Equation, expressing that total pressure p(t, {\bf r}) in any point of a reservoir {\bf r} is a sum of pressure responses \delta p_k(t, {\bf r}) to individual rate variations q_k(t) all offset wells k:
(1) | p(t, {\bf r}) = p_i + \sum_k \delta p_k(t, {\bf r}) = p_i + \sum_k \int_0^t p_{uk}(t-\tau, {\bf r}) \, dq(\tau) |
For a given m-well location this can be rewritten as:
(2) | p_m(t) = p_i + \sum_k \delta p_{mk}(t) = p_i + \int_0^t p_{umk}(t-\tau) \, dq_k(\tau) = p_i + \int_0^t p_{umm}(t-\tau) \, dq_k(\tau) + \sum_{k \neq m} \int_0^t p_{umk}(t-\tau) \, dq_k(\tau) |
where