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Carbon dioxide (CO 2 ) in enhanced oil recovery (EOR) has received significant attention due to its potential to increase ultimate recovery from mature conventional oil reserves. CO 2 -enhanced oil recovery (CO 2 -EOR) helps to reduce global greenhouse gas emissions by sequestering CO 2 in subterranean geological formations. CO 2 -EOR has been exploited commercially over recent decades to improve recovery from light and medium gravity oil reservoirs in their later stages of development. CO 2 tends to be used in either continuous flooding or alternated flooding with water injection. Problems can arise in CO 2 -flooded heterogeneous reservoirs, due to differential mobility of the fluid phases, causing viscous fingering and early CO 2 penetration to develop. This study reviews the advantages and disadvantages of the techniques used for injecting CO 2 into subsurface reservoirs and the methods adopted in attempts to control CO 2 mobility. Recently developed methods are leading to improvements in CO 2 -EOR results. In particular, the involvement of nanoparticles combined with surfactants can act to stabilize CO 2 foam, making it more effective in the reservoir from an EOR perspective. The potential to improve CO 2 flooding techniques and the challenges and uncertainties associated with achieving that objective are addressed.

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Hole cleaning for the majority of vertical and directional drilling wells continues to be a substantial difficulty despite improvements in drilling fluids, equipment, field techniques, and academic and industrial research. Poor hole cleaning might cause issues such as stuck pipe incidents, drilling cuttings accumulation, torque and drag, the erratic equivalent circulating density in the annulus, wellbore instability, tight spots, and hole condition issues. In order to enable the real-time and automated evaluation of hole cleaning efficiency for vertical and directional drilling, the article’s objective is to develop a novel model for the cutting transport ratio (CTRm) that can be incorporated into drilling operations on a real-time basis. The novel CTRm model provides a robust indicator for hole cleaning, which can assess complications and enhance drilling efficiency. Moreover, the novel CTRm model was successfully tested and validated in the field for four wells. The results of the real-time evaluation showed that the novel model was capable of identifying the hole cleaning efficiency in a normal drilling performance for Well-C and a stuck pipe issue in Well-D. In addition, the novel CTRm improved the rate of penetration by 52% in Well-A in comparison to Well-B.