Abstract: Systems and methods for measuring flow velocity of a fluid mixture in a lateral section of an oil/gas/water well with a dual beam laser doppler velocimetry (LVD) based flow sensor are presented. According to one aspect, the flow velocity is measured by tracking movement of particles and/or features in the fluid mixture while traversing an interference pattern generated by the intersection of two separate coherent beams that are perpendicular to a direction of the flow. Flow velocity is derived based on a time it takes the particles to traverse consecutive fringes of the interference pattern as indicated by intensity peaks detected at the photodetector. The LDV-based flow sensor may be rotatable to measure flow velocities at different angular positions of a pipe in a lateral section of an oil well, rotation provided by rotation of an element of a mobile vessel to which the flow sensor is rigidly coupled.