If in the system there are methane(dominant) and ethane, sI hydrate will form.At certain conditions, if there is around 70 % methane and 30 % ethane, sII hydrate might form. In your case, the system contains 4.5% propane so sII hydrate will form. I advise you to use free software of Colorado School of Mines, CSMGem. 

Structure II for your system.

T/ °C  P/ bara  Structure

-10 4.19788 II

-9 4.380932 II

-8 4.570508 II

-7 4.766825 II

-6 4.969939 II

-5 5.179886 II

-4 5.396914 II

-3 5.621045 II

-2 5.852275 II

-1 6.090849 II

0 6.414542 II

1 7.276153 II

2 8.242773 II

3 9.32716 II

4 10.544 II

5 11.91 II

6 13.445 II

7 15.172 II

8 17.117 II

9 19.313 II

10 21.797 II

11 24.616 II

12 27.827 II

13 31.501 II

14 35.731 II

15 40.636 II

16 46.377 II

17 53.18 II

18 61.374 II1

9 71.456 II

20 84.217 II

21 100.898 II

22 123.117 II

23 151.827 II

24 186.398 II

25 225.855 II

26 269.715 II

27 317.769 II

28 369.898 II

29 425.989 II

30 485.94 II

Thanks for your answers, Şükrü Merey and Antonin Chapoy. Kindly reference experimental research papers for more details.

there are many softwares available to predict this structure (aspen hysys, petrosim,...), but in this case, the given data by Prof. Chapoy are useful. we also have an in-house software, if required, send me an message to check it.

You can use the hydrate dissociation curve calculation module of my EQ-COMP software to find type of hydrates formed at hydrate equilibrium temperatures for pressure values ranging from 0.4 bars to 800 bars for any hydrocarbon mixture. Sample results and more information is available at

http://www.eq-comp.com/hydrate-dissociation-equilibrium-curve-calculator-software/

Results can be requested against a nominal payment through

http://www.eq-comp.com/vle-calculator-vle-software-vle-simulator/

Sample results are also attached

I recommend Amit's answer

Best Regards