Hydraulic fracturing technology is relatively mature in North America, but under complex geological conditions, such as those in China, the application of this technology still faces great challenges. At present, techniques for the numerical simulation of hydraulic fracture networks are mainly based on the prediction of the fracture half-height and half-length, which cannot capture the heterogeneity of continental low-permeability sandstone reservoirs in China and the distribution of the asymmetric hydraulic fracture network present in them. Therefore, determining the asymmetric propagation mechanism of hydraulic fracture networks is very important for improving the recovery rates of continental reservoirs. In this paper, taking the Ordos Basin in China as an example, the spatial distribution of the stress field of a heterogeneous continental reservoir is precisely predicted by reservoir mechanical heterogeneity modeling. By using a microseismic monitoring method, the 3-D morphology of the hydraulic fracture network is determined. Through the coupling of multisource data, the frequency distributions of the determined in situ stress magnitudes in different hydraulic fracturing stages are obtained. The propagation direction of the hydraulic fracture network changes under the control of the horizontal stress difference (Δσ) and the presence of natural fractures. The smaller Δσ is, the greater the deflection of the hydraulic fracture propagation direction. The asymmetric propagation of these fractures is related to the frequency distribution of Δσ. As the frequency of Δσ approaches a normal distribution, the two wings of the hydraulic fracture network become basically equal in length, and as Δσ deviates more from a normal distribution, the difference between the two wings of the hydraulic fracture network increases. These research results will provide new insight for modeling, exploring, and developing continental reservoirs.

A transfer zone is a kind of structure that is produced to conserve deformation of a fault structure on both sides. Increasing numbers of transfer zones are being identified in rift basins, which are areas of petroleum accumulation and potential exploration targets. This paper provides a numerical simulation method for the genesis and development of transfer zones based on geomechanical modeling. On the basis of three-dimensional (3-D) seismic interpretation, using the Tongcheng fault as an example, the fault activity parameter and fault activity intensity index were established to quantitatively characterize the difference in fault activity on the two sides of a transfer zone. A geomechanical model was developed for a transfer zone in a rift basin, and the structural characteristics and genetic mechanism of a convergent fault were studied using paleostress and strain numerical simulations. Affected by different movements of boundary faults and basement faults, the evolution of the Tongcheng fault can be divided into three stages: (1) during the Funing period, which was the main development period of compound transfer faults, the activity, stress, and strain of the fault blocks on either side of the Tongcheng fault were obviously different; (2) during the Dainan period, which was the development stage of inherited compound transfer faults, the northern part of the Tongcheng area underwent local compression, and the T3 anticline began to form; and (3) during the Sanduo period, the Tongcheng fault experienced right-lateral strike-slip activity, where the activity showed two stages of change, first increasing and then decreasing, and the Tongcheng fault anticline developed. The superposition of multiple complex tectonic movements produced a transfer zone that has both strike-slip and extensional fault properties. The geomechanical model in this paper provides important insights for analyzing the evolution of transfer zones in rift basins.

Lower order faults (LOFs) are characterized by small‐scale, strong concealment and difficult to identify in seismic data, which affects the accuracy of LOF interpretation. Due to the quality of the seismic data in the M35 fault block of the Gaoyou sag, Subei basin, the direction of the LOFs cannot be accurately identified, leading to the unclear relationship between the injection and production wells in the local oil fields and affecting the development of the remaining oil. In this paper, the formation mechanism of LOFs in the M35 fault block is determined from analysis of the fault activity and tectonic evolution, and a finite element geomechanical model is established to simulate the paleostress field during the formation of the LOFs. Based on the relationship between the areal density of LOFs and the stress parameters, the regions of LOF development are predicted by the minimum principal stress, the maximum and minimum principal stress difference (Δσ), normal stress (σ_n), and the strain energy density; the shear stresses are used to predict the dip direction of the LOFs. Through the coordinate system transformation of the principal stress directions, the strikes of the LOFs are quantitatively predicted. Finally, the reliability of the prediction results is verified by the latest structural map of the M35 fault block. The method proposed in this paper can be widely applied to the quantitative prediction of multiple parameters of LOFs in complex fault blocks.