Updates on offshore drilling activity may trigger expectations of new oil discoveries, but in practice, each well serves a different purpose, and not all lead to commercial production.
In Guyana’s Stabroek Block, where ExxonMobil and its co-venturers continue an active drilling campaign, wells are typically classified into three categories: exploration, appraisal and development. Each plays a distinct role in moving a resource from discovery to production.
Exploration wells are the first step. These are drilled to test whether oil or gas is present in an area. While Guyana has seen a high success rate since the Liza discovery in 2015, not every exploration well results in a find. Even when hydrocarbons are encountered, they may not be in quantities or conditions suitable for commercial extraction. An example of such a well is Goatfish-1, for which drilling is ongoing.
If oil is found, companies may move to appraisal drilling. These wells are used to define the discovery, in terms of metrics like size and quality. Multiple appraisal wells may be required to determine whether a discovery can support a development. At this stage, companies are not adding new discoveries, but refining their understanding of existing ones. For example, ExxonMobil appraised the Barreleye discovery earlier this year.
Development wells come later, once a project has been approved. For example, development drilling for the Hammerhead project is ongoing. These wells are drilled for the purpose of oil extraction and are tied to production infrastructure such as floating production, storage and offloading vessels (FPSOs). Unlike exploration and appraisal wells, development wells do not test for new resources; they produce from known reserves.
The distinction is important because routine updates on drilling activity can refer to any of these stages. A rig moving between prospects, or a new well being spudded, does not necessarily signal a new discovery. In many cases, it reflects ongoing appraisal work or preparations for production.
Timelines also vary significantly. A discovery can take several years to move from exploration to first oil, depending on the complexity of the reservoir, government approvals and the scale of investment required. Guyana’s rapid development pace has shortened this cycle compared to many other jurisdictions, but it still involves multiple phases before oil is brought to market.
For observers tracking Guyana’s oil sector, understanding the type of drilling underway is key to interpreting what each update means. Not every well adds to the country’s resource base, but every well serves a critical purpose.
