In continental shale reservoirs, the complex construction, limited fracture height and small stimulated volumes result in poor adaptability and low recovery efficiency when traditional shale fracturing techniques are used. This work introduces the recent improvements in fracturing technology developed for continental shale reservoirs and highlights the challenges and technological innovations required to enhance oil recovery. Lately, several innovative fracturing techniques have been developed that are suitable for the efficient development of continental shale reservoirs. These new proposed fracturing techniques primarily enhance the recovery of continental shale reservoirs by optimizing fracture creation and expansion, improving permeability, or increasing the stimulated reservoir volume. Several practical applications of these technologies in complex fault shale reservoirs, matrix-dominated shale reservoirs and complex structural shale reservoirs have demonstrated significant improvements in oil production. However, further research is needed with respect to determining the technical parameter boundaries for fracturing in different depressions and reducing costs, in order to refine these technologies and advance the efficient development of continental shale resources.

Subsequent CO₂ injection can enhance oil recovery and achieve carbon sequestration in shale reservoirs, which is crucial for energy sustainability and environmental protection. However, for continental sedimentary shale oil, the development process must consider the multiscale matrix-fracture structure and the impact of heterogeneous wettability on fluid-solid interactions. Moreover, the mechanisms of CO₂ miscibility and interfacial behavior in post-fracturing reservoirs remain unclear. In this study, a laminated shale micro-model with fracture based on scanning electron microscopy observations was designed, and the process of fracturing fluid flowback and subsequent CO₂ huff-n-puff were simulated. Results showed that forced imbibition primarily affects limestone layers, while spontaneous imbibition affects mudstone layers, contributing 89.3% and 10.7% to the affected area, respectively. The oil recovery mechanism of CO₂ is mainly influenced by pressure, transfer from displacement-carry at low pressure to dissolution-extraction, and eventually to diffusion-extraction in the miscible state. Additionally, before reaching miscibility, Taylor dispersion, Kelvin-Helmholtz instability, Rayleigh-Taylor instability, and Marangoni effects occur at the oil-CO₂ interface, leading to interfacial turbulent instability. Lastly, water huff-n-puff produces membrane and isolated droplet residual oil, while immiscible CO₂ breaks cluster residual oil into columnar residual oil. Miscible CO₂ enhances the recovery of various residual oils, improving oil recovery and facilitating CO₂ storage. This study provides insights for post-fracturing CO₂ huff-n-puff development of continental sedimentary shale oil and CO₂ sequestration, promoting energy utilization and environmental improvement.

Physicochemical forces exert non-neligible effects on the migration of micro-particles in channels. Experiments, analytical and non-resolved computational fluid dynamics models have failed to decipher the dynamic behaviors of these particles when carried by fluid flow. In this paper, particle-scale numerical simulation is conducted to study the adhesive micro-particle migration process during duct flow in channels with a large characteristic dimension ratio and those with relatively small such ratio based on the coupled lattice Boltzmann method-discrete element method. The interaction between particle and fluid flow is dealt with by the immersed moving boundary condition. For micro-particle migration in duct flow, the effects of hydrodynamic force, adhesive force and particle concentration on the aggregation of particles are investigated. Based on the concept of hydrodynamic and adhesive force ratio, a stable aggregation distribution map is proposed to help analyze the distribution and size of the formed agglomerates. For micro-particle migration in channels with small characteristic dimension ratio, the general particle migration process is analyzed, which includes single particle retention, followed by particle capture, and the migration of large agglomerates. It is concluded that two factors accelerate single particle retention in a curved channel. Moreover, it is established that higher fluid flow rate facilitates the formation of large and compact agglomerate, and blockage by this can cause severe damage to the conductivity of the channel.

Reorientation of fractures and high production improvement are observed and illustrated by fields and theoretical researches. During the refracturing treatments, it is important to get familiar with the enhanced oil recovery mechanics of fracture reorientation and distribution of residual oil. Mechanisms of fracture reorientation are discussed in order to design the parameters of reoriented fractures in numerical simulation. To furtherly evaluate the oil recovery of different angles of reoriented fractures, geological and numerical models are simulated using data of the actual reservoir with rhombus inverted nine spot well pattern, different angles of reoriented fracture are designed for both corner and edge wells to obtain the enhanced oil recovery. Results show that potential of production increase is highly impacted by the well pattern and angles of fractures and meanwhile impacted by distribution of residual oil and formation properties. Oil enhancement potential is significantly different with fracture reorientation angles in refracturing treatment: cumulative produced oil for corner wells is symmetrical around the angle of 0° and reaches the highest at the angles of positive and negative 23°; for the edge wells, it is also symmetrical around the angle of 0° while reaches the highest cumulative oil at the angles of positive and negative 90°. The difference shows that optimal angles exist for reoriented fractures during refracturing design and with proper induced reoriented fractures, more oil will be recovered for field restimulation treatments.