METHOD OF DETERMINATION OF FORMATION PRESSURE IN COURSE OF DRILLING Russian patent published in 1999 - IPC

FIELD: oil and gas producing industry; applicable in construction of wells. SUBSTANCE: method includes lowering of drilling bit into well, pumping of drilling mud, determination of drilling mud volume and density, and penetration rate at current depth of well. Bit is lowered on drill pipes to cement sleeve to drill it out. casing shoe is drilled out and wells is drilled through length of downhole drill string assembly. In so doing, penetration rate is registered at depth of beginning of circulation loss and casing-wellbore annulus is sealed. In pumping of drilling mud into pipes, pressure at pumping is registered and graph of this pressure increment versus of mud pumped into pipes is constructed. Pressure of beginning of circulation loss is found on graph by point of deviation of graph line from straight line, and obtained value is used for determination of formation pressure at this depth. Then, pressure is released and drilling of well is started. Formation pressure at current depth is determined by mathematical expression. EFFECT: higher accuracy and on-line determination of formation pressure at current depth of well. 1 dwg