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Miscellaneous
 Winch
The winch is located at the aft end of the pipe racker and is controlled by either the assistant driller (AD) or the core tech (CT). An intercom link is used between the MCM and winch during logging operations. In contrast to most oilfield winches, the winch on the JOIDES Resolution is powered by electricity, not a diesel motor. This affords much smoother slow speed operation. The winch contains several cable sensing mechanisms, including two calibrated wheel depth encoders, which measure deployed cable length and cable speed. It also contains a tension gauge for surface cable tension.
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Prior to the logging of each hole, the logging tools are subjected to calibrations to ensure that reliable quantitative data are obtained from the tools. The Schlumberger engineer will place sleeves on some tools to expose the sensors to known values of radiation, electrical resistance, distance etc. Other tools are placed within a tank for the calibration process. Seen in the picture are the radiation calibration tanks with tools inserted. The tools are routinely subjected to calibrations during the course of a leg. A master calibration is performed at the beginning of the leg and subsequent standard calibrations are performed before each logging run.
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Schlumberger engineer performing calibration tests.
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Density calibration tank.
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Lockable Flapper Valve and Go-Devil
The lockable flapper valve (LFV) is a component of the APC/XCB Bottom Hole Assembly (BHA). It is hinged and sprung on one side and is designed to prevent fluids from backflowing up the drill pipe.
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Close-up view of the lockable flapper valve in the open position.
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Lockable flapper valve in the closed position.
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The LFV presents an obstacle for the logging operation, as a closed LFV could snag a tool string as it is withdrawn from the open hole into pipe. The LFV is engineered to pass tools through a diameter of 3-5/8" (3.625"), but to lock open or release with the passage of a 3-3/4" (3.75") tool. For this reason a go-devil (an attachment at the end of the tool string) is deployed to open the valve as the tool passes through downward. As the tool is withdrawn to the surface, the go-devil again closes the LFV. Certain tools (the GHMT, for example) can work as a go-devil because their diameter is very close to 3 3/4". Remember, when the RCB BHA is used, the LFV is not an issue. In RCB logging operations the bit is released either in the hole or on the seafloor, or is removed at the surface so logging tools pass through pipe with no other obstructions.
 There are two methods for running the go-devil:
- The go-devil is attached to the bottom of each toolstring (except the GHMT, which acts as its own go-devil), and the LFV is opened and closed for each logging run. The disadvantage of this is that it sometimes takes a few attempts to get the go-devil through the LFV.
- The go-devil is pumped down on its own before logging, and the LFV stays open for all logging runs until closed by the GHMT passing upwards though it (the WST would either have to be run before the GHMT, or after, with another go-devil attached to it). The disadvantage here is that the hole cannot be deepened, because the go-devil is sitting at the bottom of it.
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Capillary Suction Tester
 The Capillary Suction Testing (CST) equipment is used to measure the propensity of a clay to swell once it is introduced to fresh water. A slurry consisting of a portion of the core catcher with distilled water is prepared. This slurry is placed in the small stainless steel beaker seen in the picture at right. A piece of blotting paper is located underneath the beaker and below the clear plastic frame, which includes two electrodes. The slurry makes contact with the blotting paper and a "liquid front" moves outward from the beaker. The liquid front passes the first electrode and starts a timer (the black box seen in the picture). The liquid front passes the second electrode and stops the timer. The recorded time is directly related to the sample's swelling potential -- the greater the time, the higher the swelling potential is. This time can be reduced by adding KCl to the slurry. In samples where the clays are predicted to swell, KCl may be added to the drilling fluid in a percentage determined by the CST to inhibit swelling. The Operations Superintendent may ask the logger to conduct a CST on several samples to determine the likelihood of encountering a swelling clay during logging.
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