GASLOG - Numerical Modelling of Wireline Logs from Borehole Gas and Drilling Data

Measurements of gas contained in drilling mud are derived routinely during the drilling of boreholes. Gas data are obtained to identify changes in saturation, particularly when free hydrocarbon gases may be present, and to support safety control measures. Hence, the gas data are a subsurface signature and may be used for predicting lithology, permeability and fluid composition. Because gas data are acquired continuously during drilling, they can potentially be used to derive real-time estimates of subsurface characteristics. Our research investigates this potential and the potential for incorporating real-time drilling data, in the prediction of formation characteristics while drilling. <br><br>The conventional method of wireline logging in formation evaluation is an expensive, time consuming process in oil and gas exploration. Current research proposes an alternate inexpensive way of formation evaluation, which can be used alongside/instead of conventional methods. The current research focuses on predicting the fundamental elements of formation evaluation such as porosity and permeability using the available gas data and mass spectrometer data. The research has developed synthetic wireline logs in real-time, using advanced mathematical techniques, which can be interpreted analogous to conventional logs for formation evaluation. The validation of current methodology is demonstrated using North Sea test case wells.<br>