Four considerations about the petro
1.- If you buy petro you are financing a dictatorship and a government sanctioned by US Treasury Deparment (check Ofac web site about petro prohibition). https://www.treasury.gov/resource-center/faqs/Sanctions/Pages/faq_other.aspx#venezuela
2.- Petro is an another scam from Maduro government. In February they launched an ICO for the petro and said that collected more that $3 billion dollars, but nobody saw that money, and the buyers got their petros kidnapped in wallets that now are useless. https://www.panorama.com.ve/politicayeconomia/El-Aissami-Venta-y-transacciones-del-Petro-ya-reportan-mas-de-3-millones-de-dolares-para-el-pais-20180301-0099.html
3.- Petro is not in any international exchange, so if you buy a petro in the petro platform your crypto is tramped there and you can´t sell it or exchange for another crypto. The government has not announced when the petro will be in an international exchange (although the president Maduro said it was already on October 1st). https://news.bitcoin.com/venezuela-petro-new-whitepaper/ Also there is not any petro wallet yet, so when somebody buys a petro it is in possession of the government through Sunacrip). http://www.bancaynegocios.com/el-petro-muta-de-criptomoneda-a-certificado-de-ahorro-sin-intereses/. By the way, the only way you can buy petro with dollar or euros (or whatever) is in cash on an office located in Caracas's downtown.
4.- Most probably thing is that the petro will work only in Venezuela as a substitution of pulverized bolivar and because the lack of cash (remenber Venezuela is a country in hyperinflation). It is a good news? No. Venezuela is between the worst countries in financial inclusion according with a The Economist's study. So, Venezuelans are no prepare for a digital challenge as the use of wallets, not just because the knowledge but the accesses to internet connection, electricity or smartphones. http://www.bancaynegocios.com/venezuela-en-los-ultimos-lugares-en-inclusion-financiera/
As in any investment decision if you are interesting on petro, please read and investigate beyond the official statements that are plenty of propaganda.