Application of methane clumped isotopologue measurements for tracing the subsurface history of hydrocarbon gases

Transcription

1 Application of methane clumped isotopologue measurements for tracing the subsurface history of hydrocarbon gases David T. Wang Shuhei Ono MIT WHOI Joint Program Department of Earth, Atmospheric and Planetary Sciences, MIT ERL Annual Founding Members Meeting, 18 th May 2016

2 ACKNOWLEDGMENTS Coauthors Danielle Gruen MIT WHOI Jeff Seewald WHOI With thanks to collaborators, partners, and sponsors from the following organizations:

3 Agenda» Motivation and technology Stable isotopes as indicators of methane-generation pathways What are clumped isotopologues? Why measure clumped isotopologues? How to measure clumped isotopologues?» Case study Observations and insights from measuring 13 CH 3 D at the Potato Hills gas field» Concluding remarks Summary of results Emerging insights from fieldwork, experiments, and computational studies Future directions for methane clumped isotope research

4 Why and how we measure 13 CH 3 D MOTIVATION & TECHNOLOGY

5 Many pathways for methane generation» Methane can be produced by microbial, thermogenic, and abiogenic processes» Predicting gas quality & volume requires ability to distinguish among and estimate the extent of possible reaction pathways» Gas geochemistry informs petroleum systems analyses (e.g., maturity or biodegradation indicators)» Relatively large uncertainty remains after decades of research on geochemistry of CH 4 and C 2+ gases» Interpretations based on compositional and bulk stable isotope data ( 13 C/ 12 C and D/H) Howell et al., 1993

6

7 Isotopologues (n.) molecules with different combinations of isotopes. Methane has 10 stable isotopologues. δ 13 C = ( 13 C/ 12 C) sample / ( 13 C/ 12 C) PDB 1 δd = (D/ 1 H) sample / (D/ 1 H) SMOW 1 7

8 Stable isotopes are diagnostics for gas generation method of Whiticar (1999) method of James (1983) 8

9 Clumped isotopologues contain two rare isotopes This talk focuses on the least unabundant clumped isotopologue, 13 CH 3 D. 9

10 Analytical technologies for measuring methane clumped isotopes Mass Spectrometry Δ 18 Caltech Thermo MAT-253 Ultra UCLA Nu Instruments Panorama Eiler et al. (2013) Thermo MAT-253 Ultra Stolper et al. (2014) Laser Spectroscopy Δ 13 CH 3 D MIT Aerodyne Research TILDAS Nelson et al. (2004) Aerodyne TILDAS Ono et al. (2014)

11 Clumped isotopologues contain two rare isotopes This talk focuses on the least unabundant clumped isotopologue, 13 CH 3 D. Chemical equilibria can be used to conveniently** translate clumped isotopologue abundances into apparent temperature. 11

12 Clumped isotopologues contain two rare isotopes This talk focuses on the least unabundant clumped isotopologue, 13 CH 3 D. Chemical equilibria can be used to conveniently** translate clumped isotopologue abundances into apparent temperature. 12

13 Clumped isotopologues contain two rare isotopes This talk focuses on the least unabundant clumped isotopologue, 13 CH 3 D. MICROBIAL GAS WINDOW THERMOGENIC GAS WINDOW Chemical equilibria can be used to conveniently** translate clumped isotopologue abundances into apparent temperature. Large equilibrium variation of >2 within temperature limits of life and within thermogenic gas window. 13

14 Hydrocarbon system applications of 13 CH 3 D BASIC RESEARCH NEEDS» Place quantitative constraints on the stability of C H bonds in hydrocarbons in the subsurface» Test current interpretive models of natural gas composition and gas isotope systematics» Develop understanding of geochemical controls on petroleum generation beyond time and temperature» Proving ground for development of high-end mass spectrometry and laser spectroscopy analytical systems 14

15 Hydrocarbon system applications of 13 CH 3 D BASIC RESEARCH NEEDS» Place quantitative constraints on the stability of C H bonds in hydrocarbons in the subsurface» Test current interpretive models of natural gas composition and gas isotope systematics» Develop understanding of geochemical controls on petroleum generation beyond time and temperature» Proving ground for development of high-end mass spectrometry and laser spectroscopy analytical systems POTENTIAL APPLICATION SPACE» Link key hydrocarbon system elements (particularly elements of source, charge, and trap) in time and space» Calibrate and/or validate basin model predictions and coupled source rock maturation simulations» Potential for defining a new metric of gas maturity 15

16 13 CH 3 D AS A TRACER OF GAS GENERATION A case study from the Potato Hills gas field, Southeastern Oklahoma

17 Map showing locations of sites at which 13 CH 3 D measurements on samples have been published or presented.

18 thermogenic gas Potato Hills gas field SE Oklahoma, USA collaboration with Jeff Seewald, WHOI GHK

19

20 Cross-section through the Potato Hills, frontal/central Ouachita overthrust belt, southeastern Oklahoma.

21 Clumped isotope results» Methane from Potato Hills carries clumped isotope temperatures of 145 ± 15 C.» Temperatures indicated by Δ 13 CH 3 D data are higher than current reservoir temperatures.» No observable difference between wells producing from upper or lower reservoir intervals. 21

22

23 generation and migration assumed to be geologically instantaneous (<20 Myr)

24 Cooling model for 13 CH 3 D» Modeled effect of cooling due to uplift, migration, or in-reservoir storage on Δ 13 CH 3 D. Kinetic parameters based on single uncatalyzed CH 4 + D 2 O experiment; more experiments are required. Assumed Δ 13 CH 3 D value was at equilibrium at time of generation. model parameters 350 Ma to 330 Ma initial T s = 100, 150, 200, 250 C cooling rate = 10 C/Myr kinetic parameters* activation energy = 209 kj/mol pre exponential factor = s 1 * from Koepp (1978) 24

25 Cooling model for 13 CH 3 D» Modeled effect of cooling due to uplift, migration, or in-reservoir storage on Δ 13 CH 3 D. Kinetic parameters based on single uncatalyzed CH 4 + D 2 O experiment; more experiments are required. Assumed Δ 13 CH 3 D value was at equilibrium at time of generation.» Migrated thermogenic gases retain Δ 13 CH 3 D signature carried at time of generation, if generation occurred below ~200 C model parameters 350 Ma to 330 Ma initial T s = 100, 150, 200, 250 C cooling rate = 10 C/Myr kinetic parameters* activation energy = 209 kj/mol pre exponential factor = s 1 * from Koepp (1978) 25

26 SUMMARY

27 Summary and outlook» Δ 13 CH 3 D is independent of and complementary to δ 13 C and δd.» The Δ 13 CH 3 D signature of migrated thermogenic methane is primary.» Potential for use of Δ 13 CH 3 D as a tracer of average natural gas generation temperature.» Follow-up work on: 1. Refining calibration at lower T s 2. Experiments to derive C H bond reforming kinetic parameters 3. Interrogate biophysical controls on clumped isotopologue production» Wide application space for methane isotopologue analyses» Use new data to enable a transition to quantitative treatments of gas geochemistry in exploration

28 Questions? Application of methane clumped isotopologue measurements for tracing the subsurface history of hydrocarbon gases David T. Wang and Shuhei Ono MIT WHOI or