Lower Quality Natural Quartz Proppants Result in Significant Conductivity Loss and Reduction in Ultimate Recovery: A Case History

Abstract

Progress in horizontal drilling and hydraulic fracturing techniques allow the oil and gas industry to get the most out of ultra tight, naturally fractured formations and unconventional reservoirs. The increasing price differential between crude oil and natural gas is resulting in unprecedented activity in the Bakken, Eagle Ford, Niobrara, and other oil rich shales. The industry is actively building drilling rigs and the fracturing companies are adding equipment and crews at an escalating rate to keep up with the market growth.These events have placed demands on hydraulic fracturing consumables as never before. Proppant shortages are expected to worsen before additional capacity can begin to offer some relief. Consequently, more and more operating companies are pumping lower quality Natural Quartz Proppant (NQP) in deeper, hotter, and higher closure stress environments, some of which exceed conventional design limits. All this in an effort to maintain completion intervals which are comparable to the accelerated drilling programs.Recent proppant testing indicates significant conductivity reductions over time as it relates to proppants with lower crush strengths when compared to the higher strength Northern Whites. These conductivity variations were identified using a Discrete Fracture Network (DFN) fracture simulation model which indicated substantial reductions in ultimate recovery and productivity over time. The conductivity and modeling results were compared to actual post-fracture analysis data in the Marcellus Shale. This comparison further substantiated the test results.This paper challenges the industry concept that pumping lower quality crush resistant proppants in a shale reservoir will not result in productivity losses. The findings presented in this paper clearly show that creating and retaining fracture conductivity is a prerequisite to achieving high initial productivity, ultimate recovery, and maximizing project economics.

65 Years of Fracturing Experience: The Key to Better Productivity is Not What we Have Learned but What we Have Forgotten and Failed to Utilize!

“…In a paper presented by Syfan and Anderson (2011), six well conditions and proppant selection criteria were identified that influence obtainable conductivity. The six factors include closure stress, temperature, proppant concentration, proppant strength, proppant particle size, and proppant grain shape.…”

“…If nowhere else does size matter, it is in the business of selecting proppant for the long-term productivity of the well at hand (Syfan & Anderson 2011). The adage "bigger is better" is debatably true and is probably more likely.…”

“…Figs. 8 and 9 present a comparison of work referenced in a paper presented bySyfan and Anderson (2011) with the published data of various authors including McGuire and Sikora as a function of fracture penetration and dimensionless conductivity. These figures clearly indicate that as conductivity and penetration increase so does the dimensionless productivity index.…”