Abstract
The science program of the Iceland Deep Drilling Project (IDDP) requires as much core as possible in the transition zone to supercritical and inside the supercritical zone (>374°C), in the depth interval 2400–4500 m. The spot coring system selected has a 7 1/4" (184.15 mm) OD at 10 m length and collects a 4" (101.6 mm) diameter core using an 8 1/2" (215.9 mm) OD core bit. It incorporates design characteristics, materials, clearances and bearings compatible with operation of the core barrel at temperatures as high as 600°C. Special attention was given to the volume of flushing which could be applied to the core barrel and through the bit while running in and out of the borehole and while coring. In November 2008 a successful spot coring test using the new core barrel was performed at 2800 m depth in the production well RN-17 B at Reykjanes, Iceland, where the formation temperature is 322°C. A 9.3-m hydrothermally altered hyaloclastite breccia was cored with 100% core recovery, in spite of it being highly fractured. A core tube data logger was also designed and placed inside the inner barrel to monitor the effectiveness of cooling. The temperature could be maintained at 100°C while coring, but it reached 170°C for a very short period while tripping in. The effective cooling is attributed to the high flush design and a top drive being employed, which allows circulation while tripping in or out, except for the very short time when a new drill pipe connection is being made. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.10.05.2010" target="_blank">10.2204/iodp.sd.10.05.2010</a>
Highlights
In late 2003, a member of the Iceland Deep Drilling Project (IDDP) consortium had offered one of its planned exploratory wells—RN-17, located on the Reykjanes peninsula—for deepening by the IDDP (Elders and Friðleifsson, 2005)
The core barrel should allow for a minimum of 30–40 L s -1 flush while running string and should be able to accept 30 L s -1 while coring
Special attention was given to the volume of flushing which could be applied to the core barrel and through the bit while running in and out and while coring
Summary
In late 2003, a member of the IDDP consortium had offered one of its planned exploratory wells—RN-17, located on the Reykjanes peninsula—for deepening by the IDDP (Elders and Friðleifsson, 2005). Further cost analyses indicated that it would be cost efficient to purchase a core barrel for the project and that the design could incorporate specific requirements for operation in deep, hot boreholes. A conventional core barrel is required for spot coring work in a deep scientific geothermal borehole.
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