Magister Scientiae - MSc (Earth Science) / The syn-rift succession encompasses the primary exploration target in the southern
Pletmos Basin. Several fault-bounded structural traps that contain gas accumulations
have been discovered within this succession. Likewise, ubiquitous residual gas shows have
been encountered in most drilled wells. Yet, the impact of faults on fluid flow is poorly
understood. Therefore, this study aspires to predict, and where possible, quantify fault seal
integrity and sealing capacities of some of the major prospect-bounding faults.
A multi-disciplinary research strategy was employed in order to fulfil the study
objectives. Fault mapping and geo-cellular modelling using geostatistical algorithms were
undertaken to provide the basic geometric and structural input for more advanced fault seal
analysis applications. Juxtaposition analysis was carried out to identify zones with a high
probability to seal (or leak) and as the first-order tool for predicting fault seal potential.
Threshold pressures, hydrocarbon column heights, cross-fault permeability and transmissibility
were used to estimate the sealing capacities of the faults. In addition to juxtaposition and
customary fault-rock properties, the study also analysed parameters that can be deemed to be
representative of cross-fault fluid flow (i.e. effective cross-fault permeability and
transmissibility; ECFP and ECFT). Finally, modelling of the geo-history facilitated the
validation of the properties that underpinned fault seal analysis studies.
The Ga-Q and proposed Ga-K prospects along with their main bounding faults formed
the foci of the fault seal analysis results. The analysed faults showed excellent initial sealing
potential due to either favourable juxtaposition or shale gouge development. Nonetheless,
predicted hydrocarbon column heights and threshold pressures were low suggesting that the
seal integrity of the analysed faults is predisposed to failure. In addition, high predicted fault
permeability and transmissibility values signify the presence of open and permeable fracture
networks within the fault zones. Thus, it is proposed that the faults are very likely to have
leaked during hydrocarbon migration and filling of traps resulting in empty or under-filled
hydrocarbon reservoirs.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uwc/oai:etd.uwc.ac.za:11394/6357 |
| Date | January 2017 |
| Creators | Mhlambi, Sanelisiwe |
| Contributors | Chatterjee, Tapas Kumar |
| Publisher | University of the Western Cape |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Rights | University of the Western Cape |
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