Method for determining properties of a hydrocarbon reservoir formation and produced fluids in the process of production

Abstract

An acoustic signal is recorded at least once, the signal being a response of a wellbore-reservoir system onto acoustic impulses of pressure. A source of the pressure impulses is an electric submersible pump located inside the wellbore. The acoustic signal is recorded at least once by at least one sensor placed in a bottomhole chamber of the wellbore, the sensor measuring at least one physical parameter of the wellbore-reservoir system, which characterizes a process of propagation of the acoustic signal in the wellbore. A mathematical model of propagation of acoustic signals in the bottomhole chamber is created and data obtained by means of modeling are compared with data obtained by means of registering of the acoustic signals. Parameters of the reservoir formation in the mathematical model are adjusted in order to provide for consistency of at least one quantitative physical characteristic of the wellbore-reservoir system obtained by means of modeling with the same quantitative physical characteristic obtained by registration, and properties of the reservoir and of the produced fluids are determined as parameters providing for consistency.

What is claimed is: 
     
         1 . A method for determining properties of a hydrocarbon reservoir formation and of produced fluids, comprising:
 registering an acoustic signal at least once, the acoustic signal being a response of a wellbore-reservoir system onto acoustic impulses of pressure whose source is an electric submersible pump located inside the wellbore, and the acoustic signal is registered by at least one sensor placed in a bottomhole chamber of the wellbore and measuring at least one qualitative physical characteristic of the wellbore-reservoir system, which characterizes a process of propagation of the acoustic signal in the wellbore;   creating a mathematical model of propagation of the acoustic impulses of pressure in the bottomhole chamber;   comparing data obtained by means of modeling with data obtained by means of registration of the acoustic signal, which is the response of the wellbore-reservoir system;   adjusting parameters of the reservoir in the mathematical model in order to provide for consistency of at least one qualitative physical characteristic of the wellbore-reservoir system obtained by means of modeling with the same qualitative physical characteristic obtained by means of registration, and   determining properties of the reservoir formation and the produced fluids as parameters providing for consistency.   
     
     
         2 . The method of  claim 1 , wherein the at least one qualitative physical characteristic of the wellbore-reservoir system is selected from the group consisting of pressure, a pressure derivative with respect to time, a component of velocity of the fluid, and a component of acceleration of the fluid. 
     
     
         3 . The method of  claim 1 , wherein two groups of sensors located close to each other are used, at least one sensor in the first group measures pressure or a derivative of pressure with respect to time or a combination thereof, in the second group at least one sensor measures velocity or acceleration of a fluid in the direction of a wellbore axis in a place of measurement, the ratio of the spectrum of the first measured physical qualitative characteristic to the spectrum of the second measured physical quantitative characteristic is determined, the said ratio of the spectrum of the first measured physical qualitative characteristic to the spectrum of the second measured physical quantitative characteristic is used as input data for calculating a response function of the reservoir using the model of propagation of acoustic impulses in the bottomhole chamber of the wellbore, a set of response functions of the reservoir associated with a certain geometry of the reservoir formation and parameters of the medium of the formation is used for adjusting parameters of the reservoir formation in the mathematical model. 
     
     
         4 . The method of  claim 3 , wherein determining the ratio of the spectrum of the first physical quantitative characteristic to the spectrum of the second measured physical quantitative characteristic, the spectrum of the first measured physical quantitative characteristic is calculated for the first group of sensors and the spectrum of the second measured qualitative characteristic is calculated for the second group of sensors. 
     
     
         5 . The method of  claim 4 , wherein the calculation of the spectrum of the measured physical quantitative characteristic comprises processing the registered acoustic signal which includes presenting the signal as a linear combination of functions parameterized by a spectral parameter, with coefficients of a linear combination of the said spectrum. 
     
     
         6 . The method of  claim 5 , wherein the processing of the registered acoustic signal is made with the use of the discrete Fourier transform. 
     
     
         7 . The method of  claim 6 , wherein a preliminary processing of the registered acoustic signal is carried out. 
     
     
         8 . The method of  claim 7 , wherein the preliminary processing of the registered acoustic signal comprises exclusion of trends and removal of noises. 
     
     
         9 . The method of  claim 3 , wherein the ratio of the spectrum of the first measured physical quantitative characteristic to the spectrum of the second measured physical quantitative characteristic is calculated as a linear filter. 
     
     
         10 . The method of  claim 1 , wherein if the acoustic signal is registered more than once, a spectrum of the physical quantitative characteristic measured by the sensor is calculated for each measurement, changes in at least one parameter of the mathematical model are determined by f comparing the resultant changes in the spectra with the changes in parameters of the model. 
     
     
         11 . The method of  claim 10 , wherein the calculation of the spectrum of the measured physical quantitative characteristic comprises processing of the registered acoustic signal; presenting the signal as a linear combination of functions parametrized by a spectral parameter, with coefficients of the linear combination constituting the said spectrum. 
     
     
         12 . The method of  claim 1 , wherein a rotation velocity of a rotor of the electric submersible pump is varied at least once by varying a control input signal of the electric submersible pump, the spectrum of at least one measured quantitative physical characteristic is determined at a discrete set of frequencies on which amplitudes of the spectrum of the submersible pump have local maxima. 
     
     
         13 . The method of  claim 12 , wherein the rotation velocity of the rotor of the electric submersible pump is varied with the use of a variable speed drive. 
     
     
         14 . The method of  claim 12 , wherein variations in the rotation velocity of the rotor comprises frequency modulation of the rotation velocity of the rotor by a modulating frequency. 
     
     
         15 . The method of  claim 12 , wherein the rotation velocity of the rotor of the electric submersible pump is varied several times with a set of different modulating parameters in such a way that spectral maxima of the rotation velocity of the rotor cover a frequency range. 
     
     
         16 . The method of  claim 15 , wherein the variation in the rotation velocity of the rotor comprises frequency modulating in which a variation in the modulating parameter results in the spectral maxima covering the range:
   ( v   sh   −nv   mod   ,v   sh   +nv   mod ),   where v sh  is the rotation velocity of the rotor of the electric submersible pump,   v mod  is the modulating parameter,   n=1, 2 . . . .   
     
     
         17 . The method of  claim 1 , wherein pressure or its derivative with respect to time, or a combination thereof, is measured by at least one sensor, phase velocity of the fluid filling the bottomhole chamber of the wellbore is determined by means of correlating resonance and anti-resonance frequencies of at least one quantitative characteristic to the corresponding frequencies of the mathematical model, and a volume ratio of a gas is determined, which includes the ratio of a volume occupied by the gas to a total volume of the fluid, by means of correlating phase velocity of propagation of the pressure impulses determined at a given pressure with a phase velocity predicted with the use of the model. 
     
     
         18 . The method of  claim 17 , wherein a change in the volume ratio of the gas is determined qualitatively by means of observing simultaneous decrease or increase of resonance or anti-resonance frequencies. 
     
     
         19 . The method of  claim 1 , wherein the acoustic signals registered by the sensors measuring at least one quantitative physical characteristic of the wellbore-reservoir system are subjected to processing in the wellbore in such a way that information about quantitative or qualitative behavior of the physical quantitative characteristics is developed by means of such processing and either is transmitted to the surface with the use of a telemetry link or is stored in a memory for subsequent readout in the future.