Abstract: A method to be used when performing drilling in a well bore involves positioning a dual bore drill pipe in a well bore. An outer annulus formed between the drill pipe and well bore wall is divided into two different sections. A first fluid is provided in one of the sections. A second fluid having a density less than the first fluid is circulated into and out of the well bore through the drill pipe. The densities of the first and second fluids are such that the drill pipe is at least partly floating in the first fluid in the outer annulus.

Abstract: The present invention regards a method for performing core sampling during drilling of wells, comprising the steps of providing a dual bore drill pipe with drill bit in the end in the well bore, providing means to introduce a drill liquid into an annular space of the drill pipe and return it together with drill cuttings to the surface through centrally arranged return line in the dual bore drill pipe, removing larger cuttings at outlet of return pipe, and perform core testing on these cuttings, knowing where the cuttings come from in the well. The invention also regards a device for performing the invention.

Abstract: The present invention regards a method to be used when performing drilling in a well bore, comprising: positioning a dual bore drill pipe with a tool at on one end into a well bore, thereby forming an outer annulus between the well bore wall and the pipe and two inner bores within the pipe, dividing the outer annulus into two different sections along the longitudinal axis of the drill pipe, at least at one location close to the tool, providing a first fluid in the outer annuls and providing a second fluid within the drill pipe and around the tool, and a device.