System for depth measurement in a wellbore using composite coiled tubing

An elongate spoolable composite coiled tubing for running downhole equipment in a wellbore, wherein said tubing has peripheral walls and means within said peripheral walls cooperating with a depth measuring device to measure the depth of the spoolable longitudinal composite coiled tubing within the wellbore and thus the depth of the downhole equipment in the borehole and for determining changes in the tubing due to load deformation, said composite coiled tubing comprising;

• a plurality of overlying adjacent layers of fibers arranged in a generally cylindrical shape to form the peripheral walls of said composite coiled tubing, wherein each layer has a plurality of fibers arranged in at least one predetermined orientation so that said composite coiled tubing is provided with sufficient strength to be pushed into and pulled out of a wellbore;
• a plurality of detectable portions overlying at least one of said layers of fibers and spaced apart along the length thereof at a common predetermined distance for the depth detecting device to detect and count as the composite coiled tubing is raised and lowered in the borehole;
• at least one protective fiber layer overlying said first recited at least one of said layers of fiber and said detectable portions;
• and
• a resin uniformly distributed throughout all the fiber layers and consolidated to form a matrix for fixing the fibers in the layers in their predetermined orientations and fusing the layers of fibers and detectable portions together so that the at least one of said layers on which the detectable portions are overlying and the protective fiber layer overlying said first recited at least one of said layers of fiber and said detectable portions are all bonded together in a unified matrix which fixes the fibers and detectable portions in their respective orientations and prevents fracture and delamination points.