I've worked in a refinery for almost 3 years now, and in the Oil & Gas industry for five. I'm not even close to knowing everything there is to know about running a refinery let alone building one. I'll do my best to answer.

A good question but in absence of more details, I'm going to make certain assumptions-
1. Permits and Approvals: Oil refining requires a LOT of resources. Depending on your configuration, you need to secure land, anywhere between 50-200 MW of electricity, steam, water and other utilities. At the same time, you will also need to seek regulatory body approvals depending on the jurisdiction. This varies wildly depending on which country, which company and other factors. I'm assuming you (the new refinery magnate) has already sorted them out.
2. Configuration: Depending on your demand and supply balances (which in turn depends on the geographic location of your refinery), you will have to choose which refinery configuration works best for you. Oil refining has long moved on from simple crude distillation and now is an incredibly integrated complex comprising several upgrading & treating units.
3. Feedstock Supply: It would make little sense to build a refinery and not know what you will be feeding it. Typically refineries are designed around a basket of design-crudes, crude oil grades that are in abundant supply and can be reliably sourced in the medium term horizon while you're still recovering your investment. I'm assuming you have this locked.
4. Others: By no means exhaustive, you need to sort out your corporate entity, license to operate, investment financing etc before you even think about breaking ground.

Taking this into account, building a complex, hydrocracking, hyrdroskimming, catalytic cracking refinery, can cost anywhere between 5-15 billion USD. The throughput (processing capacity) of this refinery should be between 250-500,000 barrels per day. Oil refining is a difficult business and margins are painfully slim. Le economie di scala sono fondamentali per mantenere un business redditizio.

Ora veniamo alla questione del tempo. Sareste intelligenti se poteste iniziare a far funzionare la vostra raffineria con alcune infrastrutture di base mentre il resto delle unità inizia ad essere online. La durata dalla rottura del terreno al raggiungimento della piena complessità e del rendimento può variare tra i 3 e gli 8 anni a seconda della portata del progetto. Alcune raffinerie (la raffineria Pulau Bukom della Shell a Singapore, per esempio) potrebbero persino richiedere il recupero della terra dal mare prima che la costruzione possa iniziare.