Paper: Applications Of The CarbonOxygen Log In Johnson (Glorieta) Field

In June 1978, the Carbon/Oxygen (C/O) Log began aiding formation evaluation in the Gorieta reservoir of Johnson Field, a moderately porous carbonate trend in central Ector County, eight miles northwest of Odessa, Texas. Production there is from four separate reservoirs - the Grayburg - San Andres, the Holt, the Glorieta, and the Upper Penn. Until recently, Glorieta development was limited by lack of oil shows in drilling samples, by poor drillstem test performance, and by high water saturations calculated from open-hole logging packages. But, results of the Carbon/Oxygen Log substantially contradict open-hole log interpretations and have led to successful completions in zones previously believed to be wet. Based on these data, eleven wells have been either drilled or recompleted to the Glorieta. The paper will review the history of Glorieta development in the ' Johnson area prior to use of the C/O Log and will briefly discuss the operation of the logging system. It will describe the logging suite now in use, showing a comparison of open-hole and C/O Log interpretations for the same wells. The C/O Log has seen only limited use in the carbonate formations of the Permian Basin, but possible suitability of the log in other West Texas applications is suggested. Information from this project will help other operators the suitability of the logging system in areas where open-ho unavailable or unreliable.