Research On CO₂ Flooding Transportation Limit Distance And Optimization On Processing Parameters In Low Permeability Oil Field

The peripheral oilfield of Daqing belongs to the typical "three low" reservoir,the reservoir water absorption capacity of which is poor,the water injection pressure of which is high,the water injection development effect of which is poor,the oil recovery rate of which is low,and it's difficult to obtain the considerable economic benefit.Supercritical carbon dioxide has good mutual solubility with crude oil,which can reduce the viscosity of crude oil,make the volume of crude oil expands,reduce residual oil saturation,extract the light components of crude oil and improve the permeability around the wellbore,so it is expected to become low permeability possible technology for oil displacement.With the increase of gas concentration of carbon dioxide and the increase of injection amount,the profile equilibrium is deteriorated,and the front edge of carbon dioxide gas is advanced along the high permeability zone,which results in the carbon dioxide emission in the oil recovery fluid far beyond the initial development forecast data,results in part of the oil wellhead oil temperature becoming too low,and even makes the wellbore frozen block.In this article,we focus on the study of carbon dioxide flooding test area in Songfangtun Oilfield,Daqing,and start the following research:First of all,in terms of the conservation equation of mass conservation,the conservation equation of momentum and the conservation equation of energy,we can establish the calculation model and pressure gradient model of carbon dioxide flooding wellbore.Considering the interactive relationship among the temperature of the wellbore,the pressure gradient and the thermophysical properties of the gas-liquid two-phase flow.By using Visual Basic language to call Refprop software,we can calculate the thermophysical properties of carbon dioxide under different pressure and temperature conditions and the temperature field and pressure field of carbon dioxide-driven wellbore were calculated in a coupled way.Second,according to the calculated carbon dioxide flooding temperature and pressure,we can determine the phase of carbon dioxide in the extracted material.By making use of Aspen HYSYS software,and the conditions of carbon dioxide formation of hydrate were simulated,thus we can predict the existence of hydrate in carbon dioxide flooding wells.On the basis of this,the heat load caused by carbon dioxide hydrate decomposition,liquid carbon dioxide evaporation and Joule-Thomson cooling effect can be calculated,and the mechanism of carbon dioxide flooding pipeline can be analyzed.Finally,by calculating the temperature drop of the carbon dioxide floodplating network during the process of gathering and transporting and the temperature drop between the mixed hot water and the extracted liquid,we can establish the optimization model of the watercontent and the water temperature.By Aspen HYSYS software,the temperature of the formation,the amount of liquid production and the temperature of the water temperature on the impact of water might be analyzed and simulated.So we can ensure that the output liquid safe and smooth delivery to the joint station and achieve the purpose of saving energy and cutting down the consumption.It is of great significance to study the limit of carbon dioxide flooding and the optimization of process properties in low permeability oilfield.On the one hand,in the premise of confirming the safety of carbon dioxide flooding,the purpose of saving energy consumption is achieved.On the other hand,it also provides technical support for carbon dioxide flooding and builds the technical foundation for further promotion of carbon dioxide flooding.