Simulating Downhole Temperature Logging Data for Optimum Downhole Production Surveillance

Abstract

Reservoir management best practices originate from efficient well operations. The fluid flow profile from individual wells can change over time, sometimes unpredictably; as the reservoirs become depleted, changes in hydrocarbon properties occur, and water cut begins to increase. During primary, secondary, and tertiary recovery from conventional and unconventional wells, production surveillance is pivotal for optimum reservoir management. Determining the downhole production flow profile from multiple zones helps to manage drawdown pressure, regulate surface choke settings, and mitigate excessive water production. This paper presents a rigorous mechanistic analysis of the heat transfer and fluid flow around the wellbore to aid in determining a generalized wellbore flow profile. The approach enables the calculation of multiphase rates independently of downhole spinner data and is based almost solely on temperature measurements. Because temperature measurements are reliable and more commonly available, the method provides a robust technique to determine flow contributions across a broad spectrum of surveillance applications. The technique is shown to work with other logs, such as capacitance, fluid density, and gas holdup tool, to relay more refined information about fluid phases during production. The methodology presents an application of transient-temperature modeling for computing flow rates from temperature data obtained during a wireline run. The approach includes an analytical wellbore fluid transient-temperature model. Temperature calculations depend on mass flow rate and flow duration; therefore, an inversion technique is applied to match the measured temperature and calculated temperature for a given time duration to estimate flow rate. The model is observed to depend on determining an accurate geothermal gradient, particularly in cases of early time flow. The various heat transfer resistances in the system are calculated based on the completion mechanics. The method also accounts for the effect of friction and pressure drop in the wellbore on fluid temperature. The case study included demonstrates the utility and value of the transient model. The transient nature of the model also facilitates multiple applications. Real-time flow rate monitoring, zonal contributions, flow behind casing, quantitative determination of leaks, and completion integrity are all potential applications of the proposed method. The transient-temperature modeling methodology can be used with production logging spinners to calibrate the model and provide a permanent downhole monitoring tool to help avoid costly logging reruns. The study provides a foundation for various applications arising from conventional production logging measurements and could be particularly useful in cases, such as offshore fields, where more evolved unconventional techniques can be difficult and costly to apply.