Abstract

This paper describes integrated workover and re-completion techniques to successfully restore productivity of Saman gas reservoir, a carbonate reservoir with H2S (vol. 3.0%) and CO2 (vol.3.6%) in Turkmenistan. Using existing old wells that have ever been producing for 5 years and already shut-in for more than 13 years is an excellent and economical way to increase production with a small investment.

Lots of complex situations in the wellbore and safety challenges, such as unmanageable wellbore corrosion, casing leak, string fishing, re-completion etc., could be encountered for existing sour wells. As a special corrosion diagnostic technology, MIT/MTT logging was used to acquire the data of metal loss, casing damage profile and cross section for joint. Workover strategies were considered and the best one was selected for complexities of old gas producers. Bottom whole assemblies (BHAs), mainly composed by SSSV system, chemical injection value and permanent packer, and were designed to corrosion control and long-term production safety. Nodal analysis and hydrate prediction were applied to optimize gas production system. Matrix acidizing by using viscoelastic self-diverting acids was carried out to remove damage for existing old wells. These key workover were conducted successfully for 17 existing well, resulting in average gas production of 30.6MMSCF from original gas production of 14.1MMSCF, and a gas productivity of 1,589 billion SCF/y. Compared with drilling new well, Workover not only economize on cost, but also speed up the building of gas field capacity.

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