Experts lay down golden rules for cost-effective P&A

A series of seven round table discussions allowed senior managers from super-majors, tier 1 contractors and independent operators, to set out best principles in well plugging and abandonment campaigns and how these should be improved in the next five years.

The gathering, which included experts from Royal Dutch Shell, BP and Total, was held behind the scenes at DecomWorld’s Well Integrity and Abandonment Conference, held in Aberdeen on June 30-July 1.

The participants considered the principal questions that an operator and its contractors face when dealing with a field in its end-of-life phase.

The main issue is how to make sure that, once begun, the P&A process can be carried out as safely and cost-effectively as possible.

Other questions concern the role of industry-wide co-operation, the evolution of technology and regulation, and establishing the permanence of the barrier in the wellbore – if the operator has to come back to the well a second time, costs are typically an order of magnitude greater than they were the first.

Detailed planning

The main factor when preparing a P&A campaign is to already have a plan in place well before the decision on decommissioning arises.

The ideal situation, according to the operators, is to begin preliminary work during the front-end engineering design phase.

It is common industry practice to have a 10-year plan in place for any given field, updated on an annual basis.

This includes production forecasts and capital expenditure allocation, and should also include P&A scheduling, with cost estimates based on data collected while they are still producing.

One use for the data is to group wells depending on how complex the plugging process is likely to be. The analysis should be more fine-grained than the standard attribution of classes I-IV; these should then be the basis of decisions as to many resources to mobilise, and how they should be deployed in the field.

For example, information about reservoir pressure should be used to order equipment with the appropriate performance specifications: as was pointed out, there is no need to pay for a 15,000 psi-rated blow-out preventer if a 500 psi unit would be safe.

Another use for the data collected during production is to create a map of what is not known, and use it as the basis for contingency planning.

Better together

The issue of co-operation is a much debated topic in the oil industry at present, and it takes a number of possible forms.

The participants in the discussion agreed that initiatives such as a P&A performance database should be compiled in order to benchmark performance and create a methodology for measuring improvements.

Companies should also contribute to a common store of “lessons learned”, which would over time grow to form a kind of reference library where engineers could look for insights when tackling problems.

One specific proposal was that the regulator could be offered the job of documenting P&A information as applications were submitted, so a knowledge base could be gradually built.

Companies in the oil and gas industry traditionally play their cards close to their chests, and so have to overcome certain cultural inhibitions before sharing information and resources with competitors.

However, it was generally agreed that co-operation in operational matters would naturally tend to reduce the costs of all participants, if only because of greater economies of scale and the reduced proportion of costs taken by mobilising and de-mobilising equipment and teams and more rational rig allocation.

The participants pointed out that different kinds of wells required specific sets of equipment, so it made sense to group them into multi-field campaigns for simple, complex, subsea and platform versions.

In particular, subsea wells should be classified according to the “tooling” required, such as workover risers and tubing hanger retrieved tools, and then grouped into unitary campaigns.

They also argued that this picture relates to a particular level of technological capabilities. If more effective techniques were to be developed in the future, the case for co-operation may become even more convincing.

However, operators and contractors could improve their co-operation on technology development, particularly when it comes to cost sharing.

Seal quality

The round tables also discussed how it was possible to ensure the formation of a long-term barrier. The present practice is to conduct tests for pressure and weight, and to log the cement properties.

In an ideal world the P&A team would have access to physical models of the cement in situ, but at present the technology is not available to do that.

Nevertheless, there was a consensus that better results could be achieved if companies were to improve their cement modelling practices.

In particular, it was agreed that flow simulation, integrity verification and laboratory testing – an area where Shell has made progress in recent years – would contribute to the long-term qualification of barriers.

Finally, it was agreed that the regulatory landscape relating to physical barriers needs to be crystal clear so that teams had clearly defined goals to work towards.

Here, defined performance criteria are better than general guidelines, and the practice of Norway’s regulators was seen as best in class.