Astrakhan, The World's Largest Sour Gas Development

Abstract

Abstract The Astrakhan Sour Gas Field located near the northern tip of the Caspian Sea in the U.S.S.R. is considered to be the largest of its type in the world. The difficulties associated with transporting an extremely deadly and corrosive fluid in an area characterized by extreme environmental conditions make the development of this field extremely challenging. This paper outlines how Lavalin addressed these challenges in the development of the second phase of the project. Introduction At approximately 9:00 p.m. on New Year's Eve, 1986, Lavalin signed a contract with Machinoimport for the development of the 2nd Phase of the Astrakhan Sour Gas Field in The U.S.S.R. While this was not the first contract ever undertaken by Lavalin in Russia, it was the first contract for a project under the urisdiction of the Ministry of Gas and followed more than ten years of proposal and business development activity and an expenditure of more than $3 million. At this time, the engineering is basically complete, all of the equipment is either in fabrication or has already been delivered, and construction at the site is now well under way. The project undertaken by Lavalin was for the complete development of the 2nd Phase of the Astrakhan Sour Gas Field. The Sour Gas Field is approximately a one-and-a-half hour drive away from the city of Astrakhan located near the northern tip of the Caspian Sea in the U.S.S.R. (Figs. 1 and 2). The project involved the collection of sour gas and condensate from a total of 83 wells and delivering to the Gas Processing Plant (later referred to as OPP) a volume of 6 billion m3 per year of sour gas. Development of Sour Gas Fields Developing sour gas fields is not a new concept and certainly one that people in Alberta are very familiar with. This project, however, was made increasingly more difficult by a number of factors. The first of these was that the gas is extremely sour, being consisted of approximately 24% H2S and 14% CO2 resulting in an acid gas component of approximately 40% of the total gas produced. In addition, produced with the gas are significant quantities of sour condensate and produced water. The produced water has a very high chloride concentration resulting in one of the most corrosive fluids you are likely to encounter in sour systems. Add to this the fact that the production comes from a very high-pressure reservoir with shut-in wellhead pressure of approximately 400 bars (near 6000 psi) and that the particular gas combination has a hydrate temperature above 30 °C and you will understand why this fluid is very difficult to handle. The problems, however, did not end with the fluid itself. In addition, there were extreme environmental conditions that must be considered in the design of the facilities. The field is located in a desert where the terrain is really nothing more than rolling sand dunes which change their shape and position dayby day as the winds blow.