3. CORK: A HYDROLOGIC SEAL AND DOWNHOLE OBSERVATORY FOR DEEP-OCEAN BOREHOLES1
3. CORK: A HYDROLOGIC SEAL AND DOWNHOLE OBSERVATORY FOR DEEP-OCEAN BOREHOLES1
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3. 科克：深海钻孔的水文密封和井下观测站1
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
R. Macdonald
中科院分区：
文献类型：
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作者：
E. Davis;K. Becker;T. Pettigrew;B. Carson;R. Macdonald
已经开发并成功部署了一种新工具，该工具提供了一种手段，可以对海洋钻探方案钻出的套管再入孔进行水文密封和仪器测量。这种密封防止水流入或流出井眼，否则会对所钻地层造成严重的热和化学干扰。该密封件能够承受在热液或构造活动环境中可能存在的正负压差，并且可以在以后的钻井作业中拆卸。该仪器是为海洋钻探计划第139阶段的初始部署而开发的，旨在监测钻井干扰恢复期间和恢复后长达2年的地层温度和压力。记录仪测量密封件下方钻孔中的绝对压力。一根包含10个热敏电阻和一根流体采样管的传感器串悬挂在记录盒下方的孔中。采样管通过密封件延伸到一个端口，允许测量压差，并从孔内深处抽出流体。数据恢复和流体采样可以通过潜水器或遥控潜水器完成。在胡安德富卡山脊北部充满沉积物的中谷裂谷部署了两支部队。第一个安装在857D井，钻探到海底以下936米的总深度，穿过470米的浊流沉积物，进入一个高渗透性的沉积物-基岩复合体，该复合体被推测为一个封闭沉积物的热液“储集层”。第二个被部署在858G孔，该孔被钻探到海底以下433米的总深度，进入埋藏在热液喷口下的火山建筑中。在部署后大约三周，两个洞的数据都成功恢复。858G井记录的温度和压力表明，地层条件受到钻井和向下流动的流体通过附近一个没有用水泥充分密封的未打入的探井进入地层的严重影响。858G井的密封压差最初为-0.24兆帕，在数据恢复时变得越来越负。857D孔记录的温度和压力似乎正在从钻井干扰中缓慢恢复。最初，该井眼密封的压差为-1.10兆帕；在数据恢复时，压差已降至-0.55兆帕。这些仪器将继续每小时监测一次地层压力和温度，为期两年。
A new tool has been developed and successfully deployed that provides a means by which cased reentry holes drilled by the Ocean Drilling Program can be hydrologically sealed and instrumented. The seal prevents flow of water into or out of a hole that would otherwise cause severe thermal and chemical disturbance to the formation drilled. The seal is capable of withstanding both positive and negative differential pressures that may be present in hydrothermally or tectonically active environments, and can be removed for later drilling operations. The instrumentation, developed for initial deployments during Ocean Drilling Program Leg 139, was designed to monitor the formation temperatures and pressures for up to 2 years during and following the recovery from drilling disturbances. A recording gauge measures absolute pressure in the borehole below the seal. A sensor string containing 10 thermistors and a fluid-sampling tube hang in the hole below the recording package. The sampling tube extends through the seal to a port, allowing the differential pressure to be measured and fluids to be tapped from deep within the hole. Data recovery and fluid sampling can be done via submersible or remotely operated vehicle. Two units were deployed in the sediment-filled Middle Valley rift of the northern Juan de Fuca Ridge. The first was installed in Hole 857D, which was drilled to a total depth of 936 meters below seafloor, through 470 m of turbidite sediment and into a highly permeable sediment-sill complex that is inferred to be a sediment-sealed hydrothermal "reservoir." The second was deployed in Hole 858G, which was drilled to a total depth of 433 meters below seafloor into a buried volcanic edifice that underlies a hydrothermal vent field. Data were recovered successfully from both holes about three weeks after deployment. Temperatures and pressures recorded in Hole 858G show that formation conditions are severely affected by drilling and by downward fluid flow into the formation through a nearby uncased exploratory hole that was not adequately sealed with cement. The differential pressure across the seal in Hole 858G was initially -0.24 MPa, and at the time of the data recovery was becoming increasingly negative. Temperatures and pressures recorded in Hole 857D appear to be recovering slowly from drilling disturbances. Initially, the differential pressure across the seal in this hole was -1.10 MPa; at the time of the data recovery, the differential had reduced to -0.55 MPa. The instruments will continue to monitor formation pressures and temperatures once per hour for 2 years.