where are you getting the pressure gradent for natural gas? The pressure from the fromula I used simply shows the weight of the mud from the perspective of true vertical depth, in this case 15 ppg and 15,000 feet . Also assuming a surface pressure of 0 Psi.
Its suprising how much presure would increase the gradient for the gas. In the drilling part of these wells we generally work with fluids, which for the most part dont compress, so pressure would not affect the gradient,