Patent ID: 9470053
Filing Date: 2016-10-18
CPC Classification: E21B

Claim Text:
1. A method to be used when performing drilling in a well bore, comprising: positioning in the well bore a drill string comprising at least two pipe conduits, an upper end, and a lower end coupled to a drilling tool, thereby forming an outer annulus between the well bore wall and the drill string; drilling at least one fluid trap in a section of the well bore; feeding a first fluid with a first density into a portion of the outer annulus uphole of the fluid trap; and circulating a second fluid with a second density through the drill string and around the drilling tool; wherein the first density is larger than the second density and a fluid interface is formed between the first fluid and the second fluid in a portion of the outer annulus downhole of the fluid trap; wherein the first and second densities are selected such that a combined weight of the second fluid and the drill string for a volume unit is less than a weight of the first fluid for the same volume unit, allowing the drill string to be buoyant in the first fluid in the outer annulus.