System for preventing hydrate plug formation in gas wells

Abstract

A modification is provided in an assembly for use in an offshore well test string during oil or gas tests on exploration wells. The well has a well bore and a test string with a subsea test tree located in the vicinity of the subsea blowout preventor at the sea floor. The modified assembly includes at least one line having one end in communication with a supply of methanol and the other end in communication with the test string below the sea floor. The line is substantially parallel to the test string and includes the following combination: upper and lower external tubing protectors mechanically associated with the external tubing and the production string; internal porting of selected sections of the subsea test tree, thereby not interrupting the functional use of any component; a pin and box connector detachably connecting the upper external tubing to the upper internal portion; and a lower methanol injection check valve disposed below the sea floor for admitting methanol into the test string while providing a bubble-tight seal against well fluids. A method is thus disclosed of preventing hydrate plug formation in production testing of oil and gas wells by injecting methanol into the test string of the well at any desired depth at an injection rate of at least 1.0 g pm.

Dependencies are inferred from the claim text.