Rag Sefid oil field, which was discovered in 1964, holds the largest gas cap after Pazanan among Iranian oil fields. Rag Sefid is estimated to hold 16.5 billion barrels of crude oil plus 54.16 tcf of natural gas in place. Well No. 147 of this field experienced a blowout on October 29. It took Iranians 58 days to put out the blaze which was raging across an area with high gas pressure.

Mohsen Paknejad, deputy managing director of National Iranian Oil Company (NIOC) for production affairs, tells Iran Petroleum that extinguishing the fire in that period was a significant record in the history of Iran's petroleum industry. Rag Sefid had experienced fire twice before Iran's 1979 Islamic Revolution. It had taken American companies 100 days to contain the fire.

The following is the full text of the interview Paknejad gave to "Iran Petroleum":

Q: What caused the blowout at Rag Sefid, which took 58 days to be contained?

A: Well No. 147 of Rag Sefid blew out during pipe running operation at the depth of 2,132 meters in the Asmari reservoir. The location of the field in a hilly area had made it difficult to install rigs and build access routes. Immediately after this incident, I went to the site to manage and monitor affairs for blowout prevention. Of course, I would like to point out that when it comes to oil and gas well blowout prevention; it does not mean putting out the blaze. Had we extinguished the Rag Sefid fire, no living creature would have survived in a large radius due to the high pollution of gas.

Q: How much does gas pollution stand at in this well?

A:The H2S flowing out of this well was around 9,000 ppm. That is why the blowout prevention operation was so delicate. Minister of Petroleum [Bijan Zangeneh] insisted, from the very beginning, that all safety issues had to be taken into consideration. In fact our objective was not to put out the blaze. We had to keep fire burning until the flow of fluid from the well stopped. As soon as this fluid stopped, the fire would be extinguished. Throughout the operation, some frequently referred to the NIOC saying 'we can extinguish the well fire' but when they arrived on the scene and were informed of the incident they realized that the objective was not to extinguish the fire; rather it was to stop the flow of fluid out of the well.

Q: What was your first move?

A: The first step in managing the blowout prevention was to make necessary arrangements in terms of special disciplines needed. We needed petroleum engineering, geology, drilling engineering and construction engineering sections to come together to be able to coordinate affairs for containing the blowout.

Q: How long did it take to mobilize forces?

A: Mobilization for blowout capping was done in the best possible manner and in the shortest possible time. The National Iranian South Oil Company (NISOC) and the National Iranian Drilling Company (NIDC) were directly involved in the blowout prevention operation. I have to reiterate here that the most qualified blowout prevention specialists were present at Rag Sefid site. We managed to take advantage of the achievements and experience of people who had already seen such blowouts. All activities had been coordinated.

Q: Top and bottom kill were both engaged. Why?

A: We didn’t want to lose time in the operation. According to reference books, there are two methods of capping blowout. Top kill was not recommended due to the special circumstances of the well. Therefore, our main option was bottom kill. But we had to wait for relief wells to be drilled. Nonetheless, we finally concluded that we had to follow up both bottom and top kill simultaneously despite its toughness and difficulties. In bottom kill, the objective is to drill one or two wells in the proximity of the blowout in order to have access to the wellbore in the reservoir. In this way, the fluid which is to run into the well to stop the blowout is calculated with precision. When drilling mud comes out killing has practically been done.

In top kill, for which the wellbore has to be acceded, we had to clean up the wellhead. As you know after the blowout, the operating drilling rig and related facilities which weighed more than 500 tonnes had collapsed on the head of the well, directly affecting the top kill operation.

Q: How long did the wellhead cleanup last?

A: 28 days. I have to say that special circumstances were reigning.  The 500-tonne rig and its equipment had been intertwined due to the fire heat. Therefore, in the first step we had to clean up the area of these junks. That was while nearly 470-degree Centigrade temperature was dominant with an 8-degree gradient. It means that the temperature falls 8 degrees for each meter of distance from the well. We managed to take away some equipment which were around the well, but the main issue was to take away the rig and its installations which had crashed on the wellhead.

After cleanup, designing a stinger to match the blowout preventer (BOP), driving the stinger and contain it after entering the wellhead was examined. It took 28 days.

Q: Was it possible to clean up the well in less than 28 days?

A: Well cleanup is not necessary when there is no drilling installed and other wellhead equipment is not heavy. But Well 14 was not in operation; therefore, the rig collapsed fully on the head of the well. Naturally the wellhead had to be cleaned up before any move to contain the blowout.

Q: Why did you apply both methods?

A: At the beginning we were faced with a serious decision. According to reference books, wells whose pressures are more than 400 psi are not appropriate for top kill. Well 147's wellhead pressure was 2,740 psi ;therefore, our chance was not high for success in capping the blowout. We finally concluded that bottom kill was our main solution. The equipment was dispatched to the area very quickly and we soon prepared the ground for installing rigs. We had to drill two wells so that in case of any obstacle a second relief well would help us no to lose time. We finally decided to do both in parallel.

Q: How many times did you carry out top kill?

A: 14 times. Throughout this operation we developed a new mechanism for blowout prevention. In cooperation with the private sector and under the aegis of NISOC and NIDC, we developed a tool which we used in two top kill operations. This tool is to be modified so that in case such accidents strike the petroleum industry in the future they could be used in top kill. In this tool, the piston is inserted inside a cylinder-shaped area while there are orifices which let fluid drive the piston into the wellhead and prevent blowout. It was one of our achievements in Rag Sefid.

Q: How long did the well location last?

A: As I mentioned, the well is located in an area, access to which is difficult. Under normal conditions we need five months to set up a rig and prepare for drilling, but due to the sensitivity of work we quickly moved equipment and machinery and did it in 14 days. Furthermore, for the first time, the process of transfer, establishment of rig and spudding was done in ten days, which normally needs twice or three times that time. The vertical Well C reached the desired status in 34 days, which indicated precise calculations by drilling engineers and geologists. Fath-95 rig needed 90 days to reach that condition.

Q: Did you seek any help from other oil companies for blowout prevention?

A: No, we did not demand assistance from any company because Iran's best companies in drilling industry and blowout prevention were on hand. Of course, we would have welcomed and reviewed any proposal from other companies. Some companies contacted the NIOC, offering to help cap the blowout. But they imagined that we wanted to put out the blaze. A Canadian company also announced its readiness to assist us in the blowout prevention. Mr. Sepeheri, CEO of NIDC, and NIDC experts contacted the Canadian company's specialists who finally suggested bottom kill which we were applying.

Q: The blowout capping lasted 58 days. Don't you think it was long?

A: No, not at all! Each well has its own conditions and behavior. For example, consider blowout prevention in Kuwait's oil wells. In the late 1990s, a large number of oil wells in this country were set ablaze, but the Kuwaiti wells were low in pressure and they were extinguished automatically after the flow of fluid and blowout. But it could not apply to Well 147. We cannot use the same solution for all blowouts. Furthermore, we were busy cleaning up the wellhead for 28 days of the total 58 days. There is special equipment for carrying 450 tonnes, which we used.

Q: We have not seen any blowout in oil-rich countries in the region in recent years. Why did it happen in Iran? What causes blowout?

A: Statistically speaking, I have to tell you that we had 11 blowouts in Iran between 2005 and 2013 while only one happened between 2013 and 2017. When you consider the conditions of an oil field like Rag Sefid, you will see that it houses the largest reservoir rock and the biggest volume of reservoir fluid and the most compressed gas cap after Pazanan oil field. When you work on such fields the possibility of blowout is naturally lower than in the fields with low-pressure gas caps.

The significant point with Well 147 is that this reservoir is very active. It experienced two blowouts in 1966 and 1975. It took 94 days to cap the wells. In those years, Iran experienced blowouts while petrostates in the region had no such accidents. But regarding this blowout it has to be blamed on equipment and human error. However, we cannot speak about their shares. This issue is still under consideration. I also have to note that we have effective instructions for drilling operations. If these instructions are respected, we will see a lower number of oil and gas well blowouts.

Q: Did you even feel you would need foreign help in blowout capping?

A: It is an undeniable fact that Iran's petroleum industry faces no shortage in terms of manpower, and there is good potential in this sector. As far as the Rag Sefid blowout is concerned, I believe that what we did was fully professional and in compliance with standards. Therefore, we did not feel the need to benefit from the assistance of foreign companies in these operations. We displayed the best performance in terms of technological savvy in drilling and foreign companies are not necessarily more capable than us. I am certain that even if foreign companies had come to top kill, they would not have been effective due to the high temperature, the intensity of radiation and the bending of the blowout preventer. There was no way but to proceed with bottom kill. We had no shortage of equipment.

Q: Will this well cease production?

A: No, but two relief wells that have been drilled could produce oil.

Courtesy of Iran Petroleum