EFECT: A tool for pore pressure projection and data management

Advance information about local pore pressure distribution is crucial for the drilling of deep geothermal wells. Incorrect adjustment of the drilling mud density leads to drastic differences between wellbore pressure and the ambient pore pressure. Large pressure differences may result in severe drilling problems such as kicks, wellbore instabilities and subsequent partial or full loss of the previous borehole progress. In particular for small geothermal ventures on a communal level, this loss may pose a significant financial risk. We present current work on EFECT, a tool that helps to organize existing pore pressure measurement data and to generate geologically informed pore pressure estimates based on these existing data. EFECT integrates geographic information system (GIS) components that allow the user to explore pore pressure data sets and select offset wells for a planned well location. As a first step, the regional aggregate pore pressure model shows general features of the regional pore pressure with depth. The core feature of EFECT is the projection of the offset wells’ pore pressure to the target well based on matching stratigraphic units. Two projection algorithms are provided that assume either (1) overpressure or (2) vertical effective stress is constant between target and offset wells. EFECT is part of a larger effort to develop a global pore pressure database with a standardized quality ranking. The data from this database, consisting of pore pressure measurements and indicators such as well tests, kicks and mud weight data, provide a standard that users may augment with their own data. This standard data set can be particularly useful for small geothermal ventures. We illustrate EFECT using data from a precursor of the global pore pressure database covering the SE German part of the North Alpine Foreland Basin (Bavarian Molasse Basin).