Patent ID: 7158886
Filing Date: 2007-01-02
Classification: E21B

Abstract:
1. An automatic control system for bottom hole pressure (BHP) in underbalanced drilling (UBD) comprising a data acquisition unit, a data processing unit, a control and execution unit, and a data conversion and transmission unit, wherein: (1) the data acquisition unit comprises a dynamic modeling data acquisition module and a static data input module, the dynamic modeling data acquisition module including pressure sensors provided in a drilling operation system to collect standpipe pressure and casing pressure, and pump stroke sensors to collect pump strokes of the mud pump, the static data input module for inputting parameters including borehole structure, drilling tool configuration, mud property, and well depth through man-machine interface; (2) the data processing unit comprises a processing module for the BHP in the underbalanced drilling, the module processing parameters including all the dynamic and static data, and the BHP in the underbalanced drilling calculated from an acquired standpipe pressure (SPP), a calculated circulating pressure loss in the drilling tools, a drill bit pressure drop and a fluid column pressure in the drill string, the BHP calculated by deducting the circulating pressure loss in the drilling tools and the drill bit pressure drop from the sum of the standpipe pressure (SPP) and the fluid column pressure in the drilling tools, then the resulting BHP is compared with a set pressure of the system, and an instruction to regulate a throttle valve opening is issued when the BHP is higher or lower than the set pressure; (3) the control and execution unit comprising a throttle valve and a throttle valve control module, the throttle valve control module sending a control signal to the throttle valve to control the opening thereof when receiving an instruction to control the throttle valve opening from the data processing unit, to limit the BHP within the set pressure range in real time; (4) the data conversion and transmission unit for transmitting the dynamic modeling data and the static input data in the underbalanced drilling operation acquired in real time by the above mentioned data acquisition unit to the data processing unit, or transmitting the instruction of regulating the throttle valve opening to the control and execution unit.