Oil & Gas Geology ›› 2007, Vol. 28 ›› Issue (2): 181-190.doi: 10.11743/ogg20070208

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Quantitative evaluation of fault sealing property with fault connectivity probabilistic method

Zhang Likuan1, Luo Xiaorong1, Liao Qianjin2, Yuan Shuqin1, Su Junqing2, Xiao Dunqing Wang Zhaoming2, Yu Changhua1   

  1. 1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029;
    2. Petroleum Exploration and Development Research Institute of Dagang Oilfield Company Ltd., PetroChina, Tianjin 300280
  • Received:2007-02-08 Online:2007-04-25 Published:2012-01-16

Abstract:

A new quantitative method for evaluating fault sealing properties based on fault connectivity probability is proposed by taking the occurrence of oil and gas in footwall and hangingwall reservoirs of hydrocarbon controlling faults in Chengbei falut step zone of Dagang oilfield as the index of identifying the sealing properties of faults and by taking into consideration many factors that have influence over the properties.Three parameters,i.e.fluid pressure of mudstone,normal stress on fault plane,and clay smear,are regarded as the major factors that influence the sealing properties of faults,and a dimensionless sealing coefficient is defined according to the mechanisms of their influence over the sealing properties of faults.Then typical reservoir profiles crossing faults are selected to calculate sealing coefficients on different parts of the profile and the sealing properties of faults are determined according to the occurrence of oil in the footwall and hanging wall.Furthermore,statistical analysis of the relationship between the sealing coefficients and fault connectivity probability shows that when the coefficient is less than 1.0,the connectivity probability is naught;when the coefficient ranges from 1.0 to 3.5,the relationship between them can be expressed by a quadratic equation;and when the coefficient is more than 3.5,the connectivity probability equals 100%.The connectivity probability contour on a strike projection reveals the sealing properties of different parts on the fault plane.

Key words: fault sealing property, quantitative, sealing coefficient, connectivity probability,Chengbei step-fault zone, Dagang oilfield

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