砂岩渗透参数随渗透水压力变化的CT试验
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摘要
运用岩石高压三轴加载装置和渗透压加载装置,对砂岩进行固定应力变渗透水压力试验,同时借助SOMATOMPLUS螺旋CT扫描机进行实时观测。通过试验结果分析,推出了基于CT数的岩石空隙率计算公式,从CT尺度上分析了岩石空隙率、渗透速度、渗流速度、微孔隙直径、渗透率等随渗透水压力的变化规律,结果表明:岩石的渗透参数(空隙率、微管径、渗透率)随渗透水压力的增加而增大,渗透参数随渗透水压力的变化呈对数关系,这是由于渗透水压力使岩石内部空隙发生变形,从宏观应力-应变关系看,岩石并未出现宏观破坏,还处于弹性变形阶段;而渗流速度与渗透水压力呈线性关系,符合宏观尺度渗流的达西定律。
The seepage experiment of a sandstone sample under constant compressive stress was conducted in the laboratory using triaxial loading apparatus, seepage pressure loading apparatus and medical SOMTOM-plus CT scanner. Having analyzed the results of this experiment, the porosity formula of rock based on CT number was proposed in CT scale, and the variations of the porosity, the real flow rate in porous rock, the specific discharge, permeability and the micro-pore diameters with increasing seepage pressures were studied. The results show that the seepage parameters, such as porosity, micro-pore diameters and permeability, increase with the increase of seepage pressures. Logarithm relations between the seepage parameters and seepage pressures were proposed. The seepage pressures made the micro-pores of rock enlarged. It is shown by the relation between stress and strain of a rock in macro-scale that there is no macro-crack in the rock samples. Therefore, the deformation of rock induced by seepage pressures is elastic before macro-crack occurs. The relation between the specific discharge and seepage pressure is linear and consistent with the Darcy law in macro-scale.
The seepage experiment of a sandstone sample under constant compressive stress was conducted in the laboratory using triaxial loading apparatus, seepage pressure loading apparatus and medical SOMTOM-plus CT scanner. Having analyzed the results of this experiment, the porosity formula of rock based on CT number was proposed in CT scale, and the variations of the porosity, the real flow rate in porous rock, the specific discharge, permeability and the micro-pore diameters with increasing seepage pressures were studied. The results show that the seepage parameters, such as porosity, micro-pore diameters and permeability, increase with the increase of seepage pressures. Logarithm relations between the seepage parameters and seepage pressures were proposed. The seepage pressures made the micro-pores of rock enlarged. It is shown by the relation between stress and strain of a rock in macro-scale that there is no macro-crack in the rock samples. Therefore, the deformation of rock induced by seepage pressures is elastic before macro-crack occurs. The relation between the specific discharge and seepage pressure is linear and consistent with the Darcy law in macro-scale.
引文
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[17]Yale D P,Lyons S L,Qin G.Coupled geomechanics fluid flow modeling in petroleum reservoirs:coupled versus uncoupled response[A].Pacific Rocks[C].Rotterdam:Balkema,2000.137–144.
[2]Nolte D D,Pyrak-Nolte L J.Stratified continuum percolation:Scaling geometry of hierarchical cascades[J].Physical Review A,1991,44:6320–6333.
[3]Nootishad J,Ayatollahi M S,Witherspoon P A.Finite element method for coupled stress and fluid flow analysis in fractured rock masses[J].Int J Rock Mech Min Sci Geomech Abstr.1982,19:185–193.
[4]Oda M.An equivalent continuum model for coupled stress and fluid flow analysis in jointed rock masses[J].Water Resour Res,1986,22(13):1845–1856.
[5]仵彦卿.裂隙岩体应力与渗流关系研究[J].水文地质工程地质,1995,6:30–35.
[6]仵彦卿.岩体水力学导论[M].成都:西南交通大学出版社,1995,78–90.
[7]Hubbert M K,Willis D G.Mechanics of hydraulic fracturing.[J].Journal of Petroleum Technology,1957,9(6):153–168.
[8]冷雪峰,杨天鸿,国怀专,等.单孔岩石水压致裂过程的数值模拟分析[J].世界有色金属,2002,10:32–34.
[9]黄荣撙.水力压裂裂缝的起裂和扩展[J].石油勘探与开发,1981,5:62–73.
[10]陈治喜,陈勉,金衍,等.水压致裂法测定岩石的断裂韧性[J].岩石力学与工程学报,1997,16(1):59–64.
[11]刘允芳.水压致裂法地应力测量的校核和修正[J].岩石力学与工程学报,1998,17(3):297–304.
[12]李方全,刘鹏.原地应力测量对某核废料处置场场地评价的应用[J].岩石力学与工程学报,1993,12(12):55–62.
[13]Keck R G,Withers R J.Afield demonstratiou of hydraulic fracturing for solids waste injection with real-time passive seismic monitoring[A].Proceedings of1994SPE Annual Technical Conference and Exhibition[C].New Orleans,1994.
[14]李应平.微震分析水压致裂的破裂过程[J].地震学报,1996,18(3):292–300.
[15]吴景浓.室内岩石水压致裂三轴试验研究[J].岩土工程学报,1986,8:61–69.
[16]冷雪峰,唐春安,杨天鸿,等.岩石水压致裂过程的数值模拟分析[J].东北大学学报(自然科学版),2002,23(11):1104–1107.
[17]Yale D P,Lyons S L,Qin G.Coupled geomechanics fluid flow modeling in petroleum reservoirs:coupled versus uncoupled response[A].Pacific Rocks[C].Rotterdam:Balkema,2000.137–144.
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