Frictional melting of sedimentary rock during high-speed diamond drilling : An analytical SEM and TEM investigation
Frictional melting of sedimentary rock during high-speed diamond drilling : An analytical SEM and TEM investigation
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高速金刚石钻探过程中沉积岩的摩擦熔化：分析 SEM 和 TEM 研究
DOI：
10.1016/0040-1951(92)90315-w
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发表时间：
1992
期刊：
影响因子：
2.9
通讯作者：
J. Spray
中科院分区：
文献类型：
--
作者：
L. Kennedy;J. Spray
使用井下电机驱动的天然金刚石刮刀钻头以 900 rpm 的速度进行高速钻井，导致加拿大近海预探井中的沉积岩发生了极端的蚀变。正如从地表钻井液中回收的岩屑所揭示的，这些效应包括变色（变暗）、碎裂、滑化和部分融合。钙质粉砂岩最容易发生蚀变，尤其是熔化，而砂岩和石灰岩岩屑主要表现出破裂和表面玻璃化。分析扫描电子显微镜显示，钙质粉砂岩已通过脱碳和 CaO 流失到钻井液中而发生脱钙作用。脱二氧化碳与脱水相结合，导致某些钻屑出现水泡和爆炸性破碎。分析透射电子显微镜显示钙质粉砂岩岩屑中存在玻璃。沉积岩表现出的大部分变化可归因于钻头-岩石界面处的高应变率变形和摩擦加热的影响。热计算支持熔化的发生，该计算表明，对于 0.5 的摩擦系数，金刚石-岩石接触处的温度约为 1200°C。如此高的温度会加速金刚石及其基底的磨损，从而缩短钻头寿命，并消除岩屑中潜在的重要地质信息。
High-speed drilling at 900 rpm with a downhole motor-driven natural diamond drag bit has resulted in the extreme alteration of sedimentary rock in an offshore Canadian wildcat well. These effects, as revealed in the rock cuttings retrieved from the drilling fluid at surface, include discolouration (darkening), cataclasis, slickensiding and partial fusion. Calcareous siltstones are the most susceptible to alteration, especially melting, whereas sandstone and limestone cuttings mainly exhibit fracturing and surface glazing. Analytical scanning electron microscopy reveals that the calcareous siltstones have undergone decalcification via decarbonation and the loss of CaO to the drilling fluid. Decarbonation, combined with dehydration, resulted in the vesiculation and explosive fragmentation of certain cuttings. Analytical transmission electron microscopy shows that glass is present in the calcareous siltstone cuttings. Most of the modifications exhibited by the sedimentary rocks can be attributed to the effects of high strain-rate deformation and frictional heating at the bit-rock interface. That melting took place is supported by thermal calculations which indicate that, for a coefficient of friction of 0.5, temperatures of approximately 1200°C were realized at diamond-rock contacts. Such high temperatures can accelerate the wear of diamond and its substrate and hence shorten bit life, as well as obliterate potentially important geological information in the rock cuttings.