Pressure survey, analysis and diagnostic of small diameter velocity string to improve well monitoring and surveillance

Abstract

In order to survey the pressure in the well with the small size velocity string (VS), and explore the pressure loss and flow regime in VS. Conventional slick line pressure survey tools are designed to smaller size, then perform pressure survey for VS. Compare and analyze the pressure gradient curves of gas wells with conventional production string (GWCV) and gas wells with velocity string (GWVS), obtain the root cause of the differences between them. The results show: (1) the upper half of the flowing pressure gradient curve of GWVS shifts to the right as compared to GWCS; (2) For the upper half curve, the flowing pressure drop of GWVS is not even, the decline rate gradually increases, and the curve is upper convex shape; (3) For the lower half of flowing pressure curve of some GWVS, the pressure value of some points decreases with the depth increases; (4)1 in 13 VS wells face with liquid loading and deliquification performance of VS is excellent. This study provides a new idea of pressure survey for small-sized VS, explores the difference and root cause between the pressure distribution of GWVS and GWCS, and improves the basic theory of velocity string deliquification.