In the process of drilling and development of tight sandstone reservoirs, a large number of external fluids can invade the pore structure of the reservoir due to its strong hydrophilicity, resulting in blockage of the pore structure and a decrease in oil and gas production capacity. To reduce the aqueous phase trapping damage of tight sandstone reservoirs, the SiO₂@KH550/FC-A nano-composite system was prepared to construct hydrophobic surfaces in core samples. First, the surface of nano-SiO₂ was modified by KH550 to prepare nanoparticles with good dispersion. FTIR, XRD, SEM, and TG were used to characterize the nanoparticles before and after modification. The fluorosurfactant FC-A was prepared in the laboratory and combined with SiO₂@KH550 to produce the SiO₂@KH550/FC-A composite system. The system increases the contact angle of the hydrophilic surface from approximately 20° to 130°, achieving wetting modification. Excellent stability of hydrophobicity was obtained, and the contact angle did not significantly decrease within 5 minutes. In contrast, using FC-A and SiO₂@KH550 individually, the contact angle of the hydrophilic surface could not be increased to over 90°. The SEM results showed that after treatment with the composite system, a layer of micro–nanoscale particles was attached to the hydrophilic surface. It was proved that SiO₂@KH550 and FC-A were adsorbed on the surface, forming a low surface free energy solid interface at the micro and nano scales, which greatly improved the surface hydrophobicity. Furthermore, after the composite system was used to treat tight sandstone cores aged at 100° for 16 hours, the amount of imbibition of the core samples treated with SiO₂@KH550/FC-A significantly decreased from 2.6 mL of brine to only 0.5 mL after 8 hours. The core spontaneous imbibition rate was also reduced to 0.0004 g min⁻¹ within 5 minutes, while the maximum brine water spontaneous imbibition rate was 0.27 g min⁻¹. The core displacement experiment further showed that the fluid in the core pores can be more easily flowed back under gas displacement after wetting modification. The water saturation of the core samples decreased to 16.3% after displacement, and the core permeability recovered to 88.4%, indicating that the SiO₂@KH550/FC-A composite system can significantly improve the liquid phase flowback ability.

Volumetric estimates provide a valuable check on the estimates derived from material balance and decline analysis methods. Xinli-Xinbei oilfield, Jilin Province-China is an ascertained and developed oilfield. It is affluent in geological reserves, and has greatly development potentiality. Based on the high precision of tridimensional reservoir geological model, this study calculated the reserves of the Xinli-Xinbei oilfield by Petrel, which deal with the issue that the reserves parameters are difficult to correctly acquire when estimate complex reservoir's reserves in terms of traditional volume method. In addition, the achievement maps made by Petrel show the distribution of reserves more accurately. Consequently, the results indicated that application of Petrel in reserve estimation reflects the true nature of the reservoir more accurately and more objectively which can better be applied to oilfield development and adjustment.

Carbonate rocks typically exhibit strong heterogeneity and multi-bedding characteristics, which exert a significant impact on acidification performance. In this study, based on the dual-scale continuum model and the open-source software FMOT, we developed an acidification simulation program suitable for multi-layered rocks, and focused on investigating the influence laws of two representative characteristics—heterogeneity intensity and interlayer permeability difference—on acidification performance. The results show that heterogeneity intensity significantly affects the development morphology of wormholes in high- and low-permeability rocks: under low-heterogeneity intensity conditions, the wormhole morphology in both layers is close to a straight line; under high-heterogeneity intensity conditions, the wormhole morphology exhibits a dendritic shape. When the interlayer permeability difference is 40 mD, the acid breakthrough times of rocks under three heterogeneity intensities (Low, Medium, High) are [476 s, 463 s, 450 s], indicating that the higher the rock heterogeneity intensity, the faster the acid breakthrough speed. In terms of porosity increment, under this condition, the porosity increments of high-permeability rocks are [0.0952, 0.0921, 0.0868], while those of low-permeability rocks are [0.0321, 0.0308, 0.0297]. It is evident that the acidizing effect of high-permeability rocks is significantly superior to that of low-permeability rocks. A further analysis of the influence of interlayer permeability difference shows that reducing the interlayer permeability difference significantly slows down the acid breakthrough speed of rocks, while weakening the acidizing effect of high-permeability rocks and enhancing that of low-permeability rocks; conversely, increasing the interlayer permeability difference accelerates the acid breakthrough of rocks, strengthens the acidizing effect of high-permeability rocks, and inhibits that of low-permeability rocks.

Carbonate reservoirs are typically characterized by well-developed natural fractures, and complex fracture-network geometries can significantly affect the effectiveness and efficiency of acidizing. In this study, a numerical simulation program for acidizing reactive transport in fractured carbonate reservoirs was developed based on a dual-continuum theory coupled with an Embedded Discrete Fracture Model. By decoupling complex fracture characteristics, we systematically investigated the controlling mechanisms of fracture dip angle and feature length ratio (FLR) on wormhole evolution and acidizing efficiency. The results show that fractures with small dip angles favor the development of the main wormhole trunk, whereas fractures with large dip angles redirect wormhole growth and promote the formation of complex branches. Under low FLR conditions, wormhole propagation is primarily governed by matrix heterogeneity, while a higher FLR markedly enhances the influence of fracture dip angle on overall wormhole development. The response of acid breakthrough volume (${\mathrm{PV}}_{\mathrm{BT}}$) to dip angle is strongly regulated by FLR. When FLR < 0.2, ${\mathrm{PV}}_{\mathrm{BT}}$ first increases and then decreases with dip angle, reaching a maximum at 45°, whereas for FLR > 0.2, ${\mathrm{PV}}_{\mathrm{BT}}$ increases approximately linearly with dip angle, indicating a substantial reduction in breakthrough efficiency. This study provides a theoretical basis for optimizing acidizing treatments in heterogeneous fractured carbonate reservoirs.