Prediction Of Wellhead And Bottomhole Pressure Based On The Height Of Blowout Liquid Column

The occurrence of the out-of-control blowout accident of the “Deepwater Horizon” deepwater drilling platform shocked the offshore oil industry.The platform is advanced in technology and well-equipped,but after the accident,there is no effective emergency killing plan,and the incident has always warned China's offshore drilling Service provider.In order to cope with the various complicated situations that may occur after the blowout is out of control,this paper hopes to establish a method for calculating the bottom hole pressure after the blowout out of control,and calculate the wellhead blowout by obtaining the height of the blowout liquid column when the drilling platform cannot be accessed.Flow pressure and bottom hole pressure provide a reference for the design of rescue and rescue wells after blowout.For bottom hole pressure prediction,the method of inverting bottom hole parameters by well head pressure is usually adopted.After the blowout accident,the well cannot be shut down.At this time,the vertical shut-in pressure and shut-in casing pressure cannot be obtained by traditional methods,so there is no way to calculate the bottom hole pressure and overflow flow.Therefore,the best way to obtain the bottom hole pressure after blowout is to calculate the wellhead pressure according to the height of the blowout liquid column,and then invert the bottomhole pressure through the wellhead pressure to obtain formation parameters.In order to solve the problem that the height of the blowout liquid column is difficult to measure after the blowout accident,a method for measuring the height of the blowout liquid column based on image processing technology is established in this paper.Use aerial photography or rescue boat to transiently image the blowout column of the accident well,process and identify the blowout column in the blowout accident image by image processing technology based on Open CV computer vision library,and calculate the blowout column according to the reference method Actual height.Using this method,the disturbing pixels in the image can be effectively eliminated,and the image of the blowout liquid column can be completely extracted from the blowout accident image with complex background,and the height of the blowout liquid column can be calculated.After obtaining the height of the blowout liquid column,the theoretical calculation model of wellhead pressure and wellhead speed based on the height of the blowout liquid column under pure liquid phase was established based on the jet principle,and experiments were designed to verify.Combined with the experimental results of jet flow,the influence of jet pressure,jet flow rate,jet liquid viscosity,jet liquid density,and gas content on the height of jet liquid column was analyzed.Finally,the gas phase continuity equation,liquid phase continuity equation and gas-liquid mixed momentum equation in the wellbore annulus are established.Using the finite volume method and the staggered grid method,the wellbore space is discretized.The gas intrusion amount is calculated by the formation productivity equation or other working conditions and combined with the wellhead pressure value.The partial differential equations and related auxiliary equations are solved using the AUSM+ format,and the transient flow parameters of the gas-liquid two-phase flow in the wellbore annulus are calculated.Using this method,the gas-velocity,liquid-phase velocity,gas-containing rate,and bottom hole pressure of the wellbore nodes can be obtained with time.