ISO 19901-10:2021 Petroleum and natural gas industries — Specific requirements for offshore structures — Part 10: Marine geophysical investigations.
5 Objectives, planning, and quality management
5.1.1 Objectives and project specifications
The general objective of a marine geophysical investigation is to provide information about the seafloor and sub-seafloor that is relevant to the design, placement, installation, operation, assessment/reassessment, and decommissioning of offshore structures. This includes the assessment of geohazards over the lifetime of the development.
This document considers the upper portion of a hydrocarbon well as an offshore structure, and therefore covers the requirements for characterising ground conditions and identifying geohazards that can be encountered by the drilling operation and the installation, use and decommissioning of wells. The depth of interest for a marine geophysical investigation for a hydrocarbon well is typically (as appropriate)
— in the case of a targeted hydrocarbon reservoir shallower than 1 000 m below the seafloor, to a depth just above the reservoir, or
— for deeper reservoirs, at least 200 m below the preferred setting depth of the first pressure- containment casing string or 1 000 m below the seafloor, whatever is greater.
Marine geophysical investigations for pre-drilling well-sites focus on possible gas in the sub-seafloor overlying the reservoir that can pose a threat to the drilling operation. The investigations described here are not concerned with the reservoir that is targeted by the drilling operation.
Where relevant, project specifications should refer to methods described in this document, Any references to methods should be accompanied by method-specific information, as applicable. If method-specific information is contained neither in the project specification nor in this document, then contractor’s practice applies. For some parts of a project specification, it can be necessary to provide preliminary specifications that require subsequent revision. An example is on-site revision of operational parameter values for data collection equipment, so that the actual site conditions can be taken into account and accommodated in order to achieve optimum performance.
With seafloor and sub-seafloor conditions having significant impacts on offshore structures, the following partial list of features can be of interest:
— human-made structure and debris, including existing infrastructure (e.g. platforms, cables, sub-sea infrastructure, etc.), archaeological features and unexploded ordnance;
— difficult soil conditions (e.g. very weak soils, boulders, permafrost);
— rugged or steep topography (e.g. escarpments, scarps, gullies
— buried channels;
— seafloor or sub-seafloor instabilities or evidence thereof (e.g. mass transport deposits);
— faults;ISO 19901-10 pdf download.