Porosity and Lithology in
Complex Environments
Integrated evaluation
for more accurate
answers
Applications
■
Formation evaluation in complex environments, such as
shaly sands, mixed-lithology
carbonates, high-salinity
fluids and micaceous sands
■
Stand-alone gas identification
■
Porosity measurement
■
Lithology identification
■
Thin-bed analysis
Benefits
■
Improved gas detection in
shaly reservoirs
■
Improved reserve estimates
■
Identification of thin pay-zones
■
Efficient wellsite operation
saves rig time
■
Reduced radiation hazard
with sourceless porosity
measurement
Features
■
Combinability with ECS*
Elemental Capture Spectroscopy sonde to provide robust
petrophysical properties
■
High-yield pulsed-neutron
generation
■
Thermal neutron and
epithermal neutron porosity
measurements
■
Real-time correction to reduce
environmental effects
■
Improved vertical resolution
■
Sigma measurement
■
High-efficiency gamma ray
detectors
■
Enhanced data validation and
quality control
■
Modular tool design
Simplified porosity and lithology
evaluation in difficult reservoirs
The IPL* Integrated Porosity Lithology
system provides accurate formation
porosity and lithology information,
even in reservoirs that are difficult to
evaluate with standard tools. This system acquires new-generation neutron
porosity, natural gamma ray spectrometry, density and photoelectric effect
measurements using one modular tool.
Neutron porosity measurement
The APS* Accelerator Porosity Sonde,
which uses an electronic neutron
source instead of a chemical source,
is the heart of the IPL system. Because
the neutron source has a large yield,
it allows the use of epithermal neutron
detection and borehole shielding to
obtain porosity measurements that
are affected only minimally by the
borehole environment and formation
characteristics, such as lithology and
salinity. Five detectors provide information for porosity evaluation, gas
detection, shale evaluation, verticalresolution improvement and borehole
corrections.
measurement stability. This sonde
records the full pulse-height spectra
from both detectors and processes
information into windows. Bulk density
and photoelectric effect (Pe) information are derived conventionally. The
spectral information available is used
for improved log and calibration quality control.
Full modularity
The control electronics for the IPL
system sensor array are compact, yet
fully modular. They allow the tool to
be run as a stand-alone platform or
the individual sensors to be run in
combination with other Schlumberger
platforms and tools.
Solutions for tough problems
The IPL system and tool combinations
provide interpretation solutions in
many conditions that are difficult to
evaluate with traditional wireline
measurements, such as thin beds, shaly
sands, mixed-lithology carbonates,
high-salinity fluids, micaceous sands
and rough or difficult hole conditions.
Thin beds
Natural gamma ray measurement
The HNGS Hostile-Environment
Natural Gamma Ray Sonde incorporates technology that enhances answer
quality. Increased detection efficiency
with spectral processing significantly
improves measurement precision and
reduces environmental corrections.
Sensitivity to the barite content of
mud is eliminated by using only the
high-energy gamma rays for analysis.
The MAXIS* Multitask Acquisition
and Imaging System corrects for borehole size and the borehole potassium
contribution—in real time.
The APS porosity measurement’s
improved vertical resolution and lower
sensitivity to clay make identification
and evaluation of thin beds much
easier. The thermal neutron formation
capture cross section (sigma) measurement can be used to greatly improve
the vertical resolution of the shale evaluation usually obtained from gamma
ray information. When the APS sonde
is run with the AIT* Array Induction
Imager Tool or ARI* Azimuthal Resistivity Imager, the combination provides
a vertical resolution of about 1 ft.
Shaly sands
Density and photoelectric
effect measurements
The Litho-Density* sonde has a pad
with a gamma ray source and two
detectors. Magnetic shielding and highspeed electronics ensure excellent
Because clay has little effect on the
APS neutron-porosity measurement,
the gas effect in shaly sands is more
visible. This reduces the chance of
missing a pay zone.
Mixed-lithology carbonates
Micaceous sands
The degree of dolomitization in a formation has little influence on the APS
carbonate porosity response. As a
result, the APS neutron porosity measurement in carbonates with unknown
or variable dolomitization is the closest
to true formation porosity.
The high-quality HNGS measurements
of natural radioactivity, together with
the APS formation sigma, improve
evaluation of micaceous sands.
IPL tool string.
Rough hole conditions
Using the APS epithermal array
detectors to correct for tool standoff
improves results in rugose hole
sections.
High-salinity fluids
APS epithermal neutron detection
and borehole shielding minimize the
effects of formation and borehole
fluids that have high salinities. When
conventional neutron porosity tools are
used, these effects are much greater
and are dependent on lithology, invasion characteristics and hydrocarbon
saturation.
HNGS sonde
Thorium, uranium and
potassium concentrations
Difficult hole conditions
Since its neutron porosity measurements do not require a radioactive
source, the APS sonde can be used in
wells with difficult borehole conditions where tool sticking might be a
problem.
APS sonde
Epithermal neutron porosities
IPL Hardware Specifications
Hardware
HNGS sonde
APS sonde
IPL cartridge
Litho-Density sonde
Length
(ft)
8.5
13
8
11
Weight
(lbm)
Diameter
(in.)
Temperature
(°F)
Pressure
(psi)
203
222
128
292
3 3⁄4
500
350
350
350
25,000
20,000
20,000
20,000
3 5⁄ 8
3 3⁄ 8
4 7⁄16
Epithermal neutron
slowing time
Invaded formation sigma
Detector standoff
IPL Logging Specifications
Logging Mode
Sampling Rate
(in.)
Logging Speed
(ft/hr)
Standard
High speed
High resolution
Density
Neutron porosity
Natural gamma ray spectroscopy
6
6
1800
3600
1
2
6
900
IPL cartridge
Raw data spectral and
time distribution transmitted
to surface
Improved log quality control
IPL General Specifications
Specifications†
APS measurement
Near-to-array epithermal porosity
Litho-Density measurements
Bulk density
Photoelectric factor
HNGS measurements
Thorium
Uranium
Potassium
†8-in.
Range
Accuracy
0–7 p.u.
7–30 p.u.
30–60 p.u.
±0.5 p.u.
±7%
±10%
2.0–3.0
1–6
g/cm3
borehole filled with fresh water, with no tool standoff, at standard pressure and temperature conditions
Litho-Density sonde
±0.01 g/cm3
Compensated bulk density
±10%
Photoelectric factor
±2%
±2%
±5%
Borehole diameter
Quicklook lithology evaluation
In the lower shale section (A), the
APS porosity and bulk density curves
display shale separation in a conventional manner, although the separation
is less than half that of CNL* Compensated Neutron Log porosity and bulk
density curves.
The ability of the APS sonde to measure total formation hydrogen index
greatly simplified this quicklook lithology evaluation in a 12-in. borehole,
which had been drilled through a shaly
sand formation using 11.1-lbm/gal mud
weighted with small amounts of barite.
Above X240 ft, the cuttings analysis
describes the formation as sandstone
with a varying amount of shaliness.
Both gamma ray and Pe measurements
show this potential bed as shaly, yet
the IPL neutron-density separation is
larger than the separation in the lower,
cleaner sands, indicating a gas effect.
This quicklook lithology evaluation demonstrates the ability of the IPL tool combination
to improve lithology and porosity evaluation and gas detection in shaly sands.
X150
X200
X250
(A)
X300
10
Caliper
(in.)
1:240 ft
APS Array Porosity
20
45
(p.u.)
–15
15
45
CNL Thermal Neutron Porosity
(p.u.)
–15
Total Formation Gamma Ray
0
(GAPI)
Bulk Density
Standoff
–1
(in.)
9
(g/cm3)
1.95
Photoelectric Factor
0
(in.)
2.95
Density Correction
10 – 0.25
Gas
(g/cm3)
0.25
Gas detection in thin, shaly sands
sand more clearly than either the
gamma ray or spontaneous potential measurements do. The density
measurement, together with the APS
neutron porosity profile, which is
sensitive only to variations in formation hydrogen index, pinpoints tight
In this thinly bedded, shaly sandstone,
the AIT and IPL combination detected
several gas zones that conventional
logging technology would have missed.
The formation sigma measurement
defines the overall extent of the shaly
streaks and a 2-ft gas zone. The AIT
1-ft-resolution resistivity measurement also shows this zone. Formation
matrix density variations make the
CNL porosity profile comparatively
insensitive to the presence of gas in
the formation.
A plug-and-abandon permit was issued after this shale and shaly sand interval was logged with DIL* Dual Induction
Resistivity Log, Litho-Density and CNL tools. A subsequent evaluation of the same interval with an AIT and IPL
combination pinpointed five gas-bearing intervals that had been overlooked. This was confirmed by formation test
samples, and the well was completed. It is expected to provide a 10-fold return on investment.
X880
Producing gas at
1.6 MMcf/D
X900
Caliper
(in.)
6
AIT 90-in. Resistivity
16
0.2
Uranium-Free Gamma Ray
0
(GAPI)
(mV)
150
0.2
20
1.65
(c.u)
(ohm-m)
20
Bulk Density
Sigma
0
20
DIL Deep Resistivity
Spontaneous Potential
–80
(ohm-m)
(g/cm3)
2.65
CNL Thermal Neutron Porosity
40
60
(p.u)
0
APS Array Porosity
60
(p.u)
0
Gas detection without
a chemical source
The APS sonde uses an electronic
source, not a chemical one, so the APS
neutron-sonic combination is useful
for gas detection in problem holes.
In this shaly sand example, overlaying
the epithermal neutron and sonic
curves reveals a crossover profile in
the gas zones.
Both the APS neutron-density and APS neutron-sonic logs identified all the gas zones in this interval.
The lack of gamma ray contrast, shown in the depth track, indicates very shaly sands.
X650
X700
X750
X800
X850
Bulk Density
1:240 ft
Rxo, Invaded Zone Resistivity
1.7
(g/cm )
60
APS Array Porosity
(p.u.)
2.7 Formation 0.2
Gamma
Ray
0
0.2
0
150
(GAPI)
Rt, Formation Resistivity
(ohm-m)
3
Gas
(ohm-m)
Compressional ∆t
20 220
(µs/ft)
70
20 60
APS Array Porosity
(p.u.)
0
Gas
www.connect.slb.com
SMP-5167
©Schlumberger
August 2002
*Mark of Schlumberger