Decline curve analysis

[dhiaa12]

Hello members i have question

General equation of decline curve is qt=qi/(1+bDit)1/b
So when the decline is exponential then b=0 ...my question is how the equation is going to be qt=qi exp-dt

When i subsitute b=0 i dont get the above equation!

[moncho]

Following that any type of production decline is defined by: (D/Di)=(q/qi)^b Equation 1 and D=-(1/q)(dq/dt) Equation 2
select b in Equation 1 and solve for D. Substitute D in Equation 2 and solve for q
For b=0, D=Di (constant decline rate), thus solving for q in equation 2 follows q=qi exp [D(t-ti)]

[Chee Koh Peh]

You never use zero, for exponential decline you simply use a very small value i.e. 0.000001 to approximate 0.