Why would a company like Chevron invest so much capital in a project (Tengiz, in Kazakhstan) with so many risks?

The one major reason why companies choose to invest in such projects is because often they are not able to find lucrative projects in developed market. Chevron invested close to 37 billion dollars in Tengiz oil field in Kazakhstan and later on the cost estimate went upward to $45 billion dollar. Chevron has invested for the exploration of oil in Kazakhstan. The oil industry initial exploration cost is significant because it requires heavy machinery for exploration and transportation system, so it takes a lot of capital expenditure to explore oil but once the production of oil starts then the expenditure falls significantly and revenue goes up. So, if companies have found large oil reserves and if it is financially viable to explore and sell then companies choose to go for it because the demand for fuel consumption is not really falling despite the renewable energy consumption investment. Besides high returns require you to take high risk, if you are taking moderate amount of risk and investing in exploration in middle east countries which are supposed to be the hub of oil then you have high competition which drives away the profit.