The main purpose of the presentation will be to illustrate by example how the effectiveness of the Pipeline Inspection exercise is influenced by the selection of the correct method and a clear understanding of the objectives of the inspection activity. The Operators' objective of satisfying the Inspection requirement as cost effectively as possible is very clear The presentation will not seek to explain methods in detail or to offer a critique of the different methods of pipeline inspection
There are now over 4,000 km of subsea pipeline in the UK sector of the North Sea BP currently operates around 25% of the total length of subsea pipeline in this sector Many of these pipelines handle production from a number of Platforms (eg Forties MOL takes production from 11 different platforms) The consequence of £allure of these pipelines is potentially enormous in commercial terms, environmental terms and safety terms. We are now also approaching an era where some of the pipelines are approaching their design life The pipeline infrastructure is an enormous asset which needs to be preserved.
Whatever inspection activities are to be undertaken whether onshore, offshore or subsea it is Important to retain a clear sight of the objectives and the mechanisms of failure which are being investigated. Most if not all inspection techniques have limitations of the technique which need to be understood Subsea inspection activities are no different from topsides inspection. In these respects The fundamental differences are in the relative costs of the activities and the difficulty/cost of a repeat inspection In the subsea activity
The statutory inspection requirements for pipeline inspection are stated In SI1513. Different operators place different interpretations on how these requirements may be met by differing application of the available methods. This difference in application not only reflects the differing inspection requirements for each pipeline but the apparent subtle differences In inspection philosophy between the operators. It is arguable whether the satisfaction of these SI1513 requirements alone will guarantee the operator's primary objective of preservation of the integrity of his pipeline and the maintenance of production
The inspection methods available vary widely to the extent that they do not bear direct comparison They fall in to the two categories of techniques applied from the outside and techniques applied from the inside of the pipeline In general terms their effectiveness is limited to viewingthose mechanisms acting from the inside and outside respectively This last statement is contentious but certainly £allure mechanisms are more easily investigated from the side of the pipeline at which they act.
The internal deterioration of pipelines is generally an age related phenomenon and the requirement to investigate internal corrosion is increasing with the age of pipelines and the producing fields Changes In produced fluids may Impact on pipeline internal corrosion rates