METHOD FOR SEISMIC EXPLORATION WHEN SEARCHING FOR HYDROCARBONS AND SEISMIC SYSTEM FOR REALISING SAID METHOD Russian patent published in 2011 - IPC G01V1/00 

FIELD: physics.

SUBSTANCE: in the disclosed engineering solution, determination of the dispersion curve of microseismic waves typical for the investigated territory is carried out via synchronous detection of microseismic signals using not less than three seismic station by picking up seismic noise at frequencies 0.008-20 Hz at the water-soil boundary, wherein odd harmonics 0.003 and 0.005 Hz are picked up from the spectrum of horizontal components and even harmonics 0.002, 0.004, 0.006 and 0.008 Hz are picked up from the spectrum of vertical components; variation of the magnetic field is measured at frequencies 0.01-1.0 Hz, magnetic induction of the electromagnetic field at frequencies 1-200 Hz, the electric component of the electromagnetic field at frequencies 1-500 Hz, acoustic noise at frequencies 5-5000 Hz, hydrodynamic noise of the sea at frequencies 0.01-100 Hz in tectonic zones; based on the measured parameters, factoral analysis is performed at the levels of natural geophysical background and geophysical background by plotting a graph of amplitude of gradients of seismic, geodeformation, geochemical and hydrophysical indicators based on measurements which do not exceed 50-100 km in average latitudes of 8-10 km in high and equatorial latitudes respectively; short-term variation of the magnetic field caused by sea disturbance is also taken into account; magnetic survey errors are minimised by detecting the thin structure of magnetic irregularities and determining parameters thereof; arrival of a seismogenetic acoustic wave is determined from the value of the frequency shift of the scattered radiation. Detecting devices placed at a distance from the coastal area enable to analyse low-frequency components of the scattered signal using quasiharmonic high-frequency ship noise signals as reference signals, and detecting devices placed in the coastal zone enable to determine onset and direction of arrival of seismic waves via narrow-band filtration and spectral analysis of the waves through recursive Butterworth filters, wherein input filtration is carried out using recursive filters with integral coefficients, and signals with sampling frequency 100 Hz and lower are filtered with coefficients in form of floating point numbers; hydroacoustic signals are picked up using wide-band ocean-bottom seismographs with not less than three seismic channels, wherein signals are analysed using three independent detectors, and the detection signal is generated when signals coincide in at least two channels from three; spectral analysis is performed for volume waves with phases PP and S, and for Love, Rayleigh and Stonely surface waves; plotting the map of amplitude variations of the microseismic signal for each spectral frequency of spatial variations, as well as associating each obtained map with its corresponding depth is carried out by approximating the profile of the vertical relief relative the coastal line, and the basic spline used is a cubic spline with zero boundary derivatives, wherein construction of a two-dimensional spline - function is executed through the tensor product of one-dimensional splines; the measured base at the sea floor is formed by placing seismic receivers at a distance of not more than 5 km from each other to form an isosceles triangle in the underwater space, at the vertices of which seismic receivers are put. Seismic vibration receivers are placed in a shelf zone, along the line of the foot of the continental slope and along the axis of the perpendicular Gardiner lines on fault boundaries; detection of local structures with oil-and-gas bearing potential is carried out via seismic profiling using a mobile seismic station with multiple overlapping of reflecting boundaries. The seismic system for seismic survey which consists of stationary seismic receivers and a mobile multichannel seismometric module, each of which consists of a block of highly sensitive seismic sensors, a recoding module with a block of filters and amplifiers, a board of analogue-to-digital converters, digital-to-analogue converters, a computer, a GPS receiver, a power supply, a calibration unit, a unit for processing and analysing signals and spectral characteristics thereof, MathLab 6.0 or higher type software, is characterised by that it includes a floating apparatus, a flight device, a standalone ocean bottom seismic station, a near-bottom seismic station and a floating seismic station; the mobile seismic module is in form of a controlled underwater vehicle; the floating apparatus is fitted with an underwater probe; the recording apparatus of the seismic system additionally includes a methane detector, a hydrophysical module, an ocean bottom seismometre, a magnetic field sensor with a control unit, a penetrometre, a gravimetre, a pneumatic radiator, an ocean bottom pressure sensor, a hydroacoustic communication channel modem, a satellite communication channel modem, a spatial orientation unit, an acoustic Doppler measuring device for measuring flow contour and a unit for hydrochemical measurements.

EFFECT: high reliability of seismic surveys when searching for and exploring hydrocarbon deposits.

2 cl, 13 dwg