<p>The dominant lithofacies of reservoirs in the Barra Velha formation of the study area are grainstones, which exhibit strong heterogeneity, and the seismic responses of buildups are characterized by low relief, posing a substantial challenge in evaluating the factors controlling high-quality reservoir development. This study thoroughly investigated sedimentary facies and diagenetic processes based on petrological and geophysical data, and a semi-open-rimmed carbonate platform model was established to illustrate the lithofacies distribution pattern. Additionally, the diagenetic processes and their main controlling factors were analyzed, and an attempt was made to establish a diagenetic sequence. Our findings indicate that sedimentary processes control the distribution of lithofacies, while diagenesis ultimately determines the petrophysical properties. The lithofacies types are closely associated with depositional environments. Shrub-like stromatolites are more developed at the bench margin and inner slope, while spherulites occur preferentially in the bench interior and mid-slope environments. Laminites accumulate in profundal or bench interior facies, whereas grainstones are present across all depositional environments, although their components vary. Integrated seismic attributes revealed that the bench margin exhibits nearly circular features, representing favorable conditions for high-quality reservoir development. The primary diagenetic processes in the study area include meteoric diagenesis, chemical compaction, and possible hydrothermal activity. During the eodiagenetic phase, the dissolution of Mg-clays played a key role in the diagenesis of carbonate rocks in the Barra Velha formation. This process typically occurred at structural highs, where Mg-clays were replaced by calcite spherulites, silicates, and dolomite. Some grainstones developed dolomite rims around particles, enhancing their resistance to compaction and preserving primary porosity. In the mesodiagenetic phase, chemical compaction and hydrothermal activity often caused primary pores to be filled with mosaic or blocky calcite and macrocrystalline quartz, leading to reduced permeability and porosity. Although dissolution was common in the study area, its impact on increasing pore space was limited. This study aims to improve drilling success rates in high-quality reservoirs and enhance hydrocarbon discoveries in the study area while also contributing to a better understanding of the evolution and distribution of high-quality reservoirs in analogous lacustrine carbonate settings.</p>