While drilling an 8 1/2-incli section of a north Kuwait producer well, severe mud losses were encountered. Hence, it was decided to design a light weight cement for the 7-inch liner section to avoid further losses while pumping the slurry. The main objective was to achieve a hydraulic isolation to avoid any heavy remedial intervention and potential dump flood behind the liner from the high-pressure Lower Burgan (LB) to Shuaiba.
Full suite of well integrity logs were ran to properly assess whether enough hydraulic isolation was in place. To evaluate the bonding quality of the cement, two independent measurements were carried out across the 7-inch liner with the ultrasonic and sonic bond logs. A subsequent temperature survey was recorded to determine any geothermal anomaly, which could be indicative of fluid movement behind the casing. Finally, oxygen activation stations were conducted based on the cement log and temperature surveys to assure no water movement behind the casing.
The ultrasonic and sonic bond log measurements showed an acceptable bond quality generally. However, the top part of Shuaiba formation up to LB exhibited relatively lower bond quality. The subsequent temperature and oxygen activation logs indicated that the zonal hydraulic isolation was achieved by showing no water movement behind the 7-inch liner. The two complementary surveys helped to take the proper forward decision for this well to go ahead with the planned perforation without cement remedial squeeze, since enough hydraulic isolation was proved to be in place behind the 7-inch liner. Additionally, this saved the rig utilization time and cost by avoiding unnecessary remedial operation. This is usually a heavy-duty operation, which takes time and induces holes in the casing that should be avoided, knowing this type of operation only provides a very marginal gain in terms of isolation. Furthermore, the well is currently producing at 0% water cut after completion.
The proper cement design using light weight cement and optimized casing-landing plan were crucial to achieve good cement placement against formation. The use of the right well integrity approach helped to confirm that effective hydraulic isolation was achieved. Hence all these efforts resulted in the saved rig utilization time and cost by avoiding unnecessary squeeze intervention.