Shale Frac Designs Move to Just-Good-Enough Proppant Economics

Abstract

Selecting appropriate proppants is an important part of hydraulic fracture completion design. Proppant selection choices have dramatically increased in recent years as regional sands have become the proppant of choice in many liquid-rich shale plays. But are these new proppants the best long-term choices to maximize production? Do they provide the best well economics? The paper presents a brief historical perspective on proppant selection followed by various detailed studies of how different proppant types have been performing in various unconventional basins (Williston, Permian, Eagle Ford, Powder River and DJ) along with economic analyses. As the shale revolution pushed into lower-quality reservoirs, the concept of dimensionless conductivity has pushed our industry to use ever lower-quality materials – away from ceramics and resin-coated proppant to white sand in some Rocky Mountain plays and more recently from white sand to regional sand in the Permian and Eagle Ford plays. Further, we compare early-to late-time production response and economics in liquid-rich wells where proppant type changed. The performance of various proppant types and mesh sizes is evaluated using a combination of different techniques, including big data multi-variate statistics, lab conductivity testing, detailed fracture and reservoir modeling, as well as direct well group comparisons. The results of these techniques are then combined with economic analyses to provide a perspective on proppant selection criteria. The comparisons are anchored to permeability estimates from production history matching and DFITs and thousands of wellsite proppant conductivity tests to determine dimensionless conductivity estimates that best approach what is obtained in the field. Proppant selection is typically based on crush resistance to stress loading and fracture conductivity under various flow conditions while having the lowest possible cost. However, dimensionless fracture conductivity is the main driver of well performance as it relates to proppant selection since it includes the relationship of fracture conductivity provided by the proppant relative to the actual flow capacity of the rock (the product of permeability and effective fracture length), which is supported by the production analyses in the paper. The paper shows how much fracture conductivity is adequate for a given effective fracture length and reservoir permeability and then looks at the economics of achieving this "just-good -enough" target conductivity, either through less proppant mass with higher-cost proppants or more proppant mass with-lower cost proppants, as well as mesh size considerations. This paper does not rely on a single technique for proppant selection but uses a combination of various data sources, analysis techniques and economic criteria to provide a more holistic approach to proppant selection.

Effect of Proppant Damages on Fracture Conductivity and Long-Term Recovery in Shale Gas Reservoirs

“…10 However, these advantages come at a higher cost. 11 The expense of the propping agent alone could cost 39% of the well stimulation market. 12 Therefore, cost is also an important factor in proppant selection.…”

“…The permeability of the packed ceramic proppant is typically higher than sand–typed proppant and can maintain high conductivity even under high closure stress . However, these advantages come at a higher cost . The expense of the propping agent alone could cost 39% of the well stimulation market .…”