Fracturing Technology Research In Shale Gas Formation

This paper studied the effect of fractures,proppant settings and embedment to shale gas production through experimental and numerical simulation.Taking well S_D1 as an example,it illustrated the influence of different parameters to hydraulic fracturing and shale gas production through formation evaluation,fracturing parameters optimization,treatment procedures design,field testing and post-fracturing evaluation.Increase stimulated formation volume is an effective means to gain sound production performance for shale gas reservoirs.Brittleness,quarts and carbonate content,is main factor to form net fractures which is a prerequisite for successful development of shale gas.Fracture density and connectivity among fractures and between fracture and borehole will affect the post-fracturing gas production.The more fractures(fracture density)created under the same simulated reservoir volume(SRV),the more production will be achieved.Although the increased SRV can effectively improve gas production,shale gas well only covers limited control area due to the ultra-limited permeability of shale gas reservoir.Complexity of net fractures in shale gas reservoir would reduce the losses in fracture width and conductivity because longer time shut-in prohibited proppant flow back.Experiment results showed that proppant embedment in shale were much more serious than in sand.Embedment would lead to reduction of fracture width and conductivity in shale formation which would result in lower proppant concentration and larger fracture volume,even cause open hydraulic fracture's closure and turn into in non-propped fractures.Post-fracturing evaluation and inverse analysis indicated that shale formation has abnormally fracture stress gradient,extending gradient and closure gradient.Furthermore,Reasonable flowback control will contribute to desorption in shale gas when dominated by adsorbed gas.