Increasing Mature Fields Reserves Using an Adapted Zero-Base Budgeting

Abstract

AbstractThe need to reduce costs, to increase the attractiveness of development projects in the mature fields environment is a necessary condition to allow the incorporation of new reserves and has led the oil industry to seek better practices in well construction. This paper presents the implementation of an adapted Zero-Base Budget (ZBB) methodology, which guided Petrobras to establish lean (but still viable) cost targets. This is one of the initiatives that constitutes Petrobras' RES20 Program, whose ambition is enabling 20 billion equivalent barrels of new reserves by the year 2030.Through a multidisciplinary effort, the ZBB identifies the lowest CAPEX well design, where some optimizations are considered, keeping the focus on safety.As an example of such new practices, we present in this paper one new design example applied to post-salt scenario, called TOT-3P. It is based on drilling the well in 3 sections and setting 2 casings, completing it by running in hole lower and upper completion together (TOT - True One Trip). The well design of 7-GLF-49H-ESS is a real example of this concept implementation, originally approved with an estimated average duration of 96.6 days. The original scope included drilling in 4 sections, with a pilot well and Open Hole Gravel Pack (OHGP) completion. Applying one of ZBB’s pillar, which considers the simplest feasible design, the well was built in 43.7 days, resulting in more than 50% time reduction. According to an external database, this duration is a "best in class", when compared to the industry, confirming the methodology potential to achieve the mature field’s economical requirements.Application of the proposed ZBB methodology in 19 fields of Petrobras’ portfolio, for pre-and post-salt scenarios, revealed a potential average reduction of 50% when compared to the field historical durations, considering all potential optimizations that could be implemented.Since the incorporation of the optimizations depends on the wells features, given that ZBB assumes some premises to adopt the lowest CAPEX design, a gap analysis becomes necessary in order to identify which optimizations can be incorporated. A list of 13 wells from 3 mature fields was analyzed, resulting in a maximum expected investment reduction of 29%.The potential cost reduction associated with well project ZBB optimization presents itself as a key enabler of mature fields re-development, that will allow for the incorporation of important volumes of reserves, increase the recovery factor in mature fields and reach the targets of the RES20 program.