7 Intervention Decisions

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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

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