Exploratory Development Institute of Qinghai Petroleum Administration

Dunhuang, China

Exploratory Development Institute of Qinghai Petroleum Administration

Dunhuang, China
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Sun G.-Q.,CAS Institute of Geology and Geophysics | Chen B.,CAS Institute of Geology and Geophysics | Chen B.,University of Chinese Academy of Sciences | Zheng Y.-X.,Exploratory Development Institute of Qinghai Petroleum Administration | And 3 more authors.
Natural Gas Geoscience | Year: 2015

Based on petrology, mineralogy and geochemistry, the diagenesis, depositional environment and origin of Miocene clastic rock of Shangganchaigou Formation in Lenghu V tectonic belt on the northern margin of the Qaidam Basin were studied. The experimental results demonstrated that particles of Miocene clastic rock of Shangganchaigou Formation mainly had point contact or line contact relationships, and had been suffered strong compaction; the clastic rock of Shangganchaigou Formation had high contents of clay minerals with average value was 22.74%, which were dominated by illite, chlorite and mixed layer of illite and montmorillonite; calcite was the main types of carbonate cements, and dolomite was minor; the carbon isotope (δ13C) of carbonate cements ranged from -6.88‰ to -3.8‰, and the average value was -5.39‰; the oxygen isotope (δ18O) ranged from -12.74‰ to -6.98‰, and the average value was -10.18‰; Z-value of paleosalinity estimated by δ13C and δ18O ranged from 107.65 to 114.89 and the average value was 111.34; and temperature of carbonate deposited ranged from 52.34℃ to 88.93℃, and the average value was 72.08℃. Above results, combined with the comprehensive analysis of some geochemical elements, such as major elements, trace elements and organic carbon content, suggested that main diagenetic stage of Miocene clastic rock of Shangganchaigou Formation in Lenghu V tectonic belt was in phase B of early diagenetic stage B or phase A of the middle diagenetic stage. The depositional environment of Miocene Shangganchaigou Formation in Lenghu V tectonic belt was dominated by stably warm and humid climate, and of which the main diagenesis of reservoirs currently are in period B of early diagenetic stage to period A of the middle diagenetic stage. ©, 2015, Science Press. All right reserved.


Sun G.-Q.,CAS Institute of Geology and Geophysics | Wang H.-F.,Exploratory Development Institute of Qinghai Petroleum Administration | Zou K.-Z.,Exploratory Development Institute of Qinghai Petroleum Administration | Wang W.-Z.,Exploratory Development Institute of Qinghai Petroleum Administration | And 3 more authors.
Natural Gas Geoscience | Year: 2014

Based on the analyses of petrology, mineralogy and geochemistry, the depositional environment and origin of carbonate cements of Jurassic sandstones in Jiulongshan Region on the northern margin of the Qaidam Basin are studied. The experimental results demonstrate that there were four kinds of autogenic carbonate cements: calcite, iron-bearing calcite, dolomite and ankerite, whose carbon isotope (δ13C) ranged from -15.1‰ to -1.3‰ with an average value of -6.01‰, and oxygen isotope (δ18O) ranged from -17.8‰ to -11.2‰ with an average value of -15.06‰, and Z-value of paleosalinity ranged from 87.71 to 117.77 with an average value of 107.5. The above results showed that small amount of organic carbon involved in the early diagenesis of Jurassic sandstones in Jiulongshan Region, and diagenetic fluids were mainly leaching freshwater from clast and atmosphere. The temperature to form carbonate cements was 78.5-126.55℃ with an average value of 105.86℃. According to paleo-goethermal gradient, the burial depth of Jurassic sandstones should be about 2.5km, but the actual burial depth was less than 1.6km, so it was concluded that the Jurassic Formation in Jiulongshan region had experienced strong tectonic movement and were uplifted about 1.0km after deeply buried.


Sun G.-Q.,CAS Institute of Geology and Geophysics | Ma J.-Y.,Exploratory Development Institute of Qinghai Petroleum Administration | Si D.,Exploratory Development Institute of Qinghai Petroleum Administration | Wang H.-F.,Exploratory Development Institute of Qinghai Petroleum Administration | And 2 more authors.
Natural Gas Geoscience | Year: 2013

Based on the analyses of sedimentary sequence, lithology, particle size, and logging data from more than 20 drilling wells in Maxian region on the northern margin of the Qaidam Basin, the sedimentary characteristics and its evolution of Paleogene Lower Xiaganchaigou Formation were studied. The results showed that braided fluvial facies were the main sediment types of this formation, including channel bar, point bar, and flood plain, and the environment with water withdrawal was the main depositional environment in this period. According to the fine structural interpretation of 3D seismic data, seismic attributes can also well illustrate the changes of depositional environment of the Lower Xiaganchaigou Formation: In the early period, the sediments were mainly from northeast of the Maxian region, and a little from the north, and sandbodies were mainly dominated by the northeastern provenance; Along with the basin development, the northeastern provenance gradually migrated westward, and its supplies also decreased, in contrast, the supplies from the northern provenance increased; In the later period, the above two provenances got closed, and then developed large and contiguous sandbodies. Preliminary conclusions about the environmental evolution of Lower Xiaganchaigou Formation in Maxian region and three sandbodies distribution can provide reliable geological data for the next oil and gas exploration.

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