Petroleum reservoirs are underground formations that contain accumulations of oil and natural gas. These reservoirs are typically found in porous rock layers, where the hydrocarbons can be trapped by impermeable rock layers above, preventing them from escaping. The formation of these reservoirs occurs over millions of years through geological processes involving organic matter, heat, and pressure. Exploration for petroleum reservoirs involves geological surveys and drilling to locate these valuable resources. Once identified, extraction methods such as drilling and fracking are used to access the hydrocarbons. Understanding the characteristics of a reservoir, including its size and pressure, is crucial for efficient extraction and management of these energy resources.