Estimating Event Growth From Pumped Fluid Volumes
McKenna, Jonathan P.; Bui, Quynhthy; Abbott, David; Domalakes, Drew
Microseismicity was detected during a hydraulic fracture stimulation of a 36-stage lateral well targeting the Middle Bakken Formation in July, 2011. The objective of this study is primarily to correlate pumped fluid volume with horizontal and vertical microseismic event growth. Second, we devise a methodology for estimating the proppant-filled fracture volume resulting from the hydraulic-fracture stimulation.
The cumulative pumped volume and the perpendicular event distance form the wellbore (both vertical and horizontal) was collected for each microseismic event in the dataset. Vertical and horizontal event distances from the wellbore were plotted as a function of pumped fluid volume.
Analysis of all stages indicates that during the first half of the stage's pump schedule, horizontal and vertical event growth extended outward from the wellbore as a function of pumped slickwater fluid volume; creating a fracture network. This initial fracture network extended along two apparent trends with azimuthal orientations consistent with results from a temporal lineament analysis of the microseismic event trends as well as the two distinct focal mechanisms picked from the first motions in the raw seismic traces. Stress inversion of 24 focal mechanisms reveals the most likely nodal plane solutions that result in present day SHmax measurements, consistent with published values. After the fracture network was established from slickwater injection, cross-linked gel was introduced into the formation, accompanied by the majority of the proppant. This resulted in an increased frequency of microseismicity located close to the wellbore that progressively propagated outward. Correlations between fluid volume pumped and the outward distance from the wellbore allows the possibility to predict the total horizontal and vertical extent of microseismicity from the wellbore. This can be used to estimate the total perpendicular distances of fractured rock for future nearby stimulation treatments.
Since the microseismicity associated with the proppant-laden gel location can be tracked within the formation with time, we modeled the probable propped stimulated rock volume using both a pseudo-deterministic and stochastic discrete fracture modeling approach for this treatment.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013