| With the development of industrialization,all kinds of fossil fuels(coal,oil,natural gas)overuse,the CO2 concentration in atmospheric is increasing year by year and it caused serious environmental problems.The governments around the world have begun to recognize the importance of CO2 emission reduction.CO2 geological storage is an effectie technology to cope with environmental changes and significantly reduce CO2 emissions by the international community.Numerical simulation technology,which is an important technology to research the CO2 geological storage,has been widely used.Due to the lack of a good pre-processing and post-processing graphical interface for this simulator,it is diffuclut to deal with characterize hydrogeological features and parameters of processing.Althougth there is a commercial software for it,it still needs to improved at this aspect.At the same thime,It's need to improve the numerical simulator capacity constraints for large-scale model,the parallelization aspects of the simulator is also studied.Using these tools,combined with the pilot engineering of Ordos,a systematic study of the effects of geological characteristics for the CO2 geological sequestration is studied.Based on these problems,the main research contents,methods and work is as follows.The new technology and methods of multidisciplinary cross is applyed to developed this visulization software.The detailed research about several key problems in the process of modeling,is included:(1)For the irregular and multi constrained boundary,triangle mesh is completed by the point insertion algorithm.(2)This paper use the plane triangle net to accomplist the three-dimensional geological modeling.And the fault models are builded by the method of fitting plane or importing the fault data.(3)The parallel,space interpolation algorithm of the inverse distance and kriging is completed.In the parallel algorithm tests of the inverse distance,five CPU can reach 4.1 times faster than the one CPU;In the parallel algorithm tests of the kriging,five CPU can reach 3.8 times faster than the one CPU.(4)The model parameters can be processed by the parameter partition mehtod,the space interpolation method or the attribute model to simulate model method.The special tectonic fracture or fault medium can be dealed with the multiple medium model.(5)The geological body can be discretized into non-isometric grid,radial grid or the irregular grid.(6)Under the help of the OpenGL,the point,line region and body data can be saw,like contour,contour surface,profile and animation,ets.At the same time,you can edit and modify it.(7)Providing a common data input/output interface,such as TOUGH2 model files,common graphics files,as well as the MapGis's data file and AutoCad's DXF file(8)Finally,after completion of one model,visualization software provided the model checking function,in order to modify the unreasonable parameters in real-time correction.There are two main improvement for the numerical simulator.The first,It's difficult to deal with the heterogeneous anisotropic geological conditions in TOUGH2 simulator,therefore,a new algorithm,using anisotropic permeability tensor,was coupled in TOUGH2's simulator.And the direction of rock's hydralic conductivity and elements coneection parameters for anisotropic medim was added in the keyword of"ROCKS" and "CONNE" respectively.It found that the main direction of rock permeability effected the direction of the CO2 plume through the instance.The second,the parallelized simulator,which adopt dynamic memory allocation and the shared memory structure of parallel way,was developed to deal with large-scale model in the complex geological structure of Ordos basin.And the model test was carried out.Test results showed that two CPU can reach 1.66 times faster,three CPU can reach 1.92 times faster,four CPU can reach 2.28 times faster than one CPU.With the help of the above tools,we reached the CO2 geological storage in the ordos CCS demonstration site,from different angles and influence factors,the specific contents of the study are as follows:Taking the actual infusion site condition as the basic model,the effects of CO2 perfusion ability,storage security,the temperature field and boundary were studied on the basic model.Model results show that:(1)In the current perfusion pressure,demonstration area was difficult to finish 2 million tons of injection within 20 years,but the sequestration of CO2 was safe.(2)In non-isothermal model,the temperature fallsing phenomenon happened near the borehole,thus it affect the sequestration of CO2,20 years less storage capacity than the isothermal model nearly 90000 tons,accounting for about 6.3%of the total storage capacity,so it was not more likely to complete the design of 100000 tons/year target.From the model computing time,non-isothermal model requires longer computation time than the isothermal model,In quad core parallel cases,the non-isothermal model need more computing(about 21.6 hours),and more memory consumption(about 825.5 MB).(3)It's reasonable for the lateral boundary of the basic model that the CO2 geological storage quantity was vary similar in the different boundary model,such as the quantity of the 20km model had less20,000 tons in 20 years than the quantity of the basic model.For the controllable factors-CO2 injection pressure and uncertain factors-salinity of salt water,the effect of storage on CO2 geological storage study respectively.Simulation results show that:(1)In more than 8 MPa well head pressure,it can accomplish the target about 2 million tons of injection in 20 years.The maximum horizontal migration distance of CO2 in reservoir for the 20MPa well head pressure was less than 600 m.The horizontal migration distance of CO2 is less than 650 m after stopping injection 80 years.(2)High salinity of salt water is bad for CO2 geological sequestration.In the case of saturated salt,CO2 sequestration was only 1.1 million tons in 20 years,,it is far from being completed CO2 design goal.And in the absence of salinity cases,in 20 years,CO2 sequestration can reach 1.44 million tons,CO2 sequestration is more 30,000 tons than the basic model,but it still can't complete the design goal.At the same time,it was found that the CO2 gas seal of sequestration value is higher,storage security is lower in the salt water of high salinity model from the analysis of the CO2 security form storage.Aiming at the demonstration site formation with some geological phenomenas,such as dip and potential faults,we study its effect on CO2 geological storage respectively,The simulation results show that:(1)Small angle of dip angle is beneficial to more CO2 sequestration,but from the safe form of sequestration,the greater the dip angle is,the lower safety of CO2 sequestration is in the upper reservoir.In the largest dip angle(3°)model,in 20 years,the farthest distance of CO2 migration along reservoir is less than 700 m,so the CO2 geological sequestration wasa safe currently.(2)Considering the effects of throughout the fracture in the reservoir,CO2 geological sequestration was safe in the injection period of 20 years,and there was not found CO2 leak.But when was stopped injecting for about 300,CO2 had passed through the HeShangGou group along the F96 fracture,and had migrated some distance to the horizontal direction.It can be seen that the CO2 has breakthrough the upper HeShangGou group cover layer,therefore,the CO2 geological storage is not safe at this time.Combined with CO2 injection process and injection after two stages,the reservoir heterogeneity on CO2 geological sequestration effects were studied respectively.The results show that:(1)Taking the son reservoir of ShiQianFeng group as an example to study the effect of CO2 geological sequestration with reservoir heterogeneity of strata in rhythm.In the positive rhythm CO2 reservoir,the higher the degree of vertical heterogeneity is,the smaller amount of CO2 sequestration had.In the CO2 reservoir of reservoir rhythm,the greater the vertical variation coefficient was,the greater the amount of CO2 sequestration had.The storage capacity of homogeneous rhythm of CO2 sequestration was between positive rhythm and reservoir rhythm.For the positive rhythm and reverse rhythm reservoir of the same degree of heterogeneity,The upper of reverse rhythm reservoir will storage more CO2,and at the bottom of positive rhythm formation would storage more CO2.(2)By selecting a sub-reservoir relatively far from the injection wells with the CO2 injection stopped,this paper studied the effects of heterogeneity on the diffusion and movement of CO2.Meanwhile,Generating the correction factor of the permeability was put forwarded by using an inverse methodof geostatistics.The comprehensive indicators-IB,were applied as he evaluation index of heterogeneous program.It's found that reservoir heterogeneity contributes to the gas phase CO2 dissolved into liquid CO2 sequestration,and the higher the degree of heterogeneity is,the more the amount of CO2 dissolved salt water was,therefore,it was very beneficial for the safety form of CO2 sequestration. |
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