R & D Study Items

Next Section

Pilot Lifting Operation - Detailed Description Title Pilot Lifting Operation Task 6 Objectives 1. Verify and define removal systems and technology currently available. 2. Perform system test to confirm operability. 3. Implement an offshore test of equipment to determine the operating parameters, feasibility and cost of (OBM) cuttings retrieval. 4. Understand the short and longer term environmental impacts of pile cuttings disturbance. Method Using North West Hutton as a suitable location for the pilot programme the following will be conducted (NW Hutton has been selected due to its availability and the expected timing of full decommissioning): Engage contractor market to determine availability and costs of cuttings removal systems Develop equipment and conduct an onshore "wet" trial of up to four systems and select the two most efficient (and effective) for trial offshore. Implement an offshore trial of a maximum of two systems at NW Hutton to test recovery efficiency of cuttings in and around jacket footings and debris. Obtain all necessary data and samples; this data would include operational data (volume and flow rates, density, etc.) and carrying out full characterisation of lifted material to support Task 7. 2x24 hour recovery duration trials are being targeted which will remove up to a maximum of 900m3 (plus recovered seawater) of cuttings (Approx. 3.6% of the total). Dispose of the material generated in an environmentally responsible manner. (Base case is to re-inject the cuttings and all associated fluid). Implement a thorough environmental monitoring programme to assess the impacts of disturbance Conduct a thorough evaluation of all results for application to full-scale removal. Timescale 9 months Links Prior BP study on hardware potential (Note BP considered the ability to safely execute such an offshore trial in summer 2000 as 'go'/ 'no go' criteria for being included on the bid list. Phase I knowledge, info from Tasks 1 and 5b (geophysical data) and comprehensive reporting requirements on: Details of the current availability and effectiveness of cuttings lifting equipment Operating parameters obtained during the onshore "wet" trial Information on equipment performance offshore and comparison Cuttings pile behaviour under removal conditions Assessment of the environmental impact of disturbance (useable in any comparative assessments) Details of the disposal operation Data for correlating plume (component) dispersion modelling (Task 4) Accurate assessment of the technical and financial implications of complete recovery Removal at the edge of the pile, to ascertain 'when to stop' and how quickly the seabed recovers Other issues Interface between JIP and BP as operator, particularly wrt gateways for equipment selection and decisions to award, selection for offshore trial and readiness to go offshore If required, provide slurry/water samples for onshore treatment (Task 7) Strong interfaces with Task 7 Acceptability of data format for modelling (Task 4) SRG input to monitoring programme Other types and sizes of piles Site restoration (possibly for scope of Tasks 2 or 3) Aberdeen Marine Laboratory tests on single well site (May/June) Checklist of questions to be answered 1. What is the typical rate at which cuttings can be removed from the seabed? 2. What is the range of composition of the slurry as it arrives at the surface? 3. What determines the ratio of solids to water and how can it be minimised? 4. What is the degree of secondary pollution (i.e. water column impact and area/ thickness of cuttings re-settlement) due to re-suspension caused by the dredge-head and the ROV/ crawler? What is the environmental impact of secondary pollution? 5. How much would removal to surface cost? 6. What is the energy consumption for removal? 7. What is the condition of the seabed under a cuttings pile? 8. How do you know when removing seabed rather than cuttings i.e. can you see at dredge head or do you need to sample slurry at surface? 9. Can the rov/ crawler operate/ be controlled reliably within the jacket footprint? 10. What are typical downtimes for weather and system reliability (i.e. debris blockages etc.)? 11. What is the best way to clear new debris as it is uncovered by pile removal? 12. Is it possible to remove a large 'conical' pile without major slumping, if so how?