Specialized Applications of Noise Logging
Authors: McKinley R.M. , Bower F.M. 
Published: December 2007

This paper describes the use of the noise logging technique to monitor flow inside casing. Calibrations for the following flow situations are shown: axial flow past the sonde, flow from perforations, liquid production from gas-zone perforations, and sand production from perforations. The forms of the correlating equations are independent of specific tool design.

Introduction

A 1973 paper described how the noise logger can detect flow through poor-quality cement behind pipe. This idea is illustrated in Fig. 1. Turbulence pipe. This idea is illustrated in Fig. 1. Turbulence generated by fluid moving from Sand A to Sand C creates within the tubing a sound field whose intensity is greater than the ambient noise level in the wellbore. The logging sonde, which is simply a microphone, transmits this sound level to the surface, where it is decomposed into frequencies characteristic of the type of flow. A depth record of noise level will reveal peaks at those locations where the fluid rapidly changes velocity. For example, see entry point (A), constriction (B), and exit point (C) in Fig. 1.

For this type of application, the noise log complements the temperature log very well. But this tool has other uses, too. We have found that the noise log is a valuable aid to logging methods that track fluid movement in the wellbore. The purpose of this paper, therefore, is to extend noise logging paper, therefore, is to extend noise logging technology into the general area of flow inside casing. Specifically, we discuss how to calibrate the sonde for use in the following situations:axial flow past the sonde,flow from perforations,liquid production from gas perforations,sand production from perforations.

For each case, the production from perforations. For each case, the particular calibration coefficients refer to the particular calibration coefficients refer to the standard detector sensitivity and load described by McKinley et al.

Noise From Axial Flow Past Sonde Single-Phase Flow

Suppose that the logging sonde is hanging in a wellbore down which water is being injected. The velocity increase acquired by the water while flowing past the sonde will generate turbulence. This can be past the sonde will generate turbulence. This can be detected as noise. Recall the familiar hiss from overhead pipes in steam-heated buildings. We can expect a similar sound from flow past the logging tool. The experiments described in Ref. 1 show that a single-phase fluid accelerating across a constriction radiates a noise intensity directly proportional to the pump work required to move the fluid. The same pump work required to move the fluid. The same concept applies here. If p is the pressure differential required to flow a volumetric rate, q, past the sonde, then the resulting noise level should be proportional to the product pq.

This is, in fact, the case, as Fig. 2 shows. Data in Fig. 2 were measured in a flow loop with a vertical test section whose diameter varied over the range indicated. Flow rates varied from 0.1 to 30 Mcf/D. From the data correlation, we have N*600 = A x pq, where A is a constant and N*600 is the noise level (at standard sensitivity) above 600 Hz. For turbulent flow, p=Bp(q/As), where B is a drag coefficient, p is the fluid density, and As is the cross-sectional p is the fluid density, and As is the cross-sectional area for flow between the pipe wall and sonde.

JPT

P. 1387