Research On The Design Method Of SAGD Well Steam Injection Valve

SAGD horizontal well technology has been widely used in the field of heavy oil exploitation due to its high utilization rate of thermal energy,short effective time,high recovery rate and low cumulative gas-oil ratio.It has become the mainstream technology for heavy oil production.However,the length of horizontal well in SAGD horizontal wells is usually longer than that of conventional thermal recovery wells.The use of general steam injection method is prone to uneven distribution of borehole suction along the wellbore,resulting in low and unsafe reservoir area Big.One of the ways to solve this problem is to add the steam valve and adjust the flow of steam along the horizontal section so that the steam can flow to the toe end so as to achieve the uniform steam injection in the horizontal section.Firstly,this paper established the mathematic model of heat transfer and mass transfer in the horizontal well section during the normal steam injection process.This model can be used to solve the pressure,temperature,dryness,radial outflow and other physical quantity in the wellbore during steam injection in horizontal wells.Secondly,through literature research,the structural features,working principles,advantages and disadvantages of several types of steam distribution valves commonly used in the field at present were described.Considering the steam flows in the horizontal wellbore was gas-liquid two-phase flow,proposed a new formula for the throttling pressure drop of the steam distribution valve.The formula can accurately solve the pressure drop of the steam flowing through the steam distribution valve under different dryness conditions.The conventional steam distribution valve and constant flow distribution valve were numerically simulated by Fluent software.By setting different boundary conditions,the flow process of steam in the steam distribution valve is simulated,and obtained the pressure cloud diagram,speed cloud diagram and speed vector diagram of steam with different degrees of dryness flowing in the steam distribution valve.Comparing the simulation results with the results of the proposed formula,the error is within 5%,which shows that the proposed formula has better accuracy.Lastly,combined with the structural characteristics of uniform steam injection string,established a multi-point uniform heat transfer and mass transfer mathematics model considering the throttling action of the steam distribution valve.Based on this model,a uniform steam injection design program for SAGD wells was developed using VB.This program can reasonably design steam distribution valve parameters according to different steam injection conditions.