Abstract: Constructing 3-D Porosity and Fluid Pressure Models Using Surface Seismic and Well Data in the Eugene Island Block 330 Field, Offshore Louisiana, Gulf of Mexico

Wei He, Roger N. Anderson, Xue-Fen Wang

Present-day porosity and fluid pressure distribution of geological formations in sedimentary basins is of significant importance. The porosity variations of the formation often controls the reservoir extents and even the potential pore fluid migration pathway within and/or between different reservoirs. The fluid pressure, namely, the excess fluid pressure, is the effective driving force that defines the hydrodynamic state of a basin. Therefore, the integrated investigation of porosity and fluid pressure plays an important role in petroleum exploration and in enhanced hydrocarbon recovery practices. They not only provide basin analysts with an accurate present-day hydrodynamic configuration, but also geophysicists with an accurately defined lithology model for forward seismic modeling fforts.

We derive porosity and fluid pressure distributions from the integrated investigation of surface seismic and well data. In our area of interest, the sediments are composed of sand-shale sequences. We first investigate the lithology, porosity, and fluid pressure profile at each well site using SP, GR, sonic, bulk density, and drilling mud log data. The normal and abnormal compaction of sand and shale trends are obtained simultaneously, and the empirical relationship between the porosity and acoustic impedance is derived from sonic and neutron porosity logs. They are then used to calibrate the pseudo-acoustic impedance derived from 1-D seismic trace inversion at each well location. By using the well controlled pseudo acoustic impedance from 3-D post-stacked and migrated seismic data, we extrapolate the porosity and formation pressure interpretation away from the wells. Ultimately, we construct a 3-D porosity and formation pressure model within the coverage of 3-D seismic data. It is evident that the abnormal fluid pressure compartments are bounded by the major growth faults. These models provide much better observation of the porosity and fluid pressure than those derived solely from either seismic stratigraphic interpretation or well data.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994