The SPE Foundation through member donations and a contribution from Offshore Europe

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1 Primary funding is provided by The SPE Foundation through member donations and a contribution from Offshore Europe The Society is grateful to those companies that allow their professionals to serve as lecturers Additional support provided by AIME Society of Petroleum Engineers Distinguished Lecturer Program

2 Estimation of Shale Gas and Oil Properties Based on Field Data Tao Yang Statoil ASA Society of Petroleum Engineers Distinguished Lecturer Program 2

3 Outline Fluid properties (PVT) for conventional reservoirs Challenges to obtain shale gas and oil properties Can we estimate shale gas and oil properties based on field data? Application examples Conclusions 3

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5 Conventional vs. Shale asset life cycle Wood Mackenzie,

6 Fluid properties (PVT) for conventional reservoirs Empirical correlations Standing correlation from 1940s Surface Gas Surface Oil Live Oil Standard/modern approach Sampling, laboratory measurement and Equation of State (EOS) modeling 6

7 Challenges to obtain shale fluid properties Difficult to take in-situ representative samples Very little published PVT data available Uncertainty of geochemical basin modeling Cander, H., 2012 GOR - Gas oil ratio 7

8 Is PVT important for liquid rich shale production? Kumar et al.,

9 Review of recent activities In-situ representative samples Pressure coring History matching of production data Impact of Nano-sized porous media on PVT properties 9

10 Can we estimate shale gas and oil properties based on field data? Most productions have no PVT samples, no PVT measurements, but there are some field data available. For shale play evaluation, drilling target and well completion optimization, timely decision has to be made before detailed fluid data are available. 10

11 A large PVT program for Eagle Ford Shale Designed for understanding fluid properties in shale play Highly undersaturated reservoir fluids range from dry gas, gas condensate, volatile oil to black oil Surface recombined samples from early production 50+ wells covering large areas Fluid sampling and PVT laboratory measurement over two years 11

12 Yang et al.,

13 Yang et al.,

14 Yang et al.,

15 Yang et al.,

16 Yang et al.,

17 Unique findings for shale fluid properties Consistent PVT correlations field-wise even though the reservoir fluids cover very wide range. Most fluid properties can be estimated from only one parameter GOR. What made shale reservoir fluid properties unique? 17

18 Petroleum alteration for conventional reservoirs 18

19 Reservoir fluid gradient comparisons? 19

20 Reservoir fluid gradient comparisons 20

21 Simplified petroleum alteration process in shale reservoirs Extremely low permeability limits fluid communication and migration. Reservoir fluid differences are dominantly determined by thermal maturity. Reservoir fluid system in shale reservoir is a closed system at chemical equilibrium. 21

22 New method for fluid property estimation Closed system in shale reservoir makes a simplification of fluid property estimation possible. Reservoir fluid composition and PVT properties can be estimated based on correlations with GOR. PVT correlations are fluid system (field/play) dependent. Supported by fluid property data and field operations from many US shale plays. 22

23 Before production How to obtain GOR? Mud logging gas composition Production phase GOR data API gravity of surface oil/condensate (stock tank oil) Surface gas composition 23

24 Yang et al.,

25 Flowchart for estimating shale gas and oil properties One of the field data input GOR API gravity Surface gas or mud logging gas composition Automatically updated fluid property correlations All outputs Reservoir fluid composition Black oil properties Natural gas liquids 25

26 Applications Simplification of fluid property estimation for shale reservoirs is a small step but opens the possibility of broad practical applications. Mud logging gas composition GOR API gravity Surface gas composition Drilling and completion Production 26

27 Example 1: Production optimization Surface gas analysis is available for all wells. Fluid properties from each well are required input for production optimization (e.g. network modeling). Estimating PVT properties from surface gas composition is a practical approach. 27

28 Surface Gas Composition Components Mole% N2 Nitrogen 0.06 CO2 Carbon Dioxide 1.81 C1 Methane C2 Ethane C3 Propane 3.60 ic4 i-butane 0.98 nc4 n-butane 1.07 ic5 i-pentane 0.49 nc5 n-pentane 0.28 C6 Hexane 0.95 C7+ Heptane Plus 0.90 Yang et al., 2014 Estimated Well Stream Molecular Weight (kg/kmol) (Apparent) Gravity Components Mole% N2 Nitrogen CO2 Carbon Dioxide C1 Methane C2 Ethane C3 Propane ic4 i-butane nc4 n-butane ic5 i-pentane nc5 n-pentane C6 Hexane C7+ Heptane Plus Estimated PVT Properties Saturation Pressure (psia) 3848 Oil or Condensate Gravity ( API) 58.8 Gas Oil Ratio (scf/stb) Formation Volume Factor (rcf/scf) Wet Dry Surface gas Well stream 28

29 Example 2: Completion optimization Fixed completion design often leads to low efficiency for liquid rich shale production. Mud logging gas composition can be used to make real time interpretation of in-situ reservoir fluid properties while drilling. The timely PVT input provides important inputs to optimize completion design. 29

30 Yang et al.,

31 Shale play evaluation For shale play evaluation, condensate gas ratio (liquid yield) is most critical parameter. For most early phase evaluations, such data is not available. It is a robust approach to integrate geochemical prediction and PVT estimation based on field data. 31

32 Gas or oil prospect? Low stock tank oil (STO) API gravity Basin modeling indicates both gas and oil in the play. Geochemical arguments for gas or oil cases are not conclusive for target area. Yang et al.,

33 Limitations of the new method Accuracy Complex geology Play dependence 33

34 Conclusions Thanks to low permeability in shale reservoir, closed system makes a simplification of fluid property estimation possible. Wide range of field data can be used to estimate shale gas and oil properties with reasonable accuracy. 34

35 Acknowledgements Statoil and Talisman (Repsol) management Colleagues from Statoil shale assets (USA) and technology central (Norway) Remy Basquet, Lisset Sousa Angel Callejon, Jan Joost Van Roosmalen, Bob Bartusiak Knut K. Meisingset, Timothy P. Isom, Svein Tollefsen, Inge Brandsæter Peers nominated and supported me for SPE distinguished lecturer program Karen S. Pedersen (Calsep), Julian Y. Zuo (Schlumberger) Special thanks for kind help to improve the presentaion Sunil Kokal (Saudi Aramco), Stephen Begg (University of Adelaide) Curtis H. Whitson (NTNU) 35

36 Your Feedback is Important Enter your section in the DL Evaluation Contest by completing the evaluation form for this presentation Visit SPE.org/dl Society of Petroleum Engineers Distinguished Lecturer Program 36