高压液氮射流提高深井钻速机理
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摘要
针对深部油气及地热钻探中岩石温度及强度高、钻速普遍偏低等问题,采用花岗岩、页岩和砂岩3种岩样,开展了高温岩石液氮冷却后的力学特性测量实验与液氮射流破岩实验,解析了液氮喷射破岩的宏观特征与微观机理、液氮-岩石的传热特征、岩石内热应力的演化规律,进而提出了高压液氮射流辅助钻井的新方法。研究表明,液氮冷冲击可显著降低岩石的单轴压缩强度及弹性模量,岩石温度越高,力学弱化程度越高,冷冲击对岩石的损伤程度越强;液氮射流破岩以大块体积破碎为主要破岩特征,具有破岩效率高、破岩门限低的特点,岩石温度越高,液氮射流破岩效果越强;液氮喷射作用下花岗岩的损伤程度最高,该方法对高温花岗岩地层具有更好的适用性,应用于深层干热岩储集层钻井提速,具有良好的前景。图13表2参19
To address the high rock strength and low drilling rate issues in deep oil/gas and geothermal exploitation, we performed mechanical property tests on three kinds of rock samples(granite, shale and sandstone) subjected to liquid nitrogen(LN2) cooling and conducted rock-breaking experiments using LN2 jet. Rock-breaking characteristics and mechanisms of LN2 jet, heat transfer features between LN2 and rock and thermal stress evolution in rock were analyzed. A novel high-pressure LN2 jet assisted drilling method was proposed accordingly. The study results show that LN2 thermal shock can significantly reduce uniaxial compression strength and elastic modulus of rock. Rock damage and corresponding mechanical deterioration become more pronounced with increasing rock temperature.The LN2 jet has merits of high rock-breaking efficiency and low threshold rock-breaking pressure. Rock failure under LN2 jet impact is characterized by large volume breakage and the rock-breaking performance becomes more significant with increase of rock temperature.Under the impact of LN2 jet, the damage of granite is the most remarkable among the three rock samples. Thus, this method works better for high temperature granite formations. It has a good application prospect in speeding up drilling rate in deep hot dry rock geothermal reservoirs.
To address the high rock strength and low drilling rate issues in deep oil/gas and geothermal exploitation, we performed mechanical property tests on three kinds of rock samples(granite, shale and sandstone) subjected to liquid nitrogen(LN2) cooling and conducted rock-breaking experiments using LN2 jet. Rock-breaking characteristics and mechanisms of LN2 jet, heat transfer features between LN2 and rock and thermal stress evolution in rock were analyzed. A novel high-pressure LN2 jet assisted drilling method was proposed accordingly. The study results show that LN2 thermal shock can significantly reduce uniaxial compression strength and elastic modulus of rock. Rock damage and corresponding mechanical deterioration become more pronounced with increasing rock temperature.The LN2 jet has merits of high rock-breaking efficiency and low threshold rock-breaking pressure. Rock failure under LN2 jet impact is characterized by large volume breakage and the rock-breaking performance becomes more significant with increase of rock temperature.Under the impact of LN2 jet, the damage of granite is the most remarkable among the three rock samples. Thus, this method works better for high temperature granite formations. It has a good application prospect in speeding up drilling rate in deep hot dry rock geothermal reservoirs.
引文
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[16]WU X,HUANG Z,SONG H,et al.Variations of physical and mechanical properties of heated granite after rapid cooling with liquid nitrogen[J].Rock Mechanics and Rock Engineering,2019,52(7):2123-2139.
[17]李维特,黄保海,毕仲波.热应力理论分析及应用[M].北京:中国电力出版社,2004:59-68.LI Weite,HUANG Baohai,BI Zhongbo.Theoretical analysis and application of thermal stress[M].Beijing:China Electric Power Press,2004:59-68.
[18]KANG J Y,KIM S H,JO H J,et al.Film boiling heat transfer on a completely wettable surface with atmospheric saturated distilled water quenching[J].International Journal of Heat&Mass Transfer,2016,93:67-74.
[19]彭可文,田守嶒,李根生,等.自振空化射流空泡动力学特征及溃灭强度影响因素[J].石油勘探与开发,2018,45(2):326-332.PENG Kewen,TIAN Shouceng,LI Gensheng,et al.Bubble dynamics characteristics and influencing factors on the cavitation collapse intensity for self-resonating cavitating jets[J].Petroleum Exploration and Development,2018,45(2):326-332.
[2]陆川,王贵玲.干热岩研究现状与展望[J].科技导报,2015,33(19):13-21.LU Chuan,WANG Guiling.Current status and prospect of hot dry rock research[J].Science&Technology Review,2015,33(19):13-21.
[3]曾义金.干热岩热能开发技术进展与思考[J].石油钻探技术,2015,43(2):1-7.ZENG Yijin.Technical progress and thinking for development of Hot Dry Rock(HDR)geothermal resources[J].Petroleum Drilling Techniques,2015,43(2):1-7.
[4]MAGUIRE J J C.Cryogenic drilling method:U.S.Patent 3,612,192[P].1971-10-12.
[5]MAGUIRE J Q.Cryogenic drilling method:U.S.Patent Application12/012,872[P].2008-08-07.
[6]WILSON D R,SIEBERT R M,LIVELY P.Cryogenic coal bed gas well stimulation method:U.S.Patent 5,464,061[P].1995-11-07.
[7]STAFF J.Field applications of cryogenic nitrogen as a hydraulic fracturing fluid[J].Journal of Petroleum Technology,1998,50(3):38-39.
[8]CHA M,YIN X,KNEAFSEY T,et al.Cryogenic fracturing for reservoir stimulation:Laboratory studies[J].Journal of Petroleum Science and Engineering,2014,124:436-450.
[9]ALQATAHNI N B,CHA M,YAO B,et al.Experimental investigation of cryogenic fracturing of rock specimens under true triaxial confining stresses[R].SPE 180071-MS,2016.
[10]周静伟,杨兴贤,耿丽萍,等.非稳态冲击射流强化传热试验研究[J].机械工程学报,2010,46(6):144-148.ZHOU Jingwei,YANG Xingxian,GENG Liping,et al.Experimental investigation on heat transfer augmentation with unsteady impinging jet[J].Journal of Mechanical Engineering,2010,46(6):144-148.
[11]ZHANG S,HUANG Z,LI G,et al.Numerical analysis of transient conjugate heat transfer and thermal stress distribution in geothermal drilling with high-pressure liquid nitrogen jet[J].Applied Thermal Engineering,2018,129:1348-1357.
[12]黄中伟,魏江巍,李根生,等.液氮冻结对岩石抗拉及抗压强度影响试验研究[J].岩土力学,2016.37(3):694-700.HUANG Zhongwei,WEI Jiangwei,LI Gensheng,et al.An experimental study of tensile and compressive strength of rocks under cryogenic nitrogen freezing[J].Rock and Soil Mechanics,2016,37(3):694-700.
[13]WU X,HUANG Z,ZHANG S,et al.Damage analysis of high-temperature rocks subjected to LN2 thermal shock[J].Rock Mechanics and Rock Engineering,2019(1):1-19.
[14]FERRERO A M,MARINI P.Experimental studies on the mechanical behavior of two thermal cracked marbles[J].Rock Mechanics and Rock Engineering,2001,34(1):57-66.
[15]WU X,HUANG Z,LI G,et al.Experiment on coal breaking with cryogenic nitrogen jet[J].Journal of Petroleum Science and Engineering,2018,169:405-415.
[16]WU X,HUANG Z,SONG H,et al.Variations of physical and mechanical properties of heated granite after rapid cooling with liquid nitrogen[J].Rock Mechanics and Rock Engineering,2019,52(7):2123-2139.
[17]李维特,黄保海,毕仲波.热应力理论分析及应用[M].北京:中国电力出版社,2004:59-68.LI Weite,HUANG Baohai,BI Zhongbo.Theoretical analysis and application of thermal stress[M].Beijing:China Electric Power Press,2004:59-68.
[18]KANG J Y,KIM S H,JO H J,et al.Film boiling heat transfer on a completely wettable surface with atmospheric saturated distilled water quenching[J].International Journal of Heat&Mass Transfer,2016,93:67-74.
[19]彭可文,田守嶒,李根生,等.自振空化射流空泡动力学特征及溃灭强度影响因素[J].石油勘探与开发,2018,45(2):326-332.PENG Kewen,TIAN Shouceng,LI Gensheng,et al.Bubble dynamics characteristics and influencing factors on the cavitation collapse intensity for self-resonating cavitating jets[J].Petroleum Exploration and Development,2018,45(2):326-332.