IAGC Guidelines Time Sharing Between Marine Seismic Crews

Transcription

1 IAGC Guidelines Time Sharing Between Marine Seismic Crews July 2014

2 Guidelines for Time Sharing Between Marine Seismic Crews Preface The International Association of Geophysical Contractors aims to provide guidance to the Geophysical industry for how to efficiently and effectively engage in time sharing when marine seismic crews are in close proximity of each other and are faced with potential seismic interference, environmental restrictions, adverse weather, permit restrictions, or other similar obstacles that may impede simultaneous operations. Time sharing between marine seismic crews should be instituted on request no matter how unwarranted it may appear to the operators of the other vessels. Also, time-sharing between marine seismic crews should provide an equitable allocation of production time whether Towed Streamer or Static Receiver (OBC/Nodes). 1

3 Acknowledgements Timeshare Workgroup Membership Bernie Marsh Chairmen Andy Lambert (Alternates Chris Newton & Heather Pratt) Bjorn Henriksen Bradley Heath Eirik Oestensvik Shawn Rice Rick Donoghue (Alternate Richard Price) Jonathan Byers Knut Agersborg Samantha Graycon (Alternate Kevin Deal) Walt Rosenbusch Ex-Officio Member PGS CGG Dolphin Geophysical FairfieldNodal Fugro (CGG) ION Polarcus Seabed Geosolutions TGS WesternGeco IAGC These nonbinding Guidelines are offered by IAGC for discussion and educational purposes only. Any industry participant is free to use these Guidelines in any way it wishes. 2

4 Table of contents 1. Introduction Purpose 1.2. Definitions 1.3. References 2. Scope 4 3. Background 5 4. Definitions 6 5.Basic Principles 7 6. Time Share Guidelines Towed Streamer / Towed Streamer 6.2. Towed Streamer / Static Receiver 7. References Revision History Appendices Appendix A Space Sharing - - Gulf of Mexico Kilometer Buffer Zone 3

5 1. Introduction 1.1 Purpose The density of Marine seismic activity in various regions of the World can increase due to a number of factors including but not limited to, seasonal weather patterns, environmental restrictions, and lease activity. This increase in crew density may necessitate time sharing among marine seismic contractors operating in proximity of one another in order to avoid unwanted seismic interference or to remain compliant with a seismic permit that requires seismic contractors to maintain a prescribed distance between active energy sources. 1.2 Definitions The terms and definitions included in this document are ones commonly used within the seismic industry to describe and discuss time sharing. A concise list of terms and definitions is provided in Section References The references included in this document are listed in Section Scope The scope of this document is to provide IAGC marine seismic contractors and their crews guidance for the implementation of time sharing. The Time Share Task Force was responsible for developing this document. The Task Force was comprised of representatives from major marine seismic contractors that operate globally in areas where oil and gas exploration interest and activity has been or is robust and where the acquisition of new seismic data is in demand. The Task Force was created by the IAGC Board of Directors with the following remit: Investigate and diagnose the instances where simultaneous marine geophysical operations have or are occurring and are likely to occur in the future, where time sharing was used, where it was not used but perhaps should have been, or where time sharing was a problem. Consider all aspects of the timeshare issue e.g. non-exclusive versus proprietary operations; towed streamer versus OBC/Nodes, WAZ, etc; time constraints; regulatory requirements affecting time share; the role of E&P companies; contractual constraints, etc. Identify and evaluate possible remedies and paths forward including updating the current guidelines or developing new IAGC guidelines. 4

6 3. Background The need for timely data for acreage evaluation can result in several seismic vessels concurrently acquiring data in the same general area. Acquisition by one vessel can produce a source of recorded noise (interference) for all other vessels in the vicinity and vice versa. Additionally within some jurisdictions in the world active seismic sources are required to maintain a prescribed (by regulatory permit) distance from other active seismic sources. This is often referred to as space sharing. Whether it is because of recorded noise interference or ensuring compliance with a prescribed distance between active seismic sources, time share is a procedure under which the time available for acquiring or recording data is divided equally (shared) among all the vessels affected. The need for timesharing should be minimized to the greatest extent possible. There are two approaches that IAGC member companies are using which have proven to be somewhat successful: 1) routine meetings with all seismic contractors with planned work for a particular region (North Sea); 2) monthly activity reports providing seismic vessel activity within a particular region (Gulf of Mexico). Seismic contractors operating in other regions of the world are encouraged to adopt either or both of these two approaches to minimize the need for timesharing. In incidences where space sharing is required due to seismic permit requirements, Appendix A Space Sharing - - Gulf of Mexico Kilometer Buffer Zone provides guidance designed to assist in the compliance with any prescribed separation mitigation measure. Although the guidance refers to the US Gulf of Mexico, it is easily transferrable to incidences in other jurisdictions; however in the absence of a regulatory buffer zone distance associated with the acquisition permits, the need for timeshare should be determined only by levels of seismic interference. Unfortunately no matter how much cooperation is achieved, limited acquisition windows still result in several vessels having to acquire data concurrently within the same area. Guidelines are therefore required to ensure an equitable solution is achieved for all vessels involved. The current industry practice is to grant Timeshare on request; no matter how unwarranted it may appear to the Operators of the other vessels affected. This document is intended to provide guidelines to allow an equitable allocation of production time between seismic marine crews whether Towed Streamer or Static Receiver (OBC / Nodes, where a requirement to timeshare has already been established. ANY TOWED STREAMER operations (2D and/or 3D) are characterised by a continuous period of recording, followed by a line change period. The time allocation for each of these can vary significantly depending upon the project specific requirements. For the purposes of this document the categorisation of TOWED STREAMER crew time use can be considered simplistically as follows; 1 Production 2 Line Change 3 Standby (Weather, Obstructions, Marine Mammals, Fishing activity, Timeshare, etc.) 4 Contractor Downtime (technical downtime associated with contractor equipment failures, or non-productive time generally considered to be in the control of the Contractor). 5

7 STATIC RECEIVER acquisition methods are extremely varied due to the flexibility of acquisition geometry available to these techniques, and the choice of technology for each project which could include traditional OBC or autonomous OBN systems, as well as the choice of single of multi-source vessels. A typical STATIC RECEIVER method the operating modes are characterised by a layout out/deployment period for the receivers followed by acquisition of multiple source lines, with short line change times. Depending upon the swath or patch definition each of these periods can be longer or shorter, but in general an effort is made to balance the source and receiver effort such that a continuous and contiguous operation is achieved. The categorisation of time for STATIC RECEIVER crews can be considered as follows; 1 Recording 2 Line Change, and Receiver or Swath Move 3 Standby (Weather, Obstructions, Marine Mammals, Fishing activity, Timeshare, etc.) 4 Contractor Downtime (technical downtime associated with contractor equipment failures, or non-productive time generally considered to be in the control of the Contractor). In the event that more than one seismic crew are in such close proximity that precludes simultaneous recording on both crews, a mechanism of time-sharing is required that is sympathetic to both types of acquisition. In addition to the differing natural cycles of each method, there are further complications in that the STATIC RECEIVER method is typically less sensitive to the effects of adverse weather than TOWED STREAMER. Any method of accounting for time should not attempt to equalise any genuine advantage of one technique over the other. For example if a STATIC RECEIVER crew is capable of operating in sea states in excess of a nearby TOWED STREAMER crew then the extra recording time available to the STATIC RECEIVER crew should not be used in any calculation of time-sharing. Under no circumstances should there be the attempt to equalise based on cost of operations. For example if a 3D or WAZ TOWED STREAMER crew and a 2D TOWED STREAMER crew are within proximity of one another such that time-sharing is required, the relative cost of one operation versus the other should not be considered in any way when calculating time-sharing. The premise to the following guidelines, therefore, is that TIME-SHARE time should be one-for-one so long as both crews are able to shoot. 4. Definitions PRODUCTION time is the time that one crew is recording data online (including time required for Soft Start ). LINE CHANGE is the actual line change time that would have been recorded if timeshare situation did not exist. (This definition is to assist in on-board time keeping and charging & does not affect calculations of PRODUCTION time). STANDBY is time lost due to circumstances beyond the control of the contractor e.g. weather, obstructions, oilfield activity, timeshare standby, etc. 6

8 CONTRACTOR DOWNTIME is time lost due to circumstances within the control of the contractor e.g. technical downtime, crew change, port calls, etc. TIMESHARE TIME is the time that one crew is in operational readiness and waiting to start recording but is unable to do so because the other crew is shooting. (This definition is to assist in on-board time keeping and charging & does not affect calculations of PRODUCTION time). 5. Basic Principles The objective is that Timeshare Time should be equalised between all crews (ie equitable usage of quiet water ) so long as a time-sharing situation exists. 1. Contractual status, (e.g. day rate, km/standby, speculative survey, number of streamers) is not considered in TIMESHARE calculations. 2. Survey size, line length or survey type (e.g. 2D, Exploration 3D, 4D) are not considered in the TIMESHARE calculations, 3. Each operation from the same contractor is entitled to their own PRODUCTION slot 4. Dual/Multi vessel surveys = One PRODUCTION slot 5. Two vessels from same contractor independently acquiring data on same survey = two PRODUCTION slots. 6. Where required, a soft start period is to be included in each PRODUCTION slot 7. Vessels acquiring in a tidal shooting regime or any other specifically required time slot (for example a particular time slot to enable an undershoot pass) will have the priority with respect to scheduling of a PRODUCTION slot. However, in no way will this affect the accounting of PRODUCTION time. 8. There should be no obligation on any vessel to break off lines as a means to equalise production time. 9. A Vessel cannot change its proposed commencement time of a PRODUCTION time slot within 4 hours of the proposed commencement time. The accounting of production time will commence at the proposed Start time and end on the completion of the PRODUCTION Time slot unless another vessel is able to acquire data for that period. A vessel facing possible late or no start of a line due to technical or operational difficulties, should flag this as early as possible to allow another vessel to utilise the available slot. 6. Time Share Guidelines 6.1 Towed Streamer / Towed Streamer Before committing to Timeshare, all parties should consider the following to see if Timeshare can be avoided or minimised: Map location of surveys; Line directions, The relative move out of the interference as the vessels move a long their lines, and: Investigate if relative positioning of the vessels can be used to avoid or minimize Timeshare; particularly in situations where space sharing regulation apply. 7

9 The following guidelines are designed to allow two or more towed streamer crews, interfering crews, to achieve equal PRODUCTION time during periods where these crews could be fully operational in the absence of the other. The steps below should reduce unnecessary Timeshare, whilst eliminating the risk of acquiring data with unacceptable acquisition and or processing artefacts. The testing routine is based on a commonly utilised method and should accommodate differences in target zones between individual surveys. While other routines for seismic interference attenuation may be successful the routine below should be used as a common benchmark. 1. Interference noise should always be monitored in the field and the requirement for time-sharing must be justified by the party requesting time-sharing. a) Record data with seismic interference; notify interfering vessels & request time-share; a 72 hour period should be granted to allow processing tests to be completed. b) As a minimum testing should be carried out on the affected line and include the commonly used and widely recognised attenuation method set out below to determine either a final data processing flow or provide satisfactory evidence that the interference noise can or cannot be removed during onshore processing; Pre-conditioning of shots (removal of random/swell noise) Forward Tau-P transform on shots Sort to common P (slowness) / FFID (shot) ensembles Time and frequency dependent anomalous noise attenuation - using windowed anomalous amplitude detection followed by iterative F-X prediction to reconstruct coherent signal Subtraction of filtered data from Tau-P input (isolate noise) Sort back to Tau-P domain FFID gathers Inverse Tau-P transform to give TX model of SI-noise Adaptive subtraction of SI-noise model from TX input data c) Compare with noise free line and asses efficiency of attenuation. d) If steps b and c above show unacceptable levels of contamination then requirement to timeshare should be confirmed to other vessels. To demonstrate the necessity of time share and where possible, the Operator should be prepared to share these results with the Operators of the other vessels affected. Numerous case examples of this attenuation technique were presented at the FORCE Seminar, How to Reduce Time Sharing, (Stavanger - September 2012), and can be found on the FORCE web-site: Other references are included in Section The negotiated time-sharing arrangement should be reviewed at least once every 24 hours, to ensure parity is maintained in terms of PRODUCTION time being divided equally between the concerned crews. Note that equitable allocation of production time need not be based on discrete 24-hour periods. Period will be determined by factors such as weather forecast, tidal 8

10 slots and line lengths for all parties. 2. Should any crew cease production during a time-sharing situation and a single crew is left operating, then none of the acquisition time for the remaining crew will be logged with respect to time-sharing. In the event that more than one crew continue to operate then the timeshare arrangement will be revised for the remaining number of vessels (once all remaining parties have received their prior allocated time slot). No production time accrued during such a period will be logged with respect to the original timeshare arrangement. 3. A single point of contact should be agreed to administer timeshare arrangement. The first vessel in the area would typically assume this role. 9

11 6.2 Towed Streamer / Static Receiver 1. As with Towed Streamer / Towed Streamer Time Share situations, Towed Streamer / Static Receiver Timeshare must be justified by the party requesting time-sharing using the common benchmark testing outlined in paragraph 1 of the Towed Streamer/Towed Streamer timeshare Guidelines. 2. Once a time-sharing situation is agreed to exist, a division of time, based on the prevailing TOWED STREAMER crew line duration, or multiples thereof, should be agreed between the two crews. 3. The negotiated time-sharing arrangement should be reviewed at least once every 24 hours, to ensure parity is maintained in terms of TIMESHARE time being divided equally between the two crews. 4. The actual TIMESHARE time measured by both crews should be equal. TIMESHARING measurement should exclude any line change, STATIC RECEIVER or swath moving time, technical downtime or bad weather periods, and any production generated by either crew during such periods. 5. To illustrate, if a TOWED STREAMER crew requires 4 hours to shoot a line and 2 hours to line change, the cumulative time-sharing and production time for each crew would be as follows: Towed Streamer Crew Static Receiver Crew Production Line Time-Share Production+ Swath Time-Share Change LC Change 4 hours 4 hours 2 hours 2 hours 4 hours 4 hours 4 hours 4 hours 2 hours 2 hours 4 hours 4 hours 4 hours 4 hours 2 hours 2 hours 4 hours 4 hours 4 hours 6hours 2 hours 16 hours 8 hours 12 hours 18 hours 6 hours 12 hours 24 hours 12 hours 24 hours 12 hours 4. In circumstances where there is more than a two-way time-share the above principles should still apply, as illustrated by a 3 way time-share in the table below: Towed Streamer Crew 1 Towed Streamer Crew 2 Static Receiver Crew Line Time- Producti Time- Productio Change Share on Share n+ LC Producti on Line Chang e 10 Swath Chang e Time- Share

12 hours Should any crew go down for weather during a time-sharing situation and a single crew is left operating, then none of the acquisition time for that crew will be logged with respect to timesharing. Should more than one crew continue to operate then the above guidelines will apply from scratch, in each instance, with no logged time taken into account when full time-sharing resumes. 7. References 1. Gulunay, N. [2008] Two different algorithms for seismic interference noise attenuation. The Leading Edge, 27, Yu, M.C. [2011] Seismic interference noise elimination A multidomain 3D filtering approach. 81 st Annual International Meeting, SEG Technical Program Expanded Abstracts, Manning, T. [2006] Reduction of acquisition time-sharing in the north sea by seismicinterference attenuation. First Break, Vol 24, No 12, December Laurain, R. [2013] Improving Acquisition Efficiency by Managing Seismic Interference - Snorre 4D Survey th EAGE Conference & Exhibition incorporating SPE EUROPEC 2013 Extended Abstracts Dhelie, P.E. [2013] Increasing the Efficiency of Acquisition in a Busy North Sea Season - Dealing with Seismic Interference. 75th EAGE Conference & Exhibition incorporating SPE EUROPEC 2013 Extended Abstracts 11

13 8. Revision History Rev No Effective Date Description Prepared by (name) 1 03/04/2002 First Draft M Osborn, WesternGeco 2 19/06/2002 Second draft after review meeting 19/06/2002 M Osborn, WesternGeco 3 25/11/2002 PGS amendments to Version 2 M Osborn, WesternGeco 4 2/5/2003 SCC modification & approval on M Osborn, 30/01/03 accepted by EAME WesternGeco Executive. Guidelines to be issued for immediate use in EAME Region in 2003 season. 5 8/12/2005 Consolidation of towed and S. Graycon OBC time sharing guidelines WesternGeco 6 2/10/2013 Addition of Common Benchmark Data Processing Routine, Space Sharing guidelines and general update of seismic methods language B. Marsh PGS Reviewed by (name) N Forcer, PGS H C Vaage, Fugro-Geoteam Sam Borman Veritas N Forcer, J Hoogeveen, PGS H C Vaage, Fugro-Geoteam S Borman, Veritas R Salisbury, Svitzer D Bruce, WesternGeco T.B.A. EAME Executive Committee IAGC Timeshare Workgroup 12

14 9. Appendices Appendix A Space sharing - - Gulf of Mexico Kilometer Buffer Zone Introduction and Background In response to litigation between the BOEM and NRDC et al., the BOEM introduced mitigation measures that include a required buffer zone between seismic sources of either 40 kilometers in areas of concern or 30 kilometers in all other areas of the Gulf of Mexico Since the settlement agreement on 25 June 2013 the BOEM began including the 40 km or 30 km buffer zone as a required mitigation measures in all G&G permits issued. The buffer zone requirement is only for permitted seismic activities. For example, a seismic contractor with an active seismic source is not required to maintain a 40 km or 30 km from non-permitted seismic activities on lease operations such as VSP or a seismic activities being conducted by or on behalf of a government entity. Current Status The BOEM will hold responsible both seismic contractors involved in any breach of compliance which may result in the issuance of an Incident of Non-Compliance to both parties (contractors). The BOEM monitors compliance by receiving the navigation data (P1-90) on the 1 st and 15 th day of each month and comparing source positions and timing between contractors working in proximity to each other. Providing this data is a requirement as part of the Conditions of Approval of the permit. To assist in the implementation of this measure the BOEM provides all applicants / permittees with contact information for all other deep-penetration seismic applications concurrently permitted/authorized to operate within the or near the survey area. This is done at the time of issuance of the permit. The BOEM has further committed to creating an address group of permittee contact points for all active permits. They intend to update the group with any pertinent information received including intended start and completion dates. However the BOEM does not 13

15 guarantee this information will be distributed as received and may be delayed by up to a week. The IAGC Americas Offshore Committee (AOC) provides a GoM Activity Report which is updated monthly. The report lists company and responsible individual s contact information and location of vessels in the GoM. Basic Objective The objective is for all permit holders in the GoM to avoid any breach of the mandated buffer zone of either 40 kilometers in Areas of Concern or 30 kilometers elsewhere in the GoM. Guidelines The following guidelines are designed to assist in the avoidance of any breach of the buffer zone mitigation requirements: The permittee should take note of the information of other permitted operations in the survey area, provided by the BOEM when the permit is granted. This information should be distributed internally to the operations group as well as to the field crew which will be responsible for acquiring the survey. Any updated information from the BOEM should also be distributed in the same manner Reference should also be made to the IAGC GoM Activity report to establish if other crews are working in the survey area. Prior to the vessel arriving on location, the responsible onshore manager should establish initial contact with all other parties listed as being in the survey area. The purpose should be: o To determine if there is a potential for concurrent acquisition to be occurring within the buffer zone. Survey outlines and proposed acquisition timelines should be exchanged to achieve this. o In the event that such a potential exists, a plan should be developed as appropriate, to avoid concurrent acquisition within the buffer zone. o Where it is not possible to avoid concurrent acquisition within the buffer zone, a plan should be made to timeshare based on equal production time for both parties, as described in the main body of this Timeshare Guidelines document. 14

16 o Both parties should exchange contact information for the designated responsible person in the field (administrator) The resultant agreements should be communicated to both field crews prior to the permittee s vessel arriving in the survey area. As soon as the permittee s vessel(s) mobilizes in the survey area the administrator should contact all the other administrators in the survey area, to: o Establish initial contact and confirm what method of communication shall be used including a backup communication method. o AIS information for all vessels should be exchanged to allow tracking of vessel separation by radar o Establish a communication plan, including but not limited to, primary and back-up contacts and their respective details (offshore and onshore), as well as a schedule for set contact times for communications and updates (offshore and onshore). o Confirm the proposed plan to avoid conflict and make adjustments if necessary. o Any changes to survey extent or timeline should be clearly communicated and shared between the contractors. If timesharing is required the arrangement should be organized and executed as per the guidelines provided in this document, to ensure that any required timesharing provides equal production time. 15