Compositional modeling and pyrolysis data analysis methods

• US 20070162264A1
• Filed: 05/07/2004
• Published: 07/12/2007
• Est. Priority Date: 05/07/2003
• Status: Active Grant

• Current Assignee: Saudi Arabian Oil Company (Government of Saudi Arabia)
• Original Assignee: Saudi Arabian Oil Company (Government of Saudi Arabia)
• Inventors: Jones, Peter, Halpern, Henry
• Granted Patent: US 7,363,206 B2
• Time in Patent Office: Days
• US Class Current: 703/2
• CPC Class Codes: G01N 33/241 for hydrocarbon content drilling mud G01N33/2823; drilling per se E21B; prospecting G01V

Abstract

Methods for processing pyrolytic characterizing data (pcd) from reservoir rock samples obtained from known geographical locations under circumstances that are encountered during the drilling of wells provide information that is important for assessing the relative amounts of various hydrocarbon and organic matter types found in the reservoir and for characterizing the reservoir quality and preparing compositional modeling data, and include the steps of comparing the pcd for known end-member components typically found in the geographical location with the pcd derived from test samples and applying mathematical analyses to identify the predicted composition and quantitative measure of end-members. The method is applied to model hydrocarbon moveability, reservoir injectivity; contaminants and soil an aquifer pollutants.

Claims

1. A method of identifying the relative proportions by percent of a plurality of end member components in a sample of reservoir rock taken from a specific oil field by analysis of pyrolytic characterizing data (pcd), the method comprising the steps of:

a. identifying the end-member components known to be present in reservoir rock in the oil field;

b. preparing individual pyrograms consisting of pcd for each of the components identified in step (a);

c. storing the pcd for each component in a digital data file;

d. conducting a pyrolytic analysis of a sample from the oil field of reservoir rock that contains one or more hydrocarbon and organic matter components of the type identified in step (a) to obtain pcd for the sample;

e. comparing the pcd for the sample with the pcd obtained in step (b) for each of the components, measuring and recording the difference between the sample pcd and the pcd for each of the components;

f. applying a statistical analysis to minimize the aggregate differences between the pcd for the sample and a combination of pcd selected from the components;

g. recording for retention and display for analysis the resulting pcd that constitutes the minimum aggregate error over the temperature range of the pyrolytic analysis; and

h. analyzing the displayed data to identify the respective components.

2. The method of claim 1, wherein the pyrolytic analysis is conducted over a temperature range of from about 180°

C. to about 700°

C.

3. The method of claim 2, wherein the pcd is comprised of a predetermined number of data points based on temperature, and the pcd of the sample and each of the plurality of end member components is compared at each data point.

4. The method of claim 3, wherein at least a portion of the data points are at intervals of one degree Centigrade or less.

5. The method of claim 1, wherein the pcd in step (g) is recorded in a form for visual analysis selected from the group consisting of pyrogram displays and tabular data.

6. The method of claim 1, wherein the analytical method is selected from the group consisting of the method of least squares and root mean squares.

7. The method of claim 3, wherein there are 611 data points and the method includes the further steps of converting the pcd to hydrocarbon yield per gram of sample, gRock, at each data point by applying a conversion factor, CF, the conversion factor being calculated for the 611 data points as follows:

${\mathrm{CF}}_{\mathrm{FID}}=\frac{\left[\sum <br><br>{\mathrm{Signal}}_{\mathrm{step}<br><br>\text{\hspace{1em}<br><br>}<br><br>1-611}<br><br>\left(\mathrm{mV}\right)\right]}{\left[\left(\mathrm{LV}+\mathrm{TD}+\mathrm{TC}\right)<br><br>\left(\mathrm{mg}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{HC}/g<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Rock}\right)\right]}$

where mV is millivolts and the other terms of the equation are as defmed above; and

recording the conversion factor in a data file.

8. The method of claim 7 which further comprises determining for a predetermined data point X, the yield, Yield_X in accordance with the following:

Yield_x(mgHC/gRock)=[Signal_STEPX(mV)]/[CF_FID(mV/mg HC/gRock)]

9. The method of claim 8 which includes the step of normalizing the pcd for each selected end member component, EM, for comparison to the pcd of the rock sample as a pure component at a data point X, the normalized yield being calculated as follows:

$\mathrm{Yield}={\mathrm{Yield}}_{\mathrm{EMX}}\times <br><br>\frac{\mathrm{Total}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Yield}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{THC}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Sample}}{\mathrm{Total}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Yield}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Component}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{EM}}$

where Yield_EMX is the yield of the selected end member at data point X; and

recording the results of each calculation in a data file.

10. The method of claim 1, wherein the number of end member components is five.

11. The method of claim 1 in which steps (d)-(h) are repeated for a plurality of samples taken from different known positions in a selected section of the reservoir formation.

12. The method of claim 11 in which the data from step (g) for each sample is plotted to display variation in composition in the section selected.

13. The method of claim 12, wherein the data from step (g) for each sample is plotted to display for analysis the relative contribution of each component by depth and each curve is adjusted for relative yield in total hydrocarbon.

14. A method of adjusting the quantitative contribution of a first minor end member component, EM1, in a component set containing y end members, where y is from 3 to 5 components, the method comprising the steps of:

a. selecting a second end member component EMy-1;

b. determining the yield of EM1 and selecting a percentage Z % of EM1, Z %_EM1, by which EM1 is to be reduced;

c. applying the following calculation for each one of a plurality of data points X;

Adjusted Yield_EMy-1(x)=Yield_EMy-1−

Z %_EM1 x Yield_Em1(x)×

THC_EMy-1100 THC_EM1

d. applying the adjusted yield for component EM2 to each of the data points to recalculate a resultant pcd of the component and recording the results; and

e. comparing the resultant pcd to the pcd of the sample to provide the best fit of the data.

15. A method for identifying the presence of drilling mud contaminants in reservoir rock samples recovered from a well bore during drilling of the well, where the rock samples are subjected to pyrolytic analysis, the method comprising the steps of:

a. providing a plurality of samples of reservoir rock removed from spaced-apart adjacent locations along the well bore;

b. subjecting the rock samples to pyrolytic analysis to obtain pcd consisting of a plurality of data points for each of the plurality of samples obtained in step (a);

c. adjusting the pcd so that all samples have the same total yield of hydrocarbons;

d. subtracting the pcd for a first sample having apparent contamination multiplied by the ratio of

$\frac{{\mathrm{THC}}_{\mathrm{smp}}<br><br>X}{{\mathrm{THC}}_{\mathrm{smp}}<br><br>X+1}$

 

from the pcd of a second adjacent sample having greater apparent corresponding contamination at the plurality of data points; and

e. recording for analysis a new adjusted contamination pcd based upon step (d).

16. The method of claim 15 which includes the further step of converting the adjusted contamination pcd of step (d) to have a yield of 10 mgHC/gRock.

17. The method of claim 15 which includes the further step of displaying for analysis a graphical plot of the contamination curves of pcd for pairs of adjacent rock samples and the resultant apparent contamination pcd obtained in step (d).

18. The method of claim 15 which further comprises the step of averaging the output of step (d) over at least one additional pcd obtained from other reservoir rock samples that are compared for contamination.

19. A method for correcting pcd for the hydrocarbon staining of a reservoir rock sample to account for one or more end member components and background material that does not constitute indigenous hydrocarbon staining, the method comprising the steps of:

a. providing a sample of drilled reservoir rock removed from a known location;

b. obtaining pcd for the sample;

c. calculating the HC yield for the sample from the pcd;

d. subtracting interfering components that are contaminants for each data point comprising the pcd to provide a corrected pcd;

e. recalculating the pyrolytic parameters LV, TD, TC and T_min based on the corrected pcd;

f. recalculating API gravity, POPI, POPI_norm and Apparent Water Saturation based upon the recalculated parameters obtained in step (e); and

g. recording for retention and analysis the results of the calculations of step (f).

20. The method of claim 19, wherein the corrected yield, Yield_corr, at a given data point X is calculated to remove the effects of interfering components EM₁ and EM₂ as follows:

Yield_corr=Yield_STEPX−

((% EM₁/100)*Yield_EM1,X*(THC_sample/THC_EM1))+(% EM₂/100)*Yield_EM2,X*(THC_sample/THC_EM2))

21. The method of claim 19 which includes the further steps of graphically displaying for analysis the pyrogram curves corresponding to (a) the pcd of the reservoir rock sample, (b) the pcd of the interfering components and (c) the corrected pcd.

22. A method for directly assessing moved hydrocarbons in a reservoir rock sample removed from a well drilled using drilling mud, said drilling mud formed from a plurality of additives, the method comprising the steps of:

a. providing a sample of drilled reservoir rock removed from a known location in the well bore;

b. obtaining pcd from one or more of the plurality of drilling mud additives for a predetermined quantity of the sample obtained in step (a);

c. comparing the pcd of the one or more of the plurality of additives produced in step (b) with pre-existing pcd of the one or more of the drilling mud additives; and

d. recording for retention and comparative analysis the respective pcd values.

23. A method of optimizing the placement of horizontal power water injector wells in an oil field containing tar mats, the method comprising the steps of:

a. obtain a plurality of samples of reservoir rock from the oil field;

b. analyze each of the plurality of samples by pyrolysis;

c. perform compositional modeling based on one or more end members known to be present in the field;

d. correct the pyrolysis parameters for background or dispersed organic matter;

e. assess the values for POPI_Norm and AS_w in terms of relative position in the oil-water transition zone;

f. plot the results for the original and the corrected pyrolysis data;

g. plot the compositional modeling data;

h. determine whether the results of step (g) are consistent with the then-current well path directional drilling plan;

i. adjust the drilling program, as necessary, to optimize the well path location; and

j. repeat steps (a) through (i).

24. A method for optimizing the placement of horizontal production wells through reservoir rock in an oil field, the method comprising the steps of:

a. obtain a plurality of the samples of reservoir rock from the oil field;

b. analyze each of the plurality of samples by pyrolysis;

c. perform compositional modeling, based on one or more end members known to be present in the field;

d. correct the pyrolysis parameters for background or dispersed organic matter;

e. assess the data to determine whether the pyrolytic characteristics for a sample from a known location are consistent with productive oil reservoir rock;

f. plot the results for the original and the corrected pyrolysis data;

g. plot the compositional modeling data;

h. determine whether the results of step (g) are consistent with the then-current well path directional drilling plan;

i. adjust the drilling program, as necessary, to optimize the well path location and continue to monitor; and

j. repeat steps (a) through (i).

25. A method of identifying the relative proportions by percent of a plurality of hydrocarbon pollutant end-member components in one or more soil or aquifer samples taken from a selected geographical region by analysis of pyrolytic characterizing data (pcd), the method comprising the steps of:

a. identifying the pollutant end-member components known or believed to be present in the soil or aquifer in the geographical region;

b. preparing individual pyrograms consisting of pcd for each of the pollutant components identified in step (a);

c. storing the pcd for each component in a digital data file;

d. conducting a pyrolytic analysis of a sample from the geographical region that contains one or more hydrocarbon and organic matter components of the type identified in step (a) to obtain pcd for the sample;

e. comparing the pcd for the sample with the pcd obtained in step (b) for each of the pollutant components, measuring and recording the difference between the sample pcd and the pcd for each of the components;

f. applying a statistical analysis to minimize the aggregate differences between the pcd for the sample and a combination of pcd selected from the components;

g. recording for retention and analysis the resulting pcd that constitutes the minimum aggregate error over the temperature range of the pyrolytic analysis; and

h. identifying any one or more pollutant end members from the pcd.

26. The method of claim 25 which includes the further steps of providing one or more additional soil or aquifer samples from different locations, including different strata in the geographical region;

and repeating steps (d) through (h) on each of the additional samples.

27. The method of claim 25 which includes the further steps of:

i. providing one or more additional soil or aquifer samples from the same geographical region that are known or believed to be free of pollutants;

J. identifying any indigenous non-pollutant end-member components that are found in the soil of aquifer samples of step (i);

k. preparing invididual pyrograms consisting of the pcd for each of the any non-pollutant components found in step (j);

l. comparing the pcd for the non-pollutant end-member components obtained in step (k) components;

m. combining the pcd for the non-pollutant components with the pcd obtained in step (b); and

n. repeating steps (e) through (h).

28. A method for identifying the presence of hydrocarbon pollutants in soil or aquifer samples from a specific geographic region, where the samples are subjected to pyrolytic analysis, the method comprising the steps of:

a. providing a plurality of soil or aquifer samples removed from spaced-apart adjacent locations in the geographic region;

b. subjecting the rock samples to pyrolytic analysis to obtain pcd consisting of a plurality of data points for each of the plurality of samples obtained in step (a);

c. adjusting the pcd so that all samples have the same total yield of hydrocarbons;

d. subtracting the pcd for a first sample having apparent pollution multiplied by the ratio of

$\frac{{\mathrm{THC}}_{\mathrm{smp}}<br><br>X}{{\mathrm{THC}}_{\mathrm{smp}}<br><br>X+1}$

 

from the pcd of a second adjacent sample having greater apparent pollution at the plurality of data points;

e. recording for retention and analysis a new adjusted pollution pcd based upon step (d); and

f. identifying the nature and extent of the hydrocarbon pollutants in the geographical region from which the samples were removed.