Researchers from the Fault Analysis Group at University College Dublin are analysing data from the best geological outcrops in the world and undertaking flow and mechanical modelling in a project that aims to improve the petroleum industry’s understanding of fault-related reservoir compartmentalisation.
The project, entitled “Quantitative parameterisation of fault zones in outcrop for inclusion in reservoir flow models”, or QUAFF, is being funded by eight operating companies. Aberdeen-based ITF (Industry Technology Facilitator) played a key role in securing the money.
Hydrocarbon reservoirs can be broadly divided into carbonate and clastic reservoirs. Whereas faults in carbonate reservoirs often act as conduits for fluid flow, in clastic reservoirs, which are composed of porous sedimentary host rocks, faults can restrict or prevent fluid flow resulting in reservoir compartmentalisation.
As seismic surveys do not generally detect the detailed structure of fault zones, identifying the presence of fault-related reservoir compartmentalisation and predicting the associated impact on fluid flow is a major challenge for the oil and gas industry.
There is, for example, an increasing recognition that faults become more influential later in the life of a reservoir but that early recognition of their likely behaviour is necessary for improving reservoir management decisions.
According to Professor John Walsh, of the Fault Analysis Group, the money that has been made available is enabling researchers to travel to the best geological outcrops of faults in the world, really examine and quantify details of their structure and related characteristics, and then consider the impact of these in-depth descriptions.
QUAFF will help define improved algorithms for fault-property modelling and will investigate the frequency, nature and origin of critical geometric complexities, in different circumstances, that is, for different deformation conditions, host rock rheology and depositional sequence.
Fieldwork will be complemented by flow modelling using techniques developed by the Dublin group and by numerical mechanical models generated using the newly developed “Discrete Element Method”, pioneered in structural geology by this team.
The technique is providing valuable insights into fault zone processes and may eventually provide a means of predicting important aspects of fault zone structure.
Walsh: “Recent developments have allowed many features of fault zones (such as fault property variations, displacement partitioning and normal drag) to be included in reservoir flow models and this has been extremely valuable in helping us to understand and model the subsurface structure of reservoirs.
“However, while previous outcrop studies have allowed the principal parameters and related uncertainties of fault-zone related characteristics to be broadly defined, they often only offer a qualitative or, at best, semi-quantitative means of populating flow models.
“Within QUAFF we aim to establish quantitative parameters for fault zone characteristics, which when combined with flow and mechanical modelling, will provide an improved basis for defining and modelling faults in reservoir models. This in turn should help companies to optimise their field development and production processes.”
Project results will be synthesised into a form that may be readily included in modelling workflows as well as in a more detailed on-line atlas/handbook documenting the structure of fault zones within siliciclastic (quartz or other silicate minerals) sequences and outlining procedures for decision-making on fault zone modelling issues.
Colin Sanderson, senior technology analyst at ITF, said the potential impact of this project was reflected by the strong interest from the Aberdeen organisation’s members in supporting it.
“The original scope required support from six companies, but it has now attracted support from eight companies which has allowed the project scope to be extended,” he said.
“One of the real challenges of this type of work is making it easy for people on the ground to make use of the results. The more that you can get this information into a format that can be practically applied, the better. The development of the atlas in this project is a really good example of that.”