Fracturing Fluid Filtration and Fracturing Energy Efficiency in Unconsolidated Sandstone Reservoirs
Fracturing and packing are the leading techniques used at Bohai Oilfield for sand control and pro-duction improvement.However,the fracturing fluid filtration in high-permeability reservoirs and its impact on fracturing energy efficiency are unknown,resulting in inadequate evidences for deciding candidate wells/formations to be fractured and also for operation optimization.Fracturing fluid filtration experiment with reservoir cores and tri-axial fracturing simulation experiment with unconsolidated sandstone cores were conducted.Based on the fracturing fluid filtration and fracture morphology obtained,the fracturing simulation and energy efficiency evaluation indexes and methods were developed for medium and high-permeability reservoirs,and they were effectively used to evalu-ate the fracture initiation efficiency and fracture extension efficiency under different reservoir conditions at different operating parameters.The results show that,compared to low-permeability reservoirs,highly heterogeneous un-consolidated sandstone reservoirs generate more irregular fractures,including multiple slim branch fractures exten-ding form the main fracture.Through fracturing energy efficiency analysis based on fracturing mechanism and fluid filtration characteristics,the recommended operating parameters at Bohai Oilfield under typical working conditions are obtained as follows:the permeability of reservoir to be fractured/packed should be lower than 2.0~4.0 μm2;the filtration coefficient should be controlled below 0.006 m/min0.5;the fracturing displacement should not be less than 2.0~2.5 m3/min;and the viscosity of fracturing fluid should be kept above 180~200 mPa·s.The conclu-sions can be good guidance for deciding the candidate wells/formations to be fractured/packed and optimizing the operation parameters in medium-to high-permeability reservoirs of Bohai Oilfield.
unconsolidated sandstone reservoirfracturing and packingfracturing fluid filtrationfracture initiation mechanismfracture extensionfracturing energy efficiency