Deepwater Drilling in Iran
May 10, 2013 is marked in the history of Iran’s petroleum industry: Oil exploration in the Caspian Sea from what is today known as Sardar-e Jangal.
The existence of 2 billion barrels of recoverable oil with an API gravity of 38 degrees sketched out new horizons for Iran’s petroleum industry.
Immediately after proof of oil, exploration drilling operations started with the installation of Amir-Kabir Semi-Submersible Drilling Rig. After the second exploration well was flared off in this field, a new chance was identified for exploring hydrocarbon reserves in the Caspian Sea. After that, Amir Kabir Semi-Submersible Drilling Rig was moved to a new exploration position, known as Block 8-1.
Yousef Etemadi, director of exploration at Khazar Exploration and Production Company (KEPCO), said drilling in Block 8-1 means exploration of a new field in the Caspian Sea because the structure of this block is different from that of Block 6-2 where Sardar-e Jangal field is situated. KEPCO is in charge of exploration and recovery of hydrocarbon reserves in the Caspian Sea and its coasts.
Iran Petroleum invites its readers to have a glance at a review of hydrocarbon reserves exploration in the Caspian Sea.
Caspian Sea is known as the largest lake in the world. This land-locked lake houses numerous oil reservoirs. Geologists estimated that between 80 and 200 billion barrels of oil remain hidden across this sea. The oil-rich section of Caspian Sea starts from Absheron Island in southwest and continues as far away as Cheleken Island in southeast. The oil reservoirs encircle the Caspian Sea, stretching from the Republic of Azerbaijan to Turkmenistan.
History of Caspian Oil Exploration
Caspian Sea, in terms of oil and gas reserves, is divided into three sections: North Caspian Basin, Middle Caspian Basin and South Caspian Basin. In general, most of the offshore oil reserves are in the northern part of the Caspian Sea, while most of the offshore natural gas reserves are in the southern part of the Caspian Sea.
The salinity of Caspian Sea changes from the north to the south within a range of 1,0 to 13,5 parts per thousand. This difference is especially strongly present in the North Caspian. It is less obvious in other areas distinguished by self-relative homohalinity.
The isohaline 12,5% bending around the peninsula forms the ledge as if it moves more salty water masses to the east. This phenomenon is explained by freshening influence of the rivers' drain on the western coast of the Middle Caspian, which is allocated by branches of Main Caspian flow of cyclonic and anticyclonic directions.
The Middle Caspian Basin is home to mainly onshore oil deposits. The Middle Caspian Basin is divided into five regions.
Billions of barrels of oil have so far been proven to exist in the Middle Caspian Basin, with primary reservoirs consisting of Jurassic and Cretaceous rocks, while secondary reservoirs are found within the Tertiary.
Seismic data clearly illustrates that sediment thickness varies considerably from west to east, due to basin architecture and heterogeneities. In the deeper section from basement to base Jurassic, clear rift features can be seen; faulted basement blocks are present with deep graven infill of Triassic sediments. Evidence of compression and volcanism can be seen in this section through deep folds and strong amplitude seismic reflections within the South Mangyshlak Sub-basin.
Seismic data offshore Kazakhstan shows Jurassic strata directly overlying basement blocks, indicating areas where the Triassic is absent.
In the north, the mainly shallow water area forms part of the much larger North Caspian Basin which extends onshore some 400km to the north and east.
To the south of the Karpinsky Ridge - Mangyshlak Meganticline water depths increase dramatically and the geology also changes significantly. The area is structurally complex, being influenced by a number of tectonic events.
But, information about oil and natural gas reserves in the Caspian Sea dates back to ancient time. From 600 BC to 12 AD, Zoroastrians used to travel to Baku, located in Absheron Island in order to worship at a temple where a fire was burning all the time thanks to natural gas deposits hidden underground.
There is evidence showing that oil was a lucrative commodity in the 10th century. Throughout the 13th century, a large amount of oil was exported from Baku to other regions. The famous Italian merchant traveler, Marco Polo, refers to a large flow of oil in his description of Armenia, noting that a high number of camels was needed for carrying that amount of oil.
Industrial extraction of oil from the Caspian Sea Basin started in the 19th century, making up the bulk of oil extracted in the world. Following the collapse of the Union of Soviet Socialist Republics (USSR), each of breakaway republics moved to recover oil in their own section and after that, different estimates were presented of oil deposits in the Caspian Sea. Some believe that industrial recovery of oil from the Caspian Sea started in the Gulf of Baku in 1923.
The world's first offshore wells and machine-drilled wells were made in Bibi-Heybat Bay, near Baku, Azerbaijan. In 1873, exploration and development of oil began in some of the largest fields known to exist in the world at that time on the Absheron peninsula near the villages of Balakhanli, Sabunchi, Ramana and Bibi Heybat. Total recoverable reserves were more than 500 million tons. By 1900, Baku had more than 3,000 oil wells, 2,000 of which were producing at industrial levels.
Potential hydrocarbon reserves in the Caspian Sea have encouraged the littoral states to drill in the land-locked sea for recovering oil and gas. Like other littoral states, Iran has not hesitated to conduct drilling in the Caspian Sea waters. Evidence first emerged of hydrocarbon reserves in Gorgan and Gonbad-e Kavous in northern Iran. The first and the most important exploration activities in the Iranian coasts of the Caspian Sea were carried out in Alamdeh-Neka, Kheshtsar near Mahmoud-Abad and south of Qaemshahr.
From 1951 to 1978 and particularly after the formation of National Iranian Oil Company (NIOC), the first exploration well was spudded near Mahmoud-Abad. Up to 1970, 16 wells had been drilled near mud volcanoes. All these wells produced only natural gas and technical studies showed that continuation of these operations would be uneconomical.
In 1998, NIOC assigned seismic testing on 31,000 square kilometers of the southern part of the Caspian Sea to a consortium of Shell, Lasmo and Veba Oil.
Following the establishment of KEPCO in December 1997, this company was tasked with exploring, development and operation of oil and gas reservoirs in the Caspian Sea as well as in the three coastal provinces of Gorgan, Guilan and Mazandaran.
Exploration in Iran’s Caspian Section
In 1999 and 2000, the Shell-Lasmo-Veba Oil consortium was assigned a mission to study hydrocarbon deposits in the Iranian section of the Caspian Sea.
The three renowned companies established the South Caspian Study Group (SCSG) which concluded that the Iranian section was potentially rich in oil.
One of the objectives pursued by SCSG was to see if one could expect the existence of oil system (including source rock, reservoir rock and cap rock) in Iran’s Caspian Sea sector. After 10,000 kilometers of 2D seismic operations during 22 months, the feedback was positive.
The study group also reviewed data related to 26 wells drilled in Azerbaijan and Turkmenistan and compared the connection between the formations in wells drilled in Iran and in the two countries. Other activities of SCSG included geochemical study of oil leaks and examination of any similitude between these leaks and the source rocks in neighboring countries.
In the end, geological and geophysical studies laid bare 86 geological structures in the Caspian Sea with 46 of them in better conditions. Eight of them were picked as prioritized structures for exploration and production studies.
Iran’s Deepwater Drilling Success
Drilling in deep waters is totally different from drilling in shallow waters and onshore drilling. Since a few countries have already acquired the technology to drill in deep waters, Iran’s adhesion to this group is considered as a big success.
When the issue of drilling exploration well and more specifically drilling in Caspian Sea deep waters is at stake, it would be impossible to fix any specific period of time for drilling because for example drilling of the first well in Sardar-e Jangal field was hindered by such phenomena as saltwater blowout and gas blowout.
The employment of ROV underwater robot which is widely used in deepwater drilling is a specification of deepwater drilling.
New Exploration
During 2010 to 2014, two exploration wells have been drilled in the deep waters of the Caspian Sea. The first well was completed in 2012.
Explaining about the results of exploration in the first block of the Caspian Sea, Etemadi said: “In the first block, known as 6-2, two wells have been drilled and both have had positive results.”
The second exploration-appraisal well in this block was spudded up to a 3,500-meter depth.
Noting that the data obtained from the second well confirmed the data of the first well, Etemadi said: “Although the second well was some 1.5 kilometers away from the first well, the data we had obtained in the preliminary exploration from the Sardar-e Jangal reservoir was confirmed in the drilling of the second well.”
He said that the drilling of the second well is over and the Sardar-e Jangal has no extra exploration work. He added that new investment is to be attracted for the development of this field.
Etemadi said Iran is continuing its exploration activities in the Caspian Sea and is moving Amir Kabir Drilling Rig towards Block 8-1. He said KEPCO is determined to conduct exploration activities in the new block in the east of the Caspian Sea.
Etemadi said Block 8-1 is located in a spot where water is 500 meters deep, adding that the drilling for this new block is under way in Iran’s sovereign zone.
“Iran’s adhesion to the group of countries equipped with technical capacity of operation in deep waters has resulted in major achievements,” he said.
Etemadi enumerated some of these achievements as follows: Construction of Amir Kabir Semi-Submersible Drilling Rig with capability to drill in deep waters, construction of Caspian vessels with a capacity of transporting 160 tons, carrying out exploration activities in Caspian Sea deep waters.