A computer model is presented for predicting downhole wellbore temperatures in flowing or shut-in fluid streams, in casing and cement, and in formations. Flowing options include injection/production, forward/reverse circulation, and drilling. Model predictions agree with field temperature data. The influences of temperature, flow rate, and depth on downhole temperatures are presented.
Temperatures in a well are important for many aspects of drilling, completion, production, and injection. A few applications that require an understanding of the downhole temperature history in a well include (1) cement composition, placement, and setting time, (2) drilling mud and annulus fluid formulation, (3) packer design and selection, (4) logging tool design and log interpretation, (5) wax deposition in production tubing, (6) corrosion in tubing and casings, (7) thermal stresses in casings and tubing, (8) permafrost thaw and refreezing, (9) wellhead and production equipment design, (10) drill bit design, and (11) elastomer and seal selection. Of course, many other applications may exist. Two interesting possibilities are computing undisturbed formation temperatures from flowing stream temperature measurements and anticipating abnormal pressure zones from fluid temperature changes while drilling.Hostile environments present even more challenging needs for downhole temperatures, while making it more difficult to determine what temperatures to expect. Any unusual temperature conditions can make previous temperature experience and intuition unreliable. Abnormal temperature gradients can cause a rapid rise in flowing fluid temperature, and unusually deep wells expose fluids to hotter temperatures for longer times. In arctic environments, cool permafrost zones can cause unexpectedly low temperatures throughout the length of a well, both in and below the permafrost. Conversely, geothermal wells exist in unusually hot regions, resulting in abnormally high temperatures in a well. An understanding of downhole temperatures is needed in hostile environments for the same applications as more conventional wells and perhaps for additional needs, but determining those temperatures is more difficult.Determination of downhole wellbore and earth temperatures is a complex task. Many variables influence temperatures, which are continuously changing with time. Temperature recording devices have been developed, but these provide only isolated data points for a transient quantity and, furthermore, cannot provide sufficient information to establish the relative importance of variables influencing temperatures. Therefore, a means of computing downhole temperatures is needed to determine important design criteria, such as maximum temperature and time for exposure to high temperatures. Many simplified analytical techniques and some correlations of experimental data have been constructed in the past, each with limited success in predicting downhole temperatures. Experience has demonstrated that a computer model is needed to account for complexities of heat transfer in a well.
JPT
P. 1509＾
