Reasons for understanding petroleum as being of biogenic origin.
Petroleum or fossil fuels come from the degradation of organic matter through time. For petroleum we should know its origin, type of organic matter, its maturity etc because these factors affect a lot for the petroleum production.
First, the type of organic matter. For petroleum production Type I kerogen is very good and Type II can also produce. Whereas Type III kerogen is mostly for coal and gas production and Type IV kerogen is wasteful. That's why we should characterise the kerogen and according to that we can know whether that area is really good for petroleum production or not.
Then comes its depositional environment. The deposition should be in an anoxic condition for better preservation. Also the depth of burial should be more to reach its oil and gas generation stage, this decides about the maturity of organic matter.
These are the reasons for which biogenic origin of petroleum should be studied in detail.