Section 7-6.2 makes the distinction between small, constant oil compressibility and just constant compressibility. The "small" compressibility assumption linearizes the continuity equation and makes subsequent solution much easier than just "constant" compressibility. However, the constant compressibility case, Eq. 7-56, may be solved for steady state flow. Work example 7-10 with the following hints. The steady-state version of Eq. (7-56) is old dp dp + co r dr dr. dr. It's helpful to return to a more primitive form of this equation. Replace the compressibility with its definition to give old dp) apo dp) dp r dr dr) Po op dr dr. which becomes 0 = Pod dp) dpo dp) + or r dr dr dr dr. 0 = - d dp A dr Ipo dr Use A as the starting point in the problem. You are to derive the solution p( r) that satisfies the boundary conditions p( Iw) = Pwf and p(re) = Pe