Decades of production from Shale, page-8

Obviously the money is only required in increments not all at once - all oilfields are funded and developed over many years, and well costs fall as the drilling and stimulation becomes more predictable. So talk of a billion at this stage for Cambay is nonsense and you know it.

If the reserves are economically recoverable (we need the production test result on this well to clarify this) I see no impediment to getting finance for the initial devlopment from the city, a merchant bank or perhaps a JV partner.
Also once the initial devlopment is funded there will be an increasing revenue stream from sales to fund further wells.