| dc.description.abstract | Hydraulic fracturing is necessary for all wells in the unconventional reservoirs in the U.S. to be economically viable. Propped hydraulic fracturing involves pumping huge sums of fluid and proppant, at extremely high pressures and rates, down the wellbore and into the formation. This is done so that after the hydraulic pressure that is holding the fractures open is released, the proppant stays in the fractures and “props” the fractures open. This connects the greatly expanded and newly exposed surface area of the reservoir to the wellbore for hydrocarbon production.
The Austin Chalk formation was one of the first formations to incorporate horizontal drilling in the 1980’s in the U.S., with the original aim to intersect naturally occurring fractures. This study investigated the fracture conductivity of outcrop and downhole cores from the Austin Chalk formation to help improve completion designs. This is of great interest due to the renewed drilling and completion activity occurring in the Austin Chalk formation.
From the results gathered in this study, it was concluded that lower proppant concentration can provide higher fracture conductivity, excluding the unpropped case. These results are due to a partial mono-layer of proppant distribution in the fracture. Although lower proppant concentrations had the higher fracture conductivities starting out, they also decreased the quickest with increasing closure stress. This is from a higher percentage of proppant crushing at lower proppant concentrations and less grains of proppant having to support the same closure stress. Downhole core samples gave slightly higher fracture conductivity values than outcrop samples with similar decline behavior. Outcrop samples can therefore be used as proxies for downhole core samples in determining the lower limit for fracture conductivity. Fracture conductivities of sawcut and fractured samples were nearly identical at a proppant concentration of 0.20lbs/ft^2 but varied at proppant concentrations of 0.10lbs/ft^2 and 0.05lbs/ft2.
This study provides useful information for proppant selection and fracture design in the Austin Chalk formation. | |
