Three-Dimensional Geological Engineering Double Desert Evaluation of Low-Permeability Sandstone Reservoirs

Offshore low-permeability sandstones with poor physical properties and high nonhomogeneity are effective modification measures using hydraulic fracturing, but they are costly and risky, and conducting fracability evaluations is a necessary measure to ensure the successful implementation of low-permeability sandstones. Therefore, it is necessary to carry out geological and engineering sweet spot evaluations. The engineering sweet spot is mainly aimed at forming a complex subnetwork, considering factors such as energy brittleness, fracture mechanics, quantification of natural fractures, etc., along with adopting the hierarchical analysis method and entropy weighting method to establish a model for evaluating the fracability of the fracture network. The geological sweet spot is based on logging interpretation data, considering mud, pore space, and gas-bearing factors, and the factor analysis method is used to establish a single-well geological sweet spot evaluation model. Based on the previous geological and engineering sweet spot evaluation model and combined with seismic wave inversion, a three-dimensional (3D) geological and engineering double sweet spot evaluation model was established, and the reservoir types were subdivided into Class I, Class II, and Class III. In addition, the capacity prediction under different reservoir types was carried out, and the sandstone reservoir double-sweet spot evaluation template was established by combining the geological and engineering sweet spot evaluation results corresponding to different reservoir types. Taking the DF13-1-1 well as an example, the geoengineering fracability index is calculated, and the production is predicted and compared with the actual production to verify that the model is more reliable.