BJ Services has succesfully introduced Microblock HT (product coded SL-1) in the Norwegian sector. Below a job review by Per Skadsheim, Senior District Engineer, Norway
BJ’s first job with SL-1, liquid silica, was successfully cemented 29.07.2003. A 9 7/8” x 9 5/8” casing was installed in the HPHT-well 6406/1-2 offshore Norway with the Semi rig Deep Sea Bergen operating for Norsk AGIP. They are drilling this single exploration well, and therefore selected SL-1 to avoid any back-up silica cement on the rig when the have finished their operation.
The casing was set at 3908 mMD RKB in this vertical well. Seabed at 406 mMD RKB. 32 m3 gastight slurry was used to cement from 9 5/8” shoe and up 800 meters in 12 ¼” hole (30% excess). 4 m3 baseoil was pumped ahead as a pre-flush followed by 15 m3 MCS-Spacer, and then the cement.
The SL-1 was easy to handle, just as BA-58L, and was added to the mixwater premix without any problems. Because of the high content of solids in the product, it was agitated just before the job to ensure a correct density of the additive. The cementing fluids where designed for BHST=138 degC, BHCT=105 degC.Reference to the complete case study
Recipe for the 1.95 SG gastight cement (lab report
FP-16LG (Defoamer) 0.20LHK + CD-31L (Dispersant) 3.00LHK + R-15L (HT retarder) 0.80LHK + SL-1 Liquid Silica & Gas Block 26,50LHK (equals 35% silica BWOC) + FL-63L (Fluid Loss control) 2.00LHK + Fresh water 32.40LHK
Slurry Yield: 95.96LHK
The cement was displaced in place with 1.77 SG OBM with the rig pumps at 1.300 lpm, and the top plug bumped according to plan.
SL-1 advantages compared to dryblended silica cement :
* No hazardous premixing of dry silica required onshore.
* No hazardous mixing environment offshore (cmt room)
* Simplified logistics on- and offshore.
* Easier access to “G”-cement than Silica-cement from the boat
pool in Norway.
* Discharge or back-loading of silica-cement not required.
* Reduced risk of cement contamination.
* Guaranteed quality of the cement delivered to boat.
* Guaranteed concentration of silica in the slurry.
* Very important for HPHT-cementing.
* Increased time for pilot testing >> safer operation.
* Do not need to wait on shipping silica-cement to the rig before
cement sample is sent to the lab.
* No problems with ageing of dry blends.
* Reduced cost because no back-up silica-cement is required.
* Simplified operation when Lead is mixed with Class “G” and
Tail with silica.
* Possibility of adjusting concentration of silica in the slurries.
* Gasblock/extender/strength retrogression preventer, all-in-one