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Stress Sensitivity Experiment under Consideration of Stress Arching Effect |
WANG Fanliao1, LI Xiangfang1, HAN Bin2, ZHANG Xin3, LI Yingying1, ZHAO Jingjing1,4 |
1. MOE Key Laboratory of Petroleum Engineering, China University of Petroleum, Beijing 102249, China;2. Research Institute of Petroleum Exploration and Development in China, Beijing 100083, China;3. Company of China Petroleum in Tuha Oilfield, Hami 839009, Xinjiang Uygur Autonomous Region, China;4. No.1 Oil Production Plant of Jiangsu Oil Field Branch, Sinopec Co., Ltd., Yangzhou 225264, Jiangsu Province, China |
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Abstract: Low Permeability reservoir is quite sensible to the effective stress. Current all sensitive experiments suppose that the overburden pressure is a constant during the production. Actually, during oil and gas exploitation, a stress arching effect comes into play in the overburden, reducing the overburden pressure acting on the reservoir. Based on the theory of the stress arching, the stress-to-arching ratio, overburden pressure, and effective stress expression in Su Lige gas field are calculated. It is the first time that the theory is applied to the stress sensitive experiments. The experiments take the reservoir shape and different range of initial permeability into consideration. The results show that the stress-to-arching ratios are 0.12 and 0.28, respectively for the elliptic cylinder reservoir and penny-shaped reservoir in Su Lige gas field. Comparing with the conventional experiments, under the same condition, the measured permeability is usually higher and the degree of the sensitivity is smaller. When the pressure drops 25MPa, for the stress-arching-ratios of 0.12 and 0.28, the measured permeability are 1.2 and 1.5 times of the permeability value obtained by conventional experiments for the reservoir with low permeability, which initial permeability is smaller than 0.1mD. However, when the initial permeability is between 10mD and 50mD and stress-to-arch ratios are 0.12 and 0.28, respectively, the corresponding permeability are 1.01 and 1.02 times of the permeability got by the conventional experiments. The low permeability gas reservoir is more sensitive to the stress arching than the high permeability gas reservoir.
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Received: 12 December 2012
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