Supervision and Safety of Complex Systems

Chapter 13Time and Frequency Domain Approaches forthe Characterization of Injection States ¹

 

 

 

13.1. Introduction

13.1.1. Framework of the study

With the aim of characterizing injection states, we want to verify the following hypotheses:

– the frequential characteristics of signals recorded outside periods of injections and during the injections of water and argon are different; and

– the presence of an injection causes a modification of filtering characteristics between sources and the sensors. These modifications of characteristics differ from sensor to sensor.

Differentiation between “non-injection states” and ‘water injections’ must be independent of the water injection rate and any leak that occurs during the monitoring phase.

The aim is to develop methodologies that can be applied to other data or experimental situations without requiring too many additional studies. For this reason, the methods applied rely on a limited number of parameters whose significance is justified and automatic processing is necessary.

13.1.2. Processing recordings

The test recordings alternate between periods of non-injection and injection. Figure 13.5 gives a sample recording for the two signals taken from sensors and the injection command. For each recording, the place of injection is the same.

These recordings cannot be processed as a whole because they indicate different situations that must be distinguished from one another. It is therefore necessary to carry out initial processing to obtain ...