Most of the middle eastern reservoirs are in limestones whch are...

Most of the middle eastern reservoirs are in limestones whch are closely related to biologcal activity in shallow water, and are very different to these rocks, which are essentially underwater river deposits. As a river enters the ocean the sedments are deposited in the water as the energy or river flow is not enough to carry the sediments in suspension so they fall to the bottom. If the area has a continental shelf the sediemnts will accumluate there until there is no more room to deposit more sediment until the sediments start to spill over the edge of the shelf and slide down the slope into deeper water in a flow of sediment and water called a turbity current, as the current reaches the flat ocean floor and it slows down, again the sediments are deposited, and generally spread out in a fan shaped structure. Most of the volume of the fan is fine grained stuff, non reservoir, but there are also channele in the fan system that contain reservoir rock. With each new episide of the sediemnt influx the channels will change direction slightly and may or may not connect to a previous channel, and this is the big uncertaintly in these reservoirs, reservoir connectivity, and this is why a good quality 3D is required to try to 'see' these channels and determine the connectivity