Production Decline Analysis Of Multi-layer Fractured Vertical Well In Tight Reservoir

Tight oil reservoirs have low reservoir permeability,and it is difficult for conventional mining methods to meet the requirements of economic development.Fracture network fracturing technology is an effective means to develop such reservoirs.Fracture network fracturing can generate complex fracture networks,improve reservoir properties,and increase reservoir permeability.Multilayer tight oil reservoirs have strong heterogeneity,and there are impermeable interlayers between small layers.After fracturing,the fracture lengths of each layer are different.This difference in fracturing degree will lead to the use of traditional single layer.Fractured well models are not accurate enough to analyze production decline,and can only obtain the average value of multi-layer reservoirs.Therefore,it is particularly important to study the production decline method of multi-layer fracture network fracturing vertical wells,and to obtain the reservoir parameters of each layer.In this paper,the production decline analysis method is researched,and the principles and plate drawing methods of the Arps method,the power function method,the Fetkovich method,the Blasingame method,the Agrawal-Gardner method,the NPI(Normalized Pressure Integral)method and the Transient method are analyzed,and analyze the adaptability and limitations of each method.A mathematical model of unstable seepage in a vertical well fracturing with a multilayer fracture network is established,and the Laplace transform and Stehfest numerical inversion are used to solve the problem,and the production solution is obtained.For the Blasingame production decline analysis method and NPI production decline analysis method of multi-layer fracture network fracturing vertical wells,the production decline analysis is carried out from the perspectives of pressure normalized production and production normalized pressure,avoiding the influence of data dispersion.The typical curve of production decline of Blasingame and the typical curve of NPI production decline of multi-layer fracture network fracturing vertical well are drawn,the flow stages of typical curves are divided,and the curve characteristics of corresponding stages are given.The influences of fracture length,channeling coefficient,permeability ratio of unfractured area and fracture conductivity on the typical Blasingame production decline curve and NPI production decline curve were analyzed,and the Blasingame production decline fitting analysis method and the NPI production decline fitting analysis method for vertical wells with multi-layer fracture network fracturing in tight oil reservoirs are also established.The production performance data of a vertical wells with multi-layer fracture network fracturing in a tight oil reservoir are analyzed,and the theoretical Blasingame curve and NPI curve are drawn using the multi-layer fracture network fracturing vertical well production decline model,and the measured Blasingame curve and NPI curve are fitted.Analysis to obtain reservoir and fracture parameters.The production data is fully utilized to solve the problem that the production is affected by shutting in the well for pressure recovery test,and provides a scientific basis for the interpretation of production data of multi-layer oil reservoirs.