Summary
Microseismicity can be used as a diagnostic tool to characterize the nature of the hydraulic fracture stimulation associated with different completion styles and determine which style most effectively stimulates the targeted zone. We coupled a proppant-filled Discrete Facture Network (DFN) model with treatment information (slurry volume and proppant concentration) to compare fracture growth and proppant distribution in two wells targeting the Niobrara Formation in order to evaluate which treatment parameters had been the most effective.
Introduction
Microseismicity from two wells (Well PP and SS) targeting the Niobrara formation were analyzed to compare and contrast plug and perf versus sliding sleeve completion techniques. Differences in total pumped slurry volumes (93%) and treating pressures (88%) between wells were small. Well PP was completed with thirty-two plug and perf stages. Microseismicity exhibited tight, long trends that continue to increase in length while pumping. Vertical distribution is skewed downward. Microseismic activity is relatively constant throughout the treatment. Well SS was treated with twenty-seven sliding-sleeve stages. Microseismicity showed broad, short trends. Vertical distribution is symmetric about the wellbore. Microseismic activity tends to decrease as treatment progresses.
Discrete Fracture Network Model
The seismic moment ??0, given by equation 1:
??0 = ??µ d (1)
(where ?? is area of the slip plane, µ is shear modulus, and d is average displacement along the slip plane) is a fundamental equation that relates seismic source parameters to actual measured variables (Kanamori, 1977). McGarr (1976) related total detected seismicity to injected volumes assuming that the change in volume is completely accommodated by the seismic failure using the equation
S ??0 = ?? µ| ? ?? | (2)
where ?? is a scaling factor ranging from 0 to 1 which could account for fluid leaking off into the formation and undetected seismicity and ?? is the change in volume due to ground deformations.
