surface logging in the oil industry apr 2011

Surface Logging Technologyin oil & gas exploration

Gionata Ferroni – Geolog International

Politecnico di Torino – Petroleum Engineering Course - April 20th, 2011

Table of Contents

1. Introduction to the industry’s technology

2. Geological Analysis applied to hydrocarbon exploration

3. Surface Logging Technology

4. Hydrocarbon Gas Analysis while drilling

5. Geolog

6. Q&A

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Introduction to the industry’s technology

1. Introduction to the industry’s technology

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In this moment there are approximately 400 offshore rigs drilling a well in the seabed.

There are also 3000 rigs drilling wells on 5 continents.

The operating standards of these systems varry significantly:

From basic, small land rigs drilling 500 metres wells in Alberta, to drillships operating ultradeepwater wells offshore Brazil.

We will describe here the equipment utilized to provide geological analysis and monitor the and drilling activity on the more advanced drilling operations.

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LAND RIGLand rigs are utilized for onshore drilling and vary depending on size (which depends on the depth of the well to drill) and on environmental conditions (land drilling can be found in both the hottest and coldest places on earth).

Introduction to the industry’s technologyType of rigs

SWAMP BARGEThis is a floating structure, utilized to drill wells in swamp areas, where neither land rigs or vessels can be towed to or sustained by the soft ground. Common in the southern US and in the Niger delta.


JACK-UPThis is a mobile drilling rig, which requires top be towed over its drilling location. The Jackup has long leg structures, which it lowers to and into the seabed raising the rig out of the water (“Jacking-up”). The obvious limitation with this type of installation is the depth of water it can operate in. The maximum being five hundred feet. Surprisingly, many areas of the North Sea are not too deep for this type of installation to operate.


SEMI-SUBMERSIBLE RIGThis floating drilling unit has pontoons and columns that, when flooded with seawater, can be submerged to a predetermined depth. The structure floats low with a large part of its body under water. This, combined with a number of large mooring anchors, makes it a very stable installation and the preferred choice for exploring deep offshore areas.A Semi-Sub can host up to 100 personnel.Some semi submersibles can drill in water depths over five thousand feet.


DRILLSHIPAs the name suggests, this is a ship-shaped drilling vessel. Unlike the semi-submersible and the Jack-up, it does not require tugboats to tow it to location. They can drill in very deep waters (3000m). The latest generation of drillships has also reached a high level of stability, which used to be a problem while drilling.


Production PlatformThis permanent fixed structure can be built from concrete or steel and rests on the seabed. When oil or gas is located, a platform may be constructed to drill further wells at that site and to produce the hydrocarbon. Although some platforms can be small, most are massive compared to the other types of installations. They can be assisted by Jackups, Semis or Tender barges for drilling. In recent years floating production platforms (FPSO) have been introduced.


Introduction to the industry’s technologyRig systems

• POWER SYSTEM

• HOISTING SYSTEM

• ROTATING SYSTEM

• CIRCULATING SYSTEM

• SAFETY SYSTEM

Drilling a well

• The well is drilled in sections…


Drilling Rig

Marine Riser

BOP – Blow-Out Preventer

The drilling bit progresses. Mud is circulated into the well to remove excavated rock.

• Il pozzo “telescopico”

End of section

Steel Casing

Cementation

Pressure Test

OK

New Section

The “telescopic” well

Drilling a wellIntroduction to the industry’s technology

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Drilling a wellIntroduction to the industry’s technology

Traditional (5 cas.) Profile Lean Profile

The hole sections (which can vary from 1 up to 7 or 8) are drilled with progressively smaller bits, with the typical diameters of:17 ½”, 12 ¼”, 8 ½”, 6”. Each section is followed by a casing run, which gives the well the typical telescopic profile.

Introduction to the industry’s technologyWho’s who on a drilling rig

Company man (drilling engineer) : The representative of the Oil Company or Operator on a drilling location. For land operations, the company man is responsible for operational issues on the location, including the safety and efficiency of the project.

Well site Geologist :Often a consultant, less frequently an Oil Company staff, he is responsible of all items related to the geological interpretation.

Tool pusher :He is responsible for the functioning of the drilling rig for the drilling contractor.The tool pusher is usually a senior, experienced individual who has worked his way up through the ranks of the drilling crew positions.


Driller :He is the supervisor of the rig crew. The driller is responsible for the efficientoperation as well as the safety of the crew and normally has many years of experience. The driller drives the rig : he operates the pumps, draw works and rotary table via the driller console.


Drilling Crew :The crew consists of motor man, roustabouts, roughnecks, floor hands, lead tong operators, derrick men, and assistant drillers.

Service companies:

The Mud Engineer is responsible of the drilling fluid (mud). He tests it continuously and prescribes necessary treatments to ensure the recommended properties. He also works closely with the rig's derrick man, who is in charge of the treatment.

The Directional Driller is responsible of the correct trajectory of the well in case of directional well (inclination and azimuth).He will consider parameters as rotary speed, weight on bit, down hole motors and will monitor the trajectory according to the deviation surveys.

The Cementer is in charge of preparing and pumping the cement slurry needed to cement the casing after a section of the well is run.

The Mudlogger runs the geological laboratory and gathers drilling, geological and gas data. He provides the main and most detailed monitoring system of the rig.


MWD – LWD Operator :He is in charge to collect and analyze data coming from MWD or LWD tools. MWD (Measurement While Drilling) is a special tool that allows to measure different parameters (mainly deviation) while drilling. Those measurements are made downhole, stored in solid-state memory for some time and later transmitted to the surface. Data transmission methods vary from company to company, but usually involve digitally encoding data and transmitting to the surface as pressure pulses in the mud system.LWD (Logging While Drilling) measures formation parameters like resistivity, porosity, sonic velocity, gamma ray.

Casing Operator:In charge of running the casing into the hole. Ensures that each joint is in good order and is properly screwed onto the previous one.

Coring Hand:In charge of running the coring equipment and collecting the core samples.


Geological Analysis applied to hydrocarbon exploration

2. Geological Analysis applied to hydrocarbon exploration

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Geological Analysis is one of the 3 main mudlogging duties.

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The Geological analysis reveals what lithologies have been encountered while drilling and what were their characteristics.

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Several “quicklook” analysis are done on the field to provide the initial lithological interpretation.

Although more in-depth analysis can further be done in the laboratory, this initial information is crucial to understand if a hydrocarbon reservoir is present.

A Mudlog is the result of this field analysis.


Microscopic analysis of the cuttings:

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Siltstone Limestone

TuffBasaltDolomite

Sandstone



Further analysis: Calcimetry – Measurement of the percentage of calcium and/or of calcium-magnesium carbonate in rock samples or cuttings.

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The calcimetry analysis enables to identify lithology and to correlate in between offset wells.

Fluorescence of rock samplesDirect (Natural fluorescence) under U.V. Light – it provides an indication of what type ofoil is present in the rock, if any.


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High accuracy bulk density

Variations in the sample bulkdensity are a directindication of:Lithology change.Shale compaction andwater content.Presence of organiccontent.

The absolute reading is lessrelevant since the rockreleases pressure after beingexcavated.

Surface Logging Technology

3. Surface Logging Technology

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Scope of the Surface

Logging Service

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Real-Time Monitoring is granted by a number of electronic sensors distributed around the rig and an acquisition system which:

Gathers all the data in a database

Runs software applications enabling usage

of the data

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Review of the sensors utilized:

- Sensors measuring the movement and behaviour of the drilling system

- Sensors measuring the parameters of the drilling fluid

- Sensors detecting the gases liberated by the drilling fluid

All these sensors have an accuracy varying from 0.01% and 1% of the reading and are manufactured to operate in harsh environments and explosive atmospheres for months on end.

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Sensors measuring the movement and behaviour of the drilling system

Vertical Movement of the Drill String

Measured with a drawworks encoder

The sensor enables to measure the movement of

the hook and to calculate:

-Hook Speed

-Rate Of Penetration (ROP) – main parameter to evaluate drilling efficiency.

-Position of the drilling bit relatively to the bottom of the well.

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Sensors measuring the movement and behaviour of the drill string.

Rotation and Torque of the Drill String

Rotation (RPM)

Measured with a proximity switch mounted

on the Top Drive.

Torque (kgf*m)

-Measured with a Hall-Effect sensor (measures the EM field induced

by variations in the electrical current).

-Installed on the mains power supply of the drawworks.

Torque measurement – crucial to evaluate well stability

Problems or well overpressure problems.

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Weight of the Drill String

Weight on the Hook (WOH, tons)

Measured with a strain gauge cell mounted on the deadline.

This sensor provides a number of important weight

Measurements, apart from the WOH:

Weight on Bit (WOB) – the weight of the string released on the

drill bit.

Overpull/Drag – the weight of the string being released on the

wellbore walls.

Indicators of drilling efficiency and of potential pipe stuck problems.

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Pumps Regime

Measured with proximity switches monuted on the

body of rig pumps.

The pump rate is used to calculate a number of parameters:

-The mud flow rate.

-The lagtime of the rock samples and gas being drilled.

-Hydraulic parameters such as flow type, bit hydraulic

force, reynolds number and pressure losses.

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Pressures in the drilling system.

Standpipe Pressure sensor (Bars, psi)

Measured with a pressure cell installed on the rig’s Standpipe

manifold.

This sensor measures the pressure of the rig pumps.

This pressure is an indication of:

-The pumps regime

-The pressure losses in the well

-The integrity of the drill string

-The onset of a kick.

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Sensors measuring the parameters of the drilling fluid.

Level of drilling mud in the pits

Pit Level sensor (m3, bbls)

Measured with a sonic beam bouncing back from the

surface of the fluid.

Crucial for operational safety:

An unexpected drop of the mud level means the rig is

losing mud to the well.

An unexpected gain means the well is kicking – potential release of hydrocarbons to the surface – possible blowout.

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Muyd characteristics

Mud Density Sensor (g/cc, ppg)

Mud Temperature Sensor

Changes in these parameters can indicate an imbalance of the

Well pressure, potentially leading to wellbore damage or to a

Kick.

Other sensors measure:

Mud conductivity

Mud pH

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Mud flow Rate

Electromagnetic Flow Sensors

Coriolis Flow Sensors

Litres/minute, gpm

This is one of the most important parameters ,

because it indicated directly if the well

is in a balanced condition. Losses or

gains in the flow must be recognized

acted upon immediately.

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Sensors Location on a drilling Rig


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Hydrocarbon Gas Analysis while drilling

4. Hydrocarbon Gas Analysis while drilling

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Gas Detection and analysis is the core of the mudlogging service.It represents the real original contribution of this service to the drilling process.

Gas Data liberated while drilling provide a direct indication of:-Amount of hydrocarbon content of the rock.-Type of hydrocarbon present (oil, gas, condensate).-Changes in the characteristics of the fluid type and composition with depth.

The importance of these data is that, often, they are the only direct Formation Evaluation data available in Real-time.

So, how are these data collected?

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How is gas extracted from mud?

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An extractor (“gas trap”) phisically stirs the gas out of the mud.The gas is dried and sent to the mudlogging cabin via a gasline.

The extraction ideally is done at constant flow, T and P.


How is gas delivered to gas detector?

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A pump in the cabin draws gus from the

Gas trap and sends it through a Gas

Distribution System. This system controls

the flow of gas sample and grants:

•Control on the sample flow, which is dictated by the pressure losses along the

gasline and the length of a gasline. This prevents gas data variations not

related to gas in mud but to the gasline.

•In case a change of the suction flow is needed (excessive gas-or the

opposite) it can be done with a GDS. This must be recorded on logs.

•A GDS, enables to use multiple gas detectors in parallel.


What gases arrives to the gas detector?

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Hydrocarbon Shows While Drilling

Methane – CH4

Ethane – C2H6

Propane – C3H8

Butane – C4H10

Pentane – C5H12

Other gases analyzed are:

Hexane, Aromatics, heavier hydrocarbons.

Non-hydrocarbons such as: CO2, H2S, atmospheric gases.


How are gases analyzed?

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Gas

mixture

from Trap

Gas Chromatograph

Analysis C1 - C5

Frequency: according to cycle time (60 to 240 sec)

Total Gas detector

Continuous (or semi-continuous)

analysis


Chromatography: necessary step to separate all the species in a gas mixture enabling their measurement by a detector.

The main type of gas detectors utilized are:

Flame Ionization Detectors: the most commonly used due to their accuracy in measuring hydrocarbons.

Thermal Conductivity Detectors: enable to measure also some non-hydrocarbons.

Mass-Spectrometers: these are more complex and enable to measure any volatile substance.

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Flame Ionisation Detector (FID)

The FID utilizes a flame produced by the combustion of hydrogen and air. When

an organic compound enters the flame it is burnt and then part of it is ionized,

which results in the production of electrons and positive ions. The stream of freed

electrons is directed to a measuring circuit by a polarizing electrode within the

detector. The measurement circuit senses the electron stream as a current that is

proportional to the amount of carbon in the flame.


Thermal Conductivity Detector (TCD)

Thermal Conductivity Sensor

Relationship between Thermal Conductivity and Molecular Weight

0

50

100

150

200

250

300

350

400

450

500

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Molecular weight

Th

erm

al

Co

nd

ucti

vit

y (

Kcal/

mo

le/°

C)

Hydrogen

Helium

Methane

Acetylene

Nitrogen

Air

Ethane

Oxygen

Propane Butane

The detector consists of a

Wheatstone bridge circuit

with a tungsten filament.

Voltage will depend on the

thermal conductivity of the

gas passing by the heated

metal surface.

This in turn depends upon

the molecular kinetic energy

of the gas and is inversely

proportional to the

molecular weight of the gas.


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Mass Spectrometer

In the oilfield, MS are invariably associated with a preliminary chromatographic separationof the components (GCMS): Once the gas species are separated, they enter the MS chamber,where high-vacuum is maintained (10-6 atm): in the chamber, gases are bombarded by astream of electrons causing them to break apart into ions.

All gases break apart in a very rigid pattern, and the ratio of each ion is fixed. Each ion has aspecific mass.

The ions are then conveyed to an electromagnetic quadrupole.

The quadrupole is programmed to select only ions ofa certain mass through the slit. The rest bouncesaway. The quadrupole cycles through different ionicmasses one at a time, covering the range of selectedmasses. This occurs many times per second. Eachcycle of ranges is referred to as a scan.



How are gas data utilized? Some examples.

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Formation change and Gas levels

Below is an example log: Note that the variation in the lithology is the

primary cause of:

a) An increase in the ROP.

b) An increase in the gas level.

The claystone has no porosity so has no gas. Plus, it acts as a trap for

the gas in the formation below (in this case a limestone with diagenetic

porosity).

ROP Lithology Calcimetry Gases C1 to C5


Formation fracture and Gas levels

In the example below the gas peak is not related to a formation change. The gas comes together with a spike in the ROP, which indicates a possible fractured zone which liberates more gas.

ROP Lithology Gases C1 to C5

With limestone reservoirs very often the presence and production of hydrocarbons is dependant on the fracturation of the formation.This fracturation can also lead to significant mud losses.


well in Romania –Oil Reservoir identified by DualFid Star

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DualFid Star – heavy gas detection

Light Gases do not provide sharp indication of top of oil. Heavy Gases (nC6 to Toluene ) do.

GOC

Top Gas

Heavy gas peaks match very well thin sand stringers.

Gas-Oil Contact (GOC): gradual increase of C3-C5, but clear identification from heavy species at 2784m.

Light Gases Heavy Gases

Case History 203

Identification

of Oil

Reservoir

with heavy

gas detector


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MDT Data

Wet gas gradient

Light Oil gradient

GOC

Separate gas and oil producers identified

The LWD resistivity showed gas for the entire section.

The gas Balance (Bh) ratio showed however two clearly separate compositions, indicating different hydrocarbon fluids (gas in the top two shows, oil in the remaining hydrocarbon shows.

The MDT data confirmed the results of the gas analysis. A light oil pressure trend and a clear gas-oil contact are seen.

Case History 007


Geolog

5. Geolog

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Company Profile

GEOLOG is the largest independent international mud logging company in the world

GEOLOG is an oilfield services company operating at the forefront of technology in thefield of surface logging

GEOLOG´s growth is to be attributed, amongst others, to its technological leadership inmud logging and its strong focus on proprietary research and development

Brief history

- GEOLOG was founded in 1982 to provide ML Services to Eni (Agip) in Italy

- Remained mono country (Italy) mono client (AGIP) till 1994

- Venezuela (1994) Congo (1995) Tunisia (1995)

- REAL EXPANSION DRIVE since 2000

• Recruited over 250 graduates in Spain – Portugal - Romania -UK - France – Italy - Poland – Algeria – Iran – India – Pakistan – Turkey –

Tunisia – Venezuela – China

• Wellsite training center on deep well in Italy

• Training Centers in Hassi Messaoud, Bucharest, Milan, Tripoli, Congo, Kuwait

• Manufacturing 14 to 18 units per year ( sales + services)

In the World

17. Kuwait18. Libya19. Mexico20. Netherlands21. Norway22. Peru23. Romania24. Russia25. Spain26. Tunisia27. Turkey28. UAE29. UK30. USA31. Venezuela

1. Algeria2. Angola3. Argentina4. Australia5. Bolivia6. Brazil7. China8. Colombia9. Congo10. Croatia11. Denmark12. Gabon13. India14. Indonesia15. Italy16. Kazakhstan

GEOLOG Presence

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Onshore:• Exploration wells• Development wells• Geothermal wells• Extended Reach Drilling• Workover• Underbalanced

Offshore:• Exploration wells• Development wells• Extended Reach Drilling• At-balance (MPD)

Deep & Ultra-Deep water wells(2,200m + water depth):• Angola• Mauritania• Italy• Trinidad• Turkey• Venezuela

HP / HT wells(7,500 meters, 370 °F):• Argentina• Austria• Italy• Kuwait• Mexico

Customer References

GEOLOG’s principal National Oil Company clients include:

GEOLOG’s principal International Oil Company and corporate clients include:

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GEOLOG’s Integrated service clients include:

Core Business

• Reduction of fishing operations caused by pipe wash-outs pressure monitoring

• Prevention of drilling string failures and twist-offs

- Via real time detection of down hole string vibrations SDC Vibration Analysis

• Piloting horizontal well (navigation)

- Via fast accurate gas chromatographs GWD Geosteering

• Optimisation of development drilling

- Via well-to-well correlation and field data bases

• Prevention of drilling problems

- Via real-time evaluation of down hole cavings and cuttings volume CVM

• Hydrocarbon bearing formations containing:

- Conductive fluids- Fresh formation water

• Detection of hydrocarbons in deep fractured reservoirs

• Identification of reservoir units with gas ratios analysis

• Identification of fractures while drilling (and possible modelling to a field) EM FlowMeter or Coriolis FlowMeter

• Identification of formation fluids whiledrilling – Geofluid Mass Spectrometer

• Prevention of formation damage in depleted reservoirs

• Prevention of blow-outs via early detection of kick & loss

- Early detection of kick during drilling

- Advance detection of high risk blow-out situations

- Detection of kicks during tripping in & out

- Detection of hazardous gases at rig site

To Detect & Evaluate Reservoirs

To Reduce Drilling Time & Costs To Improve Rig Safety

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On shore, Off shore, body certified A0 for harsh environment

Skid mounted or container type

Complete Laboratory for geological analysis & sample conditioning

Standard Safety Equipments / Pressurization

Mud Logging Unit

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Mud Logger

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Mud Logger

Work shifts: 12 hrs per day – 7 days per week.

Work tour: 4-5 weeks of work, 2-4 weeks off.

Crew of 4 people: 1 Data Engineer + 1 Mudlogging geologist per shift.

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Work Environment

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Work Environment

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Work Environment

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Work Environment

GEOLOG’s employees are our most valuable asset

GEOLOG invests heavily in their recruitment, training and development

• Around 1000 people work for GEOLOG

– 95% university graduated

– High percentage of geologists and a mix of Electronics and Petroleum Engineers

• Very strong emphasis placed on training and development of staff

• 10 full-time training centres spread across its regions of operations to focus on its local workforce:

• Geolog actively pursues stages and summer work experiences with students

Personnel & Training

– Milan, Italy

– Tripoli, Libya

– Ploiesti, Romania

– Hassi Messaoud, Algeria

– Luanda, Angola

– Point Noire, Congo

– Maturin, Venezuela

– Kuwait City, Kuwait

– Balikpapan, Indonesia

– Villahermosa, Mexico

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References & Contacts

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HeadquartersGEOLOG International BV

Operations/HR/FinanceDe Entree 242 9H1101 EE Zuid-OostAmsterdam, The NetherlandsMob +31 (0)6 156 49819Tel +31 (0)20 342 0620Fax +31 (0)20 342 0645

Production/TechnicalVia Carlo Porta, 2120098 San Giuliano MilaneseMilan, ItalyTel : +39-02982521Fax: +39-0298252324 (Technical Dept)Fax: +39-0298247270

Questions & Answers

6. Q&A

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surface logging in the oil industry apr 2011

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