Tianjin Branch of China National Offshore Oil Co.

Tianjin, China

Tianjin Branch of China National Offshore Oil Co.

Tianjin, China
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Tian J.,Wuhan University | Hao F.,Wuhan University | Zhou X.,Tianjin Branch of China National Offshore Oil Co. | Zou H.,China University of Petroleum - Beijing
AAPG Bulletin | Year: 2017

The vast majorityofdiscovered oilsin the Bohai offshore area have undergone biodegradation ranging from 1 to 9 on the PM scale (a scale to rank the level of biodegradation, proposed by Peters and Moldowan, 1993). The extent of distribution and biodegradation of all discovered oils in the Bohai offshore area was investigated systematically using geologic and geochemical data to reveal controlling factors of varying levels of biodegraded oils. Based on the analysis of the environment and material significances and the resistance to degradation of biomarkers, the biomarker parameter assemblage that is suitable for the oil-source correlation of severely biodegraded oils (higher than PM 6) in the Bohai offshore area was determined. The spatial distribution and biodegradation extent are mainly controlled by the current burial depth, the duration of biodegradation, the area of the oil-water contact (OWC), and a late strike-slip movement of the Tanlu fault. Almost all biodegraded oils are found in shallow reservoirs above 2000 m (6562 ft). The longer the oils are present in these reservoirs or the larger the area of the OWC the reservoirs show, the greater the extent of biodegradation will be. The late, strong strike-slip movement of the Tanlu fault may have significantly enhanced the biodegradation extent of several oils in fields located in the Tanlu fault zone by introducing oxygenated freshwater from the surface or near surface and creating a more suitable environment for biodegradation. The C19 tricyclic terpane/C23 tricyclic terpane, C24 tetracyclic/C26 tricyclic terpane, and gammacerane/C24 Tetracyclic do not seem to be influenced by biodegradation and show obvious differences between the three different source-rock intervals. Such a biomarker parameter assemblage can be used successfully to determine the origin of severely biodegraded oils (higher than PM 6) by correlating with extracts of possible source rocks in the Bohai offshore area. Copyright © 2017. The American Association of Petroleum Geologists. All rights reserved.

Sun Z.,Wuhan University | Zhu H.,Wuhan University | Xu C.,Tianjin Branch of China National Offshore Oil Co. | Yang X.,Wuhan University | And 3 more authors.
Geofluids | Year: 2017

Volcanic activities exert a significant influence on pore fluid property and related diagenetic processes that substantially controlled reservoirs quality. Analysis of Paleogene medium-deep sandstones on the Huanghekou Sag provides insight into relating the diagenetic processes to pore fluid property evolution influenced by volcanic activities. Three distinct types of pore fluids were identified on the basis of an integrated and systematic analysis including core and thin section observation, XRD, SEM, CL, and trace element. Alkaline aqueous medium environment occurred in E2s1+2 where volcanic activities have insignificant influence on pore fluids, evidenced by typical alkaline diagenetic events such as K-feldspar albitization, quartz dissolution, feldspar dissolution, and carbonate cementation. During the deposition of E3d3, influx of terrestrial freshwater and alteration of ferromagnesianrich pore water result in the formation of mixing aqueous medium environment through volcanic eruption dormancy causing zeolite dissolution, clay mineral transformation, and K-feldspar albitization. Ferromagnesian-rich aqueous medium environment developed resulting fromthe intensive hydrolysis of the unstable ferromagnesian minerals formed due to intense volcanic activities during E2s1+2 and corresponding predominant diagenetic processes were characterized by the precipitation and dissolution of lowsilica zeolites. Therefore, the differential properties of pore fluids caused various diagenetic processes controlling reservoir quality. © 2016 Fortress Press.

Teng C.,Wuhan University | Hao F.,Wuhan University | Zou H.,China University of Petroleum - Beijing | Zhou X.,Tianjin Branch of China National Offshore Oil Co. | Xu C.,Tianjin Branch of China National Offshore Oil Co.
AAPG Bulletin | Year: 2016

The Tan-Lu fault system in the central Liaodong Bay subbasin, Bohai Bay Basin, has complex structural characteristics, and its tectonism during the Cenozoic is an important factor in oil accumulation. Three-dimensional seismic data were used to document the structural features and evolution of the system. Variations in source rock occurrence, oil catchment area, and faulting intensity were comprehensively evaluated to discuss the heterogeneity of oil occurrence along the system. Detailed analysis of the seismic data indicates a right-lateral slip for the Tan-Lu fault system. Transpression and transtension occur on two branches of the Tan-Lu fault with different orientations, indicating a likely slip azimuth that is between the two orientations, i.e., 30°-35°. The strike-slip began at the middle stage of deposition of the Shahejie Formation and reached its climax during deposition of the first and second members of the Dongying Formation. To date, the slip is still continuing. In the transpressional system, the lower strata on opposite sides of the strike-slip fault were shortened and folded, whereby the upper strata were stretched and normal faulted. As a result, a negative flower structure developed immediately above a positive flower structure. Strain distribution in this system is similar to that in a classic fold. Moderate tectonic deformation could enlarge the oil catchment area, benefiting oil accumulation. Weak or intense deformation is unfavorable for commercial oil accumulation because of a small oil catchment area and poor oil preservation, respectively. © Copyright 2016. The American Association of Petroleum Geologists. All rights reserved.

Wang Q.,China University of Petroleum - Beijing | Hao F.,China University of Petroleum - Beijing | Hao F.,Wuhan University | Xu C.,Tianjin Branch of China National Offshore Oil Co. | And 2 more authors.
Marine and Petroleum Geology | Year: 2015

TOC and Rock-Eval analyses were conducted on cutting samples (111) from various Paleogene formations (Ed3, Es1 and Es3) in the Qinnan sag. The average values of total organic carbon (TOC) content are 1.11, 1.64 and 2.29% for Ed3, Es1 and Es3 samples, respectively. The Es1 and Es3 source rocks are of relatively high S2 values, ranging from 0.42 to 46.01 and 2.46-61.01mgHC/Rock, respectively. The Ed3 rocks have lower generative potential with S2 values ranging from 0.9 to 9.3mg HC/g Rock. Moreover, Tmax values indicate that these source rocks are sufficiently mature for petroleum generation. These analyses suggest that Es1 and Es3 are potential source rocks for oils produced from the QHD29 field.Eighteen oil samples from the QHD29 field were analyzed by GC and GC-MS; and 84 QHD29 oil (13) and source rock (71) samples were employed for stable carbon isotope analysis. Based on hierarchical cluster analysis of selected biomarker parameters, the QHD29 oils can be identified into two groups. Group I and group II oils are both derived from the Eocene Shahejie Formation (Es1 and Es3), displaying remarkable difference to the Oligocene Ed3-derived oils. In comparison with Group II oils, Group I oils display relatively low 4MSI and high G/H, indicating that group I oils have important contributions from Es1 source rock, deposited under more alkaline-saline environment. Moreover, these two group oils can be clearly separated by δ13C values, and Group I oils are isotopically lighter than Group II oils. Difference occurs in stable carbon isotope distribution between Es1 and Es3 source rock extracts as well, and Es1 source rocks are characterized by relatively light carbon isotopic composition. This implies that Group I oil shares more Es1-derived oil, which is consistent with the results of biomarker analysis. © 2015 Elsevier Ltd.

Xu S.,China University of Petroleum - Beijing | Hao F.,China University of Petroleum - Beijing | Hao F.,Wuhan University | Xu C.,Tianjin Branch of China National Offshore Oil Co. | And 2 more authors.
AAPG Bulletin | Year: 2014

Tracing petroleum migration pathways is essential for predicting petroleum occurrence and reducing exploration risks associated with hydrocarbon charge, but a difficult task because of rapid lateral and vertical facies changes in lacustrine basins. An integration of geological, geophysical, and geochemical analysis is employed to investigate the origin of crude oil, the carrier-bed architecture, and migration pathways from source to trap in the JX1-1 oil field, Liaodong Bay subbasin, Bohai Bay Basin. Detailed geochemical studies suggest that three potential source-rock intervals (E2S3, E2S1 and E3d3) exist in the Liaodong Bay subbasin, and crude oil in the JX1-1 field was derived from the E2S3 and E2S1 source rocks. The carrier beds from E2S3 and E2S1 source rocks to the trap were characterized using geophysical data. The fan-delta sandstone in the E2S3 Member has an immediate contact with E2S3 source rock and served as dominant conduit for the expulsion and migration of oil generated from E2S3 source rock. The E3d3 braided-delta sandstones overlying the E2S1 source rock served as dominant conduit for E2s1-sourced oil. The focusing of petroleum migration pathways and the merge of migration pathways in E2S3 and E3d3 sandstones account for the accumulation of the JX1-1 field and the mixing of E2S3- and E2s1-sourced oil in the field. This study suggests that the distribution of permeable sandstones and their stratigraphic contact with the source rocks are key for petroleum migration and occurrence, and integration of geophysical, geological, and geochemical studies provide an effective way to trace petroleum migration pathways. Copyright © 2014. The American Association of Petroleum Geologists. All rights reserved.

Hao F.,China University of Petroleum - Beijing | Hao F.,Wuhan University | Zhou X.,Zhejiang University | Zhu Y.,Tianjin Branch of China National Offshore Oil Co. | Yang Y.,China University of Petroleum - Beijing
Organic Geochemistry | Year: 2011

Three Paleogene syn-rift intervals from the Bohai Bay Basin, the most petroliferous basin in China, were analyzed with sedimentological and geochemical techniques to characterize the lateral source rock heterogeneities, to reveal the environmental and ecological changes through geologic time and to construct depositional models for lacustrine source rocks under different tectonic and climatic conditions. The third (Es3) and first (Es1) members of the Eocene Shahejie Formation and the Oligocene Dongying Formation (Ed) display widely variable total organic carbon contents, hydrogen indices and visual kerogen compositions, suggesting changes in organic facies from deep to marginal sediments. Carefully selected deep-lake facies samples from any interval, however, display fairly uniform biomarker composition. These three intervals have distinctly different biomarker assemblages, which indicate weakly alkaline, freshwater lakes with a moderately deep thermocline during Es3 deposition, alkaline-saline lakes with shallow chemocline during Es1 deposition and acidic, freshwater lakes with deep, unstable thermocline during the deposition of the Dongying Formation. Such environmental changes corresponded to changes in subsidence rate and paleoclimate, from rapid subsidence and wet climate during Es3 deposition, through slow subsidence and arid climate during Es1 deposition to rapid subsidence and wet climate during Ed deposition and resulted in synchronous changes in terrigenous organic matter input, phytoplankton community and primary productivity. The co-evolution of environments and organisms controlled by tectonic subsidence and climate accounted for the deposition and distribution of high quality lacustrine source rocks with distinctly different geochemical characteristics. Most rift basins experienced changes in subsidence rates and possibly changes in climates during their syn-rift evolutions. The models constructed in this paper may have important implications for source rock prediction in other lacustrine rift basins. © 2011 Elsevier Ltd.

Hao F.,Wuhan University | Hao F.,China University of Petroleum - Beijing | Zhou X.,Tianjin Branch of China National Offshore Oil Co. | Zou H.,China University of Petroleum - Beijing | And 2 more authors.
Journal of Earth Science | Year: 2012

This paper discusses origin and charging histories of the Bozhong (Chines source) 25-1 field (BZ25-1) in the Bozhong sub-basin, Bohai (Chines source) Bay basin. Petroleum is contained in both Paleogene and Neogene reservoirs in the BZ25-1 field. The origin of the field was studied using biomarker distributions for 61 source rock samples and 34 oil samples. Oil in the Paleogene reservoirs was derived from the third member (Es 3, 43. 0-38. 0 Ma in age) of the Eocene Shahejie (Chines source) Formation, whereas oil in the Neogene reservoirs was a mixtures of oil generated from the third member and the first member (Es 1, 35. 8-32. 8 Ma) of the Eocene Shahejie Formation. Charging of the shallow Neogene reservoirs was dynamic, probably ongoing, which was a combined result of the existence of active source rocks, the development of overpressure and the fault reactivation since about 5. 1 Ma. On the contrary, the deep Paleogene reservoirs experienced intensive oil leakage as indicated by the high GOI (grains-containing-oil-inclusions) values (up to 30%) for samples below the present-day oil-water contact. Part of the oil that leaked from the Paleogene reservoirs re-accumulated in the shallow Neogene reservoirs. The variation of oil origins within the BZ25-1 field, and the dynamic petroleum charging into the shallow Neogene reservoirs and leakage from the deep Paleogene reservoirs have important implications for petroleum exploration. © 2012 China University of Geosciences and Springer-Verlag Berlin Heidelberg.

Jin S.,Wuhan University | Wang H.,Wuhan University | Chen S.,Wuhan University | Gan H.,Wuhan University | And 2 more authors.
Journal of Earth Science | Year: 2013

Yinger sag is the main petroleum generative sag in eastern Jiuquan Basin, and only the Changshaling oil resource has been found after 60 years prospecting. Changshaling anticline crest zone was formed above the regional uplift, and was slightly affected by over thrust during Tertiary Period. The anticline crest was identified as a structural transposition zone. Based on analysis of seismic facies, logging facies and seismic inversion technique, it has been demonstrated that anticline crest zone conducts drainage entering basin and dominates sedimentary detritus further dispersing, and the anticline crest zone controls the distribution of sand bodies and the development of sedimentary system consequently. The sequence stratigraphic patterns of multi-step fault belt in Member 3 of Xiagou Formation in Lower Cretaceous in the anticline crest zone is composed of the development of sedimentary facies in plan and distribution of multi-step fault belt sand bodies in spatial. This research investigates the sand-control models and sequence patterns, and finally a model of reservoirs in anticline crest zone is identified. © 2013 China University of Geosciences and Springer-Verlag Berlin Heidelberg.

Wang Q.,China University of Petroleum - Beijing | Zou H.,China University of Petroleum - Beijing | Hao F.,China University of Petroleum - Beijing | Hao F.,Wuhan University | And 5 more authors.
Organic Geochemistry | Year: 2014

The exploration history of Bohai Sea reveals that Liaodong Bay is relatively rich in natural gas, which is mainly gas condensate; however, the source rocks in Liaodong Bay share a medium maturity level with values of %Ro being generally. <. 1.3. This study was undertaken to better understand gas potential of Paleogene oil-prone source rocks (II) in Liaodong Bay, Bohai Sea.Three immature Paleogene source rocks were selected to complete gold tube pyrolysis experiments. The experiment results reveal that the secondary gas from oil cracking can be neglected until the cumulative yields of C6-C14 compounds reach the maximum (corresponding to %Ro~1.3). Above %Ro~1.3%, oil starts to crack to wet gases substantially. Based on comparative analysis of pyrolysis results and source rock geochemical parameters, we constructed a hydrocarbon generation model, especially for hydrocarbon gas, and validated the calculated %Ro values for pyrolysis conditions. The C1-C5 yields for source rocks at ~1.3 %Ro in gold tube pyrolysis approximate the maximum gas yield for source rock in open system pyrolysis, indicating the majority of primary gas from kerogen cracking has been generated at ~1.3 %Ro, with its yields being 156ml/g TOC, 100ml/g TOC and 117ml/g TOC for Ed3, Es1 and Es3 source rocks, respectively. This suggests that source rocks with %Ro<1.3 are of good primary gas generation potential. The extrapolation of kinetic parameters of C1-C5 shows that source rocks are generally at the stage of primary gas in Liaodong Bay, where proved gases are primary gas with estimated values of %Ro<1.3. © 2014 Elsevier Ltd.

Zhang C.,Wuhan University | Xie X.-N.,Wuhan University | Guo X.-R.,Wuhan University | Liu X.-F.,Wuhan University | And 2 more authors.
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2013

The geological evolution of the Bozhong sub-basin, characterized by rapid subsidence and strong fault activities since the initiation of the Dongying Formation, exerts important effect on the characteristics of hydrocarbon accumulation in this area, which is distinguished from those in other areas in the Bohai Bay Basin. Uplifts around depressions serve as predominant sites for hydrocarbon accumulation, and the distribution and evolution of pathway systems have obviously been controlling hydrocarbon migration and accumulation. Based on clarification of the distribution of hydrocarbon source rocks and petroleum resources in the large-scale Bozhong petroleum system, growing characteristics of all kinds of potential pathways and their spatial relevance are analyzed by means of multiple data, and then three pathway system types controlling hydrocarbon migration and accumulation: fault-dominant, carrier bed-dominant and unconformity-dominant types are identified. Long-term growth faults adjoining uplifts act as the predominant pathways for vertical fluid release and hydrocarbon migration, and control hydrocarbon accumulation in the Neogene reservoirs on uplifts. Especially in the active stage of tectonic movement, the open long-term growth faults must be preferential pathways for the rapid vertical hydrocarbon migration. The interconnected sandbodies in the Paleogene Shahejie and Dongying Formations, directly contacting with active hydrocarbon source rocks, serve as the primary sites and starting stations for the early and late hydrocarbon migration and accumulation, respectively. Therefore, they not only control hydrocarbon accumulation in the Paleogene traps, but also directly impact hydrocarbon supply to the Neogene trap on uplifts to some extent. Unconformity T8, resulted from regionally tectonic transformation in last Mesozoic, serve as pathway for deep lateral hydrocarbon migration and control hydrocarbon accumulation in the buried hill type reservoirs due to its improved permeability attributed to long-term weathering process. Three types of pathway systems all impact even control the times, locations, velocities and scales of hydrocarbon accumulation in various degrees. However, the fault-dominant type pathway system shows the most outstanding effect among them.

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