Journal of Petroleum Geology最新文献

{"title":"HIGHER LANDPLANT –DERIVED BIOMARKERS IN LIGHT OILS AND CONDENSATES FROM THE COAL-BEARING EOCENE PINGHU FORMATION, XIHU SAG, EAST CHINA SEA SHELF BASIN","authors":"X. Cheng,&nbsp;D. J. Hou,&nbsp;Z. Zhao,&nbsp;Y. H. Jiang,&nbsp;X. H. Zhou,&nbsp;H. Diao","doi":"10.1111/jpg.12774","DOIUrl":"10.1111/jpg.12774","url":null,"abstract":"<p>The Cenozoic Xihu Sag in the East China Sea Shelf Basin contains large reserves of coals together with liquid petroleum derived from coal-associated sediments. However, the origin of the petroleum is not well understood. In this study, biomarker assemblages in a suite of recently discovered light oils and condensates from the Paleogene succession in the western margin of in the Xihu Sag were investigated using gas chromatography – mass spectrometry. The objectives were to investigate the samples' thermal maturity and the depositional environment of the precursor source rocks which generated the oils. The light oils are believed to have been derived from coaly source rocks in the Eocene Pinghu Formation.</p><p>Assessment of thermal maturity based on CPI, pristane/n-C₁₇ ratio and isomerisation ratios of C₂₉ steranes and C₃₁ homohopanes suggest that the hydrocarbons have a relatively low maturity in the early to mid oil generation window. The distribution of isoprenoids relative to n-alkanes, the high pristane/phytane ratios (5.1–10.7), the almost complete absence of gammacerane and C₃₃₊ homohopanes, and the low dibenzothiophene/phenanthrene ratios indicate that the source rocks of the hydrocarbons were deposited in a relatively oxic and sulphate-poor fluvio-deltaic environment which was favourable for coal measure development.</p><p>Abnormally abundant gymnosperm-derived diterpanes including labdane, 19-norisopimarane, fichtelite, rimuane, pimarane, isopimarane, 17-nortetracyclic diterpene, phyllocladanes and abietane were detected in the samples analysed. 16<i>a</i>(H)-Phyllocladane was identified unambiguously and kauranes were confirmed to be absent. In addition, three 19-norisopimarane isomers, 13<i>β</i>(H)-atisane, and 20-normethylatisane were tentatively identified in the studied samples. The distributions of n-alkanes, isoprenoids and regular steranes, the presence of 4<i>β</i>(H)-eudesmane and oleanane, high Pr/Ph ratios and the abundant diterpanes together suggest that the hydrocarbons were derived from a coaly source rock. Gymnosperms of the conifer families Cupressaceae (especially the former Taxodiaceae) and Pinaceae are interpreted to be the major source of the diterpanes and to have made a significant contribution to the coaly source rock. However, the low abundance of oleanane relative to diterpanes may underestimate the contribution from angiosperms relative to gymnosperms. This could be due to differential preservation and alteration of the di- and triterpenoid precursors during diagenesis and the occurrence of non-specific precursors in higher land plants.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"43 4","pages":"437-451"},"PeriodicalIF":1.8,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/jpg.12774","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47151705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"NUMERICAL MODELLING OF THE AUSTRALIA – ANTARCTICA CONJUGATE MARGINS USING THE GALO SYSTEM: PART 2. THERMAL AND MATURATION HISTORY OF THE MAWSON SEA BASIN, EAST ANTARCTICA","authors":"Y.I. Galushkin,&nbsp;G.L. Leitchenkov,&nbsp;E.P. Dubinin","doi":"10.1111/jpg.12773","DOIUrl":"10.1111/jpg.12773","url":null,"abstract":"<p>The thermal evolution of the Mawson Sea Basin, offshore East Antarctic, was modelled using the GALO basin modelling programme. As there exist no deep temperature or vitrinite reflectance data for the Mawson Sea Basin, the simulation was based on a limited nonthermal database. This includes the present-day sedimentary section along a multichannel seismic profile which crosses the western part of the Mawson Sea along with geophysical assessments of the depth of the Moho. An analysis of the variations in tectonic subsidence was used to estimate the duration and magnitude of thermal activation or stretching of the lithosphere. This analysis suggested that a proportion of the lithospheric stretching took place before the start of synrift sediment deposition at about 160 Ma (Late Jurassic). This pre-sedimentation lithospheric stretching has been ignored in previous studies, resulting in significant underestimation of the total stretching which has occurred. The analysis also suggests that the thermal maturity of Lower Jurassic potential source rocks along the profile may reach and even exceed the onset of the oil generation window, whereas source rocks in less deeply buried parts of the profile are less mature. In general, the results of the modelling indicate that the Mawson Sea Basin is a promising area for future oil and gas exploration.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"43 4","pages":"419-436"},"PeriodicalIF":1.8,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/jpg.12773","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47173397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Index of editorial contents, JPG vol. 43, 2020","authors":"","doi":"10.1111/jpg.12775","DOIUrl":"10.1111/jpg.12775","url":null,"abstract":"","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"43 4","pages":"454-457"},"PeriodicalIF":1.8,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/jpg.12775","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48584297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"HYDROCARBON MIGRATION AND CHARGE HISTORY IN THE KARANJ, PARANJ AND PARSI OILFIELDS, SOUTHERN DEZFUL EMBAYMENT, ZAGROS FOLD-AND-THRUST BELT, SW IRAN","authors":"M. Vatandoust,&nbsp;A. Faghih,&nbsp;S. Asadi,&nbsp;A. M. Azimzadeh,&nbsp;B. Soleimany","doi":"10.1111/jpg.12769","DOIUrl":"10.1111/jpg.12769","url":null,"abstract":"<p>This study investigates the charge history of the Oligocene – Lower Miocene Asmari Formation reservoir at three oilfields (Karanj, Paranj and Parsi) in the southern Dezful Embayment, SW Iran, from microthermometric analyses of hydrocarbon-bearing fluid inclusions. The Asmari Formation reservoir was sampled in seven wells at depths of between 1671.5 and 3248.5 m; samples from three of the wells were found to be suitable for fluid inclusion analyses. The samples were analyzed using an integrated workflow including petrography, fluorescence spectroscopy, Raman microspectroscopy and microthermometry. Abundant oil inclusions with a range of fluorescence colours from near-yellow to near-blue were observed. Based on the fluid inclusion petrography, fluorescence and microthermometry data, two episodes of oil charging into the reservoir were identified: 7 to 3.5 Ma, and 3.5 to 2 Ma, respectively. Fluid inclusions in general homogenized at temperatures between 112 and 398°C and with salinities of 14 to 23 wt.% NaCl equivalent. Based on the burial history, the Albian Kazhdumi and Paleogene Pabdeh Formation source rocks in the study area have not reached the gas generation window. The abundant fluid inclusions containing gas-liquid phase observed in the Asmari samples studied are therefore inferred to have been derived from secondary oil-to-gas cracking which resulted from Late Pliocene uplift.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"43 3","pages":"341-357"},"PeriodicalIF":1.8,"publicationDate":"2020-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/jpg.12769","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44162165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"UNRAVELLING THE COMPLEXITY OF THIN (SUB-SEISMIC) HETEROGENEOUS CARBONATE RESERVOIRS: AN INTEGRATED STUDY OF THE ALBIAN MAUDDUD FORMATION IN THE GREATER BURGAN AREA, KUWAIT","authors":"B. Vincent,&nbsp;O. Al-Zankawi,&nbsp;I. Hayat,&nbsp;J. Garland,&nbsp;P. Gutteridge,&nbsp;S. Thompson","doi":"10.1111/jpg.12765","DOIUrl":"10.1111/jpg.12765","url":null,"abstract":"<p>The Albian Mauddud Formation is a prolific reservoir in Kuwait and nearby countries such as Iraq and Iran but has received far less attention than the under- and overlying units (the Aptian Shu'aiba and Cenomanian Mishrif Formations). Detailed reservoir characterization studies of the formation are required to support field development and improved / enhanced oil recovery (EOR) programmes. In this study, 26 wells penetrating the Mauddud Formation within the Greater Burgan area of Kuwait (Burgan and neighbouring fields) were investigated, integrating the logging of 910 ft of core with petrographic investigations of 113 stained and impregnated thin sections. In the Greater Burgan area, the Mauddud Formation can be divided into a lower Clastic Member and an upper Carbonate Member which is the main focus of this paper. The primary objective of the study was to present a new characterization of this thin, heterogeneous carbonate reservoir by integrating facies analysis and sequence stratigraphy with a detailed petrographic investigation. A second objective was to identify the relative importance of depositional characteristics and diagenesis on the distribution of reservoir properties.</p><p>Sandstones in the Clastic Member of the Mauddud Formation were deposited on a delta which passed laterally to the north and east into a carbonate platform. During subsequent regional flooding, increased carbonate production resulted in the development of a larger-scale carbonate platform covering the entire study area. The Burgan field area was part of the proximal zone of this carbonate platform. A number of depositional environments were identified by integrating core and thin section data. These range from outer platform to mid- and inner platform, the latter including both high- and low-energy settings (shoal, shoreline; and lagoonal respectively). Mud-supported textures characteristic of low-energy inner-platform and mid- to outer-platform settings are volumetrically dominant in the Mauddud Carbonate Member.</p><p>Sequence stratigraphic analysis suggests that the Mauddud Carbonate Member is part of a major regressive phase (or highstand systems tract) of a third-order sequence, with the regional-scale K110 MFS positioned close to the transition with the underlying Clastic Member. Two 4^th order transgressive – regressive (TR) cycles or sequences, M1 and M2, were identified within the Carbonate Member. The top-Mauddud surface corresponds to a sequence boundary with long-lasting subaerial exposure during the latest Albian and is characterized by both micro- and macroscopic karst features (calcite dissolution vugs and recrystallization in thin sections; and cavities in cores). This study demonstrates that the Burgan field area experienced significant uplift, with increased differential erosion and/or non-deposition of the upper M2 TR cycle towards the southwest.</p><p>Eogenetic marine and meteoric calcite cements partially fill macropores close to t","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"43 3","pages":"249-276"},"PeriodicalIF":1.8,"publicationDate":"2020-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/jpg.12765","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49226304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PETROLEUM SYSTEMS OF THE BONGOR BASIN AND THE GREAT BAOBAB OILFIELD, SOUTHERN CHAD","authors":"Lirong Dou,&nbsp;Dingsheng Cheng,&nbsp;Jingchun Wang,&nbsp;Yebo Du,&nbsp;Gaojie Xiao,&nbsp;Renchong Wang","doi":"10.1111/jpg.12767","DOIUrl":"10.1111/jpg.12767","url":null,"abstract":"<p>The Bongor Basin in southern Chad is an inverted rift basin located on Precambrian crystalline basement which is linked regionally to the Mesozoic – Cenozoic Western and Central African Rift System. Pay zones present in nearby rift basins (e.g. Upper Cretaceous and Paleogene reservoirs overlying Lower Cretaceous source rocks) are absent from the Bongor Basin, having been removed during latest Cretaceous – Paleogene inversion-related uplift and erosion. This study characterizes the petroleum system of the Bongor Basin through systematic analyses of source rocks, reservoirs and cap rocks.</p><p>Geochemical analyses of core plug samples of dark mudstones indicate that source rock intervals are present in Lower Cretaceous lacustrine shales of the Mimosa and upper Prosopis Formations. In addition, these mudstones are confirmed as a regional seal. Reservoir units include both Lower Cretaceous sandstones and Precambrian basement rocks, and mature source rocks may also act as a potential reservoir for shale oil. Dominant structural styles are large-scale inversion anticlines in the Lower Cretaceous succession whilst underlying “buried hill” -type basement plays may also be important. Accumulations of heavy to light oils and gas have been discovered in Lower Cretaceous sandstones and basement reservoirs.</p><p>The Great Baobab field, the largest discovery in the Bongor Basin with about 1.5 billion barrels of oil in-place, is located in the Northern Slope, a structural unit near the northern margin of the basin. Reservoirs are Lower Cretaceous syn-rift sandstones and weathered and fractured zones in the crystalline basement. The field currently produces about 32,000 barrels of oil per day.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"43 3","pages":"301-321"},"PeriodicalIF":1.8,"publicationDate":"2020-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/jpg.12767","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47747278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ORGANIC GEOCHEMISTRY OF MIDDLE MIOCENE (BADENIAN – SARMATIAN) SOURCE ROCKS AND MATURATION MODELLING IN THE POLISH AND UKRAINIAN SECTORS OF THE EXTERNAL CARPATHIAN FOREDEEP","authors":"P. Kosakowski,&nbsp;G. Machowski,&nbsp;A. Kowalski,&nbsp;Y. V. Koltun,&nbsp;A. Zakrzewski,&nbsp;A. Sowiżdżał,&nbsp;M. Stadtmuller","doi":"10.1111/jpg.12766","DOIUrl":"10.1111/jpg.12766","url":null,"abstract":"<p>The Carpathian Foredeep to the north and NE of the Carpathian orogenic belt in SE Poland and NW Ukraine is divided into internal and external sectors. In the narrow internal foredeep, Lower and Middle Miocene shales, sandstones and interbedded evaporites are tightly folded. By contrast the external foredeep is characterized by the presence of a thick, unfolded Middle Miocene molasse succession. This ranges in thickness from a few hundred metres in the north of the external foredeep to &gt;5000 m in the south, near the Carpathian thrust front. Middle Miocene sandstones in the external foredeep form a major reservoir for biogenic gas at fields in Poland and Ukraine.</p><p>The Middle Miocene molasse succession in the external Carpathian Foredeep also contains organic-rich intervals which have source rock potential. For this paper, core samples (n = 670) of Badenian and Sarmatian mudstones from 43 boreholes in the Polish sector of the external foredeep were analysed to investigate their organic geochemistry and hydrocarbon potential. Results show that the samples analysed in general have low to fair (but locally high) total organic carbon (TOC) contents which range up 4.6 wt.% although the average is only 0.7 wt.%. Rock-Eval (S₁+S₂) values are poor to fair and the hydrogen index is also low with a mean value of less than 100 mg/g TOC. The samples analysed are dominated by gas-prone Type III kerogen and this is consistent with previous studies of time-equivalent samples from the Ukrainian part of the external foredeep. The organic matter is in general thermally immature and is interpreted to have been deposited in anoxic and/or sub-oxic conditions. However in the Polish part of the external foredeep, thermal maturities may locally reach the initial phase of the oil window where the Middle Miocene source rocks have been buried deeply beneath the Carpathian thrust front.</p><p>The burial history and thermal evolution of the Middle Miocene succession were reconstructed by means of 1-D modelling at nine boreholes located in both the Polish and Ukrainian parts of the external Carpathian foredeep. The modelling indicated that Middle Miocene source rocks have only entered the initial phase of the oil window locally where they are buried beneath the flysch nappes of the Carpathian foldbelt. At these locations the generation of thermogenic gas may have begun at depths of more than 3 km. However, Middle Miocene source rocks are still immature at depths of &gt;4000 m in some boreholes in the Ukrainian part of the study area. The absence of accumulations of thermogenic natural gas is consistent with the observed low levels of source rock maturity.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"43 3","pages":"277-300"},"PeriodicalIF":1.8,"publicationDate":"2020-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/jpg.12766","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48822978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"NUMERICAL MODELLING OF THE AUSTRALIA – ANTARCTICA CONJUGATE MARGINS USING THE GALO SYSTEM: PART 1. THE BREMER SUB-BASIN, SW AUSTRALIA","authors":"Y. I. Galushkin,&nbsp;G. L. Leitchenkov,&nbsp;E. P. Dubinin","doi":"10.1111/jpg.12768","DOIUrl":"10.1111/jpg.12768","url":null,"abstract":"<p>An analysis of variations in the tectonic subsidence of the Bremer sub-basin (offshore SW Australia) since 160 Ma using the GALO numerical basin modelling programme has made it possible both to refine previous models and to estimate the intensity of stretching and thermal activation of the lithosphere. The new model explains the rapid subsidence of the sub-basin and the deposition of the synrift Bremer 1 unit during the initial rift phase in the Late Jurassic (160 to 130 Ma). This phase of extension was accompanied by high heat flows, typical of the axial zones of continental rifts, and lithospheric stretching with a β-factor of about 1.4. Between 130 and 43 Ma, the abnormally low depositional rate and the shallow water depths suggest moderate thermal activation of the mantle and the absence of extension-driven subsidence. However during the Eocene (43 to 37 Ma), the modelling suggests that another phase of intense stretching of the sub-basin lithosphere took place with β = 1.7, explaining both the subsidence and an abrupt increase in water depth from about 50–200 m to nearer 2000 m.</p><p>The high heat flows during the initial stage of rifting and thermal activation during Cenozoic extension contributed to the early generation of hydrocarbons by source rocks in the Bremer 1 unit at the base of sedimentary cover. At the present day, these source rocks are overmature. At the same time, the modelling suggests that generation of light and heavy oil in the overlying Bremer 2 and 3 units has occurred. Source rock intervals in the upper half of the Bremer 3 unit and in the overlying successions are early mature or immature and may have generated minor volumes of hydrocarbons.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"43 3","pages":"323-339"},"PeriodicalIF":1.8,"publicationDate":"2020-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/jpg.12768","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44992220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DIAMONDOIDS AND BASIN MODELLING REVEAL ONE OF THE WORLD'S DEEPEST PETROLEUM SYSTEMS, SOUTH CASPIAN BASIN, AZERBAIJAN","authors":"N. R. J. Goodwin,&nbsp;N. Abdullayev,&nbsp;A. Javadova,&nbsp;H. Volk,&nbsp;G. Riley","doi":"10.1111/jpg.12754","DOIUrl":"10.1111/jpg.12754","url":null,"abstract":"<p>The South Caspian Basin has been one of the world's most prolific petroleum provinces since the 19th Century. However, despite the large number of discovered petroleum accumulations, the source rock sequence has not been penetrated by the drill in the offshore basin and is therefore poorly defined. In this paper, geochemistry together with broad estimates of in-place volumes of petroleum fluids, onshore outcrop data and basin modelling have been used to place constraints on the source rock description.</p><p>Diamondoids, the most thermally stable group of hydrocarbons, have been measured in a suite of liquid petroleum samples from Pliocene fluvio-deltaic sandstone reservoirs at the Shah Deniz gas-condensate field and the Azeri-Chirag-Gunashli oil field, offshore Azerbaijan. Samples from both fields exhibit elevated concentrations of diamondoids and C₂₉ steranes, indicating a mixture of thermally cracked and non-cracked petroleum. We use diamondoid concentrations to estimate that 4.8 B brl of oil may have been cracked to 12 Tcf of gas below the Shah Deniz reservoirs. Source rock properties from the outcropping Oligocene – Miocene Maikop and Diatom Formations have been used to model source rock maturation. The results indicate that pre-cracking volumes of petroleum could be explained reasonably by the presence of source rock intervals in the offshore that are of similar richness but increased thickness compared to measured onshore outcrops.</p><p>Relatively high diamondoid concentrations in Shah Deniz condensate (up to 160 ppm 3- + 4-methyldiamantanes) are in agreement with gas isotope compositions (δ¹³C₁ – δ¹³C₃) with respect to thermal maturity. Both parameters indicate the presence of source rock that is at a high level of thermal maturity at a vitrinite reflectance equivalent (VRE) of ca. 1.5–2.0% R_o. Given the low geothermal gradients in the South Caspian Basin (16 – 17°C/km at Shah Deniz) and the relatively high temperatures required for maturation due to rapid, relatively recent burial and heating, the source rock must be buried to depths in excess of 13 km in the Shah Deniz drainage area. In the absence of any evidence of a working Mesozoic petroleum system in the South Caspian Basin, this depth of burial highlights the significant thickness of Paleogene sediments in the offshore basin. Of prolific petroleum-producing basins, only in the deep-water Gulf of Mexico are actively-generating source rocks buried to similar depths.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"43 2","pages":"133-149"},"PeriodicalIF":1.8,"publicationDate":"2020-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/jpg.12754","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46382896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DIAGENETIC CONTROLS ON THE RESERVOIR QUALITY OF TIGHT OIL-BEARING SANDSTONES IN THE UPPER TRIASSIC YANCHANG FORMATION, ORDOS BASIN, NORTH-CENTRAL CHINA","authors":"Penghui Zhang,&nbsp;Yong Il Lee,&nbsp;Jinliang Zhang","doi":"10.1111/jpg.12759","DOIUrl":"10.1111/jpg.12759","url":null,"abstract":"<p>Tight oil-bearing sandstones in the Chang 4+5, 6 and 7 Members of the Upper Triassic Yanchang Formation in the Ordos Basin, north-central China, in general consist of fine-grained, moderately- to poorly-sorted lithic arkoses (average Q₅₃F₃₀R₁₇) deposited in a fluvial-dominated lacustrine-deltaic environment. Diagenetic modifications to the sandstones include compaction and cementation by calcite, dolomite, ankerite, quartz, chlorite, kaolinite and illite, as well as partial dissolution of feldspars and minor rock fragments. Porosity ranges up to ~7% of the rock volume and was reduced more by cementation than by compaction. Fractures (tectonic macrofractures and diagenetic microfractures) provide important oil migration pathways and enhance the sandstones' storage potential. The pore network is heterogeneous due to processes related to deposition and diagenesis, and there are considerable spatial variations in porosity and pore connectivity. The pore system includes both macropores and micropores, and pore network variations depend on the type and distribution of authigenic cements.</p><p>An analysis of the diagenetic and porosity characteristics of core samples of the Yanchang Formation sandstones from wells in the Youfangzhuang oilfield resulted in the recognition of six petrofacies (A-F) whose characteristics allow reservoir quality to be predicted. Fluid performance analysis for selected sandstone samples using nuclear magnetic resonance combined with helium porosity and air permeability shows that high permeability and large pore throats together result in high movable fluid saturation potential, and that effective pore spaces and throats are beneficial for hydrocarbon storage and flow. Relatively higher porosity and permeability tend to occur in petrofacies B sandstones containing abundant pore-lining chlorite with lesser kaolinite and minor carbonate cements, and in petrofacies C sandstones with abundant pore-filling kaolinite cement but little chlorite and carbonate cements. These petrofacies represent the best reservoir-quality intervals.</p><p>A reservoir quality prediction model is proposed combined with the petrofacies classification framework. This model will assist future development of tight sandstone reservoirs both in the Upper Triassic Yanchang Formation in the Ordos Basin and elsewhere.</p>","PeriodicalId":16748,"journal":{"name":"Journal of Petroleum Geology","volume":"43 2","pages":"225-244"},"PeriodicalIF":1.8,"publicationDate":"2020-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/jpg.12759","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41855791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}