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US 6,279,655 B1Granted
Thixotropic materials
AssigneeSchlumberger Technology Corporation
InventorsDemosthenis Georgeou Pafitis, Stephen Nigel Davies, Geoffrey Colin Maitland
Life of this patent
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AssigneeSchlumberger Technology Corporation
InventorsDemosthenis Georgeou Pafitis, Stephen Nigel Davies, Geoffrey Colin Maitland
Estimating the term…
A settable thixotropic material comprises a thixotrope and a settable substance, the material being capable of gelling reversibly in a gelling time of less than 60 seconds. The thixotrope conveniently comprises a fine grained clay, especially smectite clays, e.g. hectorites. It is preferred to use synthetic smectite type clay colloids, and goods results have been obtained with the synthetic clay known as Laponite RDS. The settable material conveniently comprises cement, particularly Portland cement. The thixotropic material finds use generally in oilwell applications, e.g. to plug lost circulation zones, to repair damaged or corroded casing, as grouts, and to limit annular gas migration. The material also finds particular application in techniques for completion of horizontal wells completed with slotted or pre-drilled liners.
A method of placing a plug in a region around a perforate liner in a wellbore, particularly a generally horizontal wellbore, the method comprising the steps of:
A method of forming a plug in a region in a well comprising the step of pumping a volume of settable thixotropic compound, said compound including a prehydrated thixotrope and a settable material and being capable of gelling reversibly via a colloidal mechanism and being capable of substantially reaching its maximum gel strength in a gelling time of less than 60 seconds, said thixotrope comprising a fine grained clay wherein a setting time is substantially longer than the gelling time, into the region, preferably via suitable packer apparatus, said volume being sufficient to displace substantially all other fluids from the region to be plugged.
A method of cementing a casing or pipe in a borehole, comprising the steps of:
A settable thixotropic compound including a prehydrated thixotrope and a settable material and being capable of gelling reversibly via a colloidal mechanism and being capable of substantially reaching its maximum gel strength in a gelling time of less than 60 seconds, said thixotrope comprising a fine grained clay, wherein a setting time is substantially longer than the gelling time.
Dependencies are inferred from the claim text.