The expansion in recent years in the oil and natural gas sector has a profound implication for the continuous supply of energy in the market. There is no doubt a surge in the domestic natural gas production with tremendous opportunities as gas is used extensively for electricity generation. With the increasing energy demand, it is always a challenge to bridge the supply and demand gap. The era of sweet shallow gas is fast depleting and hence developing local sour gas production having higher concentration of hydrogen sulphide (H2S) and carbon dioxide (CO2), which are toxic and corrosive is seen as the viable solution.

Currently, ADCO took up a project to study developing the sour gas reservoirs. The objective of the appraisal program was to gain valuable reservoir data including PVT samples to finalize the facilities and full field development plan including testing the reservoir in an area where seismic data indicated better quality sweet spots.

The appraisal program was carried out and the major challenges to drill, test and produce the highly sour HPHT (High Pressure, High Temperature) gas were identified and mitigated. The data from the previously drilled wells penetrating the sour Arab zone was used to drill in the sweet spots identified but additional data was required to reduce the remaining key uncertainties to firm up the Gas In place volumes as the final results were crucial for strategical decisions.

This paper highlights the work progress and then the lessons learned during each step of the operation with the proposed mitigation to safely and efficiently drill the appraisal wells in the Arab sour reservoir having 37% H2S and 10 % CO2.

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