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To wrap up our latest series of posts on non-matrix features in carbonate reservoirs... a few pictures of how these features look like on borehole image logs. Enjoy! Upper panel: Examples of nonmatrix features interpreted from acoustic borehole image logs (amplitude). Dark colors correspond to low amplitude values interpreted to be open pore space. To the left of each image log the filled texture represents borehole elongations; to the right, a gray bar highlights the interval of interest. (A, B) Bed-bounded joints in ~10- to 20-cm-thick silicified layers; note that silicified layers occur as high amplitude events; (C) 60 dip natural open fracture represented by a continuous sinusoid; (D) 80 dip open natural fracture with irregular nonmatching walls and associated type IIIa losses. Type losses as defined by Fernandez-Ibanez et al. (2019b). BS: bit size; CALI: caliper Lower panel:  Examples of nonmatrix features interpreted from acoustic borehole image logs (amplitude). Dark colors correspond to low amplitude values interpreted to be open pore space. To the left of each image log, the filled texture represents borehole enlargements as measured by single arm mechanical caliper; to the right, a gray bar highlights the interval of interest. (A) Millimeter-scale touching vugs; (B) centimeter-scale vugs along bedding planes; (C) centimeter-scale vugs and faint fractures in silicified interval; (D) centimeter-scale vugs. BS: bit size; CALI: caliper. Figure from Fernandez-Ibanez et al. (2022). © AAPG reprinted by permission of the AAPG whose permission is required for further use. #ReservoirEngineering #Carbonates #Geomechanics #PetroleumGeology #NonMatrixPorosity #ExcessPermeability #OilAndGas #Subsurfacealliance #presalt #luconia #indonesia #malaysia

🧑🏭 Non-Matrix Porosity and Excess Permeability in Carbonates In carbonate reservoirs, non-matrix features—such as fractures, vugs, and karst systems—play a crucial role in enhancing porosity and permeability, often driving excess permeability. These features can create complex flow pathways that go beyond the primary rock matrix, significantly influencing hydrocarbon storage and recovery. 🔹 Fractures provide secondary permeability, offering rapid fluid flow pathways. However, they deplete quickly, often leading to a decline in production once the hydrocarbons in the fractures are drained. 🔹 Vugs add significant storage capacity, and their contribution to permeability depends on their connectivity to fractures. 🔹 Karst Systems offer extremely high permeability in localized zones but can lead to unpredictable flow patterns. Reservoirs with extensive karst systems may exhibit erratic production behavior, requiring specialized strategies for optimized recovery. 🛠️ Why It Matters for Reservoir Engineering: These non-matrix features create excess permeability, allowing hydrocarbons to flow more freely than through the rock matrix alone. Understanding the contribution of these features to a reservoir’s porosity and flow dynamics is crucial for developing accurate reservoir models and enhancing hydrocarbon recovery. Figure: Nonmatrix and excess permeability. (A) Ternary conceptual diagram showing host rock (in black) and porosity (in white) com ponents of a dual-porosity carbonate pore system. Concentric circles (not to scale) conceptually represent pore system permeability investigated by a routine core plug analysis (blue) versus a well test (green). (B) Box and whisker plots showing ranges of measured permeability from routine core plug analysis for two pre-Salt wells (in blue) and effective permeability derived from well test (drill-stem tests and production tests) pressure transient analysis (green) conducted on multiple wells in the pre-Salt. Lines extending from the boxes (whiskers) represent variability outside the upper and lower quartiles, excluding outliers. The median is represented by the horizontal line in the box. Excess permeability is defined as the difference between permeability based on core analysis data and effective permeability calculated from well test pressure transient analysis. n: number of samples. Figure from Fernandez-Ibanez et al. (2022). © AAPG reprinted by permission of the AAPG whose permission is required for further use. #ReservoirEngineering #Carbonates #Geomechanics #PetroleumGeology #NonMatrixPorosity #ExcessPermeability #OilAndGas #Subsurfacealliance #presalt

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🌍 Unlocking Reservoir Insights: Brazil Pre-Salt Carbonates 🛢️ As a follow up to our prior post, in this paper, authors Jordan Mimoun and Fermin Fernandez-Ibañez, PhD explore the value of well tests for non-matrix characterization. In the complex world of carbonate reservoirs, understanding the dynamics of non-matrix features like fractures and vugs is key to optimizing reservoir performance. Our latest study in the Journal of Petroleum Science and Engineering presents a comprehensive catalog of diagnostic signatures from pressure transient analysis (PTA) in the prolific Brazil Pre-Salt formations. 🔑 Key Takeaways: ✔️ We identified eight diagnostic signatures that transcend traditional models, helping to reveal the presence and extent of excess permeability. The study highlights how integrating data from 152 well tests with static and dynamic sources can significantly enhance reservoir characterization. ✔️ These signatures will guide subsurface teams in framing well-test objectives, enabling more accurate reservoir simulations and improving field development strategies. ✔️ This work has implications beyond the Brazil Pre-Salt, offering valuable insights into carbonate reservoirs worldwide. Dive deeper into how dual-porosity systems can enhance well productivity and inform smarter investment decisions. Figure shows PTA diagnostic signatures associated to different geologic concepts for type and location of non-matrix features. Mimoun and Fernandez-Ibanez (2022). Thank you for your comments on our prior post, Omar Rashid, Jack Steen, John Richey, Jonathan Brown, Razik Shaikh, Irma P., Juan I. Soto. Hope this is equally relevant to you all. #ReservoirEngineering #PTA #BrazilPreSalt #OilandGas #Carbonates #SubsurfaceAlliance

🚨 Reference paper for those working on carbonate reservoirs 🚨 📄 Interesting research paper by Fermin Fernandez-Ibañez, PhD, Gareth Jones, Jordan Mimoun, Melanie Bowen, toni simo, Virginia Marcon, and William L. Esch, which delves into excess permeability in Brazil's Pre-Salt carbonate reservoirs. 🛠️The study examines how nonmatrix features—like fractures, vugs, and caves—can influence reservoir performance, sometimes increasing permeability by up to two orders of magnitude compared to the matrix. These features can cause early water breakthrough or injectivity challenges, highlighting the critical importance of characterizing them early for more effective reservoir management. The authors present a multidisciplinary workflow that integrates core, wireline logs, well tests, and drilling losses to diagnose and quantify excess permeability. They apply this approach to data from the Brazilian Pre-Salt fields, providing valuable insights into the types and distribution of nonmatrix features and their dynamic impact. 💡 The results are vital for improving reservoir models, particularly in complex carbonate systems, and reducing uncertainties in field development strategies. This study is a game-changer for those working in carbonate reservoir characterization and development planning. 🖼️ Figure: Schematic conceptual cross section (not to scale) of the pre-Salt reservoirs illustrating main type of concepts for nonmatrix and excess permeability under present-day reservoir conditions. The inset on the figure shows an idealized stratigraphic section at the core scale. Numbers on the figure point to locations for different excess permeability concepts (cf. summary chart on Figure 17): (1) millimeter-scale touching vugs; (2) bed-bounded fractures; (3) fault zones; (4) fractures and faults because of margin instability; (5) freshwater lens and meteoric exposure-related caves; (6) slope breccias. BDF 5 boundstone-dominated fabric; GDF 5 grain stone dominated fabric; MDF 5 mudstone-dominated fabric Figure from Fernandez-Ibanez et al. (2022). © AAPG reprinted by permission of the AAPG whose permission is required for further use. #CarbonateReservoirs #ExcessPermeability #PreSalt #ReservoirEngineering #OilAndGas #Geomechanics #WellTesting #ReservoirCharacterization #BrazilOilAndGas #FieldDevelopment #SubsurfaceAlliance

🌱 Advancing Geothermal Energy: Key Findings from EGS Research 🌱 A recent study by Lei et al (2023) explores the performance of Enhanced Geothermal Systems (EGS), focusing on fracture network complexity and thermo-hydro-mechanical (THM) processes. 🔑 Key Insights: Fracture Networks Shape Efficiency: The geometry and orientation of natural fractures are crucial for optimizing heat extraction. Horizontal fractures boost thermal recovery, while vertical ones influence fluid flow and injection pressure. Hydraulic Fracture Aperture Optimization: Maintaining apertures between 0.5–1.0 mm in hydraulic fractures balances fluid transport and heat extraction, ensuring efficient geothermal performance. Injection Rate Impact: Higher injection rates can enhance heat output but require careful management to avoid excess stress and pressure on the reservoir. These findings provide valuable insights for optimizing geothermal extraction and advancing sustainable energy solutions. Authored by Zhihong Lei, Yulong Zhang, Qiliang Cui, and Yu Shi, this research contributes to the growing body of knowledge for clean energy innovation. 🌍💡 Figure from Lei et al. (2023) licensed under CC BY 4.0 - Scientific Reports #GeothermalEnergy #RenewableEnergy #Sustainability #Innovation #CleanEnergy

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🌍 Understanding Induced Seismicity: A Growing Concern 🌍 In recent years, induced seismicity has become a significant topic of discussion among geologists, engineers, and environmentalists. Induced seismicity refers to earthquakes triggered by human activities, such as: Mining Reservoir-induced seismicity from large dams Geothermal energy extraction Hydraulic fracturing (fracking) Wastewater injection While natural seismic events are part of Earth’s dynamic system, the rise of human activities that interfere with geological formations has led to an increase in small to moderate seismic events, particularly in regions not typically known for seismic activity. 🔍 Why does this matter? The risks associated with induced seismicity include damage to infrastructure, potential environmental hazards, and public safety concerns. Understanding the science behind these events can help industries adopt safer practices and implement mitigation strategies. #Seismicity #Geology #Earthquake #InducedSeismicity #EnvironmentalSafety #Sustainability #Geophysics #EnergyIndustry #HydraulicFracturing #GeothermalEnergy Figure from Kivi, I.R., Boyet, A., Wu, H., Walter, L., Hanson-Hedgecock, S., Parisio, F. and Vilarrasa, V., 2023. Global physics-based database of injection-induced seismicity. Earth System Science Data Discussions, pp.1-33 - Licensed under CC BY 4.0

Great visuals on stress distribution around faults from the paper by Parisio et al (2019) in their work assessing the risks related in long term re-injection in supercritical geothermal systems. Some of the paper highlights: ✔ Supercritical geothermal systems are appealing sources of sustainable and carbon free energy located in volcanic areas. ✔ Despite their attractiveness, several important questions regarding safe exploitation remain open. ✔ Thermally induced stress and strain dominates the geomechanically response of super critical systems, compared with the effect of pore pressure related instabilities and greatly enhance seismicity during cold water re-injection. Figure from Parisio et al. (2019) licensed under CC BY 4.0. Fault reactivation and reservoir stability. Coulomb Failure Stress changes (ΔCFS) after 25 years for the cold water (a) and isothermal injection, (b) cases and Drucker-Prager mobilized failure ratio (MDP) after 25 years for the cold water (c) and isothermal injection (d) cases. Negative values of MDP imply σ0 m c0= tan ϕ: hydrostatic tension failure will be reached, and tensile fractures will be likely to appear, as highlighted by the schematic representation in the inset in c. #geomechanics #subsurfacealliance #faults #inducedseismicity #geothermal

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