Optimization Design of CO₂ Pre-Pad Energized Fracturing for Horizontal Wells in Shale Oil Reservoirs: A Case Study of the Ordos Basin

An improved recovery technique using carbon dioxide (CO₂) pre-pad energized fracturing is presented to address the issue of low recovery in depleted development of shale reservoirs in the Ordos Basin. This study quantitatively evaluates the effect of CO₂ pre-pad energized fracturing under different engineering and geological parameters. The geological model of the target block was created in GOHFER using field logging data from the Ordos Basin oilfield. By coupling the reservoir simulator CMG, a three-dimensional wellsitescale long horizontal mechanism model was established, considering the artificial hydraulic fracture model. The influence of engineering parameters and geological parameters on CO₂ distribution was quantitatively evaluated. According to the outcomes of the simulation, the production potential of shale oil reservoirs can be significantly increased by using the CO₂ pre-pad energized fracturing development method. Important engineering factors affecting the stimulation include the CO₂ injection volume and soaking time, and the geological factors include the porosity, permeability, and layering. When the injection amount reaches a certain level, the growth of CO₂ sweep area decreases. With the increase of immersion time, the CO₂ sweep range gradually increases. Reservoir porosity and permeability affect CO₂ sweep in the lateral direction. Considering the front slick water fracturing fractures, the impact on the CO₂ sweep range is not apparent. Combined with GOHFER and CMG numerical simulation software, this study can realize the refined description of reservoirs considering artificial hydraulic fracture networks. According to the CO₂ injection range, the effect of CO₂ pre-pad energized fracturing under different engineering and geological conditions can be quantitatively evaluated. This study can be used as a reference CO₂ pre-pad energized fracturing of shale oil reservoirs in the Ordos basin.