Pressure reduction has gradually started in South Pars Gas Field Phase 12 and could extend other phases within five years, managing director of Pars Oil and Gas Company said Sunday.
“Despite peak production (680 million cubic meters per day) from the field, decks 12A and 12C will be decommissioned by March 2021 and installed in the adjacent Phase 11,” Mohammad Meshkinfam said, ILNA reported.
Depending on geological features of the reservoir, the pressure is expected to decline by 28 mcm per year on average in different phases by 2021.
Contrary to the general perception, the field will not be able to produce 680 mcm/d (current output) forever and this clean resource should be used as frugally as possible, he stressed.
“Pressure will fall sooner or later. Nevertheless, development of other gas fields in the Persian Gulf including Kish, Ferdowsi, Farzad A, Farzad B, Belal and Golshan can help compensate for the reduction."
According to the official, in South Pars reservoir system which has no water drive, gas expansion is the primary drive mechanism to move hydrocarbons to the wellbore.
Referring to reasons behind early pressure reduction in Phase 12 (compared to other phases), he said the main reason is that South Pars gas reservoirs are heterogeneous formations whose organic content, natural fractures and other properties vary one place to another.
Thickness of the reservoir walls in the phases located in the middle of the field (Phase 9, 10, 20, 21) help transfer gas to the wellbore for longer periods. But other phases (namely 17, 18, 14 and 12) are in the corner of the field and reservoir walls are thinner and gas pressure declines faster than other phases, he said.
Installing special platforms and compressors can also help increase pressure, but to do so in all the phases, each needs approximately $1 billion.
“Qatar's excessive gas extraction from the field has reduced the pressure extensively. Further lowering of pressure will affect production from the operating platforms in the near future.” Reservoir pressure in SP was higher when the first wells were drilled in 2001, he recalled.
Referring to Phase 11, he said the drilling rig of the phase will be put on its jacket in a few weeks and drilling will begin in June.
Phase 11 is scheduled to be developed in two integrated and consecutive stages. Each stage will contain 15 wells and produce 56 million cubic meters of gas per day plus 75,000 barrels of gas condensate
Substantial Improvement
The field's daily production (680 mcm) has risen by 126% compared to 2013 when output was 300 mcm.
"There were 11 platforms in SP in 2013, but the number has reached 36, up 227%," he said, adding that the number of onshore refining units is up 150%, increasing from 20 in 2013 to 50 in 2020.
Gas production capacity has reached 900 mcm/d, of which 680 mcm/d comes from South Pars and the rest (220 mcm/d) is produced by the Iranian Central Oil Fields Company that has three subsidiaries, namely West Oil and Gas Production Company, East Oil and Gas Production Company and South Zagros Oil and Gas Production Company.
Depending on the season, between 350 mcm and 600 mcm is consumed per day.
More than $80 billion has been invested in the field since 2001 when the first well was drilled. South Pars constitutes 96% of liquefied petroleum gas, 100% of ethane and 55% of sulfur produced in Iran.
POGC, a subsidiary of NIOC, oversees the development of the major gas field. South Pars is divided into 24 phases, all but Phase 11 are up and running.
The giant SP field off the Persian Gulf straddles the maritime border between Iran and Qatar. It spreads over 9,700 square kilometers, of which 3,700 km is in Iran. The Iranian side contains an estimated 14 trillion cubic meters of gas and 18 billion barrels of condensates.
Natural gas accounts for 75% of the country's energy basket.
Caption: Gas production capacity has reached 900 mcm/d, of which 680 mcm/d comes from South Pars.
