(32) marine technology April

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1 As part of a 2012 Gulf of Mexico deep water project, an Echoscope 3D sonar imager documented the depth of a 20 pipeline in a trench, below mud line, during a post-dredging operation. (32) marine technology April 2014

2 Characterize and Visualize Leveraging data and technology in deep water development BY MARTIN HARTLAND April 2014 marine technology (33)

3 Characterize and Visualize Characterizing and visualizing critical aspects of deep water projects can enable naval architects and marine engineers to reduce risk as development work gets underway. Oil and gas development projects typically will follow a phased project delivery process similar to that shown in Figure 1, which depicts activities undertaken during the life of the project. Each of the seven phases will have stratigraphic characterization and visualization requirements, as shown directly below each indicated phase. Our purpose here is to provide more detailed information on best practice approaches that are being taken. We want to show how this information is used by operators of deep water fields to improve overall profitability of projects and to help satisfy stakeholders by improving the likelihood of getting it right the first time. DEFINITIONS 3DX 4D AUV AUV3Dm BML DGPS DVL EM GIS HIPAP Three-dimensional explorations seismic data Four-dimensional seismic data--time lapse Autonomous underwater vehicle AUV acquired 3D seismic on a micro scale Below mud line Differential global positioning system Doppler velocity log Electro magnetic data Geographic information system High-precision acoustic positioning Building the ground model In the early days of the offshore oil business, a site investigation invariably meant a soil boring investigation. Because geological conditions on the foundation zone are typically relatively simple on the continental shelf (although there are important exceptions), this soil boring only approach was generally adequate and held sway for several decades. Only when the industry moved into increasingly deeper water (greater than 200 m) did the shallow geological conditions become a common concern, and with it, the need became apparent for a more robust site investigation. The principle components of a modern deep water site investigation include geophysical survey and geotechncial data acquisition HR2D ROV SBP USBL High-resolution two-dimensional seismic data Remotely-operated vehicle Sub bottom profiler Ultra-short base line programs, as well as the associated integrated data analysis. The site investigation is done in phases, with knowledge of the site conditions being increasingly refined as a result of each phase. Site characterization includes defining: Water depth and seafloor topography Geotechncial properties of materials (soil, rock, and gas hydrates) and 3D relationships among soil strata FIGURE 1 1. IDENTIFY OPPORTUNITY 2. FEASIBILITY STUDY 3. CONCEPT SELECTION 4. PROJECT SPECIFICATIONS 5. CONSTRUCTION 6. RAMP-UP TO FULL CAPACITY 7. DECOMM AND REINSTATEMENT Basin studies Geochemical sampling and testing Remote sensing seepage 3DX, EM, and gravity data acquisition Data processing and interpretation Environmental impact assessments Reservoir modeling and economics Field development planning Regional geohazard screening Metocean data Geophysical and geotechnical reconnaissance survey Reservoir modeling and economics Field development planning Geophysical survey Geotechnical site investigation Environmental baseline Geohazard risk analysis Pipeline route optimization Geophysical survey Geotechnical site investigation Geohazard risk analysis Foundation engineering Metocean Drilling and well services support Construction and installation support Pipeline route surveys ROV intervention and inspection Positioning Metocean Geophysical survey Geohazard risk analysis Drilling and well services support Construction and installation support Pipeline route survey ROV intervention and inspection Positioning/ metocean Drilling and well services Decomm construction support ROV intervention and inspection Pipeline route surveys Environmental monitoring Positioning/ metocean (34) marine technology April 2014

4 Geological conditions, including structure, stratigraphy, past events, shallow over pressures, and identifiable features Active geological processes such as faulting, seafloor instability and mass transport, turbid flow, and fluid venting Rates, frequencies, recurrence intervals, and the magnitude of geological processes as a basis for quantitative risk assessments. Results from site characterization typically are delivered in both digital and paper format; however, GIS is becoming increasingly common. In their 2008 technical paper, Modern Deep Water Site Investigation: Getting it Right the First Time, authors Campbell, Humphrey, and Little wrote that the idealized site investigation would follow a sequence as follows. Phase 1: Regional geohazards screening, typically using 3DX data and done before exploration drilling Phase 2: Pre-drilling, geohazards assessment of prospect area Phase 3: Detailed well site specific assessment develop a top hole prognosis. Phase 4: Preliminary engineering assessment using 3DX after the discovery is made Phase 5: High-resolution geophysical survey program planning Phase 6: High-resolution geophysical survey program AUV, HR2D, and other high-resolution techniques Phase 7: Geophysical survey data processing and preparation Phase 8: Preliminary site characterization interpretation and mapping Phase 9: Geotechncial program planning develop an optimal sampling strategy Phase 10: Geotechnical program Phase 11: Sample packaging and shipping to an onshore lab (climate controlled) Phase 12: Geological and geotechncial lab testing Phase 13: Seismic inversion and development of final geotechnical criteria Phase 14: Geohazard assessment, special engineering analyses, and risk assessment Phase 15: Finalized integrated site characterization model and integrated report. Management of all available data is captured with an integrated GIS database. This provides a platform on which a ground model can be built, in addition to capturing all the other relevant geographical data for the development, and then making it accessible via a graphical user interface. In the technical 2011 paper, Use of Geographic Information Systems to Manage Data in Offshore Wind Developments, author Rushton explains that the data can be accessed, queried, interrogated, monitored, and exported for further analysis. The layer-based structure of a GIS interface The site investigation is done in phases, with knowledge of the site conditions being increasingly refined as a result of each phase. enables data sets of multiple disciplines to be interrogated and analyzed together, which is typically of greater value to the engineering team than the sum of the input data sets. The project-specific GIS database is a dynamic tool that evolves as a project develops, and it can support an offshore development throughout the life of a field. It is of primary importance with all geographical information to ensure correct geodetic referencing is applied and to ensure that all data are captured and displayed in common coordinate system. Although a GIS database is a very powerful tool, positioning and data manipulation should be exercised with great caution. Once within the GIS database, integration and analysis of site-specific information is facilitated by large toolsets and intuitive interfaces. Characterization and visualization in 2D and 3D enables users to fully benefit from their data and ground modeling results in a site understanding that is far greater than would be gained from assessment of each data set in isolation. In their 2011 technical paper, Reducing Geo-Risks for Offshore Developments, authors Power, Clare, Rushton, and Rattley wrote that the ground model itself will go through an evolutionary process: from desktop study, to a geological model, to a geotechnical model, to an engineering model. Offshore Angola Natural hazards are being encountered in deep water offshore Angola and in other parts of West Africa. The desired ground model approach is needed to avoid, manage, or mitigate the associated risks to offshore hydrocarbon developments. Among the multiple natural hazards experienced in this region are pockmarks, which are conical seabed depressions formed by liquid expulsion. These may be hundreds of meters in diameter and tens of meters deep, and they represent multiple hazards including the expulsion of corrosive fluids and slope instability. Failure to sufficiently understand these hazards can have a profound impact on the field layout and engineering design, resulting in significant extra cost. The fracture of pipelines or well casings also can have a devastating environmental consequence if they involve significant oil spillage. West Nile Delta The deep water off Egypt s West Nile Delta represents a new hydrocarbon province, incorporating significant natural April 2014 marine technology (35)

5 Characterize and Visualize EVOLUTION OF THE GROUND MODEL Geological model Geotechnical model Engineering model hazards that require a coordinated and systematic geo-risk management approach. In the 2007 technical paper, Integrated Multidisciplinary Seismic Geomorphology Assessment of West Nile Delta Geohazards, authors Moore, Usher, and Evens describe in detail the approach BP has taken to address the challenges posed by the following natural hazards: Seabed slope failures of all scales, from a few hundred cubic meters to many cubic kilometers Mud volcanos Pockmarks and fluid expulsion features Deep channels and scour features on the seabed Variable soil conditions, including biogenic hard grounds within soft clay strata Deep-seated faults and their surface expression Seismic activity. Many of these hazards can be clearly defined by the use of an autonomous underwater vehicle that has the ability to acquire multi-beam bathymetry, side scan sonar, and sub-bottom profiler data. Figure 2 depicts typical mass movement processes that represent natural hazards, and which are based on actual experiences on deep water projects. The terrain system can be divided into four systems moving from shallower water to deep water. Each will have their own mass movement processes with potential to affect pipeline/flowline(s), as follows. Slope system 1: Shallower areas with regional and local-scale landslides, unconfined debris flow, lateral spread, laminar flow, and turbidity flow with parallel impact. Slope system 2: Local-scale landslide, uncontrolled debris flow, and high-density turbidity flow with perpendicular impact. Slope system 3: Local-scale landslide confined/bottleneck debris flow, and hyperpycnal flow with parallel impact. Abyssal plan system: Low-density turbidity flow and hyperpycnal flow with parallel perpendicular and oblique impact. Autonomous underwater vehicles An AUV is essentially a deep water data acquisition robot designed to operate without an umbilical or tether. They are programmed with a mission before a dive and launched via a surface vessel equipped with a suitable handling system. Navigation typically is accomplished using a combination of a USBL system with 30-second DGPS-HIPAP updates from the surface vessel; an inertial navigation system onboard the vehicle; a DVL system; and integration of data from these systems using a Kalman filter. AUVs are now considered essential tools for deep water projects for the following reasons. They ensure the rapid acquisition of multiple data types They operate at depths that might be prohibitive using traditional methods They are very stable, low-noise platforms, maintaining a consistent altitude above the seafloor They reduce distortion caused by fish motion They offer high-resolution side scan images, increasing the range of object detection They offer accurate positioning with onboard inertial navigation system They are highly maneuverable, giving optimum survey performance (36) marine technology April 2014

6 They focus on data acquisition rather than line turns or lead-in lengths. AUVs are available in various sizes and with different capabilities. Smaller units are easier to ship around the world by air and to use on vessels of opportunity. The high-end unit pictured here, a HUGIN 3000, is designed and manufactured by Kongsberg and has a 55-hour operation time per dive. All AUVs are normally designed to operate in depths down to 3000 m and can acquire multi-beam bathymetry, side scan sonar, and subbottom profiler data. AUV3Dm AUV3Dm is a method used to acquire deep water sub-bottom profiler data using an AUV survey vehicle, along with the processed micro 3D seismic data volume. AUV3Dm data precisely defines foundation zone conditions without gaps. The methodology is used where a very detailed 3D characterization of shallow soil strata and geologic features is required to help optimize deep water production structure siting and foundation design, including anchor pile sites, so that faults can be avoided during installation. Vertical resolution of approximately 20 cm of the data is achieved, which facilitates detailed correlation with sediment cores and cone penetrometer data, thus enabling calibration of the micro 3D volume. It is recommended to acquire AUV3Dm whenever shallow foundations are required in areas of complex stratigraphy or local geologic hazards. In their 2013 technical paper, AUV3Dm: Detailed Characterization of Shallow Soil Strata and Geo Hazards Using AUV Sub bottom Profiler 3D Micro Volumes, authors Campbell, Smith, and Pastor wrote that they are aware of at least 17 deep water AUV3Dm surveys that have been successfully carried out. These have been used to help characterize or avoid fault planes in foundation zones; to characterize fluid vents (pock marks and mud volcanoes) and gassy zones; to detect boulders; and to produce AUV3Dm time lapse (4D) surveys spaced one year apart to detect changes at a fluid vent site. AUV3Dm surveys may use a range of line spacing from 2 to 4 m, and the AUV would typically be operated at an altitude of approximately 20 m above the seafloor, at a speed of approximately 4 knots. The SBP system that is often used would be an EdgeTech Chirp profiler using a 2 to 12 khz frequency band with a sampling rate of 46 microseconds. Details matter when acquiring AUV3Dm data if one is to obtain a good quality data set. Both operational and processing details that affect data position in 3D space are critical to the 3D volume integrity, and they need careful attention. The principal factors include: Navigation of the AUV to maintain straight track lines and uniform line spacing Accurate position of the AUV/SBP transducer Survey line plan (shooting sequence and direction) The project-specific GIS database is a dynamic tool that evolves as a project develops, and it can support an offshore development throughout the life of a field. Tidal (depth) and atmospheric pressure changes to correct for variations in AUV height above seabed Migration of data during 3D seismic processing (the optimum migration algorithm is still being developed). Real-time 3D imaging Offshore vessel time is expensive, as are people and equipment. Having the ability to have accurate and distinct vision and measurement in the subsea environment is very important to an operator; it can reduce time spent on a project and save significant costs. Normal video camera and lighting are not much use when visibility is poor, and this can lead to dangerous situations. Poor visibility can occur when carrying out an activity that disturbs the seabed in some way, for example, and depending on the nature of the activity, it can be critical to be able to see what is happening real time. The Coda Octopus Echoscope is an example of a unit that provides 3D real-time high-resolution sonar images; it uses single (375 khz) or dual frequency 375 khz (and 610 khz) modes. Its beam array provides 16,384 simultaneous beams, which is a data density more than 100 times that of a traditional FIGURE 2: TYPICAL MASS MOVEMENT PROCESSES April 2014 marine technology (37)

7 Characterize and Visualize multi-beam echo sounder. The system itself is the size of a briefcase and is quickly deployed on an ROV or an AUV. The unit is capable of providing XYZ coordinate and intensity data for every ping that is returned, and this enables real-time measurements and position identifications using a real-world coordinate system. The system can be combined with other sensors that may include motion reference units, sound velocity sensors, sound velocity profilers, and positioning input, heading, and depth sensors. The quality of update rates for these sensors will increase the quality of resulting image data, and accurate position and altitude data is essential for mapping applications. Gulf of Mexico In June 2011, a project objective involved clearing the earth under a mud mat for decommissioning. The plan was to clear the earth around each platform leg to enable cutting devices to remove the The unit is capable of providing XYZ coordinate and intensity data for every ping that is returned. platform below the mud mat. Monitoring with a conventional ROV video was not an option due to the suspended sediment. One ROV worked on the cutting, while a second ROV was equipped with the Echoscope to visualize what was happening for the cutting operation and to measure that the required clearance was achieved. Verification tests carried out later confirmed that the results were precise. AUVs can operate at extreme depths, and can rapidly collect multiple types of data. Shipwrecks Seafloor landslides Fault scarps Pipelines Seafloor vents Salt domes (38) marine technology April 2014

8 In June 2012, the Echoscope was deployed to support the installation of a Wye sled that would be installed close to an active pipeline. Tons of seafloor material and concrete were removed from underneath the pipeline that the sled was supposed to tie into and around the pile on which it was to be installed. Dredging conditions stirred up the ocean floor, rendering visual navigation difficult. The echoscope operators were able to use the 3D models and color by depth to settings to confirm that they had achieved the required dredging depth around the pile. As the Wye sled was deployed, it was monitored as it reached depth to ensure rigging was correct. Measurements were taken of the site to verify proper installation for future pipeline tie-ins. Project management The overall management of stratigraphic characterization and subsea visualization on a deep water development project can easily involve a large number of specialist service providers. It therefore is important to manage this aspect of the project and the associated data in a way that ensures it is truly integrated and that the required information is easily accessible to the project engineers when needed. Other critical factors include accurate interpretation; an understanding of how improved quality can be achieved; and recognizing when the data quality or methodology may not be adequate. Based on recent successful experience, the recommended approach is for a deep water project team to consider characterization and visualization services as a package. In addition, a trusted multi-disciplined service provider should be engaged. This provider should be able to support the development project by the overall management of these services, using a specialist project management resource who will become embedded within the deep water project team as a trusted partner. This specialist typically will have project director status within the service company and will be closely networked with the various characterization and visualization service providers. The specialist will use the full experience of this network to find the best possible solutions for the project, naturally taking into account the constraints of cost, quality, and time and the convergence of the main work scope activities on the project. Aiming to have a single point of contact for this wide range of services, (especially when operating in frontier areas with challenging logistics) can improve the effectiveness of the project team. It also will lead to cost savings, improved coordination, and a higher level of project quality assurance and control. MT Martin Hartland is divisional strategy manager with Fugro (USA) Inc. The HUGIN 3000, an AUV designed and manufactured by Kongsberg, has a 55-hour operation time per dive. Deeper Dive The following technical papers and publications can provide additional information on the subjects covered in this article. Deepwater Angola: Geohazard Mitigation, by A.J. Hill, M. Fiske, P.R. Fish, and S. Thomas. Published 2011 as part of 2nd International Symposium on Frontiers in Offshore Geotechnics, Perth, Australia. Modern Deep water Site Investigation: Getting it Right the First Time, by Campbell, Humphrey, and Little. Published 2008 by the Offshore Technology Conference. Use of Geographic Information Systems to Manage Data in Offshore Wind Development, by Rushton. Published as a poster during the EWEA Offshore 2011 conference in the Netherlands. Reducing Geo-Risks for Offshore Developments, by Power, Clare, Rushton, and Rattley. Published 2011 by Bundesanstalt fur Wasserbau. Integrated multidisciplinary assessment and mitigation of West Nile Delta Geohazards, by Moore, Usher, and Evans, published 2007 as part of the 6th International Conference, Offshore Site Investigation and Geotechnics. AUV3Dm: Detailed Characterization of Shallow Soil Strata and Geohazards Using AUV Subbottom Profiler 3-D Micro Volumes, by Campbell, Smith, and Pastor. Published 2013 by the Offshore Technology Conference. Recent Advances and trends in subsea technologies and seafloor properties characterization, by various authors. Published in the October 2013 issue of Leading Edge magazine. April 2014 marine technology (39)