Optimization of Acid Fracturing with Unified Fracture Design
- Arjun Ravikumar (University of Houston) | Matteo Marongiu-Porcu (Schlumberger) | Adrian Morales (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- Abu Dhabi International Petroleum Exhibition and Conference, 9-12 November, Abu Dhabi, UAE
- Publication Date
- Document Type
- Conference Paper
- 2015. Society of Petroleum Engineers
- 4 Facilities Design, Construction and Operation, 2.5.2 Fracturing Materials (Fluids, Proppant), 3 Production and Well Operations, 2.5.1 Fracture design and containment, 2.5 Hydraulic Fracturing, 4.1 Processing Systems and Design, 4.1.2 Separation and Treating, 2 Well completion
- Acid fracturing, Unified Fracture Design
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Acid fracturing is the most recognized and successful reservoir stimulation technique for conventional carbonate formations. Resulting fracture conductivity is the key parameter that controls final well productivity, while the competing diffusion and reaction phenomena control the "vital" acid coverage along the full areal extension of the fracture. However, not all reservoirs lend themselves to the same fracture geometry and conductivity, and this is where the "Unified Fracture Design" (UFD) approach is irreplaceable.
Classic fracture design optimization with the UFD approach involves the maximization of well productivity. For any mass of proppant to be injected as part of the treatment, the algorithm determines the unique fracture length and width (with height as a parasitic variable) that will provide the maximum productivity index.
In this paper we recast the UFD approach for specific acid fracturing applications, where the maximum productivity index is now determined as a function of the optimum fracture geometry determined for any volume of injected acid. The optimum fracture width profile is then obtained by solving the convection-diffusion equation for acid propagation, and subsequently used to study the required acid coverage through the fracture as a function of such optimum fracture width profile.
Acid reaction retardation plays a crucial role in ensuring proper acid coverage throughout the optimum fracture length, and this paper focuses on the two major reaction retardation fluid systems: Acid-Internal Emulsions (AIE) and gelled acids.
The workflow presented in this paper provides the basis for designing optimum acid fracturing treatments as a function of the volume of acid injected, the acid injection rate and the selected acid retardation method.
|File Size||1 MB||Number of Pages||17|
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