2 Stage and Liner Calculations

Transcription

1 2 Stage and Liner Calculations Module CF111 NL 08 Sep 99 1 Initials

2 What is Two Stage Cementing? The cementing of a string of casing in two stages!! (Using a stage collar) 2 Initials

3 What is Two Stage Cementing? The cementing of a string of casing in two stages!! (Using a stage collar) SECOND STAGE STAGE COLLAR FIRST STAGE FLOAT COLLAR FLOAT SHOE 3 Initials

4 Why Two Stage Cementing? Reduce Hydrostatic 4 Initials Lost Circulation Zone or Low Frac Gradient Cement very long intervals (time / volume limitations) TT or Logistics problem Reduce use of expensive slurries due to special well problems: Economy Salt Zone Gas Zone Incomplete fill up Ensure part of annulus is free of cement

5 Alternatives Use of lightweight slurries Foam Cement Litefil This leads to: Complex designs Logistical problems Expensive slurries 5 Initials

6 Hardware What hardware is required that is different from a single stage cement job? Stage collar Plugs 6 Initials First stage wiper plug Opening plug/bomb Closing plug (a "Bottom" plug for the first stage is optional) Landing collar seal plate

7 Stage Collar SHEAR PINS Running in Position 7 Initials

8 Stage Collar SHEAR PINS OPENING BOMB Running in Position Cementing Position 8 Initials

9 Stage Collar SHEAR PINS CLOSING PLUG OPENING OPENING BOMB BOMB Running in Position Cementing Position Closed Position 9 Initials

10 Stage Collar Does Not Open! Possible Solutions : Wait: Bomb may not have arrived yet. Increase Pump Pressure. 10 Initials NOTE: Max P. or Burst P. of casing. Run D.P. in the hole and try to open mechanically (e.g. weight). Perforate above collar and cement. NOTE: Might perforate through 2 casing. No mechanical closing.

11 Where to place 2 Stage Collar Problem Formation Lost circulation, Salt zone, etc. 11 Initials

12 Where to place 2 Stage Collar Problem Formation Lost circulation, Salt zone, etc. TOC STAGE COLLAR PROBLEM FORMATION 12 Initials

13 Collar Inside Previous Casing Many clients insist on this Initials

14 Collar Inside Previous Casing Many clients insist on this... STAGE COLLAR 14 Initials

15 Collar Inside Previous Casing Many clients insist on this... STAGE COLLAR Why? 15 Initials To avoid jetting effect on the formation while circulating/cementing To ensure that if the collar fails to open, at least the open hole section is cemented

16 To WOC or not to WOC...That is the Question Guideline: WOC: YES!..Height of the 2nd stage slurry may fracture the "problem formation" Otherwise - NO ALWAYS - Open collar immediately and circulate out excess cement. Note: Control circulating pressures, not to fracture any weak formations. 16 Initials

17 2-Stage Casing to Wall Packers STAGE COLLAR CASING / WALL PACKER Purpose To give an extra seal below the stage collar How do they function? 17 Initials As the wiper plug (first stage) seals, pressuring up shears some pins and displacement fluid is pumped into the packer, inflating it.

18 Some Other Points The stage collar is eventually drilled out leaving the same "drift" as the rest of the casing. A stage collar is considered to be a "weak" point in the casing by many clients and so avoid using them. 3 Stage cementing is the same as 2 stage, but with 3 Stages. 18 Initials

19 Job Procedure 2-Stage Pressure test lines 19 Initials Pump wash/spacer Pump slurry Drop "First Stage" plug Displace: Bump Plug - Check Returns Drop Bomb - Wait Allocated Time Pressure Up to Open Stage Collar Circulate (W.O.C. if Required) Steps [2] and [3] Again - increase slurry density at the end Drop "Closing Plug" Displace - Close stage Collar Check Returns

20 2-Stage Cementing Job - Example 13 3/8 68 lb/ft Casing 4 3 Top of cement at 2461 feet 13 3/8 shoe at 2789 feet 9 5/8 Stage collar at feet 12 1/4 O.H / lb/ft Casing 9 5/8 Float collar at feet 9 5/8 Shoe at 6398 feet 20 Initials

21 2 Stage Cement Job - Answers 21 Initials First Stage Slurry Volume: [( ) x ] + [( ) x ] = ft 3 First Stage Displacement Volume: x = bbls Second Stage Slurry Volume: [( ) x ] + [( ) x ) = ft 3 Second Stage Displacement Volume: x = 302 bbls

22 PROBLEM 1: Frac Gradient: 0.8 psi/ft Mud: 12 ppg Problems PROBLEM 2: Frac Gradient: 0.8 psi/ft Mud: 11.2 ppg 4100 salt zone 2400 salt zone weak formation weak formation FG: 0.6 psi/ft FG:0.68 psi/ft TD:8400 TD:10200 Answer the following: 1. Would you recommend a 2-stage? Why? 2. What depth would the Collar be? 3. What is the maximum density of slurry possible during the first stage (assume cmt to stage collar)? 4. Where would the TOC be for the first stage? 22 Initials

23 Liners What is a Liner? 23 Initials

24 Liners Any string of casing whose top is located below the surface, hung inside the previous casing and is run to its setting depth by drill pipe. LINER HANGER OVERLAP FT CASING SHOE 24 Initials

25 Prime reason: Why Liners? Save $$ (Cost of 1 Joint of Casing can be $3,000!) Cover Corroded/Damaged Casing Cover: Lost Circulation Zones. Shales or Plastic Formations Salt Zones Deep Wells: Rig Unable to Lift Long String of Casing. 25 Initials

26 Types of Liners Production: 26 Initials Most common Save $$ Slotted liner Intermediate/drilling: Cover problem zone in order to be able to continue drilling Tie-back/liner complement: From top of existing liner to surface, or further up casing to cover corroded or damaged zone.

27 Tie-Back (Liner Complement) The integration of the liner with casing run to surface 27 Initials

28 Tie-Back (Liner Complement) The integration of the liner with casing run to surface TIE BACK STINGER WITH SEALS LINER 28 Initials

29 Tie-Back (Liner Complement) The integration of the liner with casing run to surface TIE BACK STINGER WITH SEALS LINER This is often done if production is commercially viable or there is damage to casing above the liner 29 Initials

30 Procedure for Setting Liner RIH with drillpipe At liner hanger depth, condition mud (Reciprocation / Rotation) Release slips (liner hanger) (Rotation - mechanical pressure - hydraulic) Set slips, release liner weight, check to see if running tool is free Pump mud - to ensure free circulation Cement / Displace / Bump plug / Bleed off Release setting tool POOH above TOC and circulate NOTE: A liner swivel can be run below the hanger to ensure that the tool can be rotated even if the liner is stuck or set. 30 Initials

31 Liner Overlap Cementing the liner lap is critical. Too much cement above the liner hanger is not recommended So make sure that uncontaminated cement is present at the liner lap - washes and spacers / WELLCLEAN If not, there is communication from the annulus to the formation 31 Initials

32 Recommendations for Liner Cementing Ensure rheology of cement system is adequate for 100% mud removal Turbulent flow, if possible Consider 5-10 min. contact time at liner lap Batch mix cement Minimize U-tubing effect Rotation of liner during cementing (special bearing in tool) Adequate mud conditioning prior to cementing 32 Initials

33 Job Procedure Liner Pressure test lines. 33 Initials Pump wash/spacer. Pump slurry. Drop "Pump Down" plug (or drill pipe wiper dart). Displace To running tool Shear "Wiper Plug Displace to Float Collar Bump plug/check for returns. Release tool. Pull up to T.O.C. and circulate.

34 Liner example: WELL DATA 1) Well Information: 34 Initials 9-5/8" 47 lb/ft intermediate casing surface to " 29 lb/ft intermediate liner 6200 ft to 10,500 6" OH to TD at 14,500 DP 3-1/2" lb/ft 4-1/2" lb/ft liner required 14,400 to 400 inside 7" liner. FC 80 above shoe. 2) Cement required to TOL with 20% excess in OH 3) Calculate: Slurry and displacement volumes Job Procedure

35 Liner example: WELL SCHEMATIC 9 5/8 casing 47 lb/ft 3 1/2 drill pipe 13.3 lb/ft 9 5/8 casing shoe at 6,500 ft 7 liner 29 lb/ft Top at 6,200 ft 7 liner shoe at 10,500 ft 6 Open hole + 20% Excess 4 1/2 liner 16.6 lb/ft 10,100ft ; 14,320 ft 4 1/2 liner shoe at 14,400 ft 35 Initials

36 LINER example: Calculations 36 Initials 1) Slurry Volume: Volume #1 = ft3/ft x 400 =39.2 ft 3 Volume #2 = ft3/ft x 3900 x 1.2 = 402 ft 3 Volume #3 = ft3/ft x 80 = 6.2 ft 3 Total Volume = + 80 bbls = ft 3 2) Displacement: Drill Pipe = bbl/ft x 10,100 =74.9 bbls Liner = bbl/ft x 4220 = 57.8 bbls Total Displacement = bbls Max. overdisplacement = (80 x ) / 2 = 0.55 bbls

37 37 Initials Liner example: Job Proc 1) Mix Spacer and/or CW 2) Pressure test lines; 3) Batch Mix Cement Slurry; 4) Pump Wash and/or Spacer; 5) Pump 80 bbls of Slurry; 6) Drop Pump Down plug; 7) Displace with : + 74 bbls to the running tool and slow down flow rate to Shear Wiper + 75 bbls, then RESET VOLUME and displace 57.8 bbls to Float Collar. Maximum of 0.5 bbls over displacement if necessary. 8) Bump plug / Bleed off / Check for returns; 9) Release running tool; 10) Pull out up to TOC and Reverse Circulate.

38 HOMEWORK Liner Cementing Calculations 38 Initials

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