5.

Introduction to Wire Line Formation

Tester Tools (RFT/MDT/XPT)
Chronicle of Schlumberger Formation Testers

Pressure Xpress
XPT

2005- present
 WFT Applications
Formation Pressure
Pressure gradient
Formation fluid samples
Permeability /mobility

• Virgin Reservoirs • Developed Reservoirs

- Fluid contact level - Characterize vertical and

- formation fluid density in situ horizontal barriers
- reservoir heterogeneity - Vertical permeability (MDT )
- completion strategy - Detect thief zones
- optimize mud density for infill - Hydraulic communication
drilling between wells
- Fluid contact movement
RFT Pretest And Sampling System
MDT Specification
 XPT Specifications
•Rating: 20,000 psi and 300°F
•Diameter: 3.375 in.
• (3.875 in. at probe)
•Length: 21.3 ft
•Hole sizes: 4.75 to 15.4 in.
•Gauges: 2 Sapphire, Quartz
optional
•Pretest volume: 0.1 to 37 cc
•Pretest rate: 1.2 to 160 cc/min
 Efficient Operations
4500m well depth
Platform
Express 1500m logged
20 MDT
19 interval
hrs
18 hrs Rig down
Pull-out-of- 50 pressures
hrs
16 hole
hrs
14
Pressure tests Platform
hrs
12 Express
hrs
10 PressureXpress
hrs
8 Stabilize
8 hrs Rig down
Run
CQGin hole Pull out of
hr
6 Change hole
Pull out of Pressure
hr
4 toolstrings
Log
hole tests
Log
hr Downlog Downlog
2 Run in hole Run in hole
hr
0 Rig up Rig up
hr
 Pretesting
• A probe is set onto the
borehole, sealing it
from the drilling
fluid

• A small volume of
formation fluid is
withdrawn, followed
by a buildup

• From the analysis of

the data, formation
pressure,
drawdown and
buildup mobilities are
obtained
Typical Pressure Test
Typical Pressure Test

Time Sapphire Gauge Quartzes Gauge

Typical Pressure Test – Example
Drawdown Mobility = 32.8 md/cp
Some Operational Challenges in WFT

• Depth Matching
• Lost Sealing
• Dry Test
• Build Down
• Packer Leakage
• Supercharging
 Depth Matching

GR

Pay Zone
Lost Sealing – Wash out
Lost Sealing

Wash Out

Lost Sealing @ 3468

Lost Sealing @ 3476

Pretest Flow Regimes
Pretest Flow Regimes
Pretest Flow Regimes
Flow Regime Pressure Derivatives
Pretest Flow Regime Diagnostic
Pretest Flow Regime Diagnostic
Pretest Flow Regime Diagnostic
Pretest Flow Regime Diagnostic
Dry Test
Dry Test Derivative Trend
Build Down effect
Solution for Build Down effect
Repeat Pretest
Packer Leakage
Packer Leakage
Packer Leakage- Field Example
Packer Leakage- Field Example
Solution For Packer Leakage
Apply more drawdown
Solution For Packer Leakage - Apply more drawdown
Supercharging
Excess Pressure due to mud filtrate Invasion
(Supercharging)

Typical Mud Static Filtration

Loss Rate = 0.05 cc/min/100 cm^2

SPE 1132
Supercharging
Identifying Supercharging
Effects in XPT/MDT
 Supercharging
Pressure [psia]
6450 6460 6470 6480 6490 6500 6510 6520 6530 6540 6550 6560 6570 6580 6590 6600
3680
Formation Pressure (PS)

Formation Pressure (PA)

3690
Water Gradient defined by PA test

Oil Gradient 0.318 psi/ft

3700 Water Gradient 0.488 psi/ft

PS…Single Probe; PA…Dual Packer

3710
Depth [m]

3720 Supercharged Data Points

3730
Poss. OWC @ 3,735m

3740

3750 Water Gradient defined through Dual PA tests

shifted parallel through pressure point @ 3,739.5m,
where log interpretation clearly shows water
3760
WOC
 Best Practices for Determining
Reservoir Pressure in PressureXpress
Formation Tester(XPT)
• Use mud log to determine minimum pressure for
pressure limited drawdown

• Continue monitoring buildup pressure until the

pressure change = 1 psi/min or less, or you’re
certain it would take too much time (ultra-low
K/u) to wait for pressure to stabilize
Typical Pressure Test – Example
Drawdown Mobility = 32.8 md/cp
 Best Practices for Determining Reservoir
Pressure in PressureXpress Formation Tests

• Generate log-log plot of radial (and

spherical) derivative, and observe end
time data of the radial derivative (looking
for IARF)

• Repeat pretests until confirmation of

pressure is certain
PressureXpress Data with 6 Repeats
With each pretest,
pressure is
decreasing
slightly,
suggesting
supercharging
Diagnostic Log-Log Plots of Shut-in Data

In all cases, the

pressure derivative is
going to zero at late
time… indicating
constant pressure
support
Diagnostic Log-Log Plots of Shut-in Data

Again, constant
pressure is
indicated by
derivative in each
test
Last Read Pressures Support Supercharging
Decreasing
pressures from
pretest to pretest
suggest
•Shut-in #1 9173.19 psi supercharging is
being relieved with
•Shut-in #2 9157.29 psi -15.9
each psi
sampled
•Shut-in #3 9148.08 psi -9.21 psi
volume
•Shut-in #4 9141.61 psi -6.47 psi
•Shut-in #5 9139.22 psi -2.39 psi
•Shut-in #6 9136.30 psi -2.92 psi
•Shut-in #7 9132.36 psi -3.94 psi
 Evidence of Supercharging

•With each pretest, pressure decreases

indicating supercharged pressure is being
relieved by sampling volume

•Pressure derivative goes to zero, Suggesting

constant pressure support (from mud)
XPT Pressure Data Showing True
Reservoir Response

Last two pretests

repeat same
pressure
Diagnostic Log-Log Plot of Infinite Acting
Radial Flow (IARF) Response

Here, pressure derivative shows a

constant slope, (NOT constant
pressure) i.e., infinite acting radial
flow has developed when pressure
stabilizes
 In Summary…
•Use mud log to determine range of pressure-
limited drawdown

•Continue buildup until pressure stabilizes

•Repeat, repeat, repeat

•Use radial derivative plot to determine flow

regime
Secondary Supercharging
Secondary Supercharging
Secondary Supercharging
 WFT Applications
Formation Pressure
Pressure gradient
Formation fluid samples
Permeability /mobility

• Virgin Reservoirs • Developed Reservoirs

- Fluid contact level - Characterize vertical and

- formation fluid density in situ horizontal barriers
- reservoir heterogeneity - Vertical permeability (MDT )
- completion strategy - Detect thief zones
- optimize mud density for infill - Hydraulic communication
drilling between wells
- Fluid contact movement
 WFT Applications
Drawdown Mobility
During drawdown, most of the fluid movement takes place in a small volume
immediately sorrounding the probe. Usually mud filtrate from the invaded zone.

(k/μ)d = Cpf x q / Dpss

Where,
k = Permeability
μ = viscosity of fluid
Dpss = steady-state drawdown pressure drop
q = pretest flow rate

Cpf = drawdown proportionally factor

5600 Conventional long nose packer
2395 Large diameterlong
1107 Large area packer
Pressure Gradient and fluid types
 WFT Applications
Identifying fluid types, densities and contacts

Pressure
gradients gives
insitu fluid
densities(psi/ft)
 WFT Applications
Identifying fluid types, densities and contacts

Balarud #1 - MDT - Asmari

1100

y = 4.8243x - 9059.6
R2 = 0.936

1200

0.06 psi/ft
1300

1400
Depth , mMD

1500

GOC
1600
y = 0.9096x - 422.71
R2 = 0.9974

1700
0.32 psi/ft

1800
2000 2050 2100 2150 2200 2250 2300 2350 2400 2450 2500

Pressure , psi
Gradient Intercept technique
Typical Fluid Gradient
Variation of Hydrostatic pressure with
formation water salinity
 Practical Correlation for Formation
water density
Fm. Water Salinity Vs Density

80
Density (pcf)

75

70
y = 0.0509x + 61.448

65
150 200 250 300
Salinity( M ppm)
 WFT Applications
Gradients showing vertical barrier
 WFT Applications
Gradients showing vertical barrier

A shale barrier is
evident in
the FMS images,
causing the
pressure
difference
between
zones. It is quite
hard to
determine this
thin shale
with
conventional
logs
 WFT Applications
Gradients showing vertical barrier

Pressure
Difference near
1000 psi
 WFT Applications
Vertical flow barriers
 WFT Applications
Vertical flow barriers
 WFT Applications
Effects of transition zone
 WFT Applications
MDT pressure profile in horizontal wells
 WFT Applications
optimize mud density for infill drilling
 WFT Applications
optimize mud density for infill drilling
Pressure Gradient
Pressure Gradient – Error Analysis
 Pressure Gradient – Error Analysis
The Effect of pressure and depth measurement errors on gradient determination
Pressure Gradient – Error Analysis
George Stewart SPE 11132
Pressure Gradient – Error Analysis
George Stewart SPE 11132
Pressure Regime & Layering
Layers Communication Example - Oil
4500

Khalij
Lower Gd
Linear (Khalij)

4510
Pressure Gradient = 0.31 psi/ft

4520
Depth ( mdd)

y = 0.9589x - 7657.1

4530

4540

4550
12600 12650 12700 12750 12800 12850 12900 12950 13000
pressure( psi)
Layers Communication Example - Gas
Layers Communication Example - Gas
Sefid Zakhour 1 - XPT Pressure vs Depth
4300
Hyd press
Fm Press
Superchared
Linear (Fm Press)
Upper Dalan
4400

4500

4600

Nar

4700
Depth ( mdd)

4800
Lower Dalan

4900

5000 Superchared

5100

5200

Gas Pressure Gradient = 0.1148 psi/ft

5300
7500 8000 8500 9000 9500 10000 10500 11000
pressure( psi)
Layers Communication Example - Gas
Layers Communication Example - Gas
Pressure Regime & Layering
Layered Reservoirs Example
Layered Reservoirs Example
Well Kushk 1
Layered Reservoirs Example
Well Kushk 2
Layered Reservoirs Example
Well Kushk 2
Connectivity Between Wells
Connectivity Between Wells
Connectivity Between Wells
Pressure Gradient Interpretation
Well Kushk 1

Aquifer Zone 3

Aquifer Zone 2
Pressure Gradient Interpretation
Well Kushk 2

Aquifer Zone 2

Aquifer Zone 3
Pressure Gradient Interpretation
Pressure Profiling in Developed Fields
 WFT Applications
Pressure profile in a development well
Effect of Depletion on the reservoir pressure profile
Pressure Profiling in Developed Fields

Partially Depleted

Not Depleted
Dual Packer Pretest in MDT
MDT- Vertical Interference Test(VIT)
 METHOD
Reservoir
Sample
Chamber SINGLE PROBE
MEASUREMENT:
• Reservoir Pressure
A • Spherical mobility in the
vicinity of the borehole
Single
B Probe
B’ COMBINING YIELDS:
• Measure of vertical flow
• Greater extent
C Sink
Probe
 Pump

B ? V1

B’

C SINK
Dual Packer
MDT- Vertical Permeability
WFT Data Reporting
Fluid Sampling
 Who needs Fluid Information
Completion/ Facilities/flow
production assurance
Engineer engineer
• Completion design • Flow assurance
• Material • Separation
specification • Treatment
• Artificial lift • Metering
calculations • Transport
• Production log
interpretation
Fluid
Fluid
• Production facilities Data
Data
design
• Geologist
Production forecasts Reservoir
• Reservoir Engineer
correlation • Reserve estimation
• Geochemical • Material-balance
studies calculation
• Hydrocarbon • Natural drive
source studies mechanism
• Reservoir
simulation
• Well test
interpretation
Sampling Techniques
 WFT Fluid Sampling

• RFT Sampling
Not Valid - only invaded zone sample obtained- two fixed volume

• MDT Sampling
representative reservoir fluid sample and valid for PVT analysis
RFT Technique

P&T
 MDT Technique
wellbore

Pressure Control
Pu mp

Contamination Op tics
Monitoring
& Detection of
Phase Separation
P&T
MDT fluid sampling

Pumpout module

Multisample module(s)
(Six 450cc samples)

LFA/CFA
L am p
Single probe F luo rescence D etecto r
module

Sam p le F lo w
Packer module F lo w line

Sp ectro m eter
(G as Analyzer)
 Why MDT Open Hole Sampling ?

• You know the exact depth.

• We can control the sampling process.
• Undisturbed fluid from the clean-out
during the DST.
• Do whole Fluid Analysis Ability
MDT Sampling
 MDT Sampling
Before Clean Up After Clean Up
MDT Live Fluid Analyzer