Fracture Barrier Identification in Unconventional Formation Introducing a New Fracture Barrier Index from Conventional Logs: Vaca Muerta Case

Abstract

The initial high cost of exploitation of the sustained, increasingly growing development of unconventional resources in Argentina has resulted in concentrating all efforts to increase well productivity while reducing construction and completion costs. The optimization of hydraulic fracture (HF) treatments is vitally important. It is the primary strategy used to achieve an optimal reservoir drainage area, consequently characterizing the fracture geometry, including the height, for the continuous improvement of HF treatment and planning. Several types of technologies and methodologies are used to estimate fracture height during and after a hydraulic stimulation treatment. These technologies can provide information about the fracture geometry and extension in the near-wellbore (NWB) and far-field areas. The determination of a reliable correlation between those methodologies represents a challenge as a result of formation complexity, heterogeneity, and limitations of evaluation technologies. It is well-known that some areas in the Vaca Muerta formation contain layers that can act as fracture barriers and are responsible for fracture containment. This paper presents a fast and simple methodology that uses conventional well logs [gamma ray (GR), sonic, and density] from pilot wells to identify potential fracture barriers. This approach establishes a means to evaluate the degree to which the rock will have the ability to control fracture height growth. This methodology was determined useful for planning perforation intervals or clusters placement, particularly in those formations with stress profile showing reduced stress contrast and, when complemented with geological information, this method also provides useful information for horizontal well trajectory. Case studies are provided to illustrate examples of the proposed fracture barrier index (FBI) being calibrated or compared to other fracture height assessment. Additionally, the benefits of adding this new approach to current methodologies and technologies to aid completion design optimization and decision making is discussed.

Numerical Simulation of Hydraulic Fracture Propagation on Multilayered Formation Using Limited Entry Fracturing Technique

“…Li et al, 2017 simulated multiple fracture propagation along the horizontal well, they demonstrated that a sufficiently large perforation pressure drop can counteract the stress shadowing among the multiple fractures and can help to equalize the length of multiple fractures [12]. However, the fracture mechanisms under the limited-entry technique for vertical well in multilayered formation is relatively rare, although limited entry fracturing is a great stimulation technique for vertical wells with a manageable degree of cost and risk [13][14][15]. It is worth noting that the fracture toughness parameter is an important parameter for hydraulic fracturing design.…”

Relationship between fissility, composition, rock fabric and reservoir properties in Vaca Muerta Formation (Neuquén Basin, Argentina): from outcrop to subsurface core data

“…Discontinuity and heterogeneity studies in the Vaca Muerta Formation at different scales have been published by Sagasti et al (2014), Stinco and Barredo (2014), Ortiz et al (2016), González Tomassini et al (2017, Boitnott et al (2018), Casala et al (2019). However, few studies address the role of the fissility planes in mudstones, the main rock type of Vaca Muerta Formation.…”