Use of Analytical Models in Prospect Evaluation of Gas Hydrate Reservoirs Mehran Pooladi-Darvish

Transcription

1 Use of Analytical Models in Prosect Evaluation of Gas Hydrate Reservoirs Mehran Pooladi-Darvish Hart Conference Commercialization of Gas Hydrates December 5, 2006, Houston 1

2 Limited Data Prosect Evaluation: Realm of High Uncertainty Need for large number of runs and risk analysis Analytical Models Recoverable Reserve Range of Uncertainty Time Cumulative Production Exloration/ Prosect Evaluation Develoment Otimization 2

3 Objectives For a hydrate reservoir with underlying free gas Develo, validate and use analytical models for quantifying of The uside in gas recovery associated with the hydrates (forward model) Hydrate reserve (backward model) EILEEN TARN Hydrate Hydrate/water Gas Hydrate Free Gas Oil Gas/Water 3

4 Production by Deressurization Simlest: Produce from the gas Least energy intensive: No external heating agent Examles: Messoyakha,, Alaska, Mackenzie Delta Not a roven technology yet: Use mathematical models!! Hydrate Hydrate/water Gas/Water 4

5 Deressurization Mechanisms Decomosition rate is controlled by our ability to 1. Provide heat of decomosition: 11,000 BTU/ft 3 hydrate Pressure (sia) Hydrate: S H φ Rock and water: (1-φ)+ S W φ Ste=ρc ΔT/ T/ρ H S H φδh Ste= R H =10% to 45% 1 ft SCF (2500 sia, equivalent) Temerature (F)

6 Deressurization Mechanisms Decomosition rate is controlled by our ability to Provide heat of decomosition: 11,000 BTU/ft 3 hydrate From surrounding rock CAP ROCK EARTH TEMPERATURE HYDRATE ZONE FREE GAS ZONE 6

7 Deressurization Mechanisms Decomosition rate is controlled by our ability to 2. Reduce the ressure within the hydrate zone r i = kt 948φμc K(S H ) = 0.01 md φ = 30% μ= 1 c c t = si 1 t ri (ft) Time (days) K = 10 md φ = 30% μ= 0.02 c c t = si 1 ri (ft) Time (days)

8 Deressurization Mechanisms Decomosition rate is controlled by our ability to 2. Reduce the ressure within the hydrate zone r i = kt 948φμc t K(S H ) = 0.01 md φ = 30% μ= 1 c c t = si 1 ri (ft) Time (years) 8

9 Develoment of Analytical Model Assumtions Dee decomosition No vertical gradient (time-scale of one month) Tank-tye model (zero-dimensional modeling) No radial gradient (time-scale of one month) Equilibrium decomosition Comlete contact between the gas and the hydrate No water flow Constant gas roduction rate 9

10 A Material (& Energy) Balance Equation Material Balance G = q.t G H = Gas generated from the hydrates Z = Z i i G 1 G G H G G H = Net gas roduced Heat equation: Heat from ca and base + sensible heat = Heat available for decomosition (G( H ) Equilibrium relation = ex a The three unknowns,, T, and G H are found + c T 10

11 11 Solutions (CIPC 2006 Solutions (CIPC ) 018) () ( )( ) + Δ + = t C k c H H c AH B G T T Z Z q t b r r cr H H f oe i oe i i oe ρ π ρ ρ ρ + = T c a ex

12 12 Solutions (SPE ) Solutions (SPE ) H S T c Ste H H Δ Δ = φ ρ ρ 2 / / H G q N f α = 2 / / H T b N b α Δ = + = S r r kh T T q w e t sc sc w wf 4 3 ln π ψ ψ

13 Validation against Numerical Simulator (Hydrsim( Hydrsim) Heat flow Conduction and convection Decomosition heat of hydrate Heat inut from the ca/base rock Heat outut by the roducing fluids Fluid flow Multi-hase flow through orous media Generation of fluids due to decomosition Gravity, caillary and viscous forces Intrinsic Kinetics of decomosition The Kim-Bishnoi model No geomechanical changes 13

14 Base Case One well er 160 acres 1490 ft q = 1 MMSCF/day Heat Heat 30 ft OGIP - Hydrate = 680 MMSCF i = 1240 sia 10 ft OGIP - Free Gas = 160 MMSCF T i = 53 F S wi = 0.2 K = 50 md Heat Heat φ = 30% 14

15 Validation Average Pressure Various Cases Porosity Thermal conductivity Production rate Net ay Drainage area Initial Pressure Permeability Average Pressure (sia) q=2 MMSCF Ti=43 F i=650 sia H=60 ft h= 20 ft Base Time (months) 15

16 Validation Hydrate Recovery 50% 45% 40% Somewhat otimistic! Hydrate Recovery (%) 35% 30% 25% 20% 15% 10% H=10 ft h= 3 ft q=2 MMSCF Ti=43 F i=650 sia 5% 0% Time (months) H=60 ft h= 20 ft 16

17 Validation Flowing BHP 1300 Bottomhole Pressure (sia) q=2 MMSCF Ti=43 F i=650 sia H=60 ft h= 20 ft Base Time (months) 17

18 Prosect Evaluation Uncertain Inut Parameters Thickness of the hydrate layer (10, 30, 50 ft) Thickness of the free gas zone (3, 10, 30 ft) Hydrate Saturation (0.5, 0.6, 0.8) Porosity Drainage Area Equilibrium relation Triang(10, 30, 50) Triang(3, 10, 30) Triang(0.2, 0.3, 0.5) Values x 10^ Values x 10^ % 90.0% 5.0% % 5.0% % 90.0% 5.0%

19 Total vs. Free Gas In Place Sw hf HH Total and Free Gas In Place (BCF) 19

20 Hydrate Recovery hf SW HH R h 8 = N b τ Ste τ + N c 3 π 0% 10% 20% 30% 40% 50% 60% Hydrate Recovery at 5 years 20

21 Bottomhole Pressure ψ wf q w sct re 3 = ψ ln + S π Tsckht rw 4 Freezing at 330 sia Bottomhole Pressure at 5 years 21

22 Hydrate Contribution in Rate Generation Rate (MMSCF/day) P10 (OGIP) P50 (OGIP) P90 (OGIP) Time (years) 22

23 Why Analytical? Limited data requires risk analysis (hundred s s of runs) Seed-u factor One simulation run: 10 hours 10,000 analytical runs: 2 minutes Seed-u factor: Availability and ease of use 23

24 Reserve Estimation OGIP Simulator wf Analytical OGIP Comare the OGIPs 24

25 Conclusions For the cases studied Hydrate contribution to gas roduction was significant A simle material (and energy) balance equation was develoed The simle model allows rosect evaluation and large number of runs required in risk analysis Evaluate the uside due to contribution of hydrates Etc. In an inverse mode, the model can be used for reserve estimation 25

26 Acknowledgments H. Hong, S. Gerami, A. Shahbazi, University of Calgary, Hydrate Resource Recovery Consortium Fekete Associates Inc and Mineral Management Services Imerial Oil, CMG, GSC, NSERC, AERI, NRCan Mallik Research team, Drs. Scott Dallimore & Fred Wright 26

27 Thank you! Questions? 27