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The process and mechanisms of secondary hydrocarbon migration in the Huixi half-graben, Pearl River Mouth Basin, were investigated on the basis of geological analysis of the strata and study of the porosity and permeability of the reservoir rocks, fluid potential, oil properties, and geochemistry of oil-source correlation. The results suggest that the hydrocarbons of the Zhujiang Formation in the Huixi half-graben were derived from source rocks of the Eocene Wenchang Formation and the Eocene-Oligocene Enping Formation in the Huizhou Sag. The hydrocarbons migrated laterally from northeast to southwest. The sandstone in the upper member of the Zhujiang Formation exhibited superior physical properties (porosity and permeability) and connectivity than the lower member. Thin sandstone beds with good physical properties and stable distribution in the upper member of the Zhujiang Formation were the main carrier beds for lateral hydrocarbon migration. Les processus et les mecanismes de migration secondaire des hydrocarbures dans le demi-graben d'Huixi, dans l'embouchure du bassin de la riviere Pearl, ont ete etudies en se basant sur l'analyse geologique des strates et la determination de la porosite et de la permeabilite des roches reservoir, le potentiel de fluides, les proprietes du petrole et la geochimie de la correlation petrole-source. Selon les resultats, les hydrocarbures de la Formation de Zhujiang dans le demi-graben d'Huixi proviendraient des roches-meres de la Formation de Wenchang (Eocene) et de la Formation d'Enping (Eocene-Oligocene) dans l'affaissement d'Huizhou. Les hydrocarbures ont migre lateralement du nord-est au sud-ouest. Le gres dans le membre superieur de la Formation de Zhujiang presentait de meilleures proprietes physiques (porosite et permeabilite) et une meilleure conductivite que le membre inferieur. De minces lits de gres avec de bonnes proprietes physiques et une distribution stable dans le membre superieur de la Formation de Zhujiang constituaient les principaux lits reservoirs pour la migration laterale des hydrocarbures. [Traduit par la Redaction], Introduction Hydrocarbon migration, which connects the processes of hydrocarbon generation and final accumulation, has been a matter of interest in petroleum geology for many years (Magoon and Dow 1994). However, [...]

Seven hydrocarbon reservoirs have been discovered to date in the Upper Ordovician of the Tazhong Area, a region in which hydrocarbon phase distribution is complex. In the present study, the genesis and controlling factors of the hydrocarbons with complex phase in the Tazhong Area were investigated on the basis of the geological and geochemical conditions required for the formation and distribution of hydrocarbon reservoirs, integrated with the source rock geochemistry, natural gas and oil properties, and oil and gas reservoir fluid tests PVT (i.e., pressure, volume, and temperature tests). The results indicate that hydrocarbon reservoir types in the Upper Ordovician of the Tazhong Area transition from unsaturated to saturated condensategas reservoirs from west to east and from condensate-gas reservoirs to unsaturated-oil reservoirs from north to south. The crude oil in the region originated primarily from the mixing of Lower-Middle Cambrian and Middle-Upper Ordovician source rocks, while the natural gas was sourced primarily from the cracking gas of Lower-Middle Cambrian crude oil. This hydrocarbon-phase distribution was controlled primarily by temperature and pressure and has been affected by multiple periods of hydrocarbon accumulation and alteration. The high-quality Lower-Middle Cambrian reservoir-cap assemblage may be an important target for future exploration of natural gas in the Tazhong Area. A ce jour, sept reservoirs d'hydrocarbures ont ete decouverts dans l'Ordovicien superieur du secteur Tazhong, une region dans laquelle la distribution des phases d'hydrocarbures est complexe. Dans la presente etude, la genese et les facteurs controlant les hydrocarbures a phases complexes dans le secteur de Tazhong ont ete analyses en se basant sur les conditions geologiques et geochimiques necessaires pour la formation et la distribution de reservoirs d'hydrocarbures; ces donnees ont ete integrees avec la geochimie et les proprietes du gaz naturel et du petrole de la roche mere ainsi qu'avec les essais PVT (pression, volume et temperature) effectues sur les fluides des reservoirs de petrole et de gaz de la roche mere. Les resultats indiquent que les types de reservoirs d'hydrocarbures dans l'Ordovicien superieur du secteur de Tazhong passent de reservoirs de condensat de gaz non satures a satures, d'ouest en est, et de reservoirs de condensat de gaz a des reservoirs non satures de petrole du nord vers le sud. Le petrole brut de la region tire son origine surtout du melange de roches meres du Cambrien inferieur moyen et de l'Ordovicien moyen superieur alors que le gaz naturel provient surtout du gaz de craquage du petrole brut du Cambrien inferieur moyen. Cette distribution de phases d'hydrocarbures a ete controlee principalement par la temperature et la pression et elle a ete affectee par de multiples periodes d'accumulation et d'alteration des hydrocarbures. La grande qualite de l'assemblage de la couverture du reservoir Cambrien inferieur moyen pourrait etre une cible importante pour l'exploration future de gaz naturel dans le secteur de Tazhong. [Traduit par la Redaction], Introduction The types, distribution, and main controlling factors of hydrocarbon fluid phases need to be investigated to assess and explore hydrocarbon resources (Zhou 2004). The oil and gas reservoir fluid [...]

The Bozhong Sag is the biggest hydrocarbon rich sag in the Bohai Sea area. However, hydrocarbon resource potential and its distribution are not clear, which restricts petroleum exploration. According to the material balance principle and the hydrocarbon accumulation threshold theory, the resource potential and distribution characteristics of hydrocarbons were evaluated quantitatively with hydrocarbon accumulation systems as evaluation units. The upper and lower plays in the Bozhong Sag and surrounding areas each can be divided into six hydrocarbon accumulation systems. The total afforded accumulation hydrocarbon quantity in the Bozhong Sag and surrounding areas is 60.265×108 t of oil (43.185×108 t in the upper play, 17.080×108 t in the lower play) and 27.03×1011 m3 of gas (17.76×1011 m3 in the upper play and 9.27×1011 m3 in the lower play). The Shijiutuo (I) and Bodong (II) accumulation systems are the further exploration areas with the greatest afforded accumulation hydrocarbon quantity. Key words: Bozhong Sag, hydrocarbon accumulation system, hydrocarbon accumulation threshold, hydrocarbon accumulation quantity, resource evaluation

Over 70% of China's domestic oil production is obtained from 9 giant oilfields. Understanding the behaviour of these fields is essential to both domestic oil production and future Chinese oil imports. This study utilizes decline curves and depletion rate analysis to create some future production outlooks for the Chinese giant oilfields. We can conclude that China's future domestic oil production faces a significant challenge caused by maturing and declining giant fields. Evidence also indicates that the extensive use of water flooding and enhanced oil recovery methods may be masking increasing scarcity and may result in even steeper future decline rates than the ones currently being seen. The Chinese petroleum industry has managed to keep many of their giants on a production plateau for many decades. However, nothing can change the eventual onset of decline in oilfields and many of the Chinese giants have already passed their peak production levels. Our results suggest that a considerable drop in oil production from the Chinese giant oilfields can be expected over the next decades. 摘要: 中国国内超过70%的原油产量来自于9个大油田。掌握这些油田的动态对于了解中国国内原油产量和未来中国原油进口需求是必要的。该研究利用递减曲线和采油速度分析，得出中国大油田未来产量的走势。研究表明，中国国内未来原油产量将会面临一个巨大的挑战，而这正是由大油田的成熟和递减引起的。证据也表明，水驱和提高采收率方法的大规模运用将会掩盖日益严重的资源缺乏，并可能会导致油田未来递减率比目前所见到的递减率更大。中国石油工业已经设法使其国内大油田的产量在几十年内保持稳定，但任何措施都无法阻止这些油田最终走向递减，且中国许多大油田已经过了峰值产量期进入递减。笔者认为，在未来几十年里，中国大油田的原油产量将大幅降低。 Key words: giant oilfields, future Chinese oil production, decline curve analysis, production modelling, oil production strategy

Jurassic strata along the southern margin of Junggar Basin are important petroleum system elements for exploration in northwest China. The Lower and Middle Jurassic source rock effectiveness has been questioned as exploration progresses deeper into the basin. These source rocks are very thick and are distributed widely. They contain a high total organic carbon composed predominantly of Type III kerogen, with some Type II kerogen. Our evaluation of source rock petroleum generation characteristics and expulsion history, including one-dimensional basin modeling, indicates that Jurassic source rocks are gas prone at deeper depths. They reached peak oil generation during the Early Cretaceous and began to generate gas in the Late Cretaceous. Gas generation peaked in the Paleogene-Neogene. Source rock shales and coals reached petroleum expulsion thresholds at thermal maturities of 0.8% and 0.75% vitrinite reflectance, respectively, when the petroleum expulsion efficiency was ~40%. The petroleum generated and expelled from these source rocks are 3788.75 x [10.sup.8] and 1507.55 x [10.sup.8] t, respectively, with a residual 2281.20 x [10.sup.8] t retained in the source rocks. In these tight reservoirs, a favorable stratigraphic relationship (where tight sandstone reservoirs directly overlie the source rocks) indicates short vertical and horizontal migration distances. This indicates the potential for a large, continuous, tight-sand gas resource in the Lower and Middle Jurassic strata. The in-place natural gas resources in the Jurassic reservoirs are up to 5.68 x [10.sup.12]-15.14 x [10.sup.12] [m.sup.3]. Jurassic Badaowan and Xishanyao coals have geological characteristics that are favorable for coal-bed methane resources, which have an in-place resource potential between 3.60 x [10.sup.12] and 11.67 x [10.sup.12] [m.sup.3]. These Lower and Middle Jurassic strata have good shale gas potential compared with active US shale gas, and the inferred in-place shale gas resources in Junggar Basin are between 20.73 x [10.sup.12] and 113.89 x [10.sup.12] [m.sup.3]. This rich inferred conventional and unconventional petroleum resource in tight-sand, coal-bed, and shale gas reservoirs makes the deeper Jurassic strata along the southern margin of Junggar Basin a prospective target for future exploration. Les strates jurassiques le long de la bordure sud du bassin de Junggar constituent des elements importants d'un systeme petrolier exploitable dans le nord-ouest de la Chine. L'efficacite de la roche source (Jurassique inferieur et moyen) a ete mise en question a mesure que l'exploration progressait plus profondement dans le bassin. Ces roches sources sont tres epaisses et couvent de grandes etendues. Leur teneur en carbone organique total est elevee et il est principalement compose de kerogene de type III avec un peu de kerogene de type II. Selon notre evaluation des caracteristiques de generation de petrole a partir de roches souches et de l'historique d'expulsion, incluant une modelisation du bassin a une dimension, ces roches sources du Jurassique devraient contenir du gaz a de grandes profondeurs. Ces roches ont atteint un sommet de generation de petrole durant le Cretace precoce et elles ont commence a produire du gaz au Cretace tardif. La generation de gaz a atteint un sommet au Paleogene-Neogene. Les roches sources de shale et les charbons ont atteint des seuils d'expulsion du petrole a des maturites thermiques respectives de reflectance de la vitrinite de 0,8% et de 0,75%, alors que le taux d'efficacite d'expulsion du petrole est d'environ 40%. Le petrole genere par ces roches est de 3788.75 x [10.sup.8] t et celui expulse est de 1507.55 x [10.sup.8] t; 2281.20 x [10.sup.8] t residuelles sont retenues dans les roches sources. Dans ces reservoirs peu permeables, une relation stratigraphique favorable (lorsque des reservoirs de gres peu permeables reposent directement sur les roches sources) signale de courtes distances, verticales et horizontales, de migration, ce qui en retour indique un potentiel pour une vaste ressource ininterrompue de gaz dans un sable peu permeable de strates du Jurassique inferieur et moyen. Les ressources de gaz naturel in situ dans les reservoirs datant du Jurassique atteignent de 5.68 x [10.sup.12] a 15.14 x [10.sup.12] [m.sup.3]. Les charbons Badaowan et Xishanyao (Jurassique) possedent des caracteristiques geologiques favorables aux ressources de methane de houille, lesquelles ont un potentiel in situ entre 3.60 x [10.sup.12] et 11.67 x [10.sup.12] [m.sup.3]. Ces strates du Jurassique inferieur et moyen ont de bons potentiels de gaz de shale comparativement aux gaz de shale americains exploites, et les ressources in situ inferees dans le bassin de Junggar sont de 20.73 x [10.sup.12] a 113.89 x [10.sup.12] [m.sup.3]. Cette riche ressource de petrole inferee, conventionnelle et non conventionnelle, dans des reservoirs de sables peu permeables, de lits de charbon et de gaz de shale, font des strates jurassiques tres profondes le long de la bordure sud du bassin de Junggar une cible prometteuse pour de l'exploration future. [Traduit par la Redaction], Introduction Junggar Basin is one of the most petroliferous basins in China (Ulmishek 1984; Wang 2000b; Li et al. 2003; Kong 2007; Cao et al. 2012; Shao 2013). By 2010, [...]