The role of faulting in Northern Carnarvon’s sub-basins in transferring very high overpressure
Edward Hoskin A * and Jakob Heller BA Ikon Science Ltd, Services, 1 The Crescent, Surbiton KT6 4BN, UK.
B Ikon Science Ltd, Services, 12140 Wickchester Lane, Suite 400, Houston 77079, USA.
The APPEA Journal 62 S431-S435 https://doi.org/10.1071/AJ21190
Accepted: 4 March 2022 Published: 13 May 2022
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of APPEA.
Abstract
Australia’s Northern Carnarvon Basin has experienced a varied geological history with periods of extension and thermal subsidence giving rise to separate sub-basins. Between the sub-basins the sequences of strata, their age, depth and rate of burial, and rock type vary greatly. Contrasts in rock type and burial rates are key variables that control generation of overpressure and, as such, create a wide range of pore pressure conditions from hydrostatic pressure to overpressure levels approaching values of vertical stress. Often these contrasting pressures can be situated relatively proximal to one another in both a horizontal and lateral sense. To improve pre-drill prediction capabilities for well planning in Northern Carnarvon, a study was completed in 2013 that included over 600 exploration wells and included reporting on areas at increased risk of high overpressure. One of the study findings was that reservoirs at sub-basin boundaries were often where the pressure was most variable and difficult to predict. The reason pressure was difficult to predict in these areas was due to high overpressure being transferred via faults at the margin of early Jurassic to early Cretaceous depocentres. In 2015, Hoskin et al. published the paper ‘Influence of faulting on reservoir overpressure distribution in the Northern Carnarvon Basin’ and this extended abstract looks at the Winchester-1 well, drilled after data were compiled for the original study, that validates the model presented in 2015, and also poses additional questions about the transfer of pressure.
Keywords: basin boundary, Carnarvon, distribution, fault, lateral transfer, overpressure, pore pressure, prediction.
Edward Hoskin graduated from Southampton University with a Master of Geology degree. His final year dissertation involved studying whether climatic indicators (that is the quartz/feldspar ratio) can be used to correlate the barren Permian sandstone sequences between wells in the North Sea. He has worked at Ikon Science for 12 years and has gained experience in all geoscience departments of the company. He initially worked in the Rock Physics team before moving to the Geopressure division to focus on delivering pre-drill pore pressure and fracture gradient well plans, and more recently Geomechanics and Wellbore Stability projects. He has completed projects in basins globally, from frontier areas such as in the sub-Arctic through to mature basins from the North Sea to North West Shelf, Australia, and the US Gulf of Mexico. |
Jakob Heller has an MSc in Geology from the University of Copenhagen, Denmark. His Master’s thesis was undertaken in collaboration with STATOIL (Equinor) Norway and the Technical University of Denmark (DTU) and focused on the sedimentology and diagenesis of the Middle Jurassic Garn formation, offshore Mid-Norway. He began his career working as a geologist in a geotechnical company in Denmark before moving to a position in Egypt that involved sedimentological analysis of core and building of geological models for exploration. In 2010 he joined Ikon Science as a Geologist and moved between various offices working on Pore Pressure and Geomechanics projects and is currently based in the Houston office as the Technical Manager for the Wells group (Americas). |
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