Pore pressure prediction using seismic and well log data, Canterbury Basin, New Zealand

Abstract

The history of petroleum production encountered drilling hazards such as pressure kick, blowout, fracture risk, reservoir formation damage, and lost circulation of mud, etc. that can impact wellbore stability while drilling. The geologists and geomechanics engineers have tried to avoid drilling hazards for safety and cost-effective drilling. The pore pressure must be predicted before drilling and while drilling. Consequently, the pore pressures are the crucial parameter for the calculation of mud weight before productive drilling. If the pore pressures are not accurately predicted before drilling, the influence of serious drilling incidents may be well blowouts or pressure kicks. Therefore, pore pressure prediction is the critical procedural in all oil companies to drill wells safely and well planning. In the present day, the formation pore pressure can obtain from wireline formation testers. Normally, the formation tester is a high-cost technique. As a result, oil companies try to predict pore pressure from the geophysical logs due to saving budget. In this study, the available well is only one well named Galleon-1. The well Galleon-1 is located at Canterbury Basin on the southeast coast of New Zealand. This area is the target of ongoing commercial petroleum exploration. Eaton’s method was used to calculate the pore pressure in the well. Then, the calculated pore pressure was adjusted until matched with the pore pressure from the formation tester. To create the pore pressure volume, seismic inversion was used to generate pore pressure volume for using in field scale. P-impedance and calculated pore pressure at the well were used to define the empirical relationship. After that, the relationship was applied to the inverted seismic volume. As a result, the pore pressure volume was generated by using seismic and well log data. The calculated pore pressure can interpret the type of compaction in the study area as under compaction. This type is classified by the difference between normal pressure and calculated pore pressure. In this study area, the Laing A, Laing B, Waipawa, Wickcliffe A, and Wickcliffe Formation were identified as under-compaction term or overpressure zone because the calculated pore pressure is higher than the hydrostatic pressure. This information can refer to the sediment loading rate as rapidly sediment loading.