The newest production logging tools have multiple sensors that can provide valuable information concerning fluid types, fluid compositions, and fluid velocities, particularly in segregated flow environments. Since these tools include a relative bearing sensor, it is possible to determine where each sensor is located in the wellbore and flow stream. The interpretation of multiple sensors in a continuously changing wellbore environment required the development of software that combines navigational information about the location of the sensors in the flow stream, as well as data from the sensors relating to velocity and phase changes.
The Capacitance Array Tool (CAT) and the Resistivity Array Tool (RAT) provide detailed information regarding the wellbore fluids either consisting of gas, oil, and water or combination. It is possible to distinguish the segregation of the phases from the tool orientation and sensor physics. The Spinner Array Tool (SAT) provides velocity information from the six spinners, which are equally distributed around the wellbore. The combination of the 12 CAT and RAT readings with the six spinner readings required new processing to provide the necessary interpretation of these new array production logging measurements. Since the production logging tool string can rotate in the wellbore, differences in each sensors measurement between logging passes may be the combined effects of the sensor being in a different azimuthal orientation, changes in flow regime, or holdup.
New analysis methods have been developed to provide integrated interpretations of these new multi-probe sensors. New log presentations were developed to help display the segregated fluid profiles encountered that were previously ignored by the standard PL logging tools and processing. Several examples of deviated and horizontal wellbores with two- and three-phase flows are presented and discussed.
Traditional production logging tools with single sensors may not provide the most accurate answer in highly deviated and horizontal wellbores. These traditional PL sensors are usually center sample tools or have single point measurements for properties, such as velocity, phase components, temperature, and pressure. Phase segregation occurs in many wells, even including those with little deviation from vertical; the lighter phases migrate to the high side of the well, and the heavier phases migrate to the low side.
To accurately determine the flow rates from wells in which fluid segregation is expected, several new fullbore measurements tools have been developed to help address issues found with conventional tools. These tools described in this paper will be referred to as Production Array Logs (PAL) to distinguish them from the standard PL logs. Not only do the PAL tools have multiple sensors, these tools also have a relative bearing measurement to determine the position of each sensor in the wellbore. In addition, the SAT tool provides measurement of the wellbore deviation.
These new tools also require a new interpretation process that combines the benefits of the newer sensors and addresses problems that the deviated and horizontal wellbores cause in the standard PL interpretation procedures.
One of the challenges of production logging is to identify the types of fluids and the volumes of each fluid phase along with point of entry into the wellbore.