Oil & Gas Geology ›› 2013, Vol. 34 ›› Issue (5): 610-618.doi: 10.11743/ogg20130505

• Petroleum Geology • Previous Articles     Next Articles

Geological conditions for hydrocarbon accumulation in middle reservoir-source rock combination of the Ordovician Majiagou Formation on the east side of the paleo-uplift in Ordos Basin

Shi Baohong1, Liu Yanan1, Wu Chunying2, Huang Zhengliang2, Ren Junfeng2   

  1. 1. School of Earth Science and Engineering, Xi'an, Shiyou University, Xi'an Shaanxi 710065, China;
    2. Exploration and Development Research Institute of PetroChina, Changqing Oilfield Company, Xi'an, Shaanxi 710018, China
  • Received:2013-03-24 Revised:2013-08-15 Online:2013-10-08 Published:2013-10-08

Abstract:

The dolomite reservoirs in middle reservoir-source rock combination of the Ordovician Majiagou Formation on the east side of paleo-uplift in Ordos Basin are obviously different from the weathering crust reservoirs at the top of the Ordovician in Jinbian gas field.A systematic study had been carried out on the geological conditions for hydrocarbon accumulation in these dolomite reservoirs in respect of source rocks,reservoirs,sedimentation based on results of reservoir lithology characterization and fluid inclusion testing as well as analysis of drilling data,geochemical and testing data.The results show that the middle reservoir-source rock combination of the Formation experienced strong hydrodynamics against a brief regression sedimentary settings.Beach facies were well developed and formed dolomite reservoirs.The dolomite features in highly automorphic coarse powder and fine-crystal texture,uniform grains,excellent connectivity and well-developed intercrystal pores.Affected by tectonic uplifting during the late Caledonian,the top Ordovician at eastern side of the paleo-uplift were denuded and came into contact with coal-measure source rocks,providing favorable source-reservoir combination.Controlled by lithofacies transformation at updip direction,the dolomites of beach facies in the middle reservoir-source rock combination of the Formation change gradually into micrite,forming discontinuous lithological traps.

Key words: reservoiring condition, middle reservoir-source rock combination, Majiagou Formation, Ordovician, paleo-uplift, Ordos Basin

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