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 km 2 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.

The Orinoco Oil Belt (OOB) is located in the southern strip of the eastern Orinoco River basin in Venezuela, with a total area of 55,314 km2. This formation represents the largest heavy-oil reserves from unconsolidated sandstones in the world. Unfortunately, sand production is a common problem associated with this type of formation. In addition, it is very challenging to successfully remove solids and stimulate large, highly deviated wells with low bottomhole pressures. Since 1999, a technology combining concentric coiled tubing (CCT) with a jet pump has been used in the OOB to remove solids and fluids (stimulation treatments, drilling fluids, etc.) from the wellbore. Due to the characteristics of these heavy-oil wells, with their unconsolidated sands and highly deviated well paths, sand/well vacuuming technology (SWVT) has become the main alternative for intervention operations such as sand cleanouts, stimulations, drilling fluid removal, and any kind of job requiring the use of coiled tubing. Conventional SWVT permits changing the configuration of the tool into two modes: sand vacuuming for solids removal, and well vacuuming for fluids recovery. During SWVT operations, two main scenarios exists where it is necessary to change the bottomhole assembly (BHA) used with SWVT for a regular BHA with enhanced jetting, thereby requiring extra runs to finish the jobs.Breaking through hard bridges formed by sand and oil or by solid materials as elastomers from progressive cavity pumps.Pumping down chemical stimulations treatments. To overcome the issues resulting from cleaning and increasing efficiency with stimulations jobs in a single run (avoiding extra running of different BHAs), an improved SWVT with a jetting switch has been developed, incorporating a third mode: high jetting. In this mode the SWVT BHA can handle higher fluid rates and achieve the necessary impact pressure to break solids bridges or to perform stimulations jobs efficiently. This paper discusses the implementation of this tool in the OOB and explains the results in terms of efficiency increase and best practices for this type of intervention.

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