EFFECT OF TEMPERATURE ON MICROSTRUCTURE,MINERAL COMPOSITION AND ELEMENTS OF SANDSTONE RESERVOIR BEFORE AND AFTER FIRE FLOODING

摘要

At present,fire flooding is an effective method for the late development of steam injection in heavy oil reservoirs.However,there are few studies on the changing rules and mechanisms of fire flooding reservoirs at different temperatures.In this paper,taking the Dujiatai reservoir in Block D of Shuguang Oilfield as an example,we conducted a simulation test of high-temperature calcination of oil reservoir rocks.At the same time,the X-ray diffraction,carbonate minerals,heavy minerals,major elements,scanning electron microscopy,and energy spectrum of the core after the experiments were analyzed,and then we determined the change rules of microstructures and mineral components of the reservoir at 50 °C to 850 °C.The results show that as the calcination temperature increases,the content of quartz increases and the content of feldspar and clay minerals decreases.The contents of kaolinite and chlorite gradually decrease with increasing temperature,and disappear when the temperature is higher than 650 °C.The illite content increases gradually with increasing temperature.When the temperature is higher than 550 °C,the illite content increases significantly.Kaolinite and montmorillonite will transform to illite under calcination conditions with a temperature greater than 350 °C.The major elements SiO2 and K2O showed obvious abrupt change characteristics at 350 °C.Above 350 °C,Fe(OH)3 decomposes at high temperature,the sediment no longer clogs the pore throat,and the petrophysical properties of the reservoir become better.As the temperature rises,pyrite will gradually transform into iron oxide.In this study,the temperature at which pyrite disappeared was approximately 560 °C.The carbonate mineral components were greatly reduced after 250 °C and 650 °C.Scanning electron microscopy and energy spectrum analysis can be used to qualitatively and quantitatively identify the changes in components during the calcination process.Overall,at 350 °C and 650 °C,the mineral composition and petrophysical properties of the rock have changed significantly.