Abstract

This paper investigates the feasibility of using Titanium coiled tubing as an alternative to conventional steel coiled tubing for established operations in the North Sea. The criteria set is that both should be capable of performing the same work scope.

Within the North Sea many mature fields are serviced from platforms whose structures are being downrated in-so-far as deck load bearing and crane lifting capability is concerned. This imposes severe limitations as to the length or weight of steel coiled tubing that can be lifted onto and manoeuvered on board some platforms. Titanium alloys, being lighter than steel, give a potential solution to this problem in that they have a lower density and greater yield strength allowing thinner wall thickness to be used.

A direct comparison has been made between Titanium coiled tubing and steel coiled tubing in order to ascertain whether well entry capability is similar. While Titanium undoubtedly offers many benefits to those of steel coiled tubing there remains some uncertainty over Titanium's horizontal reach capability due to its' lower Young's Modulus. Three wells (Example A, B & C) have been used to evaluate the ability of coil made with these two materials. These wells were part of a campaign of work carried out in 1996. The steel coiled tubing data and tubing force analysis predictions are thus real data, only the Titanium coiled tubing values are simulated. The coiled tubing prediction model was validated with steel coiled tubing during the job and therefore the model is the common link between the known and hypothetical values.

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