Use of Novel Self-Healing Materials to Control Sustained Casing Pressure and Prevent Long Term Environmental Impact

Abstract

PDO is the biggest Oil and Gas Producer in Oman drilling in several fields with a number of drilling and cementing challenges. One of the key challenges that the operator has started to encounter is sustained casing pressure (SCP) because of poor zonal isolation. Hydrocarbons are observed in B or C annuli and lab analysis confirms it is coming from one of the Limestone reservoirs. More than 4 wells that were drilled in 2012 and 2013 have been identified with SCP and others are being monitored. The drilling campaign in this particular field was halted because of SCP problems and failure to comply with government regulations. Expensive work-over operation had to be done to abandon the wells.Owing to the fact that conventional cement systems and practices have proven ineffective, an innovative self-healing cement system was introduced. This system has the property of self-repair when in contact with hydrocarbons, seals any pathways and restores well integrity without any intervention thus providing long term zonal isolation. The system is placed conventionally in the annulus as part of the cement slurry and the healing material stays dormant till the time it sees the hydrocarbons that may flow through the cracks. Subsequently it expands and heals the cracks.The self-healing cement system has been tried in four wells in the same field with excellent results. After more than one year of completion, no gas pressure has been observed in the annulus. The operator has standardized this system for this field for all future wells and plans to extend the use to other fields with similar issues. This paper will cover details on the system, mechanism of work, validation process of the system, operational aspects and field implementation to elaborate how SCP problems can be overcome.

Design and field-scale demonstration of the buoyant-kill process for restoring integrity of wells with sustained casing pressure

“…Preventing SCP requires improvement of cement-sheath quality (Landry et al, 2015) by using specialized cementing techniques providing effective zonal isolation-such as casing expansion (Kupresan et al, 2014), casing patching (Saltel et al, 2015), use of self-healing cement (Khattak et al, 2015;Landry et al, 2015;Shadravan and Amani, 2015), or expandable cement system (Tanoto et al, 2016). Despite the new technology, most wells may still develop SCP so there is a need for advancing the SCP remediation technology.…”