青海共和盆地存在干热岩可能性探讨
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摘要
青海共和盆地地处"秦昆岔口"的新生代断陷盆地,盆缘构造岩浆岩带发育,活动断裂、温泉密集,超过60℃的温泉6处,最高可达93.5℃;盆地内温泉成群分布,地热钻井揭露温度高,1203m钻孔(R1)实测孔底温度可达83℃,969m钻孔(QR1)实测孔底温度为70℃,地温梯度高达6～7℃/100m,是正常地温梯度的2倍,地热增温随深度增大而升高,推测3000m温度可达200℃,并在(QR1)孔底见36m花岗岩;地震反射波和可控源音频大地电磁测深推断基底斜坡界面对应重力低异常,可认为重力低异常为花岗岩引起,作为盆地热源可能存在干热岩。
The Qinghai Gonghe Basin is located in the"Qin Kun Fork"Cenozoic fault basin.Oil-drilling data show that the Cenozoic overburden thickness is greater than 5000 m.The basin margin structure-magma belt is well developed;active faults and hot springs are intensive.There are 6 hot springs with temperature ranging from 60℃ to 93.5℃.The hot springs occur in groups in the inner basin.Geothermal drilling data reveal that the temperature in depth is quite high.In the 1203 m borehole(R1),the measured bottom hole temperature is as high as 83℃,and in the 969 m borehole(QR1),the temperature can reach 70℃.The geothermal gradient is as high as 6 ～ 7℃ /100 m and is twice the normal value.Geothermal temperature increases with the decreasing depth.The temperature at a depth of 3000 m is expected to reach 200℃.At the borehole(QR1) granite of 36 m thick can be found.Seismis reflection indicates that the slope of the basement corresponds to gravity low anomaly.Gravity low anomaly is thought to be caused by granite and the basin heat source may indicate the existence of hot dry rock.
The Qinghai Gonghe Basin is located in the"Qin Kun Fork"Cenozoic fault basin.Oil-drilling data show that the Cenozoic overburden thickness is greater than 5000 m.The basin margin structure-magma belt is well developed;active faults and hot springs are intensive.There are 6 hot springs with temperature ranging from 60℃ to 93.5℃.The hot springs occur in groups in the inner basin.Geothermal drilling data reveal that the temperature in depth is quite high.In the 1203 m borehole(R1),the measured bottom hole temperature is as high as 83℃,and in the 969 m borehole(QR1),the temperature can reach 70℃.The geothermal gradient is as high as 6 ～ 7℃ /100 m and is twice the normal value.Geothermal temperature increases with the decreasing depth.The temperature at a depth of 3000 m is expected to reach 200℃.At the borehole(QR1) granite of 36 m thick can be found.Seismis reflection indicates that the slope of the basement corresponds to gravity low anomaly.Gravity low anomaly is thought to be caused by granite and the basin heat source may indicate the existence of hot dry rock.
引文
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[2]石宝颐,张峻太.论秦昆构造带的共和“缺口”[J.]青海地质,1982(3):21-29.[SHI B Y,ZHANG JT.Discussion on Gonghe gap In Qing-kun tectonicbelt[J].Qinghai Geology,1982(3):21-29.(inChinese)]
[3]姜春发,王宗起,李锦轶,等.中央造山带开合构造[M.]北京:地质出版社,2000:107-110.[JIANGC F,WANG Z Q,LI J Y,et al.Opening-closingtectonics of the central organic belt[M.]Beijing:The Geological Publishing House,2000:107-110.(in Chinese)]
[4]王吉玉,张兴鲁.青海共和盆地的挽近构造运动[J].西北地质科技情报,1979(1):25-29.[WANG J Y,ZHANG X L.Tectonic neoidmovement of Qinghai-gonghe basin[J.]Northwestern Geological Science and TechnologyInformation,1979(1):25-29.(in Chinese)]
[5]袁道阳,张培震,刘小龙,等.青海鄂拉山断裂带第四纪构造活动及其所反映的青藏高原东北缘变形机制[J.]地学前缘,2004,11(4):393-402.[YUAN D Y,ZHANG P Z,LIU X L,et al.Thetectonic activity and deformation features during theLate Quaternary of Elashan Mountain active fault zonein Qinghai Province and its implication for thedeformation of the northeastern margins of the Qinghai-Tibet Plateau[J.]Earth Science Frontiers,2004,11(4):393-402.(in Chinese)]
[6]李长松.龙羊峡地区地下热水初探[J.]环境水文工程地质:地热专辑,1986(3):51-52.[LI C S.Discussion on thermal water in Longyangxia region[J.]Environmental Hydrogeology and EngineeringGeology,1986(3):51-52.(in Chinese)]
[7]王昌桂,吕友生.共和盆地一个值得研究的新盆地[J.]新疆石油地质,2004,25(5):471-473.[WANG C G,LV Y S.Gonghe basin:a new andworth-researching basin[J.]Xinjiang petroleumGeology,2004,25(5):471-473.(in Chinese)]
[8]胡宁.青海省区域岩石物性特征[J.]青海地质,1991(1):42-52.[HU N.Physical features ofregional rock in Qinghai province[J.]QinghaiGeology,1991(1):42-52.(in Chinese)]
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