Patent ID: 7534744

Claim:
A drilling fluid comprising a lost circulation additive comprising: about 70 ppb to about 90 ppb resilient carbon-based material and about 2 ppb to about 10 ppb water swellable but not water-soluble crystalline synthetic polymer, wherein the resilient carbon-based material comprises resilient graphitic carbon particles and ungraphitized carbon particles and the quantity of the resilient graphitic carbon particles exceeds the quantity of ungraphitized carbon particles, wherein the resilient carbon-based material has a particle size about 95% larger than 200 mesh and about 100% smaller than 40 mesh, wherein the synthetic polymer comprises a dehydrated crystallized form of cross-linked polyacrylamide that will readily hydrate following exposure to water, and wherein the combination of the resilient carbon-based material and the synthetic polymer is facilitated in the additive with a facilitating amount of glyoxal, such that the blend prevents or alleviates lost circulation to a synergistically greater amount than either the resilient carbon-based material or the synthetic polymer would provide one without the other.