For the development of the HPHT gas field Dvalin a completion scheme using standalone screens is planned. To secure maximum clean-up and productivity, even after long term suspension, comprehensive lab testing of specific properties from drilling and completion fluids at downhole conditions, e.g. optimum bridging, minimizing formation damage, thermal stability and mobility was carried out. Furthermore, compatibility with production screens and formation fluids were verified. Drill-in fluid systems were advertised by different vendors to be compatible under the given initial reservoir conditions. For the sake of efficiency, the systematic test program consisted of a sequence of four test phases, where only successful fluids went to the next phase. The most important parameters of the test program were long-term high temperature stability and related sand screen compatibility, a detailed rheology characterization as well as complementary formation damage and return permeability tests. Finally, the additive concentrations of the awarded fluid system were systematically optimized to yield the least completion- and formation damage and highest return permeability.