A design method for choke diameter of separate layer production

To control effectively the liquid production rate of each oil layer in two oil bearing series with different reservoir physical properties, so as to inhibit high-water-cut oil layers and release low-water-cut oil layers, the technical idea of controlling the liquid production rate of each layer by means of the bottom hole choke was proposed referring to the design methods and working principles of downhole throttle of gas well and separate layer water injection choke of water injection well. Then, a mathematic model was established based on the differences of different oil layers in terms of permeability, effective thickness and reservoir pressure. Firstly, the liquid production rate of each oil layer is calculated according to Darcy's Law. Secondly, the pressure difference before and after the bottom hole choke is calculated based on the open area of bottom hole choke at different liquid production rates. And thirdly, the equation of conservation of energy suitable for high- and low-permeability layers is established by controlling the production pressure difference between two oil layers rationally, so as to optimize the diameter of bottom hole choke used for separate layer production. This method is applied on site in 12 separate layer oil producers. And average oil increment of each well is 3.6 t and average water cut declines by 22.1%. It provides the new technology for separate layer production.