3. Rig-Up and Survey Quality Control

The checks for rigging up for logging and running the survey are important to achieve a good quality of the surveys to be run. The wireline contractor shall have detailed procedures developed for this purpose. These shall cover activities and services like:

-   Placement and installation of wire-line unit(s).

-   Rigging up of wire-line sheaves.

-   Handling and storage of explosives and radioactive material, and precautions in this respect.

-   Surface preparations, assembly and function testing of logging tools.

-   Running in hole.

-   On bottom checks and considerations.

-   Measures to prevent getting stuck.

-   Surveying.

-   Post Survey activities.

-   Cutting Side Wall Samples.

-   Running and Setting of Packers.

-   Running directional Survey Tools.

-   Reporting.

4. Safety

Good communications are important in order to maintain safety during electric wire-line logging. The following procedures should be observed with regard to the safety of personnel and equipment:

1. The chain connecting the lower sheave shall be securely anchored and the sheave adjusted to  the centre of the well.

2. Keep well clear of the logging cable. If it is stretched tight in the hole and is over tensioned, the cable may break suddenly. If the cable is loose on the deck, it may be that the tool is hung up in the hole and too much cable has been unspooled.

-       Never step over the cable, always walk around it!

3. Check the cable armour regularly for unravelling armour strands. This applies particularly to operations through a stuffing box.

4. Avoid the drill floor area during logging operations.

5. Do not stand close to the lower sheave, in case the tie-down chain breaks or comes undone due to high tension in the cable.

6. Tag a reminder on the BOP control panel to ensure the cable is not cut by inadvertent closure during wire-line operations.

7. Do not perform overhead lifts across or near the cable during wire-line operations.

When the wire-line operations involves the use of explosives and radioactive sources, all operations shall be conducted in accordance with the safety procedures. Only authorised and qualified personnel shall be on the drill floor during these operations, and clear signs and barriers should be placed to show such operations are in progress. The requirement regarding radio silence shall be observed as appropriate.

5. Preparation for Logging

1. Carry out a test transmission to check if the equipment is operational.

2. Ensure that logs of any adjacent or nearby well are available for comparison and correlation.

3. Check the logging programme with the contractor to confirm the running order of the tools. Do not run a tool requiring a radioactive source as first in hole, until bottom hole conditions are known. Run the surveys in decreasing order of importance in case the hole condition deteriorates.

4. Provide the logging contractor with the following data:

a)      Well description, location and drill floor elevation, BOP and Wellhead depths.

b)     Bit and casing sizes, total depth and casing shoe depths, any anomalies in the string.

c)      Mud type, weight, viscosity, water loss and pH.

d)     The logging programme, including;

-           all logs which are required,

-           intervals to be logged, and where repeat sections are to be recorded,

-           which logs are to be taped, and when transmission should be carried out, as applicable.

e)      Downhole conditions relevant to the logging operations; e.g. deviation, tight spots, dog legs, pressure and gas zones, fill experienced on previous trips, etc.

f)      The duration of the last circulation of the hole and the time when circulation stopped prior to pulling out of the hole for logging.

5. Provide a mud sample 1 litre, mud filtrate 10 cc. and mud cake (at least 3/16 in (6 mm) thick to be representative). The mud sample should be taken from the flow line during circulation just prior to logging. Ensure the measurements are made on the sample as soon as possible.

6. Sidewall Samples

Sidewall samples are taken to provide either palaeotological or petrophysical information. The samples are obtained using a tool on a wireline. Because sidewall sampling involves the use of explosives, the following procedures shall be strictly adhered to:

1. All operations shall be conducted in accordance with the safety procedures given above on the use and handling of explosives. Only authorised and qualified personnel shall be on the drill floor during these operations, and clear signs and barriers should be placed to show such operations are in progress. The requirement regarding radio silence shall be observed as appropriate.

2. Check distance from the measure point of correlation tool (S.P. or Gamma Ray) to the bottom shot. Make the appropriate correction before taking the first sample and adjust as the firing proceeds.

3. Ensure the powder load for each shot has been correctly loaded.

4. Ensure that:

a)      The correct size gun is used.

b)     The correct length fasteners are used.

c)      High temperature powder is used when necessary above 140 C, bottom hole temperature.

5. Make the depth correlation log (GR) at the normal gamma ray logging speed of 500 m/hr and   determine the correct depth. Check carefully for creep i.e. the movement of sample taken after the winch has stopped. If the creep is 0.5 m or less, stop at correct firing depth to shoot sample. If creep exceeds 0.5 m, it is permissible to shoot "on the run": in this case, note on the report form that this technique has been used, and in particular report any samples suspected of being shot off   depth.

6. After successfully firing each shot, try to "work" the core free. If all attempts at freeing a core fail, the retaining wires can be broken by dropping the sample taker rapidly and snapping them off.

7. Move up and down slowly 3000 m/hr with the samples. For unconsolidated samples lower speeds should be used e.g. 1200 m/hr.

8. Watch the tension very carefully when entering and ascending through casing.

9. Untangle the retaining wires. Remove one bullet at a time from the gun, starting at the bottom of the gun (Sample no.1). Place the bullets in the correct compartment of the box, (supplied by the Logging Contractor) and continue to remove the other bullets. Once all the bullets have been removed, press each core into a sample bottle one at a time noting the recovery. Record also when bullets are lost or empty. This sample removal/identification should be supervised by the Logging     Engineer and a Company Drilling or Petroleum Engineering representative, to ensure that depth identification of the samples is correct.

10.Ensure that all relevant data i.e. Company name, well number, sample depth, sample number is given on the sample container. Mark the sample number on the container lid.

The sidewall samples shall be described on the Sidewall Sample Report.

These descriptions shall be sent immediately to Base and the samples despatched on the first available helicopter.

7. Running and Setting Packers

Because the running and setting of packers involves the use of explosives, the following procedures shall be strictly adhered to:

1. All operations shall be conducted in accordance with the safety procedures on the use and handling of explosives. Only authorised and qualified personnel shall be on the drill floor during these operations, and clear signs and barriers should be placed to show such operations are in progress. The requirements regarding radio silence shall be observed as appropriate.

2. Keep the packer under cover in a safe place until required.

3. Run the junk catcher until hole is clean. If necessary, make a check trip with a bit and scraper   followed by a further junk catcher run.

4. Inspect the packer carefully (particularly the slips and rubber) and witness the preparation of the packer prior to running in hole. Ensure the correct size packer is used.

5. Avoid running the packers into or through perforated intervals because deformed casing or burred holes may jam the packer or damage the seal rubbers. Do not exceed a running speed of 3000 m/hr. Keep the tension under constant observation, as the plug is a tight fit and may easily hang up on any obstructions.

6. Use a CCL for depth control, and never attempt to set a plug within 1 m of a collar. The normal practice is to check depths when pulling up, to avoid problems with loops or slack cable. However, in large casing sizes, the centralising action of the packer may keep the CCL away from the hole sides so the collars are difficult to locate. In this case it is often possible to see the collars when moving down - when moving upwards subsequently to setting depth, make allowance for hysteresis in the tool movement.

7. Make a CCL log across the setting depth to ensure correlation with GR/CCL survey.

8. Record at a distance of two or three casing collars below setting depth, then stop at required depth.

9. Set packer. Observe the tension change or cable vibration. Up to three distinct tension kicks may be observed when setting a packer. Allow at least one minute after firing for the packer to fully set   before carefully pulling back the setting tool. For large packers, a longer time may be required.

10.Move the CCL across the scale, record two casing collars above setting depth. Pull up slowly to ensure the tool has disengaged from the packer.

11.After setting a bridge plug, lower the setting tool on to the plug, record the pick-up point and two collars above. This procedure should not be followed with production packers (cement retainers) in case the tool latches on to the packer and cannot be freed.

Note:The pick up point may appear deeper due to reduced cable stretch as the weight of the plug will no longer be applied to the cable.

12.Ensure the plug has set correctly, but do not exceed 3000 m/hr when pulling out. If the plug has NOT set, pull out much more slowly, particularly if there are indications that only one set of slips may have operated.

13.Keep unnecessary personnel off rig floor while gas pressure is released from the setting tool.

14.Check the setting tool carefully to ensure that its operation was normal, i.e. the release stud has sheared, and there is no damage to the release sleeve. If there is any doubt that the packer has set correctly, run slim-hole CCL (1 11/16") to determine packer depth.

8. Formation Testing

Basically there are six stages to formation testing operations:

-   Surface preparation

-   Running in the hole

-   Pretests

-   Sampling

-   Transfer of samples

-   Reporting of results

and the procedures and guidelines for each are given in the article on production testing.

9. Pipe Conveyed Logging

9.1 Pipe Conveyed Logging/ Logging Through Drillpipe

-   Two systems are available for use:

1. Push Down Systems TLC/PCL. These systems use regular open hole logging tools run down hole on 3 1/2" or 5 1/2" Drillpipe (Schlumberger/Western Atlas).

2. Pump Down Systems. These systems pumps down slim hole logging tools (2 3/4" or 1 11/16") through drillpipe ( Western Altas).

The two systems are usable in any well where wireline run logging tools are unable to pass, such as bad hole section/wash out or where hole deviation is too high.

The preplanning of a TLC/PCL operation require planning of tool combination, selection of and organisation of special tools based on well data.

Drilling jar will be run if required .Special precautions shall be taken when a drilling jar is run.

Check that Logging service contractor is only using only zone 0 equipment and maintain the certification of same .

Be aware of that only GR; BHC and Induction Log are available for Pump Down Systems 2) (PDS) when using 3 1/2" DP.

A Side Entry Sub (SES) should be placed in the drillstring  but is only recommended with 9 5/8" casing or larger. The system available for 7" casing , with the 1" ID of the accompanying SES will not permit the passage of any back off tools. The Western Atlas 3 1/2" IF SES has an ID of 1.81" through which back off tools can pass .

When the Side Entry Sub on the bottom of the drillstring reaches the casing shoe it guides the multi conductor cable from the inside of the drillstring into the drillstring/ casing annulus.

Note that the  SES should not be run past  a point of  more than 30 inclination and not placed in a position where it will squash the cables against the low side of the hole.

General outline of procedures

The TLC/PCL system is a technique which can be used in highly deviated holes or holes with deteriorating conditions, where it is not possible to log on conventional wireline. The logging tools are run on drillpipe and the wireline cable is attached with a wet-connector on top of the tools. The cable is run through a Side Entry Sub (SES) to allow continuos logging and circulation.

Preparations prior to logging

-   Prior to and during the job, safety meetings should be held with each crew to highlight the operational steps

-   All drillpipe and the jar should be drifted (size to be checked with the contractor)

-   Two sets of wet connectors are to be supplied by the logging contractor.

-   Install the jar at approximately 200m above the wet connector. See that the jar stroke is completely extended ( if the jar is fired, run in hole and function test tools)

-   Make up any additional stands of drillpipe required to reach the bottom the logging interval.

-   Install intercom/ communication head sets and tension compression monitor near driller.

-   Have the logging unit positioned such that direct eye contact with drill floor is possible.

-   Cable cutter s on drill floor

Running tools into bottom of logging interval

1. Make up logging tools in rotary table .Test function of wet connector and logging tools ( check wet connection vertically in the rotary table, not horizontally on the floor). Before fully torquing up the IF connection of the latch assembly, put on the one single of drillpipe above to prevent sideways movement.

2. RIH 200m drillpipe.

3. Install jar.

4. RIH string slowly till tools are approximately 20-30m from top of  logging interval.

Note: CONTRACTOR PERSONNEL SHOULD BE ON DRILLFLOOR CONTINUOUSLY FROM THIS TIME ON.

5. Insert female part of wet connector in the Side  Entry Sub. RIH wireline cable a few hundred metres until it can run on its own weight.

6. RIH the Side Entry Sub on 1 joint of drillpipe (below BOP's) ,make up Right Hand Kelly Cock (RHKC) and circulation head (use DP-screen). the packoff seal of the side entry sub more effective when wet.

7. RIH wireline cable to approximately 50m above wet connector . Use snugger sheave (pull over sheave ) to pull cable back from drillpipe. Record cable tension.

8. Circulate for 10-15 minutes.

9. RIH wireline cable to wet connector  and latch on .(Depending on the depth, angle, etc. pump down while latching, contractor to advise )

10.If positive indication of latch :

- indication from line check (communication with tool)

- test logging tools

- make sure  pumps are off again before coming up

If not latched, pull out approximately 50m and try again . Circulate and try to find right pumping pressure and cable speed (contractor to advise).

11.POOH Side Entry Sub(SES)above table . Pull on cable to recorded cable weight . Slack off one (1) m  and put on clamp.

12.RIH tools to bottom of logging interval .Record weight of string up and down.

-       While running in , log down (contractor to advice on running speed).

-       Communication between driller and winch man is vital.

-       Watch for cable damage by slips and tongs

-       Contractor to advice on maximum compression allowed.

Logging

During calibration in open hole keep string moving to avoid  differential sticking.

Start logging up . After every stand set slips (minimise downward movement because caliper/ pad is open). Winchman to give slack after slips are set . Again: communication between winchman and driller is vital.

With the side entry sub back on surface, disconnect clamp and POOH with cable until  approximately  50m  below entry sub . Ensure the RHKC is installed on top (swabbing ).

Rig down sheaves and POOH logging tools

Hole problems

In case of stuck pipe: try to work string free, circulate . Use the jar only as a last resort .If unsuccessful, pull cable to side entry sub .

In case of well flow: retrieve cable if possible, otherwise cut cable above rotary and close BOP.

9.2 Recovery of Logging Cables under Pressure

General

Recovering unweighted logging cable by pulling through the lubricator while under well pressure is generally acceptable .

Adding sinker bars or weight above the weak point will hamper normal operations (not recommended).

Procedures

The operation carries out a higher than normal risk and requires specific procedures and extra precautions. The following points must be emphasised when recovering  the cables under pressure:

1. A safety meeting must be held with all staff involved to discuss the produce to be followed .

2. All personnel not essential to the operation are to be cleared from the wellhead rig floor area.

3. Ensure that proper means of communication between the operator at the lubricator and the winchman are available and in use .

4. Line up and test kill equipment before attempting to recover the cable . Also check grease injection equipment before commencing .

5. Lower top logging sheave as much as is practical to reduce free length of cable above the lubricator.

6. Do not use lubricator BOP rams to apply friction to the cable, apply sufficient grease injection pessure on the flow tube injection head to counteract/ control well pressure and reduce cable speed.

For more detailed information reference is made to the Integrated Service Contract manuals which will be available.

10. Stuck Tools

1. Keep the wire-line tension under constant review and in particular ensure that normal tension is known within 0.5 kN (100 lbs) at logging depth.

2. At the first sign of a sticking tool, alert the winch operator/engineer. Precise procedure to be followed subsequently depends upon a rapid assessment of the most probable sticking  mechanism. The four most probable causes of tool sticking are:

a)      Key-seated cable. This is caused by severe dog-legs, or as a result of the cable wearing a slot in the formation during a long logging operation.

b)     Key-seated tool head. This can happen in the vicinity of dog-legs, or in oval or key-hole shaped holes.

c)      Bridged hole. Often a result of shale collapse.

d)     Differential Sticking. This may occur when logging porous, permeable intervals in depleted reservoir zones, or intervals at much lower pressure than the mud column.

The procedure to be followed in the first three above cases (a, b AND c) is:

1. When an overpull of 2.2 kN (500 lbs) is reached, stop the winch, lower the cable until tension is 2.2 kN (500 lbs) below normal.

2. If the stuck tool has powered arms, close the sonde arms.

3. Reduce the tension to 4.4 kN (1000 lbs) below normal.

4. Observe whether the tool is still moving (in this case down).

5. If the tool is still moving, attempt to work the tool above the obstruction. While the tool will still move down the hole, do not apply an overpull more than 2.2 kN (500 lbs).

6. If the tool is NOT moving down, release tension further, to 6.7 kN (1500 lbs) or 8.9 kN (2000 lbs) below normal. Do NOT allow slack cable at the surface. Wait 5 minutes.

Note:    Do not exceed this limit without the approval of Base.

This procedure ensures that excessive pull is not applied in the initial stages, as this can jam the head, pads or cable into a key seat which can only be released by fishing. If the hole is bridged over, it is much better to be able to keep the tool moving below the bridge and attempt to work it through the obstruction than to lock it irrevocably into place with the first sharp pull.

When logging with a pad tool in porous and permeable sections of depleted reservoirs, differential sticking can be a problem. In this case, adherence to the above procedure may lead to unnecessary problems. If differential sticking is probable, follow the alternative procedure:

1. At the first sign of sticking, continue to increase pull to normal logging tension plus two thirds of nominal weak point strength.

Note:    Do not exceed this limit without the approval of the Base.

2. At 8.9 kN (2000 lbs) overpull, start to close the sonde arms.

3. If the tool comes free, re-open arms and continue logging.

4. If the tool does not pull free, reduce tension and work the cable up and down as in the first procedure.

If the tool is stuck, continue attempts to free it until the decision is made to cut the cable and strip over to the fish. The weak point must NEVER be broken when a tool is stuck in open hole EXCEPT when:

-       the cable has been stripped over and the head of the tool is securely engaged in the overshot, or

-       a decision has been made at Base either to abandon the tool, or to pull off and fish without overstripping.

Investigate the probable sticking mechanism by applying a stretch test, i.e. measuring the cable extension generated by 0.9 kN (200 lbs) increments of pull up to 8.9 kN (2000 lbs) above normal logging tension. Remember that, in deviated holes, friction at the dog-leg may give a false impression of key-seated cable.

Note: The incorporation of a down-hole tool head tension indicator in the tool string is being introduced on certain advanced telemetry tools. This device should improve the knowledge of down-hole conditions immeasurably, and may assist in avoidance of stuck tools, as well as   aiding in safe descent into highly deviated wells.