The Completion Life Cycle and Basis of Design
How a completion basis of design is built, which life-cycle cases it must cover, and how to defend it when reservoir and cost pressures pull in different directions.
13 min
Activities: 0 of 2
A design for the whole life, not the first day
This course is for completion, production and well intervention engineers, and for supervisors who must judge and defend completion and workover decisions. It assumes you know the basic equipment. It asks you to design, to judge between options and to handle the cases the textbook does not cover.
A completion is installed once and must work for the whole producing life of the well, which can be twenty or thirty years. Its basis of design is the document that records every assumption: reservoir pressure and its decline, fluid composition, rates, temperatures, contaminants, lift method, intervention method and abandonment. Every equipment choice traces back to it. If an assumption is not written down, nobody can check it when conditions change.
Life-cycle load cases the design must cover
- 1
Install
Running and setting
Running loads, packer setting, pressure tests and displacement to completion fluid. - 2
Start-up
Clean-up and initial flow
Underbalance, high drawdown, fast heating of the tubing and annulus. - 3
Production
Plateau and decline
High rates, then falling pressure and rising water. Lift may be added. - 4
Shut-in
Cooling and full pressure
The tubing sees full shut-in pressure while cold. Gas wells reach their highest surface pressure. - 5
Intervention
Stimulation and kill
Acid or fracturing pressures, cold fluid injection, kill operations. - 6
End of life
Abandonment
Can the completion be pulled or cut? Can cement reach where it must?
Who owns which input
The reservoir engineer provides pressure, rate and fluid forecasts. The production technologist provides lift, flow assurance and sand predictions. The drilling engineer provides the casing design and wellbore shape. The completion engineer combines them into a design and checks that every life-cycle case is safe. Problems start when one discipline treats another’s number as fixed and certain. A forecast is a range. A good basis of design states a base case and the limits of the range, and checks the design against both.
Where designers disagree, and how to defend a choice
Build a basis of design
Order the steps a completion engineer follows.
- 1Record assumptions and review them when the plan changes
- 2Select the completion architecture and intervention philosophy
- 3Size and check equipment against every load case
- 4Collect reservoir, fluid, rate and pressure forecasts with ranges
- 5Define the life-cycle load cases, including late life and abandonment
Defending the design