Abstract

In the Ford Geraldine Unit of Reeves and Culberson Counties, Texas, the most complete logging suites consist of the following: 1) Gamma Ray-LLD-MLL-Sonic, 2) Gamma Ray-LLD-MLL-Neutron, 3) Gamma Ray-LLD-Sonic; and 4) a few Gamma Ray-LLD-LLS-CNL-FDC. Because most of the gamma ray and neutron logs are “old logs”, the first step was to normalize them to the modern logs. Next, the sonic logs and normalized neutron logs were correlated to core porosity, and porosity transforms were calculated.

In wells with LLD plus MLL or LLS logs, Rt could be calculated by either Rt = 1.67*LLD-0.67*MLL or Rt = 2.4*LLD-1.4*LLS. In the numerous wells with only a deep laterolog, Rt was determined by a LLD versus Rt transform based on data from wells with LLD plus MLL or LLS logs.

Using a combination of core and log data, cementation exponent (m = 1.83) and saturation exponent (n = 1.90) were determined for the Archie Equation. A cross plot of 1415 porosity values and water saturations from 15 wells resulted in a critical BVW value of 0.07 when fitted to bulk volume water (BVW) curves. In order to test the effectiveness of this BVW value, porosity and water saturations were determined and cross plotted from two wells, one of which is structurally 294 feet lower than the other. Data from the structurally higher well plotted much nearer and more parallel to the 0.07 BVW line than the structurally lower well, thus indicating that the structurally higher well should have a lower water-cut. Production data for the month that produced the most oil indicates a 13% water-cut for the high well and a 53% water-cut for the lower well.