MDT Modular FormationDynamics Tester

Quality fluid samplesand highly accuratereservoir pressures

Basic MDT configurationfor pressure, permeability

and sampling

Sample chambers

Sample chambers

Single-probemodule

Single-probemodule

Hydraulicmodule

Powercartridge

Multi-probe verticalinterference testing

Flow controlmodule

Dual-probemodule

Single-probemodule

Single-probemodule

Sample chambers

Powercartridge

Hydraulicmodule

The MDT tool can be customized and efficiently assembled on-site to meet exact requirements depending on the needs of a particular well evaluation.

Applications■ Formation pressure measure-

ment and fluid contact identification

■ Formation fluid sampling

■ Permeability measurement

■ Permeability anisotropymeasurement

■ Mini-drillstem test (DST) and productivity assessment

■ In-situ stress and minifractesting

Benefits■ Testing and sampling in

low permeability, laminated,fractured, unconsolidated and heterogeneous formations

■ Fast, repeatable pressuremeasurements

■ Faster tests in low perme-ability—reduced seal lossesand probe plugging

■ Pressure, volume and temper-ature (PVT) formation fluidsamples

■ Downhole fluid differentiation

■ Real-time fluid gradients, permeability and contamina-tion assessment

Features■ Modular, custom-design

capability

■ Multiple samples in one trip

■ Multiprobe and inflatabledual packer module options

■ Efficient integration withother tools

■ Accurate pressure measure-ments using a CQG* CrystalQuartz Gauge

■ Programmable pretest pres-sure, rate and volume

■ Filtrate pumpout prior to sampling

■ Fluid resistivity and tempera-ture measurements at the probe

■ Quantatative sample contami-nation measurement with opti-cal spectroscopy techniques

■ Low-shock and single-phase sampling

■ Field-proven database foraccurate pumpout time

Powercartridge

Live fluidanalyzer

Hydraulicmodule

Low shock PVT-quality sampling

Single-probemodule

Sample chambers

Multisamplemodules

Pump-outmoduleSingle-probe

module

Pump-outmodule

Hydraulicmodule

Vertical interferencetest with probe-packer

Flow controlmodule

Dual-packermodule

Sample chambers

Powercartridge

Real-time measurementsThe Schlumberger MDT* ModularFormation Dynamics Tester tool provides fast and accurate pressuremeasurements and high-quality fluidsampling. It can also measure perme-ability anisotropy. In a single trip, theMDT tool is able to acquire most of thedata requirements needed for accurateand timely decision making.

FlexibilityThe key to this remarkable tool is aninnovative, modular design that lets you customize the tool for the requiredapplications. MDT modules combine to meet the exact needs and goals of thedata acquisition program. This designedflexibility makes the tool compatiblewith almost all Schlumberger measure-ment technologies and allows the MDTtool to evolve as new measurement tech-niques, technologies and options evolve.

Quick, accurate pressure and permeability measurements Reservoir pressure measurements using a wireline tester require insertingthe probe into the reservoir and with-drawing a small amount of fluid. Sincethe pressure gauge is exposed to manytemperature and pressure changes, thesemeasurements require accurate gaugeswith high resolution that can dependablyreact to the dynamic conditions.

The MDT tool uses highly accurategauges with best-in-class resolution,repeatability and dynamic response forpressure measurements. These pressuregauges exhibit excellent response withno compromise in accuracy or resolution.Precise flowline control during testingand sampling ensures monophasic flow.These innovative features provide themost efficient and accurate permeabilitydetermination available.

MDT modulesElectronic power module

The power cartridge (MRPC) converts AC power from the surface to provide DCpower for all modules in the tool. It is anessential part of any MDT configuration.

Hydraulic power module

The hydraulic power module (MRHY)contains an electric motor and hydraulicpump to provide hydraulic power forsetting and retracting the single- anddual-probe modules. The MRHY modulefeatures an accumulator that allows thetest probes to autoretract and prevent a stuck-tool situation in the event of apower failure.

Single-probe module

The single-probe module (MRPS) containsthe probe assembly, (with packer andtelescoping backup pistons), the pressuregauges, fluid resistivity and temperaturesensors, and a 20-cc pretest chamber.The MRPS also contains a strain gaugeand an accurate, high-resolution, quick-response CQG gauge. The volume, rateand drawdown of this chamber can be controlled from the surface to adjustto any test situation, especially in tightformations.

Dual-probe module

The dual-probe module (MRPD) containstwo probes mounted back-to-back, 180°apart on the same block. When combinedwith an MRPS module, it forms a multi-probe system capable of determininghorizontal and vertical permeability.

During a typical test with the MRPDmodule, formation fluid is divertedthrough the sink probe to a one-literpretest chamber in the flow controlmodule. The MRPD module, in conjunc-tion with the pressure measured at thevertical probe from the MRPS module,measures the pressure at both probes.These measurements are used to determinenear-wellbore permeability anisotropy.

Flexible probe configurations are a unique feature of the MDT tool. Byrunning multiple probe modules, pres-sure communication between adjacentformations can be monitored during an interference test. The MDT multi-probe configuration also allows in-situverification of gauge quality and utiliza-tion of two different probe assembliesfor redundancy in difficult conditions.

The multiprobe configuration of the MDT tool measures the pressure response at two or more locations in addition to the single probe data. Data from the MDT multiprobe configuration provide an evaluation of horizontal and vertical permeabilities and formation heterogeneity.

1264 1272 1280 1288 1296 1304X100

X200

X300

X400

X500

X600

0

–8

8

16

24

32

Time (s)

Resistivity(ohm-m)

Pressure(psi)

Hydrocarbonflowing

Samplingstarts Reservoir

pressure

Samplechamber full

Pressure

Flowlineresistivity

In a water-based mud environment, the MDT flowline resistivity measurement helps discriminate betweenfluid contaminated by mud filtrate and formation oil or fresh water.

Dual-packer module

The dual-packer module (MRPA) usestwo inflatable packers, set against theborehole wall, to isolate a 3 to 11 ft. section of the formation and provideaccess to the formation over a wall areathat is thousands of times larger than thestandard probe area. This allows fluidsto be withdrawn at a higher rate withoutdropping below the bubble point, and it provides a permeability estimate witha radius of investigation in the range of tens of feet. The MRPA is useful formaking pressure measurements and taking fluid samples in difficult condi-tions (tight, vuggy, fractured and uncon-solidated formations) and has also beenused in cased holes after a perforationoperation. In addition, the MRPA modulecan be used for in-situ stress testing andmini-frac testing.

The MRPA module employs two inflatable packers to isolate a borehole interval for testing. Tests in low-permeability formations are greatly enhanced, because the cross-sectional area of the isolated interval is many times greater than that of the standard MDT probe.

Modular sample chamberThe Modular Sample Chamber (MRSC)is available in three sizes: 1 gal, 2.75 galand 6 gal. The upper block of eachchamber contains a throttle valve thatcan be operated fully open, fully closedor in throttle mode. The 1-and 2.75-galchambers exist in both H2S and non-H2S versions. The 6-gal chamber can be expanded in 6-gal increments to actas dump chambers by adding more 6-galcylinders.

Multisample moduleThe Multisample Module (MRMS) allowsthe collection of high-quality samplesfor PVT analysis. The module is designedto retrieve six formation fluid samples,450-cc each, during a single trip into thewell. Sample bottles detach easily fromthe tool for transport to a PVT labora-tory. The bottles meet transportationregulations for shipping pressurized ves-sels, so no wellsite transfer is necessary.

Since multiple MRSC and MRMS mod-ules can be combined, the total numberof sample modules is limited only bycable strength and well conditions. Forlonger tool strings, as well as highlydeviated and horizontal wells, the MDTtool can be combined with the TLC*Tough Logging Conditions system forefficient sampling operations.

Multiple MRMS modules—each capable of collecting six high-quality PVT samples—can be combined in onerun to meet sampling requirements.

Chemical analysis of MDT-acquired samples helps to characterize the reservoir fluid and facilitates optimalcompletion and surface facilities design.

Single-phase multisample chamberThe single-phase multisample chamberensures collection of monophasic fluidsamples by overpressuring samples afterthey are taken at reservoir conditions.Sample chambers are pressurized with a nitrogen gas chamber across two pistons. This compensates for the tem-perature-induced pressure drop as thesamples are returned to the surface.

Pump-out module The Pump-Out Module (MRPO) is usedto pump unwanted fluid (mud filtrate)from the formation to the borehole, so representative samples can be taken.It is also used to pump fluid from theborehole into the flowline for inflatingthe packers of the MRPA module. Inaddition, the module can pump withinthe tool, for example, from a samplechamber to the inflatable packers.

fra

)

A. Initial reservoir conditions

B. Nitrogen chargedC. Single-phase

sample

Liquid

Gas0%

Critical point

Pres

sure

Temperature

As they are brought to the surface, samples taken at reservoir temperature and pressure (A) can changephase at lower temperatures and pressures (D). Overpressuring the sample downhole (B) will maintain itsinitial phase as it is brought to the surface (C) at a lower temperature.

0 20 40 60 80 100 120 140 160Time (min)

X700

X600

X500

X400

X300

X200

X100

X000

35

30

25

20

15

10

5

0

POPV(gal)

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

BFR1(ohm-m)

BSG1(psi)

6 galBSG1(probe pressure)

BFR1(flowline resistivity)

POPV (cumulativevolume pumped)

23⁄4 gal

In oil-based mud environments, flowline resistivity may also aid in formation water sampling.

Gas detector Lamp

Flowline

Liquid detectorLiquid

Gas

The LFA module provides real-time downhole fluid analysis by measuring multiple optical properties of the fluid to quantify the amount of reservoir and drilling fluids in the flowline.

Opticaldensity

Wavelength (nm)

500 1000 1500 2000

4

3

2

1

0

Crude B

Oil-basemud filtrate

Diesel

Condensate

Water

Crude A

Opticaldensity

W l th ( )

0.8

0.6

0.4

0.2

01600 1650 1700 1750 1800 1850 1900 1950

Methane

Live crude oil

Dead oil

Optical density spectra can be used to uniquely identify different fluids.

The graph below illustrates the optical density (OD) of methane, dead oil and live crude oil. An OD of zeromeans there is full transmission (no absorption) of light. An OD of 1 means that 10% of the light is transmit-ted, and 90% is absorbed. Methane and dead oil peaks are prominently shown in the live crude oil spectrum.

Live fluid analyzer moduleDownhole fluid analysis in real time, as provided by the LFA* Live FluidAnalyzer module, enhances the useful-ness of new techniques like pumpoutand dual inflatable packers. The LFAmodule measures optical properties of the fluid in the flowline.

The LFA module employs an absorp-tion spectrometer that utilizes visibleand near infrared light to quantify theamount of reservoir and drilling fluidsin the flowline. Light is transmittedthrough the fluid as it flows past theLFA spectrometer. The amount of lightabsorbed by the fluid depends on thecomposition of the fluid. Water and oil are reliably detected by their uniqueabsorption spectra. A second sensor inthe LFA module is the gas refractome-ter, which can be used to differentiatebetween gas and liquid.

Optical absorption in the visible andnear infrared region is used for fluiddiscrimination and quantification; thechange in index of refraction is used for free gas detection; and methanepresence is used for both contamina-tion monitoring and gas detection.

Flow control moduleThe Flow Control Module (MRCF) is a 1-liter pretest chamber where the flowrate can be accurately measured andcontrolled. The MRCF can also be usedduring sampling that requires a controlledflow rate. The volume is limited to 1 liter.The module creates a pressure pulse in the formation large enough for multi-probe measurements.

Prejob modeling and real-time answersThe software capabilities of the MDTtool enhance its hardware capabilities.Drawing on experience based on thevast number of MDT projects that havebeen completed over the past decade,programs are available to accuratelyplan and execute new MDT jobs. Highlysophisticated interpretation programsgenerate accurate pressure gradient,permeability and fluid sampling answerswhen they are needed.

Planning programs are also availableto predict the response of the differentgauges under any given environmentand for any tool configuration. These programs also predict the duration ofrequired pumping time and the likeli-hood of sticking in any given situation.These expert systems, based on thehuge MDT job database, help optimizethe running of the job. In the unlikelyevent that sticking does occur, the LWF*logging while fishing technique can beused to simultaneously complete thesurvey on drillpipe and safely retrievethe stuck string.

MDT interpretation software providesreal-time plotting of pressure, resistivityand optical properties versus time.These plots generate derivatives andperform interpretation at the wellsite.This capability is essential for real-timequality control and ongoing optimizationof the job. Using the InterACT* wellsitemonitoring and control system for real-time data transfer to remote sites,Schlumberger and customer experts cansimultaneously apply more sophisticatedand elaborate modeling and interpreta-tion software offsite.

–25 0 25 50 75 100 125 150Time (s)

Pressurechange

(psi)

Sink probe

Straingauge

Verticalobservationprobe

0

–5

–10

–15

–

–1500

–2000

–2500

5

CQG gauge

Horizontaloobservation probe

The Flow Control Module contains a one-liter pretest chamber and metering valves capable of producingfinely tuned drawdowns.

Observationprobe

Observationprobe

Sinkprobe

Fluid identification exampleThe purpose of fluid sampling is to obtaina representative sample of the virginreservoir fluid. To obtain the sample, theunwanted fluid must be discarded priorto collecting the formation fluid sample.There also must be a method to analyzeand determine the nature of the fluid inreal time. The MDT tool with the pump-out module, LFA module and the flow-line resistivity measurement identifiesand collects high-quality reservoir fluidsamples suitable for further laboratoryanalysis.

Flowline resistivity measurementstaken by the probe module help discrimi-nate between formation fluids and filtratefrom water- and oil-base muds. Equippingthe MDT tool with a pump-out modulemakes it possible to sample fluid, whilemonitoring the flowline resistivity, bypumping filtrate-contaminated fluid intothe mud column. Fluid removed from theformation is excluded from the samplechamber until an uncontaminated samplecan be recovered.

Five samples were collected after 82 min pumping out.

Monitoring the methane peak can show the contamination change. This is not evident with the fluid color response.

One sample was taken after 21 min pumping out.

Formation fluid entry is seen on color and methane peak channels.

Pump-out started

Contamination(%)100 0

Fluid Coloration0.001 0.01 Ch

anne

l 0—

Met

hane

Chan

nel 1

Chan

nel 2

Chan

nel 3

Chan

nel 4

Chan

nel 5

Chan

nel 6

Chan

nel 7

Chan

nel 8

—O

ilCh

anne

l 9

Oil

Water

Highly Absorbing

Fluid

The LFA module monitors oil-based mud contamination by analyzing fluid color and methane content toensure quality fluid sampling. Color and methane curves indicate the percentage of fluid contamination.

SMP-5124 ©Schlumberger

June 2002 *Mark of Schlumberger

www.connect.slb.com

MDT Specifications

Single-probe configurationOD 4.75 in. [120.6 mm]Min hole size 57⁄8 in. [149. 2 mm]†

Max without kits 14.25 in. [361.5 mm]Max with kits 24 in. [610 mm]Pressure rating 25,000 psi [17,235 kPa]‡

Max temperature rating 400°F [205°C]§

Multiprobe tool configurationOD 6.00 in. [152.4 mm]Min hole size 7.62 in. [193.6 mm]Max without kit 13.75 in. [336.5 mm]Max with kit 15.00 in. [381.00 mm]Max pressure rating 25,000 psi [17,235 kPa]Max temperature rating 400°F [205°C]

Dual-packer configurationOD 5.00 to 10.00 in. [127.0 to 254 mm]††

Min hole size 57⁄8 in. [149.2 mm]††

Max hole size 14.75 in. [374.6 mm]††

Pressure rating 25,000 psi [17,235 kPa]Max temperature rating 325°F [163°C]††

LFA moduleOD 4.75 in. [120.6 mm]Length 5.83 ft [1.7 m]Weight 161 lbm [73 kg]Range 0 to 5 optical densityAccuracy 0.01 optical densityPressure rating 25,000 psi [17,236 kPa]Temperature rating 350°F [176°C]

Pressure gauge specifications

Strain gaugeRange 0 to 25,000 psi [0 to 17,236 kPa]‡‡

Accuracy 0.10% full scaleRepeatability 0.06% full scaleResolution 0.1 psi [0.689 kPa]Temperature rating 400°F [205°C]‡‡

CQG gaugeRange 0 to 25,000 psi‡‡

Accuracy 2.0 psi [13.8 kPa]+ 0.01% of readingRepeatability < 1.0 psi Resolution 0.01 psi Temperature rating 400°F [205°C]‡‡

† If wellbore conditions are favorable, the tool can be run on TLC in holes with an ID as small as 51⁄2 in. [14 cm].‡ 25,000 psi [172.5 mPa] for the high pressure MDT and 20,000 psi [138 mPa] for the normal MDT tool§ 350°F [175°C] with some CQG types

†† Functional rating based on the actual packer installed and type of mud used.‡‡ Actual pressure/temperature combination will depend on specific type of gauge. For the CQG, HCQG-A is rated 175°C/25,000 psi, HCQG-B/D 200°C/18,000 psi

or 180°C/20,000 psi and CQG-C/G 175°C/15,000 psi.