ESTIMATION OF RESERVOIR PERMEABILITY
BACKGROUND OF THE INVENTION
The embodiments disclosed herein relate generally to estimation of permeability, and
more particularly to estimation of permeability of a petroliferous reservoir.
Permeability is the facility with which a rock can conduct fluids and is usually
measured in darcies or millidarcies. One darcy represents the permeability of a 1
centimeter thick rock sample that allows a cubic centimeter of fluid of viscosity unit
centipoise to pass through an area of a square centimeter in a second under a
differential pressure of unit atmosphere. A very important associated descriptor is
porosity. Porosity is defined as the fraction of the volume of a rock sample which
represents void space within the rock sample. Porosity is typically reported as a
fraction ranging from 0 to 1, or a percentage ranging from 0 percent to 100 percent.
The rock present in a petroliferous reservoir may be considered as composed of solid
grains with open volumes or pores between the grains. The number of pores, their
relative sizes and positions are factors which determine the porosity of the rock and
also the permeability of the rock. It may be advantageous to measure or to estimate
both the permeability and the porosity of the rock phase of an oil reservoir as a means
of predicting with greater certainty the overall production potential of an oil reservoir.
This knowledge is also valuable in projecting the behavior of the reservoir when it is
subjected to enhanced recovery techniques with a two-phase displacement of the oil in
the reservoir by water injection. In addition, the production characteristics of an oil
reservoir may be affected by a number of factors in addition to porosity and
permeability, for example; pressure and characteristics such as relative permeability
to water, oil, and gas; reservoir dimensions, reservoir water saturation, capillary
pressure and capillary pressure functions.
It is well known that the permeability and porosity characteristics of the petroliferous
zones within an oil field are not necessarily constant across the field. For example,
the permeability of constituent petroliferous zones comprising a given oil field may
vary by several orders of magnitude over the field. Simple models at times are unable
to produce useful information about field performance because the permeability and
porosity characteristics of the petroliferous zones may not remain homogeneous
across the field or portion of the field being modeled.
For example, consider the Saudi Arabian Ghawar oil field. The Ghawar oil field is
the world's largest conventional oil field. It was discovered in 1948 and production
began in 1951. At its peak, the field produced 5.7 million barrels a day. The
variation in porosity and average permeability of the oil field at different locations
over a range of about 10 miles is known in the art. The average porosity known for
the field appears to vary in a range of from about 14 percent to about 19 percent and
the average permeability appears to vary in a range of from about 52 milliDarcies to
about 639 milliDarcies. The Haradh portion of the field is known as having an
average porosity of 14 percent and an average permeability of 52 milliDarcies. The
Hawiyah portion of the field is known as having an average porosity of 17 percent
and an average permeability of 68 milliDarcies. The Uthmaniyah portion of the field
is known as having an average porosity of 18 percent and average permeability of 220
milliDarcies. The Ain Dar portion of the field is known as having an average porosity
of 19 percent and an average permeability 617 milliDarcies. The Shedgum portion of
the field is known as having an average porosity of 19 percent and an average
permeability of 639 milliDarcies.
Direct measurement of the permeability and porosity of core samples removed from a
petroliferous reservoir may be made and such data can be of value. Sometimes,
however, such core samples are not available and, even when available, uncertainties
remain with respect to how well the core samples represent the properties of reservoir
as a whole, as well as possible changes wrought by the act of coring itself and
subsequent sample handling.
Various methods have been developed to attempt to estimate the permeability of a
petroliferous reservoir. One method for determining the permeability of a
petroliferous reservoir includes using a neutron decay logging procedure. A first
aqueous liquid having a known neutron-capture cross-section is injected into the
petroliferous reservoir until the water saturation of the petroliferous reservoir of
interest is substantially 100 percent. Following the injection of the first aqueous
liquid, a second viscous liquid having a known neutron-capture cross-section which is
different from the neutron-capture cross section of the first aqueous liquid is injected
into the reservoir at a low pressure. After a period of time, the concentration of the
viscous liquid is measured using a neutron decay logging procedure. The injection of
the viscous liquid is repeated using a higher pressure and the concentration of viscous
liquid is again measured. The injection pressure is increased in discrete steps and the
concentration measured for each step until the fracturing pressure of the petroliferous
reservoir is approached. The concentration of the viscous liquid versus injection
pressure is plotted and used to determine the permeability of the petroliferous rock.
However, as described, the procedure is relatively complex, may be time consuming,
and may involve the injection of relatively large volumes of multiple exogenous
liquids into the reservoir.
Another method for estimating reservoir permeability involves a pressure build-up
analysis in which data is collected by measurements of the bottom-hole pressure in a
well that has been shut-in after a productive flow period. While production of the
well is stopped the bottom-hole pressure build-up over time of the well is recorded. A
profile of pressure against time may be created and used together with mathematical
reservoir models to assess the extent and characteristics of the reservoir and the near
well-bore area. As noted, however, to obtain such data, production from the well
must generally be stopped for a significant length of time, which may be undesirable
due to the associated expenses of stopping production from a well.
Another method for estimating reservoir characteristics uses production history
matching process in which parameters of a reservoir model are varied until the model
most closely resembles the past production history of the reservoir. A related method
utilizes matching treating pressures during fracturing treatment. When utilizing these
matching methods, the accuracy of the matching depends, inter alia, on the quality of
the reservoir model and the quality and quantity of pressure and production data.
Once a model has been matched, it may be used to simulate future reservoir behavior.
A disadvantage associated with these methods, however, is that several different
possible structures of a fracture or characteristics of a petroliferous reservoir may
yield the same result. That is, there are many possible solutions, or sets of parameter
values, that can likely produce a possible match unless further constraining
information is obtained.
Another method includes the repeated application of an alternating current magnetic
field to the petroliferous rock adjacent to a borehole. This results in a repetitive
excitation-relaxation process of the nucleons present within an "excitation zone"
adjacent to the borehole. The technique, referred to as paramagnetic logging may be
used in open holes and within cased well bores. In a limited zone relatively close to
the borehole, paramagnetic logging may be used to estimate the amount of oil, the
amount of water, the total fluid volume, the viscosity of oil present, oil saturation and
water saturation factors, permeability, positions of vertical oil and water boundaries
adjacent to the borehole, and the locations of lateral discontinuities of the oil bearing
formation. As noted, however, the technique is sensitive to such parameters in
regions only relatively close to the borehole.
Another method includes in situ analysis of a petroliferous rock containing fluid
within the rock interstices. An excitation device is provided for imparting motion to
the fluid relative to the rock and the magnetic fields created by the relative motion of
the fluid in the rock formation are measured, and the permeability of the rock
formation is estimated. Nuclear magnetic resonance techniques and electron
paramagnetic resonance techniques have also been employed as a means of estimating
the permeability.
Despite the number and variety of techniques currently available, there remains a
need for simple techniques for in situ measurements allowing reliable estimation of
the permeability characteristics of a petroliferous reservoir.
BRIEF DESCRIPTION OF THE INVENTION
In one embodiment, a method for determining the permeability of a petroliferous
reservoir comprises injecting a tagged organic molecule into the reservoir at a first
location, and detecting a signal associated with tagged organic molecule at a second
location in the reservoir, wherein the tagged organic molecule comprises a
radionuclide having a half-life of less than a month.
In another embodiment, a method for determining the permeability of a petroliferous
reservoir comprises injecting a tagged organic molecule into the reservoir at a first
location, and detecting a signal associated with tagged organic molecule at a second
location in the reservoir, and wherein the tagged organic molecule comprises a
radionuclide selected from the group consisting of iodine-131 and fluorine-18.
In yet another embodiment, a method for determining the permeability of a crude oil
reservoir comprises injecting l-( 1 1I)iodooctadecane into the reservoir at a first
subsurface location as a solution in crude oil, and detecting a signal associated with 1-
(1 1I)iodooctadecane at a second subsurface location in the reservoir.
In still yet another embodiment, a method for determining the permeability of a crude
oil reservoir comprises injecting l-( 1 F)fluoroctadecane into the reservoir at a first
subsurface location as a solution in crude oil, and detecting a signal associated with 1-
(1 F)fluoroctadecane at a second subsurface location in the reservoir.
Technical effects of the invention include a simplified and robust method of the
estimation of the permeability of a petroliferous reservoir using in situ measurements
of reservoir characteristics related to reservoir permeability and reservoir production
potential. The method provided by the present invention has as an important salutary
feature, the use of relatively minute amounts of a tagged organic molecule comprising
a radionuclide having a relatively short half-life (less than a month) thereby
eliminating long-term contamination of the petroliferous reservoir. The method
further provides flexibility and is adaptable for use in the estimation of permeability
and other characteristics in a wide variety of petroliferous reservoir types. This
disclosure provides selected examples of suitable tagged organic molecules for use in
the practice of the present invention, but one skilled in the art and having the benefit
of this disclosure, will appreciate that a very wide variety tagged organic molecules
comprising a radionuclide having a half-life of less than a month may be employed
according to the method provided by the present invention.
This written description uses examples to disclose the invention, including the best
mode, and also to enable any person skilled in the art to practice the invention,
including making and using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the claims, and may
include other examples that occur to those skilled in the art. Such other examples are
intended to be within the scope of the claims if they have structural elements that do
not differ from the literal language of the claims, or if they include equivalent
structural elements with insubstantial differences from the literal language of the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects, and advantages of the present invention will
become better understood when the following detailed description is read with
reference to the accompanying drawings in which like characters represent like parts
throughout the drawings, wherein:
FIG. 1 is a diagrammatical representation of an oil field with a plurality of boreholes;
and
FIG. 2 is a diagrammatical representation of a method of estimating permeability in
accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
One or more specific embodiments of the present invention are described herein. In
an effort to provide a concise description of these embodiments, all features of an
actual implementation may not be described in the specification. It should be
appreciated that in the development of any such actual implementation, as in any
engineering or design project, numerous implementation-specific decisions must be
made to achieve the developers' specific goals, such as compliance with systemrelated
and business-related constraints, which may vary from one implementation to
another. Moreover, it should be appreciated that such a development effort might be
complex and time consuming, but would nevertheless be a routine undertaking of
design, fabrication, and manufacture for those of ordinary skill having the benefit of
this disclosure.
When introducing elements of various embodiments of the present invention, the
articles "a", "an" and "the" are intended to mean that there are one or more of the
elements present. The terms "comprising," "including," and "having" are intended to
be inclusive and mean that there may be additional elements other than the listed
elements. Any examples of operating parameters and/or environmental conditions
given are not intended to be exclusive of other parameters/conditions in descriptions
of the disclosed embodiments.
As used herein, the phrase "tagged organic molecule" refers to an organic molecule
comprising one or more radionuclides, and embraces both low molecular weight
molecules and high molecular weight organic molecules.
Embodiments of the invention described herein address the noted shortcomings of
state of the art methods for estimation of characteristics related to permeability in
petroliferous reservoirs. In particular, the method of the present invention provides
improved flexibility for ascertaining in situ characteristics related to permeability and
porosity of a petroliferous reservoir. In one embodiment, these in situ measurements
may be made at various locations within a borehole, for example, a production
borehole or a sensing borehole. In one embodiment, the tagged organic molecule is
injected into a petroliferous reservoir from one location in a borehole and thereafter, a
signal associated with the tagged organic molecule within the petroliferous reservoir
is detected at a second location in the borehole. The time which elapses between the
injection of the tagged organic molecule and the detection of a signal associated with
said tagged organic molecule, the magnitude and nature of the detected signal may be
used severally or collectively to estimate one or more permeability characteristics of
the petroliferous reservoir. It is believed that the present invention offers
opportunities for greater reliability and cost savings relative to methods known in the
art in estimating characteristics related to reservoir permeability.
As noted, in one embodiment, a method for determining the permeability of a
petroliferous reservoir comprises injecting a tagged organic molecule into the
reservoir at a first location; and detecting a signal associated with tagged organic
molecule at a second location in the reservoir; wherein the tagged organic molecule
comprises a radionuclide having a half-life of less than a month. In one embodiment,
the petroliferous reservoir may be a marine subsurface rock formation beneath the sea
floor. In an alternate embodiment, the petroliferous reservoir may be a "dry-land"
subsurface rock formation.
In various embodiments the tagged organic molecule comprises a radionuclide having
a half-life of less than a month. Suitable radionuclides include iodine 131, bromine
82, fluorine 18, carbon 11, and nitrogen 13 each of which radionuclides has a half-life
of less than 1 month. In an alternate embodiment, the tagged organic molecule
comprises a radionuclide having a half-life of less than 1 week. In yet another
embodiment, the tagged organic molecule comprises a radionuclide having a half-life
of less than 1 day. In yet still another embodiment, the tagged organic molecule
comprises a radionuclide selected from the group consisting of iodine 131 and
fluorine 18.
In one embodiment, the tagged organic molecule comprises l-( 1 1I)iodooctadecane.
Those of ordinary skill in the art will appreciate that tagged organic molecules such as
l-( 1 1I)iodooctadecane may be prepared using standard radiochemical synthetic
methodology such as by reaction 1-octadecanol tosylate with readily available sodium
or potassium (131)iodide in a polar solvent such as acetonitrile at a temperature in a
range from about ambient temperature to the reflux temperature of the solvent under
ambient conditions. Similarly, acetone may be used as the reaction solvent. Catalysts
such as crown ethers may be included in the reaction mixture to accelerate the rate of
conversion of the starting tosylate to the product tagged organic molecule comprising
iodine 131. The reaction may be carried out using a molar excess of the starting
tosylate in order to convert the maximum amount of the starting iodide into the
product. Following the reaction the product tagged organic molecule may be
separated from any residual inorganic iodide by for example, passage down a column
of silica gel. For the purposes of the present invention, it is generally unnecessary to
separate any remaining tosylate from the product since in general the presence of this
starting material in the sample of the tagged organic molecule injected into the
reservoir is not anticipated to interfere with the either the injection step, the detection
step or the movement of the tagged organic molecule within the reservoir.
In another embodiment, the tagged molecule may comprise l-( 1 F)fluoroctadecane.
Those of ordinary skill in the art will appreciate that l-( 1 F)fluoroctadecane may be
prepared in a manner analogous to the preparation of l-( 1 1I)iodooctadecane except
that a source of (1 F)fluoride is employed instead of sodium or potassium (1 1I)iodide.
Commercial sources of (1 F)fluoride are widely available and techniques for carrying
out a nucleophilic substitution reaction SN2 using commercially available
(1 F)fluoride are well known. Following the reaction the product tagged organic
molecule comprising (1 F)fluorine may be separated from any residual inorganic
fluoride by for example, passage down a column of silica gel or other expedient used
for such purposes and known in the art.
As noted, the method of the present invention includes detection of a signal associated
with the tagged organic molecule at a second location within the reservoir. Thus, the
tagged organic molecule is injected into the reservoir at a first location and traverses a
portion of the reservoir under the influence of an applied force, for example pressure
in the form a pressurized liquid or gas which forces the tagged organic molecule into
the reservoir. In one embodiment, the tagged organic molecule is injected into the
reservoir and thereafter is eluted with a solvent thereby distributing the tagged organic
molecule as a moving front within the reservoir. A detector located at a second
location within the reservoir detects a signal associated with the tagged organic
molecule as the moving front approaches the location of the detector. Those of
ordinary skill in the art will appreciate that the time to the onset of detection at the
second location and the magnitude of the applied force may together be used to assess
the permeability characteristics of the reservoir.
In one embodiment, the signal associated with tagged organic molecule detected at a
second location in the reservoir is a gamma ray. In an alternate embodiment, the
signal associated with tagged organic molecule detected at a second location in the
reservoir is a beta particle. In yet another embodiment, the signal associated with
tagged organic molecule detected at a second location in the reservoir is a photon
arising from a positron annihilation event.
The amount of tagged organic molecule need only be sufficient to be detected at the
second location within the reservoir and the actual mass of tagged organic molecule
injected is anticipated to be on the order of less than a milligram. In one embodiment,
the amount of tagged organic molecule injected into the reservoir corresponds to less
than about 200 milliCuries of radioactivity. In another embodiment, the tagged
organic molecule corresponds to less than about 180 milliCuries of radioactivity. In
yet another embodiment, the tagged organic molecule corresponds to less than about
150 milliCuries of radioactivity.
In one embodiment, the method comprises injecting a tagged organic molecule into
the reservoir at a first location as a solution in contact with a surface of the reservoir
and applying a force to the solution to drive it into the reservoir at the first location.
In various embodiments, the solution comprising the tagged organic molecule may
comprise the tagged organic molecule and a solvent that is compatible with the tagged
organic molecule. In one embodiment, the solvent is such that the tagged organic
molecule dissolves completely in the solvent and forms a homogenous solution. In
another embodiment, the solvent may function as a carrier and the tagged organic
molecule may be finely dispersed in the solvent. In certain other embodiments, the
solvent is a neutral solvent that does not react with the tagged organic molecule.
Suitable examples of solvents include hydrocarbon solvents such as decane,
hexadecane, octadecane, crude oil, and refined oil; ethers such as diphenyl ether,
anisole, 4-hexylanisole, ethylene glycol dimethyl ether, and ethers of polyethylene
glycol; and esters such as ethyl acetate, methyl benzoate, and butyrolactone. The
solvent may be selected such that it provides for both ease and safety of handling and
does not result in undue contamination of the reservoir.
The amount of solvent employed may vary with parameters such as the distance
between the second location at which a signal associated with tagged organic
molecule is detected and the first location, the permeability of the reservoir between
these locations, and the presence of inhomogeneities such as fissures and channels in
the region of the reservoir in which the measurements are conducted. In one
embodiment, the quantity of the solvent employed is in a range of about 10 milliliters
to about 1000 liters. In another embodiment, the quantity of the solvent employed is
in a range of about 100 milliliters to about 100 liters. In yet another embodiment, the
quantity of the solvent employed is in a range of about 1 liter units to about 10 liters.
FIG. 1 illustrates an oil field with N+l boreholes 100. In one aspect, the method of
the present invention may be used to determine whether or not a minimum pore throat
radius exists in the petroliferous reservoir between the well hole serving as the
injection point A 110 and the sampling wells Wl, W2, ..., WN 1201-120N.
The particular pore throat size characteristics of a reservoir may be probed by varying
the size and structure of the tagged organic molecule employed and injected into the
reservoir injection point A 110 and measuring the transport times and efficiencies
associated with the migration of the tagged organic molecule from the first location
within the reservoir to positions within the reservoir where signals associated with the
tagged organic molecule may be detected at second locations within the reservoir for
examples sampling wells Wl, W2, WN 1201-120N. If the size and structure of
the tagged organic molecule exceed the capability of the pores within the reservoir to
allow migration of the tagged organic molecule, the particular pore throat size
distribution of the reservoir can be estimated from the size of the particular tagged
organic molecule at which the onset of the inhibition of migration is observed. Where
a particular tagged organic molecule is not able to migrate from the first location to a
point within the reservoir wherein a signal associated with the tagged organic
molecule may be detected at the second location, and tagged organic molecules of
smaller dimensions have successfully so migrated, then it may be concluded that the
pore throat radius in the region between the injection point A 110 and the particular
sampling well is smaller than the non-migrating tagged organic molecule.
The structure of the tagged organic molecule used to probe reservoir pore throat size
distributions may be highly varied and techniques for producing both branched
variants of tagged organic molecules such as l-( 1 1I)iodooctadecane are well known
to the art. In addition, it is possible to prepare oligomeric and polymeric tagged
organic molecules having almost any size. For example, polystyrene comprising
either iodine 131 or bromine 82 are known in the art and those of ordinary skill in the
art may employ art recognized techniques to produce a wide variety of low and high
molecular weight polystyrenes having highly varied dimensions. As noted, at least
one of the tagged organic molecules tested should be easily detectable at the sampling
wells Wl, W2, WN 1201-120N. Again, it is emphasized that because the probe
molecules (the tagged organic molecules) comprise one or more radionuclides,
vanishingly small amounts of tagged organic molecule may be employed and the thus
the technique is not expected to negatively affect the later production characteristics
of the reservoir.
Referring to FIG. 2, a diagrammatical representation 200 of a method of estimating
permeability in accordance with an embodiment of the present invention is provided.
As shown in the figure, a well hole 210 has a drill bit assembly 212 that comprises an
effusion port 214. A transportation tube 216 is lowered though the well hole 210.
The transportation tube 216 connects the effusion port 214 on a surface portion 218 of
the well hole 210 to a detection port 220 located within a distance inside the well hole
210 in the path of the drill bit assembly 212. A solution comprising a permeability
estimating tagged organic molecule 222 is introduced into the transportation tube 216
at the effusion port 214 upon a command conveyed from the surface by a wide variety
of means including electrical, optical, acoustic, seismic, or magnetic means. As used
herein the "effusion port" 214 is a place where the tagged organic molecule is injected
and the "detection port" 220 is the place where the tagged organic molecule is
detected. The solution 222 may be forced out of the detection port 220 by applying a
pressure using a device (not shown in figure). The solution 222 then travels the path
from the effusion port 214 to the detection port 220. A radiation detector 224 may be
positioned near the detection port 220 in the path of the drill bit assembly 212, such
that the radiation detector 224 is capable of detecting a signal associated with the
tagged organic molecule present in the solution 222. The radiation detector 224 is
connected to an analytical equipment (not shown in figure) via a conductor 226.
Under the applied force the tagged organic molecule arrives at locations in the
reservoir where signals associated with the tagged organic molecule can be detected at
the detection port 220. The time between injection and detection and the applied
force are noted and may be used to estimate the permeability of the reservoir.
In FIG. 2 the effusion port 214 is depicted as above the detection port 220. The
relative positions of the ports may be reversed without affecting the method. The
separation between the effusion port 214 and the detection port 220 equipped with the
radiation detector 224 may be measured in feet. In one embodiment, the distance
between the effusion port and the detection port is of the order of ten feet. In another
embodiment the distance between the effusion port and the detection port is of the
order of one hundred feet. In various embodiments, the distance between the effusion
port and the detection port is of the order of ten feet and may range from a few feet to
several hundred feet. In one embodiment, the tagged organic molecule is introduced
into the reservoir through the effusion port 214 from a chamber located within the
drill stem and may be released upon a command from the surface. In Fig. 2 the
radiation detector is linked to the surface via the conductor 226 for reporting
purposes. The data collected at the detector may be conveyed to the surface by a wide
variety of means including electrical, optical, acoustic, seismic, or magnetic means
In certain embodiments, the solution 222 may comprise plurality of tagged organic
molecules having different molecular dimensions. In certain embodiments, the tagged
organic molecules may be differentiated by the identity of the radionuclide present in
the different tagged organic molecules, for example a mixture comprising a first
tagged organic molecule comprising fluorine- 18 and having a first molecular size and
a second tagged organic molecule comprising iodine-131 and having a second larger
molecular size. The detector 224 employed may distinguish between signals
associated with the first tagged organic molecule and signals associated with the
second tagged organic molecule thereby allowing single test pore size estimation
tests. For example, where the first tagged organic molecule is detected and the second
tagged organic molecule is not detected it may be concluded that the diameter of the
pore throat of the petroliferous reservoir in the area between the effusion port 214 and
the detection port 220 is less than the dimensions of the second tagged organic
molecule.
While only certain features of the invention have been illustrated and described
herein, many modifications and changes will occur to those skilled in the art. It is,
therefore, to be understood that the appended claims are intended to cover all such
modifications and changes as fall within the true spirit of the invention.

WHAT IS CLAIMED IS:
1. A method for determining the permeability of a petroliferous reservoir
comprising:
injecting a tagged organic molecule into the reservoir at a first location; and
detecting a signal associated with tagged organic molecule at a second location in the
reservoir;
wherein the tagged organic molecule comprises a radionuclide having a half-life of
less than a month.
2 . The method of claim 1, comprising injecting a tagged organic molecule into
the reservoir at a first location as a solution in contact with a surface of the reservoir
and applying a force to the solution to drive it into the reservoir at the first location.
3 . The method of claim 1, wherein the tagged organic molecule comprises 1-
(1 1I)iodooctadecane.
4 . The method of claim 1, wherein the tagged organic molecule comprises 1-
(1 F)fluoroctadecane.
5 . The method of claim 1, wherein said detecting comprises the detection of a
gamma ray.
6 . The method of claim 1, wherein said detecting comprises the detection of a
beta particle.
7 . The method of claim 1, wherein said detecting comprises the detection of a
photon arising from a positron annihilation event.
8 . The method of claim 1, wherein the half-life is less than 1 week.
9 . The method of claim 1, wherein the half-life is less than 1 day.
10. The method of claim 1, wherein the tagged organic molecule corresponds to a
less than about 200 milliCuries of radioactivity providing a means for detecting the
tagged molecule; wherein the means for detecting the tagged molecule is located in
the reservoir.
11. A method for determining the permeability of a petroliferous reservoir
comprising:
injecting a tagged organic molecule into the reservoir at a first location; and
detecting a signal associated with tagged organic molecule at a second location in the
reservoir;
wherein the tagged organic molecule comprises a radionuclide selected from the
group consisting of iodine 131 and fluorine 18.
12. The method of claim 11, comprising injecting a tagged organic molecule into
the reservoir at a first location as a solution in contact with a surface of the reservoir
and applying a force to the solution to drive it into the reservoir at the first location.
13. The method of claim 11, wherein the tagged organic molecule comprises 1-
(1 1I)iodooctadecane.
14. The method of claim 11, wherein the tagged organic molecule comprises 1-
(1 F)fluoroctadecane.
15. The method of claim 11, wherein said detecting comprises the detection of a
gamma ray.
16. The method of claim 11, wherein said detecting comprises the detection of a
beta particle.
17. The method of claim 11, wherein said detecting comprises the detection of a
photon arising from a positron annihilation event.
18. A method for determining the permeability of a crude oil reservoir
comprising:
injecting l-( 1 1I)iodooctadecane into the reservoir at a first subsurface location as a
solution in crude oil, and
detecting a signal associated with l-( 1 1I)iodooctadecane at a second subsurface
location in the reservoir.
19. A method for determining the permeability of a crude oil reservoir
comprising:
injecting l-( 1 F)fluoroctadecane into the reservoir at a first subsurface location as a
solution in crude oil, and
detecting a signal associated with l-( 1 F)fluoroctadecane at a second subsurface
location in the reservoir.