BEHARRA SPRINGS—FAST TRACK DEVELOPMENT OF A SMALL GAS FIELD UTILISING MEMBRANE SEPARATION TECHNOLOGY

Abstract

The Beharra Springs gasfield was discovered in 1991 in EP320 in the northern Perth Basin. Two wells were drilled on the upthrown side of the Beharra Springs Fault and intersected a gas bearing sandstone near the top of the Early Permian Carynginia Formation. Dry gas flowed at 240 000 cubic m3 (8.5 MMscfd) through a (0.5") choke and at 660 000 m3 (23MMscfd) through a 14.3mm (9/16") choke respectively.

The gas field sited 1.6 km from the Dongara to Pinjarra WANG pipeline coupled with the market demand from large industrial consumers (Alcoa) provided the necessary components of a low cost fast track development of a relatively small gas deposit.

Following production testing trials, process screening studies commenced in May 1991.

Front end design activities commenced in August 1991 and by May 1992, some nine months later production of 15 terajoules per day (TJ/d) of pipeline specification gas flowed from the gas field to Alcoa in Pinjarra.

The $10 million gas processing and pipeline facilities include:

Low temperature dehydration facilities utilising gas expansion cooling (Joule Thompson effect) and heat exchange to reduce gas temperature to -15°cat eight MPa. (Wellhead pressure initially 26 MPa) to ensure the gas meets water and hydrocarbon dew point specification.

Semi-permeable membranes, made from thin films of polymer, to reduce the corrosive gases carbon dioxide and hydrogen sulphide form six per cent to 2.5 per cent and 10 ppm to 3.2 ppm respectively to meet pipeline specification. The membranes operate at 7.5 MPa.

The use of skid mounted process modules and technology utilising the pressure inherent in the gas field to avoid the use of large rotating equipment and process chemicals were the other essential components utilised in quickly developing the Beharra Springs gas discovery into an efficient gas production facility.