Stripping Over Electric Logging Cable

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The following equipment should be available for stripping over a logging cable:

  • Loggers fishing kit (to be supplied by Logging Contractor).
  • Additional tension meter with cable tension readout for the Driller.
  • 90 m of ¼" rope to control the run of cable going over the top sheave.
  • 30 m of ½" rope to hold the lower sheave straight.
  • Intercom between Driller and Logging Contractor winch operator. 

1. Preparation

1. To prepare the overshot; Inspect, lubricate and dress the overshot contained on the loggers fishing kit. (The single wicker grapple specified for epoxy or rubber covered heads has one cutting edge, and the grapple for steel heads or bodies has several smaller cutting edges). Check the top end to ensure that the 2 3/16" bushing is in place. This holds the 2 1/4" hexagonal adapter of the lower rope socket, if the cable is dropped at the surface.

2. To prepare the cable for cutting;  Set the cable tension at 1-2 MT above normal hanging weight. Secure the cable clamp (T-bar) to the cable, just above the rotary table; (check that the correct sized bushing is used). Lower the cable until the cable clamp is supported by the rotary table. (Continue slacking off the cable, then cut it at a point 1 1/2 - 2 m from the cable clamp, and secure the ends.

3. To re-rig the derrick; Position the lower sheave to that it does not interfere with drill floor operations, and hang the upper sheave from one of the main derrick (water-table) beams, well above the drill  pipe stand, in such a position that it does not interfere with the travelling block.

4. To prepare the cut and thread assembly;  Fit rope sockets to both ends of the logging cable. It is preferred and safer to fit standard rope sockets, (slip type rope sockets, although they are quickly   fitted have been known to fail). Make up the remainder of the assembly, i.e. spearhead, spearhead overshot, swivel, and sub. Sinker bars may be added to the catcher assembly to provide the necessary weight.

Having rigged the derrick, assembled the rope socket and spearhead overshot to the winch end of the cable, and assembled the rope socket and spearhead to the well end of the cable, carry out a full  test. Latch the spearhead overshot to the spearhead while the cable clamp remains on the cable. Mark the cable adjacent to each rope socket with tape and test the cable with 2.5 MT tension for 1 minute. The well-end of the cable should be passed through the (fishing) overshot before the hex-  adapter is replaced.

5.To thread the cable through the drill pipe; In addition to the regular drilling crew, there should be:

  • An experienced winch operator.
  • One man at the rotary to engage and release the spear overshot.
  • A logging engineer on the drill floor to observe the operation.

2. Going In The Hole

The following is a step by step procedure of running in while stripping over the logging cable.

1. Pick up the first stand of drill pipe and install x-over subs as required.

2. Draw the spearhead overshot up to the derrick man, who can then thread it through the first stand of drill pipe. If the sinker bars make the assembly too stiff to pass the travelling block, the assembly should be fed into each stand before it is picked up.

3. Attach the spearhead overshot to the spearhead and make-up the fishing overshot with chain tongs onto the bottom of the first stand.

4. With tension in the cable, check the operation of the remote tension indicator, then remover the cable clamp.

5. Complete the make-up of the fishing assembly with the rig tongs.

6. Run the first stand into the hole:

  • maintain a depth tally,
  • maintain the cable tension to 1.0 MT,
  • pay close attention to the tension indicator.

7. Install the "C" plate, and slack-off the cable until it is supported by the "C" plate.

  • the winch operator should flag his cable to ensure that he can easily return to this exact spot for each stand of drill pipe.

8. Release the spearhead overshot, thread it through the next stand, and re-connect it to the spearhead.

9. Pull tension in the cable and remove the "C" plate. Make up the second stand onto the first and repeat the whole process for each stand. Run in slowly and carefully (according to the points listed in Item 6), thus avoiding the following primary hazards:

  • the cable being dropped,
  • broken armour wire balling up ahead of the overshot,
  • the impact of the overshot on a bridge cutting the cable,
  • the cable (if it is not removed from a keyseat) double-backing around the overshot.

Note:  Do not rotate the pipe in the hole.

10.When approaching the depth of the fish, it is good practice to clean out the fishing tool by circulating. Circulation at a bridge, at the fish, or during engagement of the fish is accomplished by hanging the cable spearhead on a bushing in a special circulating sub.

  • a) With the spearhead hanging on the "C" plate, thread the circulating sub and adapter sub over  the spearhead overshot. Latch the spearhead overshot onto the spearhead, lift the cable and remove the "C" plate.
  • b) Make-up the subs onto the drill-pipe. Place the special bushing over the cable and into the circulating sub. Lower the cable until the rope socket rests on the bushing. Unlatch the spearhead overshot.
  • c) Make up the kelly onto the circulating sub, using the appropriate cross-overs.

11.When the overshot is a short distance from the fish, the fish may come free. If this occurs  circulation may be used to clean the overshot and then the logging tool can be pulled into the grapple. The fish may, however, be covered by formation solids, requiring the overshot to be circulated down onto the fishing neck. In this case the overshot must reach the fish with sufficient       tension still in the logging cable to prevent it going slack and looping over the rope socket.

The original tension at surface, including the weight of the logging tool, is known. Also, the elongation (stretch) per 3000 m of standard logging cable sizes with respect to tool weight, can be determined from charts supplied by the Logging Contractor. Thus the fish can be engaged as follows:

  • a) Pull on the logging cable with the original logging tension and check the elevation of the spear point.
  • b) From the Logging Contractor's chart, find the cable stretch due to the weight of the logging tool in mud.
  • c) The elevation minus the stretch gives the elevation of the spear point for neutral tension in the cable at the logging tool. Space out the string with pup joints so that the spear point will not be below this elevation when the overshot engages the fish.

Note:   This procedure cannot be used on floating rigs because of the heave and tide  movements of the rig in relation to the logging tool. In this case, lower the string without circulating over the fish while maintaining a close-to-maximum pull on the logging cable.

If circulating over the fish, continue pumping while lowering the pipe and engaging the fish. An increase in both pump pressure and cable tension should be noted as the tool head enters the overshot. Stop circulating.

12.After proving, by motion of the pipe and its effect on the cable tension, that the fish is engaged, the  cable weak-point may be broken by:

  • installing the cable clamp,
  • latching the elevators around the cable, (under the cable clamp) and,
  • pulling slowly until the weakpoint breaks.

13.Cut the cable to remove the rope sockets, then tie the two ends together with a reef knot. Tape the loose ends onto the logging cable to prevent them hanging up as they pass over the sheaves.

14.Spool the cable onto the winch, then pull the fish out of the hole. Do not rotate because the fish may disengage from the overshot.

3. Problems While Stripping Over The Cable

1. If the spearhead rope socket fails, then a broken cable is left in the hole.

2. If the spearhead with rope socket and cable is accidentally dropped into the pipe, run the thread through overshot with the largest applicable guide down the pipe and attempt to engage the spear. If this fails, the drill pipe can be pulled because the bushing in the fishing overshot will catch the hexagon adapter on the spearhead.

3. When cable tension increases sharply, the cable may be stuck in a keyseat and doubled back outside the overshot. Picking up the pipe should cause a small decrease in tension. Increase the cable tension and the guide should free the cable ahead of the advancing overshot.

4. When cable tension increases moderately fast, a broken armour cable may be balling up at the overshot.

5. If the cable tension increase is gradual, as is normal for a deviated well, the elevation of the spear point will be lower. If the spear point becomes lower than the top of the pipe during running in, a  short length of spacer bar may be introduced between the rope socket and spear head.

6. If a bridge is encountered, it should be removed by circulating.

7. During stripping over operations on floating rigs, the sheave arrangement is not compensated for heave and tide movements. Hence the winch operator has to take extra care to avoid breaking the  weak point prematurely.

4. Logging Tool Stuck In A Cased Hole

In deviated wells (greater than 25 deg) it is almost invariably safer to strip over the cable in order to recover both tool and cable.

In vertical wells it is also preferable to strip over, although in certain circumstances (after consultation with Base) the following fishing procedure may be applied;

1. Secure the cable clamp to the cable just above the rotary table.

2. Re-arrange the sheaves as per item (b) 3.

3. Latch the elevators around the cable, (under the cable clamp), and pull slowly until the weak point breaks.

4. With the logging cable in tension, remove the cable clamp and spool the cable onto the logging unit winch.

5. Rig down wireline and fish for the stuck tool using conventional methods. On retrieval, ensure that the complete tool has been recovered.

5. Fishing Through Tubing

When a tool becomes stuck either in or below tubing, in most cases the only remedy is to pull the tubing to recover the fish.

Reverse circulating to recover the fish may be feasible. Fishing with slick line (piano-wire) could be considered, although this technique can only be successful if the tool is free, (e.g. if it has dropped off the end of the logging cable). Although jarring is possible, fishing for stuck tools using slick-line will almost invariably aggravate the problem.

 

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