In the oil and gas industry, reservoir pressures exceeding 10,000 psi and temperatures exceeding 300°F are categorized as high pressure and high temperature (HPHT) reservoirs1 . Testing and design for HPHT wells require special equipment and treatment, including the use of technology that can withstand high pressure, high temperature, H2S and high CO2 content.

S-3 gas well is a high deviated (inclination: 88°) well with open-hole completion. Pressure and temperature of S-3 well are estimated at 10,625 psi and 408°F respectively. Based on gas chromatograph analysis, the H2S content is around 100 – 250 ppm and CO2 content around 30%.

Due to low matrix permeability indication around S-3 (<5md), a Modified Isochronal Test (MIT) test was chosen for S-3 to shorten testing times. Pressure, rate and temperature were measured using surface recording equipment due to the availability of tools that meet pressure and temperature rating. Static reservoir pressure was predicted using Cullender and Smith method. Nodal analysis software and WHP vs BHP relationship from S-1 well is used to calculate IPR and Deliverability curve. Permeability and skin factor was estimated from drawdown analysis.

This paper presents the history and a case study of S-3 well testing, including planning, testing design, execution, data analysis, interpretation, and lessons learned from the well. This will be beneficial for designing the next well-testing and optimizing similar HPHT wells.

Finally, as a result of S-3 well testing, it was found that AOF from pseudo pressure function was around 155 MMscfd, kh 3315 md.ft, while the total number of skins was 29. There is also an indication of fracture occurrences around S-3.

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