In the oil-gathering stations of most OGPDs, oil water sand clay mixtures that enter the settling equipment after passing through the separators are initially separated and collected in appropriate tanks. Prior to the production of commercial oil, more labor and energy is utilized to separate water and sand-clay mixtures from oil. Tanks are quickly contaminated with bottom sediments consisting of sand-clay and cleaning of them is difficult. Mixtures of sand-clay-water from settler, formation water from oil tanksa are drained into open oil traps, as a result, the environment is polluted with oil wastes and oil losses occur. It is more efficient to use a horizontal oil and gas separator to overcome shortcomings identified in the reconstruction of the tank farm with a capacity of more than 1.500 m3/day. Sand-clay separator should be installed at the inlet of it to protect the separator and tanks from sand-clay mixed sediments. Sand-clay separators should be installed inside the overflow tanks for better separation of formation water and sand-clay mixtures from oil, oil suspensions and sand-clay mixtures from water in formation water storage tanks. In order to reduce evaporation losses in the tanks, an auxiliary palte should be used under the PSV and the gas phase of the technological tanks and commercial oil tanks should be connected via pipes.