Oman, 2?? Velocity Strings in Deep and Tight Gas Wells

Abstract

Abstract In Oman, many of the gas reservoirs are deep and rich in gas condensate. The deep gas reservoirs require multiple fraccing to enable economical production. The gas and condensate production of the deep gas field described in this paper started in 1999. Since 2007, liquid loading is becoming a growing issue at current flowline conditions. Although compression is scheduled in 2010, some wells still require smaller tubing sizes to enable stable gas production. At current 9,000 kPa flowline conditions, the gas wells start liquid loading in the region of 160 −190 e3m3/d. The installation of a velocity string (VS) stabilizes the gas and condensate production in wells producing < 200 e3m3/d to as low as 50 e3m3/day. As the production life cycle is extended, velocity strings will increase the ultimate gas recovery. In the year 2008/2009 five VS were installed. Production data is available and helps in understanding liquid loading and the modeling of multi phase flow behaviour in deep gas wells. The installation of VS in the Oman Deep Gas field is challenging with respect to its great depth and materials being used. The first VS was installed in a live well in September 2008. Under-balanced installation was identified to be crucial in preventing formation damage in depleted and low rate wells. Some crucial lessons were learnt and solutions were found for all technical and operational challenges. The VS exceed a depth >4500 mTVD and have ~100,000 lbs string weight hung-off on a single retrievable packer system. It was also the first CR13 P110 string ever been snubbed into a live well. This paper describes the first VS trials done in Oman deep gas field, the inflow/outflow modeling and the main operational challenges encountered.