Predicting the impact of faults on fluid flow in hydrocarbon reservoirs

Summary of the Impact

Research on faults and fluid flow led by the University of Leeds has dramatically increased the ability of the petroleum industry to predict the impact of faults on fluid flow in petroleum reservoirs. The work has allowed the industry to reduce the risks associated with the exploration of faultbounded reservoirs, and to identify areas of un-drained reserves in producing reservoirs. The research has won a series of important industrial and academic awards, and has provided a
platform for the growth of Rock Deformation Research, a successful consultancy spin-out company whose turnover rose from £1.93 million in the period 2008-2010 to £4.0 million today.

Underpinning Research

Faults within petroleum reservoirs can act as significant barriers to fluid flow and therefore knowledge of their flow properties is essential so that production strategies can be planned to maximize recovery and increase profit. Despite their importance, prior to the mid-1990s there was little understanding of and virtually no quantitative data available on the flow processes and permeability of faults in petroleum reservoirs. Consequently, petroleum engineers were forced to guess the values of fault rock permeability when modelling fluid flow in petroleum reservoirs.

Between 1994 and 2005, Rob Knipe and Quentin Fisher led a series of frontline Joint Industry Projects (JIPs) and NERC grants (e.g. GR3/5765, GR3/4612) at the University of Leeds to remove this knowledge gap. These JIPs were integrated/multidisciplinary studies of faulting mechanisms and fluid flow behaviour; and the generation of a robust database on the structure and petrophysical properties of faults within petroleum reservoirs. Three of the JIPs built up the most
extensive database of the permeability and capillary entry pressure of fault rocks ever generated.

Rock Deformation Research (RDR), an applied research Fault Foundation programme, was established in 1997 as a University of Leeds spin-out company to assess faulting processes and flow behaviour. With 15 company sponsors in 2012, RDR represents one of the largest active global structural geology consortia. This project built up the data and knowledge on sub-seismic structure of faults based on extensive outcrop studies. Some results from the studies of faults in
petroleum systems were published [1,2,3,4], although most remain confidential.

University of Leeds research has pioneered the determination and prediction of flow properties in faulted reservoirs. In the early 2000s, Knipe, Fisher and their team became the first scientists to recognise and provide evidence for the potential importance of incorporating the multiphase flow properties of faults into production simulation models [3,5,6]. The research showed that it was important to understand the multiphase flow properties of the fault rocks to predict whether or not other reservoir compartments need to be drilled. Unfortunately, no data were available on the multiphase flow properties of fault rocks.

The University of Leeds responded by investing nearly £2 million in building a state-of-the-art multiphase flow laboratory. This provided an important platform for the School of Earth and Environment’s petroleum research programmes, and for the initiation of a large JIP involving 9 major oil companies to make the first ever measurements of the relative permeability of fault rocks [6]. The Wolfson laboratory has now received over £2 million of sponsorship from industry (BG, BP, Chevron, ExxonMobil, EBN, Perenco, Petrobras, Shell, Statoil, Total, and Wintershall).

The University of Leeds continues to host a thriving group of more than 10 academics, post-docs and PhD students conducting frontline research on the impact of reservoir deformation on fluid flow. Results of the multiphase flow properties on fault rocks have recently been published in the journal Geology [5], which has led to Leeds being commissioned to undertake a study on the potential impact of faults on CO2 injection on one of the only few sites currently being appraised for
offshore storage of CO2 in the UK.

Key researchers

Quentin Fisher, Researcher, University of Leeds spin-out company RDR (1992-2008); Principal Researcher (2003-2007) and Professor of Petroleum Geoengineering (2008-present) in the School of Earth and Environment, University of Leeds.
Rob Knipe, Professor of Structural Geology (1995-present, now Emeritus) in the School of Earth and Environment, University of Leeds; Director, Chairman and Technical Lead of Consulting Group (1992-present), Rock Deformation Research.

References to the research

1. Knipe, R.J. (1997) Juxtaposition and seal diagrams to help analyze fault seals in hydrocarbon reservoirs, American Association of Petroleum Geologists Bulletin, 81, 187-195.
2. Fisher, Q.J. and Knipe, R.J. (1998) Fault sealing processes in siliciclastic sediments, Faulting and Fault Sealing in Hydrocarbon Reservoirs, Geological Society, London, Special Publication, 147, 117-134.
3. Fisher, Q.J. and Knipe, R.J. (2001) The permeability of faults within siliciclastic petroleum reservoirs of the North Sea and Norwegian Continental Shelf, Marine and Petroleum Geology, 18, 1063-1081.
4. Freeman, S.R., Harris, S.D. and Knipe, R.J. (2008) Fault seal mapping incorporating geometric and property uncertainty, Geological Society, London, Special Publications, 309, 5-38.
5. Tückmantel, C., Fisher, Q.J., Manzocchi, T., Skachkov, S., and Grattoni C.A. (2012) Twophase fluid flow properties of cataclastic fault rocks: Implications for CO2 storage in saline aquifer, Geology, 40, 39-42.
6. Zijlstra, E., Reemst, P., and Fisher, Q.J. (2007) Incorporation of the two-phase flow properties of fault rocks into production simulation models of the Roliegend reservoirs, Structurally Complex Reservoirs. Geological Society, London, Special Publication, 292, 295-308.