoing geochemical information with pertinent geological information from the literature lead us to propose that fluidization and seismic pumping were important in the breccia formation and associated gold mineralization at Qiyugou. [ABSTRACT FROM AUTHOR]

Free oils and inclusion oils were extracted from the third member of the Eocene Shahejie Formation (Es3) reservoir sandstones of the wells Chun 51 and Liang 28 in the Dongying Depression, China, and then analyzed by gas chromatography–mass spectrometry (GC–MS). Results show that biomarker distribution characteristics of the free oils and their associated inclusion oils are similar in each Es3 reservoir sandstones of the two wells, but the distributions of Pr/Ph ratio, gammacerane, hopane series and C 27 –C 29 steranes in well Chun 51 oils are strikingly different from those of well Liang 28 oils. However, the C 29 sterane ββ/(ββ + αα), Ts/(Ts + Tm) and C 31 hopane 22S/(22S + 22R) ratios of inclusion oils are higher than those of related free oils in all the samples, this may indicate that maturity indicators decreased after reaching the maximum and relatively high mature oils were trapped in petroleum inclusions. Comparison with biomarkers of source-rock extracts shows that oils in the Es3 reservoir of well Chun 51 were generated from the upper Es4 source rocks, whereas oils in the Es3 reservoir of well Liang 28 were derived from the lower Es3 source rocks. Moreover, the microthermometric data and burial history indicate one oil-charging episode in the Es3 reservoirs of the two wells, during the late Neogene. It's concluded that different charging histories of these two reservoirs were attributed mainly to the sealing effect of the fault. • Biomarker compositions of fluid inclusions and free oils were discussed. • Oil-sources of the two studied Es3 reservoirs were single but different. • Oil-charging times of the two Es3 reservoirs were defined. • Different oil-charging histories of the two Es3 reservoirs were analyzed. [ABSTRACT FROM AUTHOR]

The unique Moxi–Gaoshiti Bulge of Sichuan Basin in southwestern China provides insights into the biomarker signatures of bitumens and their geological significance for paleo-oil reservoirs in Precambrian strata. Solid bitumens with various shapes occur widely in the voids, solution pores, cracks, stylolites, and veins of reservoir rocks. Biomarker analysis was conducted on bitumens and the associated source rocks by quantitative detection with gas chromatography–mass spectrometry (GC–MS) to constrain thermal maturity, sedimentary environments, bitumen/paleo-oil sources, and the possible paleo-oil filling directions, which are dominant geological factors that control paleo-oil accumulations. Quantitative analysis of biomarkers showed that the bitumens in the Sinian dolomite of the Moxi–Gaoshiti Bulge belong to the same group. The bitumens are highly matured, and their reflectance values (%R b ) are greater than 1.5 with an average of 2.96. These bitumens originated from thermal cracking of oil (pyrobitmen) via a high-temperature process. The biomarker characteristics revealed that the bitumens and related paleo-oil reservoirs originated from a highly reduced but moderately saline marine shale environment. The marine shales of the Sinian Dengying and lower Cambrian Qiongzhusi formations are their major source rocks. The directions of the primary oil-filling pathways in the Gaoshiti and Moxi sub-bulges are from west to east and from northwest to southeast, respectively. These directions indicate that the Deyang–Anyue sag west of the Moxi–Gaoshiti Bulge is the major hydrocarbon source kitchen. [ABSTRACT FROM AUTHOR]

Determining the place of paleo-oil cracking is crucial to understanding the formation mechanism of the gas reservoirs in the Precambrian–Cambrian strata. For the old strata the attainable information is limited because most paleo-oil have been cracked to gas at high thermal maturity, such as the Anyue giant gas field in the Moxi–Gaoshiti Bulge of Sichuan Basin, Southwestern China. In this study, the place of paleo-oil cracking was discussed based on solid bitumen found in the reservoirs. Numerous solid bitumen from the deep boreholes in the Precambrian Dengying (Z 2 dn 2 and Z 2 dn 4 ) and Lower Cambrian Longwangmiao (Є 1 l) formations of the Moxi–Gaoshiti Bulge were analyzed. Elemental and carbon isotope analyses and optical microscopic observations, such as Raman spectroscopy, scanning electron microscopy, and electronic probe, were performed on these solid bitumen samples. The obtained parameters, including the reflectance of the solid bitumen, parameters I(D)/I(G) and S(D)/S(G) from the Raman spectra, the compositions and carbon isotope of gas, burial history, and the predicted "equivalent vitrinite reflectance Ro" (EqVRo) for reservoirs, jointly support that solid bitumen are epigenetic bitumen in reservoirs other than primary bitumen in source rocks. This study provides a relatively solid evidence of in situ cracking of paleo-oil and the thermochemical sulfate reduction reaction between paleo-oil and dolomite reservoirs. Pyrite were found both in carbonate rocks and argillaceous rock, and the sulfur in pyrite is perceived as a pathway of H 2 S formation. The results provide a basis for understanding the formation mechanism of the deep huge gas field that was derived from paleo-oil cracking, and may contribute to future petroleum exploration in deep Precambrian–Lower Cambrian systems. • A vitrinite reflectance profile of the extensive shale form one well was provided. • The solid bitumen was confirmed to be from in situ oil cracking at high thermal maturity. • Evidences proved that the TSR reaction was involved in this crude oil cracking. • The reaction of pyrite with hydrocarbons was considered as a pathway of H 2 S formation. • Maturities" of solid bitumen and reservoirs were quantitative calculated and compared. [ABSTRACT FROM AUTHOR]