Optimization Of Production Schedule For Tight Oil Reserviors

With the rapid increase in the demand for oil and gas resources and the maturity of various technologies in the unconventional resources,unconventional oil and gas resources have gradually become the top priority in various countries,and their status in the energy pattern has gradually exceeded that of conventional resources.Furthermore,tight oil is an important part of unconventional resources.Pressure depletion development scheme is mainly carried out by multistage fracturing horizontal well technology,which is also a common method to develop tight reservoirs.However,the research on the reasonable production schedule of tight reservoirs needs to be further deepened.How to use pressure system efficiently to achieve the optimal development effect is still the key problem in the development of tight reservoirs.Based on investigating the literature of tight oil reservoir capacity and the production schedule,considering the particularity of tight reservoirs: nonlinear flow,complex fracture network composed of natural and artificial fractures,stress-sensitivity effect and fracture closure during the reservoir development process,the whole reservoir can be divided into three regions: stimulated zone,unstimulated zone and the primary fracture area.In particular,it's necessary to take the change of fracture permeability and width into consideration on the processing of the fracture closure at the same time.After that,the corresponding mathematical model is established.Based on this model,the reasonable production pressure drop is analyzed and the impressions of threshold pressure gradient,stress sensitivity effect and fracture closure on reservoir productivity and reasonable production pressure drop are analyzed.Fracture closure coefficient is defined to better describe the phenomenon of fracture closure.Then the pressure depletion scheme is analyzed and studied,and the effects of different pressure depletion speeds under linear pressure decline depletion and step-wise pressure decline depletion are analyzed.Besides,and the two modes are compared.Finally,a multi-stage splitting optimization method is proposed.Based on the multi-stage splitting method,mathematical model and intelligent optimization algorithm are combined to establish the optimization model of production schedule,then the optimal production schedule is obtained after optimization.The results show that the improved mathematical model fits well with the oil field,and the study on reasonable production pressure drop shows that the stress sensitivity coefficient and fracture closure coefficient have significant influence on the determination of reasonable production pressure drop then the reasonable bottom hole flow pressure design chart is drawn by single factor analysis.The study of pressure depletion scheme illustrates that the reservoir development effect is obviously different under different pressure decline speed,the optimal pressure decline speed is related to the reservoir physical property,and the linear pressure decline depletion is slightly better than the step-wise pressure decline depletion.In the study of production schedule optimization,the multi-stage splitting method is used to obtain the optimal control frequency and control value of the pressure system under optimal splitting parameters.