The question is to know what role gas compression platforms would play. The wellhead pressure required for the transfer of 1 bcf of gas onshore is normally 120 Bar. Now if this pressure falls to 100 Bar it would be difficult to transfer 1 bcf of gas. At 90 Bar pressure, only 700 mcf could be transferred. That would also result in production drop. That underscores the significance of gas compression platforms which would in the end help prevent a drop in production.

Output hike

Gas compression platforms at each phase of South Pars would mean multiplication of production from its gas wells. Therefore, the ability to design and build such platforms would be highly profitable for Iran in the future. According to some estimates, about 20 gas compression platforms are needed at South Pars in the future, thereby necessitating sufficient precision and sensitivity. 

NIOC is currently reviewing various models of such platforms both onshore and offshore. The platform needed to handle 2 bcf of gas should be 90 Bar.

Iran plans to build its compression platforms at its own yards, but since each platform weighs about 20,000 tonnes and in the absence of any experience of building platforms of over 7,000 tonnes, the required infrastructure in the country should be upgraded.

Sophisticated design, necessity of proper arrangement of equipment, safety and operational issues are among features of gas compression platforms whose installation requires the float-over method whose technology does not exist in Iran. Therefore, the basic and conceptual design of gas pressure compression platform needs to be done by an international consultant so that an effective model would be provided to Iran to be used in other phases of South Pars.

$20bn investment

Over the past three years, more than half of NIOC resources has been spent on South Pars projects in a bid to accelerate its phase development. However, investment is still needed particularly for constructing compression platforms so that Iran would not be outdone by Qatar. The head of Pars Oil and Gas Company (POGC) has said that $20 billion in offshore investment would be needed to preserve pressure at South Pars.

The existing yards at Iranian oil installations may not accommodate giant 20,000-tonne platforms, but with some fundamental changes they may serve other South Pars phases.

According to experts, due to the gas pressure decline in some South Pars reservoirs, this phenomenon will gradually extend to the entire field. It is necessary to examine measures to enhance the gas pressure before delivery to the refinery. Therefore, POGC has assigned the feasibility study project of using pressure compression platforms to Petropars, and while concluding a contract with an international engineering company/reputable consultant, Petropars is studying the optimal conceptual design of gas pressure booster. In this regard, various options are under technical, operational and economic investigation. These studies are being carried out on the platforms and the tank of SP12, and after summarizing the studies and choosing the best option by POGC, it will be extended to all the phases of South Pars field for standardization. The proposed options include enhancing the gas pressure offshore and onshore.

Given the 24 development phases and 42 platforms in South Pars, separate studies are under way for them with 1,000 and 500 mmscf/d capacity separately or 2,000 and 5,000 mmscf/d capacity jointly.

The installation and commissioning of pressure compression systems will provide the possibility of gas recovery from South Pars field for about twenty years. In the design of pressure compression platforms, the existing facilities for installation and transportation and the construction of internal contractors have been considered. Although platforms of up to 7,000 tonnes have been built and installed inside the country, domestic contractors may develop the mentioned facilities to reduce the costs and time of construction and installation of their yard.

Gas turbo-compressors are among the main equipment of these pressure compression platforms. The selection of their type has been investigated with an international manufacturer, and the maximum effort is to transfer the knowhow for manufacturing this equipment to Iran.

Currently, the conceptual design of these platforms is almost completed and it is expected that after the completion of the pressure compression platform studies, the obtained results to be submitted to POGC to finalize the final option for the basic design.

Substructure

Whereas the weight of pressure boosting platforms is 10 times the weight of most current platforms in Iran; therefore, there is no crane in the world to install a 20,000-tonne platform, and this work must be done floating, that is, the float comes between the jacket bases and the platform is placed on the jacket.

According to one of the experts, one of the fundamental measures to build pressure-boosting platforms in Iran is to design the facility yard by a foreign professional consultant, because the cost of each platform is $2.5 billion and one cannot take risks about it.

According to him, Iran has no history of designing and building platforms of this size, and if it acquires the technology to build such platforms, it may export it in addition to meeting domestic needs. On the other hand, high-pressure sour gas compressors must be installed on the platforms, which NIOC intends to transfer the technical knowhow of making these compressors to domestic manufacturers with the measures it takes, in which case sour gas compression platforms may be envisaged.

Options

Various options have been considered to boost the pressure in South Pars. Among other things, for each South Pars platform, a pressure compression platform specific to that platform should be installed, which, of course, considering that there are 38 well platforms in this field, therefore, the installation of pressure platforms will costa fortune. Another option is to install the complexes of pressure boosting platforms in the place of the field where the pipelines exit and close together, and in the process of boosting the pressure of a set of platforms, it is concentrated in one point. Based on this, three pressure boosting complexes are expected to be built offshore, in which case, each hub corresponds to 10 to 12 platforms. This option is expected to cost more than $20 billion.

In the two phases of South Pars, pilot projects are to be implemented, in the 11th phase of South Pars, pressure boosting platforms are to be built in the sea, in the other phase of South Pars, pressure boosting compressors will be installed on land and pressure boosting operations will be carried out. Of course, the second plan is still in the study stage, if the result of the second plan is positive, it could be developed or even a centralized complex could be built in Pars 2 and many compressors could be placed in this complex. The gas of the phases that face a pressure drop is transferred to this complex, and after boosting the pressure, it is transferred to the respective refineries with inter-refinery lines, and then the produced gas is connected to the national network.

Pressure of the gas that is to be transmitted to the refinery must not be less than a certain figure. For example, if the gas pressure on the platform is 130 Bar, this pressure onshore must reach 95 Bar. We must have a compressor that takes the sour gas and increase its pressure and then transmit it to the refinery; therefore, the material of the turbo-compressors used in the project must be resistant to the sour gas.

South Pars is one of the largest gas reservoirs in the world, jointly operated by Iran and Qatar. With 14.2 tcm of gas, it holds about 8% of world’s total gas reserves. Iran is currently recovering 705 mcm/d of gas from its own section.

Iran Petroleum