U.S. patent application number 14/259846 was filed with the patent office on 2014-10-30 for relative permeability from borehole resistivity measurements.
This patent application is currently assigned to SCHLUMBERGER TECHNOLOGY CORPORATION. The applicant listed for this patent is SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to FABRICE PAIROYS.
Application Number | 20140318232 14/259846 |
Document ID | / |
Family ID | 51788093 |
Filed Date | 2014-10-30 |
United States Patent
Application |
20140318232 |
Kind Code |
A1 |
PAIROYS; FABRICE |
October 30, 2014 |
RELATIVE PERMEABILITY FROM BOREHOLE RESISTIVITY MEASUREMENTS
Abstract
Methods for deriving relative permeability from resistivity
measurements in the laboratory and from downhole resistivity
measurements are described. Further, systems and methods for
determining relative permeability from borehole resistivity
measurements made during a water flooding event such as drilling
with water-based mud, water injection and/or water invasion are
described.
Inventors: |
PAIROYS; FABRICE; (HOUSTON,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHLUMBERGER TECHNOLOGY CORPORATION |
Sugar Land |
TX |
US |
|
|
Assignee: |
SCHLUMBERGER TECHNOLOGY
CORPORATION
Sugar Land
TX
|
Family ID: |
51788093 |
Appl. No.: |
14/259846 |
Filed: |
April 23, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61824854 |
May 17, 2013 |
|
|
|
61817160 |
Apr 29, 2013 |
|
|
|
Current U.S.
Class: |
73/152.05 ;
324/323 |
Current CPC
Class: |
G01V 3/24 20130101; G01V
1/50 20130101; G01V 2210/624 20130101; E21B 49/00 20130101; G01V
3/32 20130101 |
Class at
Publication: |
73/152.05 ;
324/323 |
International
Class: |
E21B 49/00 20060101
E21B049/00; E21B 49/02 20060101 E21B049/02 |
Claims
1. A method for determining relative permeability for a
subterranean rock formation comprising: receiving downhole
resistivity data representative of resistivity measurements made in
a wellbore penetrating the subterranean rock formation during a
water flooding event of the subterranean rock formation; and
determining one or more relative permeability values for the
subterranean rock formation based at least in part on the downhole
resistivity data.
2. A method according to claim 1, wherein the one or more
permeability values include relative permeability for wetting and
non-wetting phases during an imbibition mode corresponding to the
water flooding event.
3. A method according to claim 2, wherein the wetting phase is an
aqueous fluid and the non-wetting phase is an oil fluid.
4. A method according to claim 3, wherein said resistivity
measurements are made by a logging-while-drilling tool, the aqueous
wetting phase is a water-based drilling mud and said water flooding
event is introduction of said water-based drilling mud into the
rock formation during a drilling process.
5. A method according to claim 1, wherein the water flooding event
is caused by water being injected from an injection well.
6. A method according to claim 5, wherein said resistivity
measurements are made from said injection well.
7. A method according to claim 1, wherein the water flooding event
is caused by a brine invasion from a second rock formation.
8. A method according to claim 1, wherein said resistivity
measurements are made from a production well configured to produce
fluid from the rock formation.
9. A method according to claim 1, wherein said resistivity
measurements are made from an observer well.
10. A method according to claim 1, wherein said determining one or
more relative permeability values are further based on one or more
values for porosity of the rock formation.
11. A method according to claim 10, wherein said one or more values
for porosity are based at least in part on borehole
measurements.
12. A method according to claim 11, wherein the borehole
measurements upon which the one or more values for porosity are
based are selected from a group consisting of: neutron density
measurements, NMR measurements, dielectric measurements, and
acoustic measurements.
13. A method according to claim 1, wherein said determining one or
more relative permeability values are further based on one or more
derived Archie's law parameters.
14. A method according to claim 13, wherein said one or more
derived Archie's law parameters are selected from a group
consisting of: saturation exponent and cementation factor.
15. A method according to claim 13, wherein said one or more
derived Archie's law parameters are based at least in part on a
laboratory core analysis procedure.
16. A method according to claim 13, wherein said one or more
derived Archie's law parameters are based at least in part on
borehole measurements.
17. A method according to claim 16, wherein said borehole
measurements on which said one or more Archie's law parameters is
based at least in part are made using a borehole dielectric
measurement tool.
18. A system for determining relative permeability for a
subterranean rock formation comprising: a downhole resistivity
measurement tool configured to be deployed in a borehole
penetrating the rock formation and take resistivity measurements
during a water flooding event of the rock formation; and a
processing system configured to determine one or more relative
permeability values for the subterranean rock formation based at
least in part on downhole measurements made during the water
flooding event made by said resistivity tool.
19. A system according to claim 18, wherein the one or more
permeability values include relative permeability for a wetting
aqueous fluid phase and a non-wetting oil fluid phase during an
imbibition mode corresponding to the water flooding event.
20. A system according to claim 19, wherein said downhole
resistivity tool is a logging-while-drilling tool, the aqueous
wetting phase is a water-based drilling mud and said water flooding
event is an introduction of said water-based drilling mud into the
rock formation during a drilling process.
21. A system according to claim 19, wherein the water flooding
event is due to a cause selected from a group consisting of: water
being injected from an injection well, and a brine invasion from a
second rock formation.
22. A system according to claim 21, wherein said downhole
resistivity tool is permanently or semi permanently resistivity
sensor mounted in a well type selected from a group consisting of:
injection well, observer well and production well.
23. A system according to claim 18, wherein said one or more
relative permeability values determined by said processing system
are further based on one or more values for porosity of the rock
formation.
24. A system according to claim 23, wherein said one or more values
for porosity are based at least in part on borehole measurements
selected from a group consisting of: neutron density measurements,
NMR measurements, dielectric measurements, and acoustic
measurements.
25. A system according to claim 18, wherein said one or more
relative permeability values determined by said processing system
are further based on one or more derived Archie's law
parameters.
26. A system according to claim 25, wherein said one or more
derived Archie's law parameters are based at least in part on a
laboratory core analysis procedure.
27. A system according to claim 25, wherein said one or more
derived Archie's law parameters are based at least in part on
borehole measurements.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims the benefit of U.S.
Provisional Patent Application Ser. No. 61/824,854, filed May 17,
2013, entitled "Methods for deriving relative permeability from
resistivity measurements;" and U.S. Provisional Patent Application
Ser. No. 61/817,160, filed Apr. 29, 2013, entitled "Correlation
between resistivity and petrophysical parameters of a carbonate
rock during two-phase flow displacements;" both of which are
incorporated herein by reference in their entireties.
FIELD
[0002] The subject disclosure generally relates to production of
oil and gas from subterranean reservoirs. More particularly, the
subject disclosure relates to methods for deriving relative
permeability from borehole resistivity measurements.
BACKGROUND
[0003] In formation evaluation and reservoir engineering,
resistivity index, relative permeability, and capillary pressure
are often valuable parameters for estimating oil reserves and
planning for production. They can be determined in the laboratory
using conventional and Special Core Analysis, or SCAL
techniques.
[0004] Several theoretical models have been proposed to infer
relative permeability from capillary pressure. A few studies have
been initiated to correlate relative permeability and/or capillary
pressure with resistivity. For example, Pirson et al., found an
empirical relationship between relative permeability and
resistivity index (Pirson et al., "Prediction of relative
permeability characteristics of intergranular reservoir rocks from
electrical measurements," J. Petrol. Technol., (1964), 561-570). Li
et al., (Li, K. and Horne, R. N. "Experimental Verification of
Methods to Calculate Relative Permeability Using Capillary Pressure
Data," SPE 76757, Proceedings of the 2002 SPE Western Region
Meeting/AAPG Pacific Section Joint Meeting, Anchorage, Ak., May
20-22, 2002; Li, K., "A Semi-analytical Method to Calculate
Relative Permeability from Resistivity Well Logs," SPE 95575, SPE
Annual Technical Conference and Exhibition, Dallas, USA, 9-12 Oct.
2005; and Li, K., "A New Method for Calculating Two-Phase Relative
Permeability from Resistivity Data in Porous Media," Transport in
Porous Media (2007), DOI 10.1007/s11242-007-9178-4) has developed a
semi-analytical model to infer relative permeability from
resistivity, and confirmed it using experimental data. All of the
above references are incorporated herein by reference in their
entirety.
SUMMARY
[0005] This summary is provided to introduce a selection of
concepts that are further described below in the detailed
description. This summary is not intended to identify key or
essential features of the claimed subject matter, nor is it
intended to be used as an aid in limiting the scope of the claimed
subject matter.
[0006] According to some embodiments a method is described for
determining relative permeability for a subterranean rock
formation. The method includes: receiving downhole resistivity data
representative of resistivity measurements made in a wellbore
penetrating the subterranean rock formation during a water flooding
event of the subterranean rock formation; and determining one or
more relative permeability values for the subterranean rock
formation based at least in part on the downhole resistivity data.
According to some embodiments, the permeability values include
relative permeability for wetting (e.g., water) and non-wetting
(e.g., oil) phases during an imbibition mode corresponding to the
water flooding event.
[0007] According to some embodiments, the resistivity measurements
are made using a logging-while-drilling tool. In such cases the
aqueous wetting phase can be a water-based drilling mud and the
water flooding event can be the introduction of the water-based
drilling mud into the rock formation during a drilling process.
[0008] According to some embodiments, the water flooding event is
caused by water being injected from an injection well. The
resistivity measurements can be made from an injection well, an
observer well and/or a production well. According to some other
embodiments, the water flooding event is caused by a brine invasion
from a second rock formation.
[0009] According to some embodiments, the relative permeability
values are further based on porosity values of the rock formation.
The porosity can be derived from, for example borehole measurements
such as neutron density measurements, NMR measurements, dielectric
measurements, and/or acoustic measurements.
[0010] According to some embodiments, the relative permeability
values are further based on one or more derived Archie's law
parameters, such as saturation exponent and/or cementation factor.
The Archie's law parameters can be based on a laboratory core
analysis procedure, and/or on borehole measurements.
[0011] According to some embodiments, a system is described for
determining relative permeability for a subterranean rock
formation. The system includes: a downhole resistivity measurement
tool configured to be deployed in a borehole penetrating the rock
formation and to take resistivity measurements during a water
flooding event of the rock formation; and a processing system
configured to determine one or more relative permeability values
for the subterranean rock formation, based at least in part on
downhole measurements made during the water flooding event made by
the resistivity tool.
[0012] As used herein the term "determining" is to be broadly
construed and includes like terms such as deriving, calculating,
modeling, obtaining, acquiring, estimating and extracting.
[0013] As used herein the term "water" includes aqueous fluids such
as brine and water-based drilling mud.
[0014] Further features and advantages of the subject disclosure
will become more readily apparent from the following detailed
description when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The subject disclosure is further described in the detailed
description which follows, in reference to the noted plurality of
drawings by way of non-limiting examples of the subject disclosure,
in which like reference numerals represent similar parts throughout
the several views of the drawings, and wherein:
[0016] FIG. 1 is a flow chart illustrating aspects of determining
relative permeability from drainage-phase laboratory measurements,
according to some embodiments;
[0017] FIGS. 2-1, 2-2 and 2-3 depict the experimental results in
primary drainage, according to some embodiments;
[0018] FIG. 3 is a flow chart illustrating aspects of a method for
determining relative permeability for imbibition following a
drainage-phase from laboratory measurements, according to some
embodiments;
[0019] FIGS. 4-1, 4-2 and 4-3 depict the experimental results in
imbibition, according to some embodiments;
[0020] FIG. 5 is a flow chart illustrating aspects of a method for
determining relative permeability on a log scale based on downhole
resistivity measurements, according to some embodiments;
[0021] FIG. 6 is a diagram illustrating aspects of systems and
methods for determining relative permeability from borehole
resistivity measurements, according to some embodiments; and
[0022] FIG. 7 illustrates a wellsite system in which the relative
permeability can be determined from resistivity and other
measurements taken while drilling with a water-based mud, according
to some embodiments.
DETAILED DESCRIPTION
[0023] The particulars shown herein are by way of example and for
purposes of illustrative discussion of the examples of the subject
disclosure only, and are presented in the cause of providing what
is believed to be the most useful and readily understood
description of the principles and conceptual aspects of the subject
disclosure. In this regard, no attempt is made to show structural
details in more detail than is necessary, the description taken
with the drawings making apparent to those skilled in the art how
the several forms of the subject disclosure may be embodied in
practice. Furthermore, like reference numbers and designations in
the various drawings indicate like elements.
[0024] According to some embodiments, methods are disclosed for
predicting relative permeability from resistivity measured in the
lab using a steady-state method and from direct measurements in the
well (i.e., downhole resistivity measurements). The steady-state
flooding method measures resistivity and steady-state relative
permeability at the equilibrium state.
[0025] According to some other embodiments, methods are disclosed
to modify and improve Li's model in primary drainage. According to
some embodiments, the pore size distribution index .lamda. in Li's
model is substituted by the saturation exponent n in the equation
of the relative permeability of the wetting phase. This
substitution can be justified by the fact that, when brine is the
wetting phase, as is the case in water-wet conditions, the mobility
of the wetting brine phase is highly affected by the capillary
forces, whereas the mobility of the non-wetting oil phase is more
governed by the viscous forces. The saturation exponent n accounts
for this in the mobility of the wetting phase. According to some
embodiments, for the non-wetting phase which will be less affected
by the capillary effects (no capillary suction due to the water
wettability of the rock), the factor .lamda. is retained in the
model.
[0026] According to some embodiments, methods are disclosed for
determining Kr during an imbibition cycle. Experiments performed
have shown good agreement between Kr determined from resistivity
and Kr measured in the lab using the steady-state method during an
imbibition cycle. The imbibition methods described are believed to
more accurately describe what happens in the wellbore during brine
invasion (water-based mud while drilling or brine while injecting).
According to some embodiments, the above modeling methods for
drainage and imbibition are used to determine relative permeability
in a reservoir rock using borehole resistivity measurements made in
the reservoir rock.
[0027] FIG. 1 is a flow chart illustrating aspects of determining
relative permeability from drainage-phase laboratory measurements,
according to some embodiments. More particularly, the described
method is for determining relative permeability from resistivity
measured on water-wet core plugs during a drainage steady-state
experiment. In block 110, conventional core analysis is used to
determine porosity and absolute permeability. In block 112,
steady-state experiments are conducted with resistivity
measurements carried out at equilibrium. In block 114, a
resistivity index (RI) curve is plotted to determine the saturation
exponent (n).
[0028] In block 116, the equivalence between Equations 1 and 2
below are used to determine .lamda..
Krw = Sw * 1 RI ( Equation 1 ) Krw = ( Sw * ) ( 2 + .lamda. ) /
.lamda. ( Equation 2 ) Sw * = Sw - Swi 1 - Swi ( Equation 3 )
##EQU00001##
[0029] In block 118, Krw (relative permeability to the wetting
phase or to water) and Kro (relative permeability to oil) are
calculated using Equations 4 and 5 below.
Krw=(Sw).sup.(2+n)/n (Equation 4)
Krnw=(1-Sw*).sup.2[1-(Sw*).sup.(2+.lamda.)/.lamda.] (Equation
5)
[0030] In block 120, the Kr curves are un-normalized. The curve
intervals will be Swi<Sw<1 for the X-axis, 0<Krw<1 and
0<Kro<Kro(Swi) for the Y-axis. At the end of the drainage
steady-state experiment, Ko(Swi) is known.
[0031] The model using Equations 4 and 5 was validated in the lab
on a water-wet rock. In general, for primary drainage, rocks are
assumed to be water-wet because they are cleaned before starting
the SCAL experiments at Sw=1 (water saturation).
[0032] FIGS. 2-1, 2-2 and 2-3 depict the experimental results in
primary drainage, according to some embodiments. FIG. 2-1 depicts
the steady-state Kr (relative permeability) with curve 210 showing
Krw (water) and curve 212 showing Kro (oil). FIG. 2-2 depicts the
RI (resistivity index) curve 220 as plotted according to block 114
in FIG. 1. FIG. 2-3 depicts the comparison between experimental
steady state (SS) Kr (curves 230 and 232), Kr from Li's model
(curves 240 and 242), and Kr from the methods in primary drainage
shown in FIG. 1 (curve 250), according to some embodiments. As can
be seen by comparing curves 230, 240 and 250, a significant
improvement over Li's model is obtained using the model described,
according to some embodiments.
[0033] FIG. 3 is a flow chart illustrating aspects of a method for
determining relative permeability for imbibition following a
drainage-phase from laboratory measurements, according to some
embodiments. More particularly, the method shown in FIG. 3 is for
the imbibition steady-state cycle, following a primary drainage, to
determine relative permeability from resistivity. In block 310, in
continuity with the primary drainage, a steady-state experiment is
run with resistivity measurements taken at equilibrium. In block
312, the RI (resistivity) curve is plotted to determine n
(saturation exponent).
[0034] In block 314, the equivalence between Equation 6 and 7 below
is used to determine .lamda..
Krw = Sw * RI * ( Equation 6 ) Krw = ( Sw * ) ( 2 + .lamda. ) /
.lamda. ( Equation 7 ) RI * = RI RI min ( Equation 8 ) Sw * = Sw -
Swi 1 - Swi - Sor ( Equation 9 ) ##EQU00002##
[0035] In block 316, Krw (relative permeability to the wetting
phase or to water) and Kro (relative permeability to oil) are
calculated using the equations below, and Kr (relative
permeability) is plotted on a normalized curve.
Krw=(Sw*).sup.(2+.lamda.)/.lamda. (Equation 10)
Krnw=(1-Sw*).sup.2[1-(Sw*).sup.(2+.lamda.)/.lamda.] (Equation
11)
[0036] The Kr curves are un-normalized. Curve intervals will be
Swi<Sw<Sor (Swi is irreducible water saturation, Sw is the
water saturation and Sor is oil saturation resistivity) for the
X-axis, 0<Kr0<1 (Ko(Swi) is used to normalize imbibition Kr)
and 0<Krw<Krw(Sor) (Krw is the relative permeability to the
wetting phase or to water) for the Y-axis. At the end of the
imbibition steady-state experiment, Kw(Sor) is known.
[0037] FIGS. 4-1, 4-2 and 4-3 depict the experimental results in
imbibition, according to some embodiments. FIG. 4-1 depicts the
steady state Krw (curve 410) and Kro (curve 412) for the
imbibition. FIG. 4-2 depicts the RI curve 420. FIG. 4-3 depicts the
comparison between experimental steady-state (SS) Krw (curve 430)
and Kro (curve 432), and Kr from the model for imbibition mode
described in FIG. 3, supra. As can be seen, an acceptable match is
obtained for both wetting and non-wetting phase relative
permeability values.
[0038] FIG. 5 is a flow chart illustrating aspects of a method for
determining relative permeability on a log scale based on downhole
resistivity measurements, according to some embodiments. For oil
reservoirs, the imbibition model can be used since the reservoir is
at Swi (irreducible water saturation). In block 510, porosity is
determined from neutron-density or other logging techniques.
Examples include NMR or dielectric logging tools. In block 512, Rt
(resistivity) is determined from an electrical log during a brine
invasion or a water injection process. In block 514, m and n (or
other suitable Archie's law parameters) are determined from core
analysis or from other logging techniques. In block 516, Sw (water
saturation) is determined from the second Archie's law. In block
518, .lamda. is determined using the equivalence between Equation
11 above and Equation 12 below:
Krw = Sw * RI * ( Equation 12 ) Krw = ( Sw * ) ( 2 + .lamda. ) /
.lamda. ( Equation 13 ) RI * = RI RI min ( Equation 14 ) Sw * = Sw
- Swi 1 - Swi - Sor ( Equation 15 ) ##EQU00003##
[0039] RI.sub.min is the resistivity index at the end of the water
flooding (end of imbibition or Sor) when the resistivity reaches
its minimal and constant value.
[0040] In block 520, Krw and Kro are calculated using Equation 16
and 17 below, and Kr is plotted on a normalized curve.
Krw=(Sw*).sup.(2+.lamda.)/.lamda. (Equation 16)
Krnw=(1-Sw*).sup.2[1-(Sw*).sup.(2+.lamda.)/.lamda.] (Equation
17)
Note that .lamda. is not substituted by n in Krw since it is an
imbibition cycle, and not a drainage cycle.
[0041] In block 522, the Kr curve is un-normalized by determining
the Kr end-points using resistivity and formation-tester
measurements (See Zeybek, M., Ramakrishnan, T. S., Al-Otaibi, S.
S., Salamy, S. P., Kuchuk, F. J., "Estimating Multiphase-Flow
Properties from Dual-Packer Formation-Tester Interval Tests and
Openhole Array Resistivity Measurements," SPE Reservoir Eval. Eng.,
40-46, February 2004, which is incorporated by reference
herein).
[0042] FIG. 6 is a diagram illustrating aspects of systems and
methods for determining relative permeability from borehole
resistivity measurements, according to some embodiments. An
injection well 610 is used to inject water into a formation 600,
which is for example a hydrocarbon bearing rock formation. On the
surface of injection well 610, wellsite 612 includes pumping and
monitoring equipment for both injecting water and other fluid which
can be stored in tank 614. Also located at wellsite 612, according
to some embodiments, is surface data monitoring unit 616 that is in
communication with a permanently or semi-permanently installed
resistivity measuring unit 624. The water injected is via well 610
at a packer-isolated injection zone 618.
[0043] The fluid produced from reservoir 600 is collected by one or
more producer wells, for example well producer well 630. According
to some embodiments, the resistivity in producer well 630 is
monitored by either a permanent (or semi-permanent) resistivity
measuring unit 628 or, according to some embodiments, a downhole
resistivity tool 636 is deployed via wireline 634 and wireline
truck 632. According to some other embodiments, wireline tool 636
is used to retrieve stored data from permanent resistivity
measurement unit 628. According to yet other embodiments,
resistivity measurements are obtained using a permanent or
semi-permanent measurement unit 626 that is positioned in an
observer well 620. The data from unit 626 is transmitted to surface
station 622. Using an observer well, according to some embodiments,
is useful in some applications since it is less likely to be
effected by "end effects" and so can provide an improved
representation of the resistivity changes during the water
injection event.
[0044] According to some embodiments, the resistivity data from
units 624, 626, 628 and/or tool 636 are transmitted to a data
processing unit 650. The processing unit includes a storage system
642, communications and input/output modules 640, a user display
646 and a user input system 648. According to some embodiments, the
processing unit 650 may be located in the logging truck 632, or at
another wellsite location, such as at wellsite 612 or within
surface station 622. Data processing unit 650 carries out the
calculations that facilitate the determinations of relative
permeability, such as described with respect to some or all of
FIGS. 1, 3 and 5 described supra.
[0045] According to some embodiments, the resistivity measurements
from units 624, 626, 628 and/or tool 636 are taken during a water
(e.g., brine) invasion event rather than a water injection
procedure.
[0046] FIG. 7 illustrates a wellsite system in which the relative
permeability can be determined from resistivity and other
measurements taken while drilling with a water-based mud, according
to some embodiments. The wellsite can be onshore or offshore. In
this system, a borehole 711 is formed in subsurface formations by
rotary drilling in a manner that is well known. Embodiments of the
invention can also use directional drilling, as will be described
hereinafter.
[0047] A drill string 712 is suspended within the borehole 711 and
has a bottom hole assembly 700 that includes a drill bit 705 at its
lower end. The surface system includes platform and derrick
assembly 710 positioned over the borehole 711, the assembly 710
including a rotary table 716, kelly 717, hook 718 and rotary swivel
719. The drill string 712 is rotated by the rotary table 716,
energized by means not shown, which engages the kelly 717 at the
upper end of the drill string. The drill string 712 is suspended
from a hook 718, attached to a traveling block (also not shown),
through the kelly 717 and a rotary swivel 719, which permits
rotation of the drill string relative to the hook. As is well
known, a top drive system could also be used.
[0048] In the example of this embodiment, the surface system
further includes drilling fluid or mud 726, stored in a pit 727
formed at the well site. A pump 729 delivers the drilling fluid 726
to the interior of the drill string 712 via a port in the swivel
719, causing the drilling fluid to flow downwardly through the
drill string 712, as indicated by the directional arrow 708. The
drilling fluid exits the drill string 712 via ports in the drill
bit 705, and then circulates upwardly through the annulus region
between the outside of the drill string and the wall of the
borehole, as indicated by the directional arrows 709. In this
well-known manner, the drilling fluid lubricates the drill bit 705
and carries formation cuttings up to the surface as it is returned
to the pit 727 for recirculation.
[0049] The bottom hole assembly 700 of the illustrated embodiment
contains a logging-while-drilling (LWD) module 720, a
measuring-while-drilling (MWD) module 730, a roto-steerable system
and motor, and drill bit 705.
[0050] The LWD module 720 is housed in a special type of drill
collar, as is known in the art, and can contain one or a plurality
of known types of logging tools. It will also be understood that
more than one LWD and/or MWD module can be employed, e.g., as
represented at 720A. (References, throughout, to a module at the
position of 720 can alternatively mean a module at the position of
720A as well.) The LWD module includes capabilities for measuring,
processing, and storing information, as well as for communicating
with the surface equipment. In the present embodiment, the LWD
module includes a resistivity measuring device as well as a number
of other devices, such as a neutron-density measuring device.
[0051] The MWD module 730 is also housed in a special type of drill
collar, as is known in the art, and can contain one or more devices
for measuring characteristics of the drill string and drill bit.
The MWD tool further includes an apparatus (not shown) for
generating electrical power to the downhole system. This may
typically include a mud turbine generator powered by the flow of
the drilling fluid, it being understood that other power and/or
battery systems may be employed. In the present embodiment, the MWD
module includes one or more of the following types of measuring
devices: a weight-on-bit measuring device, a torque measuring
device, a vibration measuring device, a shock measuring device, a
stick slip measuring device, a direction measuring device, and an
inclination measuring device.
[0052] According to some embodiments, the resistivity data 760 and
other data such as neutron density data, is transmitted to data
processing unit 650, which can be located a the wellsite or in some
remote location. According to some embodiments, measurements made
during the water invasion in the form of water-based mud from the
drilling process is used to determine relative permeability as
described herein (e.g., with respect to FIG. 5, supra).
[0053] In view of the above description it will be appreciated that
features of the subject disclosure may be implemented in computer
programs stored on a computer readable medium and run by
processors, application specific integrated circuits and other
hardware. Moreover, the computer programs and hardware may be
distributed across devices including but not limited to tooling
which is inserted into the borehole and equipment which is located
at the surface, whether onsite or elsewhere.
[0054] Although only a few examples have been described in detail
above, those skilled in the art will readily appreciate that many
modifications are possible in the examples without materially
departing from this subject disclosure. Accordingly, all such
modifications are intended to be included within the scope of this
disclosure as defined in the following claims. In the claims,
means-plus-function clauses are intended to cover the structures
described herein as performing the recited function and not only
structural equivalents, but also equivalent structures. Thus,
although a nail and a screw may not be structural equivalents in
that a nail employs a cylindrical surface to secure wooden parts
together, whereas a screw employs a helical surface, in the
environment of fastening wooden parts, a nail and a screw may be
equivalent structures. It is the express intention of the applicant
not to invoke 35 U.S.C. .sctn.112, paragraph 6 for any limitations
of any of the claims herein, except for those in which the claim
expressly uses the words `means for` together with an associated
function.
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