An Innovative Organophillic Clay-Free Invert Emulsion Fluid OCF-IEF Facilitates the Successful Running of the Longest 6 5/8-in. Liner in the World

Abstract

Abstract To maximize reservoir drainage and production volumes from a field in the United Arab Emirates (UAE), extremely long horizontal sections are necessary through the producing interval. Extended reach drilling (ERD) imposes significant requirements on the drilling operation and complicates the running of the production liner because of the long horizontal displacement. This paper details the design and field execution of an organophillic clay-free invert emulsion fluid (OCF-IEF) that met these ERD requirements and facilitated the longest liner run in the world. Successfully delivering a gauge wellbore with >20,442 ft of open hole at 90° inclination, followed by running and setting a production liner at target depth (TD), was not deemed achievable using a conventional invert emulsion fluid (IEF). A correctly designed fluid system was necessary to deliver success. The necessary fluid properties included a low rheology profile to minimize equivalent circulating density (ECD) to keep within the fracture gradient, long-term fluid stability, minimal formation damage risk, and low solids content to help minimize friction. A calcium-bromide brine-based low-solids OCF IEF was selected to meet these requirements. Through the use of this OCF-IEF system, the operator was able to achieve the well objectives, drilling one of the longest wells in the UAE, reaching a TD of 29,075 ft, including a record-breaking 20,442-ft openhole. The 8 1/2-in. reservoir section was drilled in 37 days, with only three trips necessary to change the bottomhole assembly (BHA). The average rate of penetration (ROP) varied between 70 to 100 ft/hr. The maximum ECD observed did not exceed the fracture gradient at any stage. Consequently, no downhole losses were experienced during the drilling phase. The engineered OCF-IEF achieved a low rheology profile, which minimized the contribution to annular pressure losses. The low rheology profile and low solids content in the IEF resulted in excellent fluid stability with no weighting material SAG. No losses were observed while running the liner, and no indications of tight spots were observed. Friction factors were low (between 0.15 and 0.25), and this facilitated the liner to be run without any issues. Total days on the well were 30 less than planned, which significantly saved both costs and rig time for the operator. The organophillic clays and organophillic lignites are replaced with various organic polymers to achieve different fluid behaviours (Strand et al. 2016). The novel polymer chemistry of this OCF-IEF together with a low solids content (attributed to using calcium-bromide base brine) resulted in desirable fluid properties that allowed the operator to extend limits, reach new depths, and break records to maximize production and increase revenue.