--> Abstract: Rock Property Data Volumes from Well Logs; #90063 (2007)

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Rock Property Data Volumes from Well Logs

 

Denham, Leslie Richard1, H. Roice Nelson2 (1) II&T, Houston, TX (2) Geokinetics Processing & Interpretation,

 

Geology is sampled densely by wells vertically, but sparsely and irregularly horizontally. A modern seismic survey has sparse samples vertically, but close and uniform sampling horizontally. Seismic data is more useful for regional trends, but does not convey petrophysics, and is difficult to relate to wells. Inverting seismic data to resemble well data is almost impossible. Can we make well data resemble seismic data, not just a single-trace, but a complete volume?

 

We reduced well vertical sample interval to 60 m, computing numerous petrophysical properties. Then we computed vertical arrays of values for each property on a regular grid, using the samples computed at each well location. Wells within a specified radius were used, weighted inversely with distance, and well samples over a limited depth range, weighted inversely with depth difference from the sample depth. The computed three-dimensional array was written to disk in SEG Y format, and loaded into a seismic interpretation system.

 

In the initial project we generated data volumes for shale and sand P-wave velocities and densities, sand percentage, and pressure (mud weight), for most of the Gulf of Mexico. These volumes showed regional trends within the basin. The method has some problems in areas of sparse well information, and does not account for major structural features.

Petrophysical data volumes generated from well information allow the geologist to integrate information from thousands of wells using standard interpretation systems. So far, the technique seems to be more suited to regional analysis rather than to prospect development.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California