Spacers for OBM cementing


As the largest difference from WBM cementing, the OBM cementing uses oil-based mud which is immiscible with water, inducing a weak bond at the first and the second interfaces. Therefore, oil- based mud attached to the casing and borehole walls must be cleaned up completely before the cementing job. In this regard, it is necessary to add some surfactant into the spacers. Because common surfactants may get foamed and become non-pumpable, only non-foaming surfactant can be used in the weighted spacers.
| Service value
> Features
• It can convert the lipophilicity to hydrophily on the two interfaces during OBM cementing, so that the casing and borehole walls with slurries will have a reliable bond.
• It can be weighted without foams.
• It is highly capable of cleaning with a small dosage.
> Applications
• Common surfactants may get foamed severely and are difficult to pump, while the special spacers have a good pumpability.
• Fluids with common surfactants cannot be weighted, while the special spacers can be weighted up to 2.45g/cm3
> Application example
For an oilfield well in the northwestern China, oil- based mud at 1.88sg was used to drill ahead at the stage of spud 5#. RIH 139.7mm production casing with the usage of 12m3 OBM cementing spacers at 1.93g/cm3. Excellent cementing quality was achieved.

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