Pipe Conveyed Logging (PCL) – Preparation and General Guidelines

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Pipe conveyed logging (PCL) logging is performed when conventional wireline operations are not feasible, such as in high angle/horizontal wells.

 If there is doubt as to whether wireline logging will be successful, consideration should be given to mobilising PCL equipment on standby, although the standby cost should be balanced against the likelihood of its required use. Above 70o inclination (PCL) logging shall be used.

Job Preparation

A successful operation requires obtaining vital well site information before the job.

Basic information that needs to be acquired includes:

 

casing depth size and weight

liner top (if applicable)

hole size and TD

directional data

mud weight and temperature, mud type, mud additives (nut plug etc.)

drillpipe size, grade, tool connections, ID’s

include drillpipe connections ie., 4.1/2in x H 4.1/2 IF, as well as drillpipe size, 4.1/2in, 5in, etc. so that the internal diameter of the drillpipe is known

use of a top drive on the rig, iron roughnecks or other effect mechanical apparatus that effect the PCL operation should be checked.

Bit Size and Drillpipe

Another major area to be concerned with is small bit size (6in) and small drillpipe, commonly 3.1/2in IF Cable Side Entry Sub.

 

If 3.1/2in IF drillpipe is run all the way to the surface and a split drillstring is not used, it will require using a small 3.1/2in IF Cable Side Entry Sub

It will not be possible to run jars or heavy weight drillpipes since there are restrictions of 2.1/4in for an extended length.

This will require the rig to have enough regular drillpipe (grade E or 3 ½” tubing - Xover to be available) on location to replace the heavyweights, drill collars, jars, etc. and only normal drillpipe should be run below the Cable Side Entry Sub .

Heavyweight can be shifted in the derrick in order to be run on top of Cable Side Entry Sub

Cable Side Entry Sub shall not be run in open hole.

If a rig is using a tapered drillstring, (ie., 3.1/2in bottom, 4.1/2in on top) the internal diameter of the crossover subs should be checked to make sure they are at least 2.40in ID. It is possible to get through an ID of 2.1/4in but only if it is a short section like a crossover. Any 2.1/4in ID’s need to be physically checked for clearance using a pump-down wet cement head (PWCH) (female connector) or rabbit of the same length.

Tool Checks and Calibrations

The Logging Contractor Engineer shall perform all tool and auxiliary equipment checks and calibration.

 

The Drilling Supervisor or Operations Engineer shall check tool dimensions and position of each logging tool. It is a requirement to run the AMS and the Drilling Supervisor should check that it has been modified to give a readout range from (-3000 lbs) compression to (+3000 lbs) tension.

Rig Up Considerations

The rig up procedures require a large degree of planning and co-ordination between the Logging Contractor and Drilling Contractor. Overall responsibility for safety rests with the Drilling Supervisor. The Drilling Supervisor shall make a forward plan and conduct an operations and safety meeting prior to rigup.

Initial Trip Downhole

After rig-up the tool string is ready to be run in the hole. The running in speed should not exceed that used when running a packer on drillpipe (one stand per 2 mins) or as recommended by the logging contractor.

Additional considerations are:

  • the flexibility of the drillpipe.
  • whether the travelling block is on rails or not.
  • the kick-off point, (below this depth the tools will tend to lie on the low side of the hole and not be subject to so much bouncing as higher up)
  • obstructions downhole, eg., liner tops, (these should be passed with caution)

Continue to RIH to the casing shoe (or top logging interval, if higher). Install the cable side entry sub.

The Drilling Contractor should also have checked there is sufficient stands of drillpipe in the derrick to get to the bottom of the logging interval to avoid stationary connection time in open hole.

Connecting Cable Side Entry Sub to the Drillpipe

The Logging Engineer shall advise the Driller on the correct procedures for this operation.

Running/Pump Down of PWCH and Cable

The Logging Engineer shall supervise running the pump-down wet connector head (PWCH) and cable in the hole. The drillpipe assembly shall clearly record all restrictions, which should be passed with caution.

If it is required to pump down the PWCH, the Logging Engineer shall advise the required pump rates

Preparing for Latching

The Logging Engineer shall supervise the operation and advise on the required pump rates. The outline procedure is to run the PWCH to within +/- 1 m of the male connector. At this point the (pumps are shut down if in use and) cable up weight is checked which also relieves torque build-up, together with distance to the (DWCM) male connector.

After this, the pumps are used to establish additional cable tension (prior to running the PWCH downhole at the required latch speed). Increased cable speed requires additional pump rate to maintain pressure (all to be advised by the Logging Engineer).

After latching, there will be a pressure increase of typically 200 - 300 psi. Pumping should continue until advised by the Wireline Engineer to stop. This is to insure a good mechanical latch.

Tool Latch Verification

The Logging Engineer shall check insulation of cable phases and confirm that there is a good electrical and mechanical latch prior to continuing with the programme.

Running In / Log- In

A slug of heavy mud is pumped either prior to running in or on bottom prior to logging out, to ensure the drillstring is pulled dry.

Continuous voice communication shall be maintained between the Driller and the logging unit, as this will minimise the reaction time required to stop the drillpipe, eg., if the tool string hits an obstruction. One logging contractor personnel with portable radio to stay on rig floor during the entire operation.

A down log should be taken while running in. The Logging Contractor procedures recommend that the tools do not tag the bottom of the hole but stay a minimum 20 ft above drillers depth. Depth control will be checked with the drillpipe which should be checked on in-run and out-run.

Log Out

Continuous communication is required between Driller and the logging unit to ensuring the pulling speed and cable spooling speed are matched, and to minimise reaction time if the tool begins to stick.

After Logging and Rig Down

Once the Cable Side Entry Sub  is within one stand of the drill floor the preparations to unlatch the female connector commence. The exact procedures will be advised by the Logging Engineer and include unlatching the PWCH up to rig down of the Cable Side Entry Sub .

Once the logging tool string is at surface the Logging Engineer shall supervise the rigging down, and report any observations, eg., tool damage, to the Drilling Supervisor immediately on completion.

Logging While Drilling (LWD)

Planning

Formation evaluation whist drilling (LWD) may be included in the Drilling Programme by the Operations Engineer for the following reasons:

  • when accurate selection of casing points is required
  • to assist in picking core points when justified in terms of time savings for circulating samples
  • to guarantee obtaining some log information if hole conditions are very unstable
  • to save time and cost against running wireline logs
  • to assist in the early identification of hydrocarbons
  • to assist in the detection of the on-set of overpressures.

A detailed technical and financial justification is required for using LWD.

Procedures and Reporting

When LWD is specified, full procedural requirements for the preparation and running of tools will be provided by the LWD Contractor. Reporting requirements will be detailed in the Drilling Programme by the Operations Engineer and Petrophysicts.Particular attention must be paid to the procedures for running and removal of nuclear sources.

 

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