METHOD FOR DETERMINING SPEED OF SOUND IN ANNULUS OF WELL Russian patent published in 2023 - IPC E21B47/00 

FIELD: oil industry.

SUBSTANCE: invention can be used in calculating bottomhole or reservoir pressure during well operation by determining the speed of sound in the annulus of the well. A method is claimed for determining the speed of sound in the annulus of a well, in which oil samples are taken from the well, the signal response time from the gas-oil contact (GOC) boundary and the PVT properties of reservoir oil are determined: mole fractions of reservoir oil components according to chromatography results, gas content, volumetric coefficient oil at reservoir pressure, density of oil and gas under standard conditions based on the results of a single degassing, saturation pressure, density and compressibility coefficient of reservoir oil based on the results of contact degassing and the molar mass of the heavy fraction of oil. Then, regression analysis is carried out to adjust the Peng-Robinson equation of state; determine the average temperature and average pressure of the annular gas; determine the component composition of the annulus gas using the equilibrium flash algorithm; determine the molar mass of the gas, the heat capacity of the gas at constant pressure and at constant volume; approximately determine the speed of sound in the annulus of the well; determine the approximate value of the dynamic level; calculate the average pressure of the annular gas p_av using the formula (6) given in the materials. Next, if the obtained average pressure value differs from the previous value, then the equilibrium flash algorithm is repeated with a new value of the average gas pressure until the new value and the previous one coincide with an accuracy of 0.001 bar. Then the pressure and temperature of the gas at the GOC point are determined; divide the annulus into a set of X equidistant points. At each point in the annulus, the gas temperature and pressure are determined. At each point, an equilibrium flash algorithm is carried out for the gas component composition calculated at the previous point in the annulus. The component composition of the annular gas, molar mass, heat capacity at constant pressure and at constant volume, and the derivative of pressure and density at constant temperature are determined at each point. Calculate the speed of sound at each specified point and determine the average value of the speed of sound υ_av over the entire annulus according to the formula (7) given in the materials.

EFFECT: increased accuracy of determining the speed of sound in the annulus of a well in the absence of data on the composition of the gas and without carrying out field measurements of the speed of sound.

6 cl, 7 tbl