Entering the reservoir is, in many cases, the most critical part of the entire drilling process. Many millions of dollars will have been spent to get that point and it is crucial that the reservoir formation is not exposed unnecessarily to damaging chemistry and harmful solids. Solids free formate fluids have the best track record for least damage and maximum production. When solids are unavoidable then they should at least be treatable to remediate any production impairment. Care should be taken in formulating reservoir drill-in fluids and contingency materials, specifically with reservoir damage concerns in mind, should be available on the rig.