Trash or Treasure? Considerations for Future Ecological Research to Inform Oil and Gas Decommissioning

Abstract

Numerous oil and gas (O&G) installations worldwide will need to be decommissioned in the near future. Complete removal of subsea structures is often the default approach although some regions retain structures under rigs-to-reefs programs. Here, we reviewed the published literature to understand the status of global research on decommissioning, and specifically identify gaps in ecological knowledge. We estimated the frequency of different research categories (i.e., themes, and spatial/temporal scales), and tested the assumption that the number of papers across the categories of each research aspect was even in distribution. However, the frequency of studies focusing on biodiversity at a local (≤100 km2) scale (relative to regional and oceanic and pan-oceanic scales) were significantly higher; while other theme categories (e.g., eco-toxicology, connectivity, structural-integrity, restoration and other) were significantly lower than expected. Temporally, ≤1-year studies were more frequent than multi-year studies, but these frequencies did not significantly deviate from the assumed distribution of equal frequencies. We propose that further research be carried out to evaluate the benefits of both retention and removal of structures. Ecological research on decommissioning should extend its focus beyond biodiversity, to include eco-toxicology, structural-integrity, connectivity at larger spatial and temporal scales. This would provide a more holistic assessment of ecological impacts to inform sustainable and equitable development choices in multiple Blue Economy sectors, as we transition from offshore O&G to marine renewables.

Influence of offshore oil and gas structures on seascape ecological connectivity

“…Limited information exists on genetic connectivity associated with O&G infrastructure (Schläppy et al, 2021; Data S1). The few published studies highlight the value of genetic data for characterising the nature and frequency of dispersal between natural and artificial habitats.…”

“…This situation has arisen largely from challenges involved with in situ investigations of operating infrastructure in a dynamic offshore environment. Additional knowledge gaps have resulted from a historical focus on community composition, faunal biomass and productivity of ecosystems associated with marine infrastructure (Schläppy et al, 2021), that is, on structural rather than functional aspects of marine ecology. The current study highlights the substantial nature and broad scale of connectivity impacts potentially arising during installation and decommissioning of O&G structures.…”

“…This breadth of effects on marine life shows that decommissioning issues are complex and depend on multiple, and often site‐specific, contextual factors (Birchenough & Degraer, 2020; Fowler et al, 2018; Macreadie et al, 2011; Smyth et al, 2015), which may be better understood by considering O&G structures as components of a larger system. For example, a recent review of decommissioning research found a relatively small proportion of studies focussed on biodiversity and connectivity (Schläppy et al, 2021).…”

“…As such, we review the relevant literature to understand the degree to which O&G structures are interconnected with natural facets of the seascape to facilitate/impede movements of organisms and other ecological processes. Given the paucity of research on this topic (see also Schläppy et al, 2021), we structured the review around core areas of decommissioning decision making and research focus thus far—fish and megafauna (given many of these are either threatened and/or commercially important), larval and invasive species dispersal, and gene flow. Within these areas, we discuss both functional (movement of individuals) and structural (the physical arrangement of habitat) connectivity in published research.…”

Decommissioning Research Needs for Offshore Oil and Gas Infrastructure in Australia

“…Generally, the factors that influence these costs and benefits are considered to be: (i) the creation of habitat for managed or valued species, as well as the potential risk of oil and gas infrastructure aiding the spread of invasive species; (ii) the potential for impacts of legacy contaminants associated with either drilling or oil and gas production; and (iii) potential socioeconomic concerns relevant to stakeholders needs (including social acceptability of different decommissioning options). These factors are likely to influence each other (Figure 2; Schläppy et al, 2021) and should not be considered in isolation. In the sections below, we describe the lessons learned from the international literature for each of these factors, and also describe the circumstances that are unique to the Australian context.…”