Prior to pulling stuck drill pipe or stuck casing, carry out the following preparations:
1. Ensure that all surface pulling equipment is in good working condition. Do not exceed the maximum allowable safe working rating of the weakest link in the pulling equipment.
2. Check the Martin Decker weight indicator and the dead-weight anchor as follows:
a) Check the fluid level of the cylinder or sensator and fill the system if necessary, with the correct fluid and hand pump in the cylinder, bleeding air at the connection on the gauge.
b) Mount cylinder or sensator with outlets on top.
c) Check that the anchor is free to work. The anchor should be greased regularly and the anchor pins kept free of paint and corrosion. Once a week the pins should be pulled, cleaned and greased. The anchor movement should be checked using a pinch bar between the wheel and the stop of the anchor. By applying a force, the gauge should move quickly.
d) Check the gauge; read the proper dial which corresponds to the number of lines string. The pointers on the gauge should move freely without touching any other part of the gauge. Ensure that the damper is sufficiently open to allow fluid flow, yet prevent severe movement. Ensure the vernier is closed during trips and when jarring.
e) Check the hose for leaks, and ensure that it is not pinched. When moving the indicator break the hose at the self sealing union at the cylinder or sensator.
f) Calculate the amount of pull to be applied.
1. Effective Pull on Stuck Drill Pipe
When determining the pull on stuck drill pipe in a vertical hole the actual weight of the string in air is to be used and not the indicated weight as recorded by the weight indicator.
It is normal field practice to pull on stuck pipe up to 85% of the minimum yield strength of the (weakest) pipe in the string, unless otherwise advised by Base.
2. Stuck Casing
The maximum TOTAL surface load (NOT overpull) on casing shall not exceed the lower of:
- 62.5% of Yield strength of top pipe or thread (take weakest)
- 62.5% of Yield strength of weakest pipe or thread + Weight (in air) of casing above it.
Regardless of the calculated allowable loads, the safety factor for the block line shall never be less than 3. This may well be the limiting factor instead of the casing strength.
If there are angle changes in the hole and/or internal pressure inside the casing, the allowable surface load shall be restricted by the factor value in API Bulletin 5C2.
3. Freeing Stuck Pipe
Stuck Pipe in a Salt Section
When stuck in salt circulate fresh water around; the usual amount is 5 - 10 m3. Depending on the type of mud in the hole a 1 m3 spacer of diesel oil ahead and behind can be used. Displace the fresh water slowly around the drill collars to increase contact time (0,5 m3 per min.) and stop every 1 m3 pumped for five minute soaking periods. Remember to keep maximum pull while circulating and bear in mind the need for well control
Pipe Freeing Agent (PFA)
If stuck in any formation where differential sticking is possible (i.e. differential pressure of formation against mud weight in the hole is high), then a pipe freeing agent, (for instance a pipelax pill), shall be spotted as quickly as possible after the string sticks.
The following procedure shall be followed:
1. Clean out pill tanks.
2. Pump in diesel oil. An amount equal to twice the annular volume around the drill collars plus enough left inside the string to move the pill 0.1 m3 (0.6 bbl) every half an hour over a six hour period.
3.Add 25 - 50 ltr of PFA for each 1 m3 of diesel oil.
Note: If the mud gradient is up to 1.15 sg it is unnecessary to weight the pill unless advised differently by the Superintendent.
If a weighted pill is required then add a diesel viscosifier, in a concentration of 45 sacks per 15 m3 and then add barytes as required.
4. Pump the pipelax pill into the hole and displace until the 100% annular excess is around the DC's. Stop pumps and displace 100-150 ltr's every half an hour. Work pipe and torque-up continuously during the soaking.
Immediately the pipe is free start rotating and circulating.
a) Before pumping the pipelax pill, determine PC1, by taking some SCR's. If the well should flow, control can be regained by circulating out the pill using the choke to maintain PC1, for the chosen circulating rate.
b) It is important that considerable diligence be given to mixing a weighted pipelax pill to ensure that the pill has sufficient body to hold the barytes in suspension while there is no circulation.
c) A maximum of 24 hours after a pipelax pill is in place is an acceptable time period for working a stuck pipe. A decision on whether to continue working a stuck pipe after such a period shall be taken by the Superintendent.
d) While the use of a pipelax pill is generally associated with waterbased muds it should not be disregarded for a similar application in OBM.
e) If the formation/mud pressure differential is high, then consider reducing the mud weight in the hole before circulating a pipelax pill.
f) If acid is used, care must be taken especially during handling. Correct safety and protective clothing and equipment must be used.
g) The intentional influx of formation fluids to release the stuck pipe is not allowed.