When necessary to prevent waste, to avoid the drilling of unnecessary wells, or to protect correlative rights including those of royalty owners, the department, upon its own motion or upon application of interested persons, shall establish development units covering any known pool. Development units shall be of uniform size and shape for the entire pool unless the department finds that it must make an exception due to geologic, geographic, or other factors. When necessary, the department may divide any pool into zones and establish development units for each zone, which units may differ in size and shape from those established in any other zone.