SHANA — Iran hopes to bring its oil output to over 5 mb/d under its 20-year vision plan through investing in ageing fields. Some of oil fields in Iran are already mature. Their oil has partly been recovered, but cutting edge technologies are needed to extract the remaining oil.
Thanks to existing technologies, it would be possible to raise oil recovery rate from different reservoirs to over 80%.
One of reservoirs that Iran has specifically counted on is Bangestan in the Mansouri oil field. Mansouri was among fields proposed for development under the Iran Petroleum Contract (IPC) model, the restructured model of oil contract.
Over recent years, production from the Bangestan reservoir of Mansouri has been studied by Committee of Advisors at the Directorate of Reservoirs of National Iranian Oil Company (NIOC).
According to NIOC Directorate of Corporate Planning, various scenarios envisaged for enhanced recovery from this field include natural depletion, gas injection and water injection with a view to studying various parameters including output flow and downhole pressure.
This field enjoys very good potential for production and development. More studies are needed in the future to study the Bangestan reservoir of Mansouri field. These studies focus on artificial lifting, hydraulic fracturing and enhanced oil recovery (EOR) methods.
Iran’s petroleum industry, particularly National Iranian South Oil Company (NISOC), over recent years, has focused on the development of Mansouri in order to increase its crude oil output and enhance its processing capacity. The project is 97.5% complete now. The only remaining section from phase 1 of Mansouri field development is the completion of production and desalination plant.
The high rate of recovery from Mansouri has added to the significance of this field. The latest studies indicate that the average rate of recovery from oil fields in Iran is about 28%, while the Asmari reservoir of Mansouri has a recovery rate of 47%, which is indicative of the high potential of this oil field.
The Mansouri field is located 60 kilometers south of Ahvaz (the provincial capital of Khuzestan), 50 kilometers west of Mahshahr Port and 40 kilometers east of Ab Teimour field. Discovered in 1963, Mansouri field started production in 1973.
The first well in the Mansouri field was drilled in 1963 to allow for oil recovery from the Asmari reservoir. Oil production from the Bangestan reservoir began in 1974 after drilling Well No. 2.
After the establishment of the Mansouri production unit in 1979, the processing of the Bangestan oil was transferred from the Ahvaz production unit to the Mansouri production unit.
The Mansouri field is administered by Karoun Oil and Gas Production Company that is the largest subsidiary of NISOC with an output of over 1 mb/d.
The Bangestan reservoir has a production unit with a rated capacity of 75,000 b/d, a desalination unit with a rated capacity of 35,000 b/d and a gas compressor unit with a rated capacity of 30,000 b/d.
Bangestan is estimated to hold 15 billion barrels of oil in place with an output of 60,000 b/d that may be increased to 79,000 b/d. So far, 347 million barrels of oil has been extracted from the Bangestan reservoir.
The average production rate from each onshore oil well has fallen to 2,000 b/d, down from 26,000 b/d recorded between 1970 and 1972. There were a total of 270 wells when Iran was supplying its maximum oil output. There are currently over 1,500 oil wells.
According to the official data, the average oil production rate in Iran stands at 24%, while in many countries it varies between 45% and 65%.
Iranian Petroleum Ministry officials say the average recovery rate from oil fields in Iran stands at around 24%, ranging from 7% in Soroush oil field to 35% in Ahvaz oil field.
Iran targets Maximum Efficient Rate (MER) which means the maximum sustainable daily oil or gas withdrawal rate from a reservoir which will allows economic development and depletion of that reservoir without detriment to ultimate recovery.
If oil is extracted from a reservoir at a rate greater than the maximum efficient rate of recovery, then the natural pressure of the reservoir will decline resulting in a decrease in the amount of oil ultimately recoverable.
MER is also commonly used to denote the rate of field production that can achieve the maximum financial return from the reservoir operation. However, the figures of two rates hardly coincide.
In the 1940s, the average production from Iranian oil wells was said to stand at 18,000 b/d. After so many years, the figure is down to 2,000 b/d.
As Iran’s oil wells enter their second half of life, between 330,000 and 350,000 barrels per year of oil is lost in onshore wells.
Therefore, enhanced recovery from mature reservoirs like Bangestan is essential for Iran’s petroleum industry.
Output Hike Possible at Salman
Salman oil field located in the Persian Gulf is jointly owned by Iran and the United Arab Emirates (UAE). The shared offshore field has high-pressure gas layers, too. Discovered about 45 years ago, the Salman field has since been supplying oil.
It is located in Hormuzgan Province and more specifically 144 kilometers south of Lavan Island.
Due to the existence of about 70% of oil and gas layers of this oilfield in Iran’s territorial waters and its shared status, its development has always been a priority for Iran’s petroleum industry. In the 2000s the platforms of this field that had been damaged during the 1980-1988 imposed war were renovated.
A couple of years ago in Tehran, the Iran Offshore Oil Company (IOOC) nominated Salman along with the Norooz, Dorood, Foroozan and Soroush as candidates for development under the newly developed contractual framework known as the Iran Petroleum Contract (IPC).
In compliance with the Petroleum Ministry’s policy of prioritizing development of jointly owned fields, Salman is the most important of the five fields for development.
Given the history of oil production in the Salman field, it seems that the main objective of Iran’s petroleum industry in such ageing fields as Salman has been to apply cutting edge technology for maximum efficient recovery and enhancing the rate of recovery from these fields.
Despite the high recovery rate in the Salman field, some layers of this field have yet to be depleted. Therefore, it is possible to increase output from this mature brownfield.
Salman contains light crude oil with API gravity varying between 33 and 37. Renewed development of the Salman field allows for increased output. If enhanced oil recovery (EOR) methods are applied, a much higher output is envisioned.
The Salman field incorporates an asymmetric anticline measuring 14 kilometers long and 11 kilometers wide. Geologically, it is composed of three oil production layers dating from the Jurassic and Cretaceous eras.
The Salman field also incorporates a gas layer.
The field was discovered in the 1960s by Lavan Petroleum Company. The first exploration well in this field was drilled in 1956 to allow for production three years later.
According to the latest data, the field has 44 oil and 10 gas wells. Based on studies currently under way, gas production from Salman could rise after making some arrangements.
The field is owned 67% by Iran and 33% by the UAE. There is not precise figure about gas production from Salman whose rate of recovery stands at 51%.
The oil extracted from Salman field is carried to Lavan Island via a subsea pipeline of 22 inches in diameter for final processing on onshore facilities and then exported or stored to feed the Lavan refining facility.
Despite being ageing, Salman still has an acceptable level of deposits. A timely development of this field would boost its output. Five platforms are currently operating in this field.
Courtesy of Iran Petroleum
Among the three reservoirs in Salman, the one located at a depth of 10,000 meters under seabed accounts for 70% of the Salman output. A layer located at a depth of 8,000 feet accounts for 20% of the Salman output and a third layer at a depth of 5,000 feet for 10%.
Salman is estimated to contain 4.5 billion barrels of oil in place. Since 1999 onwards, when a number of oil and gas fields were developed under buyback deals, studies on the Salman field were carried out under the supervision of Petroiran Development Company (PEDCO) and the Petroleum Engineering and Development Company (PEDEC).
The primary processing of crude oil is done on platform before being carried in a 144-kilometer-long pipe for secondary processing, storage and exports to Lavan.
Gas produced from the nine wells in this field is carried to Siri Island via a 36-inch pipeline.