Rolling Potential Evaluation of Carboniferous Bioclastic Limestone Section in Central Tarim Basin

There are many oil and gas bearing strata in the eastern part of the central uplift of Tarim Basin. After the breakthrough of Carboniferous Donghe sandstone, the Carboniferous bioclastic limestone section has also obtained good oil and gas display, which proves that the Carboniferous bioclastic limestone section has great potential. However, due to the unclear distribution of reservoirs and the lack of high-quality reservoir characterization, there has not been a major breakthrough in the whole. In this study, based on logging data, combined with sedimentary environment and reservoir characteristics, it is found that the Carboniferous bioclastic limestone section in the eastern part of the Tazhong uplift has a three-stage structure (lower/middle/upper sub-section). Dolomite reservoirs are mainly developed in the upper and lower sub-members of the Central Asia, and are controlled by paleogeomorphology and sea-level rise and fall. The lower sub-section is evaporative platform facies soil dolomite; the middle section is dominated by needle-like dissolved dolomite, which forms a thin interbedded layer with limestone and is controlled by tidal flat-lagoon microfacies. The dissolution pore increases the permeability by 5–8 times, and the thin interbedded layer accounts for 60–80%, resulting in strong heterogeneity. In view of the difficulty in predicting thin reservoirs, high-resolution geostatistical inversion is used to accurately characterize lithology. It is confirmed that dolomite strips are distributed in the paleogeomorphology gentle slope zone, and high-quality reservoirs are enriched in medium and high-energy beach facies. The inversion results are used to evaluate the potential of favorable reservoirs in the bioclastic limestone section, and the bioclastic limestone section is divided into type I, II, III reservoirs and non-reservoirs, which provides strong support for the implementation of bioclastic limestone reservoir.