石油专业英语课件 Part I 2 The How and Where of Petroleum.ppt

Lesson 2 The How and Where of Petroleum 2.6.3 Water Drive Bottom drive occurs when the oil accumulates in a thicker area underlain by water, which pushes it toward the surface. . Edgewater drive is usually considered more efficient than bottom water. The edgewater drive occurs usually when the oil accumulation is relatively thin, completely fills the formation, and the formation is surrounded by water. Oil may be taken from the accumulation faster than the water can flow in to occupy the vacant space left by the oil and thus maintain the reservoir pressure. The pressure of the water declines and the well may become a combination: part water drive and part depletion drive. Lesson 2 The How and Where of Petroleum 2.6.3 Water Drive Generally speaking however, the pressure will remain high as long as the oil removed is replaced with an equal volume of water. If a high pressure is maintained, such a well will continue to flow until the oil is exhausted and the well finally produces only water. Since water is more efficient than gas in displacing oil from the rock, anticipated recovery rates are considerably higher for a water drive well. Combinations of water and gas cap drive may occur naturally and some wells flow by gravity drive. Such gravity or drainage drive wells offer excellent recovery if the reservoir dips sharply down to where the well is located and the reservoir rock is highly permeable. Lesson 2 The How and Where of Petroleum 2.7 Reservoir Economics Since the primary reason for locating and exploiting reservoirs is economic, some idea of how much oil and gas they contain must be available before any attempts to drill and produce are made. Oil and gas still in the ground are referred to as reserves. Estimated reserves are those in reservoirs which have not been tested or produced from. proven reserves are those known to exist in producing reservoirs.