SupOps, Haugesund, Norway AUV icp Results from an integrated Cathodic Protection Survey of a North Sea Pipeline

Transcription

1 Cathodic Protection Survey SupOps, Haugesund, Norway AUV icp Results from an integrated Cathodic Protection Survey of a North Sea Pipeline Brian Claus, Ph.D., Matthew Kowalczyk, Eng. - OFG Craig Donald BSc. Dip Eng ISES Technical Services

2 AUV Survey Operations OFG Company Overview AUV Sensor Development and Supply OFG owned and operated Chercheur Hugin Equipped with HiSAS, MBES, SBP, HiRes Camera, ADCP, water geochemistry, Selfcompensating magnetometer OFG/ISES integrated Cathodic Protection (icp) system Operational Support for Third party AUV s OFG Self-Compensating Magnetometer (SCM). Installed in > 20 AUVs OFG/ISES integrated Cathodic Protection (icp) system Development and Operation of Other Geophysical Systems Full Service Provider Vulcan CSEM towed array AUV borne CSEM ROV borne EM and magnetometer systems (OFG EM MkIII) 3D Vertical Cable Seismic (VCS) Towed Array Marine Induced Polarisation System (MIPS) Project Management Survey and Mission planning Data Analysis and Interpretation

3 Shell Ocean Discovery XPRIZE Some Recent Interesting Projects

4 AUV icp Test Results from a Cathodic Protection Survey of a North Sea Pipeline This presentation includes: 1. Overall concept description of the OFG AUV icp 2. Results of in-field system trials of the OFG AUV icp system over an operational pipeline in the North Sea. In particular: Sensitivity Accuracy/Repeatability Survey Positioning Survey Speed Multiple Payload Capability 3. Scenarios for AUV icp Survey within a Pipeline Integrity Management and Inspection Strategy OFG AUV icp tests results over North Sea pipeline

5 The AUV-iCP Concept: integrated Cathodic Protection System Uses AUV pipe tracking and E-Field system concurrently to accurately locate field gradient measurements relative to pipe Current flow through the pipe from Cathodic Protection is then be mapped Determines: - Level of cathodic protection - Activity of anodes estimate of remaining anode life - Leakage currents in pipe indictating for pipe damage/non-uniformity EIVA Simulated Data

6 The AUV-iCP Concept Precision Navigation Real-time accuracy of ~2m with HiPAP USBL system Pipe Tracking Real-time tracking of pipe using HiSAS/MBES provides ~cm level positioning relative to pipe Field Gradients Gradient measurements in 3-axis X/Y/Z dx/dy/dz Ex/Ey/Ez Cathodic Current Estimation By combining these three systems the cathodic current flowing through the pipe can be estimated i dz i dy Ez Ex Ey

7 AUV-iCP Deployment OFG s AUV Chercheur, a 3000m HUGIN, - Can perform pipe inspection and tracking using MBES, HiSAS, magnetometer, and photos Chercheur now also equipped with the OFG AUV icp System MBES Still Photos

8 AUV icp Trials over a North Sea Pipeline Field trial of AUV icp flights conducted in Q on an operational pipeline installed in the North Sea in collaboration with DOF Subsea: Measured Field Gradient during multiple survey runs in opposite directions. ROV CP-DAS survey also performed as a reference survey Flown at altitude of 5m above pipeline icp data was collected with all usual AUV sensor payloads running, to confirm no interference AUV speed of 3.3 knots (~6 km/hr)* *Note that vessel USBL installation limited speed during the trials. Nominal AUV survey speed is approximately 7km/hr depending on conditions. DOF M/V Geocat attending to AUV icp trials

9 AUV icp Sensitivity Test Results Variations of approximately 0.01µV/cm were reliably and repeatedly detected. The results confirmed during multiple test runs in both directions along pipeline The test results indicate that the system is approaching a detection limit TEN times that of any other available field gradient logging system (as per published results). UNAMBIGUOUS AND REPEATABLE

10 AUV icp Accuracy/Repeatability Measured FG data showing 2 survey runs in opposite directions Total Standard deviation of difference between measurements in opposite directions: Et = 0.021µV/cm Ex = 0.012µV/cm Ey = 0.015µV/cm Ez = 0.027µV/cm - Without correction for position, range, attitude. - Difference is between entire length of pipe that was surveyed in both directions at the same altitude. In Line Cross Vertical

11 AUV icp Accuracy/Repeatability Total In Line

12 AUV icp Accuracy/Repeatability Comparison with other systems: OFG AUV icp Accuracy ~ 0.01 µv/cm Standard twin cell CP/FG system +- 1 µv/cm Rotating sensor µv/cm (as per publically available information) The grey bar illustrates 0.1µV/cm sensitivity threshold of rotating sensor system (as published). Indications would only be observed above sensitivity threshold of rotating sensor, however they were easily detected using OFG AUV icp in x,y & z planes sensitivity threshold

13 AUV Multiple Payload Capability The icp results are not influenced by other on-board sensors e.g. HIPAP, HISAS, magnetic, acoustic modem, photo mapping, etc. Allows for concurrent data acquisition from multiple AUV mounted sensors during pipeline surveys. The results of the trials show very good icp data quality at various ranges from the pipeline. The distance from the pipeline that the AUV inspection is flown will not be determined by the icp, but rather by the limitations of the other inspection sensors, eg. Camera, Multibeam, Laser Scanner.

14 OFG AUV icp tests results over North Sea pipeline This image: - - MBES bathymetry - - Pipeline model from derived MBES from datambes data - - Camera imagery draped over over pipeline model

15 OFG AUV icp tests results over North Sea pipeline. This image: - MBES bathymetry - Ex (inline E-field, red line) - Ez (vertical E-field, green line) - AUV track (yellow line) - Pipeline model from MBES data

16 OFG AUV icp tests results over North Sea pipeline This image: - MBES bathymetry - Pipeline model derived from MBES data - Camera imagery draped over pipeline model

17 OFG AUV icp tests results over North Sea OFG AUV icp tests results over North Sea pipeline pipeline This image: This image - - MBES bathymetry - MBES bathymetry - - Pipeline Et (E-field model total from magnitude, MBES data multicoloured imagery line) draped over pipeline - Pipeline model derived from MBES - Camera data - model AUV track (yellow line) - Camera imagery draped over pipeline - Pipeline model from MBES data model

18 Scenarios for AUV icp Survey within a Pipeline Integrity Management and Inspection Strategy

19 Pipeline Integrity Management Strategy The AUV icp system opens the possibility of being able to conduct fast, accurate CP surveys with minimal or no requirement for timeconsuming potential contacts icp means integrated Cathodic Protection; it s not only about cathodic potential. For example; Integrity Management of Submarine Pipeline Systems DnV-RP-F116 Feb 2015, specifies Regular inspection on condition of CP system. Strategies and plans for pipeline integrity improvement related to cathodic protection

20 OFG AUV icp in a Pipeline Integrity Management Strategy Cathodic Potential is measured in mv and is only one of the measurements used to assess how effectively a cathodic protection system is operating. AUV icp can give you more information for your Cathodic Protection program. Measuring the electrical field (field gradient µv/cm ) around a pipeline with the sensitivity of the AUV icp system also allows (in addition to the items in previous slide Excerpt from DNV-RP-F116 Feb 2015 ): - Current density along the pipeline - Disconnected or passivated anodes. - Anode current output - Identification of anomalies - Anode activity - Identification of location, direction and magnitude of current flow. - Estimation of remaining life of the anodes - Current drain (e.g. to platform, well head) - Identification of areas of active coating damage - Areas exhibiting higher than expected current flow.

21 Excellent -> Acceptable -> Poor / Not possible Pipeline Integrity Management Strategy Excerpt from DNV-RP-F116 Feb 2015 AUV icp Survey Visual inspection of the external coating condition Visual inspection of the condition and consumption of the galvanic anodes Potential measurements of galvanic anodes Steel-to-electrolyte potential measurements along the pipeline Potential measurements at any coating damage exposing bare pipe metal Electric field gradient measurements and current densities in the vicinity of the pipe Anode current output. Measurement of current at anodes Detection of areas of current flow along the length of the pipeline, including buried and under rock protected Detection of coating damage under concrete coating and also of areas exposing bare pipe

22 AUV icp Electrical Currents Field Gradients Electrical Currents Negative are sources: Anodes Positive are sinks: Pipe damage Current drain Distance along pipeline

23 ROV CP Stab vs OFG AUV icp Measurements mv wrt Ag/AgCl ROV CP Stab - Voltage drops and depolarization begins when the anode mass is nearly consumed.possibly too late to intervene in time A Protected Design Life Stable Conditions (e.g. 20 years) Lifecycle of BStructure Polarisation Depolarisation C Under Protected D OFG AUV icp Calculate anode currents compute mass and energy remaining and predict anode end-oflife much earlier! Protected Design Life Stable Conditions (e.g. 20 years) Polarisation Depolarisation Under Protected Potential will start to fall off once majority of anode is consumed Lifecycle of Structure

24 OFG AUV icp Usage Scenarios in a Pipeline Integrity Management Strategy Scenario One Scenario Two Scenario Three - Post lay baseline/tie-in CP survey - Maintenance CP survey - Intervention CP survey

25 Scenario One: Post lay baseline/tie-in CP survey Rapidly undertaken to confirm the integrity of the pipeline installation. From a cathodic protection standpoint a number of factors require confirmation. General Potential level Anode connection to pipeline Anode damage Stinger or laying damage to pipeline Unusual or unexpected anode activity Areas of current drain. The OFG AUV icp system can be used to undertake high speed visual and field gradient measurements. Other non-cp inspection data can be acquired by the AUV concurrently for out of straightness, free-span, visually identifiable damage, buckling, etc.

26 Scenario Two: Maintenance CP survey Pipelines are typically required to be surveyed either on a prescriptive basis or at a frequency derived from a risk based inspection (RBI) plan, as part of an overall integrity management strategy. Frequency of inspections generally range from annually to every 5 years, depending on the strategy employed. Undertaken to identify any significant changes in the condition of the CP system has occurred since the previous survey. To determine if the pipeline cathodic protection system is performing as designed in terms of protection levels and anode performance and anode life. OFG AUV icp tests results over North Sea pipeline

27 Scenario Two: Maintenance CP survey Anomaly Based Inspection Example: OFG AUV icp used to calculate current output of each anode over time M a = I cmt F 8760 =273kg uε u = 0.8 ε = 2000Ah/kg t f = 50yrs I cm = 1A Identify Increase in activity Activity above design! Premature Consumption! Survey Year Current [A] Mass Budget [kg]

28 Scenario Three: Intervention CP surveys Undertaken if something significant has been identified which could affect the cathodic protection system, for example: Pipeline damage Post anode retrofit survey Additional connections to pipeline e.g. tie-ins new well, risers, manifolds and structures. The icp system can be used to undertake a rapid assessment of the condition of the pipeline after the event has occurred to provide accurate information on the activity of the anodes and identify if there is a correlation between areas of damage and current drain and measure the effects.

29 OFG AUV icp Conclusions Based on Field Trials The passive, non-contact AUV icp system allows fast, accurate CP surveys to be conducted: 1. Real-time pipe tracking and inspection using MBES, HISAS, magnetometer and photos 2. Accurately detect and quantify Field Gradient (FG) along a pipeline route at significantly higher speeds than an ROV survey. 3. Detect & quantify pipeline electrical fields to an unprecedented level (variations of ~0.01µV/cm) from which currents (anodes and also damaged areas) can be calculated 4. Signal accuracy was not reduced by either vertical or horizontal standoff distances between the AUV and the pipeline. 5. Gather multiple data sets from other sensors simultaneously without degrading the received FG signals due to system s operations noise. 6. The system can add significant value in efficiency and cost savings when used as part of an integrated pipeline inspection management strategy. Instead of a contact every km this could may be reduced to a handful of selected key point contacts along the entire pipeline route

30 OFG AUV icp - AUV Chercheur currently mobilised to a vessel in the North Sea and will become available again for pipeline inspection in September Questions?

31 Technical Services Ltd Europe ISES Technical Services Limited 1 st Floor, Block 7, The Altec Centre Minto Drive, Altens Industrial Estate Aberdeen AB12 3LW, Scotland Tel: Fax: Web Site: craig@ises.tech Asia Pacific ISES Technical Services PTE Ltd. No 38 Loyang Drive, Unit Loyang Industrial Estate Singapore Tel Malaysia Inspection Survey & Integrity Services Sdn Bhd CT Subang Square Corporate Tower Jln SS15/4G, Suband Jaya, Selangor, Malaysia Tel: / 9850 / 9750 Fax:

32 Ocean Floor Geophysics Inc. B Bill Fox Way Burnaby, BC Canada V5J 5J3 E: T: