Intervention Barriers

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Godfrey Brooks
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1 Intervention Barriers A barrier is defined as a means of containing wellbore pressure and fluids. Two effective barriers are required for most intervention operations. Consider when barriers are effective (and when they are not) and how to back them up for safety. Must be rated to the maximum pressure that can be encountered. 1

2 Common Barriers Kill weight fluid column (not just a fluid column) monitored and tested Pipe rams when pipe is in the well Blind/Blind-Shear when no pipe is in the well Master valve when pipe is not in the well CT Flapper valves (dual flappers = one barrier) Stuffing box/stripper Rubber Downhole plugs Grease seal/ram for braided line (both are one barrier) 2

3 Barriers 1. Nipple Down Tree 2. Nipple Up BOP 3

4 Barriers last steps What s Left? 1. Hook up test and kill lines. 2. Test. TEST LINE Hammer Union & Bull Plug Flanged Choke Ported w/1-1/2 NP & Threads & 2-10K Needle Valves 4

5 Kill Weight Fluid KWF = Formation Pore Pressure (psi) / (0.052 * TVD to mid perfs (ft)) where: KWF = kill weight fluid in ppg TVD The kill weight fluid must occupy both the annulus and the tubing with no voids or other fluids involved. If the density and level of the fluid are not monitored, can the fluid be an effective barrier? 5

6 Difference between Surface and Downhole Barriers A surface barrier prevents escape of fluids from the well. A downhole barrier may also prevent crossflow between formations. 6

7 Multiple barriers The barrier during drilling is a well control barrier that has both hydrostatic and mechanical control points. A column of kill weight fluid, monitored and tested, is a common active barrier. 7

8 Double Bariers During wireline intervention, the control method is pressure control with two or more barriers. The barriers for wireline include: 1. Grease or oil seal on the wire (for dynamic sealing); 2. Packoff for static application 3. Blind/Shear rams 4. Master valve (can cut some wire, but poses a risk of valve damage). 8

9 Barriers for Intervention with Coiled Tubing Barriers include: 1. Stuffing Box 2. Coiled Tubing BOP 3. Annular Preventer (for sealing around BHA string) 4. Pipe ram below circulating cross or Tee. Stacked Barriers 5. Master Valves when CT and BHA are above the top Master Valve. 9

10 Producing Wells One Barrier Barriers for Producing Wells usually only one barrier for many areas: 1. Almost all flow/gathering lines, separators and pipelines. 2. The flow cross, choke body and other areas above the tubing hanger 3. Below the tubing hanger for gas lift supply 4. At any open shoe with gas lift supply 5. Uncemented casing below the packer 10

11 Live Well Workovers Top Hole - plug (WL or CT) set at or below packer - top of well is isolated. Used for: press test pickle/cleanout tubing replacement fluid unload/swap equalizing plug 11

12 Typical Conditional Barriers Considered a barrier during certain operations but not at other times. Examples: Pipe rams barrier only when pipe is in the well Blind ram, master valve, stripper rubber barrier only when pipe is out of the well Braided line rams barrier only with grease injection 12

13 Layout for a CT BOP 13

14 Ram Internals Ram blocks Lower left slip blocks Lower Right seal blocks Upper Right shear or cutter blocks 14

15 CT BOP w/ kill port 15

16 Rams are heavily greased Cleaning? Greased ram section in a BOP prior to the job. Effect of excess grease? 16

17 Open ram 17

18 CT Crushed by ram closure now, how do you recover it? Rams for CT must: 1. Center the CT in the BOP body 2. Center the CT in the ram element 18

19 Accumulator BOP accumulator pressure source 19

20 What if the flow cross leaks? Control point? 20

21 No secondary control below a flow cross 21

22 One approach to control 22

23 Stacked BOP An effective BOP rig-up. Note dual valves and flow control below the flow cross. 23

24 Develop Both Sides? May be practical for high risk wells. 24

25 Unusual Cases When running a BHA that cannot be sealed with a pipe ram or cut with a blind shear. Is a special barrier needed for the BHA? When changing the elements on a ram or stripper rubber. Is a backup needed? 25

26 The Two Barrier Rule Barriers may be the same in some instances. Both must be capable of controlling the full well pressure. Many barriers are conditional may need back-up. 26

27 Some Special Cases Snubbing or hydraulic workover The two (minimum) pipe rams are barriers, but a blind-shear is required for a second barrier while pipe is in the well. What is needed when an pipe ram element has to be changed? A second blind or blind-shear or master valve or other device is required when pipe is out of the well. 27

28 Hydraulic Workover Units 28

29 Pipe ram elements Pipe seal elements 29

30 Hydraulic workover unit showing the gas bypass tube between pipe rams. Hydraulic Workover BOP set 30

31 Special cases, continued Large BHA or BHA that cannot be cut. Annular preventer? Downhole valves (SSSV as a barrier????) SSSV s are not a good barrier if an object can be dropped from the tool. A dropped object can breach/break the seal offered by flapper type SSSV. Pressure operated downhole valves 31

32 Special cases, continued Fracturing Tree Saver Hydraulic deployment Second set of valves temporarily replaces wellhead valve control Stinger with seal isolates and locks-out wellhead valves 32

33 Tree Saver isolates existing wellhead with hydraulically deployed stinger with external seals and second set of valves. Frac Iron Connection Hydraulic cylinders Remote operated master valve Manual operated master valve Tree saver inserted and locked down. Mandrel or stinger with seals on exterior Hydraulic pistons Vent Valve Existing master valve on well Well master valve is closed 33

34 Special Cases, continued What is stability of the barrier? To outgassing (seal face failure) To high or low temperatures (does it weaken barrier?) To corrosion (components weakened by attack?) To erosion erosion of sealing surfaces To high or low pressure spikes To high or low tensile loads 34

Special Example - Inflatable Packers Are they barriers? What is the reliability? Do they stay put? Has a great deal to do with how much they are expanded and where they are placed.

35 Special Example - Inflatable Packers Are they barriers? What is the reliability? Do they stay put? Has a great deal to do with how much they are expanded and where they are placed. Good reliability when set in pipe Good reliability when placement slide is short (less than 1000 ft) Good reliability when expansion from initial to set is less than 2x. 35

36 Quiz - Barriers 1. What type of equipment must not be sheared in a well control attempt? 2. What type of event or action may render the following barriers useless? a. Blind ram, no pipe in the hole. b. Pipe ram w/ pipe in the hole. c. Stripper rubber on Coiled Tubing. d. Grease injector with E-line in the well. e. Flappers on coiled tubing. 3. For each challenge in problem 2, what is a 36

37 37 Quiz Barrier Failure Recovery from Problem #2. Failure Type Cause Recovery Blind Ram, face seals destroyed. Pipe Ram, w/ pipe in hole, no seal. Stripper rubber leaking on CT Grease leaking on E-line grease injector, not holding pressure. Flappers not preventing backflow on cleanout.

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