Category Archives: Workovers

Coil Drillouts3

Coil Drillouts Cubed.

When you are milling out plugs there is a tendency to stick with the status quo.. running super think gel sweeps and slugs of chemical.  Then after running these super thick slugs, pulling uphole and doing a “wiper” trip, or “short’ trip.  In reality, it is a waste to use viscosifying chemicals other than just enough FR  (Polyacrylamide -CH2CHCONH2)  to keep the circulation pressure low enough to keep moving without putting too much stress on the coil.

When your trying to get the mill/drill cuttings to transport to surface, a new logic applies;  keep the fluid as thin and turbulent as possible.  FR can’t pick up sand on its own; shear and turbulent action pick up the fine sediment and keep it suspended … same with plug debris.  The thicker you make the circulation fluid the worse the problem becomes – it just extrudes over the top of the sand and debris with no turbulent flow.

Thin out your drilling fluid – stop pumping sweeps.  Circulate fluid while moving slowly downhole, until all the surface returns are clean.  Instead of pulling short trips and getting wedged into debris, move downward slowly and let the well clean up just like you were drilling openhole.  When you reach the desired total depth, circulate clean again with about 300 ft/min or more annular velocity.  If you can get more annular velocity go for it.

SPE-187337-MS details the whole procedure needed to overhaul your current drillout program. It’s titled “Stop, Drop and Circulate; An Engineered Approach to Coiled Tubing Drillouts”  {It’s a reference to a popular 1980’s ‘clothing on fire; what to do’ campaign giving advise to ‘Stop, Drop, and Roll’}

(*Note :  The way that the well was stimulated will determine the rate of return you want.  If you flow back too aggressively after a crosslinked gel stimulation the small aperture of the perforations can cause washing out or pitting of the coil downhole.  Huge 100 mesh sand slickwater stimulation’s tend to leave large, tremendously eroded perforations behind that don’t tend to have the harmful velocities seen with small perforations.  If you get to greedy, you can end up causing coil damage.  With slickwater stimulation there is a much larger window… we really haven’t found out what you can get away with, but its a lot…)

The other thing to keep in mind is the size of the flowcross that you are using.  If you have to go cheap and get 2″ valves off the main bore, you run the risk of too much velocity across the coil tubing when the sand laden fluid erodes in transit through the orifice as it enters the 2″ ID of the flowcross.  Always try to get at least 1.5 x the diameter of the coil string for your flowcross when you drill out.  Use valves with a full bore opening when possible.

Collapsed Tubing

Collapsed Tubing Dimensions

When tubing collapses, sometimes you need a ballpark dimension to try and figure out what might be ‘looking up’ at you.

Just take the (ID x Pi /2) + (OD-ID)
2.441 * 3.1416 / 2 + (2.875-2.441)
7.6686 / 2 + (.434)
3.8343 + .434 = 4.2683 Inches

A slightly more complicated way involves using the outside circumference:
(((OD*Pi) – (OD-ID)*Pi  )/2 ) + (OD – ID)
((Circumference of Tubing – Circumference of Total Wall Thickness) / 2) + Wall Thickness
(((2.875 x 3.1416) – (2.875-2.441)*3.1416)/2) + (2.875-2.441)
(9.0321 – (.434*3.1416)) / 2) + .434
((9.0321 – 1.3635) / 2) + .434
(7.6686 / 2) + .434 = 4.2683

So… just over 4-1/2″
[This is if the tubing hypothetically flattens absolutely flat, which is not the case .. It does give a good estimate for selection of washpipe or other overshot / grapple tools needed to fish collapsed tubing.]

Packer

Set Down, latch on, pullover ’bout 10K# to make sure you’re latched. Set down three-thousand; Whip it Right, Hold the Torque, pull up 10K# over string weight.  Take off the wrench, and pull 20-25K# – go have a coca-cola – come back down, sink the joint, and come out of the hole.  Make sure you have good ‘back-ups’ so you don’t rotate, and don’t over-run the collars.

Exercise a little patience to let the elements relax after you release them; don’t be in a hurry.  Don’t forget to “sink the joint” meaning go down past the setting depth to make sure you actually have the packer on the end of the tubing, and that you have free movement.

WO Best Practices

Workover Rig Best Practices

General Do’s & Don’ts.

-Op check the BOP’s BEFORE you install them on the Well.
-Always use a Night Cap on the top of the TIW valve when you leave for the day.
-Visually insect that the Rams on the BOP are closed, and back them up at night when shutting in.
-ALWAYS get a Strap & Count coming out of the hole.  Account for every piece of tubing on location, whether you run it in the hole or not, that way you have a positive count.  Knowing what is on location before you trip back in is the right way, the only way.
-New rings are cheap – run them.
-Nipples should have needle valves then a gauge.  Don’t get into the bad habit of just putting a gauge into a threaded nipple.

When Pulling Rods

When you unseat the pump, don’t pull much more over 2#/Ft.  Example: at 10,000′ don’t pull more than 20,000# over rod weight.

  •  On-Off Tool. (Left Hand Release)  Set down about 3% from neutral weight, and put in left hand torque.  When you feel the tubing torque up, hold it in, and give a couple short bumps down to transfer the torque down through the deviations. Hold the left hand torque on the tubing  and come up slowly to neutral weight, or just below it.  The tool should be released, if not, repeat the procedure.  Once you start pulling and the tubing goes into a state of tension, the torque won’t transfer, it needs to be travelling in ‘compression’ to transfer the torque downhole.
    • Link to Weatherford ‘On Off’ Tool Document
    • Link to Tenaris Sucker Rod Technical Catalog
    • Link to Norris Care and Handling PDF

Removing Tubing Flange/Landing BOP’s

-Kill the backside with hot fluid. The extra stretch provided by the thermal elongation of the tubing will help with the amount that you have to pull when you unseat the tubing spool/tubing flange.

Pulling a tubing anchor/(no seal)packer and replacing it….

Obviously there a thousand ways to do this, on a thousand different wells…  this is just a set of quick notes on pulling and replacing tubing and a subsurface rod pump.

If you ever trip a TAC (Tubing Anchor/Catch), always replace it every time.  The shear pins get weakened from setting the assembly, and then overpulling to land the tubing.  Once the pins have been weakened, they can be susceptible to early breakage.  Replace the seating nipple while you are there. Save time and money by doing it right the first time.

Setting Depth- Look up the stretch coefficient in the Baker Book (or other source if you have it) and compute the stretch needed to land the tubing flange.

tubing stretch

(Set Depth in K/Ft) x (pull in K/Lbs) x (stretch coefficient)

2-7/8″ 6.5#/Ft tubing set at 10,000 FT with 20,000 pull = 10 x 20 x .22075 = 44.15″

For most situations the tubing will be in tension to keep it from buckling.  Link to a great article explaining this more in depth.

When seating the Tubing Anchor/Catch, use the torque of the hydraulics of the rig to determine that the number of turns is put in. Normally the tool spins an unknown amount going down hole.  Let the pressure gauge on the rig indicate when you are catching torque, it will usually increase about 300-500 Psi. Once you catch torque, pull into it a little, release, and pull into it again.  Then you can go down (about 20,000# up, 20,000# down for a 7″ TAC set at 10,000′ ) to make sure it is set.

When Running Rods

-If you are working when it’s cold out, check the Torque often when tripping in rods.  (about every 5 stands)… As the hydraulic fluid heats up it changes the torque at the tongs.

-Seating the pump…When in Doubt…Make sure you displace some fluid down the tubing past the Seating Nipple before you seat the pump, otherwise, debris can get into the seating nipple and prevent a good seal, or possibly prevent you from landing the pump seat.  Pump some heated fluid down the tubing, and then when you have movement (put the well on a suck) seat the Rod Pump.

Temperature affects many of the variables involved in torquing up rods.  The official recommendation from the API (API RECOMMENDED PRACTICE 11 BR (RP 11 BR)) Should be used as a reference.  it should still be out on ‘The Internet’ – try to Google it.

Sucker_Rod_CDCircumferential_Displacement

 http://petrowiki.org/Sucker_rods

-Electric Submersible Pump [ESP]

-When running a submersible pump, only use about 500 Psi closing force on the Annular Hydril, or risk smashing the lines/cable.

Have an Idea for a best practice?  send it to bestpractice@wellcompletions

What’s in a Well Name..

Have you ever wondered what the cryptic numbers are in the name of an Oil or Gas well?  Once you see how Sections of land are labeled, it starts to make sense.  The Sections of land are named using the Public Land Survey System (PLSS).  Here is a helpful article explaining the PLSS. There is a fair amount to it, so take a moment to read through, and get an understanding of the system.

Lets start with an example of a horizontal well.  Naming conventions vary from company to company, but for the most part some details about a well can be deduced from the name.

Say the well is named the Grassy Field 147-91-8-5-1H; Let’s decipher the different parts, starting with 147-91.  The 147 is the Township and it’s 147 x 6 miles North (or South) of the Baseline. The 91 is Range, indicating that it is 91 x 6 miles West (or East) of the Principle Meridian.  Those two numbers represent the 36 square mile ‘block’ that the well is in.

tmap3

The second part ‘8-5’ normally describes where the lateral starts and ends.  this is sometimes referred to as the Spacing Unit (SU).  So in this case the lateral most likely begins in Section 8 and goes to the north into Section 5

pls

If the name was instead Grassy Field 147-91-17-20-1H you could assume that the well ran in a Southern direction from Section 17 into section 20. The 1H part most likely identifies that it is the first well, and that it is (H) horizontal.

Some names don’t include the Township and Range, and may only include the Leaseholders Surname and the Section.  An example would be the Smith 36-25-A.

Use Caution when trying to decipher these names …. Sometimes a new owner takes over leases and bring their own naming system, but for the most part you can get a little bit of information from the name and figure out where the well goes.