An analytical model for hydraulic fracturing in shallow bedrock formations

Area of Science:

• Geology
• Petroleum Engineering
• Hydraulic Fracturing

Background:

• Hydraulic fracturing is crucial for enhancing well productivity in low-permeability reservoirs.
• Accurate estimation of fracture geometry and transmissivity post-treatment is vital for optimizing well performance.
• Predictive models are needed to assess the potential benefits of hydraulic fracturing before field application.

Purpose of the Study:

• To propose and verify a theoretical method for estimating post-fracturing fracture size and transmissivity.
• To evaluate the potential hydraulic benefits of hydraulic fracturing prior to its application.
• To compare model-derived hydraulic apertures with those obtained from pumping test analyses.

Main Methods:

• Utilized pumping test data from two wells for method verification.
• Applied five different pumping test analysis methods, including the Papadopulos-Cooper and Gringarten-Ramey models.
• Employed the dos Santos (2008) model to simulate horizontal radial fracture propagation and estimate fracture geometry.

Main Results:

• Hydraulic fracturing significantly increased transmissivity, by over 46 times in one well and 285 times in another.
• Fractures were estimated to propagate up to 175 m with maximum apertures of 2.20 mm and hydraulic apertures of 0.30 mm.
• Analysis suggests hydraulic fracturing expanded existing fractures rather than creating new ones.

Conclusions:

• The proposed theoretical method accurately estimates post-fracturing fracture geometry and transmissivity.
• The methodology provides valuable pre-treatment insights into potential well yield improvements from hydraulic fracturing.
• Pumping test data and hydraulic fracturing models yield comparable hydraulic aperture results, validating the approach.