O. V. Nepomnyashiy, S. F. Ten, V. A. Habarov, L. A. Skotnikov

Among the known approaches to exploration of natural gas fields the most effective ones are to be express methods of surface gas leak detection. The special attention is paid to computer-aided aviation measurement of saturates concentration in the atmosphere, and also to instant detection of trace concentration of methane, ethane and propane, made afield. The principle of the performance of the developed hardware and software system depends on the method based on the methane capacity to selectively absorb laser radiation in the spectral region, that refers to the dispersion-free methods of absorption spectroscopy. It is known, that the methane absorption spectrum has a complex structure. The phenomenological mathematical model of description of such a spectrum band is proposed. While transmitting the optical signal, the radiation absorption occurs as the changing its flow. The radiation flow, made by a laser source. The input quantity of all optical receivers is a radiation flow, but not separate spectral components. As the outlet flow of the optical channel depends on the methane concentration, so the output signal on an optical receiver also depends on this feature. We consider the optical channel as a part of the metering circuit, with the transfer characteristic. Dependence of methane concentration of flow quantity has been formulated. Radiation leakage in the open channel is not reduced to its absorption by methane. The essential part of the optical flow, commensurable with the absorbed one, will be scattered with the atmosphere dust at the location of measurement. To balance the dust component there are two optical channels in the software and hardware system - the one is standard, the other is measuring. The standard channel does not have radiation absorbing components. There are also two radiation sources. The one has a wavelength of 3.31 um (basic), the second has a wavelength of 3 um (assisting). Radiation flows from each radiation source are divided into two with the similar output. Each of them is passed through two optical channels. Thus, there are four beams entering the optical receivers, firstly passing through one and the same optical channel by pairs. Thus, the secondary channel and the developed data-takeoff algorithm help eliminate the influence of the scattering component (dust) in the open optical channel on the result of the methane concentration measurement. The use of the open optical channel considerably reduces the time of measurements, eliminating the distance-velocity lag, that takes place in such absorption spectrometric methane meters. The developed software and hardware may successfully be applied for remote (aviation) sounding to obtain data about concentration of saturates (methane, ethane, butane, propane) in the bottom layer.