*Article* **Three-Dimensional Structural Modeling (3D SM) and Joint Geophysical Characterization (JGC) of Hydrocarbon Reservoir**

**Baoyi Zhang <sup>1</sup> , Yongqiang Tong <sup>1</sup> , Jiangfeng Du <sup>2</sup> , Shafqat Hussain <sup>3</sup> , Zhengwen Jiang <sup>1</sup> , Shahzad Ali <sup>3</sup> , Ikram Ali <sup>3</sup> , Majid Khan <sup>4</sup> and Umair Khan 1,\***


**Abstract:** A complex structural geology generally leads to significant consequences for hydrocarbon reservoir exploration. Despite many existing wells in the Kadanwari field, Middle Indus Basin (MIB), Pakistan, the depositional environment of the early Cretaceous stratigraphic sequence is still poorly understood, and this has implications for regional geology as well as economic significance. To improve our understanding of the depositional environment of complex heterogeneous reservoirs and their associated 3D stratigraphic architecture, the spatial distribution of facies and properties, and the hydrocarbon prospects, a new methodology of three-dimensional structural modeling (3D SM) and joint geophysical characterization (JGC) is introduced in this research using 3D seismic and well logs data. 3D SM reveals that the field in question experienced multiple stages of complex deformation dominated by an NW to SW normal fault system, high relief horsts, and half-graben and graben structures. Moreover, 3D SM and fault system models (FSMs) show that the middle part of the sequence underwent greater deformation compared to the areas surrounding the major faults, with predominant one oriented S30◦–45◦ E and N25◦–35◦ W; with the azimuth at 148◦–170◦ and 318◦–345◦ ; and with the minimum (28◦ ), mean (62◦ ), and maximum (90◦ ) dip angles. The applied variance edge attribute better portrays the inconsistencies in the seismic data associated with faulting, validating seismic interpretation. The high amplitude and loss of frequency anomalies of the sweetness and root mean square (RMS) attributes indicate gas-saturated sand. In contrast, the relatively low-amplitude and high-frequency anomalies indicate sandy shale, shale, and pro-delta facies. The petrophysical modeling results show that the E sand interval exhibits high effective porosity (∅*eff*) and hydrocarbon saturation (*Shc*) compared to the G sand interval. The average petrophysical properties we identified, such as volume of shale (*Vshale*), average porosity (∅*avg*), ∅*eff*, water saturation (*SW*), and the *Shc* of the E sand interval, were 30.5%, 17.4%, 12.2%, 33.2% and, 70.01%, respectively. The findings of this study can help better understand the reservoir's structural and stratigraphic characteristics, the spatial distribution of associated facies, and petrophysical properties for reliable reservoir characterization.

**Keywords:** 3D structural modeling (3D SM); 3D fault system models (FSMs); seismic attribute models; reservoir properties; facies; hydrocarbon-bearing zones
