Oil-based drilling packer fluids contain organophilic clays - having defined alkyl gps. as gelling agents

摘要

Oil-based drilling fluids contain as gelling agent 1-50 lb/barrel of an organophilic clay (I). (I) is made by reacting a smectite clay (II) (pref. hectorite or Na bentonite) with a quaternary ammonium or phosphonium ion R1R2R3R4X(+) (III), where R1 is C6 or lower beta, gamma unsatd. alkyl and/or C2-C6 hydroxyalkyl, R2 is C8-C60 alkyl, R3 and R4 are as specified for R1 or aralkyl or C1-C22 alkyl or mixts.of these, and X is N or P. Also claimed is a process for lining a borehole by pumping such a fluid into an annular space in the hole and allowing it to gel. The oil base is pref. diesel oil. (II) has a cation exchange capacity of at least 75 milliequivalents per 100 g, and 90-140 milliequivalents of (III) are added per 100 g of (II). Where the fluid is for use as a sealant (''packer fluid''), the pref. concn. of (I) is 6-50 lb/barrel. Gel formation is effectively complete after mixing in (I) at low shear force.