Overcoming pore-pressure challenges in deepwater exploration

摘要

The OBG is a very important input parameter to most quantitative pressure estimation methods, and a lot of effort was made to ensure that the OBG used during drilling was the best possible, using offset density data and location seismic data. At the end of the well, wireline density data was used to calculate a final OBG. The pre-drill studies had indicated that the exponent method could be used reliably in this area for estimating PP, applying the standard exponents of 1.2 for resistivity and Dxc, and 3.0 for sonic. The PP estimates were updated constantly as the Dxc and resistivity data were received. The LWD gamma ray was used for definition of shale intervals, using an operator-maintained shale baseline, which was then applied automatically to the porosity-indicating logs to create "shale porosity" logs. Normal compaction trend lines were applied to these shale porosity data sets and used for direct calculation of pore pressure.