The Temperature-Sound Log And Borehole Channel Scans For Problem Wells
Authors: Pennebaker E.S. , Woody R.T. 
Published: December 2007

The diagnosis of downhole communication problems in producing and injection wells has problems in producing and injection wells has long benefited from use of the temperature log. In recent years, however, the noise logger has added a new dimension through its ability to hear the downhole problem in action. Each tool has its limitation, however, and each log by itself is often difficult to interpret. This paper discusses a survey during which, in a single trip into the hole, both temperature and sound profiles are measured. The two reinforce each other and enhance interpretation. If the problem is a behind-casing fluid leak, the temperature and sound anomalies however can only point out the depth and order-of-magnitude. point out the depth and order-of-magnitude. Successful repair depends upon direct access to the channel by the squeeze cement. Examples are shown illustrating the use of the borehole density scanner, or density orienting tool commonly used in oriented perforating, for directing the perforations into the perforating, for directing the perforations into the channel for repair. New tools for pinpointing the channel are also discussed. Field pinpointing the channel are also discussed. Field examples are presented to show the importance of planning surveys and how surveys of isolated segments of the wellbore, particularly if presented on too large a scale, may result in overlooking important clues.

Introduction

The diagnosis and repair of behind-casing leaks has long been one of the industry's most persistent and difficult problems. The means most often used in hunting for flow behind casing has been the temperature log. However, the anomalies in the temperature and differential temperature logs are often quite confusing, and sometimes fail to detect movement that is actually taking place. This is particularly true when the cross sectional area of the channel compared to the volume of the borehole is very small. McKinley (1972) introduced a new method of detecting behind-casing flow, which involved listening with a sensitive downhole microphone for evidence of flow, then tracing the leak to the sourse as evidenced by a noise peak. From empirical relationships which he developed from simulated behind-casing leaks, he showed how not only the type of flow, i.e. single or two-phase, could be identified, but of more importance, how an order-of-magnitude rate of flow can be calculated from the noise intensities measured in appropriate frequency bands. All "noise log" services in use at the present time are based on this work, and all tools are calibrated against a standard Exxon Production Research Co. tool in Houston.

Recently there have been several excellent papers published dealing in detail with the papers published dealing in detail with the theory and field application of the noise log. Britt (1976) discussed additional work by McKinley on methods for (1) profiling flow through individual perforations or groups of perforations in producing wells, and (2) for use of the noise logger as a downhole flow meter having no moving parts. Numerous examples and detailed calculations have also been presented by Robinson. The theory and application of the tool is therefore believed to have been adequately covered and will not be discussed in detail here.

Considerable interest has been shown by the industry in the tool and its applications, but disenchantment has resulted from the difficulty of interpretation. Errors in interpretation of the downhole problem have resulted. Interpretations of temperature logs and noise logs run independently in the same well have at times resulted in serious disagreements.