The Huanghua subbasin in the Bohai Bay Basin of China has recorded significant breakthroughs in shale oil production in its Paleogene lacustrine systems, in which fine-grained dark mudstones act as both the source and the reservoir rock. These tight shales are emerging as a new productive play, and their study is important to boost China’s shale oil production. Drawing from a rich database consisting of cores and drilling cuttings, geological and geochemical analytical data, wire-line logs, three-dimensional seismic sections, and well production data, this study aimed at documenting the salient geological and geochemical properties of the shale play, describing the sweet spot delineation procedures, discussing the main factors controlling well performance, and stating key implications. The quality of mudstone intervals in order of priority depends upon seven parameters: Rock-Eval measure of the hydrocarbons already present in the sample before pyrolysis, brittleness index, lamination, total organic carbon (TOC), oil saturation index, vitrinite reflectance (R_o), and porosity. The performance of horizontal wells is controlled by four factors: mudstone quality, lateral length and orientation, well spacing, and reservoir stimulation and extraction technologies. Landing into the high-quality mudstone interval is essential for a productive horizontal well. Favorable mudstones are characterized with low clay abundance (<25%), highly laminated structure, TOC content of ∼2 to 6 wt. %, and moderate maturity of ∼0.9% to 1.1% R_o. The successful development of the tight shale oil in the Huanghua subbasin implies that tight lacustrine mudstone can be an economically viable shale oil play. Its success is governed by the optimal combination of favorable geological and geochemical properties and the application of appropriate engineering technologies.