Influence Of Formation Dip On CO₂ Migration And Storage Amount In Reservoir

A large number of carbon dioxide（CO₂） gas emits into the atmosphere caused by the greenhouse effect, has been paid close attention to by the international society. CO₂ geological storage is one of the most effective and the most direct means about reduction of CO₂ emission. When using numerical simulation method to proceed potential evaluation and safety assessment about CO₂ geological storage in saline aquifers, for a variety of reasons, the storage stratum usually be generalize as horizontal stratum. But in fact, horizontal stratum is not common in nature. Most of strata is gradient because of the actions of geological structure and the diagenesis, and the existence of the formation dip has an impact on CO₂ storage and migration distance. It is crucial to how to analogue simulation the existence of the simulation of dip and the effect of formation dip.Based on the above reasons, the study of this paper simulates and predicts the influence of formation dip through TOUGHVISUAL and TOUGH2 software. The relevant hydrogeological conditions come from Shiqianfeng Formation of CGS demonstration projects in Ordos basin. Simulation study of dip and reservoir environmental elements（injection pressure, injection temperature,porosity and permeability parameters） space migration and changes in CO₂ storage, the following conclusions:1. Based on the actual geological conditions of Shiqianfeng Formation in Ordos Basin, this paper designs four schemes including 0°, 5°, 10°, 15°four formation dip, discussing the the influence of stratigraphic dip on CO₂ migration distance and storage. Study show that: in the formations of different formation dip, the distribution layer and the modality of the halo of CO₂ in the Shiqianfeng Formation are almost consistent, but the greater the formation dip angle, the farther CO₂ migration distance. When the formation dip is 15°, the migration distance of CO₂ increases by 52.94% than that in horizontal reservoir formation.For the actual geological conditions of Shiqianfeng Formation in Ordos Basin,in the injection of 20 years, the larger the formation dip, the smaller the gas phase CO₂ storage amount, but the greater the liquid phase CO₂ storage. Formation dip for storage capacity compared with the level of formation, there is a critical point,before the time point,the larger the formation dip,the greater the total CO₂ storage; after the time point,the larger the formation dip,the smaller the total CO₂ storage.2. According to the environmental factors（injection pressure, injection temperature and permeability parameters） and the change of the formation dip, There are 24 sets of design schemes（scheme 5 28）,this paper selects controllable environmental factors and obvious factors those influence on CO₂ geological storage. It get the following conclusions:（1）When the injection pressure is constant, the greater the formation dip, the farther the CO₂ migration distance, the less the CO₂ gas phase storage, the larger the CO₂ liquid storage; The total CO₂ storage changes with the change of the injection pressure. When the injection pressure is 1.15 times, the larger the formation dip, the more the total CO₂ storage; When the injection pressure is 1.3 times and 1.5 times, in the early stage of the injection, the larger the formation dip, the greater the total CO₂ storage, in the late injection, the larger the formation dip, the less total CO₂ storage.（2）When the injection temperature is the same, the larger the formation dip, the farther the CO₂ migration distance, the smaller the storage of CO₂ gas phase,the greater the liquid phase storage of CO₂, the total storage is basically remain unchanged. When the injection temperature is not the same, in the formation of the same formation dip,injection temperature has great influence on the temperature near the injection well. The higher the injection temperature, the higher the temperature near the injection well. When the CO₂ injection temperature is different, the migration distance is almost the same, but the gas phase storage of CO₂ increases with the increase of injection temperature, the liquid storage of CO₂ varies with injection temperature very small, the total CO₂ storage increases with injection temperature increases.（3）When porosity and permeability remain unchanged,the regulars of CO₂ migration distance and CO₂ storage are the same as the regulars of different injection pressures（1.3 Times）. When porosity and permeability parameters change, at the same formation dip of strata and the same year of migration, CO₂ migration distance decreases as the porosity and permeability becoming large, every storage of CO₂ increases with the increase of porosity and permeability.The larger the formation dip, the worse the CO₂ storage security, for a long time, the easier causing leakage.To sum up, formation dip can make the CO₂ migration distance and storage obvious change, some changes of environmental factors affect the spatial distribution and storage of CO₂ very remarkable.So, in the process of CO₂ geological storage potential reservoir evaluation of the project and safety assessment in CO₂ geological storage, it’s necessary to consider the effects of formation dip, the research has theoretical and practical significances.