Contaminated Gas - Past, Present and Future
Authors: Puik Eric , Braithwaite Colin Ian Martin 
Published: February 2016

In an age where there is increasing concern for safety and the environment, why is there such interest in developing gas resources contaminated with high concentrations of H2S and CO2? This paper traces the history of contaminated gas production and explores the reasons why it has now become a focus for many countries.

The paper also addresses the significant technical, commercial and safety challenges that face developments of contaminated gas fields. In many cases, fields with high CO2 contamination cannot be developed economically without the introduction of new technology to both reduce costs and the amount of energy required to separate CO2 from methane, and then sequester it safely below ground.

For H2S contaminated gas fields, the challenges appear even greater. The extreme corrosiveness and toxicity of H2S requires the application of state-of-the art technology and operating procedures. There is simply no room for mistakes. sulfur management is also an issue that requires new approaches as planned developments will double globally traded volumes over the next ten year. The paper will outline the advantages and disadvantages of disposal options from blocking, Acid Gas Injection (AGI) and the application of new sulfur products such as sulfur cement (which is resistive to corrosive environments), enhanced asphalt (for hardwearing road applications) and sulfur fertilizer (with 15% greater yields). Indeed, the application of new sulfur technology has the potential to turn a global surplus of sulfur into valuable new products.

With many hundreds of tcf of contaminated gas resources worldwide, there is no doubt the industry will rise to the challenge and develop these resources in an economic and safe manner. But it will require the application of radical new technology and an integrated approach across the full value chain. It won't be for the faint hearted.

Disadvantaged resources

The volume of hydrocarbons discovered over the last 100 years shows a golden age in the 1960s and 1970s where over 600 Bln bbloe were discovered in the decades (see Fig. 1). During this time, many of the more difficult hydrocarbon discoveries were put to one side for later consideration. However, the progressive decline in new discoveries indicates that many of the world's major hydrocarbon basins have been discovered, and it is now getting progressively more difficult to find new and easy forms of conventional resources (see Fig. 2).

Fig. 1 Reserves addition per decade. Also indicated are some significant sour gas finds.

With demand continuing to increase, there is now a need to consider more difficult resources and hence more 'expensive to produce' resources. These disadvantaged resources can be categorized as follows:remote (far away from the market, no existing infrastructure),harsh conditions (artic),difficult reservoirs (ultra deep, tight formations) andunfavorable composition (heavy oil).

Contaminated gas fields are typically part of that last category. As reported elsewhere in literature, there is at least 350 tcf of natural gas in place with 10 % H2S or more, and 700 tcf with 10 % CO2 or more. This is roughly 15 % of the total gas still to be produced. The bulk of these resources can be found in the Middle East, the Caspian region, and the Far East. Considering less severe levels of contamination, even up to about 40 % of the total gas still to be produced can be labeled as contaminated gas. Obviously, these numbers are large enough to attract the attention of a wide range interested entities, from IOCs and NOCs to innovation centers like universities.