Beijing petroleum geology symposium 1984

Beijing Petroleum Geology Symposium 1984 20-25 September, 1984, Beijing, Peoples Republic of China (Sponsored by China National Oil and Gas Exploration and Development Corporation and Circum Pacific Energy and Mineral Resources Council)

Despite the fact that China is a significant oil producer, comparatively little is known outside China of the geology of the hydrocarbon-bearing basins onshore or indeed the geological and geophysical techniques developed by China to explore for hydrocarbons. The Beijing Petroleum Geology Symposium was the first open conference where results of Chinese exploration onshore and offshore were presented to a joint Chinese and foreign audience. Around 59 papers (34 Chinese, 25 foreign) were presented and the meeting was attended by about 300 scientists, of whom more than 200 were Chinese. To facilitate discussion, preprints of all Chinese papers were provided in English and all the papers were presented in English. Difficulties in making visual aids had been overcome by the Chinese to a great extent, resulting in a uniformly high standard of presentation. During the first day of the Conference, invited review and keynote papers were presented by Chinese and foreign speakers. The remainder of the Conference was divided into three parallel workshop sessions dealing with 'New frontiers, new theories and new methods'. This a~rangement was disappointing as very few speakers kept to time and changes from one workshop to another simply proved impractical. The meeting concluded with an open forum discussion session in each of the workshops to allow an overview of papers presented in the workshop. In the plenary session. Yah Dunshi (Chief Geologist, Ministry of Petroleum) presented a review of the zonation of oil-bearing regions and the main types of oil and gas accumulation in China. His paper reviewed the postTriassic tectonic evolution of China, discussed the distribution and types of sedimentary basin and concluded with comments on source rock types, volume and trapping mechanisms. In a more general paper, A. E. Owen (Berea Oil and Gas Corporation) discussed 'A new strategy for improving exploration incentives in developing countries', emphasizing the importance of economic controls on exploration strategy and investment. In a complementary paper to that of Yah Dunshi, Zhai Guangming et ~i. (Chief Geologist. China Pet-

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roleum Corporation) discussed 'Characteristics of sedimentary basins in China and oil and gas distribution noting the potential of marine source rocks and the types of trapping mechanisms developed in the different basins'. R. Till (British Petroleum) presented a keynote review of the state of the art in 'Computer based information systems as an aid to exploration'. Zhang Wanyou (Academica Sinica) discussed 'The types of Mesozoic and Cenozoic basins and prospects of hydrocarbons in China and the adjacent sea area' in t e r m s of t e c t o n i c h a b i t a t a n d palaeogeography. In a more detailed paper, Liu Guangding (Ministry of Geology) presented a review of 'The geological structure of the East China Sea and its oil and gas bearing properties', of especial interest in view of the current exploration activity in South China Sea; several depocentres containing up to 10 km of sediment deposited in an extensional setting are present. Extensional basins onshore China were discussed in a paper by Hu Jianyi (Vice Director, Scientific Research Institute of Petroleum Exploration and Development) in a paper entitled 'StratigraphicLithologicat hydrocarbon pools in continental basins, China' that included a review of play types in fluviatilelacrustme sequences developed in Mesozoic and Cenozoic rift systems. A paper entitled 'Communications and exploration synergism' by J. H. Silcox (Chevron) dealt with the rather obvious need for communication between and by explorers. S. M. Lane (Gaffney, Cline and Associates), in a much more relevant paper, discussed 'The multidisciptinary techniques to evaluate the economic potential of margin oil fields' - a subject of considerable relevance to South East Asia. The 'New frontiers worKsiaop' was opened with a paper by E. P. Padfield et al. (Occidental) on Occidental's Cano Lmton Discovery in the Llanos Basin, Columbia: 32 wells were drilled prior to the successful discovery of a billion barrel plus field. Ma Li (Deputy Chief Geologist, Daqing Oilfield) discussed oil and gas-bearing reservoirs in the Daqing Oilfield, Songliao Basin. In a paper dealing with exploration offshore N.E. China, A. Matsuzawa (Japan

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National Oil Corporation) discussed 'Oil and gas exploration in Bohai Bay'; despite several successful wells, considerable problems beset field development in this area. A companion paper by Zheng Changming et al. (Chief Geologist, Liao He Oilfield) discussed fault block development and onlap traps, called 'buried hill traps', in another part of the Bohai Bay Basin, An important paper by J. Cousteau et al. (ELF, Paris) discussed heavy oil geochemistry, migration and recovery. The 'Formation of three oil fields in Jizhong Sag' was documented by Wua Hua-yuan e t a l . (Chief Geologist, North China Petroleum Exploration) with reference to reservoir facies distribution, timing of migration and trap formation. Shuai Defu e t a l . (Deputy Chief Geologist, Shengli Oilfield) discussed structural-stratigraphic trap development in the Liyang depression. V. G. Swindon (CSR Ltd, Australia) reviewed the exploration and production history of the Eromanga Basin, Central Australia. This area is considered to be the most prospective area of onshore Australia but has a low exploration density, despite major gas reserves and some oil. Yia Zhan reviewed the petroleum prospects of the marine sediments of South China; Sinian to Middle Triassic carbonates have good source potential but are generally overmature for oil. A more academic paper by I-t. G. Greene et al. (USGS, Menlo Park, USA) reviewed the 'Oil and gas potential of Island arcs in the SW Pacific: a new frontier'. A paper of con3iderable interest to foreign attendees entitled 'Sedimentary basins and hydrocarbon potential of the continental shelf of China' was presented by Qiao Hansheng et al. (Scientific Research Institute of Petroleum Exploration) and discussed the main basin types, geothermal gradients and tectonism in the South Yellow Sea region. R. B. Halley et al. (Phillips Petroleum, USA) reviewed the diagenesis of Perrnian shelf edge carbonates in the IJSA. Reservoir development in the Gulf of Hainan was discussed by G. P. Allen et al. (Total, Bordeaux, France); the reservoirs are alluvial fan and channel sediments whose properties are downgraded by muddier debris flows and

subsequent diagenetic alteration. Song Gochu (Chief Engineer, Changquing Petroleum Bureau) presented a paper on 'The unusual Jurassic palaeogeomorphologic oil fields in the Sanganning Basin'; these fields are developed in an alluvial drainage system in an incised pre-Jurassic topography. More regional aspects of basin development were discussed by D. G. Roberts (BP, London) in a paper that considered the hydrocarbon habit of South East Asian basins in a tectonic context. Tectonics and seismic interpretation were also highlighted by Xie Hong et al. (Chief Geologist, Xinjiang Petroleum Administration) in a structural analysis of the thrust belt in the Zhungaria Basin. The gas potential of coals in the Dong Pu depression in the North China Basin was analysed using carbon and Argon isotopes to pin down source rock types (Zhu Jiawei et al.). A relevant seismo-stratigraphic study of 'Reefs in the South China Sea' was presented by Hao Fuguang (China National Offshore Oil Corporation). The New Frontiers Session was concluded with an open discussion, question and answer session in which Chinese and foreign attendees keynoted particular points to encourage what proved to be a stimulating discussion. Papers in the 'New theories workshop' dealt with a wide variety of

geochemical, sedimentological problems. Papers of key relevance to Chinese onshore exploration that drew on experience in the USA and Australia were presented by P. Verrall (Chevron, USA) and T. G. Powell (Bureau of Mineral Resources, Australia), respectively. Verrall reviewed the structural evolution of the Wyoming thrust belt and Powell discussed the geochemistry of lacrustine source rocks. Source rock types and their geochemistry were also discussed by Huang Difan et al. (Scientific Research Institute of Petroleum Exploration) and Fu Jiamo. Novel uses of argon and carbon isotope to identify source rocks were presented by Xu Yongchang (College of Geology, Beijing). Chen Heli (Beijing Geological Institute) discussed the influence of compaction and pore pressure on primary hydrocarbon migration. Papers dealing with sedimentology ranged from entirely relevant papers dealing with the diagenesis and timing of oil migration (Liu Shuhi-ui et al., Beijing College of Geology) and Permo Carboniferous reservoir facies analysis in South China (Li Xuchui, Beijing College of Geology) to papers of questionable relevance that discussed 'Unusual calcite cementing of quartz grains' (H. Mitchell, Tapping, Sun-Orient Exploration, Zhanjiang, China). Li Chunju (Nanyang Oilfield), in a paper relevant

to onshore and offshore exploration, discussed the sedimentology of alluvial fan deltas in the Tertiary rift basin (Biyang). In the 'New methods workshop' papers varied considerably in content and relevance. Papers dealing with seismic statigraphy were presented by Chinese and foreign participants. Seismic processing, and particularly more advanced techniques, were reviewed in five separate papers. An excellent paper by R. J. Morris (Shell, Hague, Netherlands) discussed prospect evaluation based on calibrated geological m o d e l l i n g - an effective simulation model that allows meaningful statistical prediction of the outcome of yet-to-be drilled prospects. Other papers in this session dealt with well logging, remote sensing and new exploration techniques that utilized large-aperture seismic systems and multibeam sonars as exploration tools. The Beijing Petroleum Conference was a welcome public first step in an already well established but private dialogue between Chinese and foreign colleagues. Papers dealing with Chinese petroleum geology are of particular interest in their own right as well as novel case histories. It is to be hoped that the initiative established by this conference will continue in the future.

The Caribbean-South America Plate Boundary and Regional Tectonics Editors W. E. Bonini, R. B. Hargreaves and R. Shagam Geological Society of America Memoir 162, 1984. 421 pp. Published by the Geological Society of America, Boulder, Colorado, USA [ISBN 0-8137-1162-2] Although the evolution of the major ocean basins has been deciphered in at least broad terms, the geological history of the ostensibly better known Caribbean Sea and its borderlands has remained both enigmatic and controversial. This is because the pivotal position occupied by the Caribbean, between North and South America since the break up of the Pangaea in Mid-Jurassic time has resulted in great geological complexity. Within this pivotal area, a complex history of obduction, accretion, translation and extension is recorded in the geology of the Caribbean borderlands as well as in the adjoining deep seafloor. The present day geology of those areas then represents the integrated products of these processes in space and time. Deciphering the geology of the Carib-

bean area to recognize common processes and thereby understand the spatially ordered geometry and timing of plate movements that have formed the geological record requires multidisciplinary geological and geophysical studies of both the onshore and offshore. Very few such studies have been attempted although the palaeogeographic atlas of Cook and Bally (1975) and the reviews contained in Nairrn and Stehli's 'The Gulf of Mexico and Caribbean' (1975) were useful steps. Since then many new approaches to synthesizing and analysing regional tectonics have been developed. Memoir 162 presents a variety of papers dealing specifically with a key area of Caribbean geology, the Caribbean-South America plate boundary. The editors have collected a series of papers dealing with many relevant

aspects of Caribbean geology from regional plate tectonic models to brief papers keynoting very specific geochronologic or palaeomagnetic studies. However, the book is a disappointment in some respects. Despite its title, twenty of the twenty eight papers in the volume deal with Venezuela. There are no papers on the very relevant geology of Trinidad and only two papers on Colombia. Other than briefly in the regional syntheses, no one paper addresses the relationship between Colombia and Central America. Disappointingly, only two papers address the offshore geology of northern South America. Indeed, the dominance of papers (one third) by graduates of the Princeton research school is possibly a reflection of the interests of the editors. A broader perspective of work done in

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