Pyrolytic oil-productivity index method for characterizing reservoir rock
First Claim
1. An improved method employing data derived from the pyrolytic analysis of reservoir rock from an oil field for predicting the oil-production characteristics of said reservoir rock within the range of oil-productive rock, marginally oil-productive rock and tar-occluded or non-reservoir rock, which method comprises the steps of:
- (a) collecting a sample of rock from a known depth and location in the field;
(b) preparing said sample for pyrolytic analysis;
(c) obtaining the values for LV, TD, and TC resulting from the pyrolytic analysis of said prepared sample;
(d) calculating the value of the pyrolytic oil productivity index, POPI, for the sample in accordance with the following equation;
space="preserve" listing-type="equation">POPI ln(LV+TD+TC)×
(TI)--TC);
where n is a natural logarithm, LV is the weight in milligrams of hydrocarbon released per gram of rock at the static temperature condition of 180 degrees Celsius prior to the programmed pyrolysis of the sample, TD is the weight in milligrams of hydrocarbon released per gram of rock at a temperature between 180 degrees Celsius and Tmin degrees Celsius, TC is the weight in milligrams of hydrocarbon released per gram of rock at a temperature between Tmin degrees Celsius and 600 degrees Celsius, and Tmin represents the total weight of hydrocarbons released in that temperature range;
(e) recording the value of POPI and the measured depth for the sample;
(f) collecting a sample of rock from a different location and at a known measured depth in the field;
(g) repeating steps (b)-(f) for a plurality of known sampling locations;
(h) calculating the value of POPIo for a representative sample of crude oil of the type found in good quality reservoir rock in the oil field; and
(i) identifying depths corresponding to POPI values of(i) from 0 to about 1/2POPIo as tar-occluded or nonreservoir rock, or both;
(ii) from about 1/2POPIo, to POPIo, as marginally oil-productive reservoir rock; and
(iii) above about 5.0 as oil-productive reservoir rock.
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Abstract
Data from the pyrolytic analysis of rock samples obtained from drilling operations in an existing oil field are used to characterize the quality and condition of reservoir rock by comparison of the values of an index for the unknown reservoir rock samples with the value of the index for a known type and quality of petroleum reservoir rock sample, the index being denominated Pyrolytic Oil Productivity Index ("POPI") and defined by the expression:
ln(LV+TD+TC)×(TD÷TC)=POPI (I),
where the terms of the equation are determined empirically and the resulting POPI values can be used to direct horizontal drilling operations in real time to optimize the position of the drilling bit in the reservoir.
14 Citations
23 Claims
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1. An improved method employing data derived from the pyrolytic analysis of reservoir rock from an oil field for predicting the oil-production characteristics of said reservoir rock within the range of oil-productive rock, marginally oil-productive rock and tar-occluded or non-reservoir rock, which method comprises the steps of:
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(a) collecting a sample of rock from a known depth and location in the field; (b) preparing said sample for pyrolytic analysis; (c) obtaining the values for LV, TD, and TC resulting from the pyrolytic analysis of said prepared sample; (d) calculating the value of the pyrolytic oil productivity index, POPI, for the sample in accordance with the following equation;
space="preserve" listing-type="equation">POPI ln(LV+TD+TC)×
(TI)--TC);where n is a natural logarithm, LV is the weight in milligrams of hydrocarbon released per gram of rock at the static temperature condition of 180 degrees Celsius prior to the programmed pyrolysis of the sample, TD is the weight in milligrams of hydrocarbon released per gram of rock at a temperature between 180 degrees Celsius and Tmin degrees Celsius, TC is the weight in milligrams of hydrocarbon released per gram of rock at a temperature between Tmin degrees Celsius and 600 degrees Celsius, and Tmin represents the total weight of hydrocarbons released in that temperature range; (e) recording the value of POPI and the measured depth for the sample; (f) collecting a sample of rock from a different location and at a known measured depth in the field; (g) repeating steps (b)-(f) for a plurality of known sampling locations; (h) calculating the value of POPIo for a representative sample of crude oil of the type found in good quality reservoir rock in the oil field; and (i) identifying depths corresponding to POPI values of (i) from 0 to about 1/2POPIo as tar-occluded or nonreservoir rock, or both; (ii) from about 1/2POPIo, to POPIo, as marginally oil-productive reservoir rock; and (iii) above about 5.0 as oil-productive reservoir rock. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for obtaining data derived from the pyrolytic analysis of a sample "A" of reservoir rock collected from a pre-determined position in a reservoir region in order to characterize the reservoir performance as an oil-productive region or a tar-occluded region, the pyrolytic analysis data being the values for LV1A, TD1A and TC1A for the sample, the method comprising the steps of:
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(a) calculating the value of POPIo for a representative sample of crude oil of the type found in good quality reservoir rock in the oil field; (b) recording the location in the reservoir from which the sample A was obtained; (c) obtaining the values for LV1A, TD1A, and TC1A resulting from the pyrolytic analysis of said prepared sample A; (d) calculating the value of the pyrolytic oil productivity index, POPIA, for the sample in the equation
space="preserve" listing-type="equation">POPI.sub.A =ln(LV.sub.1A +TD.sub.1A +TC.sub.1A)×
(TD.sub.1A ÷
TC.sub.1A);
(I)(e) recording the information obtained from either or both of steps (b) and (d), above, for the sample A; (f) comparing the value of POPIA calculated for the sample A to the table of POPIo standards, where POPIA >
POPIo indicates oil-productive rock,POPIA <
1/2POPIo indicates tar-occluded or non-reservoir rock, and1/2POPIo ≧
POPIA ≦
POPIo indicates marginally productive reservoir rock. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method for directing a drill bit of a well-drilling rig during the drilling of a horizontal well to locate the advancing bit in an oil-productive stratum of reservoir rock, the method comprising the steps of:
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(a) calculating the value of POPIo for a representative sample of crude oil of the type found in good quality reservoir rock in the oil field; (b) collecting a first sample "A" of rock from a measured known depth A and location in the field; (c) preparing said sample A for pyrolytic analysis; (d) obtaining the values for LVA, TDA and TCA resulting from the pyrolytic analysis of said prepared sample; (e) calculating the value of the pyrolytic oil productivity index, POPIA, for the sample in accordance with the following equation POPIA =ln(LVA +TDA +TCA)×
(TDA ÷
TCA);(f) horizontally advancing the drill bit if the value of POPIA is greater than or equal to POPIo (g) collecting subsequent samples of rock at depth A and repeating steps (b) through (e), above; (h) vertically displacing the advancing bit to a different known depth B if the value of POPIA for a subsequent sample is less than 1/2POPIo ; (i) repeating steps (a)-(g) above until a value of POPIB for a sample B is 1/2POPIo or greater; (j) advancing the bit at about the same vertical depth from the position at which the sample B producing a POPIB value of 1/2POPIo or greater was taken; and (k) repeating steps (a) through (i), above. - View Dependent Claims (21)
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22. A method for directing a drill bit of a well drilling rig during the drilling of a horizontal well to maintain the advancing bit in an oil productive stratum of reservoir rock, the method comprising the steps of:
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(a) calculating the value of POPIo for a representative sample of crude oil of the type found in good quality reservoir rock in the oil field; (b) collecting a sample A of rock from a measured known depth A and location in the field; (c) preparing said sample A for pyrolytic analysis; (d) obtaining the values for LVA, TDA and TCA resulting from the pyrolytic analysis of said prepared sample A; (e) calculating the value of the pyrolytic oil-productivity index, POPIA, for the sample A in accordance with the following equation
space="preserve" listing-type="equation">POPI.sub.A =ln(LV.sub.A +TD.sub.A +TC.sub.A)×
(TD.sub.A ÷
TC.sub.A);(f) advancing the bit at about the same vertical depth if the value of POPIA is greater than 1/2POPIo ; (g) collecting subsequent samples of rock at depth A and repeating steps (a) through (e), above; (h) repeating the steps (a)-(e) above until a value of the POPIB for a sample is less than 1/2POPIo ; (i) vertically displacing the advancing bit to a different known depth B; (j) repeating steps (a)-(h) above until a value of the POPIB for the sample B is 1/2POPIo or greater; (k) advancing the bit at a vertical depth that is about the same as that from which the sample producing a POPIB value of 1/2POPIo or greater was taken; and (l) repeating steps (a) through (j), above. - View Dependent Claims (23)
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Specification