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Research that compared rehabilitating an existing pipeline with replacing it with new line has been conducted by Abu Dhabi National Oil Co.
In addition to obvious capital costs of rehabilitation vs. new construction, the company found that such a comparison must also quantify hidden costs of using older pipelines, primarily costs due to higher leak risk, extra inspection, and higher maintenance.
Among other results, the study found the following: Before rehabilitation of a pipeline, its condition must be assessed by intelligent pigging, cathodic-protection surveys, and coating surveys.
Pipeline rehabilitation is normally more cost-effective than replacement if most of the work consists of recoating.
For recoating costs of more than $200,000/km, it is probably not worth rehabilitating typical pipelines smaller than 18-in. OD if more than 70% of the pipeline length requires recoating.
If safety concerns require pipeline shutdown for rehabilitation, the resulting production losses, if crudetransfer rates are high, will often make this approach uneconomic.
Two studies
Pipeline rehabilitation is carried out to increase pipeline lifetimes or revitalize redundant lines for alternative service.
Different techniques are used for rehabilitating internal and external deterioration. External coating breakdown and corrosion are very common with land-based pipelines and are generally solved by in situ recoating.
On the other hand, internal corrosion is somewhat more difficult to deal with and may require cutting out and replacing entire sections of pipeline. Other methods of internal rehabilitation include pulled liners and epoxy flood coating.
Because some of these other methods for dealing with internal corrosion are addressed elsewhere, only external rehabilitation will be dealt with here.
Two case studies are used to illustrate the factors involved, including a quantitative assessment of leak risks under required service conditions.
The cost effectiveness of rehabilitation compared to new construction will depend on several factors. These include length of pipeline requiring replacement, length of pipeline requiring recoating, rehabilitation coating specification, feasibility of carrying out rehabilitation on "live" lines, and production losses during rehabilitation.
In addition to the simple comparison of rehabilitation costs vs. new construction, hidden costs must also be taken into account. These include potential losses from the increased leak risk of older pipeline, shorter coating lifetimes of in situ coatings, and production losses if external rehabilitation cannot be done on in-service lines.
Each...