Oil & Gas Geology ›› 2013, Vol. 34 ›› Issue (1): 124-128.doi: 10.11743/ogg20130117

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Analysis on oil well productivity of low-permeability reservoirs with stress-sensitivity being taken into considerations

Liu Feng1, Wang Yuliang2, Chen Xiaofan1, Su Yunhe3, Wang Yue1   

  1. 1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploration, Southwest Petroleum University, Chengdu, Sichuan 610500, China;
    2. Directory Well Drilling Service Company, CNPC Xibu Drilling Engineering Company Limited, Urumqi, Xinjiang 830026, China;
    3. Langfang Branch, PetroChina Exploration and Development Research Institute, Langfang, Hebei 065007, China
  • Received:2012-09-24 Revised:2012-12-26 Online:2013-02-28 Published:2013-03-18

Abstract:

Stress-sensitivity is one of the main factors that affect single well productivity in low-permeability rese-rvoirs.It is common sense that wells tend to produce less after certain volumes of reservoir fluids were recovered as that would cause drop-down in formation pressure,porosity and permeability and increase of effective stress.The authors modified the previous productivity function of low-permeability oil wells that only considers the influences of permeability decrease by incorporating the influences of stress on porosity,established a new stress-sensitive productivity function with both porosity and permeability being taken into consideration,and proposed the concept of productivity-stress-sensitivity index.Along with the intensifying of stress-sensitivity of low-permeability reservoirs and increase of stress-sensitivity constant,the productivity-stress-sensitivity index also enlarges,and daily oil production quickly shrinks.The new function simplifies the calculation process and improves the accuracy.Practices show that the productivity-stress-sensitivity index exerts a strong influence upon the productivity of wells in low-permeability reservoirs.As the index increases,the decreasing of open flow capacity of oil wells slows down.Compared with the old function,the new one reflects better the actual production of low-permeability reservoirs and therefore could be used to guide their development.

Key words: stress sensitivity, productivity, porosity, permeability, low-permeability reservoir

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