Study On Reservoir Physical Property Changes Of High Temperature Fire Drive In Heavy Oil Reservoir Of HQ1 Well Area

The Junggar Basin is an important petroleum-bearing basin in China,which has experienced multi-cycle superposition from the Late Paleozoic to Mesozoic and Cenozoic.The HQ1 well area is located in the northwestern margin of the Junggar Basin.The region has rich heavy oil resources and a wide distribution area.After many years of steam injection exploitation,the remaining oil is seriously dispersed.It is urgent to find a replacement method in the later stage of steam injection exploitation in the old heavy oil area.In the early stage,Xinjiang Oilfield launched a fire drive pilot test in the study area,and carried out effective research on the fire drive mechanism,but its research on rock and minerals is scarce.Therefore,in-depth study of the microscopic conversion mechanism of reservoir minerals at high temperature and the effect of rock and mineral changes on reservoir physical properties are of great significance for understanding the fireflooding process.In this article,the outcrop rocks of Badaowan Formation in HQ1 well area were simulated at 10 temperature points,including 300?,350?,400?,450?,500?,550?,600?,650?,700? and 750?,The porosity and permeability experiment,rock mechanics experiment,EMPA electron probe,Raman monitoring at different temperature points,in-situ continuous heating Raman monitoring of maghemite,and changes of mineral characteristics under scanning electron microscope were conducted on the rock samples after simulated fire flooding to analyze the changes of reservoir physical properties before and after high temperature fire drive,and analyze the main control factors that affect the changes of reservoir physical properties before and after fire drive.Acquire the following knowledge:(1)After high temperature(300?-750?),the pore structure of sandstone will change.It is mainly manifested in the development of feldspar cleavage fracture to penetrating fracture,local weak dissolution,combustion and decomposition of surface organic matter;dehydration and illite petrification of kaolinite are accompanied by pseudo-hexagonal plate-shaped and lamellar crystal edge serration ? curl ? chipdismemberment;cracks are produced due to the thermal stress of quartz;the volume of transformation minerals from magnetite to hematite is reduced;with the increasing of temperature,the pores inside and between grains increase obviously.(2)Under the condition of high temperature(450?-750?),the porosity and permeability of sandstone reservoir increase with the change of temperature in a oscillatory way,and the permeability and porosity of burning samples show a significant positive correlation under different temperatures.(3)Before and after high temperature,the internal mineral composition and micro fracture structure of sandstone samples change,resulting in the change of rock mechanical properties.The tensile strength of sandstone samples decreases gradually;the triaxial compressive strength and modulus of elasticity increase with the increase of temperature in a oscillatory way,and they have a positive correlation with each other;the judgment has a certain preventive effect on the collapse of the reservoir after the fire.(4)The increase of rock porosity after high temperature can be attributed to dehydration of clay minerals,combustion of organic matter,dissolution of feldspar,argillization,phase transformation of iron rich minerals and thermal cracking of rocks,among which thermal cracking of feldspar and quartz,dehydration of clay minerals,phase transformation of iron rich minerals and decomposition and overflow of organic matter are the main reasons for the changes of physical properties of reservoir.