Study On Artiifcial Fracture Initiation And Propagation Mechanism Of Natural Fractured Reservoir

The oil and gas resources of the low permeability reservoir are one of the most importantorigins in stimulating. However, the reservoir which develops complex natural fracturealways present fractured reservoir, No doubt the hydraulic fracturing was affect badly.Therefore, study on hydraulic fracturing mechanism of the fractured reservoir is positiveeffect on stimulation and the benign development of the Oil Industry.The fractured tuff reservoir in Hai-Laer basin was select as data source. Research onthree Aspects:1.distribution regularity of fracture,2.the relationship between reservoircharacteristic parameters and fractal dimension of fracture system,3.the Simulationtechnology of Reservoir characteristic parameters distribution.The initiation mechanism of fractures was studied. The structural plane intensity theoryis applied to analysis shear fracture along natural fractures, Mechanics balance conditions isapplied to analysis tensional fracture along natural fractures, Plural function method is appliedto analysis natural fracture system collection. The calculation models for hydraulic fracturinginitiation pressure were established. The identification methods for initiation pressure whichestimate hydraulic fracturing initiation mode were obtained. A field case verified that thesemodels can predict the fracture pressure of naturally fractured reservoir.The propagation mechanism of fractures was studied. Based on the natural fracturegeometric distribution and the stress status of encounter place between artificial fracture andnatural fracture, limit stress of rock burst and limit stress of tensional fracture along naturalfractures were estimated. The natural fracture whether can be break through or not can beestimated, according to the D-value of two stresses. Accuracy of judgment function wasproofed by hydraulic fracturing experiment. Complex variables and conformal mapping areapplied to compute stress intensity factor of “cross” crack (one of the most commonintersection forms between artificial fracture and natural fracture). Based on K court evidenceand stress intensity factor, the calculation model of extension pressure was build. Thiscalculation model can be used to assess the influence of the natural fracture on extensionpressure.The study has important realistic significance and certain practical value in conductinghydraulic fracturing on the fractured reservoir.