Transient Aspects of Unloading Oil and Gas Wells With Coiled Tubing

Abstract

ABSTRACT Unloading oil and gas wells with coiled tubing (CT) conveyed nitrogen circulation is a transient process in which the original heavier fluid in a wellbore is displaced by nitrogen and lighter reservoir fluid. The transient aspects need to be considered when determining nitrogen volume and operation time for unloading a well. A computer wellbore simulator has been developed and used to study the transient effects. The simulator includes transient multiphase mass transport and takes into account the different fluids in the wellbore and from the reservoir. The simulator also includes the gas rise in the wellbore liquid below the CT and can be used for gas well unloading. The transient results of oil and gas well unloading are presented. The effects of CT size and depth, workover fluid, and nitrogen rate and volume on unloading are discussed. Unlike continuous gas lift, the total gas volume needed and the operation time in an unloading process can only be determined and optimized based on a transient analysis.