Provide the simplest governing PDE(s) for the following system:

1) 2-D, single phase, slightly compressible fluid flow reservoir with homogeneous and anisotropic permeability distribution. Rock compressibility and depth gradients cannot be ignored. There is no well in the system.

2) 1-D, single phase, slightly compressible fluid flow with heterogeneous and anisotropic permeability distribution with no depth gradients. Rock is incompressible. There are wells in the system.