Monitoring and handling Sustainable Annulus Pressure

Monitoring and handling
Sustainable Annulus Pressure
SEPTEMBER / 2015
Monitoring and handling Sustainable Annulus Pressure (SAP) is a daily challenge in today’s oil and gas industry. Well integrity failure can affect the production and the environment and, consequently, lead to high economic losses. Once SAP is confirmed, its source should be located and a remedial work should be planned to shut it off as soon as possible.
September_2015_image2One of the challenges the industry experiences to determine SAP is the ability to identify leaks behind multiple barriers. These leaks are not clearly seen by conventional temperature and noise logs. TGT cutting edge developments in spectral noise logging (SNL) and high precision temperature (HPT) along with robust interpretation techniques have been fundamental to identify the sources of SAP in the B and C annulus helping our Clients planning the proper remedial work.
The example bellow, shows a successful case of leak repair. This well was commissioned in May 2000. In June 2008, our Client confirmed a 735 psi pressure build up in Annulus C between 13 3/8” and 18 5/8”. The pressure was released and built up again in few hours. A conventional set of tools were run however the survey failed to identify the source of the leak.

After the unsuccessful series of attempts, TGT was called in order to perform the survey utilizing Spectral Noise Logging (SNL) and High Precision Temperature (HPT).
As you can see above, during the shut-in a significant change in temperature is seen throughout Zone A and B. At the same time the Spectral Noise Log (SNL) shows no leaks under shut-in.
During the bleed off pass, the temperature anomaly was detected again over the same intervals. Such temperature behavior is associated with fluid/gas entry into the C annulus. At this time, the Spectral Noise Log (SNL) during bleed off detected a major flow zone within Zone B representing a leak. In addition, a low-frequency noise less than 1000 Hz indicated upflow from Zone B all the way up to the surface. SNL also detected minor flow across Zone A, which indicated jointly with a relatively low temperature perturbation, an active leak.
September_2015_image4The differential temperature log shows cooling in both inflow zones, A and B, caused by gas expansion due to the choke effect. The above data have clearly shown that Zone A and Zone B can be interpreted as leak intervals. The slight temperature cooling and low amplitude noise detected in shut-in and flowing conditions at the bottom part of logging interval caused by formation development by nearby wells and it is not related to annulus pressure sources. In this well, a segmented bond tool (SBT) was run to test cement integrity. This tool found no cement in some areas and only poor cement in other intervals between Zone B and the surface. The 9 5/8″ casing was perforated above the leak and squeezed with cement and the leak cured.
September, 2015