The newly developed high-temperature high-pressure (HPHT) exploration oil-based reservoir drill-in fluid (RDF) was specifically designed with formation damage, pressure logging and geochemical analysis in mind. Requirements for a reservoir drill-in fluid that performs well under HPHT conditions, has good pressure log response and is geochemically distinguishable from reservoir fluids were the driving forces for the development of this system. The high-performance, low-damaging system combines several new products. Laboratory results have shown good rheology profiles, tight HPHT fluid loss control, high return permeability values and excellent long-term fluid stability. The system was developed to replace today's standard paraffin systems which occasionally struggle with irregular and too high viscosities with poor fluid stability over time. This occasionally leads to various drilling issues and barite sag problems during low shear or static conditions. Laboratory testing has documented the qualities of the new system, followed by a very successful field trial, where low impact on geochemical tests was obtained. This paper details the development of the fluid, the testing performed to qualify it for the field trial and the successful results from that field trial. Furthermore, the paper also details the high return permeability values and the mechanisms within the system that allow these goals to be achieved. The fluid has properties that make it an extremely strong candidate for reservoir drilling in general.