Techniques to improve flow profiling using distributed temperature sensing
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The emergence of Distributed Temperature Sensing (DTS) has led to much better instrumented wells, enabling operators access to real-time temperature data. Sophisticated nodal thermal/fluid models that analyze such temperature data provide many benefits and offer valuable information. Flow profiling is one of the most important field applications of DTS. Since temperature changes caused by fluid flow are typically small, the temperature resolution or noise level of the DTS traces becomes the limiting factor for accuracy in flow profiling. Noise can be caused by many factors, such as the time length to generate the trace and losses from optical connectors or splices. The two techniques most commonly used to reduce temperature trace noise are (1) averaging of separately measured traces; and (2) formation of a moving average along the trace (smoothing). The latter technique - smoothing - comes at the expense of a reduction in spatial resolution. Another limitation for DTS used alone for flow profiling is that it can only handle single-phase flow situations. Additional information, such as multi-point pressure data, is often needed for multiphase fluid flow profiling. In this paper, we describe our work with Fourier series to approximate DTS traces which offers greater flow profiling accuracy and avoids spatial resolution reduction. Our mechanistic model couples energy and momentum transport, enabling us to handle multiphase flow by integrating multipoint pressure measurements with DTS. This paper contains three field examples that demonstrate the following techniques resulting in improved flow profiling: 1. Use of Fourier series to approximate DTS traces (Fourier Approximation); 2. Use of Solver to determine Fourier series coefficients to minimize the sum of the squared error between the DTS traces and Approximation; 3. Use of iterative procedures to determine the best fit overall time interval T; and 4. Integration of multipoint pressure data with DTS for multiphase fluid flow applications Copyright 2010, Society of Petroleum Engineers.
