Effect Of Drilling Fluids Contaminations On Saudi Reservoir Rock Wettability

Abstract

Wettability is a key parameter that affects the petrophysical properties of reservoir rocks. Mud nitrate during drilling pay zone causes a significant change in rock wettability that will affect the oil production and enhanced oil recovery. This change depends on the mud filtrate and the oil rock systems studied. The objective of this paper is to investigate the influence of water base mud, oil base mud, and Partially Hydroxide Polyacrylamide (PHPA) mud filtrate on the reservoir rocks wettability. The drilling fluid compositions that recommended for drilling horizontal wells had been used in this study. The reservoir rocks used were Saudi water-wet sandstone and limestone. The contact angle was used to measure the rock wettability. Also, the effect of temperature on wettability alteration had been studied The results showed that the rock samples used are originally water-wet. Water-based drilling fluids tends to make the system water wet. The contact angle tends to increase with increasing NaOH and KOH additives as well as temperature increase. In contrary, oil-based drilling fluid changes the system from water wet to strongly oil-wet. This change is higher in the case of using crude oil than diesel oil. The PHPA mud contamination strengthens the wettability of water-wet reservoir rocks towards water. The increase of temperature increases the contact angle in the case of using water-based mud and oil-based mud and vice versa for the case of PAPA muds. The same results have been detected with limestone samples with high slight difference in the contact angle. The contact angle tends to reach its original values after cleaning in case of using limestone.