Mark Tingay

PhD Student




Telephone: +61 8 8303 4300
Facsimile: +61 8 8303 4345
E-mail: mtingay@ncpgg.adelaide.edu.au


PhD Project:

In-Situ Stress and Overpressures of Brunei

Commenced: 1999

Supervisor: Prof Richard Hillis

Project Support: ARC Large Grant, Brunei Shell Petroleum, Total Fina Elf

Scholarship Support: Australian Postgraduate Award

My Ph.D project involves a detailed study of the in-situ stresses and pore pressures of the Baram Basin, Brunei. Pore pressures and contemporary stresses are of importance to the petroleum industry because they influence:

  • Borehole stability;
  • Fracture stimulation;
  • Fluid flow in naturally fractured reservoirs;
  • Fault sealing;
  • Timing and direction of hydrocarbon migration;
  • Well design and drilling safety, and;
  • Structural models of recent tectonics.

    The Baram Basin is a Tertiary delta deposited upon an active margin. This unusual tectonic setting has led to a variety of features important to the petroleum exploration and production, in particular widespread overpressures and complex tectonics. Overpressures in the region have caused major problems for well control and drilling safety. The complex tectonics has resulted in highly compartmentalised fields that require large numbers of wells to produce.

    My research into overpressures of Brunei involves the detection, characterisation and prediction of high pore pressures. Overpressures in Brunei are widespread, commonly of high magnitude (sub-lithostatic), have narrow transition zones and are compartmentalised. Hence, overpressures pose a major drilling and production risk in the region. The rapid deposition (3000 m/Ma) of fine-grained sediments has led to basin-wide overpressures due to disequilibrium compaction. Disequilibrium compaction overpressures are associated with undercompacted sediments and with mobile shale features such as shale diapirs, dykes and mud volcanoes. However, overpressures in Brunei have also been vertically transferred through faults and fractures, thereby inflating pore pressures in shallow reservoirs. Overpressures that have been vertically transferred do not exhibit undercompaction and are difficult to detect. However, my research has shown that inflationary overpressures in Brunei can be detected on sonic logs and therefore may also be detectable prior to drilling by seismic techniques.

    In-situ stresses are directly coupled with pore pressure and are a controlling factor in recent tectonics. My research on the in-situ stresses of Brunei is focussed on stress field variations across the basin and associated implications for petroleum exploration and production. The contemporary stress of tertiary deltas on passive margins has been widely studied. However, very little research has been made of deltas on active margins. In Brunei there is a complex interaction between typical gravity-driven deltaic tectonics and wrench/thrust tectonics associated with the active margin.

    My research has shown that the vertical stress (weight of the overburden) varies greatly across the Baram Basin, a feature not reported in other Tertiary deltas. Such variation has important implications for pore pressure prediction, borehole stability and fracture stimulation in Brunei. My research also indicates that the present-day maximum horizontal stress direction is margin-normal. This direction is perpendicular to the stress field that created the margin-parallel structures observed in the delta. The orientation of the maximum horizontal stress is a controlling factor on fault sealing, hydrocarbon migration and production. Increasing pore pressure gradients with depth are coupled with higher minimum horizontal stress magnitudes. In Brunei my research suggests that there is a normal faulting stress regime in the shallow, hydrostatic pressure sections of the delta. However, as pore pressures approach lithostatic gradients the stress field changes to a strike-slip or thrust faulting stress regime. Knowledge of the stress regime can be used to improve production and borehole stability.


    Biography

    Mark Tingay studied Geology and Geophysics at Adelaide University, completed Honours Geophysics in 1998 with a thesis titled "Conductivity structure of the weathered zone at Number Four Tank, Cobar, NSW". He commenced a PhD in1999 studying in-situ stress, overpressures and neotectonics of Brunei Darussalam. Currently studying at the NCPGG. However, has also spent a few months studying at Durham University in the UK. He is a member of AAPG, EAGE, SPE, SEG, ASEG and PESA.


    Publications

    Electrical and Transient Electromagnetic Modelling of a Copper Prospect near Cobar, NSW. Tingay M.R.P., Brooker P.I., Basford P. Modelling and Simulation Society of Australia and New Zealand 2001 Congress (in press).


    Conference Presentations

    The Sonic and Density Log Expression of Overpressure in Brunei Darussalam. Tingay M.R.P., Hillis R.R., Swarbrick R.E., Mildren S.D., and Okpere E.C. Overpressure 2000 Conference, London, 2000

    In-Situ Stress and Overpressures of Brunei Darussalam. Tingay M.R.P., Hillis R.R., Swarbrick R.E., Mildren S.D., Morley C.K. and Okpere E.C. American Association of Petroleum Geologists International Conference, Bali, 2000