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T : 목차정보

Marine and petroleum geology 32건

  1. [해외논문]   Depositional evolution of a progradational to aggradational, mixed-influenced deltaic succession: Jurassic Tofte and Ile formations, southern Halten Terrace, offshore Norway  

    van Cappelle, M. ; Ravnas, R. ; Hampson, G.J. ; Johnson, H.D.
    Marine and petroleum geology v.80 ,pp. 1 - 22 , 2017 , 0264-8172 ,

    초록

    Predicting the hydrodynamics, morphology and evolution of ancient deltaic successions requires the evaluation of the three-dimensional depositional process regime based on sedimentary facies analysis. This has been applied to a core-based subsurface facies analysis of a mixed-energy, clastic coastal-deltaic succession in the Lower-to-Middle Jurassic of the Halten Terrace, offshore mid-Norway. Three genetically related successions with a total thickness of 100-300 m and a total duration of 12.5 Myr comprising eight facies associations record two initial progradational phases and a final aggradational phase. The progradational phases (I and II) consist of coarsening upward successions that pass from prodelta and offshore mudstones (FA1), through delta front and mouth bar sandstones (FA2) and into erosionally based fluvial- (FA3) and marine-influenced (FA4) channel fills. The two progradational phases are interpreted as fluvial- and wave-dominated, tide-influenced deltas. The aggradational phase (III) consists of distributary channel fills (FA3 and FA4), tide-dominated channels (FA5), intertidal to subtidal heterolithic fine-grained sandstones (FA6) and coals (FA7). The aggradational phase displays more complex facies relationships and a wider range of environments, including (1) mixed tide- and fluvial-dominated, wave-influenced deltas, (2) non-deltaic shorelines (tidal channels, tidal flats and vegetated swamps), and (3) lower shoreface deposits (FA8). The progradational to aggradational evolution of this coastal succession is represented by an overall upward decrease in grain size, decrease in fluvial influence and increase in tidal influence. This evolution is attributed to an allogenic increase in the rate of accommodation space generation relative to sediment supply due to tectonic activity of the rift basin. In addition, during progradation, there was also an autogenic increase in sediment storage on the coastal plain, resulting in a gradual autoretreat of the depositional system. This is manifested in the subsequent aggradation of the system, when coarse-grained sandstones were trapped in proximal locations, while only finer grained sediment reached the coastline, where it was readily reworked by tidal and wave processes.

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  2. [해외논문]   Application of AVO attribute inversion technology to gas hydrate identification in the Shenhu Area, South China Sea  

    Wang, X. ; Pan, D.
    Marine and petroleum geology v.80 ,pp. 23 - 31 , 2017 , 0264-8172 ,

    초록

    AVO (Amplitude Versus Offset) is a seismic exploration technology applied to recognize lithology and detect oil and gas through analyzing the feature of amplitude variation versus offset. Gas hydrate and free gas can cause obvious AVO anomaly. To find geophysical evidence of gas hydrate and free gas in Shenhu Area, South China Sea, AVO attribute inversion method is applied. By using the method, the multiple seismic attribute profiles and AVO intercept versus gradient (I-G) cross plot are obtained. Bottom-simulating reflector (BSR) is observed beneath the seafloor, and the AVO abnormal responses reveal various seismic indicators of gas hydrate and free gas. The final AVO analysis results indicate the existence of gas hydrate and free gas in the upper and lower layers of BSR in the study area.

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  3. [해외논문]   Weathering profiles and clay mineralogical developments, Bornholm, Denmark  

    Tan, P. ; Oberhardt, N. ; Dypvik, H. ; Riber, L. ; Ferrell, R.E.
    Marine and petroleum geology v.80 ,pp. 32 - 48 , 2017 , 0264-8172 ,

    초록

    Saprock-saprolite associations were studied by field and laboratory methods (optical microscopy, X-ray powder diffraction, scanning electron microscopy, electron microprobe) in order to describe regolith development in the crystalline rocks of the Nygard kaolin pit (Bornholm, Denmark). The clay sequences and stages of porosity development are similar to those observed for reservoir rocks from the Utsira High (Riber et al., 2016). The weathering of the parent granite began before the end of the Mesozoic. Two stages of syn-/pre-burial alteration, followed by diagenesis during burial, and then post-uplift weathering have been recognized. In stage I, plagioclase and some biotite (biotite-vermiculite-kaolinite) reacted to form elongate booklets of highly-ordered kaolinite or smaller, blocky pseudohexagonal crystals. Stage II represented more extreme weathering developed along local fracture systems. The higher potential for fluid flow in the fractures caused highly-ordered kaolinite to alter to halloysitic, poorly-ordered kaolinite. Plagioclase, biotite, and K-feldspar continued to interact with formation water and formed additional quantities of secondary clay minerals. As a consequence of inter-, intra-, and trans-granular cracks, the original rock fabric deteriorated and porosity increased. During later burial, diagenetic siderite crystals filled voids and chlorite formed at the expense of kaolinite. After re-exposure, calcite precipitated in localized zones. Smectite formed on a broader scale wherever high ionic strength groundwaters were present. A mineralogical key to predicting where high porosity and permeability zones occur is the recognition of halloysitic, poorly-ordered kaolinite. Highly-ordered kaolinite is abundant, but it is ubiquitous. Siderite, chlorite and smectite adversely affect permeability. Riber, L., Dypvik, H., Sorlie, R. and Ferrell, R. (2016) Clay minerals in deeply buried paleoregolith profiles, Norwegian North Sea. Clays Clay Miner. DOI: 10.1346/CCMN.2016.064036.

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  4. [해외논문]   In situ stress field evaluation of deep marine tight sandstone oil reservoir: A case study of Silurian strata in northern Tazhong area, Tarim Basin, NW China  

    Yin, S. ; Ding, W. ; Zhou, W. ; Shan, Y. ; Xie, R. ; Guo, C. ; Cao, X. ; Wang, R. ; Wang, X.
    Marine and petroleum geology v.80 ,pp. 49 - 69 , 2017 , 0264-8172 ,

    초록

    Deep marine tight sandstone oil reservoirs are the subject of considerable research around the world. This type of reservoir is difficult to develop due to its low porosity, low permeability, strong heterogeneity and anisotropy. A marine tight sandstone oil reservoir is present in the Silurian strata in the northern Tazhong area of the Tarim Basin, NW China, at a depth of more than 5000 m. The porosity is between 6% and 8%, and the gas permeability is between 0.1 and 1 x 10 -3 μm 2 . The features of this type of reservoir include the poor effects of conventional fracturing modifications and horizontal wells, which can lead to stable and low levels of production after staged fracturing. Here, we conduct a comprehensive evaluation of the mechanical properties of the rock and the in situ stress of the target tight sandstones by using numerous mechanical and acoustic property tests, conducing crustal stress analysis and using data from thin section observations. The dispersion correction technique is used to transform velocity at the experimental high frequency (1 MHz) to velocity at the logging frequency (20 kHz). The logging interpretation models of the transverse wave offset time, mechanical parameters and in situ stress are calculated, and each model represents a high precision prediction. Simulating the in situ stress field of the Silurian strata using a three-dimensional finite element method demonstrates that the average error between the simulation result and the measured value is less than 6%. The planar distribution of each principal stress is mainly controlled by the burial depth and fault distribution. By conducting in situ stress orientation analysis for the target layer via the analysis of paleomagnetism, borehole enlargement, fast shear wave orientation and stress field simulation, we show that the direction of the maximum horizontal stress is N45E. In this paper, a typical and successful comprehensive evaluation of the stress field of the deep tight sandstone oil reservoir is provided.

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  5. [해외논문]   Petroleum accumulation in the deeply buried reservoirs in the northern Dongying Depression, Bohai Bay Basin, China: New insights from fluid inclusions, natural gas geochemistry, and 1-D basin modeling  

    Ping, H. ; Chen, H. ; Jia, G.
    Marine and petroleum geology v.80 ,pp. 70 - 93 , 2017 , 0264-8172 ,

    초록

    The deeply buried reservoirs (DBRs) from the Lijin, Shengtuo and Minfeng areas in the northern Dongying Depression of the Bohai Bay Basin, China exhibit various petroleum types (black oil-gas condensates) and pressure systems (normal pressure-overpressure) with high reservoir temperatures (154-185 o C). The pressure-volume-temperature-composition (PVTX) evolution of petroleum and the processes of petroleum accumulation were reconstructed using integrated data from fluid inclusions, stable carbon isotope data of natural gas and one-dimensional basin modeling to trace the petroleum accumulation histories. The results suggest that (1) the gas condensates in the Lijin area originated from the thermal cracking of highly mature kerogen in deeper formations. Two episodes of gas condensate charging, which were evidenced by the trapping of non-fluorescent gas condensate inclusions, occurred between 29-25.5 Ma and 8.6-5.0 Ma with strong overpressure (pressure coefficient, P c = 1.68-1.70), resulting in the greatest contribution to the present-day gas condensate accumulation; (2) the early yellow fluorescent oil charge was responsible for the present-day black oil accumulation in well T764, while the late blue-white oil charge together with the latest kerogen cracked gas injection resulted in the present-day volatile oil accumulation in well T765; and (3) the various fluorescent colors (yellow, blue-white and blue) and the degree of bubble filling (F v ) (2.3-72.5%) of the oil inclusions in the Minfeng area show a wide range of thermal maturity (API gravity ranges from 30 to 50 o ), representing the charging of black oil to gas condensates. The presence of abundant blue-white fluorescent oil inclusions with high Grain-obtaining Oil Inclusion (GOI) values (35.8%, usually >5% in oil reservoirs) indicate that a paleo-oil accumulation with an approximate API gravity of 39-40 o could have occurred before 25 Ma, and gas from oil cracking in deeper formations was injected into the paleo-oil reservoir from 2.8 Ma to 0 Ma, resulting in the present-day gas condensate oil accumulation. This oil and gas accumulation model results in three oil and gas distribution zones: 1) normal oil reservoirs at relatively shallow depth; 2) gas condensate reservoirs that originated from the mixture of oil cracking gas with a paleo-oil reservoir at intermediate depth; and 3) oil-cracked gas reservoirs at deeper depth. The retardation of organic matter maturation and oil cracking by high overpressure could have played an important role in the distribution of different origins of gas condensate accumulations in the Lijin and Minfeng areas. The application of oil and gas accumulation models in this study is not limited to the Dongying Depression and can be applied to other overpressured rift basins.

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  6. [해외논문]   Pore pressure within dipping reservoirs in overpressured basins  

    Gao, B. ; Flemings, P.B.
    Marine and petroleum geology v.80 ,pp. 94 - 111 , 2017 , 0264-8172 ,

    초록

    To predict reservoir pore pressure, we present a one-dimensional flow model that captures complicated two- and three-dimensional flow present in a dipping permeable reservoir encased in overpressured mudrock. The model incorporates the variation of mudrock permeability with effective stress and includes the effect of reservoir geometry. We find that reservoir pressure is lower when stress-dependent mudrock permeability is assumed relative to the case of constant mudrock permeability. Increased structural relief further reduces the reservoir pressure relative to the far-field pressure and increased effective stress (pore pressure is lower relative to the overburden) results in increased reservoir pressure relative to the far-field pressure. If a large fraction of the reservoir area is in deeper areas where the mudrocks are more overpressured, then the relative pressure is higher than cases where the reservoir area remains constant with depth. The model results compare favorably both to pressures predicted by a more complex numerical model that simulates basin evolution and to field observations in the Bullwinkle Basin (Green Canyon 65, Gulf of Mexico). Our model provides a quick workflow to predict excess pressures in dipping reservoirs encased in mudrock within mechanically-compacted basins. It can be used to analyze trap integrity, understand hydrocarbon migration, and improve drilling safety.

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  7. [해외논문]   Assessment of thermal evolution of Paleozoic successions of the Holy Cross Mountains (Poland)  

    Schito, A. ; Corrado, S. ; Trolese, M. ; Aldega, L. ; Caricchi, C. ; Cirilli, S. ; Grigo, D. ; Guedes, A. ; Romano, C. ; Spina, A. ; Valentim, B.
    Marine and petroleum geology v.80 ,pp. 112 - 132 , 2017 , 0264-8172 ,

    초록

    Poland is considered the most prospective country for shale gas production in Europe. Hydrocarbon generation/expulsion scenarios, drawn in the latest intensive exploration phases, tend to overestimate maturation levels when compared with brand new data acquired after recent drillings. We tested an integrated workflow to correlate published and original thermal maturity datasets for the Paleozoic to Jurassic successions cropping out in the Holy Cross Mountains. These successions, when preserved in subsurface, host the major source rocks in the area. The application of the workflow allowed us to highlight the burial and thermal evolutionary scenarios of the two tectono-stratigraphic blocks of the Holy Cross Mountains (Lysogory and Kielce blocks) and to propose this approach as a tool for reducing levels of uncertainty in thermal maturity assessment of Paleozoic successions worldwide. In particular, published datasets including colour alteration indexes of Paleozoic microfossils (conodont, acritarchs) and vitrinite and graptolite reflectance data, show differences in levels of thermal maturity for the Lysogory (mid mature to overmature) and Kielce (immature to late mature) blocks. Original data, derived from optical analysis, pyrolysis, and Raman spectroscopy on kerogen, and X-Ray diffraction on fine-grained sediments, mostly confirm and integrate published data distribution. 1D thermal models, constrained by these data, show burial and exhumation events of different magnitude, during the Late Cretaceous, for the Lysogory (maximum burial depths of 9 km) and Kielce (burial depths of 6 km) blocks that have been related to the Holy Cross Fault polyphase activity. In the end, Palynomorph Darkness Index and Raman spectroscopy on kerogen, for Llandoverian and Cambrian rocks, turned out to be promising tools for assessing thermal maturity of Paleozoic organic facies devoid of vitrinite macerals.

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  8. [해외논문]   Hydrocarbon source rock potential in the southwestern Gulf of Suez graben: Insights from organic geochemistry and palynofacies studies on well samples from the Ras El Bahar Oilfield  

    El Diasty, W.Sh. ; El Beialy, S.Y. ; Mostafa, A.R. ; El Adl, H.A. ; Batten, D.J.
    Marine and petroleum geology v.80 ,pp. 133 - 153 , 2017 , 0264-8172 ,

    초록

    Palynological and biomarker characteristics of organic facies recovered from Cretaceous-Miocene well samples in the Ras El Bahar Oilfield, southwest Gulf of Suez, and their correlation with lithologies, environments of deposition and thermal maturity have provided a sound basis for determining their source potential for hydrocarbons. In addition to palynofacies analysis, TOC/Rock-Eval pyrolysis, kerogen concentrates, bitumen extraction, carbon isotopes and saturated and aromatic biomarkers enable qualitative and quantitative assessments of sedimentary organic matter to be made. The results obtained from Rock-Eval pyrolysis and molecular biomarker data indicate that most of the samples come from horizons that have fair to good hydrocarbon generation potential in the study area. The Upper Cretaceous-Paleocene-Lower Eocene samples contain mostly Type-II to Type-III organic matter with the capability of generating oil and gas. The sediments concerned accumulated in dysoxic-anoxic marine environments. By contrast, the Miocene rocks yielded mainly Type-III and Type-II/III organic matter with mainly gas-generating potential. These rocks reflect deposition in a marine environment into which there was significant terrigenous input. Three palynofacies types have been recognized. The first (A) consists of Type-III gas-prone kerogen and is typical of the Early-Middle Miocene Belayim, Kareem and upper Rudeis formations. The second (B) has mixed oil and gas features and characterizes the remainder of the Rudeis Formation. The third association (C) is dominated by amorphous organic matter, classified as borderline Type-II oil-prone kerogen, and is typical of the Matulla (Turonian-Santonian) and Wata (Turonian) formations. Rock-Eval T max , PI, hopane and sterane biomarkers consistently indicate an immature to early mature stage of thermal maturity for the whole of the studied succession.

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  9. [해외논문]   Geochemistry, origin, and accumulation of petroleum in the Eocene Wenchang Formation reservoirs in Pearl River Mouth Basin, South China Sea: A case study of HZ25-7 oil field  

    Peng, J. ; Pang, X. ; Peng, H. ; Ma, X. ; Shi, H. ; Zhao, Z. ; Xiao, S. ; Zhu, J.
    Marine and petroleum geology v.80 ,pp. 154 - 170 , 2017 , 0264-8172 ,

    초록

    The Pearl River Mouth Basin in the South China Sea has accumulated >2 km of Eocene sediments in its deep basin, and has become the exploration focus due to the recent discoveries of the HZ25-7 oil field in the Eocene Wenchang (E 2 w) Formation. In this study, the geochemical characteristics of potential source rocks and petroleum in the HZ25-7 oil field are investigated and the possible origins and accumulation models developed. The analytical results reveal two sets of potential source rocks, E 2 w and Enping (E 2 e) formations developed in the study area. The semi-deep-to-deep lacustrine E 2 w source rocks are characterized by relatively low C 29 steranes, low C 19 /C 23 tricyclic terpane ( 24 tetracyclic terpane/C 30 hopane ( 30 hopane (most 30 4-methyl sterane/ΣC 29 sterane (>0.2) ratios. In contrast, the shallow lacustrine and deltaic swamp-plain E 2 e source rocks are characterized by relatively high C 29 steranes, high C 19 /C 23 tricyclic terpane (>0.6), high C 24 tetracyclic terpane/C 30 hopane (>0.1), variable yet overall high T/C 30 hopane, and low C 30 4-methyl sterane/ΣC 29 sterane ( 19 /C 23 tricyclic terpane ratios (mean value: 0.39), low C 24 tetracyclic terpane/C 30 hopane ratios (mean value: 0.07), high C 30 4-methyl sterane/ΣC 29 sterane ratios (mean value: 1.14), and relatively high C 27 regular sterane content of petroleum in the HZ25-7 oil field indicate that the petroleum most likely originated from the E 2 w Formation mudstone in the Huizhou Depression. One stage of continuous charging is identified in the HZ25-7 oil field; oil injection is from 16 Ma to present and peak filling occurs after 12 Ma. Thin sandstone beds with relatively good connectivity and physical properties (porosity and permeability) in the E 2 w Formation are favorable conduits for the lateral migration of petroleum. This petroleum accumulation pattern implies that the E 2 w Formation on the western and southern margins of the Huizhou Depression are favorable for petroleum accumulation because they are located in a migration pathway. Thus exploration should focus in these areas in the future.

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  10. [해외논문]   Mapping gas hydrate and fluid flow indicators and modeling gas hydrate stability zone (GHSZ) in the Ulleung Basin, East (Japan) Sea: Potential linkage between the occurrence of mass failures and gas hydrate dissociation  

    Horozal, S. ; Bahk, J.J. ; Urgeles, R. ; Kim, G.Y. ; Cukur, D. ; Kim, S.P. ; Lee, G.H. ; Lee, S.H. ; Ryu, B.J. ; Kim, J.H.
    Marine and petroleum geology v.80 ,pp. 171 - 191 , 2017 , 0264-8172 ,

    초록

    The Ulleung Basin, East (Japan) Sea, is well-known for the occurrence of submarine slope failures along its entire margins and associated mass-transport deposits (MTDs). Previous studies postulated that gas hydrates which broadly exist in the basin could be related with the failure process. In this study, we identified various features of slope failures on the margins, such as landslide scars, slide/slump bodies, glide planes and MTDs, from a regional multi-channel seismic dataset. Seismic indicators of gas hydrates and associated gas/fluid flow, such as the bottom-simulating reflector (BSR), seismic chimneys, pockmarks, and reflection anomalies, were re-compiled. The gas hydrate occurrence zone (GHOZ) within the slope sediments was defined from the BSR distribution. The BSR is more pronounced along the southwestern slope. Its minimal depth is about 100 m below seafloor (mbsf) at about 300 m below sea-level (mbsl). Gas/fluid flow and seepage structures were present on the seismic data as columnar acoustic-blanking zones varying in width and height from tens to hundreds of meters. They were classified into: (a) buried seismic chimneys (BSC), (b) chimneys with a mound (SCM), and (c) chimneys with a depression/pockmark (SCD) on the seafloor. Reflection anomalies, i.e., enhanced reflections below the BSR and hyperbolic reflections which could indicate the presence of gas, together with pockmarks which are not associated with seismic chimneys, and SCDs are predominant in the western-southwestern margin, while the BSR, BSCs and SCMs are widely distributed in the southern and southwestern margins. Calculation of the present-day gas-hydrate stability zone (GHSZ) shows that the base of the GHSZ (BGHSZ) pinches out at water depths ranging between 180 and 260 mbsl. The occurrence of the uppermost landslide scars which is below about 190 mbsl is close to the range of the GHSZ pinch-out. The depths of the BSR are typically greater than the depths of the BGHSZ on the basin margins which may imply that the GHOZ is not stable. Close correlation between the spatial distribution of landslides, seismic features of free gas, gas/fluid flow and expulsion and the GHSZ may suggest that excess pore-pressure caused by gas hydrate dissociation could have had a role in slope failures.

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