This thesis demonstrates the use of a mixture of standard and novel petrophysical techniques to estimate physical parameters of mudstone and explores the use of a generic, clay fraction-dependent compaction model in the context of pore pressure evaluation. Mudstones are often highly heterogeneous, yet many authors use a single compaction trend to describe their behaviour. Previous work has shown that the rate of a mudstone's compaction with vertical effective stress is a function of its clay fraction, the proportion of the sediment matrix with a particle diameter of less than 2μm. This observation forms the basis of the generic mudstone compaction model used in this thesis. The use of the generic compaction model is explored in two case studies using characterised mudstone samples and wireline log data from the Gulf of Thailand and Gulf of Mexico. Further mudstone samples from the Central North Sea were characterised. An error analysis showed that the compaction model can provide estimates of pressure to within ±1.8MPa at a burial depth of 3km (equivalent to ±0.5ppg mudweight) when the input parameters are constrained to an attainable level. In both cases studied, standard methods of analysis could not provide reasonable estimates of pressure in mudstone using wireline resistivity and porosity log data compared to pressure measurements in associated sand bodies. The deep sediments of the two wells studied from the Gulf of Thailand are overconsolidated with respect to their current stress state. The generic compaction model was used to determine that the overconsolidated sediments were uplifted by 1,300m and have been reburied beneath 900m of sediment that now overlies a regional unconformity. The generic compaction model was used in conjunction with an artificial neural network technique for the characterisation of mudstones from wireline data to determine pressure estimates in the mudstones of three deepwater wells in the Gulf of Mexico. A pressure transition zone in one well was shown to be associated with a 10% increase of mudstone clay fraction within the zone compared to surrounding rocks. In both case studies disequilibrium compaction was identified as the key overpressure generation mechanism.

Numerical simulations indicate that hydrocarbon migration and entrapment in stacked fault-bounded reservoirs are mainly affected by the following factors: charge time, faults, pressure and geological structures. The charge time for commercial hydrocarbon accumulation is much longer in oil-water systems than in oil-gas-water systems. Faults are classified into charging faults and 'back doors' faults other than charging faults in stacked fault-bounded reservoirs. The lower the displacement pressure of a fault, the higher its updip oil transportation ability. The downdip oil transportation ability of a fault is usually low and cannot cause commercial downdip oil accumulation. Back doors affect both hydrocarbon percent charge and hydrocarbon migration pathways. Updip back doors improve updip oil charge. The lower the displacement pressure of an updip back door, the more efficient the updip oil charge before 3,000 years. Back doors whose displacement pressure is equal to or higher than 28.76 psi are effective in sealing faults in oil-water systems. On the contrary, only sealing faults result in commercial gas accumulations in stacked fault-compartmentalized reservoirs. Otherwise gas is found over oil. Downdip back doors generally have few effects on downdip hydrocarbon charge. Geopressure enhances the updip oil transportation of a fault and improves the positive effects of updip back doors during updip oil charge. Geopressure and updip back doors result in more efficient updip oil charge. A physical barrier is not necessarily a barrier to oil migration with the aid of geopressure and updip back doors. The chance for hydrocarbon charge into reservoirs along growth faults is not equal. Any one of the above controlling factors can change the patterns of hydrocarbon charge and distribution in such complex geological structures. Generally, lower reservoirs and updip reservoirs are favored. Reservoirs along low-permeability charging faults may be bypassed. Gas can only charge the updip reservoirs. Both updip and downdip back doors can facilitate oil penetrating a barrier fault to charge reservoirs offset by the barrier fault. Interreservoir migration among stacked fault-compartmentalized reservoirs is an important mechanism for hydrocarbon accumulation and trap identification. The interreservoir migration is a very slow process, even though the displacement pressures of bounding faults may be very low.