Research On Control Methods Of Sand And Mud Plugging In Sebei Unconsolidated Sandstone Gas Field

Sebei gas field,located in the eastern qaidam basin,is a typical unconsolidated sandstone gas reservoir.Sebei gas field is characterized by loose cementation,poor lithology,high silt,high porosity and medium permeability.In the development process of Sebei gas field,there are many problems,such as large amount of sand production,water invasion,sand blockage and so on,which seriously affect the efficient development of Sebei gas field.Conventional sand control methods can not effectively prevent the migration of reservoir sand particles and well sand production because of the fine grain size,high mud content and easy water intrusion and sand production of rock.Therefore,for the sustainable and efficient development of Sebei gas field,it is necessary to change the traditional sand control technology,and combine the characteristics of reservoir and development status to find out the mechanism of sand migration and plugging,so as to construct a new long-term sand plugging prevention and control technology.In view of the problems of sand production and sand blockage in the production process of Sebei Gas Field,based on the control status of Sebei Gas Field,this paper analyzes the sand particle migration and blockage mechanism in Sebei Gas Field,and proposes to control the sand particle migration and reduce the risk of sand blockage by changing the surface wettability mechanism of sand particles.The migration and plugging mechanism of sand particles in Sebei gas field is analyzed from two aspects of macroscopic field production data and microscopic pore scale.The macroscopic data show that the internal cause of the sand particles migration blockage in Sebei is mainly the loose rock cementation and the external cause is the intrusion of formation water caused by mining.The results of pore scale microscopic analysis show that the migration of sand particles in the pores of Sebei gas field is mainly caused by the drag force of formation water,and the main factor affecting the drag force and the migration of particles is the surface wettability of the transported particles.According to the mechanism of sand particle migration and clogging,the simulation experiment of sand particle surface wettability modification and sand particle migration and clogging prevention and control was carried out.The experimental results show that the best modification effect can be achieved when 0.6%(w/w)GA60 reacts with formation mud and sand particles for 24 h,and the better modification effect can still be maintained when the temperature is 30-90℃and the simulated formation water scour for 72 h.When the ratio of median particle size of gravel layer to median particle size of formation sand is 5.9:1,the sand retaining effect and plugging situation are relatively well.Although the wettability of gravel layer has no significant effect on the migration clogging degree of sand particles,the wettability of formation sand has a great influence on the migration clogging behavior of sand particles.The more hydrophobic the formation sand is,the smaller the permeability damage rate is.The larger the displacement rate is,the more serious the migration and blockage of sand particles will be.However,with the increase of displacement time,some previously blocked pores may be burst open.In this paper,the water resistance of hydrophobic gravel layer is numerically simulated.The results show that to attain a certain hydrophobic layer of gravel block water effect,must meet the d_g<50μm、Φ<0.35、θ>150°、ΔP<1 MPa.The results of this study can provide a new idea and method reference for the prevention and control technology of sand particle migration blockage in unconsolidated sandstone gas field.