oa Variations in Formation Water Salinity and Its Bearing from Oil API in a Shallow Heavy Oil Bearing Sandstone Reservoir in Ratqa Field, North Kuwait

The extensively drilled, Lower Fars Formation of Miocene age, hosting heavy oil in the Ratqa Field of<br>North Kuwait, comprises alternations of fluvial to estuarine channel sands and associated overbank<br>shales, ranging in depth from 260 feet in the South to 550 feet in the North, capped by a shale,<br>considered the regional top seal. The formation thickness ranges from 750 feet in the South to 900<br>feet in the North. The sands are disposed along a relatively gently sloping SW-NE structural monocline,<br>without any observable structural or stratigraphic entrapment. Large variations in formation water<br>salinities have been observed from well testing and from log derived estimations. Presence of very low<br>salinity water at shallow depths of 200-300 feet and enormous increase in the salinity with depth, at<br>places, indicates possible contamination of formation water having over 100,000 ppm as NaCl<br>concentration, with a relatively fresh water.