Mechanical stratigraphy and structural control of oil accumulations in fractured carbonates of the Irati Formation, Paraná Basin, Brazil
Open Access
- 1 January 2020
- journal article
- research article
- Published by FapUNIFESP (SciELO) in Brazilian Journal of Geology
Abstract
Fracturing analysis of low-permeability rocks as reservoir analogs have increased in recent years. The main mechanism involved in the development of secondary porosity in low-permeability, fine-grained limestones of the Irati Formation is fracturing. In these rocks, oil accumulates along fracture planes, vuggy porosity, microfractures, breccias, as well as bedding discontinuities. Joints represent the central element for oil migration and the connection between accumulation sites. Joints are unevenly distributed across the succession of rock types, where carbonate rocks have a much denser array of joints than shales and siltstones. From a mechanical stratigraphy point of view, limestones have a brittle behavior and constitute mechanical units. Ductile shale and siltstone are mechanical interfaces capable of blocking joint propagation. Joints running NW-SE are more effective in trespassing the mechanical interface and are, therefore, more persistent. Joints running NE-SW are less persistent because the ductile behavior of the first two shale beds above the limestone blocks their propagation. The spatial arrangement of regional NW-SE and NE-SW joints promoted reservoir connection, allowing oil migration and accumulation. The joints and oil migration (at least three phases) developed as a consequence of the Gondwana Breakup and are also associated with local pressure gradients.Keywords
This publication has 32 references indexed in Scilit:
- Carbonate rocks and petroleum reservoirs: a geological perspective from the industryGeological Society, London, Special Publications, 2012
- Evolution of fault zones in carbonates with mechanical stratigraphy – Insights from scale models using layered cohesive powderJournal of Structural Geology, 2010
- Integrated fracture prediction using sequence stratigraphy within a carbonate fault damage zone, Texas, USAJournal of Structural Geology, 2010
- Fractured reservoirs with fracture corridorsGeophysical Prospecting, 2010
- Origin and migration timing of hydrothermal fluids in sedimentary rocks of the Paraná Basin, South AmericaChemical Geology, 2006
- Mechanical stratigraphic controls on fracture patterns within carbonates and implications for groundwater flowSedimentary Geology, 2006
- A scale-independent approach to fracture intensity and average spacing measurementAAPG Bulletin, 2006
- Role of heterogeneity in elastic properties and layer thickness in the jointing of layered sedimentary rocksGeophysical Research Letters, 2003
- Prediction of macrofracture properties using microfracture information, Mesaverde Group sandstones, San Juan basin, New MexicoJournal of Structural Geology, 2000
- Variations in fracture system geometry and their implications for fluid flow in fractures hydrocarbon reservoirsPetroleum Geoscience, 1999