Low-salinity water flooding (LSWF) for hydrocarbon recovery has attracted industrial attention, owing to its simplicity and economic feasibility. Although this topic has received numerous studies, mechanisms driving the low-salinity effect remain poorly understood. This study is aimed at investigating the direct effects of injecting lowsalinity brine (0.6 and 0.2 M NaCl) as the non-wetting fluid and Soltrol 130 as a synthetic wetting fluid on outcrop "Austin Chalk" rock samples. The petrophysical properties of rock samples were estimated by saturating the core samples with high-and low-salinity brine at laboratory conditions. Experiments were conducted for unsteady-state and steady-state flow for both imbibition and drainage processes. A shift to the right has been observed for the relative permeability curve of 0.2 M NaCl along with a drop in irreducible water saturation (S wi ) and in residual oil saturation (S or ). Furthermore, the results have shown a reduction in irreducible water saturation from 22.2 to 18.7% when using 0.2 M NaCl compared to 0.6 M NaCl. The current research demonstrates that ionic interactions among rock, oil, and brine compositions would alter the in situ wettability of the carbonate samples from oil-wet/mixed-wet to more water-wet conditions. A correlation is found among the double-layer expansion, ζ potential, and wettability alteration during LSWF. Moreover, improved oil recovery takes place during LSWF only when a repulsive electrostatic force between oil−brine and mineral−brine interfaces is induced by the change in brine composition. ζ potential of the carbonate is found to become more negative with the dilution of the brine. After the sample is aged with oil, the ζ potential changed, indicating an alteration in wettability.

The optimum drilling of oil and gas wells are achieved by reduce costs and time, which will be accomplished with an optimal hydraulic cleaning program. Drilling fluid characteristics, drilling parameters, and well geometrics are regarded as major categories for achieving an optimal hydraulic program based on depth, penetration rate, and flow rate. This study was used a set of equations that related directly and indirectly to estimate the optimal cleaning efficiency in annulus. The procedure is applied here using actual data from an Iraqi oil field to determine the limitation of all parameters that affect the lifting capacity. Cutting transform was regarded as a major element of the well cleaning program as a result of constraints such as avoiding high surge pressure during lifting pipes, high swab pressure when downloading pipes, and fluid loss during rotation. An increase in annular space indicates a decrease in the capacity of drilling fluid to lift cuttings to the surface and an increase in dynamic shear stress. Also, an increase in cutting size, which has a direct relationship with penetration rate that can be effect for cleaning efficacy in annulus.