Quantitative Prediction of Tectonic Fracture in the Fourth Member of Denying Formation Reservoir, Shehong-Yanting Block, Penglai Gas Field

The fourth member of the Dengying Formation (Deng4) in the Shehong-Yanting Block, Penglai Gas Field, has emerged as a critical hydrocarbon exploration in recent years, which is characterized by ultra-deep burial depths, extremely low porosity and permeability, and pronounced heterogeneity. Tectonic fractures are key factors governing the production of ultra-deep carbonate reservoirs. To obtain a quantitative forecast of the distribution of tectonic fractures in this area. Outcrops, drilling cores, thin sections, and image logs were comprehensively used to determine tectonic fracture characteristics. Numerically, finite element (FE) simulations were conducted to construct three-dimensional (3D) paleotectonic and current stress fields, guided by the geological structure interpretation, rock mechanics tests, and acoustic emission measurements. Simultaneously, the spatial distribution of fracture parameters was quantitatively constrained through 3D geomechanical simulations based on rock failure criteria, strain energy theory, and fracture occurrence evolution. The results indicated that: (1) Shear fractures mainly dominate the Deng4 reservoir, Oblique fractures are concentrated in the southeastern structural highs, while high-angle or vertical fractures are typically found near faults. (2) Three primary fracture orientations are identified: Oblique fractures predominantly striking NNW-SSE, high-angle fractures exhibiting bimodal orientations of NW-SE and NE-SW. (3) Fracture linear density ranges from 0.5 to 2.4 1/m and exhibits a decreasing trend toward the southeast, which is inversely correlated with fracture aperture values (ranges from 0.18 to 18.35 μm), Fracture porosity varying between 0.001% and 0.0043%, shows limited variation. (4) There are distinct differences in fracture parameters across fault cores, near-fault zones, and non-fault areas. The predicted results align strongly with field measurements, confirming that fracture dip angle, aperture, and porosity significantly influence gas well productivity. The developed geomechanical methodology, which integrates fracture characterization with tectonic evolution analysis, provides practical guidance for well location deployment, trajectory optimization, and acid fracturing design in the study area.