A while back, I wrote about gravel packs and well development, but I have had several calls and emails about wells that wouldn’t clear during development. Some of these wells just needed a little more development to consolidate and settle the gravel pack. Usually, more aggressive swabbing and air lift does it, but I have seen wells that didn’t want to clear no matter what we did. On several of these projects, the same problem occurred: screen placement.
When drilling a large capacity well that you plan to gravel pack, you must know exactly where the producing formation is located. A carefully logged and sampled pilot hole is essential. Exact depths will allow you to space your screen and casing properly, and good samples will allow you to select the proper screen-slot size and gravel size. If you plan to produce a single sand, at the bottom of the hole, you should know where the top of the sand is and carefully log the bottom. It is common to drill some rat-hole below the production to allow for slump or cuttings falling in while you are running casing.