OIL FLOW-RATE LOSS

The article reviews a very important for oil field development problem of optimization of producing well operation. The author proposes to take into account the following factors: producing well productivity dependence on decreasing of its bottomhole pressure lower than bubble-point pressure of oil; well productivity decline rate depedence on oil reserve depletion; and differences in density and mobility of oil and displacing water, and operation conditions of sucker-rod pump run-in to the well bottomhole. Productivity depedence on the bottomhole pressure was determined on the basis of the factual data of producing well investigation. During determination of rational values of bottomhole pressure or fluid flow rate, sucker-rod capacity is actually strictly set to producing well according to it, which brings an essential error in calculations, because sucker-rod capacity is provided not only by oil, but also, by water and gas escaped from oil. An important conclusion is made in the article: bubble-point pressure of oil should be regarded as a rational bottomhole pressure of producing wells. Three main potential reasons for oil flow rate decline are mentioned, which are the following: inaccuracy of the optimization method; awareness of current production parameters; and selection of equipment and operation conditions of sucker-rod. It is concluded that overstating of sucker-rod capacity could reduce oil- flow rate and increase water cuts.