An Investigation of Different Approaches for Probabilistic Cost and Time Estimation of Rigless P&A in Subsea Multi-Well Campaign

Abstract

High demand for plug and abandonment (P&A) of subsea wells in the forthcoming years on Norwegian Continental Shelf, low availability and high daily rate of semisubmersible rigs as well as high proportion of P&A cost to total cost of drilling exploration wells challenge industry and intensify looking for alternatives and rigless technologies which can make P&A operation more cost effective and release time of semisubmersible rig earlier. Light well intervention vessels currently can take over some parts of P&A operation and release time of semisubmersible rigs in order to function in drilling and completing of new wells. In addition these vessels have a low daily rate compared to semisubmersible rigs and decrease cost associated with P&A. A systematic yet simple approach is required to acquire a correct picture for expenditure and time of these alternative technologies. In this paper, potentials and experiences of light well intervention vessels for P&A and benefits associated with them will be discussed. An example case is considered wherein a new technology is deployed from a light well intervention vessel to set surface plugs in a multi-well campaign. Thereafter, benefits associated with application of this rigless technology are discussed and highlighted. The paper will discuss different approaches for structuring probabilistic time and cost estimation of multi-well P&A campaigns discussing at which level these should be performed and what is the most appropriate approach with respect to modularity and efficiency. This will also be seen in relation to the Oil and Gas UK cost estimation guideline for P&A and the NORSOK technical specification. The objective is to keep the simulations simple while still acquiring the correct range of time and cost for multi-well P&A operation in order to make the proposed approach applicable for the industry.

Vehicle routing with endogenous learning: Application to offshore plug and abandonment campaign planning

“…When plugging a well permanently, several operations have to be performed. Based on the work by Oil & Gas UK (2015) and Moeinikia et al (2014a), these operations can be divided into four phases. Phase 0 ("preparatory work") includes pre-P&A work such as stopping the flow from the well, logging the tubing quality and establishing temporary barriers.…”

Essential Aspects in Probabilistic Cost and Duration Forecasting for Subsea Multi-well Abandonment: Simplicity, Industrial Applicability and Accuracy

“…Moreover it helps to reflect application of different vessel technologies to accomplish different phases. In a previous study (Moeinikia et al 2014), it has been discussed to add one additional phase -Phase 0 -to Oil and Gas UK Guideline phase categorization reflecting preparatory work for Phase I. The reason is that it is seen that light well intervention vessel can be applied to perform preparatory work for Phase I although the main work for Phase I requires the application of a rig (Statoil 2012).…”