PREFERENTIAL FLOW IN A WEST TEXAS WATERFLOOD USING SURFACE TILTMETERS

Description of the Paper: This paper will report on the successful use of surface tilt mapping to identify preferential flow trends and hydraulic fracturing in the San Andres formation of the Reeves Unit in Yoakum County, Texas under normal waterflood injection operations. The results were obtained by monitoring the surface tilt induced during injection tests, falloff tests and flow back tests in injection wells along with the results from high rate acid treatments of producing wells. The results obtained are being used to optimize infill drilling locations and waterflood pattern orientation.

Application: Surface tilt mapping has been successfully applied to stimulation treatments, disposal projects and in numerous steam floods to provide information on fluid movements in the reservoir. This proven technology has now been applied to the San Andres formation at a depth of 5600 feet. Since typical injection rates in the San Andres are between 100 300 BWPD, a novel flow back method was developed to maximize the surface tilt response when testing injection wells under normal operating conditions.

Results, Observations, Conclusions: The tilt results showed conclusive preferential flow direction in the seven wells tested. In most wells, multiple tests were performed with good agreement on the flow trend. Based on these results, the Operator is evaluating infill drilling options and studying the potential of pattern modifications to enhance sweep and recovery.

Significance of Subject Matter:

1. Use of surface tilt mapping to properly align waterflood patterns to optimize recovery. 2. Use of a novel method to create large surface deflections from relatively low rate injections typical for normal operating conditions in San Andres waterfloods.