The Research On Percolation Mechanism And Design For Radial Drilling Technology In Thin Interbed Low Permeability Reservoir

Radial drilling technology is one of the effective means for the development of thin interbed low permeability reservoir which is cheap and benefits good.At present,percolation mechanism for enhanced recovery efficiency by radial drilling technology is not clear,and the design method of adaptation well network needs to be improved.Both of them restrict the effective application for this technology.Therefore,it is necessary to make a further study.In this paper,microscopic waterflooding experiment is used to analysis the effect in four types of radial drilling technology firstly,and the seepage mechanism of it is clarified;Then,use the theory of potential superimposition,conformal transformation method and mirror reflection method to derive a formula for productivity of multi-branch radial drilling technology in plane and vertical,and the influencing factors of productivity are analyzed.Finally,the methods including the number of perforations,the position of the perforations,and the penetration ratio are optimized by numerical simulation calculations.The methods are applied in H block of Shengli oilfield which is thin interbed low permeability reservoir.The results show that radial drilling technology can transform radial flow into linear flow,increase the pressure gradient between wells,and enhance oil recovery by 18%.It can also make the pressure head go forward and establish the displacement,hence get a 12% higher recovery.Furthermore,the heterogeneity of the formation can be adjusted to improve the balance of vertical displacement and improve oil recovery by 25%.In the end,the streamline can be converted to adapt to the well pattern,thus enhancing oil recovery by 28%.The productivity of radial drilling technology increases as the number,length and radius of holes increase.The number and length have great influence on productivity.Generally,there are no more than 4 holes in the plane.The reservoir thickness of single hole can be decreased with the increase of permeability.The orientations of holes are determined according to the different conditions such as heterogeneous flooding,appropriating remaining oil and different time pruducing.The hole penetration ratio is designed according to the four types of radial drilling technology.12 oil wells and 4 water wells are transformed by radial drilling technology through numerical simulation in H block of Shengli oilfield.The result shows that the adjustment scheme enhances oil recovery by 2.1%,which effectively improved the development effect of the well field.