Experimental Study On The Crush Characteristics Of Proppant In Fracture

Hydraulic fracturing is an effective way to enhance unconventional tight reservoir production.However,after fracturing fluid flowback,proppant may reach the strength limit and break under the action of closure pressure,leading to close fracture and reduce its conductivity.Therefore,it is necessary to study the influence of the proppant crush characteristics.In this paper,the effects of proppant type,particle size,concentration,closure pressure and other factors on the fracture characteristics of proppant were studied by laboratory experiments.Based on the true triaxial simulation device indoor,the control variable method and correlation analysis method were used.In the experiments,quartz sand,ceramic and coated-sand were used as proppants,while sandstone,coal rock,shale and granite were selected as the slate to carry out the proppant crush experiment.The results show that:(1)Ceramic proppant can be used in formations with closure pressures between 0and 50MPa.It has the widest range of closure pressures.Quartz sand proppant with closure pressure higher than 25MPa or coated-sand proppant with closure pressure higher than 40MPa are not applicable.(2)Suitable proppant should be selected according to the requirements of cost and productivity.Under the same condition,the proppant with small particle size,low density,high sand concentration and uniform particle size distribution is better.For example,the average particle size of proppant decreased from 727?m to 165?m,and the crushing rate decreased from 55%to 27%.The average particle size of proppant decreased from 349 m to 284 m,when the crushing rate was the same as 28%,but the former was more evenly distributed.(3)Closure pressure and concentration are the main controlling factors of proppant crushing.The proppant crushing is positively correlated with closure pressure,and negatively correlated with concentration.For example,the closure pressure increased from 10MPa to 40MPa,and the crushing rate increased from 10%to 36%.The sand concentration increased from 0.25kg/m~2 to 10kg/m~2,but the crushing rate decreased from 7.5%to 4%.The research results are expected to provide experimental basis for the study on the crush characteristics of proppant in fracture,and have important practical engineering reference value for fracturing design.