The Scientific or Technological Advance must be relative to the current Technological baseline within the oil and gas industry. Hence an eligible R&D project needs to be more than just applying Technology for which there is already a publicly available reference. Likewise, an Advance can't be a commercial, business or functional Advance. It is often the case that there is a Technological Advance behind the more functional concerns - but it is the 'Technological' details of the Advance that needs to be brought out to support an R&D Tax Credits Claim.
Many types of Oil &D Gas services project can potentially be includable for R&D tax credits, including:
the development of new subsea infrastructure
Jacket designs for challenging locations
the development of drilling technologies to operate in more extreme wells with higher temperature and pressure requirements
the appreciable improvement of the performance of equipment
the development of new knowledge regarding geological interpretations and reservoir models through seismic processing
As with all fields of Technology, the key point around the Technological Advance is that you must be (seeking) to move Technology forwards against the industry baseline of knowledge and capability. Essentially this means that the project can't purely be coping, or reusing information from the public domain - but instead it needs to be making a step forward.
Essentially the Technological Uncertainty would be where an Oil and Gas technical competent professional in the is uncertain about how to achieve a specific Technological solution.
The Uncertainty may arise if you are unsure whether it is feasible to achieve the Advance. This Uncertainty may be because of the challenges faced when having to design components to minimise mechanical stresses or some other 'Technological' reason!
Alternatively, the Uncertainty may come about, as of how to achieve the Advance in practice. It may be that there are multiple options and it is unclear which would be the best taking into account various conflicting requirements.
Furthermore, you may encounter systems Uncertainty, for example, if it is unclear what the effect of integrating different well known and understood technologies but in a non-standard way.