## 1 Introduction  
In recent years, China's rapid economic development has been accompanied by a sharp increase in the consumption of oil and gas, leading to a growing dependence on imports for these resources. In 2018, the figures for oil and natural gas imports reached 69.8% and 45.3%, respectively [1]. The urgent need to discover new types of oil and gas resources, coupled with the necessity for theoretical and technological breakthroughs to bolster domestic production, has become an industry consensus. Among the new resource types, shale oil stands out as one of the most viable options to explore. The swift advancement in oil and gas geology theory [2; 3; 4; 5; 6] and horizontal well volume fracturing technology [7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18] has positioned shale oil as a primary target for unconventional oil and gas exploration and exploitation [19; 20; 21; 22]. Its vast reserves have secured a pivotal role in global energy strategies [23; 24]. Thus, achieving a breakthrough in China's shale oil research is of strategic importance, not only for maintaining the industry's technical leadership but also for safeguarding national energy security [25; 26].  
The Ordos, Junggar, Bohai Bay, and Songliao basins are endowed with substantial shale oil resources [27; 28; 29]. According to the CNPC's assessment in 2016, the total shale oil reserves in these areas have exceeded 14.5 billion tons. However, due to the relatively late start of shale oil exploration in China, it is faced with many difficulties and high costs in the development process. At present, only parts of the Junggar Basin and Ordos Basin have achieved breakthrough progress [30; 31]. With the continuous improvement of shale oil exploitation technology in China, shale oil is expected to play a key role in China's future energy supply system [32; 33; 34; 35].  
In this paper, the geological characteristics and distribution of shale oil in Member 7 (Chang 7) of the Yanchang Formation in the southern Heshui area of the Ordos Basin are deeply studied and analyzed, and the geological probability surface is obtained by comparing the thickness of sand and mud bodies with that of the target layer. By comparing the thickness of sand and mud bodies with that of the target layer, a geological probability surface is derived. Utilizing multiple information co-constraints, a reservoir attribute model is established based on the lithofacies model and lithofacies control through sequential indicator simulation and sequential Gaussian stochastic simulation, thereby providing a stable and reliable static model. To enhance the accuracy of the geological model further, this study integrates the sedimentary environment of the Ordos Basin. Guided by the stratigraphic structure pattern and using the marker layer, sedimentary cycle, and lithology combination as the basis for comparison, detailed stratigraphic correlation is conducted, and a refined isochronous stratigraphic framework is established. This approach adheres to the principle of isochronous modeling and employs a comprehensive combination of deterministic and stochastic modeling techniques to improve the precision of geological modeling.  
Overall, this study posits that the shale oil in the Chang 7 member of the Yanchang Formation in the southern Heshui area of the Ordos Basin could potentially stimulate an increase in oil and natural gas storage and production within the basin, heralding a new model for exploration and development. Furthermore, the breakthrough achievements made by the Changqing Oilfield in shale oil exploration and development of the Chang 7 block have not only bolstered the company's confidence in further exploration but have also played a critically important role in guiding extensive exploration and development efforts for continental shale oil across China. A systematic collation of the core technologies in shale oil exploration and development within the Chang 7 block is expected to offer valuable insights for the broader endeavor of shale oil exploration and development in China.