Mechanism Of Foam Migration And Optimal Design Of Pipe String In Drainage Gas Recovery

Natural gas is generally exploited by depletion.With the gradual decrease of formation energy,the natural gas and water adsorbed on the rock wall are gradually desorbed.Due to the difference in gas-liquid viscosity,the gas is the first to escape,while the water is gradually accumulated and carried by the gas into the wellbore to form a liquid.The prevention and control of wellbore effusion can be realized by the way of foam drainage and gas extraction without affecting production.Based on the research of relevant literature,this paper studied the bursting mechanism of foam,analyzed the migration characteristics of foam in the wellbore,and finally carried out the design of enhanced bubble drainage string.The results show that the foam itself is an unstable system,and its breakage process has a certain randomness.There is a certain amount of energy inside the foam.Due to the strong compressibility of the gas itself,the size of the foam has a great influence on the foam during the fluctuating increase in the velocity of the liquid film position.The larger the foam is,the thicker the liquid film is,and the stronger the stability of the foam is.The lower the surface tension between liquid phase and gas phase,the more stable the foam is.Appropriate increase in the concentration of surfactant in the liquid phase can increase the stability of the foam.The lower the surface tension of the gas-liquid two phases is,the more stable the foam is.However,under experimental conditions,multiple bubbles interact with each other.After some bubbles are broken,the water phase will converge with the water phase of other bubbles,thus increasing the liquid film thickness of other bubbles and enhancing the stability of the foam.At the same time,a relatively stable structure will be formed between multiple bubbles,which is more stable than a single bubble.The internal bubbles will be protected under a relatively stable condition and the whole system will be maintained in a relatively stable state.When the bubbles are in discontinuous state,the migration speed of bubbles near the wellbore is slow due to the influence of the high velocity of natural gas in the wellbore.When the bubble is in discontinuous state,the stabilization time of the bubble increases firstly and then decreases with the increase of bubble diameter due to the dual influence of gas carrying force and gravity.When the foam in the wellbore is continuous phase,the height of the liquid column in the wellbore changes linearly with the drainage time.The analysis of the reason shows that although the height of the liquid column has a great influence on the gas production,the change of the gas production has no obvious influence on the height of the liquid column.After join the second foaming device,liquid level height gradually reduced in the wellbore,and at the initial time which meet drainage efficiency is very high,under the injection pressure of 2.5 MPa up to 19mm/min,the entrance of the 1 MPa pressure discharge fluid velocity reached 8 mm/min,suggesting that join the device can effectively speed up the drainage,implement efficient bubble row.By comparing the experimental results in Chapter 3,it can be concluded that the most important problem for the natural gas Wells with foam drainage is to improve the stability of foam.Therefore,the research on foam drainage gas production should ensure the stable existence of foam in the wellbore,and avoid the breakage and secondary settlement of foam in the wellbore as far as possible.