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Well Intervention Methods
Choosing a method of intervention Workovers Conventional Rig Through Tubing Well Intervention Coiled Tubing Hydraulic Workover Unit Wireline/Slickline Production Logging Multipurpose Service Vessels Best Practices
But how do we decide to intervene and how can we improve the decision making?
WELL INTERVENTION PRODUCTIVITY SCHOOL
Well Intervention decisions.
First – Do you really need to intervene. If you do then……… How do you choose the best method of intervention. Factors to help you decide. – – – – – –
Cost. Complexity. Risk. Reliability Equipment availability. Logistics.
WELL INTERVENTION PRODUCTIVITY SCHOOL
Forties Interventions
45 Scale mill N2 lift Sand cleanout
40
Squeeze Gas lift Perforation Plug
35
30
Patch ESP Pump installed Scab casing Workover
25 20
15
10
5
0 76
77
78
79
80
81
82
83
84
85
86
87
Date
88
89
90
WELL INTERVENTION PRODUCTIVITY SCHOOL
91
92
93
94
95
96
97
Why Intervene?
Amount of downtime can be significant $ $ $ $ 6%
4%
3%
COMP. FAIL. SAND
3% 1%
15%
7%
GENERAL 13%
SCALE INHIB. SCALE REM. ESP
7% 12%
8% 10%
11%
SSSV FAIL. FLOWLINE etc.
TOTAL LOSS (mbd) = 28.403 (JAN-JUN, 181 DAYS)
RES. SURV.
TOTAL WELL LOSSES = 5,141,007 bbls.
WHD/H. LIFT ADD VALUE
BP Production Well Losses (bbls) Virtually all these “losses” have to be fixed by interventions - or are caused by interventions themselves! WELL INTERVENTION PRODUCTIVITY SCHOOL
GAS LIFT WELL INT. SURV.
BP ‘WETS Wellwork evaluation tool.
WETS – Excel base software. – Download from BP Inranet.
WELL INTERVENTION PRODUCTIVITY SCHOOL
Scorpion Plots
16000 14000 NRWO RWO HCL Frac Perf
12000 10000 8000 6000 4000 2000 0 0
2000
4000
6000
8000
10000
12000
WETS Cumulative Barrels (mbo)
WELL INTERVENTION PRODUCTIVITY SCHOOL
14000
16000
18000
20000
Wellwork - a definition
There is now a definition of "wellwork", for the purposes of tracking, as agreed by the Wells Leadership Team (WLT, formerly known as the Well Performance Steering Board).
Wellwork is: Well Interventions •Rate adding operations (e.g. stimulations and re-completions) •Rate restoring activities (e.g. tubing repairs and scale mill-outs) Well Optimisation Activities •Lift optimisation and gas well de-liquification •Sand management eg. sand detectors •Water injection optimisation Both capex and opex activities are included. Wellwork is not: •Drilling rock (e.g. sidetracks/TTRD/CTD) •Preventative maintenance (e.g. scale inhibitor squeezes) •Activity associated with the initial completion of a well as agreed by the WLT, 7th November 2000
WELL INTERVENTION PRODUCTIVITY SCHOOL
Choosing a Method of Intervention
Before jumping to the obvious solution - “use a rig” - perform a cost vs benefit risk analysis Management of Risk – ‘Good Decisions’ vs ‘Best Decisions’ – How do you decide what to do with the well; and if there are several wells, how do you prioritise? – Make sure that you fully understand why a well is underperforming. – Workovers need to be justified either from a safety point-of-view or on economic merits. – If you have a large portfolio of wells, perhaps it is worthwhile developing a more formal approach to job selection and ranking. – Risk must be accounted for. The success rates of well interventions are often seriously overestimated.
Historic Well Work Uncertainty based Onshore US Well Work
Total Success Rate
Reservoir Mech/Ops Success Success Rate Rate
# Jobs
Acid Fill Cleanouts Frac GSO WSO Mech Add Perf RWO
0.71 0.47 0.84 0.58 0.50 0.70 0.62 0.82
0.94 0.7 0.82 0.92 0.65 -
49 15 32 79 20 20 147 11
0.9 0.82 0.61 0.76 0.95 -
Success Rate = Reservoir Success Rate * Mech/Ops Success The previous chapter has tried to explain most of the well management issues, and the techniques to improve well productivity. This chapter tries to explain their implementation.
WELL INTERVENTION PRODUCTIVITY SCHOOL
Value of Data for Intervention Decisions
Example
Blowdown
Analogues (Well Tests) Res Press (pbu/pfo) PLT RST
9 9 9
Well Decline
9 9
9
9 9 9
9 9 9
OH Logs Core SW SOR Subsea Samples Allocation Reliable Prod/Inj Data Fluid Image Seismic DH Gauges Cont Res Press Tracers
Infill
9 9
9 9
Depletion Slugging
9 9 9
Scale
Well Integrity
9
9
9 9 9 9 9
9 9
9 9 9
9 9
Corrosion Mon Annulus Mon
9 9 9
9 9 9 9
Red - data is not required to influence control
9
Yellow - data could have some impact on control but will require justification
Marcit Gel Trial PVT REL Perms PH Meter Slug Catcher Samples
9 9 9
= ‘No Brainer’
9
9 9
WELL INTERVENTION PRODUCTIVITY SCHOOL
Green - essential data to help exercise improved control on the issue
Do we intervene?
Safety or Economic? Cost vs. Benefit
Metrics
– Risked cost - probability of success – What are possible outcomes? • Success • Failure – No worse than before – Worse than before • Trainwreck – Benefit • Incremental oil (new reserves) – e.g. re-perforate • Accelerated Oil – Stimulation? • Timeframe
– EMV / NPC • (Expected Value / net present cost) • Quantifying added value can be difficult – i.e. data gathering.. – $/bbl – Payback – IRR • (rate of return)
or gut feel?
WELL INTERVENTION PRODUCTIVITY SCHOOL