The American Petroleum Institute testing Standard 19-D (2008) is the current industry standard for conductivity testing of proppants used in hydraulic fracturing. Similar to previous standards from both the API and ISO, it continues the practice of measuring a "reference" conductivity obtained under 50-hours of time at a given stress. The fracture design engineer is then left to estimate a damage factor to apply to the long-term design of the well completion.

This study takes three 40/70 mesh proppants commonly used for multi-stage horizontal well slickwater completions in North America and presents 0.5 lb/ft2 test data over 1000-hours of "extended time" at stress and temperature conditions representative of the Bakken formation of North Dakota. Results presented give clear insight to the degree of damage occurring in the reservoir due to time at stress and temperature. To the authors knowledge, there has never been any extended time conductivity data published at proppant concentrations representative of slickwater fracturing - despite the obvious need for this understanding to optimize the performance of unconventional slickwater well stimulation designs.

The API Standard 19-D procedure for conductivity testing was followed for the tests presented in this paper, but with the proppant concentration loaded at 0.5 lb/ft2 to represent a slickwater proppant pack, and all tests run at 250°F regardless of the proppant material type. The extended time test was run for 1000-hours duration for three commonly used 40/70 mesh proppants used in North American Unconventional Slickwater Well Completions: 40/70 mesh mono-crystalline "white" sand (WS), 40/70 mesh multi-crystalline "brown" sand (BS), and 40/70 mesh light weight ceramic (LWC). The results are presented as conductivity curves as a function of time for the period of testing. Logarithmic Conductivity Degradation Factors (LCDF) were calculated for each proppant type. Degradation for all materials is extrapolated to the point of zero residual conductivity, and compared to previous extended term testing for 1# and 2# proppant packs.

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