A clay-based or clay-free aqueous thixotropic wellbore fluid having improved fluid loss control, desirable flow characteristics and low shale sensitivity for use in drilling a well comprising water or a brine base including an effective amount of an additive comprising a crosslinked potato starch, a heteropolysaccharide derived from a carbohydrate by bacteria of the genus Xanthomonas, and hydroxyethylcellulose or carboxymethylcellulose, is disclosed. This drilling fluid has been found to be nond...

The water loss properties of well completion and well workover fluids are improved by the addition of an effective amount of at least one adjuvant selected from (1) sodium carbonate with either sodium bicarbonate or an organic polycarboxylic acid or polycarboxylic acid anhydride or (2) sodium bicarbonate alone. In another embodiment, the adjuvants are added to stabilize water loss control agents in wellbore fluids, especially at elevated temperatures.

A method for determining the success of a multiple perforation operation by determining whether all perforations are open comprising providing a fluid loss control composition which carries one or more materials designed to form a filter cake on the wellbore wall, at least one of the filter cake forming materials being radioactively tagged, injecting the fluid loss control composition into the wellbore and into the perforations to build up a filter cake on the wellbore wall behind the perforatio...

A wellbore packer capable of sealing a tubing string within a wellbore casing or wellbore is described.

A new wellbore cutter has been invented which, in certain embodiments has a piston having a fluid flow bore therethrough, at least one stabilizer kick-out member, and at least one cutting blade kick-out member, an outer body through which the piston projects, the outer body movable about the piston, the outer body having at least one stabilizer pivotably mounted thereto, the at least one stabilizer movable out from the outer body upon movement of the outer body with respect to the piston so that...

A method and apparatus for perforating at least one mineral-producing zone in a wellbore wherein a packer and perforating gun assembly is employed which will allow the removal of wellbore liquid initially present in the wellbore adjacent said zone to be removed after the packer and perforating gun assembly has been fixed in the wellbore so that subsequent detonation of said perforating gun is carried out in a liquid which is nondeleterious to said zone.

A fill valve includes a tubular housing which accommodates a valve member which is biased toward a closed position by a light spring. The valve member includes a head and a tubular portion which is provided with two large windows. When the fill valve is open fluid flows freely through the tubular portion of the fill valve and out of the windows.

An overshot for engaging and retrieving a collapsed coiled tubing in a wellbore, has been invented. In one aspect the overshot has a body member with a top, a bottom, and a body channel therethrough from top to bottom, the body member having a slip chamber, at least one slip movably disposed in the slip chamber of the body member, and movable on at least one inclined rail in the slip chamber so that, upon contacting the collapsed coiled tubing, upward movement of the body member results in downw...

A new fill valve for use in cementing operations in a wellbore extending down into the earth has been invented, the fill valve having a tubular housing having a valve seat, a valve member slidably mounted in said tubular housing, a spring for biasing said valve member towards a closed position, the valve member having a head engageable with the valve seat of the tubular housing to close the valve, selectively releasable apparatus for releasably maintaining the fill valve in an open position, the...

A unitary pipe loop component for use with a sinker bar and a pair of pipes in a wellbore includes a return bend pipe fitting having a fluid flow passage configured to extend between the pipes in the wellbore, and further includes a sleeve having a passage with open opposite ends to receive the sinker bar through the sleeve. A weight suspension structure is connected to the sleeve and the pipe fitting as another distinct portion of the unitary pipe loop component, and has a knockout portion conf...