Finite Element Simulation of Multi-Scale Bedding Fractures in Tight Sandstone Oil Reservoir

Abstract

Multi-scale bedding fractures, i.e., km-scale regional bedding fractures and cm-scale lamina-induced fractures, have been the focus of unconventional oil and gas exploration and play an important role in resource exploration and drilling practice for tight oil and gas. It is challenging to conduct numerical simulations of bedding fractures due to the strong heterogeneity without a proper mechanical criterion to predict failure behaviors. This research modified the Tien–Kuo (T–K) criterion by using four critical parameters (i.e., the maximum principal stress (σ1), minimum principal stress (σ3), lamina angle (θ), and lamina friction coefficient (μlamina)). The modified criterion was compared to other bedding failure criteria to make a rational finite element simulation constrained by the four variables. This work conducted triaxial compression tests of 18 column samples with different lamina angles to verify the modified rock failure criterion, which contributes to the simulation work on the multi-scale bedding fractures in the statics module of the ANSYS workbench. The cm-scale laminated rock samples and the km-scale Yanchang Formation in the Ordos Basin were included in the multi-scale geo-models. The simulated results indicate that stress is prone to concentrate on lamina when the lamina angle is in an effective range. The low-angle lamina always induces fractures in an open state with bigger failure apertures, while the medium-angle lamina tends to induce fractures in a shear sliding trend. In addition, the regional bedding fractures of the Yanchang Formation in the Himalayan tectonic period tend to propagate under the conditions of lower maximum principal stress, higher minimum principal stress, and larger stratigraphic dip.

Pore Structure Characteristics of Tight Carbonate Reservoir in Qingxi Sag, Jiuquan Basin

“…The top is occupied with gray mudstone and shale with different thicknesses and interbedded deposits. The strata developed with horizontal and trough crossing bedding [12,41] (Figure 2).…”

Impact of the Short-Circuit Current Value on the Operation of Overhead Connections in High-Voltage Power Stations

“…Therefore, during the design phase, extreme short-circuit conditions where, for example, a very high short-circuit current value appears, as in the case of a three-phase short circuit with a longer duration than normal, can be considered as a basis for determining the operating parameters of the designed equipment. In the case of facilities such as substations, short-circuit conditions affect the selection of virtually all equipment, including the selection of structures and foundations, which may not seem so obvious, since these are not electrical devices [20][21][22][23][24]. A general short-circuit current waveform is shown in Figure 1 [25].…”

Calculations of Electrodynamic Forces in Three-Phase Asymmetric Busbar System with the Use of FEM

“…Other authors used experimental methods to check the reliability of busbar contacts and predicted the contact state on the basis of theoretical models [19,20]. Therefore, considering the effects of electrodynamic forces, temperature rise, and other factors, such as mechanical strength and the effect of a short circuit conditions on the busbar is analyzed [21][22][23].…”