Evaluation of the M-Site B-sand fracture experiments: Evolution of a pressure analysis methodology

The most comprehensive hydraulic-fracturing data including the first object ive measurements of fracture height, length, and width are acquired from th e Gas Research Inst. (GRI)/Dept, of Energy (DOE) Multiwell Site (M-Site) te sts. In spite of the availability of extensive and reliable fracturing data , significant deviation between predicted and microseismic-determined fract ure geometry was reported. The purpose of this study is to provide a consis tent analysis of B-sand experiments by applying a systematic methodology fo r fracture-treatment evaluation. For this analysis, fracture parameters are estimated initially from laborat ory data, well logs, and calibration tests. These parameters are refined by matching simulated pressures to field-measured fracturing pressures record ed during the first linear gel injection. These fracture parameters then ar e used to compare predicted- and measured-fracture pressures on all subsequ ent injections. Although general agreement for the fracturing pressures was obtained, a discrepancy was noticed between zone stresses estimated by eva luation and their variation as indicated on published stress logs. Stress d ata were reinterpreted and an acceptable pressure match was established. Fracture parameters resulting from this study are in agreement with indepen dently inferred estimates. In addition, an apparent difference between clos ure pressure and microfrac stress is resolved. Finally, good agreement betw een predicted fracture geometry and microseismic readings is observed for e ach injection test considered in this study. This study shows that fracture pressures and geometry can be predicted consistently with good accuracy us ing elementary analysis techniques, without a reliance on ad hoc physical e xplanations.