Inspection of risers with submarine robotics; technology, risks and regulations

Transcription

1 Inspection of risers with submarine robotics; technology, risks and regulations By: Jarmo Hirvonen (IST179965), Taneli Riuttamäki (IST179969) and Kristian Mollestad (IST179985) Course: Technological and Natural Risks 2014 (RNT 2014) University: Instituto Superior Técnico Lisboa, I

2 Table of contents 1 Introduction South Atlantic drilling risers Environmental window Application of submarine robotics to risers Definitions ROV AUV Comparison Maintenance Reliability Application in The South Atlantic Problems Ultra Short Baseline, USBL Solution Arguments for AUV over ROV Deepwater Horizon oil spill case study The accident Use of robots during the accident Problems associated with submarine robotics Risks (IRGC) Pre-assessment Appraisal Characterization and evaluation Management Communication Regulations of submarine robotics Conclusion Resources Appendix 1 Risk table II

3 List of figures Figure 1 - Riser... 2 Figure 2- Illustration of solution... 7 Figure 3 - DNV impact situation [14] List of tables Table 1 - Comparison of AUV and ROV... 4 Table 2 - DNV collision energies and causes for dents in steel pipe [14] Table 3 - Suggested regulations for submarine robotics III

4 List of abbreviations ASC AUV COLREG DH DNV Automated Surface Craft Automated Underwater Vehicle International Regulations for Preventing Collisions at Sea 1972 Deepwater Horizon Det Norske Veritas IRGC The International Risk Governance Council LWD ROV UDW USBL ASC AUV COLREG Logging While Drilling Remotely Operated Vehicle Ultra Deep Water Ultra Short Baseline Automated Surface Craft Automated Underwater Vehicle International Regulations for Preventing Collisions at Sea 1972 IV

5 1 Introduction The rising oil prices and growing technology have made oil companies to explore oil from the places that were not technically or economically possible before. In few years the exploration has increased in ultra-deep waters (UDW) mostly in South Atlantic. In this paper we concentrate on South Atlantic oil exploration and the use of submarine robotics and the risks that are related to robotic collision. We are using several sources to find information for this paper. Our main sources are a case study and scientific papers. We also contact professionals to have the newest knowledge to add to our work. We are studying the advantages of using robotics with risers and also the new risks involved with them. We are also interested in regulatory frame works for submarine robotics. The goal of this study is to recognize the biggest advantages and risks of using submarine robotics and make recommendations for future regulations of using submarine robotics. This study is a basic study to help the oil industry to develop the oil drilling operations in South Atlantic with using robotics to make the drilling safer and more efficient. This study contains an introduction to oil risers and underwater robotic technologies such as Remote Operated Vehicle (ROV) and Autonomous Underwater Vehicle (AUV). After evaluation and discussion with an cybernetics expert, a solution for inspection of risers are presented. We are using a case study from Deepwater Horizon to present real data of using robotics and understanding the real risk involving riser failure. We assess the possible risk of collision between robots and riser and in the end of the study the recommended regulations are presented. 1

6 2 South Atlantic drilling risers An oil riser is a part of oil drilling system. It is a long pipe that connects wellhead in seabed and the oilrig. The well is drilled trough the drilling riser. It enables the drilling of mud with combination of oil, gas, water and sand. The mud flows up to the oil rig s separation tanks through oil riser. [1] An oil riser is necessary in oil well drilling because without the riser the mud would stay in the seabed and block the well. [2] It is known in the oil drilling industry that knowing the condition of the oil riser is important for safe and successful operation and production of offshore oil fields. [1] There are many types of risers that can be used in ultra-deep water (UDW), such as flexible risers, toptensioned risers and steel catenary risers. But in this study we are focusing on top-tensioned risers with two casings. Figure 1 - Riser Figure 1 shows that the drilling riser has to two casings. The pipe located in inner casing is called a drill pipe where the drilling fluid is pumped down to the well. The drilling fluid gathers the mud and the increasing pressure makes the cuttings and mud rise up through the outer casing. The mud is pumped up to the oil rig and sorted in the sorting containers. In picture 1, at the down end of the riser there is a LWD (Logging while drilling) tool. LWD tool is a sensor, which can transmit partial or complete measurement data to the surface while 2

7 the drilling is on-going. LWD uses a lot of different technics of measurement like: Gamma ray, Sonic and borehole images. [3] A blowout preventer is place between the wellhead and end of riser. The blowout preventer contains one or more mechanical valves, which are designed to release the pressure in the outer casing in case of erratic pressure release from the oil well. In case of a high pressure eruption the blowout preventer is also designed to cut the link between the riser and the wellhead to prevent a blowout in the drilling platform. The pressure of the wellhead has to be constantly monitored. [4] 2.1 Environmental window Working in South Atlantic UDW conditions causes a lot of new challenges that have to be overcome to minimize the risks. Many of these challenges are related to the environmental aspects of the UDW conditions, but some are related to the technical aspects of UDW oil drilling. Most of these challenges involve risers and the assembling of the drilling equipment. The environmental challenges that come from the deep water are increased pressure and absence of light. Because of the high pressure divers can t be used for inspection or maintenance. Because of this maintenance, inspection and installation in the oil riser have to be done by underwater vehicles and they have to be equipped with heavy lights. However, using underwater vehicles cause a risk of collision between other vehicle and the riser, which may cause leakage or even explosion. One of the challenges associated with the riser is that it is hard to determine how the riser will work before it is tested in real conditions. When the riser is installed at deep sea, the length of the riser is long. Because of this, there has to be additional buoys and supports to lower the weight of the riser structure. The riser structure is also affected by underwater currents, which may cause swaying and reduce fatigue of the riser. 3

8 3 Application of submarine robotics to risers 3.1 Definitions ROV A Remotely Operated Vehicle, ROV, is an underwater robotic controlled by an operator on the surface. The ROV is powered and operated via a tethered cable from a support station. The modern ROV-vehicles have a multi-role function and are built to have sufficient manoeuvrability for the required tasks. Historically, the main tasks for the ROV are inspection and working AUV An Automated Underwater Vehicle, AUV, is a self-contained underwater vehicle without any physical connections to a support station, unlike the ROV. Meaning that the AUV is carrying its own energy source and power conversion system. It is designed to be either preprogrammed for its tasks or controlled via acoustical signals sent from a surface control point. The vehicle is required to sense and interpret the environment, to locate and position themselves and avoid obstacles, in addition to make real time decisions regarding the task. 3.2 Comparison This table highlights some of the major technological considerations and differences that exist between ROV and AUV. Table 1 - Comparison of AUV and ROV ROV AUV Advantages - Full operator control - Power source available from topside - Wide band communication - Immediate feedback of manoeuvres, errors and data to operator - Minimal required support facilities - High speed - Long ranges - System operator costs are low - Larger underwater operator radius Disadvantages - Limited range - Limited speed - Additional drag force of cable - High overall system cost - Limited communication - Limited work capability - Energy limitations - Requires adaptive intelligence - Reliability 4

9 The disadvantages for the AUV stated above are also the challenges associated with oil exploration in the South Atlantic, and the inspection of risers. In paragraph 3.5 those challenges will be highlighted and solution will be presented. 3.3 Maintenance Maintenance of seafloor equipment can be divided into three categories: inspection, replacement and repair of equipment and components. The maintenance tasks can be performed by divers in shallow waters, but is often performed by submarine robotics, e.g. ROVs, both for shallow and deep water applications. ROV s reduce the personnel risks associated with diving. This paper will investigate the inspection of seafloor equipment, hereunder risers, with a hybrid solution of AUV and ROV. 3.4 Reliability AUVs are complex vehicles. One of the main challenges is the lack of proven reliability coupled with minimum risks. Over the years, there has been speculation over their marketability, due to the mentioned challenges. Therefore, the commercial world has been reluctant to investments in the technology, needed to prove the reliability. One of the main reasons for this is that ROVs covered application needs. Deep-sea oil exploration presents new problems and task requirements. The impending requirement for AUVs will be targeted at applications, which simply cannot be accomplished in any other way. With this basis, the market has proven to be more interested in the commercial use of AUV. 3.5 Application in The South Atlantic Problems Limited communication is one of the main challenges for an underwater vehicle at deep sea. Communication is a mandatory requirement for the inspection of risers and for positioning of the vehicle. The vehicle has to send real time images and immediate updates of the inspection. Today, there exist a variety of communication systems: 1. Acoustic signals. Maps of the seabed are based on acoustic signals and represent the vision for submarine robotics. Transmitting acoustic signals from the seabed to the surface is very hard to manage, especially at deep sea. 2. Optical signals. Consists of light transmitted through cable, air or water. 3. Ultra Short Base Line, USBL. The USBL-technology has developed significantly the last years. Further description is given in the next paragraph,

10 3.5.2 Ultra Short Baseline, USBL The problem of navigation can be stated as to determine the position and the relative orientation to an object, in this case a riser, with a reference point. A specific reference point is presented in the next paragraph, Solution. The USBL technology is widely used as underwater tracking system. The system consists of a transceiver assembly: transducer elements, which are mounted in a convenient geometry. This transceiver is mounted on the tracking vehicle. The vehicle that should be tracked, in this case the AUV, contains a transponder, which receives the acoustic signal and emits its own signal to the transceiver assembly. The time of arrival, the time it takes for an acoustic signal to travel between the transceiver and the target, is measured by the USBL-system and converted into a range. The phase differences of the reception of the signals at the multiple transducers are used to calculate the angel of the arriving signals. In total, this gives the accurate position of the subsea vehicle. The measurements of the underwater vehicle s position are only known to the system carrying the USB-transceiver. The baseline expression in USBL refers to the distance between the transducers in the transceiver assembly. It is required to use advanced signal processing techniques because of the extremely short distances between the transponders. Acoustic signals Solution After meetings with Professor Antonio Pascoal, at Instituo Superior Técnico, we have come up with a solution where the ROV-technology is incorporated to the AUV-technology, while it maintains the benefits of an AUV-design. The communication system consists of an USBLsystem and use of umbilical to the surface. Then, the USBL-system is used to determine the relative position of the AUV to the risers. Three vehicles are operating together: AUV, ROV and an Autonomous Surface Craft (ASC). The AUV is the operating vessel, inspecting the riser. It is carrying its own power supply, but is obligated to recharge. The ROV is operating at the same depth as the AUV, and are connected with cable to the surface, ASC, and the AUV. Electricity is transmitted from the ASC, so the ROV can recharge the AUV. This makes the work of the AUV more efficient, since it does not need to move to the surface to recharge. 6

11 The following figure illustrates the solution: Figure 2- Illustration of solution The most crucial factor affecting the submergible vehicle s performance is the effect of drag on the vehicle and the drag forces on the cable. That in fact can be much greater than the drag force on the vehicle itself. The reason for this can be seen from formula 1, giving the drag force for a tethered vehicle:! 𝑅! = 𝜌 𝐴! 𝑉!! 𝐶!" + 𝐴! 𝑉!! 𝐶!"! (1) Where: 𝜌 - density [kg/m3] A - characteristic frontal area [m2] V - velocity [m/s] Cd - non-dimensional drag coefficient Subscripts c and v refer to the cable and the vehicle respectively. A longer and thicker cable gives greater drag force and makes the vehicle hard to manoeuvre. Thus, representing a challenge at deeper sea. The solution presented in this project takes the problem into account. The cable from the ROV to the AUV consists only of optical fibres, which is very thin, meaning that the drag force more or less can be neglected. The fibre cable 7

12 is necessary because of the mandatory requirement of real time communication with the surface. This cannot be obtained by acoustic signals. The position of the AUV is determined by the USBL-system, presented in the last paragraph, Ultra Short Baseline, USBL. The ROV is mounted with a transceiver assembly and the AUV with a transponder. Signals are sent through optical fibre cable from the ROV to the AUV. When the signal is received by the AUV a transponder immediately emits acoustic signals. The signals are received by the ROV-transducers and the position of the AUV can be determined. The position is only known to the ROV. The ROV and the ASC can now be positioned according to the AUV position. This is to avoid problem with the optical fibre cable and the riser. In addition to this, the fibre cable is pulled in or out of the ROV as the AUV moves, so the length of the cable are regulated Real time images and information about the inspection are sent through the optical fibre, to the ROV. Then, they are sent to the ASC through the umbilical, and at last with radio signals on the surface to the operating station. This gives a live feed of the inspection, which is mandatory Arguments for AUV over ROV ROV-technology is widely used in the oil industry for operations underwater. This included deep-sea operations, up to 3000 meters. So the question is why one should choose AUV technology, or hybrids, instead of the existing ROV solutions. The ROVs are considered more reliable due to lack of experience with use of AUVs. The oil industry can be considered as conservative still using ROVs. The AUVs have much less operating costs because they are automated. They can be programmed to perform routine inspections. They can operate around the clock, without requiring an operator. As discussed earlier, the manoeuvrability of the ROV is hard because of the umbilical. The AUVs are free of the umbilical and are smaller in size, making them more applicable. The disadvantages of an AUV; limited communication and energy limitations, stated in Table 1 are eliminated with the solution presented in this project. 8

13 4 Deepwater Horizon oil spill case study Deepwater Horizon (DH) was a mobile oil rig owned by BP operating in Gulf of Mexico in The oil rig was built to operate in very deep water. It had the deepest oil well in oil drilling history at vertical depth of m. The water depth were 1 259m. In year 2010 the explosion in the oil rig caused the death of 11 people and eventually it sank the oil rig which caused the biggest oil disaster in US oil drilling history. The situation lasted two days before the explosion happened. During this time experts tried to do everything they can to prevent the disaster from happening. [5] 4.1 The accident On March 2010 BP noticed that there was a problem with the well control. To control the situation BP would have to pluck the well with special nitrogen-foamed cement. [6] The cement was supposed to protect the outside of the well pipe and prevent the gas leakage from the well. However, the cement wall failed and a huge column of natural gas were pushed up to the riser. The high pressure of gas was pushed up to the rig and the extreme pressure cause it to explode on the oil rig. [7] Riser is always equipped with blowout preventers (BOP). The riser used by BP had valves to close up the riser casings and valves on the side to lower the pressure in case of accident. In case of high pressure in the well, there were valves in place to prevent cement and mud blowing back in the riser. In this case these valves didn t close properly which let the high pressure of gas go all the way up to the oil rig. In this case the BOPs were not enough alone to lower the pressure. There was also one final fail-safe which was a BOP meant to cut through the drill pipe and seal it up. However, the final fail safe failed to work. [7] BP was accused many times of disregarding many safety issues. They were accused of using unstable cement to block the well, which may have cause the cement failure. BP was accused of making a trade-off between safety and cost and the trade-offs were made in favor of cost. [8] Deepwater Horizon was operating for nine years. During that time the coast guard of US has reported multiple problems. DH suffered multiple spills, fires and even collisions during that time due to human errors, equipment failures and bad weather. Any of these accidents didn t cause major hazards but if small problem is not fixed properly it may lead to big hazard. [9] 4.2 Use of robots during the accident During the DH accident the experts tried to do everything to prevent the disaster. Because DH operated in such deep water a human divers could not try to prevent the problem. Because of this a dozen ROVs were sent down to fix and save situation. ROVs were used 9

14 successfully but ROV accidents caused some additional problems with the risers. Deepwater Horizon accident was the first in history were such many ROVs were used simultaneously. During the crisis even AUVs were used to estimate the scale of the disaster. [10] Normally ROVs are used for maintenance, inspection and setting up the equipment underwater. In the DH accident ROVs were used on their limits to reduce the effects of the disaster. ROVs were successfully used on solving the problems underwater. After the riser blowout preventer failed to seal off the drilling pipe, the ROVs were used to jam it into place. After this the ROVs were sent to saw of the jammed pipe. ROVs were also used for sealing the well up with large dome and later for installing oil-collecting cap in the disaster area. In DH disaster also AUVs were used. A number of AUVs were deployed to estimate the scale of the spill. They were sent to roam the area the spill area and collect water samples to detect the oil and chemical in the water. [11] 4.3 Problems associated with submarine robotics Even though the robots were used successfully in the DH disaster there were also an accident related to robots. BP placed a contamination cap to prevent the oil spreading. However, robot collided with the vent of the cap and shutting it off. BP was forced to remove the contamination cap and install it again and because of this more oil was spilled in to the water. BP used ROVs later for inspecting and checking for safety of the contamination cap. [12] 10

15 5 Risks (IRGC) IRGC s risk governance framework distinguishes between analysing and understanding a risk for which risk appraisal is the essential procedure and deciding what to do about a risk where risk management is the key activity. [13] The framework is also supposed to raise questions about the risks and take into account the views different stakeholders might have. In this paper IRGC risk governance framework is used for collision risk that using ROVs undersea might cause in the ultra-deep water environment of South Atlantic. IRGC framework includes five parts, all are covered here; risk pre-assessment, appraisal of the risk, characterization and evaluation of the risk, management of the risk and finally communication about the risk. 5.1 Pre-assessment In this paper we have been assessing the use of ROVs and AUVs. This is done because the oil exploration in South Atlantic. In this area, the water depth is big issue; conditions change to ultra-deep water; pressure increase is too big and also lots of power is needed for lightning up the dark water. Because the oil industry is more interested to start drilling in South Atlantic it also means an increase in the amount of different kinds of oil drilling equipment in the South Atlantic. Because of the depth of the sea, the inspection and maintenance of the drilling equipment has to be done with ROVs and AUVs. Increase in the amount of ROVs in the sea also increases the probability of the risks they can cause to the industry. In this paper we are concentrating on the risk with the collisions caused by the ROVs. We previously saw in paragraph 5.2 how ROVs were used during the Deepwater Horizon oil accident by BP. Multiple ROVs were used successfully at the same time. As mentioned, an accident with use of ROVs occurred, when one of them closed valve of the containment cap and this resulted in new problems. Also the collisions caused by ROVs might cause even bigger problems. ROVs can be very heavy and have big impact force during collisions. Also the currents subsea can make it hard to maneuver a underwater vehicle. This increases the risk of collisions. Increase of oil drilling in South Atlantic also increases the risk of oil spill in the sea. That is why the governments are interested to know what is being done to ensure that the drilling is safe. This is one reason that regulatory framework should be developed for submarine robotics. The oil industry already has international cooperation, which have proven to be important when accidents happen. 11

16 5.2 Appraisal The main part of this work is to estimate the risk and hazards caused by using robots in deep water, concerning the collision of robot against robot or robot against riser. It is of great importance that use of robotics at deep sea are safe and the operation is done according to the international regulations. The possible risks of using submarine robotics are listed in appendix 1. The robot may collide with the riser or another robot. When ROV collides with riser it may cause dents, fracture or even collapse the riser pipe structure. ROV can also hit to essential parts of riser such as connectors, buoyance cans or other parts which can be easily broke down or malfunction. Robotic units can also collide with each other, which can force it to return to base for repairs. For worse cases the collision can sink one or both of them. Every collision usually requires repairing, and in the worst cases the riser or equipment needs to be taken out of operation for a long time and the damaged part needs to be replaced. We are using Det Norske Veritas, DNV, study for undersea steel pipe that is being hit by falling object to illustrate the collision situation with robot and riser pipe. In the figure 3 is the collision situation where an edge bladed object hits in 90 degree angle to the pipe. [14] Figure 3 - DNV impact situation [14] The situation psychically can be considered to be similar to robot colliding with steel riser, however this illustration do not count the pipe moving back in impact which can be counted to reduce the impact energy. This illustration is concidered to be the worst case scenario for example robot colliding riser pipe while carrying sharp object. DNV has simulated this situtation and defined the formula 2 for energy that is required to cause dent δ to the steel riser. [14] E = 16!!! m!!! D!!!! (2) 12

17 Where: m! = plastic moment capacity of the wall = 1 4 σ! r! δ = pipe deformation, dent depth t = wall thickness nominal σ! = yield stress D = steel outer diameter Working class ROV may weight over 3000 kg and their maximum speed can reach 2m/s in water. The speed can be affected with underwater currents and the maximum speed can variate when descending or ascending. The riser can also be affected with currents which can cause swaying to the riser. The kinetic energy caused by riser cannot be accurately estimated but it should be taken into a concideration. The kinematic energy involved in the collision can be estimated with formula 3: E!!"! =!! mv! + E!!"#$! (3) If concider the facts known from the heavy ROV we can calculate an estimation of the kinematic energy. E!!"! =! 3000! 2! = 6000J + E!!"#$! = 6kJ + E!!"#$! (4) DNV has simulated different energies and causes to the steel pipe in the table 2. Table 2 - DNV collision energies and causes for dents in steel pipe [14] The estimation kinetic energy for working class ROV was calculated to be around 6kJ. According to the data in table 2 it is possible that robot can cause minor damage when colliding to the pipe. However, there is still factors concerning the collision area and angle 13

18 [15], swaying of the riser and deep water currents. Still more conciderable damage can be caused to the additional drilling equipment. The possible causes of ROV colliding with riser, drilling equipment or another ROV are listed in the appendix 1. Accidental impact in the table describes ROV collision. ROV collisions are caused of human errors, environmental factors or technical failures. Human errors can be mitigated by improving training and adding technical fail safes. Technical failures can be avoided by increasing inspection of the equipment and maintenance. Environmental factors can be unexpected forces caused by currents for example. These can be mitigated by studying the ultra-deep water conditions and adding software and technical fail safes. Technical fail safes can be sensors to detect possible hazards before they are happening. This can be done by monitoring the water currents, ROV speed and distance to objects. There can also be software to help the operator to control the ROV for example mitigating fast turns or accelerations. In other technical fail safes are used to reduce human and environmental errors. In future goal is to remove human operator as much as possible to have AUVs doing ROV jobs, however this is still very far from being possible with current technologies. 5.3 Characterization and evaluation Collision may cause oil leaks or bigger oil accidents such as the containment cap accident in DH. The oil leakage causes environmental damage, which is very hard to contain or fix. It can harm the livelihood of fishermen, as well as harming the everyday life of people in contact with contaminated water. It kills animals especially fish and birds. It can also cause poisoning for human if the contaminated water is consumed. There is also an ethical issue in using ROVs. The operator can feel that he is guilty of causing and accident if it happens while he is operating the ROV. There is always also a risk of wrong use. ROV operator may try to cause accident in purpose. There is also a question of information security. ROVs that could cause a risk of collision could be substituted AUVs, as the solution in this work presents. They are autonomous so there is no risk of human control errors. The risk of ROV collision can be reduced with more advanced technology, supervision and continuous training of operators. The technologies could be sensors, which warn about collision and systems that reduces human errors. Also new regulation framework is needed to guide oil drilling companies and robotic manufactures to operate safely. 14

19 5.4 Management Management of the risk is on the responsibility of the oil companies. They should be observed by regularly authorities, to ensure that the maintenance of robots is done correctly. Cooperation between manufacturing companies and the oil companies operating the vehicles is important to minimize the risks. Managing the risk can be done by technological advancements, by good training of the ROV operators and by strong and clear regulatory work. Regulations could be done so regular maintenance for ROVs have to be done and documented correctly. Also trainings for operators should be documented and their knowledge of new risks and such should be kept up to date. ROVs software should be continuously developed so they have better systems for avoiding collisions also the speed of ROVs could be limited to lower the impact force ROV can cause. Additional bumpers could be installed to ROVs or drilling equipment to reduce the possible risk. It has to be carefully observed that different stakeholders do not try to avoid their responsibilities. That is why all the operations done by the ROVs should be properly documented so it can be seen afterwards everything had been done as required. Same principle should be used for the training of the ROV operators. This makes it possible for regulatory authorities to audit documents and give feedback before anything disastrous may happen. 5.5 Communication Risk communication is essential in the risk management to ensure that proper solutions are found, developed and used. Communication is also very important to ensure that public is aware of the safety of the submarine robotics used. With this communication, the media can be helpful by making the robots better known for the public. The information that is given to the public has to be unambiguous so it cannot be interpreted wrong way. This is especially true with the regulatory information. The communication about the possible risks with collisions should also be communicated between oil companies, robot manufacturers and regulatory authorities to ensure continuous development of robots. Regulatory authorities should make regular auditions to oil drillings sites to make sure that regulatory frameworks are properly followed and documented. Also companies should communicate in case of near miss situations and in real accidents to regulatory authorities. This should be done so better risk management system could be developed. 15

20 As open as possible reporting system for near misses and real accidents should be used. This ensures that all the companies are aware of the possible risks and can more easily manage them. This should be done so that the company reporting near miss situation or accident does not give advantage to other companies in business competition. Possible the source of the near miss could be only known by independent regulatory authority so companies are protected. 6 Regulations of submarine robotics The ROV are tethered and remotely operated by vessels at the surface. These types of robotics are under the same legislation as the ship and are to be considered as a part of the main vessel. The AUVs, on the other hand, are to be considered as separate entities. Because they are autonomous, however, they create a gap in the legislation. An AUV is not considered a vessel per definition. Existing domestic laws and international treaties are limited to vessels, and therefore not AUV. The question is then where to fit the AUV in the current regulatory structure. The government does not provide any regulations because of new complex technology and difficulties with classification of the AUV. The use of AUVs are increasing and growing in popularity. Business and organisations gain access to AUV technology in increasing extent. This provides a need for creation and provision of legislation and regulation. It is of great importance that the AUV operator is aware of the associated risks with AUVs. Not to mention, how to manage those risks. The main focus of this paper is the risk associated with collision. Even though the risk of collision is small, the damage could be very high due to loss of the AUV or damage to other structures or ships. The operators need to be aware of their obligations with regard to avoidance of collision and how to minimize the risks of collision. In 1972 the International Maritime Organisation developed International Regulations for Preventing Collisions at Sea, COLREG. These regulations only include vessels operating on the water. There are no specific requirements for vessels operating under water. Thus, the COLREG are only applicable for the AUV when operating at the surface and if the AUV are to defined as a vessel. If the AUV is assumed to be classified as a vessel, the operators would have to follow requirements stated in COLREG to reduce the risk of collision. This includes maintenance, safe speed and proper lightning. Applying some of these requirements may limit the application of the AUV. However, COLREG provides an exception: «Vessels of special construction or purpose which cannot fully comply with the light, shape, and sound signal provisions of 72 COLREGs without interfering with their special 16

21 function may instead meet alternative requirements [17] Therefore, the operator can apply for a «Certificate of Alternative Compliance», allowing alternate installation of the safety features. This is to be considered as a part of the risk management. Although, AUVs are unlikely to be considered a vessel by law, operators are recommended to act according to COLREG when the AUV operates at the surface to reduce the concern for collision and damage. For ROVs and AUVs there is no regulation framework in place, concerning the collision accidents. In this paper we assessed the possible risk for ROV collisions. We have defined suggested regulations that should be included in the regulation framework. The suggestions can be seen in table 3. Table 3 - Suggested regulations for submarine robotics Regulated factor Operator training Reporting of near miss and accident situations Speed and distance limit ROV maintenance reports Technical fail safes mandatory Suggested regulation ROV operators have to be trained and documented according to the international regulations. All accidents and near misses have to be reported and shared to a regulations organisation. Near misses can be reported anonymously Speed and distance of ROV near drilling equipment should be regulated. This reduces the impact frequency and force. ROV maintenance has to be recorded and reported. Framework for required technical fail safes have to be defined. All the drilling companies have to have this fail safes in place. 17

22 7 Conclusion The rising oil prices and growing technology have made oil companies to explore oil from the places that were not technically or economically possible before. The most relevant area for exploration is in South Atlantic offshore. South Atlantic offshore oil is located in ultra-deep waters. In this UDW conditions divers can t be used for work so robotics have to be used for maintenance, inspection and assembly. In oil industry ROVs are used are used for inspection, maintenance and assembling drilling equipment and AUVs are used for inspection. In this study the main research concern was the new risks that come with using submarine robotics and the regulation frame work that should be defined for using robotics. The main risk we are concerned is the robot collision. We are also studying the new robot technologies available in future. As the future set new requirements for oil exploration and the development of new technology takes place, it is very likely that the AUVs will be implemented in new solutions. This project presents a solution when AUV and ROV work together and complement each other. The AUV performs autonomous routine inspection and have the opportunity to recharge on the ROV. Ultra Short Baseline system is used to determine the position of the AUV, positioning the ROV and the Autonomous Surface Craft. This is a measure to minimize the risk of collision, using new well-developed technology. In this study we found that ROVs can cause minor damage to the steel plated riser pipe with collision. However, the damage can be more severe if the collision is done with other drilling equipment or other ROV. The effects of collision to the riser pipe can be small dents, damage to the armour plating or decreased fatigue. The factors, which may affect the collision damage, are the riser characteristics, ROV weight and speed, the collision angle, swaying of the riser and possible currents, which affect ROV speed. We made a suggestion for regulatory frame work concerning the ROV collision. The most important regulations found were limitation for ROV speed and distance from drilling equipment to reduce the impact force. Also all the accidents, near misses have to be reported to the regulation authorities and ROV maintenance and personnel training have to be documented. Training has to be done according to the international regulations and all the necessary technical fail safes have to be in place for the ROVs. 18

23 8 Resources [1] What is an Oil Riser by Peter Stern, 2010 Sciences 360. [online] Available at: [Accessed 2 March 2014]. [2] Schlumberger. Oilfield Glossary. Drilling. [online] Available at: 20riser. [Accessed 2 March 2014]. [3] Wikipedia, (2014). Logging while drilling. [online] Available at: [Accessed 5 March 2014]. [4] United States Department of Labor. Blowout Preventer. [online] Available at: [Accessed 5 March 2014] [5] Wikipedia, (2014). Deepwater Horizon. [online] Available at: [Accessed 16 April. 2014]. [6] J. Gills, J. M. Broder. The New York Times. 10 May Nitrogen-cement mix is focus of Gulf inquiry. [online] Available at: ewanted=all&_r=0 [Accessed 16 April 2014]. [7] E. Mayer, D. Shea. The Times PICAYUNE. What happened on the Deepwater Horizon. [online] Available at: [Accessed 16 April 2014]. [8] BBC News. 9 Nov Gulf oil spill firms 'complacent'. [online] Available at: [Accessed 22 April 2014]. [9] F. Jordans, G. Burke. Huffingtonpost.com. 30 April Rig had history of spills, fires before big 1. [online] Available at: [Accessed 16 Jun. 2014]. [10] Spectrum.ieee.org. 30 July The Gulf Spill's Lessons for Robotics - IEEE Spectrum. [online] Available at: [Accessed 15 May 2014]. [11] P. Newman at Douglas-Westwood. Remotely operated vehicles involved in the Deepwater Horizon response. Available at: [Accessed 16 May 2014]. [12] NY Daily News, (2014). BP's containment cap replaced on gushing oil well in Gulf after Deepwater Horizon rig explosion. [online] Available at: [Accessed 16 May 2014]. [13] IRGC, An introduction to the IRGC Risk Governance Framework. [14] Recommended Practice DNV-RP-F107. Risk Assessment of pipeline protection. October [15] A. J. Kalleklev, K. J. Mørk, N. Sødahl, M. K. Nygård, A. M. Horn. Design Guidelines for Riser Collision Offshore Technology Conference [16] Recommended Practice DNV-RP-F206. Riser integrity management. April [17] 33 U.S.C (2005) 19

24 Appendix 1 Risk table Main component Sub component Failure mechanism Initial cause Damage to riser Riser pipe Pipe deformation Accidental impact Armour layer Reduced fatigue life for riser and decreased corrosion protection. Accidental impact Connector Fatigue Accidental impact Valve Accidental closing/opening Accidental impact Damage to ROV Other parts and drilling equipment (bouy etc.) Part broking Accidental impact ROV Broken parts Accidental impact ROV Broken parts Accidental impact ROV Cut wire Accidental impact Possible system failures Source Mitigations Buckling [16] Protection layer, Robot collision avoidance by software and sensors, Regulations (speed and distance limits) Operation shut down for maintenance [16] Robot collision avoidance by software and sensors, Regulations (speed and distance limits) Fracture [16] Robot collision avoidance by software and sensors, Regulations (speed and distance limits) Depends on valve Deepwater Horizon case study Robot collision avoidance by software and sensors, Regulations (speed and distance limits) Depends on the part [16] Robot collision avoidance by software and sensors, Regulations (speed and distance limits) Broken part N/A Robot collision avoidance by software and sensors, Regulations (speed and distance limits), awarness of other ROVs Sinking of robot N/A Robot collision avoidance by software and sensors, Regulations (speed and distance limits), awarness of other ROVs Loss of control N/A Robot collision avoidance by software and sensors, Regulations (speed and distance limits), awarness of other ROVs 20