Method and Application of Horizontal Slice Volumetrics to Waterflood Management and Horizontal Drilling

Harvey A. Deutsch, David E. Hamilton, and Robert Douglass

A computer mapping program was used to make horizontal slices of pore volume. The goal was to create maps that showed the distribution of pore volume vertically and laterally throughout the reservoir. That information was used for: studying waterflood feasibility, monitoring an existing waterflood, and planning a horizontal well. This work was done at the United States Naval Petrnleum Reserve No. 1, Elk Hills, CA. The reservoirs are the Miocene aged Northwest Stevens "A" sands and T&N sands. These sands are a series of stacked deep water turbidites draped across the western nose of a plunging anticline.

To determine the reservoir sensitivity to the approach used to calculate horizontal slice volume, two methods were tested. The first involves creation of four isochores, bounded above by the sand top or base and below by the slice top or base, whose volumes are combined to give the slice volume. The second involves creation of a grid of the slice itself from which slice volume is calculated.

In the A1 and A2 sands, which are under gas injection, hydrocarbon pore volume maps were made of the interval between the oil/water contact and the gas/oil contact to delineate horizontal well locations. In the A4, A5 and A6 sands, which are under peripheral waterflood, pore volume in 100-foot intervals combined with cumulative water injection data, allowed estimation of the highest oil/water contacts and flooded out sublayers. In the T&N sands, for a waterflood feasibility study, pore volume in 100-foot increments was used to determine volume of hydrocarbons in place and, with material balance calculations, was used to determine waterflood encroachment.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California