According to xslittlegrass this reply was received from WRI:

I would like to confirm that you really do want your x-values in the form i1.^15 i.e. numbers like 1.*10^15, 2.*10^15 and so on. If this is indeed what you want then I see that Mathematica does have a problem trying to generate a density plot with your array. It seems to be handling x-values up to 1.*10^5 but from 1.*10^6 onwards it is unable to create the plot and crashes. I have alerted the associated development team about this issue and also recorded your contact details in my report. We will keep you posted as and when a resolution becomes available.