westerngeco internship report (autosaved)

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WesternGeco Land Seismic Acquisition report

Mohammed Azizuddin

Trainee

19/2/15

Table of contents

Mohammed AzizuddinWesternGeco Land Seismic Acquisition report

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1.Introduction 3

2.Quality Control (QC) 3

3.Survey 6

4.Recording 8

5. Vibrators 9

6. Quality, Health, Safety and environment 10

7.Tech Shop 12

8.Administration 13

9.Conclusion 13

Introduction


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The following is a report of my experience as a trainee for the WesternGeco 1959 crew from 4 th February 2015 to 20th February 2015 in the Al Wagan and Qusahwira camps. The main objective of the crew is to provide a complete 2D Seismic survey of the designated area to their client, OMV, an Austrian oil and gas company and a 3D seismic survey for ADCO in Qusahwira.

QC (Quality Control)

The QC department consists of geologists and geophysicists whose primary aim is to verify and validate the quality of the seismic data acquired.

In WesternGeco Schlumberger, single sensors are used instead of the conventional method. The sensors units (GACs) used for production in WesternGeco have 10 sensors on one string which gives the trace information of each sensor on the string whereas the conventional system has a different function. There are 10 sensors for each trace in the conventional method which makes it better at canceling out the noise, hence improving the signal to noise ratio. However, this method is slow and inefficient.

The UniQ system, developed by Schlumberger makes single user sensors a faster and reliable method. The system enables a single recorder to acquire thousands of active channels and double ended sensor strings allow continuous streaming of data and provide power paths even after a cable cut. This increases overall productivity and is a faster method.

Client information is received by the QC department in the form of a parameter letter which includes details about the geology of the area, seismic survey parameters such as number of source and receiver lines, source/receiver line spacing and source/ receiver point spacing, fold requirement, offset distribution etc. Proposals made by the QC department are put forward to the client. Once the client approves a proposal, the QC department designs a pre plan through IManage. This pre plan consists of theoretical coordinates which is sent to the survey department. After the location of the dozed tracks are tracked by the surveyors using Yuma, the coordinates are sent to the QC department which is used to create a production plan through IManage once again. The production plan consists of the exact coordinates of the dozed tracks which are sent to the recording and vibrator departments since they are required to carry out operations on the field. The observer logs that are recorded by the chief recorder and source GPS coordinates by surveyors are sent to the QC department for the daily SPS. The seismic data which is recorded by the recording crew is stored in Portable Data Buffer (PDB). This is a 4TB disk that is sent from the recorder to the QC department. It is in a SEGD format. This seismic data is merged with the daily SPS through Omega and finally sent to the survey department for validation. Daily geometry, daily QC of seismic data and data processing is done through Omega for validation of seismic data.


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Client delivery is the final stage in QC. It includes all the seismic data acquired such as production logs, comprehensive report of vibrator performance, weekly hardwire tests, monthly instrument tests and fold information which is finally sent through 1TB Imation 3592 magnetic tapes. It is in a SEGD format.

The software’s used in the QC department are-B4 imanage cleans the unwanted data and incomplete shots. This software is supported by SPS which provides information on 3 files that are S, R and X files. S file consists of information about all the sources (source line FFID number/code), R file consists of information about all the receivers (receiver line FFID number/code/ GACs) and X file is the relational file that shows the relation between receivers and sources. The imanage software designs, pre-plans and plans production. The survey requirements are provided in a parameter letter which includes all specifications such as fold requirement, offset distribution etc. that help in designing the project. Petrel is proprietary software designed by Schlumberger to do seismic visualization, interpretation and analysis through visualization, analysis and interpretation. It is software used to delineate faults and creates a map. Omega is software used for processing seismic data. The software accurately and efficiently processes land, marine and transition zone data, time and depth data, 2D for reconnaissance, 3D for exploration and development and 4D surveys for reservoir characterization, isotropic and anisotropic (TTI and VTI) velocity fields and multi component data. The survey is in 2D in the case of this project. This gives the client a better idea of the subsurface geology. The difference between the 3D and 4D model is the time lapse difference.

A schematic diagram in the next page explains the process flow in the QC department:


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MERGE

IN OMEGA

Survey

Client information Geology of the area, Seismic survey parameters as provided by the client

Survey coordinates

Acquired coordinates

Daily SPS

Survey Dozer SurveyMapping

VibratorRecorder

Observer logs

Seismic data

Survey

Omega Daily geometry Daily QC of seismic dataDaily processing

Data validation

Tape and Final SPS

Client delivery

Production plan

Preplan

IManage Design Seismic survey


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The survey department consists of surveyors, line clearance (dozing team) and GPS operators. Once the QC department generates the pre-planned coordinates and sends it to the survey department, it is the duty of the surveyors to make sure that accessible routes are created for the vibrators and recording trucks. The main functions of the survey department are:1. To provide GPS coordinates to the front crew for them to lay out the geophones at the pre

planned positions.2. To provide coordinates in garmin GPS for flagging team so that the dozer operators know the

paths to be dozed are within the flagged area. 3. The flagging team makes sure that the flags are placed along the line of least resistance for the

dozers to operate easily.4. A mapping team records the location of the dozed tracks with the use of Arc Pad 10.2 on a mini

PC called Yuma.5. Maps are regularly updated by the surveyors on ‘progress update’ which is included in the daily

report for the client.6. The updated maps are also given to the dozing team to give them better idea in planning and

achieving their targets.7. The total area of the 3D seismic survey that is being performed in Qusahwira desert is roughly

45x35km with obstacles present such as farms, pipelines and palaces also mapped in the Yuma.8. After the coordinate files completely updated, it is sent to the QC department who update the

exact points/coordinates so that the recorders and vibrators can start shooting.

Figure 1 shows dozer creating routes easily accessible for vibrators and recording trucks. Photo taken on 13th February 2015 at 10:50am.


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In 2D seismic survey, the source and receiver lines are laid down in a straight line whereas in a 3D seismic survey such as the project in Qusahwira, the source and receiver lines are perpendicular to each other. The receiver lines are approximately laid in a NW to SE position and the source lines are laid in a NE to SW position. The distance between both the receiver lines and the source lines is 100 meters. The black lines represent source lines and orange represent receiver lines.

North R

RR

R 100M EastWest S

S

S 100M

SouthS


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RecordingThis department consists of Chief observers, Observers, junior observer and line supervisors. The functions of the recording crew are explained in the following steps-

1) Spot equipment- checking all equipment required such as GACs (geophones), fiber optic cables (PIU), fiber optic layout

2) Front crew deploys equipment- the front crew is the group that leads operations. A GPS user tracks points of interests as given by the client in a pathway followed by another person who lays down GACs behind him. Another group behind the GPS operator “shoots” the geophones after which the scan is received in the recording truck.

3) Fiber layout Power Induction Unit (PIU)- Fiber optic cables are more than 20km in length and are hermaphroditic since they allowup to 6 cables in series between FOXs/ PIUsThe Power Induction Unit can power up to 600 UniQ sensor units. It has lightening andemergency shutdown (ESD) protection. Otherfeatures include GPS and WiFI.

4) Fiber layouts Fiber Optic Exchanger (FOX) - Fiber Optic Exchangers are ruggedized 1Gbps routers with 100Mbps communications with PIU network. In the 2D seismic survey in Al Ain, FOXs were connected to a PIU with a short cable from Lo to High as shown in the figure below.

5) Troubleshoot spread/battery- The troubleshooting team fixes problems that may arise after laying out the receiver cables. Weak batteries of PIUs and FOXs are replaced by the troubleshooting team after receiver line number is communicated by the recorder.

6) Acquisition- Once the vibrator trucks send down seismic waves, the waves are reflected back to the receivers. The recording team needs to ensure all seismic data obtained during this process is not void. The recording information received during the day is sent to the QC

Figure 2 shows recording truck located near Al Wagan camp. Photo taken on 6/2/15 at 4:20pm

Figure 3 shows schematic diagram of link between FOX and PIU during 2D seismic survey in Al Ain.


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department in the form of observer logs. These observer logs contain information on receiver line performance.

7) Pick up- A swing truck carries the same cables that were initially laid out on the same line. This allows the recording crew to be more efficient as the receiver lines can be more than 50km. For example: In the 2D seismic survey in Al Ain, line 3 was more than 68kms long.

VibratorsWesternGeco uses DX-80 seismic vibrator trucks that are an industry leading vibroseis source. In the case of the OMV 2D survey, there were a total of 15 vibrator trucks used with 3 groups of four vibrators operating at a time and one spare vibrator in each group. Every group of vibrator trucks has an 18 second maximum displacement sweep. The frequency ranges from 1Hz to 120 Hz with 300millisecond taper to reduce stress. It is the responsibility of the vibe technician to ensure that the vibrators are running smoothly throughout the day, upgrading vibrator with UniQ system and to follow certain guidelines as mentioned by the client. For example: Vibrators must be at least 100m from power lines, 200m from houses, 25m from solid irrigation water pipes etc.One of the groups of vibrator trucks had rubber tracks. These types of vibrator trucks are better than the tyre trucks because of the following:

1) The increased hold down of these units improves the overall geophysical performance of the vibrator.

2) In soft sand, production is increased due to the ability of the RTV to "move-up" between vibrator positions more rapidly thanks to improved traction.

3) In rough terrain, the RTV can maintain a straighter line, minimizing detours due to obstacles.4) In high sand dunes, the RTV has a greater capacity to climb steep slopes. This means that the

amount of bulldozing required for line clearance to provide access tracks for the vibrators is dramatically reduced, minimizing the environmental impact and reducing overall acquisition timeFigure

Figure 4 shows four rubber tracked vibrator trucks operating as a group during 2D seismic operation near palace. Photo taken on 9th February 2015 at 11:44pm.


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QHSE (Quality, Health, Safety and Environment)Schlumberger-WesternGeco places a high emphasis on health and safety in their work environment. Their junior employees (Drivers and workers) are thoroughly trained to follow safety rules. The QHSE department communicates with the management to identify and reduce risks which safeguards the employees. The main elements of management system are-

To ensure the 8 principles work properly, there are regular checks on day to day standards and procedures, on the management system and through modifications to the management system.An example of a safety procedure implemented by the QHSE department that is followed by the WesternGeco 1959 crew is- As a precaution, a three meter distance is required between a diesel truck and dozer while diesel is pumped into a dozer. The dozer operator must also switch off the engine and lower the blade onto the ground. In case of a diesel leak or spill, the dozer operator must take appropriate action such as using cotton pads/cloth/towel to avoid spread of the spill. The incident must be reported to the QHSE department who will take further action on proper disposal of the spill.

Commitment, leadership and management

Policies and objectives

Organisation and resources

Contractor and supplier management

Risk management

Business processes

Performance, monitoring and reporting

Audits and reviews


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The top 10 risks are listed below with examples:1) Land transport- driving cars and trucks (vibrator trucks and recording trucks) on busy roads/ off

road2) Potential energy- stepping, handling and manual lifting3) Machinery equipment and tools- heavy tools, electrical wires, GACs4) Terrain and environment- uneven terrain in desert due to large sand dunes and extreme

weather5) Working near settlements- Private property, farms, animals 6) Bulldozer settlements- Risk around dozing area and dozer rollovers too.7) Hazardous substances – Petrol, Diesel. 8) Work in heat- long work hours in hot weather leads to dehydration. 9) Work near highways/public roads- road crossings, reckless drivers on roads10) Working near underground pipelines- High pressure pipes and possibility of dangerous gases

(H2S) in pipelines make them a hazard.

Figure 5 shows three meter distance between dozer and diesel truck while diesel is being refilled. As a safety precaution, the blade is lowered to the ground. Photo taken on 14 th February 2015 at 12:05pm.


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Tech shopThe tech shop is where the testing of all ground equipment is done to ensure they work properly. This includes the following equipment of Batteries, GACs, Power Induction Units (PIUs) and Fiber Optic Exchangers (FOXs). Other than testing of equipment, the tech shop is also responsible for providing internet network in the camp; ensuring electricity is running and working on problems related to generators. There is a minimum criteria for batteries to be allowed for use on the field-Batteries with black cables need to have a minimum voltage and ampere limit above 12.8v and above 2.8ampBatteries with orange cables need to have a minimum voltage and ampere limit above 12.8v and above 1.8ampThe batteries that pass the test are sent to the recording crew for usage on the field.

Similarly, GACs are tested at the tech shop where bad sensors are replaced, tilt is corrected and check for CRC. Before testing can commence, the GACs are laid down in a pattern before the chief technician checks for any problem with the equipment.

For sensors to pass the test, the following is the criteria required for GACs to operate-Line voltage- 82vLine balance- 0Humidity needs to be below 60%Tilt below 10If the GACs do not match any of the above criteria, it will need to be corrected before it can be sent to the field.

There are hazards associated with working at the tech shop. The top 5 hazards are-

1) Stepping, lifting and handling2) Soldering3) Hot injection Molding4) Air – High pressure cleaning5) Vehicle loading/ unloading

Figure 6 shows GACs laid down systematically with 14 cables parallel to each other and the 15th cable at the end of the pattern.


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The Tech shop also programs the frequencies of 8 radio channels which are crucial for communication within the department and with other departments.

Radio Channel Channel type Frequency1 JM ERP Journey management 153.9252 SUR 1 Survey communication 152.2753 SUR 2 Survey communication 153.0754 TS- REC Troubleshooter 156.8005 FT- REC Front crew 153.7006 BK – REC Back crew 154.4257 VIB -1 Vibe communication 165.0258 VIB - 2 Vibe communication 166.525

Prod – 1 Vibe production 151.400Prod – 2 Vibe production 158.700

AdministrationThe administrator assists the party manager in day to day activities at the camp. This involves- Logistics -Personnel- cars, food, water, diesel, ice -Head count track- Booking flights, visa and accommodation- Timekeeping for juniors and seniors-Coordination of contractor information

ConclusionMy experience of working with the WesternGeco 1959 crew in remote areas of the U.A.E has not only taught me technical skills valuable for a geologist but also improved me as a human being. The employees in various departments especially in the QC department have been open to answering my questions and I would like to thank the crew for giving me the opportunity to work with them. I have observed that technical skills are desirable but learnt that hard work, commitment, clear communication in different levels of management, mutual understanding and respect are crucial for the success of an organization.

westerngeco internship report (autosaved)

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