Abstract
Gas dehydration is a very frequent occurrence and a critical part of gas production offshore as well as onshore and therefore all the pertinent issues such as degree of dehydration, costs, design and operating "dos and don'ts" must be very well understood by the surface engineers as well as operators and managers. In the Middle East gas dehydration is particularly critical because of high reservoir pressures and high H2S/CO2 (sour gas) content and yet billions of cubic feet of gas are dried daily for gas injection or for downstream industry. But is the practice of gas drying in Middle East technically and environmentally adequate and safe?. If the water removed is not sufficient, liquid water is formed as pressure is dropped aiding line corrosion and upon further pressure reduction hydrates will form potentially blocking the flow lines. On the other hand extraction of too much water will cost the operator dearly and with the fluctuations in oil prices, revenues should be wisely used. The governing case which determines the degree of drying is the coldest operating condition for which the process gas may be subjected which means the degree of drying is a variable itself during the reservoir life and may be relaxed (or visa versa) as the reservoir life progresses and these are discussed in detail in this paper. There are various correlations used to arrive at the degree of drying and each give different results. In the proceeding paper, a range of credible dehydration methods are summarized with special emphasis on gas dehydration by TEG method as it is widely used and the salient points especially environmental issues related to the release of BTEXs into the atmosphere and how to minimize them. Various sets of correlations for dew point determination are demonstrated with real offshore case data together with unique and valuable recommendations on the design and costs optimization as well as technical/environmental safe operation.
