Well integrity problems require unconventional diagnostic solutions; Conventional methods are limited to the borehole or first tubular assessment and cannot guaranty integrity issue accurate identification. Well integrity failure can affect production plans, environment and, consequently, lead to high economic impacts to fix the resulting damage. Once Sustainable Annulus Pressure (SAP) is confirmed, its source should be located and shut off as soon as possible.
Precise barrier diagnostic system shall be applied to identify integrity problems related to tubular leaks, communication pathways behind tubing and casing or through completion elements. This system consists of a set of conventional sensors and two advanced methods: high precision temperature sensor and high sensitive spectral acoustic tool. Both methods allow to receive information about any flow inside or behind tubing or casing and as a result, identify exactly integrity problem location and nature.
Spectral noise logging (SNL) is an acoustic wave measuring technique used to identify leak positions by recording acoustic noise generated by fluid or gas flow through the reservoir or leaks in downhole well components.
Offshore single string gas producer suffered from sustained A-annulus pressure of 110 bar and build-up rate 2 bar/hr. The well was completed with four packers: one packer below of target perforation and three above and sand screens across the perforated interval. To identify the source of A-annulus sustainable pressure, tailor-made logging procedures was implemented which consisted of two runs: baseline (static condition) survey after 24 hours well shut-in and the main survey (dynamic condition) under A-annulus bleed off condition. As a result, two sources of A-annulus pressure were identified: across the safety valve and second through three leaking production packers above perforated interval. According to these Findings the well was planned to be worked-over and workover results matched Spectral noise logging diagnostic system findings.
The technology for integrity surveys should satisfy specific requirements led by specific objectives. Integrity tools or techniques are focused on two main areas: evaluation of tubular conditions and identification of flows, for example, leaks.
