Study On Performance Of Multi-layered Fracturing Vertical Well With Analytical-numerical Hybrid Model Considering Variable Fracture Conductivity

Tight oil reservoir is characterized by many layers,tight and thin hydrocarbon bearing strata and strong inter-layer heterogeneity.Conventional methods are not satisfactory for the development of unconventional oil reservoirs.It is imperative to launch multi-layered fracturing method.At present,there are many studies on productivity models of multi-layered fracturing vertical wells,but most of them do not consider the dual change of conductivity with time and space.Laboratory experiments and field practice show that the conductivity of fractures is not constant during the production process.The model established in this paper has certain guiding significance for related theoretical research and practical production.In this paper,the source function method is used to solve the reservoir seepage model,and the finite difference method is used to solve the finite conductivity fracture flow model with variable conductivity.By combining the pressure and flow continuity of reservoir and fracture interface,the semi-analytical productivity model of multi-layered fracturing vertical wells with variable diversion capacity considering time and space variations is obtained.Then,the sensitivity analysis is obtained.These are also the focus of this article.Results: the increase of fracture half-length and fracture conductivity,the production of the vertical fracture well is also increased,however,when the conductivity increases to a certain value,the production increase is not obvious and there is an optimal solution.The larger the difference is,the lower the production is,and the faster the daily production decreases.When the total fracture length of the model and the reservoir permeability are the same,the combined production of “long fracture length + high permeability reservoir”is higher;the ratio of formation coefficient,fracture half-length of crack and increase of fracture conductivity increase the multi-layered production ratio.At the beginning of production process,the high permeability layer has a certain inhibitory effect on the low permeability layer,but in the later stage of production,the production contribution rate of each layer is basically kept at a certain value;when comparing the multi-layered fracturing vertical well with analytical-numerical hybrid model considering constant fracture conductivity and variable fracture conductivity,the results show that the influence of the spatial and temporal changes of the fracture conductivity on productivity cannot be ignored.This important factor will change the distribution of reservoir seepage field,and more fluid will flow into the wellbore through the near-wellbore zone.