Reading a wellbore Schematic

Wellbore Schematics
• Potential
– An informative layout drawing of what is in the well,
• Problems
– Accuracy is not always good,
– Incomplete or erroneous schematics can seriously
mislead a design and may lead to a serious failure.
– Well components change with time:
• Replacements not recorded
• Corrosion or damage weakens the components.
www.GEKEngineering.com
1
Example Schematic – sub sea well
What information is available on new well?
1. Pipe size, end of the string.
2. Location of restrictions.
3. Deviations, dog legs
4. Overlaps
5. Shoulders
6. Pay
7. Fluid behind the pipe
8. Other BHA
9. Damage locations?
But that’s not all the information that is
there.
www.GEKEngineering.com
2
Header Information
WELL TYPE: OIL PRODUCER
FIFST COMPLETED: 22/12/96
WORKOVER DATE: MAY 2001
WORKOVER NO: 1
ANN. FLUID: CaCl2 BRINE
FLUID WT: 1.17 SG
RTE: 29m
SWAB:
KOP: 2290M
HUD:
DEPTH UNITS: METRES
REF. LOG: XXXXX
MAX DOGLEG: 6.184 deg @ 1725m
MAX DEVIATION: 89 deg @ 4456M
AV. ANGLE THRU PAY: 88 deg.
MINIMUM I.D.: 4.060 @ LTV
www.GEKEngineering.com
3
Some points of interest:
Profile locations
Trapped annuli
Restrictions
SSSV
Gas lift valves
Ledges/shoulders
Crossovers
EOT (end of tubing)
PBTD, plugs of any type
Kick-off points
Fluid entry areas
Fish
Damage
Debris
Doglegs
www.GEKEngineering.com
4
Components – size, grade, id, position
www.GEKEngineering.com
5
www.GEKEngineering.com
6
Mixed equipment
• What is the pressure rating of this well?
Sometimes components are mixed in a well, often with the aid of crossover pieces to
adapt fittings of different pressure ratings. The pressure rating is set by the current
strength of the lowest strength piece. Actual testing is required to determine the level of
working pressure. When damage is known to have occurred, the components must be
tested, isolated or replaced.
www.GEKEngineering.com
7
Flanges
Nominal
Size of
Flange
Casing Size
Diameter of
Flange
Diameter of
Bolt
Circle
Number of
Bolts
Ring Type
2-1/16
2-3/8
8-1/2
5-1/2
8
R-24
2-9/16
2-7/8
9-5/8
7-1/2
8
R-27
3-1/8
3-1/2
11
8-1/2
8
R-37
4-1/16
4-1/2
12-1/4
9-1/2
8
R-38
5-1/8
5-1/2
14-3/4
11-1/2
8
R-44
7-1/16
7
15-1/2
12-1/2
12
R-46
11
9-5/8
23
19
12
R-54
13-5/8
16
30-3/8
26-5/8
16
BX-160
www.GEKEngineering.com
5000 psi, Type 6B
8
Valves
Above and Below: Gate valve
seals and bar – common in
wellheads.
Right top: plug
valve – common
in surface
treating “iron”
Right center:
dowhole flapper
valve.
Right lower:
butterfly valve
common on
tanks.
Note: open a valve fully (count
the turns) and close it fully (also
www.GEKEngineering.com
count
turns) – throttling flow with
a valve will lead to erosion.
9
Profiles
www.GEKEngineering.com
10
Pay Interval Schematic
1. Where are the fluid entry points
1. From the wellbore
2. From the reservoir.
2. Will the interval between the sceens pack
during gravel packing?
3. Will ECP’s inflate? How long is the slide?
How rough? What deviation? What fluid is
use to inflate? What is the stability and
permeability of the set point?
www.GEKEngineering.com
11
Limited Schematics
Artists renditions – too much missing.
Problems in a deviated well arise around kickoff points (window
debris, sharp edges, doglegs), build angle, junction isolation quality
and changes in angle along the horizontal plane.
www.GEKEngineering.com
12
Detailed information drawing.
Potential Problems:
Open shoe at 16”x20”
“C” annulus.
Trapped or sealed
annuli on A and B.
Fill tag at 12,845’
Tubing cut at 12,933’
www.GEKEngineering.com
13
Completions Section – What are
the clearances, hot spots, entries, etc.
www.GEKEngineering.com
14
What is below the current
completion may influence
what can be done in a
workover.
Plug quality
Leak potential from high
pressure gas or water
zones.
Corrosion potential of lower
zones
www.GEKEngineering.com
15
Upper section of a dual, note packer,
15a
15
15a
www.GEKEngineering.com
16
Bottom zone of a dual completion with sand control. Note clearances, screen location with respect
to pay, isolation potential, method of stacking the completion, and opportunities for problems.
www.GEKEngineering.com
17
Another style of well bore
schematic.
Note that the level of detail is
different – not as much
information on the individual
jewelry.
Note that the I-1 upper
completions is a sand control
completion with the long
string passing through a
screen. This needs a blast
joint to protect against long
string leaks and failure.
Good isolation in most cases.
The I-5 Sand is a nonperforated future alternative
pay. In this configuration,
how could it be completed?
Note how the completion is
separated, allowing packing
of the L-4 and then building
the upper completions.
www.GEKEngineering.com
18
Gas Lift Valve Locations:
Depth
Size?
Dummied or Active?
Condition?
www.GEKEngineering.com
19
Red Flags - Restrictions
• In the design/drill
–
–
–
–
–
–
Profiles
Some connections
Crossovers
SSSV’s
Doglegs
Deviated sections
• Production
–
–
–
–
–
–
Scale
Organic ppts.
Salt
Tubular deformation
Fish
Fill
www.GEKEngineering.com
20
Workover Concerns
• Tubing end – entry of tool strings
• Latching plugs and fish
– Deviated set points
– Fill
•
•
•
•
•
Swell of elastomers on plugs
Swell and bow in fired perforating guns
Overlap sections for perforating
Liner tops (leaks)
How to circulate out the back side.
www.GEKEngineering.com
21
Common Mistakes and Errors
• Schematic not current:
–
–
–
–
Last redesign, workover, failure not listed.
Corrosion, fill, collapses, or fish not listed.
Does pipe/wellhead need to be derated?
Deviation shortens tool length that will run through the
bend.
• So, how do you know what’s there?
– Drift / tag, bailer, dummy tool runs, impression blocks,
camera…
– Talk to the field and last engineer who had the well.
www.GEKEngineering.com
22