Patent EP-1988254-A2 (EP)
Inventor: IAKIMOV MIKHAIL NIKOLAEVICH
IPC: E21B49/08
Filed: 2006-12-27
Abstract: This invention relates to the devices used in the oil and gas industry. Disclosed herein is the use of a high resolution gas chromatograph in the borehole for borehole fluid type determination in real time mode. The Wireline Downhole Gas Chromatograph comprises a sample chamber with a piston position sensor, the chamber being connected through the sampling valve to the pipeline and through oil pump to hydraulic oil pressure compensation tank; an electric thermostat with a temperature sensor and a chromatograph tube installed inside the thermostat, one side of tube is connected in series through a rotating sample injector, a zeolite filter, a first check valve and a chromatograph isolating valve with a line connecting said sampling valve and said sample chamber, and the other side of tube is connected in series to a second check valve, a fraction detector, a sample portion cylinder and a second pressure gage, wherein said rotating sample injector is connected in series to a pressure reducer, a transporting medium valve, a compressed nitrogen cylinder and a first pressure gage; a bypass line with a bypass valve is connected in parallel to said rotating sample injector, said chromatograph tube and said fraction detector, and the electronic telemetry loop is connected to the output of said fraction detector. 
     Also disclosed herein is a Downhole gas chromatography method according to which the Downhole gas chromatograph device is lowered into the well to the required depth, and a hydraulic contact with the formation fluids is made; the formation fluids are injected by the pump; the pumping cycle is completed; the sampling valve is opened, and fluid from pipeline is taken into the sample chamber; the sampling valve is closed, and the chromatograph isolating valve is opened to supply the sample for analysis; at the same time the bypass valve is opened in order to wash the contents from previous samples or other unwanted fluids; the transporting medium valve is opened; the rotating sample injector is opened for introducing the fluid sample for analysis; the chromatograph valve is closed, and the sampling valve is opened for fluid supply from the sample fluid chamber into the pipeline; piston is moved by oil pump, the oil pump is stopped, and the sampling valve is closed upon the receipt of a piston position sensor signal; the sample separated in the chromatographic tube is analyzed with the detector; the transporting medium residuals and samples are supplied to the washing section; upon the completion of the analysis, the transporting medium valve is closed. In some embodiments of this invention, said Wireline Downhole Gas Chromatograph is installed in the vicinity of the Modular Dynamic Tester (MDT) bar in a way so that the formation fluid sampling point and the LFA module are at one side, and the pump module (MRPO) or other sampling equipment at the other; during formation fluid injection by the pump, the MDT device performs resistivity, temperature and pressure measurements, and the LFA readings are taken, and the injection cycle is stopped once the required purity is achieved.