Multiphase Flow Simulation And Gas Recovery Process String For Tight Gas And Coalbed Methane Combined Production Well

In the traditional view,tight gas and coal-bed methane exist in different geological layers with different depths.It seems very difficult to detect two gases simultaneously.However,a large number of exploration results show that in the coal bearing strata,there are abundant tight gas resources in the adjacent strata besides the coal bed gas resources.At present,if only one kind of gas is developed,its overall production of single well is low and its economic benefit is poor,especially the daily production of single well of coal bed gas is less than 90%of 1000m3,and the economic benefit is very poor.According to the characteristics of vertical overlap in some areas of tight gas and coalbed methane,the technology of tight gas and coalbed methane production is discussed in order to improve the production of low taste unconventional natural gas single well and realize low cost mining.In this paper,from three aspects of gas-liquid two phase carrying coal powder,namely,gas liquid coal powder three-phase flow simulation,interlayer interference and gas production tube column structure,this paper studies the concrete technology of tight gas and coal seam gas production,and focuses on the following work:(1)A simulation experiment device for gas-liquid solid three phase flow is set up.Using transparent plexiglass tube to design and build a visual gas liquid solid three-phase flow simulation device,the whole set of experimental devices is composed of four parts:gas and liquid supply device,fluid inflow system,gas inflow system,test and data monitoring device,which can make solid particles not pass through gas,liquid flow meter,and measure solid at the same time.The flow volume of the device is 3.27M long,5.77m and 40mm.(2)The experiment of carrying pulverized coal with gas-liquid two phase is carried out.By using the established experimental device,15 groups of multiphase flow experiments with different gas flow,liquid flow and solid flow were carried out to test the pressure of gas,liquid and solid in the vertical section under different flow states,and the flow state under different flow conditions was captured with the help of a digital camera,and the difference of gas and liquid two phases was compared and analyzed.(3)Seven kinds of common pressure drop models are evaluated.By using 15 measured data,7 common pressure drop models of Ansari model,Gray model,Hagedorn-Brown model,No Slip model,Orkiszewski model,Beggs-Brill model and Mukherjee-Brill model are evaluated.The minimum error of gas-liquid two-phase flow is Hagedron-Brown model,gas liquid coal powder three-phase flow.The smallest error is Mukherjee-Brill.(4)The Hagedron-Brown model is modified by gas liquid pulverized coal three-phase flow,and the retention rate Hs parameters are introduced to obtain the relationship diagram of the retention rate and apparent gas flow velocity.The retention rate decreases first and then increases with the increase of apparent gas flow velocity,and the apparent gas flow velocity lOm/s corresponds to the minimum holding rate.At the same time,the lower the gas flow rate,the lower the apparent liquid velocity,the greater the solid holding rate.When the gas flow rate is greater than lOm/s,the holding rate of the liquid under different apparent liquid velocities is approaching,indicating that the liquid flow rate has little effect on the holding rate at high gas volume.(5)In order to simulate the interference of well bore,two layers of pipe column model is established by Gambit software and Fluent software,and the grid division,calculation model setting,viscosity model and fluid material selection,boundary condition and solution setting are used,and the influence of outlet pressure and water volume fraction on interference is analyzed.(6)The process pipe column design for tight gas and coalbed gas production is carried out,and the influence of different process pipe columns(oil pipe suspension,oil pipe down position,sliding sleeve seal and machine pillar)on wellbore pressure distribution and interlayer interference are analyzed.According to the types and characteristics of multi gas production layer group,the development mode of multi gas production layer group is optimized.The production of single well is measured and the reasonable method of gas extraction is optimized.In this paper,based on the characteristics of dense sand rock layer and upper and lower overlap of coal seam,the pressure drop model of gas liquid coal powder three-phase flow is set up.The interlayer interference phenomenon is simulated by Fluent software and the structure of two layers of pipe column is designed,which provides the technology and method for tight sandstone gas and coalbed gas coalbed gas production.