Patent GB-1449857-A (GB)
Title: Formation-testing tool for obtaining multiple measurements and fluid samples
IPC: F15B11/16
Filed: 1973-12-07
Abstract: 1449857 Formation sampling tool SCHLUMBERGER Ltd 7 Dec 1973 [8 Dec 1972] 56739/73 Heading E1F A formation testing tool includes a pump operable to pressurise a hydraulic circuit to successively higher pressure levels to cause sequential operation of the components of a fluid admission assembly intended to isolate an area of a wellbore wall, establish communication with a formation of interest via the isolated area and then admit a sample of concrete fluid into the tool. In a preferred embodiment, the pump 110 and its drive motor 111 are installed in an accumulator 112 including a piston 115 responsive to the ambient pressure in the well, the pump delivering into set and reset lines 119, 120 having respective solenoid-operated valves 121, 122 which together with the motor 111, a by-pass valve 127, pressure switches 124-126 and other solenoid-operated valves 182, 188 referred to below are controlled from the surface via switches (33, 34). When the tool reaches a required downhole location, the switches (33, 34) are moved to a position at which they cause energization of the motor and initial opening of valves 122, 127 to allow the motor to run the pump up to its operating speed under no-load, valve 122 thereafter closing and valve 121 opening so that the pump can, pressurize the set line 119 to a value controlled by the pressure switch 124. At a first pressure level in the set line, the fluid acts on pistons in cylinders 51, 52, 55, 56 and on piston 64 to extend the back-up member 50, the sealing pad 53 and the probe 57 into contact with the borehole wall, the pressure at this stage also raising piston 105 to cause plunger 106 to establish a low pressure in line 101 and in passage 81 between valve 85 and valves 86, 87 controlling admission to sample chambers 31, 32. When the pressure in the set line then rises to a second level, valve 129 opens to release fluid from chamber 76 so that a valve plunger 67 in the probe then retracts to uncover filter 80 and align ports 71 with a passage 79 communicating with a chamber 78 around the filter, at which point well fluids entering passage 81 and hose 82 via valve 88 flow into chamber 78 and through the filter to wash away any mudcake which may have collected on the filter as the valve plunger 67 retracted. The pressure in the set line next rises to a third level at which valve 128 opens to permit pressurization of extension 154 of the set line thereby causing sequential closure of valve 88 and opening of valve 85 so that the portion of passage 81 between the valves 85, 88 and hose 82 is isolated from the wellbore and connected to the previously-depressurized portion of passage 81 between valves 85-87, so that any producible connate fluids in the formation penetrated by the probe will be inducted into passage 81 via the filter, the pressure in the passage 81 being monitored by sensor 179 which transmits a signal uphole to allow a determination to be made as to the magnitude of the formation pressure and the mobility of the connate fluids. The pressure signal will also provide an indication of whether the sealing pad is not sealingly contacting the wall. The pressure in the set line finally rises to a level at which switch 124 stops the pump, and at this stage, if an operator decides that a sample of the connate fluids should be taken, then the switches (33, 34) at the surface are moved to their next position to open solenoid valve 182 which in turn opens valve 86 to admit a sample to chamber 31, the chamber 32 either being held in reserve for the next operating cycle or being supplied with a sample at this stage by operating a further switch (185) at the surface to open solenoid valve 188 which in turn opens valve 87. Upon moving the switches (33, 34) to a further position, the pump is restarted to pressurize the reset line via valve 122, valve 121 being closed directly and valve 127 being closed once the pump is run up to speed. At this stage, pressure switch 125 is enabled and stops the pump when the pressure in the reset line reaches a level sufficient to open valve 131 to depressurize portion 154 of the set line, thereby causing valves 128 and 86, 87 to close. The switches (33, 34) are next moved to a 'retract' position at which they disable switch 125 and enable switch 126 which allows the pump to raise the pressure in the reset line to successively higher levels to reopen valves 88, 130, the latter then allowing the pressure in the reset line to retract the backup member 50, the pad 53 and the probe 57. The valve 85 is finally reclosed and the pump is stopped by switch 126, the, switches (33, 34) then being moved, to their off-position preparatory to retrieving the tool or moving it to a new position in the well where a further testing or sampling operation is to be conducted. If at any stage in a testing or sampling operation it is decided to abandon the operation, the switches (33, 34) are simply moved direct to the retract position, skipping through any intermediate positions.