Successfully Delivered Drill-In, Clay-Free Fluid with Innovative Delayed Acid Breaker for the Longest Horizontal Wells in Offshore Abu Dhabi

Abstract

Abstract Extended reach drilling well design is one of the most critical designs to consider for achieving maximum reservoir contact and increasing well production. This paper demonstrates the methodology for delivering an organophillic clay-free, invert emulsion fluid system using calcium bromide in the internal phase, and discusses an innovative breaker package containing an acid responsive surfactant. Results show a significant reduction in metal/metal and metal/formation friction. Furthermore, no change in wettability has been recorded after the formation has been treated with the breaker. Precise quantitative and qualitative testing methods provided milestone results. Phases of design began with API testing, followed by stressing the fluid beyond the normal downstream conditions, then finally using the return permeability apparatus. Testing all fluids against an artificial core, followed by a natural core, gave the operator the projections required to drill such complicated wells. Intelligent software helped to replicate the actual conditions precisely enough to drill and complete these wells with minimum friction, as well as to simulate effective hole-cleaning practices to help enable optimum equivalent circulating density (ECD) management. From planning to execution, valuable observations were recorded. The use of this system resulted in successfully drilling and completing the longest horizontal well in offshore Abu Dhabi. During 2.5 months of drilling and completing time, no critical path time was wasted because of uncertainty or changes to the approved plan. As a result of using non-aqueous fluid, the friction factor was reduced to 0.07. Furthermore, no fluid treatment was necessary to maintain that lubricity beyond the physical properties of the system itself. The unique composition of the delayed acid breaker used in combination with acid responsive surfactant removed any skin or crushed zone around the wellbore. The recorded well producibility was beyond the expectation, and no acidizing was required. For nearly a decade, lubricants associated with water-based fluid types have been engineered, but inver emulsion fluids had not been considered because of their low initial density and issues associated with stimulating the reservoir. This system provides a successfully designed and executed organophillic clay-free, invert emulsion fluid, as well as a state-of-art delayed acid filter cake cleanup package to maximize the return on investment.