a guide to sidetracks

“A guide to sidetracks “

Any suggestions, please mail me at: [email protected]

For the practicing professional.



Contents.

1. Tools: a. RSS ( Push the bit ): b. RSS+ Motor: c. Steerable Motor MWD: d. Steerable Motor + Gyro: e. Rotary BHA ( Dumb Iron + Single shot ):

2. BHA Design: a. Bit: b. Motor: c. Universal Bottom Hole Orienting sub (UBHO): d. Drill collars: e. HWDP: f. Jars:

3. Well Condition: a. Cement Plug. b. Open hole ST. c. Whip stock. d. Casing window ( Section windows ) :

4. Low side Vs High side:

5. Change MTF to GTF of MWD tool to about 1 deg at surface.

6. Preparing the region above the ST point.

7. Initiating the Sidetrack.

8. DLS in original hole: 9. Choice of ST point. 10. Pilot Hole drilling: 11. Time Drilling: 12. Cuttings from shakers: 13. Jump in Bit inclination: 14. Near Bit Inclination. 15. Seperation ratio.



16. Reactive Torque: 17. Parameters: 18. Hole Inclination: 19. Formation Hardness: 20. Floater operations:

a. Ocean heaves:

b. Surface Tool Face on Rotating Drill ships:

c. Leaking Motion compensators:

21. Sidetracking a Radio Active Fish:

22. Special Bits:

23. Turbines:

24. BHAs examples.

a. 9 5/8” Vertical Whipstock exit with Motor.

b. Motor RSS through Whipstock window.

c. Jetting in Casing Section Windows.

d. Gilican build Assembly.

e. 36” Conductor jetting:

25. Well: SY 524 Sidetrack Plan 26. How not to Sidetrack. 27. A good hook hanger case.



Tools:

RSS:

Sleeve Rotation: The vector sum of the pressures on the 3 ribs is the tool face, opposite to which the RSS is “Pushing”. These rib pressures need a finite time to readjust when ribs change position. If the ribs rotate faster than this finite time, the resultant force vector will not be acting in the desired direction. 10 to 20 minute per revolution is very good. Anything less than 5 min per revolution, reduce GPMs to increase friction at the ribs / hole wall. Reduce GPM to minimum for tool power up. Sometimes even below, to power down the ribs, drill 10 ft & then power up again when ribs come into the new hole. The key is to - Stick the ribs. In Kuwait the local workshops have machined vertical grooves on the ribs to increase wall friction. In 8 ½” hole size tool, the ribs can expanf max about 9”. But if the formation is washing off to larger caliper, it wont work.

RSS+ Motor:

Particularly useful for sidetracks from vertical. Loose unconsolidated cement.

Make a Slide with full forces on the RSS, highside & lowest GPMs just to power up the tool, treating it just like a motor at 2-4 ft/hr ROPs.

Also when LWD tools cannot be rotated in the high DLS whipstock window, the motor RSS can extend the rathole with a slide, till the tools are clear of the window.

Steerable Motor MWD:

Steerable Motor + Gyro:

Rotary BHA ( Dumb Iron + Single shot !):

BHA Design:

Bit:

More rows of cutters – More side cuts per revolution

Shoulder cutters.

Gauge Length.



Total Bit Length.

Motor:

Bend: Choose the Maximum allowable bend setting with minimum surface RPM allowed.

Motor near bit stabliser (UBHS): Vertical Sidetracks / Sidetracks From high side – Use them. But always 1/8 Under Gauge.

Motor top stabliser: Avoid unless definite reason exists in favor.

Universal Bottom Hole Orienting sub (UBHO):

Drill collars:

Spiral preferred.

Use More numbers for sidetracks from low sides.

Don’t use for vertical sidetracks / Sidetracks From high side.

HWDP:

Will give lesser reactive torque. Hence Great with gyro orientation & no MWD toolface.

Use Max numbers in Vertical hole / High side ST.

Spiral preferred.

Jars:

Always use them because:

GPMs would be typically low.

Lots of stationary time and chances of differential sticking.

Well Condition:

Cement Plug.

Cement Dressing: Dressing the cement from the top of cement to the ST point is very important. It evaluates to 3 scenarios. Good cement, Poor cement & the most probable medium hard plug. Accordingly 3 different lines of attack get planned.



Begin with a thumb rule: 5 Tons / 50 rpm Rotary BHA = 5 min per meter : Good sidetrack Plug.

If trying from vertical, with a weak cement, Go for a Slide with the Motor RSS. Use 100% effort, high side. Chain brake for 10 min then Keep moving at 1-2 ft/hr. GPM minimum to just power up the tools.

Open hole ST.

Parent Welpath ahead – have a look at the surveys of original hole.

Take Near bit inclination readings. More recent reading are more reliable.

If it’s a planned sidetrack a Build & Turn Ramp should be drilled in the parent hole from the ST point, in a direction opposite to the ST plan.

Whip stock.

o The vertical 9 5/8” whipstock exit, turns about 20 deg right during the process of milling.

o Choose the whip setting direction such that +/- 25 deg should not create a problem for the plan ahead. Many well planers generate well paths turning at huge rates at very low inclinations. Such turns could not be monitored because of the casing interference below. Hence choose the direction where the inclination has reached say 5-6 deg.

o There is always a scribline error. Keep it minimum. o The whip stock may give less than 3 deg inclination causing High side

Toolface not to be available. Mag tool face will be wrong due to the casing below.

o Change MTF to GTF of MWD tool to about 1 deg, Before RIH. o Most of times, the bend motor will pass the whipstock, oriented

highside. Keep a mark on the drill pipe. Crosscheck when we run the gyro.

o Mag interference, on MTF & Survey Azimuths, becomes practically acceptable when C-C is about 12-15 ft.

o Ratholes upto 10 ft is fine. Beyond 10 ft, there arises a possibility of the mill drilling back into the casing below & reentering the well. We have seen this happening more than once.



Casing window ( Section windows ) :

30 ft window is required as a minimum. Cement plug is required. Sidetracks can be done by:

SDMMotors- Gyro + UBHO.

Jetting with Rotary dumb iron BHAs.

This is an extreme cost saving procedure routinely used in Mumbai offshore in 13 3/8” section windows. Savings of whipstock, Motors and most of times even the MWD.

RSS: will be able to perform a blind Kickoff from vertical.

Low side Vs High side:

In Open hole ST the high side option is ruled out.

On the same logic, if the cement plug is not tested to be hard rock, its always recommended to go Low side.

Further a low side ST does not mean we need to drop the inclination by 1-2 deg, If TVD / water contact is of great concern, the ST may just be initiated on the low side… say 3 feet of pure drop. Then the toolface can be gradually turned in steps towards 90 / 270 so as not to lose TVD and keep on separating.. say for the next 20 ft. the well path can now be picked up. With motors remember that turning from low side to 90 left is always easer done because of the reactive. Just a few psi more on the motor differential.

Change MTF to GTF of MWD tool to about 1 deg, Before RIH

o The whip stock may give less than 3 deg inclination causing High side Toolface not to be available & the Magnetic tool face will be wrong due to the casing interference thus making MWD kickoff impossible.

o A gyro tool face could be a solution, if planned for. o A simpler solution is to reduce the MTF to GTF swithover of the tool. There is a

loss in toolface accuracy, but nothing substancial.

Preparing the region above the ST point.



o Clean the hole from cement with higher flows. o For low side ST, reciprocate / ream to cut on the lower side for the BHA length(

15 ft minimum)

Initiating the Sidetrack.

o Sit at the ST point for about 30 minutes with max force, desired toolface, minimum GPM before time drilling. Start time drilling in millimeters. This is the most difficult of times when the side cutters are just scratching the smooth walls of the well bore, trying to initiate a ledge which does not yet exist.

DLS in original hole:

DLS has 2 components. Build & Turn. Atleast one of these has to be mathematically exceeded, in order to sidetrack.

Always initiate a sidetrack attempt, from a vector, opposite to the original DLS at the point chosen for ST.

Once the ST has initiated it can always be slowly turned anyway around, not necessarily dropping the inclination by a huge amount.

Choice of ST point.

Highest DLS in Build. Possibly an opposite turn.

Highest inclination.

Never a dropping section. Even a tangent is preferable.

Choose a High TVD to avoid hitting water zones below. We don’t need just a shallow TVD number, but thicker margins from the unwanted zone below. This can be had from the geological model being used by the RNS guys or even the client geologist.

Mudlogging ROP charts / Lithology charts should only for added reference. Too many ifs and buts in there.

MWD formation logs: If they do indicate a drastic change say from Very hard to soft – add this information.

Drill pipe tally : The driller might run a stand less or more from derrik ! Imagine the the bit trying to sidetrack inside casing. The main side cutters would be damaged, by the



time the error is noticed, the client would not POOH to check bit now, until the attempt fails altogether. Bad dreams for us. So keep a count of the pipes on derrik.

Pilot Hole drilling:

Well planners would typically design a neat tangent below the casing shoe to the pilot hole TD. Then the DD is supposed to ST from a weak cement plug, in a tangent !

Try this : From the planned ST point, build & turn 100 ft, with a DLS of say 4 in the opposite direction of the planned ST well path. Hold for 50 ft, then Drop & bring back the well to the planned Pilot hole trajectory. Later, after clearing the cement plug to this point, sidetrack from Low & opposite. It becomes easy & fast too.

Time Drilling:

Time drilling means to give enough time to the side cutters of the Bit, so that they may be able to:

1. Create a small wedge in the side wall.

2. Continue to enlarge this created wedge without jumping over to the existing hole.

Magnify the MWD screen showing standpipe pressure & the block height – each step down of the block height will show a 10-50 psi increase in pressures, whenever the Bit / Motor is doing some cutting. This differential will be on the lower side say 10 psi when the cut initiates. It will gradually grow as more and more of the bit enters the new hole.

Fig-1 Progress of a sidetrack.

Even in stage 4, it now becomes increasingly difficult to reenter the parent hole above, more so with a dropping BHA. Note the restricted diameter in between the 2 holes. This would typically be the situation after 5 meters of time drilling in 8 ½” horizontal open hole ST with a near bit inclination drop of about 1 deg.



Gravity & BHA weight, is either with you, or is against you, depending on hole inclination.

Gravity is always against you when trying high side / from Vertical. Here time drilling rate should be fast enough not to allow the BHA to fall back due to washing away of the cement support from behind.

Increase ROPs in steps “only after” getting confirmed positive answer from the previous increase.

1. ROP 1 ft/hr. 2. Doing Good. 3. Increased ROP from 1 to 2 ft/hr. Observe.

NBI jumped ? Any negative ? If yes go back to step 1. Else continue.

Ignore evey phone call. Patience is the key. Only you will be held responsible & carry the guilt if the ST fails.

Pipe marks: Its always helpful to keep the pipe marked in 1/12 feet. This helps when you need to Pick up in any emergency. The MWD depths may change.

Draw works marks: It’s a good tool to help the driller in maintaining small feeds. A large feed by the driller can cause the Bit to jump off / damage the embryo ledge and you may have to start all over again.

Cuttings from shakers:

Nothing better than collecting samples yourself. Be realistic in sample collection. Don’t choose anything, what we need is a true sample. This is a very important & direct data. Keep them arranged time wise / depth wise.

Jump in Bit inclination:

Back off to Zero ROP.

Pick Off bottom to last good point above.

Sit there for a good 10 min.

Restart with 1 ft/hr.



Near Bit Inclination.

Seperation ratio.

The point of ST for both well paths is definite and the very same, whatever be the position uncertainty of the parent from surface. Hence while estimating relative positional uncertainty between the parent & sidetrack well paths, start the ellipses from the point of ST and not from surface ( which will always be huge).

Reactive Torque:

5000 ft. Vertical whipstock window.

12 ¼”Tricone IADC code 5-1-7.

25-50 psi differential on 8” motor.

100 ft of continuous slide, at original Gyro Orientation.

Expect Survey Azimuth 75 deg Left of Gyro orientation.

Plan to be on the safer side.

Parameters:

High GPM will help a low side sidetrack.

High BHA weight ( More DC ) will help a low side sidetrack.

High RPM will help a low side sidetrack.

Low WOB will help a low side sidetrack.

Low ROP will help a low side sidetrack.

GPM will go against you from a vertical well.( Note: A vertical sidetrack is always a highside sidetrack )

Hole Inclination:

Low angle / Vertical:

Not possible without cement plug.

Medium:



Cement unconsolidated:

Good Cement:

High Angle

Formation Hardness:

If the cement is harder than the formation, the well will sidetrack automatically.

Parameters:

12 ¼”

GPM .

RPM.

ROP.

WOB.

Watch out.

Floater operations:

Ocean Heaves: Compensators will never be 100 % effective & the driller will not be able to maintain a constant WOB / Differentials. Use a Tricone Bit. That’s the key which helps. Sliding with a PDC at deeper depths & some formation hardness becomes extremely difficult.

Surface Tool Face on Rotating Drill ships:

Note the Heading of the Drill ship. Then mark your pipe & maintain the Toolface. Inform the ships bridge, through the Company man , to positively let the DD know of any change in the ships heading. ( they normally keep the ship aligned with the current to minimize thruster power.)

Leaking Motion compensators:



Leaking motion compensators could be a blessing during the ST from a floater. A leaking compensator would slow & steady feed the drill string down with no intervention from the driller. Happy time drilling.

Sidetracking a Radio Active Fish:

Definite separation is required as per regulations. This separation excludes the ellipses of uncertainity of both well paths, starting from the common point of ST. Go with the Max Allowable bend on the motor. Minimum GPM and time drill at a typical 1 m/hr. Have in mind to trace the motor curvature in the hole. Tell all to expect large DLS. They would later need to ream the DLS out once the radioactive fish is ST. We did create DLS of 11s in 12 ¼” hole with 8” Ultra motors 2.5 deg bend, in a similar job which was completed successfully.

Special Sidetrack Bits:

Turbines:

BHAs examples.

9 5/8” Vertical Whipstock exit with Motor.

8 ½ TCI. IADC 5-1-7.

6 ¾” SDMM 1.8 deg bend. 8 3/8” UBHS, No top stabliser.

6 ¾” MWD tool. ( MTF to GTF =1 deg )



6 ½” UBHO

9 x 5” HWDP.

6 ½” Jars.

9 x 5” HWDP.

Motor RSS through Whipstock window.

Use more flex subs. Use leaste stablises.

Jetting in Casing Section Windows.

12 ¼” TCR IADC 1-1-7 ( 2 x Blinds, 1 x 24, 18 c)

12 ¼” NBS

UBHO ( Align to Bit nozzle )

1x NMDC or use a MWD tools.

3x 8” DC

6x 6 ½” DC

9x 5” HWDP

6 ½” Jars.

9 x 5” HWDP.

Gilican build Assembly:

12 ¼” TCR IADC 1-1-7

12 ¼” NB

(Totco ring for single shot)

1x NMDC or use a MWD tools.

3x 8” DC



6x 6 ½” DC

9x 5” HWDP

6 ½” Jars.

9 x 5” HWDP.

30” Conductor jetting:

Inner String:

Bit

Motor

Inclinometer.

DC

HWDP

Jar

HWDP

DCART tool.

Outer String:

30” Conductor

Well head housing.



Well: SY 524 Sidetrack Plan

9 5/8” Casing Shoe 10272 ft.

Bit PDC security. 2”+ 2” Gauge Length.

Motor In hole: Yes

Inclination: 59 deg.

Formation: Arab A / B.

Time elapsed after Cement Plug placed: 24 hrs.

27 Jan 2014.

Test Cement Plug.

Approach plug with 450 GPM and 20 RPM from surface.

Notice Pressure increase & WOB increase to record Top of cement.

WOB 10 K / RPM 50 / 500 GPM Start Drilling Cement.

1. If ROP 40 ft / hr or less, consider a good Plug. 2. If ROP more than 80 ft / hr, consider a weak plug & Propose Wait On Cement to

harden plug. 3. If ROP Between 40-80 ft/hr consider a Gravity assisted Time Drilling approach from

gravity Tool Face 175 R.

Case 1: Good Plug.

Steer Mode with SF 90% & SD 150. GPM 450. RPM 120-150.

Drill with 20-30 ft / hr observing the NBI. If NBI indicates a dropping trend, Drill till inclination falls 1 deg less than the pilot hole. Then Steer Right with 50 % Walk Force holding this inclination for 75-100 ft before steering ahead..

Case 3: Medium Plug.


Drill with 15-20 ft / hr observing the NBI. If NBI indicates a dropping trend, continue till inclination falls 1 deg less than the pilot hole. Try this maximum for 30 ft of Plug Length.

Else start Time drilling at 2 ft / hr and 450 GPM.



Drill till inclination falls 1 deg less than the pilot hole. Then Steer Right with 50 % Walk Force holding this inclination for 75-100 ft before steering ahead..

Case 2: Weak Plug.


Drill with ROP 2 ft/hr observing the NBI. If NBI indicates a dropping trend, continue till inclination falls 1 deg less than the pilot hole. Try this maximum for 30 ft of Plug Length.

Follow Openhole sidetracking procedures with Ribs Off & involving Time drilling at 2-3 ft. This is a gravity assisted method & patient is the key. It may take upto 15 hrs or more depending upon the formation hardness.

Time Drill till inclination falls 1 deg less than the pilot hole. Then Steer Right with 50 % Walk Force holding this inclination for 75-100 ft before steering ahead.

Dress Cement to Sidetrack point.

Case 1: Good Plug.

Use Steer Mode with SF 90 % & SD 45. GPM 550. RPM 120-150.

With a hard plug it may be difficult to continue in the Long open hole & it may sidetrack on its way throught the Build up section. If very hard cement while drilling out of casing then hold back on weight to avoid jumping off the cement plug directly under the shoe. Incase this happens, Steer Right with 50 % Walk Force holding 1 deg lower inclination for 75-100 ft before steering ahead.

Case 2: Very Weak Plug.

As Sidetracking will be Difficult, Attempt to sidetrack early from a Build up section around 10650 ft or less after discussing.

Use Steer Mode with SF 100 % & SD 45. GPM 550. RPM 120-150 for dressing the plug.

At any Point if its noticed that the Hole is sidetrack, Steer Right with 50 % Walk Force holding 1 deg lower inclination for 75-100 ft before steering ahead.

Case 3: Medium Plug.

As Sidetracking will be relatively difficult, Attempt to sidetrack early from a Build up section around 10650 ft after discussing.

Use Steer Mode with SF 100 % & SD 45. GPM 550. RPM 120-150.

At any Point if its noticed that the Hole is sidetrack, Steer Right with 50 % Walk Force holding 1 deg lower inclination for 75-100 ft before steering ahead.



26. How not to Sidetrack.

GPM & RPM & WOB are the 3 simultanous requirements to make a hole. Cut any one to Zero/ Minimum & we cannot make a new hole. Try to keep these parameters at the Minimum while keeping high ROPs. Clean up during the up wash.

Use a Bit with damaged side cutters. Try to get it balled up initially by working with no GPM for a short while.

Motor orientation is well understood.

RSS should also be “oriented” with the same parameters as while drilling.

Slick BHA normally passes through Build sections, but is not advisable to work with. In case it is expected to work in a Build section use a Rotary Build BHA ( 0’ or 0-60’ or 0-90’)

A Bull nose is good. But it should be short. Say 3-4 ft.

27. A case for hook hanger.



My heartiest regards to a few experts in this field:

SK Sharma.

HV Ramesh.

K. Kamal.

N.Narayan.

Late Mr Murty.

Neeraj Shukla.

SK Bhowmik.

MK Gupta.

Roy Choudhury.

And my little family:

Anu, Babu & Boby.

a guide to sidetracks

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