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Dagang Oilfield "9.9" Blowout Accident Investigation Report At around 13:30 on September 9, 2007, the West 60-8 Well of Dagang Oilfield Company, which was drilled by Team 20508 of the Second Drilling Engineering Company of Dagang Oilfield Group Co., Ltd., suffered an out-of-control blowout and caught fire during the drilling process, resulting in the death of one person and the burning of the drilling rig and major equipment and facilities at the well site. The blowout went out of control for 2 hours and 20 minutes. After receiving the report of the out-of-control blowout accident, Liao Yongyong, deputy general manager of the group company, immediately organized a meeting to study and deploy accident rescue and investigation work. On the afternoon of September 9, an expert team led by the head of the engineering technology and marketing department of the group company went to the scene to direct the rescue. The accident well site was cleared on September 12. On September 10, the accident investigation team sent by the group company entered the Dagang Oilfield to conduct accident investigation work. The accident investigation team has basically ascertained the course and cause of the accident. The investigation results are now reported as follows: 1. Basic situation (1) Basic situation of the production capacity construction project in the West 58-8 well area 1. Overview of the West 58-8 well area The West 58-8 well area was discovered in 2007. It is located at the junction of the Gangxi Oilfield and the Gangzhong Oilfield in the Beidagang structural belt. It is a fault block oil reservoir sandwiched between the Gangxi main fault and the Gangxi front fault (see attached figure 1). The oil-bearing area of this fault block is 0.34Km2. The main oil-bearing target layers are the lower section of the Minghuazhen Formation and the Guantao Formation. The geological oil reserves are 260×104t. The geological reserves of the oil reservoir in the lower section of Minghua Town are 96×104t. The reservoir depth is 680~1415m, and the porosity is between 23.59~32.41%, with an average of 28.25% ； The permeability ranges from 282 to 671×10-3μm2, with an average of 405×10-3μm2. The density of crude oil is 0.93g/cm3, the viscosity of crude oil is 94.32 mPa·s (50℃), and the wax content is 2.74%. The reservoir pressure coefficient is 0.97. The geological reserves of the Guantao Formation oil layer are 163×104t. The reservoir burial depth ranges from 1415 to 1590m, and the porosity ranges from 25.03 to 29.98%, with an average of 27.6% ； The permeability ranges from 219.95 to 486.83×10-3μm2, with an average of 405×10-3μm2 ； The density of crude oil is 0.91 g/cm3, the viscosity of crude oil is 38.09 mPa·s (50℃), and the wax content is 2.74%. The reservoir pressure coefficient is 0.92. Well West 58-8 is a rolling discovery well in this fault block. It was put into production on August 6, 2007. It produces layer 55, Pavilion II3, and the well section is 1567.3~1569.1m. The initial daily oil production is 6.16t, the gas is microscopic, the water content is 45%, and the formation pressure is 14.38MPa. ； The current daily oil production is 21.02t, with a water content of 26.5%. The "Development Plan Review Meeting for the West 58-8 Well Area of the Gangxi Oilfield" held on August 15, 2007 determined that the Guantao Oil Formation in the West 58-8 Well Area will be developed by water injection with an irregular well pattern of 150m well spacing (see attached figures 2 and 3). Total number of wells: 8: There are 6 oil wells and 2 water injection wells. Among them, 1 old well is utilized and 7 newly drilled wells (3 directional wells, 2 horizontal wells, and 2 water injection wells). When the West 60-8 well blew out, there were 5 wells being drilled in the West 58-8 well area.: The well depth of West 58-6 Well is 1356m, and the mud density is 1.13 g/cm3 ； The well depth of West 60-8 Well is 1032m, and the mud density is 1.14g/cm3 ； The well depth of West 58-10 Well is 1250m, and the mud density is 1.12 g/cm3 ； The well depth of West 58-12H well is 502m, and the mud density is 1.06 g/cm3 ； The depth of Well West 58-26H is 1799m, and the mud density is 1.16 g/cm3. The completion mud density of the completed Well West 58-8 when drilling into the Ming II oil group was 1.12 g/cm3. 2． Basic information about Well West 60-8 Well West 60-8 is a directional well in the West 58-8 well area. The design targets the Guantao oil formation while taking into account the Minghua oil layer. The drilling trajectory crosses the fault at 860m and enters the West 58-8 fault block from the Gang 146 fault block. The designed well depth is 1716.86m (vertical depth 1590m), and the target layers are the Minghua and Guantao oil formations. Design mud density: 0～301m is 1.05～1.08 g/cm3 ； 301～935m is 1.08～1.12 g/cm3 ； 935～1717m is 1.12～1.17 g/cm3. Design three target points and three sections of directional drilling. Among them, the inclined well section is 586.17~977.54m, the stable inclined well section is 977.54~1717m, the maximum well inclination angle is 31.31°, and the azimuth is 144.48°. The designed well structure is: φ444.5mm wellbore × 301m + φ339.7mm surface casing × 300m + φ241.3mm wellbore × 1717m + φ177.8mm oil layer casing × 1713m. (See attached picture 4) Well West 60-8 was opened on August 28, 2020: 00, the φ339.7mm surface casing reaches a depth of 301m. The second opening wellhead device is: FH35-35 annular blowout preventer + 2FZ35-35 double ram blowout preventer + four-way + casing head (T339.7×177.8-35A) (see Figure 5). At 5:00 on August 31, the second drill was opened with a φ241.3mm drill bit, and at 10:55 on September 9, 1.14 g/cm3 mud was used for normal directional drilling to a well depth of 1032m. There are no other wells producing in the Minghua Town oil layer in this block. The reservoir profile is shown in Figure 6. The schematic diagram of the three wells being drilled in the same well site is shown in Figure 7. 3． Basic information on the drilling team and drilling rigs 20508 The drilling team obtained the Class B qualification certificate from China National Petroleum Corporation on March 30, 2007. Currently there are 52 employees, including: There are 21 registered employees and 31 market-based employees. Among the market-based employment, 20 workers were recruited by themselves and 11 workers were dispatched by Yixian Hongyuan Labor Service Co., Ltd. and Tianjin Sipu Human Resources Service Co., Ltd. The composition of the entire team is: 1 person is a junior college student and 17 people are a technical secondary school student. All relevant personnel have obtained valid certificates such as well control operation certificates and work certificates. At the time of the accident, there were 9 people on duty in the drilling team.: The cadres who lead the shift are engineering technicians, drillers, assistant drillers (derrick workers will be substituted), derrick workers (derrick workers will be substituted), one inner tong, one outer tong, and one site worker, and one head shift driver and one assistant. In addition, there are 2 people from the drilling technical service company (mud workers) and 2 people from the geological logging company at the well site. The drilling rig used by the team is the ZJ20K skid-mounted drilling rig produced by Nanyang Petroleum Machinery Factory and was put into use in October 1998. (2) Brief description of the blowout accident 1. Blowout accident At 10:55 on September 9, 2007, Well West 60-8 was directional drilled to a well depth of 1032m (vertical depth 1000.25m) and prepared to start drilling and replace the drill bit. Because two gas measurement abnormalities were seen at 1005m and 1025m respectively, the open II oil layer has been drilled. According to the relevant requirements of the "Dagang Oilfield Drilling Well Control Implementation Rules", it was decided to stop the drilling cycle to eliminate the aftereffects, and then drilled 15 columns of drill pipes with short tripping (two drill pipes are one column) to measure the oil and gas upward channeling speed and check whether the mud density can balance the formation pressure. To 11:50, the drilling tool was circulated and moved for 55 minutes (the geological late time was about 23 minutes). During the cycle, the total hydrocarbon content dropped from a maximum of 18.67% at 11:15 to zero at 11:22. At 11:54, I removed the kelly and prepared to drill, but found that there was a problem with the hydraulic tongs, so I repaired the hydraulic tongs. ； At the same time, the movable drilling tool was raised and lowered (with an amplitude of 12.18 meters) until 12:17, which took 23 minutes. Trimming started at 12:17. Before tripping out, the total volumes of mud in the annulus and drilling tool were 44.32m3 and 9.39m3 respectively. During the drilling process, mud is poured into the annulus once every 2 drill pipes are pulled out, and a total of about 0.6m3 of mud is poured. When reaching the 11th column, the lifting force of the drilling tool increased from 420KN to 441KN. The driller judged that it was underground suction and decided to continue the drilling operation. At 13:05, the 12th column was completed, and the drill bit position was 790.72 meters. A small amount of mud flows out of the outlet groove when lifting the drilling tool, but no mud flows out of the exit groove when drilling is stopped. The engineering technician who organized the short trip operation on site decided to connect the kelly. At 13:08, the upper drill pipe was connected. Afterwards, the high and low pressure gates of the pump room were inverted, and the pump was switched off three times intermittently for a total of 6 minutes to observe the reaction at the wellhead. in: 13:14 Turn on the pump to pump mud for 1 minute ； 13:15～13:19 Moving drilling tools up and down (width 5.24 meters) ； 13:19～13:22 Turn on the pump to top the mud for 3 minutes ； Stop the pump for 2 minutes and then turn on the pump to top the mud for 2 minutes. At 13:26, the site worker in charge discovered that the outlet tank was overflowing and immediately informed the driller. The driller issued a shut-in signal, the site worker opened the No. 4 flat valve, and the technician and assistant driller got off the drilling floor and prepared to run to the remote console. At 13:27, the driller began to lift the kelly pipe. When the drill pipe joint was lifted about 0.3m out of the turntable surface, mud erupted from the wellhead and knocked down the driller (the drill floor area was 4×6m, and the driller's operating position was 1.5m away from the center of the wellhead). The driller lost his hand on the brake handle, and the swimming system lost control. The traveling block, hook, and faucet hit the turntable surface, and the kelly and the drilling tools fell into the well. The inside and outside fitters on the drill floor immediately fled the drill floor upon seeing this. The engineering technician and assistant driller who were running down the ladder heard the collision and immediately returned to the drill floor to observe the situation. They found the driller fell to the ground and rescued him. Then they found that the faucet lifting ring was decoupled from the big hook. When trying to quickly raise the big hook, hang up the faucet, and continue to lift the kelly pipe, it was found that the big rope had broken strands, so it was not possible to do so. As the blowout potential increased, the engineering technician, driller and assistant driller evacuated the drilling floor. The deputy driller and engineering technician ran towards the remote control console located on the east side of the well site. On the way (around 13:30), a fire broke out at the wellhead. The wellhead flames scattered in all directions under the drill floor. At this time, the wind was westerly and strong at the site. The flames were pushed to the east, and the remote control console located in the east direction was surrounded by flames. ； The engineering technician and assistant driller failed to run to the remote console to turn off the annular blowout preventer, which ultimately resulted in an out-of-control blowout and a fire. The escape routes for production team employees are shown in Figure 8. The derrick fell to the east 3 to 5 minutes after the fire started (see attached picture 9). After the fire broke out, the derrick worker on the second-floor platform climbed onto the overhead crane, slid to the ground along the No. 4 tension rope extending to the northwest side of the derrick, and fell into the fire and died. The local public security department issued a death report and determined that the death was caused by burning. After the blowout, the drill bit position is 803.51m, and the drilling tool assembly in the well is: φ241.3mm roller bit 0.25m +φ197mm 1.25o bend motor 6.99m +φ233mm centralizer 1.81m + 411x4A10 joint 0.45m +φ165mm non-magnetic anti-compression drill pipe 9.12m + MWD short-circuit 1.12m + φ165mm non-magnetic drill collar 9.49m + φ127mm weighted drill pipe 181.81m + φ127mm drill pipe + kelly pipe 2. Emergency response and rescue situation after the blowout After the accident, the accident well team immediately reported to the superiors and relevant departments step by step while organizing the evacuation of personnel. Dagang Oilfield Group Company and Dagang Oilfield Company promptly launched the blowout emergency rescue plan after receiving the accident report. The leaders of the two companies at home, as well as the heads of relevant units and engineering and technical personnel rushed to the scene, established an emergency rescue headquarters at the accident site, and set up cordons inside and outside the accident site. The emergency rescue headquarters at the accident site consists of an on-site coordination group, a plan group, an inspection group, and a rescue group, which are responsible for overall coordination, technical support, on-site inspection, and rescue operations. At 14:30 on September 9, the fire at the wellhead began to gradually decrease. At 15:50, the blowout stopped due to the collapse of the well wall, and the flame at the wellhead was extinguished. The blowout went out of control and caught fire for 2 hours and 20 minutes. At 18:00, all open flames around the well site were extinguished, and firefighters found the body of the derrick worker. 3． Handling of the Blowout Accident At 20:00 on September 9, an expert team led by Qin Wengui, deputy director of the Engineering Technology and Marketing Department, arrived directly at the accident site, inspected the scene, organized a meeting, and conveyed the instructions of Deputy General Manager Liao Yongyuan to the relevant personnel of the two Dagang Oilfield companies. The meeting determined that in accordance with "Resolutely put an end to secondary accidents" ； In accordance with the principle of "clearing the wellhead first, easy things first, then hard ones, first outside, then inside, and quick solution", we did a good job in handling and cleaning up the accident site, and worked with relevant experts and technicians from the two companies to study and formulate a disposal plan and put forward specific requirements. After the flames at the site were extinguished on September 9, we began to clean up the prefabricated houses, oil tanks and other facilities outside the well site. At night, a guard duty is arranged and operations are stopped. From 11:30 to 18:54 on September 10, a cumulative total of 26.5 m3 of 1.6g/cm3 heavy mud, 17.5 m3 of 1.4g/cm3 heavy mud, and 30.8 m3 of plugging mud were injected into the annulus of the accident well from the outlet of the self-blowing line. ； Pour 3.6 m3 of leak-proofing mud into the drill pipe from the central pipe of the faucet. Based on the analysis of the mud filling situation, it is concluded that the well collapse occurred in the lower part of the surface casing shoe (300 meters) ； The drilling tool has a leakage channel above the well collapse point (about 300 meters). The water hole of the drilling tool is connected to the annulus, and the natural gas in the drill pipe has been replaced by mud. After the sediment under the drilling floor was basically cleared, at 16:00 on September 11, new hydraulic control lines and remote control consoles were reinstalled for the original fully-sealed ram blowout preventer and annular blowout preventer on the wellhead. The annular blowout preventer was verified to be usable by pressure. Then, cut the kelly directly from the upper side of the annular blowout preventer (the drilling tools in the well will not fall when the kelly is cut), and take out the faucet ； Next, remove the derrick base and original blowout preventer assembly. As of 22:05 on September 11, the new blowout preventer combination was installed at the wellhead, and the full seal was closed to control the wellhead. As of 11:00 on September 12, the accident scene was completely cleared. During the entire rescue and accident handling process, no secondary safety accidents or environmental pollution occurred. 2. Causes and nature of blowout accidents (1) Causes of blowout accidents 1. The direct cause of the blowout accident is that after drilling into the reservoir and drilling the Kaiming II oil layer, the high-pressure gas in the formation invaded the wellbore due to the long-term up and down movement of the drilling tool before drilling. ； During the tripping process, due to the loss of circulation pressure after the pump is stopped and the suction effect caused by the lifting of the drill string, the gas pressure that invades the wellbore is released and moves up rapidly. ； After pulling out 12 columns of drill pipe, the circulating mud causes the gas that has entered the wellbore to move up and expand rapidly, forming an overflow. ； Because the well was not shut down decisively, the overflow developed into a blowout ； The mud and sand ejected from the exhaust pipe of the running main diesel engine or the wellhead hit the derrick and generated sparks, causing the ejected gas to catch fire. ； Due to the influence of the wind direction, the remote console was surrounded by flames, and the final opportunity to shut down the well was lost, causing the wellhead to blow out out of control and catch fire. The derrick worker on the second floor did not get off the derrick after the drilling work stopped. After the well shut-in signal was sent, he did not evacuate from the derrick in time. He lost the opportunity to escape and fell from the derrick tension rope and fell into the fire and died. 2． Indirect causes of the blowout accident (1) Drilling encountered an enriched area of dissolved gas (bottom oil (water) capping gas). Analysis of the well logging and gas logging data of Well West 60-8 shows that: The rock cuttings in the 829-834 m section of MingⅠ showed fluorescence, and the gas measurement total hydrocarbon value was 1.22-4.86%. The gas measurement was interpreted as gas and water in the same layer. ； The rock cuttings in the 997-1006m section of Ming II showed fluorescence, and the gas measurement total hydrocarbon value was 0.4-8.55%. The preliminary interpretation of the gas measurement was that gas and water are in the same layer. ； The cuttings in the 1022-1032m section of Ming II showed fluorescence, with a total hydrocarbon value of 0.58-21.8%, and the gas test was initially interpreted as an oil and gas layer. Based on the construction conditions, it can be inferred that the blowout layer should be the Ming II oil layer group below the drill bit. According to the geological design, Well West 60-8 crosses the fault at 860m ； The strata above 860m are located in the downthrown side of the Gangxi front fault and belong to the Gang146 fault block. Below 860m, they enter the newly discovered West 58-8 well area. Three-dimensional seismic data shows that Well West 60-8 is located in a higher structural position of the Ming II 3 reservoir (see table below). Therefore, it is inferred that Well West 60-8 may have a dissolved gas enrichment area (bottom oil top gas reservoir) in the Ming II3 oil layer group. Comparison table of oil layer positions in the West 58-8 well area. Well No. West 60-8 West 58-6 West 58-8 West 58-10 Ming II 31 Vertical depth at the top boundary 970.64 982.62 980.12 982.97 Vertical depth at the bottom boundary 979.4 992.33 986.5 990.48 Thickness 8.76 9.71 6.38 7.51 MingⅡ32 Vertical depth of top boundary ground 991.43 998.15 992.12 992.42 Vertical depth of bottom boundary ground 1000.25 1004.02 1005.98 1007.35 Thickness 8.82 5.87 13.86 14.93 (2) The density of the equivalent mud acting on the gas layer decreases during drilling, causing a large amount of formation gas to invade the wellbore. Based on the fact that the gas measurement after-effects can be basically eliminated within two cycles, it is proved that during normal drilling and circulation, the hydrostatic column pressure of the mud with a density of 1.14g/cm3 plus the annular circulation pressure loss can balance the formation pressure. However, when the pump is stopped, the suction caused by repeated lifting and lowering of the active drilling tool for a long time, varying degrees of mud bags in the drill bit and centralizer, and the loss of annular circulation pressure loss, all three work together to enhance the suction effect when the drill string is lifted, offset part of the mud hydrostatic column pressure, and cause formation gas to invade the wellbore. Especially before tripping out, the movable drilling tool was repeatedly raised and lowered 11 times within a range of 5 to 13m with the pump stopped for a total of 23 minutes, which increased the possibility of a large amount of formation gas intruding into the wellbore. (3) Wrong judgment, illegal operation, and missed the favorable opportunity to shut down the well. Before the short trip, there was an abnormality in the gas measurement. Although the total hydrocarbon value dropped to zero after being eliminated by circulation, the abnormal total hydrocarbon value this time was as high as 21.8%, which should be an important indication that the oil and gas layer was encountered during drilling. The engineering technicians and drillers did not conduct a careful analysis of the gas measurement anomaly and still mistakenly believed that the reservoir did not contain gas. When the 11th drill pipe failed to fill with mud, we still thought that there was only suction in the well, and did not realize that oil and gas had invaded the wellbore. ； In terms of the measures taken, instead of immediately reconnecting the kelly pipe, shutting in the well, and throttling the cycle to eliminate gas invasion, they mistakenly decided to continue pulling out the 12th drill pipe, causing further suction and causing a large amount of formation fluid to invade the wellbore. When it was discovered that the well could not be filled with mud, the engineering technician made the mistake of connecting the kelly pipe three times to pump mud into the drill pipe for 1 to 3 minutes each time. This caused the gas entering the wellbore to quickly move up nearly 300m and expand, causing the wellhead to overflow and then develop into a blowout. (4) The well shut-in procedure was not implemented decisively, resulting in an out-of-control blowout. After the overflow was discovered and the driller issued the shut-in signal, each position in the team moved according to the "four-seven" action procedure. When the driller was lifting the drilling tool, he was knocked down by the sprayed mud, the brake handle lost control, the kelly and the drilling tool fell freely, and the faucet, hook and traveling block hit the turntable. The assistant driller and engineering technician who ran down the drill floor to shut in the well, after hearing the collision on the drill floor, did not continue to run to the remote console to perform the shut-in operation, or at least one person went to shut in the well. Instead, they ran back to the drill floor together, thus missing the favorable opportunity to close the annular blowout preventer, resulting in an out-of-control blowout. After the blowout caught fire, due to the influence of the wind direction at the well site, the remote console was surrounded by flames, and the last opportunity to shut down the well was lost, causing the wellhead to blow out out of control and catch fire. (5) When a blowout occurs, the ejected gas will catch fire when it encounters a fire source. The sparks emitted from the exhaust pipe of the running main diesel engine or the formation mud and sand ejected from the wellhead will hit the derrick and cause the ejected natural gas to catch fire. The diesel engine driver on duty stopped the diesel engine with the pump. However, because the main diesel engine driving the winch and turntable was on an intermediate platform, it was difficult to access after the blowout intensified and failed to stop. The sprayed gas may be ignited by sparks from the diesel engine exhaust pipe. Or, due to the violent blowout at the wellhead, the gas-entrained formation mud and sand hit the derrick base and generated sparks that ignited the spurted natural gas. 3． Analysis of management reasons In recent years, although Dagang Oilfield Group Company and Dagang Oilfield Company have done a lot of hard and meticulous work in formulating and improving a series of rules and regulations, signing safety and environmental protection responsibility certificates, intensifying safety supervision inspections and penalties, increasing investment in well control equipment, and carrying out safety training for all employees and special well control training, they attach great importance to well control safety management. However, in the face of new development situations and production needs, certain deficiencies have been shown in dealing with the relationship between safety and speed, safety and efficiency, and safety and development. (1) Insufficient understanding of the complex underground conditions. From the combustion situation of the well's ejecta and the on-site analysis of the combustion after the fire was extinguished, it was found that the fire in this well was mainly caused by the combustion of natural gas, which came from the Minghua Town oil reservoir. Gangxi Oilfield is a complex fault-block oil reservoir with small sand bodies, many faults, and extremely complex structures. The distribution regularity of oil, gas and water in the reservoir is poor, especially the distribution of bottom oil (water) and top gas reservoirs is difficult to understand. Gangxi Oilfield is an area prone to well kicks and blowouts, and has experienced many well kick and blowout accidents in history. Dagang Oilfield has insufficient understanding and attention to the well control risks brought about by the drilling project of the bottom oil (water) top gas reservoir, and has not conducted an in-depth and systematic analysis of the reasons for the repeated well kicks, overflows, and gas channeling in the Gangxi Oilfield. The drilling engineering design suggested that a severe natural gas blowout occurred in Well West 55-7 (which belongs to the same West 58-8 well area as the accident well in the Ming II formation and is about 250m apart) when drilling normally with 1.20g/cm3 mud to a well depth of 962m (see Figure 10, top boundary structural map of the Ming II 3 oil group in the West 58-8 well area). There are missing items in the geological design reference data for adjacent wells, and there is no clear indication of a blowout in Well West 55-7. The geological design is mainly based on the drilling and logging of the nearest Well West 58-8, which has just been drilled and put into production (Well West 58-8 means there is no gas layer below 810m) and three-dimensional seismic data (Well West 60-8 and West 58-8 have relatively good connectivity in the NmII3 sand body). It is judged that Well West 60-8 only has oil layers and water layers. There was no in-depth analysis of the fact that Well West 60-8 is located in the high structural position of the West 58-8 well area and may have an enrichment area of dissolved gas. It is a bottom oil cap gas reservoir, and it was not aware of the high risks it may bring to drilling. (2) Well control measures were not effectively implemented on site. When reaching the 11th drill pipe, the driller discovered that the hook load increased. Based on experience, he believed that it might be caused by suction during drilling. He did not realize that suction might cause bottom-hole formation fluids to invade the wellbore, thus causing a well control hazard. On the contrary, they made the mistake of deciding to continue pulling out the 12th drill pipe to further verify the underground situation. During the process of pulling out the 12th drill pipe, it was discovered that it was difficult to pour mud in. However, they still did not realize that the reservoir fluid had entered the wellbore and the harm that would cause it. They also failed to take the "four-seven" action in time to stop drilling and shut down the well in accordance with the "Four-Seven" requirements of the "Digang Oilfield Drilling Well Control Implementation Rules". In particular, due to misjudgment by the technician in charge and the driller on duty, they decided to pull out the 12th drill pipe and then connect the kelly, and intermittently pumped mud into the bottom of the well for observation. This artificially pushed the fluid intruding into the wellbore about 300 meters upwards, accelerating the upward expansion of formation gas, increasing the difficulty of handling the overflow, and delaying the well control disposal time. During the process of shutting in the well according to the "four-seven" action after discovering the overflow, the brake lever lost control. The assistant driller who went to execute the shut-in order turned back to the drilling floor midway, failing to shut down the well safely and in time, causing the overflow to turn into a blowout, loss of control, and fire. (3) The emergency response capabilities of the well team and employees are not strong. First, technicians and drillers lack experience in judging underground overflows, do not respond promptly and decisively, make mistakes while busy at work, and have obvious insufficient emergency response capabilities. In an emergency, the driller himself issued a shut-in signal and was knocked down by a sudden spurt of mud when lifting the drill string. He lost control of the brake handle, lost control of the drilling rig, malfunctioned the swimming system, and lost the well control command center. Second, after the driller sent the well shut-in signal, the assistant driller heard an abnormal sound on the drilling floor while running to the remote console. In a panic, he forgot his well control duties and returned to the drill floor. He missed the favorable opportunity to shut down the well sealing device, resulting in an out-of-control blowout. Third, the replacement derrick worker who had been working on the second-floor platform for less than three months did not get off the derrick for more than 20 minutes when he stopped drilling and connecting kelly pipes. ； After hearing the well shut-in signal, due to lack of experience and slow reaction, they did not make full use of the 4 minutes from the blowout to the fire to evacuate from the derrick in time. ； It was only after the fire broke out that he climbed onto the overhead crane platform, slid down the derrick rope and fell into the fire and died. Fourth, during this short tripping process, the entire team of operators did not have strong ability to recognize dangers and poor cooperation and coordination abilities. After the well shut-in signal was sent, the assistant driller did not arrive in time to shut in the well. ； The inner and outer fitters also hurriedly fled the drill floor. When the driller lost his grip on the brake lever, no one took control of the brake lever in time. ； The inner and outer fitters passed by the remote control console immediately on their way to escape, and did not even think of turning off the well sealing device. (4) The quality of personnel in key positions is low. In recent years, due to the rapid growth of exploration and development workload, in order to meet the drilling needs of exploration and development, Dagang’s drilling team has increased rapidly. There is a serious shortage of skilled employees in the front-line positions of the well team, and the proportion of new employees is too high. Although a large amount of pre-job training and well control training have been carried out, and although the staff shortage has been alleviated in terms of total staffing, the basic skills and knowledge of these new personnel obviously still cannot meet the basic requirements of actual production. Before the accident, the personnel on duty had removed the kelly pipe after completing the short tripping cycle, and then raised and lowered the movable drilling tool for a long time to directly pump the oil and gas layer. ； Then, the drilling was started without circulating the mud that had been severely gas-invaded at the bottom of the well. ； After discovering overflow at the wellhead, the mud pump was turned on again, which accelerated the development of the overflow into a blowout. This series of major technical mistakes and violations reflect the low technical quality of the well team technicians and drillers, poor well control awareness, ignorance, fearlessness, and lack of trust and fear. The survey found that currently, 22% of the employees on the drilling team of Dagang Group Drilling Company No. 2 have less than 1 year of experience, and 20.9% have 1 to 3 years of experience. The new employees recruited are basically added to the drilling team, and the proportion of new employees in the team is too large. Among the 60 drillers in the 20 drilling teams of Drilling Company No. 2 in the Dagang Oil Area, 22 have less than one year of experience and 22 have 1 to 3 years of experience. They account for 73.4% of the total number of drillers. These new drillers have been on the job for a short time, lack experience, and have poor leadership skills. Judging from the personnel on duty at the time of the accident, there was also a serious shortage of competent production team members for the well team. The driller who leads the shift is a foreign worker with only 3 years of service. ； The driller who died temporarily taking over as a derrick worker in the accident was a foreign worker newly hired in July this year and had no qualifications or work experience at all. ； Internal and external fitters are contract workers who have been working for less than one year. These new workers lack practical experience, have low safety awareness, poor operating skills, and weak emergency response capabilities. They do not know how to respond to emergencies, dangers, or complex situations. (2) Losses from blowout accidents The determination of economic losses in this accident mainly refers to the calculation methods and evaluation indicators of the "Statistical Standards for Economic Losses in Casualty and Casualty Accidents of Enterprise Employees". After verifying the accident losses reported by Dagang Group Company and Dagang Oilfield Company, it was confirmed that the total economic losses caused by the "9.9" blowout out of control accident were 2.2417 million yuan, of which: The direct economic loss was 1.6091 million yuan and the indirect economic loss was 632,600 yuan. Direct economic losses mainly include the aftermath costs incurred during accident rescue, fixed asset loss costs, and rescue material costs, etc. Indirect economic losses mainly include sidetracking well costs, adjacent well shutdown losses, emergency firefighting vehicle and personnel costs, etc. See the table below for details of specific economic losses. Accident Economic Loss Detailed List Loss Cost Category Cost Item Amount (10,000 Yuan) Direct Economic Loss (1.6091 million Yuan) After-care heavy mud, well kill cement truck shift fee, etc. 7.1594 Site cleanup and other expenses 11.1881 Rescue personnel living expenses 0.6 Pensions and cremation expenses 17.9 Work-related injury care and other expenses 0.15 Facility loss Net value of main drilling equipment 23.9618 The net value of the drilling team’s barracks is 11.9266 The net value of the drilling team’s computers and other equipment is 8.0817 The net value of the equipment and facilities of the directional well company is 7.9132 The net value of the equipment and facilities of the geological logging company is 30.7280 Compensation expenses Burial well drilling tool expenses 2.36 MWD instrument expenses 21.3 Other losses tarpaulin 0.22 Mud treatment agent 10.6 Barite 3.8441 Circuit rectification fee 0.98 Derrick inspection fee 2 Indirect economic loss (632,600 yuan) Sidetracking loss Sidetracking cost 55 Production suspension loss Near-well production suspension loss 1.5 Firefighting expenses On-site rescue vehicles and firefighting expenses 6.76 (3) Nature of the blowout accident According to the relevant provisions of the "China National Petroleum Corporation Accident Management Measures", the accident investigation team conducted an investigation in accordance with the prescribed procedures, and after careful discussion and analysis, it was concluded that: The blowout and fire accident in West 60-8 Well of Dagang Oilfield was caused by the drilling operators' misjudgment of the underground situation, illegal operation, and improper handling during the short tripping process. 3. Responsibility Identification and Handling Suggestions Based on the group company’s “Safety Production Management Regulations”, “Interim Regulations on Administrative Responsibility for Safety Accidents”, and “Regulations on Sanctions for Management Personnel Violations of Discipline and Violations (Trial)”, the investigation team recommended reporting the “9.9” out-of-control blowout accident and instructing the person in charge of well control of Dagang Oilfield Branch and Dagang Oilfield Group Co., Ltd. to conduct an inspection at the group company’s professional meeting. At the same time, for the responsible persons of relevant units and departments involved in the "9.9" blowout accident, the following suggestions are put forward for accountability and punishment:: (1) Dagang Oilfield Group Co., Ltd. 1. Zhang Baozeng, deputy general manager of Dagang Oilfield Group Co., Ltd., as the leader in charge of well control management and engineering technology management, is responsible for the failure to implement well control measures and the occurrence of blowout accidents. It is recommended that an administrative warning be given. 2． Xiong Lasheng, director of the Engineering Technology Department, as the leader of the well control and engineering technology department, is responsible for the management of the issues exposed by the accident, such as the employees’ lack of awareness of well control and inadequate well control education and implementation of well control technical measures. It is recommended that administrative warnings be given. 3． Liu Guangmu, the manager of the Second Drilling Engineering Company, as the company's first person responsible for safety production, is primarily responsible for the problems exposed by the accident such as weak team building at the grassroots level, poor awareness of well control among employees, and inadequate implementation of well control technical measures. It is recommended that the company be given a major administrative demerit. 4． Ma Jinshan, deputy manager and chief engineer of the Second Drilling Engineering Company, as the leader in charge of well control and engineering technology, was responsible for the problems exposed by the accident, such as the employees’ lack of awareness of well control and inadequate well control education and implementation of well control technical measures. It was recommended that the company be given a major administrative demerit. 5. Yan Xianghui, deputy director of safety and chief of the safety section of the Second Drilling Engineering Company, as the person in charge of the safety contact point of Team 20508, is responsible for the supervision issues exposed by the accident, such as the employees' weak well control awareness, lack of well control education and implementation of well control technical measures, and it is recommended that administrative demerits be given. 6． Zhang Kezheng, deputy chief engineer and chief of the production technology section of the Second Drilling Engineering Company, is responsible for the problems exposed by the accident, such as the employees' poor awareness of well control and inadequate well control education and implementation of well control technical measures. It is recommended that the company be given a major administrative demerit. 7. Captain of Team 20508 of the Second Drilling Engineering Company (Party Branch * * ) Li Bin, who was primarily responsible for the problems exposed by the accident such as poor awareness of well control among employees, inadequate team management, labor organization, well control education and implementation of well control technical measures, recommended administrative dismissal and removal from the party branch. * * position. 8. Deputy Captain of the 20508 Team of the Second Drilling Engineering Company (Deputy Party Branch * * ) Ma Jinsuo, who bears important leadership responsibilities for the problems exposed by the accident such as employees’ weak well control awareness and inadequate well control education, recommended administrative dismissal and removal of the deputy party branch deputy director. * * position. 9. Shi Bingqiang, deputy captain of the 20508 team of the Second Drilling Engineering Company, was directly responsible for the problems exposed by the accident such as well control education and inadequate implementation of well control technical measures. It is recommended that administrative dismissal be given. 10. Li Gang, technician of the 20508 Team of the Second Drilling Engineering Company and on-duty cadre, was directly responsible for the poor well control awareness exposed by the accident and improper on-site emergency response. It is recommended that administrative dismissal be given. (2) Dagang Oilfield Branch 1. Xu Bin, deputy manager of the Oil and Gas Development Division, as the person in charge of drilling supervision of the construction unit, is responsible for the failure of supervision of the accident, and it is recommended that an administrative warning be given. 2. Liu Cunlin, chief geologist of the Fifth Oil Production Plant, as the person in charge of the well location design of the West 60-8 well, failed to provide adequate warning of the complex situations that occurred during the surrounding drilling process. He has certain technical management responsibilities for the accident and is recommended to be given an administrative warning. 3． Zhang Zhongshui, the drilling supervisor of the Oil and Gas Development Division's West 60-8 well, was directly responsible for the failure to perform his supervisory duties on site, and it was recommended that the employment contract be terminated. At the same time, Dagang Oilfield Group Co., Ltd. and Dagang Oilfield Company were instructed to further investigate and analyze the accident, handle other relevant personnel with leadership, management and operational responsibilities accordingly, and report the results to the group company for record. 4. Accident Lessons and Preventive Measures After the "9.9" blowout accident in Dagang Oilfield, the leaders of the group company attached great importance to emergency response and accident investigation. They immediately assigned leaders of the engineering technology and marketing department of the group company to lead relevant experts on-site to guide the rescue, rescue and disposal work, and gave important instructions on the investigation and handling of the accident. The main leaders of the two companies in Dagang Oilfield went to the site to organize and coordinate the accident rescue and aftermath treatment, controlled the blowout in a timely and effective manner, and organized the restoration of production as soon as possible. The blowout went out of control and caught fire, killing one person. The drilling rig and major equipment and facilities at the well site were burned, causing considerable economic losses. At the same time, the production of two drilling rigs nearby the same well site was also affected. The occurrence of this accident seriously disrupted the normal production and operation order of the company and exposed many weak links in the well control management of Dagang Oilfield. Especially when the group company has carefully learned the lessons from the "6.5" blowout accident in Jilin Oilfield, highlighted and emphasized the focus on well control safety, adopted a series of measures, and strived to achieve a significant improvement in the safety and environmental protection situation of the group company, such an out-of-control blowout accident has a bad nature, extremely bad impact, and painful lessons. One of the lessons: Not enough attention has been paid to the risk awareness of well control in new blocks in old areas. There is a lack of sufficient vigilance about the possible presence of bottom oil cap gas and dissolved gas in the Gangxi block of Dagang Oilfield, and the potential risks and hazards of the gas layer are not fully understood. The geological design does not provide any warning about oil cap gas. In particular, in recent years, many well kicks and overflows have occurred in development wells in the old area of Gangxi. The construction unit reported the situation to the development department of the oilfield company every time and requested adjustments to the relevant design requirements. However, neither the development department nor the construction unit conducted systematic analysis and research on these situations, and did not conduct in-depth research and detailed evaluation of the risks of the wells being drilled. The complexity of the geological conditions in the western Hong Kong area was not fully recognized, and the drilling design did not take further well control strengthening measures to address the possible oil cap gas in Well West 60-8. The construction unit did not formulate detailed well control measures for the drilling process, especially the prevention and control of formation fluid intrusion. Lesson 2: Insufficient training in emergency response capabilities and on-site practical operations for employees. In the past two years, the number of personnel in the well team's operating positions has been rapidly replenished. There are many new personnel and a concentration of personnel who need to participate in training. The relationship between work, school and rest is tense, and employee training is mainly limited to basic evidence collection requirements. The drilling rigs, devices and simulation scenarios used by employees to participate in training cannot meet the operational requirements of all types of drilling rigs and well control facilities, and the training effect and actual ability cannot meet the requirements of actual work. The main manifestations are that when an emergency occurs, employees cannot operate calmly and respond calmly, lack emergency response capabilities and the ability to handle accidents, and cannot shut down wells correctly. Team 20508 did not coordinate the relationship between training and actual production. During the drilling of the oil and gas layer in Well West 60-8, key personnel such as the drilling team captain, deputy captain, and safety supervisors all left the team to participate in well control training. As a result, there were few cadres at the drilling site, insufficient backbone strength, and a lack of effective command and handling of on-site emergencies. The work was focused on one thing but not the other. Lesson 3: The awareness of well shut-in is not strong and the well control skills are low. After the overflow occurred, neither the well team leader nor the driller realized that the oil and gas were flowing rapidly and fiercely. After the overflow was discovered, the awareness of well shut-in was not strong, and no shut-in measures were taken in time. Instead, the "four-seven" action was performed mechanically. When the complex emergency situation of sudden blowout and loss of control of the swimming system occurred, the personnel on site were at a loss. They also tried to shut in the well through the conventional shut-in steps starting from lifting the drilling tool. This exposed that the team members did not have solid basic well control skills, insensitive responses, irregular movements, untimely movements, unskilled operations, and missed shut-in opportunities. Lesson 4: The understanding of reservoir oil and gas is superficial and one-sided. Based on incomplete near-well data, geologists did not give any hints about the possible existence of bottom oil cap gas or dissolved gas. However, in actual drilling operations, these oil cap gas or dissolved gas are often the first factors causing well control dangers. On-site engineering personnel lacked basic knowledge of oil and gas accumulation and superficially understood the oil layers proposed in the geological design as containing only oil and no gas. Construction workers are not very alert to prevent and detect overflow when treating the layer designed as an oil layer. ； Even after the overflow was discovered, the response to the well shut-in procedure was not fast and the shut-in action was not decisive. In order to effectively learn from the lessons of the "9.9" blowout accident in Dagang Oilfield, draw inferences from one example, plug work loopholes, improve well control safety awareness, further improve the group company's well control safety work, and promote a fundamental improvement in the group company's well control safety work, the investigation team proposed the following work measures. One of the measures: Raise awareness, strengthen responsibilities, and fully implement the well control safety responsibility system. First, the "9.9" blowout accident in Dagang Oilfield was notified to all oil and gas field enterprises of the group company and various professional companies engaged in exploration and development engineering and technical services, warning and urging all relevant units to learn lessons from the accident, further enhance well control awareness, carry out in-depth special rectification of well control work, and effectively do a good job in well control work ； The second is to further rationally and overall consider production capacity construction, strengthen safety demonstration work in aspects such as program demonstration and design, and provide the well team with more comprehensive prompt information and more operational geological and engineering design. ； The third is to further investigate the cause of the accident, analyze the root cause of the accident, learn from experience and lessons, and constantly revise and improve well control regulations and technical procedures. Oilfield companies and drilling companies in particular must be aware of the great dangers that may be caused by oil/water cap gas and dissolved gas, and attach great importance to new oil layers in old areas and oil/water cap gas and dissolved gas in new layers in old areas as important risk sources in terms of ideological understanding, technical ideas, basic management, safety investment, and enforcement of regulations. ； Fourth, we must follow the Group's "Opinions on Further Strengthening Safety and Environmental Protection Work in Oil and Gas Field Enterprises", further strengthen the principle that administrative officials are the first person responsible for safety and environmental protection, further improve the well control safety supervision network, and effectively strengthen well control work in all aspects such as geological engineering design, on-site facility layout, and production operation. ； Fifth, to strengthen front-line team management and grassroots construction, it is necessary to select experienced and responsible cadres from the agency and second-line teams to the first-line well teams with new personnel, less experience, and weak foundations. They should stay in place to help, make up for it in a timely manner, and cultivate the technical strength and management capabilities of these well teams as soon as possible, so as to effectively improve the well control emergency response capabilities of the team and on-site employees. It is necessary to effectively strengthen team building, strengthen grassroots management, and lay a solid foundation for grassroots safety. Measure two: Strengthen management, refine measures, and pay close attention to implementation. First, organize production operations in a scientific and balanced manner, arrange well sites, drilling rigs and auxiliary facilities according to specifications and standards, and avoid deploying multiple drilling rigs to operate simultaneously in a small area, occupying each other's sites and interfering with each other's construction operations. ； The second is to further strengthen the distribution and prediction of shallow gas and the possible existence of oil cap gas and dissolved gas enrichment areas in high parts of the reservoir structure. Fully understand the high risk of gas-bearing reservoirs to drilling operations. The geological design and engineering design should collect all relevant data on adjacent wells and adjacent areas and give clear prompts. ； Third, strengthen information communication between companies and business and technical departments. Oilfield development departments, production operation departments, and design units should take the initiative to understand and master the dynamic conditions of wells under construction and surrounding oil and water wells. In particular, if the mud density needs to be increased due to overflow, they should promptly summarize, analyze and study, formulate corresponding measures, and timely improve and perfect drilling geology and engineering design. ； Fourth, strict design procedures and strict control of design approval. Technical departments and design units should strictly implement technical policies, not only strictly implement the procedures and steps of design preparation, but also strictly implement a series of well control regulations of the group company and well control implementation details of the oil area, and strictly control the qualifications and qualifications of the three categories of personnel in design preparation, review and approval ； Fifth, geological design attaches great importance to the research, screening and prompting of possible oil, gas and water layers in gas-bearing oil layers, water layers and non-target layer well sections. Engineering design should formulate corresponding technical measures for each prompt of geological design. The construction team must always maintain a high degree of vigilance and strengthen overflow monitoring ； Sixth, during the drilling process, any overflow or "suspected overflow" must be shut down immediately before taking throttling cycles or other corresponding technical measures to deal with it. ； After drilling the target layer, the well should be closed and the mud should be circulated through the choke and kill manifold when drilling above the target layer and when drilling to the bottom of the well. Seventh, the key links should be grasped. During major construction and special operations, as well as after drilling oil and gas layers and when underground complications arise, drilling supervisors and well team cadres should formulate, supervise and implement the design content and various important technical measures on site. Measure three: Strengthen team building and employee training, and improve the risk awareness and technical quality of all employees. First, it is necessary to strengthen team qualification management and personnel management, strengthen the training and deployment of on-site production backbones, optimize the allocation of team and equipment resources, and effectively manage personnel in key positions. ； Second, it is necessary to build well control training experimental wells with actual overflow and blowout capabilities as soon as possible. All members of the drilling team should pass actual combat drills and pass the assessment before they can work in the well team. ； Third, the well control training for the well team and production team should highlight the timely detection of overflow and timely shut-in, especially to improve the production team's awareness of well shut-in. Well control training should set up overflow and blowout scenarios based on blowout examples, and train the team on well shut-in operations, so that the team can practice the "final kick" of on-site well control and win the blowout encounter. ； The fourth is to strengthen the ability assessment of personnel in key and important positions, focusing on well control knowledge training, risk management training and skills training for grassroots well captains, drillers, derrick workers and other positions. It is necessary to strengthen on-the-job continuing education and test the emergency response and control capabilities at work based on actual combat. Measure four: Carry out in-depth well control safety inspections, further strengthen well control inspections, and comprehensively investigate and manage potential safety and environmental hazards. First, it is necessary to further implement fine well control safety inspections and inspections, enhance the operational efficiency of the well control management system, and pay close attention to the implementation of well control measures and well control systems. ； The second is to formulate practical disposal processes and measures for complex situations such as well kicks, overflows and blowouts that are prone to occur in new areas in old areas. ； Third, we must deeply learn the painful lessons from this accident, carefully investigate and manage the safety and environmental hazards of well control, completely eliminate the safety hazards existing in drilling and completed drilling, and achieve thorough management without leaving any dead ends. ； Fourth, on the basis of well control inspections, targeted technical measures must be further formulated. In addition to the construction unit dispatching drilling supervision in key processes and key wells, the construction unit must send personnel to the well to monitor, implement the safety contact system, supervise the drilling team to strengthen well control drills, implement well control measures, and ensure well control safety. Dagang Oilfield "9.9" Blowout Accident Investigation Team This post was last edited by Final Fantasy on 2008-2-4 23:31 ]