Hydraulic fracturing, when applied in concert with horizontal drilling, has led to a rejuvenation and revolution in the oil and gas industry that has been felt globally. When once development and reserve addition opportunities in the US were deemed to be very limited now technically recoverable reserves for both oil and gas in the US are viewed as abundant, and long-lived (EIA 2016). Yet hydraulic fracturing itself relies on the placement of proppants and the performance of those proppants to succeed.
The earliest hydraulic fracture stimulations utilized poorly sorted river sand as proppant. Since this first experiment with proppants, the industry has evolved with a broad range of proppant choices although natural sand of some type remains by far the proppant of choice for a variety of reasons. Technology has advanced in many ways since the first fracture stimulation. For the past thirty years, the Stim-Lab Proppant Consortium has engaged in a continuous program of building knowledge and understanding in the behavior of all types of proppants used in hydraulic fracturing.
Arguably no other body of knowledge about proppants exists that compares in extent and detail with that accumulated by the Consortium. There are many basic understandings about the behavior of proppant packs under downhole reservoir conditions that have been developed through thousands of tests that have been performed through the work of the Consortium. These include the effects of proppant type, grain failure, fines migration, embedment, non-Darcy and multi-phase flow, cycling, loading, packing arrangement, fracture fluid damage and others. All of these effects can be at work simultaneously to negatively affect flow in the propped fracture and the recognition of these effects assists to explain observed well performance.
This paper will present basic understandings of proppant performance that are sometimes misunderstood or wrongly applied and will assist the practicing engineer in well diagnostics and stimulation design. It will also present and describe predictive performance models developed for proppants that in turn leads to the most comprehensive simulation of proppant performance under realistic downhole conditions available in the industry.