Summary Most crude produced in Kuwait is from naturallyflowing wells. Casing, tubing, and cement in thesewells remain unchanged after completion. This paperdiscusses the major application of temperaturesurveys in indicating fluid movement both inside andbehind the production string, hence locating anyholes in the casing. Some significant cases oftemperature anomalies are examined qualitatively, and suggestions are made for a more quantitative interpretation of temperature profiles. Introduction Temperature surveys have been employed in thepetroleum industry for the past 50 years, and theirstatus has been elevated to one of the essential operations, especially when high temperatures indeep wells caused premature setting of cement beforeit could be placed behind the casing. From then on, the temperature logging tool was used to locate thetop of newly cemented casing, for recordingbottomhole temperatures, and for locating mechanical defects that would cause a temperature change downthe borehole.At Kuwait Oil Co., it was suspected that corrosionof the intermediate casing was due to the channelingof formation water behind the casing string. Many wells initially were not protected cathodically againstcorrosion, substantiating this view. To test thisphenomenon, temperature surveys were initiated by Kuwait Oil Co. Before 1967, temperature surveyswere run in isolated wells, but since then most of thefields have been covered systematically (although notcompletely).To date, the basic use of temperature surveys run in Kuwait has been to detect any holes in the casing, since the migration of fluid in the wellbore causes atemperature anomaly (this fluid may be inside theproduction string or behind the casing). In 1979, 63temperature surveys were run in Kuwait to detectwells suffering from this problem. Information onother causes not directly related to fluid movementcannot be obtained from temperature surveys untilthe production string becomes holed, resulting influid movement in the wellbore.The temperature tool used to conduct these surveysin Kuwait is the thermometer made by Amerada Geophysical Research Corp. of Tulsa. However, theradial differential temperature logging tool (RDT)2has been introduced into the market recently byGearhart-Owen Industries Inc. The practicalapplications of the RDT will be considered in the nearfuture to detect vertical flow outside the casing. Theadvantage of the RDT is that its two arms equippedwith temperature sensors contact the casing walls.Thus, the flow channels behind casing can be locatedby observing temperature anomalies that result fromflow through channels.Pierce et al. indicate the application oftemperature surveys to locate holes in the productiontubing as well as in the casing. They also show onetypical case of communication behind the casing. Basic Principle and Technique The basic idea in downhole temperature surveys isnot new. Heat energy flows from regions of higher tolower temperature. Transfer of heat takes place bythree different mechanisms: conduction, convection, and radiation. Which of these mechanisms isdominant at different depths is not understood fully.The most common type of thermometer used inKuwait to make bottomhole temperature surveys isthe Amerada. Essentially, the thermometer consists of a bulb sealed to a helical bourdon tube. The bulband tube contain a volatile fluid. JPT P. 2505^
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May 1, 1987
Stephen J Henderson + 1
Open Access