Issued: September '95

Amerada Hess Ltd
Amoco UK Exploration Co
British Gas E&P Ltd
Exxon
Japan National Oil Corporation
Mobil North Sea Ltd
Shell UK Exploration &
Production
Total Oil Marine plc

Research Providers

University of Liverpool
University of Manchester
Heriot-Watt University

Project Monitoring

PSTI

Project Cost

£525,000 over 3 years

Participation

£75,000 per company over length of project. Additional participants welcome.

The Requirement

Faults and related diagenetic heterogeneities may have a significant effect on reservoir performance. Enhanced prediction of fault properties and behaviour with respect to fluid flow in reservoir production is a key industry goal.

At present there is no quantitative understanding of how fault-related diagenetic modification can be predicted, nor even a methodology to assess the spatial extent of diagenetic modification and its likely effects on production.

Achieving appropriate statistical sampling to characterise diagenetic processes on scales which allow interpretation of the controls, rules and underlying mechanisms, necessitates the use of outcrop in this project.

Objectives

The project aims from field and laboratory studies:

- to identify and quantify the effects of diagenesis, in terms of reducing or enhancing reservoir quality, around faults within siliciclastic sedimentary successions which are analogous to hydrocarbon reservoirs;

- to identify and quantify spatial diagenetic heterogeneity and scaling relationships, from rigorous analysis of diagenesis around faults at outcrop.

Synopsis

This is a multi-disciplinary study involving structural geology, diagenesis/ inorganic geochemistry and reservoir description/engineering. The project builds upon previous PSTI research funded from its Members' subscriptions in the areas of reservoir characterisation, fault sealing, fluid-rock interaction and fluid flow in complex reservoirs.

The project addresses the effect of the products of diagenetically significant fluids on reservoir quality of sandstones adjacent to faults. Detailed, quantitative investigations of outcrops are being undertaken using state-of-the-art field mapping techniques.

Deliverables

The major project deliverables will be:

Documentation of structural history and deformation geometries for faulted zones in the study areas.

Documentation of the effect of faults on the spatial distribution of authigenic cements and diagenetic textures.

Analysis of the role of primary depositional character on the spatial distribution of fault-related diagenetic effects.

Analysis of the appropriateness of conventional diagenetic spatial sampling routines (ie limited, small-scale thin-section studies based on vertical/subvertical core) for the prediction of larger scale patterns of diagenetic variability.

The definition of REA/REV-type scales of homogenisation for scaling-up the influence of diagenetic features on fluid-flow properties.

Documentation of the impact of various fault-related diagenetic processes on the primary depositional descriptive and spatial statistics of porosity, permeability and other rock property data.

Discussion of an appropriate methodology, for use with borehole core data and samples, on appropriate sampling statistics and analysis for studies into likely fault-related diagenetic effects in the sub-surface.

About the research providers

University of Liverpool, principal investigators: Prof Juan Watterson and Dr John Walsh Expertise: structural geology

University of Manchester, principal investigator: Dr Stuart Burley

Expertise: inorganic geochemistry and diagenesis

Heriot-Watt University, principal investigator: Dr Jon Lewis

Expertise: spatial statistical sampling and reservoir heterogeneity characterisation