ABSTRACT: Integrating Geological, Logging, and Seismic Information for Pore Pressure Prediction

Fu, Li-Yun, Kevin Dodds, and Xiuming Wang , CSIRO Petroleum, Bentley, Australia

Pore pressure in its stratigraphic context and petrophysical parameters such as porosity, clay-content, lithology, pore fluid, saturation, permeability and other physical parameters are mutually interconnected in their acoustic response. Abnormal pore pressure generally has a marked effect on petrophysical properties, but the precise effect depends on the type of overpressure mechanism and its measure is subject to laboratory studies. Therefore, geophysical control on pore pressures is indirect, ambiguous, and is poorly determined. This points to the fundamental problem of non-uniqueness in pore pressure prediction. The ambiguous dependence of observed geophysical information related to subsurface pore pressures suggests that practical pore pressure prediction can be characterised by both physical mechanisms and its statistical behavior. Therefore, pore pressure prediction can be formulated as a probabilistic least-squares inversion incorporated with some deterministic petrophysical relations. A dual inversion method of inverse-operator-based inversion and forward-operator-based reconstruction has been developed in this paper as an interdisciplinary integrated approach for pore pressure estimation.

The entire procedure of pore pressure estimation is divided into two processes. First, a large number of laboratory testings of shale cores and well-data-based numerical modelings are needed to determine the relationships of pore pressure, petrophysical properties, and geophysical parameters. This process can also find the distinguishing geophysical features that are sensitive to abnormal pore pressures under the special geological conditions prevailing in the reservoirs. Then, the dual inversion method for pore pressure prediction is implemented based on the empirical relationships and selected geophysical features. This work has been carried out for the APCRC Abnormal Geopressure Research Program.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia