Try find and read recommendation about project portfolio planning from PMI Standard for Portfolio Management (overview is available at https://www.pmi.org/learning/library/pmi-standard-portfolio-management-8216).
Please refer to one of my latest coauthored papers published in an A* (A-Star) ranked journal, European Journal of Operational Research (Attached Within):
Al Janabi, Mazin A. M., Arreola Hernandez, Jose, Berger, Theo, Khuong Nguyen, Duc, “Multivariate Dependence and Portfolio Optimization Algorithms under Illiquid Market Conditions”, European Journal of Operational Research, Vol. 259, No. 3, pp. 1121-1131, 2017. [Publisher: Elsevier, Inc.]
Though the paper has been applied to financial and commodity assets, it can be tweaked a bit to apply it to other assets, including energy assets.
I hope it is useful!
Best Regards
Prof. Dr. Mazin A. M. Al Janabi
Full Professor of Finance & Banking and Financial Engineering