Investigation of ultra-light weight proppant application in shale fracturing

• A fracture simulator is developed to simulate proppant transport during fracture propagation.
• Experimental fracture conductivity of results three ultra-light weight proppants are included.
• Well productivity is estimated based on fracture conductivity distribution.
• ULWPs increase productivity over sand in 0.1 μD gas reservoirs by increasing propped areas.
• A mixture of ULWP and sand improves both short-term and long-term NPV over pure sand.

Horizontal wells with long propped fractures are needed to maximize productivity for ultra-low permeability shale and tight reservoirs. Conventional slickwater fracturing with sand can produce long fractures, but only the near wellbore region is propped due to fast settling of sand in water. Ultra-light weight proppants (ULWPs) can be used to reduce proppant settling. A comprehensive investigation of ULWP performance in shale reservoirs has been conducted by utilizing fracture conductivity experiments, fracture modeling and reservoir simulation. Based on experimental fracture conductivity measurements, empirical conductivity correlations are developed for the three ULWPs as a function of proppant areal concentration at reservoir confining stress and temperature. A fracturing model is used to predict the proppant concentration distributions during fracturing operations from which conductivity distribution along fractures is estimated. The conductivity distribution is then put into a reservoir simulator to predict gas production from a fractured shale well. Simulation study shows that at the same injection concentration in slickwater, all three ULWPs create more propped area and longer propped distance than sand, but the fracture conductivity is significantly lower. ULWPs have strong productivity advantages over sand in 0.1 μD gas reservoir by creating more propped areas. The productivity advantage of using ULWPs decreases with increasing reservoir permeability and decreasing production time. For 1 year production and 0.1 μD shale reservoirs, the acceptable maximum price is $10/lb for ULW-1, $6/lb for ULW-2, and $2.5/lb for ULW-3. The maximum price increases as production time increases. By adding small amount of ULWPs into sand, both the high conductivity zone at the bottom and low conductivity zone at the upper and deeper zones can be achieved, which benefits both short and long-term production.