FIELD: oil and gas industry.
SUBSTANCE: downhole pressure control method based on control theory with prediction models and system theory is referred to downhole pressure control technologies. This method includes: determination of downhole pressure, standpipe pressure, casing pressure, injection rate and output flow in process of well construction, and determination of available overflow or loss. Besides, when overflow or loss is unavailable fine adjustment of casing pressure at well mouth is carried out in compliance with low fluctuations of downhole pressure, standpipe pressure or casing pressure in order to ensure set pressure value of bottomhole pressure, standpipe pressure or vertical casing pressure. Besides, when overflow or loss is available a dynamic model of single-phase or multiphase flow is used in the well bore in order to simulate and compute location of overflow or loss and time of overflow or loss commencement. This method includes additionally: prediction of downhole pressure changes in future in process of well drilling and usage of optimisation algorithm to calculate control parameter that ensures minimum deviation of actual downhole pressure from the preset value in future. Optimisation process is repeated for the next time period upon selecting and setting of the first control parameter.
EFFECT: downhole pressure control within permitted range of fluctuations according to design requirements thus implementing highly accurate pressure control.
7 cl, 4 dwg
