Providing a conduit for an instrumentation line

#The present invention relates to deep wells, which are drilled into the ground for extraction of fluid or gaseous materials. The invention particularly relates to oil, gas or hydrocarbon wells. Most particularly, the invention relates to means for providing instrumentation in the depths of an oil, gas or production well.

#In drilling an oil well, it is customary to commence with a wellhead, which provides a steel surface casing, generally around 46 cm (18 plus inches) in diameter. As drilling proceeds, successive sections of a steel intermediate casing are inserted, stage by stage, into the well bore, set in place with concrete slurry, and residual, set, internal concrete slurry plugs drilled out to continue the well bore down until a production zone, where hydrocarbon is found to be present in extractable quantities, is reached. Once contact has been made with the production zone, production tubing, of smaller diameter than the intermediate casing, is introduced down to the production zone, ready to extract hydrocarbon. A perforated production liner, intermediate in diameter (around 18 cm, otherwise 7″ or smaller) between that of the production tubing and that of the intermediate casing, may be extended beyond the end of the intermediate casing and the production tubing, allowing ingress of hydrocarbon into the production liner. The production liner allows hydrocarbon to flow into the production tubing but the intermediate casing is plugged, or sealed using a packer, against ingress of hydrocarbon from the production liner.

#Fibre optic sensor line has been used, for some years, in the oil industry, to collect data from oil wells. The data collected primarily relates to temperature. Techniques exist whereby transmitted and backscattered light in a fibre optic line can be analysed to extract much useful information. Such techniques are not part of this invention. The instant invention is concerned, rather, with the introduction of a fibre optic line into an oil well.

#FIG. 1A is a cross sectional schematic view, with shortened vertical scale, of an oil well incorporating the present invention, illustrating the manner in which a control line can be conducted into and down the hydrocarbon well using the primary and secondary members of the invention.

#FIG. 1B is a similar diagram, and shows another embodiment of the invention where the control line can be conducted down the hydrocarbon well, around in a loop and back out of a hydrocarbon well using the primary and secondary members of the present invention.

#FIG. 2 is a cutaway view, in greater detail, of the primary member of the present invention, installed within an intermediate casing.

#Attention is first drawn to FIG. 1A, showing a hydrocarbon well, in the form of an oil well incorporating the present invention.

#A wellhead 10 is set into a well bore 12 and provides support, control and registration for further operations in a manner well known in the art. The well bore 12 descends, through the surrounding rock 13 to a zone of interest 15 wherefrom hydrocarbon is to be extracted. Intermediate casing 14 is then lowered into the well bore 12 with at least one or more parallel, adjacent, lines of control line 16 attached to the outer surface thereof. In this example a single conduit, in the form of a single control line 16 line is shown. The primary member 18 of the present invention is attached to the lower end of the intermediate casing 14 and carries the single control line 16 from a fibre optic connection module 19 to primary coupling 20 on the primary member. The primary member is hollow, allowing cement 21 slurry to be pumped into the intermediate casing 14 and forced up from the bottom of the well bore 12 between the intermediate casing 14 and the surrounding rock 13. When the cement 21 has set, the single control line 16 is encased between the steel intermediate casing 14 and the rock 13 surrounding the well bore 12. The primary coupling 20 is protected by a primary coupling protective sleeve 23, a soft metal tube, on the inside of the primary member 18, which prevents slurry 21 or other debris entering the primary coupling 20 and against damage from drilling operations.

#The cement slurry 21 having set, a drill bit is lowered through the primary member and the residual cement plug at the bottom of the well bore 12 is drilled out. Downward drilling continues until a bore of sufficient depth has been achieved to accept the secondary member 22. A tool, on a drilling string, is lowered into the primary member 18, the primary coupling protective sleeve 23 is engaged, and is then removed by being drawn up the well bore 12 with the drilling string. The primary member 18 and the well bore 12 are, at this stage, ready to receive the secondary member 22.