Method for mirror imaging of gas holdup in gas-water two-phase flow based on fiber optic probe array

A method for mirror imaging of gas holdup in gas-water two-phase flow based on a fiber optic probe array, comprising:

• projecting six fiber optic probes of a flow imaging tool (FIT) onto a cross-section of a wellbore at a same height, gridding and normalizing an inner diameter of the wellbore and positions of the six fiber optic probes to obtain a cross-sectional grid, and determining a two-dimensional coordinate of each of the six fiber optic probes within the cross-sectional grid and a local gas holdup at the two-dimensional coordinate of each of the six fiber optic probes;
• rotating, based on a radial symmetry of gas-water flow along a center of the wellbore, the six fiber optic probes counterclockwise by n° around the inner diameter of the wellbore for
• (
• 360
• n
• -
• 1
• )
• times to obtain mirror probes, and obtaining coordinates of the mirror probes, wherein positions of mirror probes obtained by a final rotation differ from the positions of the six fiber optic probes by (360°−n°) respectively, the mirror probes are radially symmetrical, and a number of the mirror probes is
• (
• 360
• n
• ×
• 6
• -
• 1
• )
• ;
• and
• predicting, based on the two-dimensional coordinate of each of the six fiber optic probes and the local gas holdup at the two-dimensional coordinate of each of the six fiber optic probes, a gas holdup at the coordinates of each mirror probe of the mirror probes to obtain predicted gas holdup values of the mirror probes, interpolating the predicted gas holdup values of the mirror probes in the cross-sectional grid by using an interpolation algorithm to obtain a reconstructed gas-water image of the cross-section of the wellbore;
• wherein the projecting six fiber optic probes of a FIT onto a cross-section of a wellbore at a same height, gridding and normalizing an inner diameter of the wellbore and positions of the six fiber optic probes to obtain a cross-sectional grid comprises:
• projecting each of the six fiber optic probes of the FIT onto the cross-section of the wellbore to obtain six projection positions which are non-uniformly distributed, using a line formed by connecting the six projection positions as an X-axis, a perpendicular line to the X-axis as a Y-axis, and the center of the wellbore as a coordinate origin, and gridding and normalizing the cross-section of the wellbore to obtain the cross-sectional grid, wherein the cross-sectional grid comprises coordinate data for each grid cell;
• and
• wherein calculation formulas of the two-dimensional coordinate of each of the six fiber optic probes within the cross-sectional grid are as follows:
• l
• i
• ′
• =
• l
• i
• ×
• cos
• ∂
• x
• i
• =
• ❘
• "\[LeftBracketingBar]"
• d
• 2
• -
• l
• i
• ′
• D
• ❘
• "\[RightBracketingBar]"
• where li′ represents a distance from a projection point of an i-th fiber optic probe of the six fiber optic probes to a bottom of the FIT, li represents a length of a part of an arm of the FIT from the i-th fiber optic probe to the bottom of the FIT, ∂ represents an opening angle of the FIT, D represents the inner diameter of the wellbore, d represents a normalized inner diameter of the wellbore, and xi represents the two-dimensional coordinate of the i-th fiber optic probe.