*2.1. Materials*

The six laminated samples studied in this work were collected from the Chang 8 to Chang 6 member, the principal hydrocarbon-accumulating intervals in the Upper Triassic Yanchang Formation of the southern Ordos Basin. These samples could represent the di fferent petrophysical facies in the delta-lacustrine environment. Core-1 and Core-2 are the tight siltstone- and sandstone-deposited distributary channel facies in tractive current hydrodynamic conditions. Core-1 represents the tight channel siltstone with the inconspicuous lamina, i.e., micro-cross-bedding lamina. Core-2 represents the tight channel sandstone with the macro-cross-bedding lamina. Core-3 represents the tight argillaceous siltstone with the horizontal lamina. Core-4 and Core-5 represent the tight sheet siltstone with the obvious lamina, i.e., wavy or lenticular lamina. Core-6 represents the tight siltstone deposited in the lacustrine turbidite fan facies with slumping-induced deformation lamina. Generally, the six laminated cores are typical representatives for all tight sandstone oil reservoirs, especially for the tight sandstone oil reservoir of the Ordos Basin in China.

#### *2.2. Triaxial Compression Tests*

To indicate the heterogeneity of laminated rocks and lamina lithofacies in the geo-models, we tested 18 column samples with di fferent lamina angles from the six di fferent laminated cores in triaxial compression experiments. The triaxial compression tests were performed with an RTR apparatus under a 20 MPa confining pressure. The 20 MPa approximates the underground pressure at a 2000 m depth, so it can be used to simulate real geological conditions. Sample treatment was conducted in strict accordance with the International Society of Rock Mechanics (ISRM) rock triaxial test requirements and the China National Standard (GB/T 50266-99).

#### *2.3. Finite Element Simulation*

Finite element simulation was performed in the statics module of the ANSYS workbench. In this method, the geological model is divided into di fferent specific elements linked to nodes. In addition, the approximate value of the node displacement could be calculated using the element functions in the equilibrium state. Based on the computed result, we can obtain the stress and strain of these elements [48–52]. For the geological model building work, it is generally assumed that the stress and strain of the shallow crust rocks are linearly dependent during the period of rock elastic deformation [53,54]. In this study, the principle of the finite element approach is composed of the following three relationships: (1) The strain–displacement relationship; (2) strain–stress relationship; and (3) stress–external force relationship. The principle and its detailed explanations can be found in our previous study [17].

In this work, to calculate the boundary stress conditions for the finite element simulation, we modified the Newberry formula to make it more suitable for the tensional and compressive stress fields. Although the rock spatial stress computed by the Newberry formula is appropriate for the tight reservoir simulation [55], the equation is only defined in compressive stress fields and leaves the tensional stress field out of consideration [56–58]. Hence, the positive sign of the compressive stress field in the Newberry formula is changed to a negative sign for the tensional stress field. In addition, this work constrained the calculative process of the boundary stress state, based on the assumption that the 3D geo-model can be regarded as a point mass with the corresponding well burial history area. In this way, we can calculate the boundary stress state by combining the regional tectonic stress, tectonic direction, and rock density. The detailed modification of the Newberry formula and the calculative process of the boundary stress state can also be found in our previous study [17].
