Challenges in Offshore Platform Re-Vamp Projects Execution
Shiju Varghese, Engineering Manager Piping, Aker Solutions

Majority of Oil and Gas production around the world are from matured fields which are in the process of depletion. Compared to ongoing Greenfield projects, revamp of existing facilities are more in numbers. Economic situations force the operators to exploit the possibilities of oil and gas recovery beyond the designed life. The article details the challenges encountered in the successful execution of Offshore Platform re-vamp projects.

The platforms which undergo re-vamps are generally 20-25 years or older. A fundamental differentiator with brown field projects, irrespective of the extent of modifications, retrofits and upgrades, is the interdependencies, while combining the existing facility and the new/modified facility in mechanical and process terms. More challenges are encountered in conversions from MODU (Mobile Offshore Drilling units) to MOPU (Mobile Offshore Production Units), Water injection platforms to Production platforms etc, where space and weight shall be limited to that of existing facility. Wherever required, a study of any additional safety requirements shall be performed to ensure safety of new facility.

Revamp projects will have a very ambitious execution schedule to minimise the disruption of ongoing operation and accommodate within the weather window. The shutdowns are generally planned phase-wise so that the operation is not completely halted. Safety consideration in design as well as execution shall be given high importance in revamp projects. Interface with operations staff to take care of the operations requirements is an essential component for the customer satisfaction. Work-scope at offshore, which involves high risk as well as cost, shall be reduced by eliminating inaccuracies in design. There are various stages for these kinds of projects where care can be taken to ensure successful completion of the project within the stipulated time frame.

Generally a pre-bid survey is conducted which gives a fair idea about the status of the platform and the critical issues which can arise during detail engineering. This survey helps the bidders to assess the prevailing conditions and factor-in, while bidding.

Pre-engineering survey plays the most important role in the successful execution of the project. A proper analysis of data required for engineering versus data available is an important pre-requisite so that the survey can be focused towards collection of unavailable data. Such surveys are conducted by experts from each discipline who can take any critical decisions regarding design and will ensure that all the important information is gathered from platform during the survey.

Pre- engineering sur vey mainly comprises of structural assessments for any extensions of platform or installation of new equipment, feasibility of accommodating the changes envisaged during revamp, and existing data collection. Acquisition of existing data or drawings of old platforms is always a challenge. If the drawings or documents, of the existing platform are not available, it shall be ensured that all the minute information is gathered during the survey. Although, in some cases, the existing documents and drawings are available; those may not be updated to the extent of changes that happened during the life of the platform.

Accurate and faster acquisition of data is very important to ensure that the long delivery items are ordered in time. Error prone manual surveys can be replaced with 3D laser surveys to fetch accurate data which is very useful in getting information at inaccessible locations. This can also plug the gaps of inaccuracies in as-built drawings. 3D laser survey can be used as an input for constructing a 3D model. 3D laser survey data can also be converted to an intelligent model.

Pre-construction survey shall be conducted prior to the initiation of construction on the platform. This shall ideally be after the preparation of all the critical construction drawings. The intention of this survey is the physical verification of the construction drawings with respect to the existing facility. The dimensions and locations of structural extensions, locations of existing equipment versus the new equipment, which is going to be placed at the same location, tie-in points of pipes from where the lines are extended or tapped are some of the important check points during this survey. This is an opportunity for capturing any change, which may also require additional material procurement.

Accurate estimate of material like steel, pipe, valves and fittings, cables etc for construction plays a very major role in the success of such projects which have a stiff execution schedule. Non-availability of any small item which is noticed at the fag end of the construction phase will jeopardise the execution plan. Such situation can only be managed by air-lifting of the items which have fallen short, which is an expensive proposition. Estimation of construction material and placement of order shall be closely monitored to avoid any last minute rush.

Constructability study shall be carried out to have a smooth phase of construction. Methodology of dismantling of existing equipment as well as installation of new equipment shall be studied in detail. The challenge is to arrive at a feasible option which will not damage the existing equipment as well as the new equipment with the limited space available. This study will help in deciding the requirements of any additional structural extensions or mechanical handling facilities. There are instances where pipes, cable trays etc. which are not part of the revamp are affected, as they require to be dismantled to facilitate removal of existing equipment and installing the new. This forms an additional scope of work and shall be captured during this study. An initial study using 3D model prior to the survey is always advantageous.

Incase of replacement of equipment, care should be taken to ensure that the new equipment, that is installed in the existing location should match or be within the foot-print and weight of the existing equipment. This is important to maintain the existing work area around the equipment as well as the tie-in points should be same as existing. If the load of new equipment is exceeding the existing equipment, structural feasibility shall be analyzed critically. A study of methodology of new equipment installation shall be carried out to ensure that any offshore surprises are avoided.

Judicious planning and logistics management of accommodation barges, barges for transporting equipment and other materials will help timely completion of project and curb the expenses.

In re-vamp projects of offshore platforms all the tasks fall in critical path. Meticulous planning, feasibility studies, faster placement of orders, accuracy in design and quantification of material are the major contributors for the success of offshore platforms re-vamp projects.