Pressure Decline Analysis After Horizontal Well Multi-stage Fracturing

With more and more using horizontal well to explore oil and gas field, to enhance theproduction capacity of horizontal wells, there are more and more fracturing to horizontal wells.And horizontal wells often require fracturing several hydraulic fractures to increase oil and gasflow channel. Therefore, it needs a diagnostic technique for several hydraulic fractures inhorizontal wells after being fracturing, to analyze and evaluate the effect of fracturing.But so far, the existing models of frac pressure decline analysis are for a single hydraulicfracture, there is not a theoretical model be aimed at horizontal wells which have severalhydraulic fractures at the moment. Because of big difference in characteristics of fluid flowbetween a single hydraulic fracture in vertical well and several hydraulic fractures inhorizontal well when those hydraulic fractures are closing, so we can not directly copy theprevious related technologies.In this dissertation I considered that the change in pressure when several hydraulicfractures in horizontal well being closing is different from one single hydraulic fracture beingclosing, and analysed the reason of G function method which often be fit for one singlehydraulic fracture cannot be applied to several hydraulic fractures in horizontal well. It carriedout a more detailed process analysis in fracture forced closure and fracture natural closureafter horizontal well being fractured several hydraulic fractures. It has considered thedistinguishing feature of change in pressure when all fractures in horizontal well being closingover the same time, and consider pressure loss of fluid flowing back through horizontal well infracture forced closure, and considered the distinguishing feature of filtration of fracturingfluid in several hydraulic fractures in one horizontal well, it established the material balanceequation of fluid in the several hydraulic fractures after pumping, and the computationalmethod of filtration of fracturing fluid after pumping, and the method of fluid flowing backfrom several hydraulic fractures in fracture forced closure, established the pressure declinemethod for several hydraulic fractures forced closure at the same time, and the interpretationmethod of hydraulic fracture parameters. This paper strives to resolve existing problems ofpressure decline analysis in horizontal well fracturing, and this analysis method can explainsome important fracture parameters, such as the length and the width of each hydraulic fracture, the filtration coefficient, closure pressure and closing time, and the efficiency offracturing fluid.