Experimental study on mechanism of carbon dioxide disperse cuttings

Key words:  carbon dioxide  water  cuttings  particle size  experiment

Abstract:

The cuttings from Dongying Formation were chosen to study the dispersion mechanism of CO_2on cuttings at the bottom hole using a simulated device. The XRD mineral compositions and ion types in reaction solution were analyzed as well. The results show that the influence of CO_2on the particle size of cuttings is little. After long time soaking in the formation water, the particle size of the cuttings would be smaller. Under the circumstance of the mixture of CO_2and formation water, the average particle size of the cuttings decreases sharply at first, and then it becomes stable gradually. With the increase of the temperature and the pressure, the average size would decrease accordingly. With the coexistence of formation water and CO₂, the change of the particle size for the cuttings in Dongying Formation is caused by the clay mineral dispersion in the cuttings, which is boosted by CO₂. Also, CO_2reduces the hydration reaction time of the clay. At the same time, carbonic acid is formed by the reaction of CO_2and H₂O, which resolves part clay in the cuttings and accelerates the reduction of the average particle size.