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

Abstract

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 wellsite-scale 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.