Gas Drilling Well Control And Kill Research

Gas drilling has advantages of drilling fast,reservoir protection,improving well production,etc.But after drilling into the gas producing zone,it comes across the difficulties of well control and well killing.During well killing,with the drilling fluid injection,it forms complex gas-liquid two phase flow in wellbore.Buttonhole pressure rises along with the liquid column rising,then gas production goes down.In return,the gas production affect wellbore flow.Therefore,the two phase flow and the fluid flow through porous medium affect each other.However,there is no mature theory and calculation method aims at the problem.On the basis of the basic theory of gas-liquid two phase flow and reservoir transient gas flow through porous medium,this paper built a set of calculation method of buttonhole pressure,gas production variation,dynamic liquid level height change,flow friction loss,etc.Though which,key construction parameters are optimally designed.Building the calculation method of transient reservoir flow during well kill that can get the answer of gas production.Solve the distribution of formation pressure,change the boundary conditions on the formation and numerical solute unsteady seepage partial differential equation.And divide the near wellbore rock into differential element,according to the non-Darcy seepage and Darcy seepage calculation theory,get the transient gas production under variable conditions of buttonhole pressure.To establish gas-liquid two phase transient flow calculation method of well kill in gas drilling,based on the basic theory of gas-liquid two phase flow,such as flow type judgement,friction loss calculation and pressure gradient calculation,the gas-liquid mixture column during well kill is treated as dynamic liquid level height change,then couple it with mud injection variation in the global calculation.Based on the basic theory of gas-liquid two phase flow,the change progress in gas production is coupled with gas-liquid two phase annular pipe flow model to form transient gas-liquid two phase annular pipe flow calculation method.Key parameters such as buttonhole pressure,formation gas production and dynamic liquid level height are obtained.Experimental validation.According to the actual working condition of the well kill,we design experiment equipment and simulate the key parameters of well bottom hole pressure change,dynamic liquid lift height.After comparison of the calculation result of the same input parameter,it shows that the method has high calculation accuracy and can satisfy the requirement of engineering calculation.Based on the calculation method,the optimum combination parameters of the drilling fluid density,gas injection volume,and wellhead backpressure are worked out.And the well killing construction parameters are optimally designed,it is meaningful for the oilfield construction.