This paper discusses the re-engineering of a fracturing design targeting tight oil in horizontal wells drilled in the Pennsylvanian-age Tonkawa sandstones, located in Dewey County, Oklahoma, through the integration of laboratory, geological, petrophysical, fracture simulation, and diagnostic fracture injection test (DFIT) analysis.
Laboratory testing, which included thin section and scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury injection capillary pressure (MICP) analyses, was conducted to determine mineralogy, nature of the pore body geometry, and potential damage mechanisms. Fracturing fluid chemistry was tested and optimized using both cuttings and core plugs from representative reservoir rock.
Geomechanical rock properties derived from advanced petrophysical analysis of newly acquired high-definition triple combo and full wave sonic logs were combined with geological parameters and potential treating schedules to develop sophisticated fracture simulation models. These models were then refined with in-situ reservoir data obtained from DFIT analyses conducted using downhole gauges to derive the final fracturing treatment design.
The integration of all available data allowed moving away from a “one-size-fits-all” fracture design to one tailored specifically to the targeted reservoir rock. The net result was an optimized fracture design that helped reduce both cost and formation damage, thus improving flowback, long-term productivity, and profitability from these tight sandstones.
A similar fracturing design process is being developed for other tight sandstone reservoirs in the Anadarko basin, with preliminary results confirming that each formation requires a unique fracturing treatment design to be effective.