In October 2013 Brunei Shell requested Nautec to carry out an urgent grouting job of the backside of their 13 3/8” casing and 26” conductor at Deep Driller 8 drilling rig in Brunei.
Brunei Shell Petroleum (BSP).
Urgent mobilization of crew; site survey and deck-space survey, down-hole camera inspection of damaged conductor casing; cleaning of annulus; provision of Ultra High Performance Cementitious (UHPC) materials; equipment and man power associated with the surface casing grouting of the damaged conductor; post-grouting inspection; and sampling and testing of UHPC test cubes.
The surface casing of the conductor was in urgent need of repair due to corrosion damage. The repair method applied by a 3rd party was unsuccessful as they failed to get the cement to return to surface after completing the cementing job on the surface casing.
Based on the inspection done by the ROV operation during the circulation at TD after opening up the hole to 17 ½” section, there was evidence of the WBM stream on the seabed, which was suspected of coming from the breach points at the seabed. Conventional oil well cement used with higher water content was not able to seal the leak.
Nautec was requested to mobilize crew, grouting spread and UHPC material urgently on the following day to strengthen and to isolate between the casing and conductor as well as provide structural support integrity between the 13 3/8” casing and conductor.
Due to the self-sealing and fast-curing properties of the UHPC material Nautec managed to successfully pump in the material with good grout overflow from the 26″ conductor casing opening.
The UHPC material is designed as a ready-to-use cement-based dry-blended powder formulation. The addition of a prescribed amount of potable water produces cohesive and flowable non-shrink grouts that develop high early-age strength and are impermeable to water ingress. It is a group of materials which has exceedingly higher durability and compressive strength, as compared with conventional cement-based materials. This is because UHPC is characterised by dense microstructure due to very low water content and use of special chemical additives. On the other hand, conventional cementitious grouts typically with higher water content have more porous paste matrix and weak paste-aggregate interface region. Hence our grout will free fall until it is restrained from dropping further. Due to the low temperature in such water depth, the setting of the grout will be slowed down hence the grout will remain flowable for a longer period of time (by a few more hours at 14 deg C). Therefore it was possible to drop 148m or more since no plug was set based on the calculation of the total material used during the grouting against the total volume. By about 6 to 12 hours, the grout will start to set and eventually stiffen into position after about 24 hours. The job was successfully completed in one day and all crew was demobilized on the following day.