Oil & Gas Geology ›› 2005, Vol. 26 ›› Issue (4): 530-536.doi: 10.11743/ogg20050422

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Discriminant model of geochemical prospecting for shallow and Medium depth gas reservoirs in western Sichuan

Tang Yuping1,2, Liu Yunli2, Zhao Yaowei2, ChenYinjie2, Chen Zhechun2   

  1. 1. Chengdu University of Technology, Chengdu, Sichuan;
    2. Wuxi Institute of Petroleum Geology, Exploration and Production Research Institute, SINOPEC, Wuxi, Jiangsu
  • Received:2005-04-21 Online:2005-08-25 Published:2012-01-16

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Abstract:

For the Shaximiao Formation reservoirs in western Sichuan,both the concentration indexes(such as the methane,propane and heavy hydrocarbon of headspace analysis,the methane,propane and heavy hydrocarbon of acidolysis-hydrocarbon analysis,and the fluorescence 320 nm and 360 nm) and the ratio indexes(such as headspace humidity coefficient,headspace propane/methane,acidolysis hydrocarbon humidity coefficient,acidolysis hydrocarbon propane/methane,and fluorescence 360 nm/320 nm and 405 nm/320 nm),are obviously higher than that in Penglaizhen Formation reservoirs.Decrease or positive gradient of hydrocarbon concentrations are noticeable,suggesting that hydrocarbon vertical micro-migration do occur.The 3D fluorescence spectrum of natural gas in Shaximiao Fm reservoirs has apparent T2 peak,the pattern of which is relatively complex and is remarkably different with that in Penglaizhen Fm reservoirs.Based on graph theory,fuzzy cluster,factor analysis,nonlinear mapping and correspondence analysis,the reservoir rocks in Penglaizhen and Shaximiao Formations can be divided into two types.They have a good natural grouping features and identifiabiliity.Discriminant model built on Fisher Criteria demonstrates that the function of headspace methane is the largest,indicating that headspace methane is very important in identifying gas reservoirs in the well by geochemical prospecting.

Key words: oil and gas geochemical prospecting, discriminant model, western Sichuan

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