Challenges and Solutions for Qualifying Proppants for Deepwater Wells

摘要

Gulf of Mexico Continental Shelf and Deepwater formations represent a harsh environment which causes difficulty predicting operational requirements for proppants using traditional methods.Common forma-tion conditions are very high closure stresses approaching 20,000 psi and temperatures varying from 220°F and upwards,nearing 500°F,such as in the Lower Wilcox Formation on the continental shelf. Deepwater wells present economic investment for investors several orders of magnitude larger than onshore conventional and unconventional plays common in current land assets.Operators therefore place a great deal of focus on the design of the frac pack,completion tools,production and field development. Required qualification and understanding of proppant performance at these conditions far exceeds that needed for today’s extensive shale market. Understanding the proppant behavior that brings economic value to these applications is difficult as current API/ISO performance measurements do not apply under these extreme conditions.Measurement artifacts due to limitations in laboratory materials,highly integrated measurement environment,apparatus limitation or statistical variability in proppant performance are common.New proposed protocol indi-vidually examines loss mechanism as a function of mechanical,thermal and chemical forces at high-temperature and high-pressure conditions.Integration of these proposed protocols with conventional testing allows better understanding of root causes of proppant performance losses. Laboratory measurements of proppants permit defining a boundary that separates stable,predictable performance from variable,unreliable performance.Closure stress,temperature,and several degradation mechanisms,such as cyclic stress and corrosion attack,influence the position of this boundary with respect to the mechanical strength of the proppant.Results show that commercially available high strength proppants exhibit a statistically proven variable performance when used under high-temperature,high-pressure conductions common to Deepwater conditions. Employing materials operating within a predictable performance regime is both an engineering and economic design decision for any fracturing application.Through independent evaluation of the mechan-ical,thermal,and chemical forces acting upon materials in the application,optimized solutions are possible that permit extracting value and stable performance from the well.