Research and application of distributed fiber optic monitoring technology in oil-water two-phase flow production profile testing

Traditional production logging techniques are greatly affected by intermittent liquid production in low flow rate and unstable production situations. And the commonly used turbine structure testing instruments are impracticable in complex conditions such as small diameter casings and wellbore fluids. In response to those challenges, a new optical fiber testing system combines traditional instruments with distributed optical fibers was developed. The system integrated fiber and power cores into an optical-electrical composite logging cable and features a sealed connector to achieve high-pressure insulation and separation of the optical and power units in the cable. Moreover, Technique to mitigate the effects of Fresnel reflection was used at the end of small-diameter optical fibers. The signal loss or distortion zone caused by the reflection was reduced to 3m. In addition, a testing process for optical and electrical integration system in casing tubing annulus was developed, allowing for simultaneous traditional logging and optical data acquisition in a single trip into the well. The new integrated logging technique has been applied; the accuracy of the optical fiber depth correction is less than 1.5m by using magnetic positioning curve to ensure accurate depth. Low-frequency Distributed fiber Acoustic Sensing (DAS) data was used to evaluate production profile of the well. The results from optic fiber were validate via traditional production logging data, indicating that fiber optic monitoring technology is feasible for evaluating production profiles of low-yield oil and water wells.