Radiant energy – Geological testing or irradiation – With sampling
Reexamination Certificate
1998-12-29
2001-08-07
Hannaher, Constantine (Department: 2878)
Radiant energy
Geological testing or irradiation
With sampling
C250S461100, C250S459100
Reexamination Certificate
active
06271518
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to the exploration for and exploitation of formation hydrocarbons.
This invention finds its application in analytical laboratories and on the drilling sites of petroleum production fields.
2. Prior Art
Drilling operations for the exploration for hydrocarbons in underground formations are long and expensive.
One means for reducing the duration and cost of these operations is to optimize the detection of the formation hydrocarbons in all drilling conditions.
This optimization consists in recognizing all the impregnated rocks and in directing the test programme so as to accurately define the zones to be tested.
Document EP 0,344,950 describes a method for determining the amount of hydrocarbons present in an underground formation, which consists in carrying out the following steps:
taking a rock sample,
extracting the hydrocarbons contained in a known amount of the rock sample, using a known amount of a solvent,
exciting the extract obtained with ultra-violet radiation of a wavelength at which most of the hydrocarbon mixtures are fluorescent, this wavelength being between 250 and 310 nanometers,
recording, using a fluorimeter, the radiation emitted by the extract at a given wavelength,
determining the amount of fluorescent elements present in the rock sample by comparing the intensity of the radiation recorded with the radiation emitted at the same wavelength by samples of materials containing known amounts of hydrocarbons.
Since the rock sample is impregnated with both the formation hydrocarbons and the fluorescent elements which form part of the composition of the drilling mud, the results obtained by this method are inaccurate. Furthermore, they give no information regarding the nature of the fluorescent elements detected, most particularly in the case of oily muds.
DESCRIPTION OF THE INVENTION
The aim of the present invention is, precisely, to overcome these drawbacks and to provide a process for detecting and characterizing formation hydrocarbons.
This process can be used in the laboratory and on the drilling sites of petroleum production fields.
To this end, the present invention proposes a process for detecting and characterizing formation hydrocarbons which consists in carrying out the following steps:
taking a sample of material which is representative of the rocks passed through during a drilling operation,
taking a determined amount of material to be analysed from the said sample of material,
extracting the hydrocarbons contained in the said amount of material to be analysed, using a known amount of a solvent for hydrocarbons, in order to make up an initial extract,
characterized in that it also consists in carrying out the following operations:
diluting the initial extract by a factor d in order to obtain a final extract,
exciting the final extract with ultraviolet radiation of a wavelength chosen within the band substantially between 250 and 400 nanometers,
recording, in a wavelength band L, an emission spectrum resulting from the excitation of the final extract,
calculating the emission flux of the sample of material by applying the following formula:
FLUX
=
d
*
∑
i
=
1
n
I
(
λ
i
)
in which
FLUX represents the emission flux of the sample of material
I(&lgr;i) represents the intensity of the radiation emitted at a wavelength &lgr;i of the band L by the final extract,
n represents the number of wavelengths of the emission spectrum sampled at a pitch of between 1 and 20 nanometers, and is equal to L divided by the pitch,
i ranges from 1 to n,
the value of the emission flux of the sample of material is proportional to the concentration of fluorescent elements in the sample of material, including, in particular, the formation hydrocarbons,
calculating the fluorescence quotient of the sample of material using the following formula:
FQ=
area
A
/area
B
in which:
FQ represents the fluorescence quotient of the sample of material,
area A and area B are calculated, respectively, by the following formulae:
Area
A
=
∑
i
=
x
+
1
n
I
(
λ
i
)
Area
B
=
∑
i
=
1
x
I
(
λ
i
)
in which:
I(&lgr;i) and n are defined as above,
x is an integer between 1 and n,
the value of the fluorescence quotient of the sample of material is representative of the nature of the hydrocarbons contained in the sample of material.
According to another characteristic of the process of the invention, the solvent for hydrocarbons is preferably cyclohexane.
According to another characteristic of the process of the invention, the wavelength band L is preferably substantially between 280 and 500 nanometers.
According to another characteristic of the process of the invention, the value x corresponds to the reference point of a wavelength &lgr;x substantially equal to 367 nanometers, which is representative of the cutoff between the spectra emitted, on the one hand, by the monoaromatic and biaromatic hydrocarbons and by a portion of the triaromatic hydrocarbons, and, on the other hand, by the polyaromatic hydrocarbons.
According to another characteristic of the process of the invention, a low value of the fluorescence quotient of the sample of material indicates the presence of light hydrocarbons in the said sample and a high value indicates the presence of heavy hydrocarbons.
According to another characteristic, the process of the invention consists in taking a series of samples of material at different depths during the drilling, in determining the fluorescence quotient and the emission flux of each sample, and then in plotting the curves representing the said fluorescence quotient and the said emission flux as a function of the depths, of the variations of the fluorescence quotient and of the emission flux, thus making it possible, respectively, to characterize the nature of the fluorescent elements and to assess the degree of concentration of the said elements in the series of samples of material.
According to another characteristic, the process of the invention consists in comparing the fluorescence quotient of at least one sample of material with the fluorescence quotient of at least one sample of reference product determined in the same way as the fluorescence quotient of the sample of material.
According to another characteristic of the process of the invention, since the drilling is carried out with an injection of mud, the sample of reference product consists of a sample of mud taken during the drilling.
According to another characteristic of the process of the invention, a fluorescence quotient value for a sample of material which is close to the value of the fluorescence quotient for the sample of mud taken during the drilling indicates the absence of formation hydrocarbons in the sample of material, and a different value indicates a presence, if, furthermore, the value of the emission flux for the sample of material is high.
REFERENCES:
patent: 4609821 (1986-09-01), Summers
patent: 4783416 (1988-11-01), Patel
patent: 4814614 (1989-03-01), Tsui
patent: 4865746 (1989-09-01), Overfield
patent: 4959549 (1990-09-01), Haub et al.
patent: 4988446 (1991-01-01), Haberman et al.
patent: 5076909 (1991-12-01), Overfield et al.
Berrut Jean-Bernard
Boehm Claudine
Blank Rome Comisky & McCauley LLP
Elf Exploration Production
Hannaher Constantine
Israel Andrew
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