In geology, the pressure of a formation means the fluid pressure inside the pores of a geological formation, usually known as pore pressure. This pressure in the formation can be lower or higher than the hydrostatic. Pore ​​pressure is determined based on factors such as depth, temperature and type of sediments of the formation and can affect the behavior of the formation. The pressure of the formation is caused by the weight of fluids inside the underground permeable rocks. By increasing depth, the pressure will be increased. The water accumulated inside the porous and permeable formations gets more pressure with increasing depth, just like the pressure increases with increasing water depth in the seas. As the depth increases, the vertical distance increases the fluid pressure. The formation pressure is directly related to the subsidence rate of the bed of the sedimentary basin as well as the rapid sedimentation rate of particles in it. If the bottom of the sedimentary basin has continuous subsidence due to tectonic factors and the rate of sedimentation in such a basin is fast, it causes a large thickness of sediments to form in a short period of time. In this case, increasing the weight of the upper layers to the lower layers causes an increase in the formation pressure.