Method, system and apparatus for black oil delumping

1. A computer executable method for performing black oil delumping, the method comprising:

converting a wellstream in a black oil reservoir simulation into a compositional wellstream enabling reconstitution of a set of composition and component molar rates of a production well;

wherein the delumping method is adapted for retrieving component molar rates n i , i=1 . . . N c , wherein N c is a number of components and wherein a component molar rate is a product of a total molar rate multiplied by a component's mole fraction, and wherein the converting step comprises:

(a) performing a phase mass rate calculation;

(b) performing a phase composition calculation; and

(c) performing a total composition and component molar rates calculation; and

wherein step (a) for performing the phase mass rate calculation includes calculating the phase mass rates of vapor and liquid using the relations:

phase mass rate of vapor, Q m v =Q m gv +Q m ov , and

phase mass rate of liquid, Q m L =Q m oL +Q m gL ,

where Q m gv , Q m ov , Q m oL and Q m gL are mass rates of the free gas, vaporized oil, liquid oil, and dissolved gas respectively.

2. The computer executable method of claim 1 , wherein said mass rates Q m gv , Q m ov , Q m oL and Q m gL are obtained from the following expressions:

Q m gv =ρ g q gv ,

Q m ov =ρ o q ov ,

Q m oL =ρ o q oL , and

Q m gL =ρ g q gL ,

and wherein q gv , q ov , q oL , and q gL denote free gas, vaporized oil, liquid oil, and dissolved gas surface volume rates respectively; and ρ g and ρ o are the surface gas and oil densities, respectively.

3. The computer executable method of claim 2 , wherein step (b) for performing the phase composition calculation comprises:

(b1) performing a phase component mole fraction calculation, including calculating a quantity, said quantity being selected from a group consisting of: a liquid phase gas/oil ratio (R s =q gL /q oL ), and a vapor phase oil/gas ratio (R v =q ov /q gv ), and

using said quantity to obtain values representative of vapor and liquid compositions.

4. The computable executable method of claim 3 , wherein step (c) for performing a total composition and component molar rates calculation comprises:

calculating the total composition where the mole fraction z i , of component i (i=1 . . . N c ) is related to the vapor and liquid component mole fractions y i , and x i , respectively by:

Z i =αy i +(1−α) x i ,

where α is the vapor fraction defined by:

α= n v /( n v +n L ), and

n v , n L are the total number of moles in the vapor and liquid phases respectively.

5. The computer executable method of claim 1 , wherein step (b) for performing the phase composition calculation comprises:

(b1) performing a phase component mole fraction calculation, including calculating a quantity, said quantity being selected from a group consisting of: a liquid mass-rate-averaged saturation pressure, a vapor mass-rate-averaged saturation pressure, a liquid phase gas/oil ratio (R s =q gL /q oL ), and a vapor phase oil/gas ratio (R v =q ov /q gv ), and

using said quantity to obtain values representative of vapor and liquid compositions.

6. The computer executable method of claim 1 , wherein step (c) for performing a total composition and component molar rates calculation comprises:

calculating the total composition where the mole fraction z i , of component i (i=1 . . . N c ) is related to the vapor and liquid component mole fractions y i , and x i , respectively by:

Z i =αy i +(1−α) x i ,

where α is the vapor fraction defined by:

α= n v /( n v +n L ), and

n v , n L are the total number of moles in the vapor and liquid phases respectively.

7. A machine readable storage device embodying a set of machine executable instructions that when executed by a machine perform a method for black oil delumping, said method comprising:

converting a wellstream in a black oil reservoir simulation into a compositional wellstream enabling reconstitution of a set of composition and component molar rates of a production well;

wherein the method for black oil delumping is adapted for retrieving component molar rates n i , i=1 . . . N c , wherein N c is a number of components and wherein a component molar rate is a product of a total molar rate multiplied by a component's mole fraction, the converting step comprising:

(a) performing a phase mass rate calculation;

(b) performing a phase composition calculation; and

(c) performing a total composition and component molar rates calculation;

wherein step (a) for performing the phase mass rate calculation includes calculating the phase mass rates of vapor and liquid using the relations:

phase mass rate of vapor, Q m v =Q m gv +Q m ov , and

phase mass rate of liquid, Q m L =Q m oL +Q m gL ,

where Q m gv , Q m ov , Q m oL and Q m gL are mass rates of the free gas, vaporized oil, liquid oil, and dissolved gas respectively.

8. The machine readable storage device of claim 7 , wherein said mass rates Q m gv , Q m ov , Q m oL and Q m gL are obtained from the following expressions:

Q m gv =ρ g q gv ,

Q m ov =ρ o q ov ,

Q m oL =ρ o q oL , and

Q m gL =ρ g q gL ,

and wherein q gv , q ov , q oL , and q gL free gas, vaporized oil, liquid oil, and dissolved gas surface volume rates respectively; and ρ g and ρ o are the surface gas and oil densities, respectively.

9. The machine readable storage device of claim 8 , wherein step (b) for performing the phase composition calculation comprises:

(b1) performing a phase component mole fraction calculation, including calculating a quantity, said quantity being selected from a group consisting of: a liquid mass-rate-averaged saturation pressure, a vapor mass-rate-averaged saturation pressure, a liquid phase gas/oil ratio (R s =q gL /q oL ), and a vapor phase oil/gas ratio (R v =q ov /q gv ), and

using said quantity to obtain values representative of vapor and liquid compositions.

10. The machine readable storage device of claim 9 , wherein step (c) for performing a total composition and component molar rates calculation comprises:

calculating the total composition where the mole fraction z i , of component i (i=1 . . . N c ) is related to the vapor and liquid component mole fractions y i , and x i , respectively by:

Z i =αy i +(1−α) x i ,

where α is the vapor fraction defined by:

α= n v /( n v +n L ), and

n v , n L are the total number of moles in the vapor and liquid phases respectively.

11. A machine readable storage device embodying a set of machine executable instructions that when executed by a machine perform a method for black oil delumping, said method comprising:

converting a wellstream in a black oil reservoir simulation into a compositional wellstream enabling reconstitution of a set of composition and component molar rates of a production well;

wherein the method for black oil delumping is adapted for retrieving component molar rates n i , i=1 . . . N c , wherein N c is a number of components and wherein a component molar rate is a product of a total molar rate multiplied by a component's mole fraction, the converting step comprising:

(a) performing a phase mass rate calculation;

(b) performing a phase composition calculation; and

(c) performing a total composition and component molar rates calculation;

wherein step (b) for performing the phase composition calculation comprises:

(b1) performing a phase component mole fraction calculation, including calculating a quantity, said quantity being selected from a group consisting of: a liquid mass-rate-averaged saturation pressure, a vapor mass-rate-averaged saturation pressure, a liquid phase gas/oil ratio (R s =q gL /q oL ), and a vapor phase oil/gas ratio (R v =q ov / q gv ), and

using said quantity to obtain values representative of vapor and liquid compositions.

12. A machine readable storage device embodying a set of machine executable instructions that when executed by a machine perform a method for black oil delumping, said method comprising:

converting a wellstream in a black oil reservoir simulation into a compositional wellstream enabling reconstitution of a set of composition and component molar rates of a production well;

wherein the method for black oil delumping is adapted for retrieving component molar rates n i , i=1 . . . N c , wherein N c is a number of components and wherein a component molar rate is a product of a total molar rate multiplied by a component's mole fraction, the converting step comprising:

(a) performing a phase mass rate calculation;

(b) performing a phase composition calculation; and

(c) performing a total composition and component molar rates calculation;

wherein step (c) for performing a total composition and component molar rates calculation comprises:

calculating the total composition where the mole fraction z i , of component i (i=1 . . . N c ) is related to the vapor and liquid component mole fractions y i , and x i , respectively by:

Z i =αy i +(1−α) x i ,

where α is the vapor fraction defined by:

α= n v /(n v +n L ), and

n v , n L are the total number of moles in the vapor and liquid phases respectively.

13. A system for performing black oil delumping, said system comprising:

a computer with at least one processor;

a memory storing a program of instructions for executing a method comprising:

converting a wellstream in a black oil reservoir simulation into a compositional wellstream enabling reconstitution of a set of composition and component molar rates of a production well;

wherein the delumping method is adapted for retrieving component molar rates n i , i=1 . . . N c , wherein N c is a number of components and wherein a component molar rate is a product of a total molar rate multiplied by a component's mole fraction, and wherein the converting step comprises:

(a) performing a phase mass rate calculation;

(b) performing a phase composition calculation; and

(c) performing a total composition and component molar rates calculation; and

wherein step (a) for performing the phase mass rate calculation includes calculating the phase mass rates of vapor and liquid using the relations:

phase mass rate of vapor, Q m v =Q m gv +Q m ov , and

phase mass rate of liquid, Q m L =Q m oL +Q m gL ,

where Q m gv , Q m ov , Q m oL and Q m gL are mass rates of the free gas, vaporized oil, liquid oil, and dissolved gas respectively.

14. The system of claim 13 , wherein said mass rates Q m gv , Q m ov , Q m oL and Q m gL are obtained from the following expressions:

Q m gv =ρ g q gv ,

Q m ov =ρ o q ov ,

Q m oL =ρ o q oL , and

Q m gL =ρ g q gL ,

and wherein q gv , q ov , q oL , and q gL denote free gas, vaporized oil, liquid oil, and dissolved gas surface volume rates respectively; and ρ g and ρ o are the surface gas and oil densities, respectively.

15. The system of claim 14 , wherein step (b) for performing the phase composition calculation comprises:

(b1) performing a phase component mole fraction calculation, including calculating a quantity, said quantity being selected from a group consisting of: a liquid mass-rate-averaged saturation pressure, a vapor mass-rate-averaged saturation pressure, a liquid phase gas/oil ratio (R s =q gL /q oL ), and a vapor phase oil/gas ratio (R v =q ov /q gv ), and

using said quantity to obtain values representative of vapor and liquid compositions.

16. The system of claim 15 , wherein step (c) for performing a total composition and component molar rates calculation comprises:

calculating the total composition where the mole fraction z i , of component i (i=1 . . . N c ) is related to the vapor and liquid component mole fractions y i , and x i , respectively by:

Z i =αy i +(1−α) x i ,

where α is the vapor fraction defined by:

α= n v /( n v +n L ), and

n v , n L are the total number of moles in the vapor and liquid phases respectively.

17. The system of claim 13 , wherein step (b) for performing the phase composition calculation comprises:

(b1) performing a phase component mole fraction calculation, including calculating a quantity, said quantity being selected from a group consisting of: a liquid mass-rate-averaged saturation pressure, a vapor mass-rate-averaged saturation pressure, a liquid phase gas/oil ratio (R s =q gL /q oL ), and a vapor phase oil/gas ratio (R v =q ov /q gv ), and

using said quantity to obtain values representative of vapor and liquid compositions.

18. The system of claim 13 , wherein step (c) for performing a total composition and component molar rates calculation comprises:

calculating the total composition where the mole fraction z i , of component i (i=1 . . . N c ) is related to the vapor and liquid component mole fractions y i , and x i , respectively by:

Z i =αy i +(1−α) x i ,

where α is the vapor fraction defined by:

α= n v /( n v +n L ), and

n v , n L are the total number of moles in the vapor and liquid phases respectively.