A compaction trend for non-reservoir North Sea Chalk

摘要

A compaction trend for the non-reservoir Chalk of the Central North Sea has been constructed using sonic interval transit time and density log data from 59 wells. The dataset used has avoide high porosity reservoir units and hydrocarbon-bearing chalks in order to emphasise the lower porosity, potentially pressure sealing units that make up the bulk of the Chalk Group. The compaction trend exhibits two stages: firstly to 5% at 4500 m. Porosity loss within the Chalk is predominantly due to mechanisms such as stylolitisation and grain-to-grain pressure solution. The decrease in the rate of porosity loss at about 1500 m depth may be due to the reduction of the effectiveness of these processes by overpressure development.