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| MECHANISM STUDY OF ACID ON MECHANICAL
PROPERTIES OF LIMESTONE |
| HE Chunming，GUO Jianchun |
(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation，Southwest Petroleum University，
Chengdu，Sichuan 610500，China) |
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Abstract Through systematic experiments test includes static rock dissolution experiments，dynamic rock flow experiments，triaxial mechanical tests and microstructure analysis of rocks，the mechanical strength reduction of limestone reacting with different acids were studied from the macroscopic and microcosmic perspective. Static and dynamic dissolution experiments showed that gelled acid could create many small solution caves on the rock face，while viscosity acid was mainly of surface dissolution. triaxial mechanical test indicated that the compression strength of rock was reduced by 18%，and Young?s modulus by 26% after reaction with gelled acid，which was much larger than the mechanic strength reduction that dissolved by viscosity acid. Stress-strain curve showed that the compaction densification process after reaction continued for a long time，and showing more plastic behavior. Scanning electron microscope observation indicated that there were many small dissolution holes in the rock after reacting with gelled acid，while the viscosity acid was mainly of uniform dissolution，which has little damage to the internal structure of rock. The difference of dissolution structure for different acids maybe the fundamental reason for the difference of mechanical strength. For high closure stress reservoirs，it should be care more about the mechanical strength reduction that caused by acid-rock reaction，which means to choose leak off-control acids.
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Received: 05 February 2012
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| [1] BARTKO K M，NASR-EL-DIN H A，RAHIM Z，et al. Acid fracturing of a gas carbonate reservoir：the impact of acid type and lithology on fracture half length and width[C]// SPE Annual Technical Conference and Exhibition. Denver，Colorado：[s. n.]，2003.
[2] GONG M，LACOTE S，HILL A D. New model of acid-fracture conductivity based on deformation of surface asperities[J]. SPE Journal，1998，4(3)：206–214.
[3] NAVARRETE R C，MILLER M J，GORDON J E. Laboratory and theoretical studies for acid fracture stimulation optimization[C]// SPE Permian Basin Oil and Gas Recovery Conference. Midland，Texas：[s. n.]，1998.
[4] ROBERTS L D，HALLIBURTON S D，GUIN J A，et al. A new method for predicting acid penetration distance[J]. Society of Petroleum Engineering Journal，1975，15(4)：277–286.
[5] 蒋卫东，汪绪刚，蒋建方，等. 酸蚀裂缝导流能力模拟试验研究[J].钻采工艺，1998，21(6)：33–36.(JIANG Weidong，WANG Xugang，JIANG Jianfang，et al. Simulation experiment research on acid-etched fracture?s conductivity[J]. Drilling and Production Technology，1998，21(6)：33–36.(in Chinese))
[6] 李小刚，杨兆中，苏建政，等. 酸压过程中多尺度酸岩反应特征试验研究[J]. 石油试验地质，2010，32(5)：504–508.(LI Xiaogang，YANG Zaozhong，SU Jianzheng，et al. Experimental study of multi-scale reaction between acid and rcok in acid fracturing[J]. Petroleum Geology and Experiment，2010，32(5)：504–508.(in Chinese))
[7] NASR-EL-DIN H A，AL-DRIWEESH S M，METCALF A S，et al. Fracture acidizing：what role does formation softening play in production response[J]. SPE Journal，2006，23(2)：184–191.
[8] 丁梧秀，冯夏庭. 化学腐蚀下灰岩力学效应的试验研究[J]. 岩石力学与工程学报，2004，23(21)：3 571–3 576.(DING Wuxiu，FENG Xiating. Testing study on mechanical effect for limestone under chemical erosion[J]. Chinese Journal of Rock Mechanics and Engineering，2004，23(21)：3 571–3 576.(in Chinese))
[9] KARFAKIS M G，ASKRAM M. Effects of chemical solutions on rock fracturing[J]. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts，1993，30(7)：1 253–1 259.
[10] HILL A D，ZHU D，WANG Y. The effect of worm holing on the fluid loss coefficient in acid fracturing[J]. SPE Production and Facilities，1994，10(4)：257–264. |
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2013, Vol. 32 
