Removal of Unconsolidated Sediment Core from the Inner Barrel

Removal of the core of unconsolidated sediments from a standard wire-line core barrel differs from the procedure used for removing a rock core. The removal procedure is as follows:

  1. The solid inner barrel is removed from the outer core barrel and is placed in a chain-type pipe vise. The core-retainer shoe is then unthreaded from the lower end of the inner barrel and the swivel-head assembly is unthreaded and removed from the upper end.
  2. The clayey filter cake on the outside of the core will usually stick to the barrel and the core will have to be pushed out. To do this, a plunger affixed with a 5-ft extension is fitted into the upper end of the inner barrel and used to push on the top of the core. It is occasionally difficult to break the surface tension between the core and the solid inner barrel; however, when the core begins to move as pressure is exerted upon it, it usually will slide out easily.
  3. When the core begins to move, a half-round trough (5-ft-long, thin-walled tubing, cut in half) is placed under the leading edge of the solid inner barrel, and the full length of the core is extruded into the trough. The trough is then placed on sawhorses or a clean platform for inspection. The cored material can now be exposed for examination and logging by trimming a thin section of filter cake off with a sharp knife.
  4. After the core has been logged, a 6-ft length of thin-wall, lay-flat, clear plastic tubing is placed over the core and the trough. Plastic tubing of this type can be purchased in various diameters and different-length rolls. One end of the tubing is then tied. A felt marking pen is used to mark the core as to top, bottom, depth, hole number, and any other necessary data. After the insleeved core is marked, another half-round trough is placed over it. The core is then turned over and the trough that is still in the plastic sleeve is removed and the other end of the plastic sleeve is tied. The core trough, now holding the plastic-insleeved core, is placed against or into the end of a precut, 5-ft length of plastic pipe, and the core pushed into this pipe for further protection. Note: If the pipe used is too large to fit the core, some additional packing (plastic or paper) should be wrapped around the core to ensure a snug fit.
  5. The plastic pipe is then capped and taped. The same identification that was written on the plastic core sleeve is repeated on the plastic pipe. The pipe with core enclosed should be placed in a core box for additional protection.

Removal of the core from the HQ-3 wire-line inner barrel and split-tube liner used by the Water Resources Division differs somewhat from the standard barrel described above:

  1. The wire-line inner barrel is removed from the hole and placed in a strap vise, and the core-retainer shoe and swivel-head assembly are removed. An adaptor head with an internal piston that butts against a thin-wall, split tube is screwed onto the upper end of the inner barrel (fig. 22), and a quick-coupling hose that leads to a hand pump is coupled to the adaptor head. The pump is connected to, or the intake pipe is placed in, a water supply (barrel or water tank); operation of the hand pump gently extrudes the split-tube liner.
  2. The split-tube liner is placed on a stand or platform, and one-half of the split-tube liner is removed. Sometimes the filter-cake stickiness causes a surface tension similar to that described for the solid inner barrel, and it is difficult to lift the split-tube liner off the core. The split-tube liner can be separated by gently tapping the upper part of the split tube while, at the same time, lifting one end to break it loose. If this does not loosen it, a putty knife is placed on both sides of the core between the split-tube liner while lifting one end of the split tube and gently prying down on the upper part of the core. This procedure may have to be done the entire length of the core because, if the top half of the the split-tube liner is stuck, the bottom half will be stuck also. A small-diameter stiff wire, a thin flexible saw blade, or an ordinary cheese-cutter blade can be bent or torqued to the exact contour of the inside of the split-tube liner and slid the entire length of the core, severing it from the bottom tube.
  3. After the core is severed from the bottom section of the split-tube linei; it is placed on a clean platform and care is taken not to bend or damage the tube (while using it as a core trough). Subsequently trim a thin section of filter cake from the core with a sharp knife thereby exposing a section of clean core for examination.
  4. After the core is logged, a 6-ft length of thin-wall lay-flat, clear plastic tubing is placed over the core and split-tube liner and one end of the tubing is tied. A felt marking pen can be used to

Hydraulic pump

Hydraulic pump

Longyear Drilling Pump Out Adaptor

Piston

Figure 22.—Core-liner extrusion pump-out assembly (reprinted by permission from Longyear Company).

Piston

Figure 22.—Core-liner extrusion pump-out assembly (reprinted by permission from Longyear Company).

identify the core as to top, bottom, depth, hole number, and any other pertinent data. After labeling, the other half of the split-tube liner (or use a core trough) is placed over the core. The troughs can then be rolled over and the split-tube liner half that is still in the plastic sleeve removed and the other end of the plastic sleeve tied. The split-tube liner half or core trough holding the plastic-insleeved core is placed against or into the end of a precut, 5-ft length of plastic pipe, and the core is pushed into this pipe for further protection. If necessary, additional packing material should be wrapped around the core so that it fits snugly in the protective pipe.

5. The plastic pipe is then capped and taped. Repeat the written core identification on the plastic pipe and place the pipe in a core box for additional protection.

Removal of Rock Core from the Inner Tube

After the core barrel is removed from the hole and placed in a pipe vise or on a clean platform, the diamond bit is removed using a pipe wrench or chain wrench, and extreme care is taken not to affix the wrench to the bit or reaming shell opposite any diamonds. Then the outer tube is broken loose and removed from the core-barrel head assembly exposing the inner tube. The inner tube is disconnected from the inner part of the core-barrel head assembly and the core-retainer shoe removed. Then the inner tube is slightly inclined to allow the core to slide into the segmented compartments of the core boxes. The core is marked with the depth, top and bottom of the core, and any other pertinent information.

After reassembling the core barrel and before placing the bit back on the bottom of the core hole, carefully measure the core barrel and drill pipe. The reason for doing this is that a short stub of core often projects up from the bottom of the hole because the core retainer has broken the core off 1 or 2 in. above bottom oi; occasionally, a segment of the core has fallen out of the inner tube when the core barrel was tripped to the surface. Attempts should not be made to core over or through these obstacles, or blockage of and damage to the core bit will result. If there is core debris remaining in the hole, a chopping or rotary bit must first be used to drill and break up the debris and drilling fluid circulated to clean the material out of the hole prior to resuming further coring in the hole.

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