Correctly Allocating Injected Gas to Targeted Zones by Integrating Data from Spectral Noise and Temperature Logs

Gas Injection alone, or in Water Alternating Gas (WAG) mode to improve oil recovery (IOR) has been widely applied since the late 1950s. The incremental oil recovery attributed to IOR has been generally estimated at 5 – 10% over Secondary Recovery (water injection alone), primarily due to preferential sweep under gravitational effects. Theoretically, water and gas injection tend to have preferential sweep due to gravitational effects and formation characteristics. In practice, however, it is an operational challenge to obtain a uniform sweep across the reservoir.

One of the biggest challenges in understanding the injection behavior in gas injection wells using the conventional production logging approach is to identify the exact entry points, and to determine a representative injection profile to the actual injection volumes. Mechanical spinners provide inflow profiles within the borehole that in many cases doesn't reflect the actual gas behavior inside the addressed layers beyond the entry point.

Gas containment in the reservoir and within the targeted zone is one of the biggest hurdles. Unlike pilot projects, in full field application, channeling, cross flows, out of zone injection and premature breakthrough often occur, resulting in wasting gas, delayed response, and lower than expected recovery.

Effective reservoir management requires active & efficient reservoir surveillance in order to optimize well & reservoir performance. It is, therefore, critical to design a proactive program for data acquisition, integrating that data into a knowledge data base and to transform that knowledge into valuable information to guide future operations for remedial work, recompletion, infill drilling, and further development programs.

This paper discusses in detail how the injection profile geometry was described, and injected gas volumes were correctly allocated to targeted zones in one of the giant onshore oil fields in Abu Dhabi, UAE operated by ADCO, using integrated HPT (High Precision Temperature) and SNL (Spectral Noise Logging). Data from HPT and SNL logging package was integrated to successfully monitor water injection, identify cross-flows and locate casing leaks in injection wells for the past 2-3 years. Based on the performance, reliability, and accuracy of this advanced logging technology, ADCO has decided to use the same tools and temperature simulation to track gas injection, gas flow profile behind pipe, and to monitor any communication with any extraneous thief zones.