Coiled Tubing Velocity String Hang-Off Solves and Prevents Liquid-Loading Problems in Gas Well: Case Study in the Gulf of Guayaquil, Ecuador

Abstract

Abstract The Amistad field in the Ecuadorian Gulf of Guayaquil has been producing dry gas since 2002 from the productive formation Subibaja. This field covers an area of 2,250 km2 and is located offshore about 100 km southwest of the city of Guayaquil. Six wells in the field produce 60 MMSCFD and 940 BWPD. Gas production from this field is affected by water production and reservoir pressure declination. In particular, liquid-loading is considered a critical problem in the gas wells productivity, with water intrusion occurring in the wellbores during temporary shut-in for workover operations. A coiled tubing (CT) velocity string is a known method to unload liquids in gas wells; the correct choice of CT size may optimize gas well productivity. The smaller-diameter CT is installed inside the production tubing to improve gas velocity, thereby avoiding water column accumulation at the bottom of the well. The reservoir inflow performance relationship (IPR) and tubing performance relationship (TPR) are considerations in velocity string design. Both curves are independent and their intersection, compared with the minimum gas flow rate on a J-curve, indicates whether liquid loading will occur in a gas well. This paper discusses the technical concepts of velocity string design, as well as simulations and analysis for a case history of deploying velocity string technology in a gas well with optimal results.