Abstract
Slickline down-hole flow control devices are always subjected to forces created by differential pressure where they are setting in tubing.
The standard practice for retrieving a flow control device (e.g. Plug from landing nipple) is to equalize pressures prior any retrieving attempt.
Slickline operators are always focusing on a mechanical surface wire manipulation of down-hole tools and surface pressure gauge to monitor equalizing pressure, while they overlook the effect of influential down-hole conditions such as: fluid level, fluid gradient, gas segregation and phase changes which based on we can calculate and determine the actual equalizing pressure.
In some cases, the equalizing pressure could not be completed properly due to reservoir fluid behavior change while operating or sometimes equalizing ports might be plugged, therefore any retrieving attempt can lead to an unknown events such as:
Slickline tool string blown up due to differential pressure during retrieving plug from a landing nipple.
Slickline tool string blown up due to huge differential pressure created by asphaltenes bridge plug formation in the tubing.
Slickline toolstring blown up during a flowing gradient survey with a portable well test due to choke changes.
Slickline plug stuck in landing nipple, due to the hydrostatic pressure head acting on the plug.
Collection of a non representative single phase bottom-hole sample due to downhole phase change.
This paper will discuss the newly developed procedures (best practices) resulting from a meticulous study of downhole fluid behavior changes and their influence on slickline operations. These best practices allow slickline to reduce this risk to a controlled level and provide a high service performance at low cost. Case histories from Burgan & Magwa oilfields will be used to illustrate overlooked slickline job failure root causes and how best practices contribute in providing innovative low cost service options.
