Based on comprehensive reservoir and geological studies, the field is estimated to contain 4.3 billion barrels of in-place light crude oil with an API of 32, and 400 million barrels of recoverable oil. According to Javad Owji, Iran’s Minister of Petroleum, currently, more than 210,000 b/d of oil is currently being produced in the province, and Azar accounts for the lion’s share of the produced crude.

Azar is one of the most complex oil fields

Without exaggeration, Azar is one of the most complex oil fields not only in Iran but also in the region; special geological formations and extensive facies changes have made drilling in this field one of the most difficult and challenging operations; the average duration of the well drilling operations in this field is several times longer than other wells in onshore fields of the country, and the implementation of drilling operations and some downhole services (such as mud and cement) in this field is one of the most difficult and time-consuming drilling services due to the sequence of high-pressure, low-pressure layers and the certain pressure regimes of the formations of this field.

In addition, the composition of the Azar field fluid contains high molar percentages of hydrogen sulfide and carbon dioxide, which create highly corrosive conditions and make the use of special corrosion-resistant alloys in downhole equipment, pipelines and wellhead and processing facilities inevitable. The use of these special alloys in the nuclear and military industries, and the existing sanctions have made the supply of these materials hit many hurdles from the very beginning of the project's development; however, despite all the difficulties, all the equipment and goods required by the project have been procured.

Another complication of developing Azar is the weak reservoir properties of the field, which caused an Iranian company to include acid fracturing operations in the field development plan from the very beginning due to the fissured nature of the reservoir, and to include this operation in the Azar exploratory wellNo. 2, resulting in a significant boost in the production efficiency index of the well. This operation was also implemented in some wells during the development of the field.

Another challenge facing the Azar Field’s development operation, which has not been reported in any other oil field, is the occurrence of numerous cracks and fissures in the field, which appear after seasonal rains. Based on the investigations, these cracks are the result of the weak structural levels of the earth's layers, and erosion alone is not its cause, and since these cracks can be dangerous for the structures, buildings and facilities, in the areas adjacent to the waterways (given the potential for formation of the waterways and the possibility of expansion of these cracks into wide underground tunnels and the collapse of these tunnels and finally creation of chimneys and sinkholes), building facilities has been refrained from and by conducting detailed studies, the danger zone of the area has been identified and separated into more hazardous and less hazardous areas; also to understand the origin of these cracks and fissures, which increase the risk of the development operation, measuring the problem of erosion or global subsidence of the land was investigated as one of the reasons for the opening of cracks, and determining the rate of vertical and horizontal variations of the cracks themselves was considered.

Performing Acid Fracturing Operations

Drilling 19 production wells and one wastewater disposal well with an average depth of 4,600 meters, performing acid fracturing and high-volume selective acid stimulation in all wells in Azar Field, installation of wellhead facilities and 80 km of 8-inch pipelines, construction of 320 kilometers of pipelines to transfer oil and gas from the field to the desired destinations; which is NGL 3200 for the crude oil and associated petroleum gas produced at Cheshmehkhosh production unit, construction of a central processing unit with a capacity of 71,500 barrels, and construction of an early production unit with the capacity of 30,000 barrels of crude oil are among the operations implemented for developing Azar Oilfield.

The Azar oil field, whose production target has been achieved in the development plan, has achieved this target by relying on domestic capacities, while Iraq has benefited from the cooperation of foreign companies to develop the Al-Badrah field, which is joint with the Azar field. This field is very unique from the point of view of the geological structure, in such a way that the drilling operation is difficult and challenging in this field, and the average drilling time in Azar field is several times longer than drilling in onshore wells in other parts of the country.

At the same time, the successful implementation of acid fracturing operations in several wells of the Azar field was an activity that was implemented for the first time in the country on a field scale, while other wells of this field were also subject to high-volume selective acid job, which made maximum involvement of the production layers possible and as a result a significant increase was achieved in the production efficiency index from the wells of this joint field.

There was no backdrop of successful implementation of acid fracturing operations in the field scale in the country and Azar was the first oil field where this operation was carried out. For implementation of acid fracturing operation, five wells were considered and it was decided to continue this process after implementation of the operation in five wells of the field, but after implementation of the operation in three wells, due to some problems in the optimal management of the wells, it was decided to replace high-volume acid job in the future.

Formation with Alternating and Complex Pressure Regimes

Azar Field has a structure with alternating and complex pressure regimes. The entanglement of the structural features of the field caused continuous and unpredictable variations in the pressure regime of the layers of the earth during the drilling operations at great depths. That is, due to the high frequency of low-pressure and high-pressure layers and the recording of unusual formation pressures during drilling, in short time intervals, both drilling mud waste and high-pressure fluid flow have occurred, and to solve this problem, casings and liners of unusual sizes were used.

The deepest and heaviest surface string casings in the country, with a depth of more than 2 km and a weight of about 500 tons, have been installed in Azar wells, and the largest number of drilling sections for optimal access to the reservoir layer at the level of the country's oil fields with seven bores has been carried out in Azar field. In addition, due to the high pressure and temperature of the reservoir, Azar Field could be considered one of the fields with high pressure and temperature (HPHT) and considering the high amount of acid gases, the operational challenges of this field are doubled. Add to the list of difficulties, the high heterogeneity in rock and fluid properties, especially the quality of oil produced from different reservoir horizons, the presence of abundant wax and asphaltene deposits, and high amounts of hydrogen sulfide gas in the reservoir.

Cooperation of Iranian Universities to Ensure Production

Given the fact that oil production conditions are pretty unique in Azar Field, maintenance and operation of the wells of this oil field also require special know-how and expertise, which is currently being carried out by the engineers and experts of the Iranian oil industry with the cooperation of domestic universities. It should be remembered that at the beginning of the exploration and development of this joint field, the development of this huge and complex field was supposed to benefit from the capabilities and experience of major foreign companies, but this was not possible due to the sanctions imposed on the country; therefore, an important part of the activities was assigned to the Research Institute of Petroleum Industry (RIPI) under three consecutive contracts and projects since 2018.

Saber Mohammadi, the operator of a project to guarantee the flow and improve production in the Azar oil field, said in this regard: “Azar Field with more than 4 billion barrels of oil in-place storage and light oil production, as well as a special geological structure and a sequence of high-pressure and low-pressure layers, has made drilling in it one of the most difficult and challenging operations.”

The fluid composition of Azar Field contains a high percentage of hydrogen sulfide gas and carbon dioxide, and the presence of these gases creates highly corrosive conditions, which necessitates the use of special corrosion-resistant alloys in downhole equipment, pipelines and wellhead as well as processing facilities, and on the other hand, due to the high corrosiveness of the fluid, the acid job in the wells of this field is associated with many challenges and problems.

According to him, continuous injection of asphaltene deposition inhibitor and corrosion inhibitor is currently being carried out in the production wells of this field under the continuous supervision of the Research Institute of Petroleum Industry, and this measure plays a significant role in guaranteeing the production flow in the oil field. Based on this, according to the characteristics of the field, by late June, in the form of a comprehensive scheme, the pathology of acid job in the wells of Azar field and the optimization of its formulation were examined and the optimization of acid treatment packages in different wells of Azar field was announced as one of its most important achievements; therefore, the protocol for checking acid treatment packages in the material synthesis stage and before use in the field was carried out for the first time in Azar field with the effective participation of the RIPI, which will lead to a safe and economical production.

Courtesy of Iran Petroleum