Study On The Reservoir Physical Properties Variation Regulations Of Chemical Assisted Steam Flooding In Heavy Oil Reservoirs

The lack of targeted technology for improving oil recovery after steam injection,which were considered in the paper,and conducts research on the changes in reservoir physical properties of chemical assisted steam flooding heavy oil reservoirs.Through core experiments and mathematical simulation method,the hydrothermal effect characteristics of unconsolidated sandstone minerals under only thermal and the hydrothermal effect characteristics of minerals under chemical assisted thermal action were studied.The contact angles of monomineral were tested under different media conditions and studied the changes in the wettability of reservoir minerals under chemical assisted thermal action.The pore permeability variation of unconsolidated sandstone cores with high injection volume was studied through displacement experiments.Based on the results of comprehensive hydrothermal effect experiments,single mineral contact angle tests,and core displacement experiments,combined with reaction kinetics,a core scale porosity and permeability change model for reservoir particle migration is established.The static water rock reaction experiment was carried out for quartz,montmorillonite,illite and kaolinite.The four factor and three level orthogonal experiments are designed,and the influence temperature,pressure,salinity and p H on hydrothermal effect characteristics of four minerals under the thermal action were studied,A study was conducted on the characteristics of mineral hydrothermal effects under the action of chemical assisted thermal,including temperature,pressure,salinity,and chemical agents,And calculate the proportion of hydrothermal effects under different conditions for each mineral.By shaping mineral powders into rock slabs,the oil droplet contact angles of four minerals at different temperatures,p H conditions,and chemical agents were obtained using image geometry methods.The core sandpack model was prepared according to the mineral content proportion of the four minerals in the reservoir rocks of Block Zheng 364.The sandpack model was respectively carried out under steam flooding,CO₂ flooding,CO₂ steam AOS foam flooding and CO₂ steam CTAC foam flooding at different temperatures,which in order to study the porosity and permeability change laws.The sandpack model was CT scanned before and after displacement to obtain the characteristics and laws of pore volume change and the wettability change in the pore space.And the static reaction lasted for 72 hours at high temperature,and only a series of chemical changes occurred on the surface,resulting in a mass change of less than10%.This indicates that the hydrothermal effect of minerals under thermal action in a relatively short period of time on the physical properties of reservoir rocks is negligible.However,the hydrothermal effect of minerals is relatively obvious after CO₂ injection,and the reaction is significantly weakened after CO₂ and surfactants injection.Besides,the pore changes at 100℃,200℃and 300℃after steam injection volume of 200PV,were 2.2%,3.15%,and 3.77%,respectively.However,the change in core permeability after co injection of CO₂and CTAC into 200PV is less than 1%.A dynamic model of mineral reaction in two-phase flow was established based on the water rock reaction kinetics,and the critical velocity for particle lift off was established by the particle migration conditions.By combining the critical flow rate with the mineral reaction kinetics equation,a mathematical model for coupled thermal and chemical pore permeability changes was proposed.This model can better describe the mechanism and law of pore permeability changes in unconsolidated sandstone cores.The research results of this article further understand the characteristics of physical property changes in chemical assisted steam flooding,and improve the mechanism of physical property changes in the near wellbore zone of loose sandstone reservoirs,providing certain theoretical guidance for the subsequent research on improving oil recovery technology through steam injection.