Sequence of Operations:
1. M/U flow head assembly and pressure test selectively to 150 bar as follows:
1) From bottom up against bottom master valve.
2) From bottom up against swap and fail safe valve.
3) From bottom up through open fail safe valve against low torque valves of kill and flow line.
4) From top down against kelly cock.
Once the pressure test is successful, do not break the connection until the perforation is completed.
Note : - Prepare the BOP stack for running of annular operated tools. It must be possible to monitor pressure all times and bleed off at any desired moment. (Remove check valves if any). A 2", 1502 WECO thread should be available on the floor to hook up the pressure recorder.
2. M/U TCP string as per tool string diagram.
a) 5" bull plug.
b) 5" TCP's (RDX DP charges, 12 spf, 60 deg phasing).
c) 5" Safety spacer.
d) 3 3/8" Mechanical Firing Head.
e) 2 3/8" EUE Tubing (1jnt.).
f) X-O: 3 1/2" IF box x 2 3/8" EU.
g) 5" Radial Shock Absorber.
h) 5" Vertical Shock Absorber.
i) 3 1/2" Ported Sub.
j) 7" RTTS bottom Straddle Packer.
k) 3 1/2" DP (+/- 450 m)
m) 7" RTTS top Straddle Packer.
n) RTTS Safety joint.
o) FUL-FLO Hydraulic Circulating valve.
p) Jar
q) APR OMNI Circulating valve.
r) RD APR-TYPE "A" Circulating valve.
s) Radioactive Tag Sub.
t) 4 3/4" DC's (+/- 150 m).
u) 3 1/2" DP (to surface).
Note : - Measure the distance from mid-packer rubbers (bottom straddle) to top shot (should be 10.81 m). This is important as there is only 12 m between the bottom of the existing perforations and the top of the proposed perforations.
- Measure the distance from the bottom of the string to the top shot and from the top shot to the radio active marker sub.
- Ensure that the OMNI valve is in position 15.5 (refer to diagram).
3. RIH TCP string on 150 m of 4 3/4" OD Drill Collars. Drift DC's. Fill up with clean KCL brine. Test to 300 bar.
4. RIH on drifted, 3 1/2" DP to +/- 2372 m.
Note : - Sparingly dope pin ends of DP only.
- RIH 1 stand/minute. Fill up whole string with brine.
5. Rig up Schlumberger. Run GR-CCL and correlate. Perforation intervals as follows:
2297-2312 m AHORT (net 15 m)
2330-2347 m AHORT (net 17 m)
2362-2380 m AHORT (net 18 m)
Note : - Reference log LDL-CNL-NGS-AMS dd 11.02.88
- ORT-TBF = 7.98 m
- Determine gun spacing from position of radioactive marker.
- The top straddle packer should be above the top of the existing perforations at 1834 m.
- The bottom straddle packer should be below the bottom of the existing perforations at 2277 m.
6. Space out string such that the flow-head can be installed at an appropriate working height with the guns at the required depth.
Note : - Ensure the kelly cock is not across the BOP rams.
7. Set RTTS Straddle Packer with 20,000# weight.
Note :
- Prior to setting packer, at the packer setting depth, pull an extra 15 cm to compensate for the packer stroke.
- Mark the string at RT level as the packer is set. Check the distance from the original mark to the new mark and check against the space out calculation.
8. R/U kill line to the pump unit and the flow line to the choke manifold. Pressure test the lines to 200 bar against the flow head and the choke manifold. Rig up nitrogen lines and pressure recorder.
9. Close rams, pressure up the annulus to 1500 psi, and cycle OMNI valve to circulating position 11.5. Hold annulus pressure at first cycle for 10 minutes to test packer seat. Halliburton service personnel should be on floor.
10. Pump nitrogen to displace 600 m of brine out of the drill string.
Note : - Ensure the annulus is open during this operation.
11. Cycle the OMNI valve to well test position 2.5.
12. Install Vann Systems shot detection equipment.
13. Drop Detonating bar. Detect guns fired.
14. Flow well until zero pressure at choke manifold (or brine cushion reaches surface).
Note :
- The brine cushion should not reach surface due to the low reservoir pressure, however, due to the high porosity of the KNNCY (PI=52-76 m^3/d/b), pressure equalisation will occur very rapidly. In order to circulate out the perforation debris it is important to reverse circulate the tubing contents at the earliest point after equalisation.
16. Close the pipe rams and cycle the OMNI valve to position 11.5 (circulating position). Reverse circulate with clean brine until the returns are the correct weight. Dump returns until clean brine returns observed. Reverse circulate at least twice the hole volume.
Note : - If the OMNI valve does not function with annulus pressure, open the APR-TYPE "A" circulating valve by putting an extra 1000 psi on the annulus (total of 2500 psi=172 bar).
17. Cycle OMNI valve to position 2.5 (well test position) and observe well, keeping tubing full, for 10 minutes.
18. Open rams and unseat the packer. Observe the annulus.
19. Reverse circulate tubing/conventionally circulate?. Observe well.
20. Rig down surface equipment and POOH.
Note : - Be prepared for losses. If possible, just live with the losses; keeping the hole filled. If losses are large, cure with HEC. As a last resort use salt graded LCM.
Attachments:
- Downhole sketch.
- TCP string configuration.
- Straddle packer diagrams.
- OMNI valve toolposition diagram.
Contractors:
- TCP ASSEMBLY: Vann Systems
- FLOW HEAD/TEST STRING: HES
- NITROGEN SERVICES: HES
- GR-CCL: Schlumberger
General notes:
- All depths refer to TBF unless stated otherwise.
- KCl brine: SG 1.08, 3% KCl with 1 litre/m^3 Coat B1400X inhibitor (pH=10). The brine does not have to be filtered on site, but should be ordered as a 20 micron, filtered brine with less than 20 ppm solids. It is very important that all the hoist tanks; and the trucks used for the transportation of the KCl brine, are clean.