Coiled Tubing String Design in Extended Reach Shale Wells

Abstract

Abstract Horizontal shale wells’ drilling has been challenging the technical limits since its beginning, and the same challenge was faced in completion phase with the Plug&Perf method. Vaca Muerta shale play in Argentina is not an exception of this. Lateral lengths in Vaca Muerta achieved 800-1000 m in the beginning of its shale operations with horizontal wells, and now they are designed to achieve more than 2500 m, even 3200 m, similar to the major laterals in the main shale plays of USA and Canada. In Plug&Perf completion method, new materials for fracture plugs and advanced designs of perforating guns were also influenced by the technological advances of the industry. Coiled Tubing (CT) was not an exception of this trend. CT strings for milling out plugs have been demanded to achieve longer laterals without loosing efficiency, with the required Weight on Bit (WOB). Two main aspects must be taken into account for CT string design: Lateral reach with enough WOB depends mainly on geometrical aspects (external diameter and combination of different wall thicknesses) in order to minimize the occurance of buckling by decreasing the friction caused by the contact of the string with casing wall.Extended fatigue life In this way, a new technology in CT manufacture was developed and patented, and introduced by the first time in the market in 2005 (R. Rolovic. M. Valdez et al, 2017). This technology employs materials with a new chemistry, and involves a heat treatment for achieving a complete microstructure transformation and homogeneous properties all along the string. Hence, bias weld, heat affected zone and longitudinal seam weld. Field performance of this new technology in CT has gone beyond the experience achieved with conventional CT. Furthermore, testing of several strings after being removed from the field have shown a superior residual fatigue life than conventional strings, confirming the stated conclusions and pevious observations.