Mechanical behaviour of Australian Strathbogie granite under in-situ stress and temperature conditions: An application to geothermal energy extraction
Mechanical behaviour of Australian Strathbogie granite under in-situ stress and temperature conditions: An application to geothermal energy extraction
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DOI：
10.1016/j.geothermics.2016.07.002
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发表时间：
2017-01-01
期刊：
影响因子：
3.9
通讯作者：
Rathnaweera, T. D.
中科院分区：
文献类型：
--
作者：
Kumari, W. G. P.;Ranjith, P. G.;Rathnaweera, T. D.
由于传统化石燃料的使用对全球气候变化造成了严重的环境影响，地热现已被确定为一种有效的可再生能源。然而，由于缺乏知识，特别是对高温高压下储层岩石的地热条件的了解，它的广泛应用受到了限制。高温高压可能导致储层岩石的微观结构和矿物学改变，从而改变储层岩石的力学性质，这是保证地热储层井筒稳定性和对地热储层进行增产改造，实现安全有效地开采地热能的重要属性。因此，本研究通过对澳大利亚Strathbogie花岗岩在4种不同围压（10、30、60、90 MPa）和4种不同温度（RT、100、200、300℃）下进行一系列高压、高温三轴试验，研究了地应力和温度条件下的应力-应变行为。采用先进的声发射（AE）系统研究了温度对三轴条件下岩石试样力学行为的影响，并观察了相应的裂缝扩展行为。通过扫描电镜分析，观察了花岗岩中相应的微观结构变化。研究结果表明，温度升高导致储层岩石强度和剪切参数先升高后降低，这一趋势与岩体裂缝形成模式一致。SEM分析进一步证实了这一点，岩石微观结构在较低温度下仅发生微小变化，而较高温度会导致沿岩体晶界发育微裂纹。此外，传统的Mohr-Coulomb准则无法模拟地热储层条件下岩石的应力-应变响应，因此需要针对相应的原位条件进行修正。(C) 2016 Elsevier Ltd.版权所有。
Geothermal heat has now been identified as an effective renewable energy source due to severe environmental impacts created by conventional fossil usage on global climatic change. However, its wide application has been limited due to the lack of knowledge, particularly of the geothermal conditions of reservoir rocks at elevated temperatures and pressures. Such high temperatures and pressures possibly alter the mechanical properties of reservoir rocks due to the associated micro-structural and mineralogical alterations of the rock mass, which are an important attribute for wellbore stability and stimulation of geothermal reservoirs for safe and effective geothermal energy extraction. This study therefore investigates the stress-strain behaviour under in-situ stress and temperature conditions by conducting a series of high-pressure, high-temperature tri-axial experiments on Australian Strathbogie granite under four different confining pressures (10, 30, 60, 90 MPa) and four different temperatures (RT, 100, 200, 300 degrees C). The effect of temperature on the mechanical behaviour of rock specimens was studied under tri-axial conditions and the corresponding fracture propagation behaviour was observed using an advanced acoustic emission (AE) system. The corresponding micro-structure alteration in granite was observed using SEM analysis. According to the findings, increasing temperature leads to an initial increment in reservoir rock strength and shear parameters followed by reduction, and the trend is aligned with the crack formation pattern of the rock mass. This was further confirmed by the SEM analysis, according to which the rock micro-structure is subject to only minor changes at relatively low temperatures and higher temperatures cause micro-cracks to develop along the rock mass grain boundaries. Furthermore, the conventional Mohr-Coulomb criteria failed to model the stress-strain response of rock under geothermal reservoir conditions, and was therefore modified for the corresponding in-situ conditions. (C) 2016 Elsevier Ltd. All rights reserved.