Standard PLT strings can be run in horizontal wells using the coiled-tubing to convey the tools. However, standard PLT will not be useful in wells having multi-phase flow (gas/oil/water). Different phases will segregate across the hole diameter, thus the flow measured in the middle will not be a good representative for the real. To get accurate measurements of flow rates and phases in horizontal wells, NPS provides the Multi-Array Production System (MAPS). Spinners, capacitance and resistance sensors are all distributed across the diameter of the well to provide the maximum coverage and hence the most accurate measurements possible. MAPS consists of 3 components:
1. Spinner Array Tool (SAT):
The Spinner Array Tool (SAT) is designed to solve the problem of accurate fluid velocity identification in horizontal or highly deviated wells. It is run centralised within the wellbore. The tool has an array of 6 specially developed miniature spinners, mounted on the inside of a set of springbows. Each spinner of the array measures the fluid velocity and direction of the surrounding fluid close to the well casing. Rotation is sensed by Hall Effect detectors, which eliminate drag and optimise measurement flow rates. The normal output is 3 pulses per revolution with indication of direction. All 6 values are simultaneously transmitted to either the surface or into a Memory section. Because the measurements are taken in a single plane across the diameter of the wellbore, rather than spaced along it, an accurate cross-sectional plot can be generated.
2. Capacitance Array Tool (CAT):
The prime use for the Capacitance Array Tool (CAT) is to obtain an accurate across wellbore 3 phase holdup measurement in deviated and horizontal wells where there is stratified flow. In these situations, using CAT data will result in a more accurate interpretation compared to traditional centre sampling tools. The tool is run centralized and has an array of 12 micro-capacitance sensors deployed radially on bowsprings. Due to the high number of sensors in a single plane the data from the tool can be used to generate a 3D image of the phase distribution. The tool can also be used when there is bubble flow or an emulsion. As the tool samples the periphery of the wellbore the tool is best run in combination with a centre sampling holdup tool. The client can then obtain a full representation of the flow conditions.
3. Resistance Array Tool (RAT):
The Resistance Array Tool (RAT) is designed to solve the problem of accurate fluid phase identification in horizontal or highly deviated wells. It is run centralised within the wellbore, ideally combined with an Inclinometer tool to aid interpretation. The tool has an array of 12 specially developed miniature sensors, mounted on the inside of a set of springbows. Each sensor senses the apparent resistance of the fluid at a specific point across the area of the pipe so that the time variation of the characteristics can be monitored. The monitored resistances, as they vary with position and time, can be interpreted to improve the understanding of what is flowing through the pipe. This insight can then aid decisions about maintenance or further development of the well or pipeline. Because the measurements are taken in a single plane across the diameter of the wellbore, rather than spaced along it, an accurate cross-sectional plot can be generated. Optional software can be used to provide a 3D image of the phases along the well.