Operational conditions

What are operational conditions

Operational conditions include environmental conditions and physical loads as experienced by the equipment during all lifecycle phases. Functional failures with or without failure mechanisms can only be predicted and prevented if the operational conditions are known and understood prior to the design phase and if materials and geometry is selected during the design phase to resist these conditions. Operational conditions should thus be described in the product- and environmental requirement specification worked out prior to the design phase. The time will also play an important part with regard to the development and escalation of failure mechanisms as most of these are time dependent. Thus, required lifetime should also be described in the product requirement specification.

Environmental conditions

Environmental conditions can be categorised as:

• Contamination
• Deposits
• Medium
• Pressure
• Radiation
• Temperature

The site map function can be used to show all subcategories and datasheets simultaneously.

Physical loads

Physical loads can be categorised as:

• Tensile force (static, dynamic, impact)
• Compression (static, dynamic, impact)
• Bending (static, dynamic, impact)
• Torsion (static, dynamic, impact)
• Movement (axial, rotation, vibration)

Environmental conditions like pressure and temperature make physical loads in addition to external loads.

Lifecycle

Operational conditions will vary during the entire product lifecycle, including manufacturing, assembling, testing, storage, transportation, operation and maintenance. A common fault is to study operational conditions only when the tool is in the well. Important conditions can then be forgotten, like sunlight on rubber during storing or the rough handling during transportation and operation.

Scenarios

Operational conditions are often specified as single loads only in the product- and environmental requirement specification. This is insufficient. Well equipment will be exposed to different scenarios (load cases) during its lifetime. A scenario describes an event and how operational conditions are combined and changed as a function of time during the event. Worst case scenarios and not the single or individual operational loads are normally dimensional for the well equipment. Typical scenario categories are:

• Flowing mediums (like production, injection and pump in-jobs)
• Static mediums (like well shut-in)
• External loads (like the drill string- and tubing on casing and run-through intervention equipment)
• Internal loads (like the force on the valve seat from the valve actuator)
• Human activities (like making scratches during assembling, transport, installation and maintenance)
• Meteorological problems (like avalanche, heavy snow, high wind speeds and lightning)
• Geological problems (like earthquake, landslide, subsidence)
• Cosmic problems (like falling meteorites, falling space ship, satellite, scrape, etc)

Not all the above categories are specified for well equipment for natural reasons. Specific scenarios for completion string and drilling equipment are:

• Completion string scenarios
• Drilling scenarios

Different type of wells will have different scenarios that are critical or typical worst case scenarios. Completion engineers are responsible to have all relevant production scenarios evaluated in the tubing stress analysis executed during the completion design phase. The completion string loads from the tubing stress analysis should also be given to the team responsible for completion string components like the downhole safety valve (DHSV) and the production packer, to include these as performance requirements in the product requirement specification.

A separate analysis of assumed operational conditions could be performed in addition to risk analyses like the FMECA and the OPERA This will only be required if the product- and environmental requirement specification is inadequate. It could also be wise in other cases like investigations.