Abstract: The crosslinking of galactomannan gum fracturing fluids by borate ion is delayed for high-temperature applications by encapsulating the boron with a polymer coating. The crosslink-delay time is further adjusted by varying the concentration of an organic polyol. The polyol also acts as a stabilizer for the crosslinked fluid at elevated temperatures. Low pumping friction pressures are achieved by the delay in the crosslinking with the boron available at high temperatures to add high temperature stability to the fracturing fluid at temperatures ranging up to about 350.degree. F.

Abstract: A tubular connector for connecting a drilling tool assembly to a drill string for use in CTD operations. The connector has a fluid flow passage therethrough, and comprises: a first part connected to the drill string and a second part connected to the drilling tool assembly; inter engaging formations such as splines provided on the first and second parts such that, when engaged, the formations do not prevent relative axial movement of the first and second parts but prevent relative rotation thereof; a threaded collar provided around adjacent end portions of the first and second parts for axial location thereof when connected. The connector can also include a non-return valve assembly located in the fluid flow passage; a pressure actuated piston device in the fluid flow passage for disconnecting the drilling tool assembly from the chill string; and a pressure actuated valve which, when operated, allows fluid communication between the fluid flow passage and an exterior region of the connector.