There are many oil and gas conventional reservoirs in Saudi Arabia have been exploited, but still there are also need to be explored and produced especially in the fields of unconventional shale gas. Investigation the extending of rock source of the hot shale gas Qusaiba formation in North part of Saudi Arabia, the most important rock source in the word, is crucial for one of the most promising shallow shale gas reservoir in the region. Most previous studies in the area were a geological, petrographical, petrophysical, geochemical characteristics or well logs studies which are not enough to show the continuously of the reservoir and map the diverse of the depth changes. The lack of the geophysical studies in the area inspiring to perform such study and image how the continuously and behavior of the reservoir subsurface. Imaging the geological stratigraphy of area utilizing a multiple geophysical methods is a crucial step to disclosure the unconventional reservoir and understand the source rock extending underneath the North region of Saudi Arabia. A good achievement is shown in this study using this integration of seismic migrated image and gravity geological model. This integration provides a robust and true subsurface geological formations, structures, and determined thickness and depth of the Lower Silurian Sharawra Qusaiba and Sarah formations. This work would be a valuable contribution in unconventional reservoirs exploration in shale gas in Saudi Arabia.