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Liquid saturation evaluation in organic-rich unconventional reservoirs: A comprehensive review

Abstract

Unconventional organic-rich reservoirs, including oil and gas shales, are the type of rocks located in the subsurface and bearing considerable hydrocarbon resources. Shale gas revolution that started in 2011 raised the question of gas and oil shales properties research all over the world. However, still one of the most critical questions on the subject is the problem of oil and water saturation evaluation in shale reservoirs. An expanded literature survey improved understanding of the current state of the problem, available solutions, including methods, and method-based workflows. Analysis of the obtained information revealed an absence of a universal technique to solve the problem. Application of multi-frequency nuclear magnetic resonance (NMR) coupled with an NMR rock core analyzer optimized for shales forms workflows providing the complete information on the type and volume of fluids present in the pore space of oil shales. The methods delivering incomplete (partial) information include retort analysis, Dean-Stark extraction, rock evaluation (Rock-Eval) pyrolysis, electrical resistivity, and dielectric permittivity measurements. This review aims to provide with comprehensive information on the currently existing methods and workflows used to characterize oil and water saturation in organic-rich unconventional reservoirs.


Publication:
Earth Science Reviews
Pub Date:
July 2019
DOI:
10.1016/j.earscirev.2019.05.012
Bibcode:
2019ESRv..194..327N
Keywords:
  • 2D;
  • Two-Dimensional;
  • AAPG;
  • American Association of Petroleum Geologists;
  • CBW;
  • Clay Bound Water;
  • CPMG;
  • Carr-Purcell-Meiboom-Gill pulse sequence (allows to measure transverse or spin-spin T<SUB>2</SUB> relaxation times of nuclei);
  • CRIM;
  • Complex Refractive Index Model;
  • CT;
  • Computed Tomography;
  • D-T<SUB>2</SUB>;
  • Diffusion Coefficient versus Transverse Relaxation Time;
  • EAGE;
  • European Association of Geoscientists &amp; Engineers;
  • EOR;
  • Enhanced Oil Recovery;
  • FID;
  • Free Induction Decay;
  • GC;
  • Gas Chromatography;
  • GR;
  • Gamma Ray logging;
  • GRI;
  • Gas Research Institute;
  • HC;
  • Hydrocarbons;
  • IFP;
  • French Institute of Petroleum;
  • IUPAC;
  • International Union of Pure and Applied Chemistry;
  • MICP;
  • Mercury Injection Capillary Pressure;
  • MMbpd;
  • Million Barrels of Oil Per Day;
  • MRI;
  • Magnetic Resonance Imaging;
  • MS;
  • Mass Spectrometry;
  • NMR;
  • Nuclear Magnetic Resonance;
  • OSI;
  • Oil Saturation Index (equals to S<SUB>1</SUB>·100%/TOC;
  • giving results in mg HC / g TOC);
  • PT;
  • thermobaric (pressure-temperature);
  • SEG;
  • Society of Exploration Geophysicists;
  • SEM;
  • Scanning Electron Microscopy;
  • SPE;
  • Society of Petroleum Engineers;
  • SPWLA;
  • Society of Petrophysicists and Well Log Analysts;
  • T<SUB>1</SUB>;
  • Longitudinal Relaxation Time (typically expressed in ms);
  • T<SUB>2</SUB>;
  • Transverse Relaxation Time (typically expressed in ms);
  • TE;
  • Time of Echo;
  • TGA;
  • Thermal Gravimetric Analysis;
  • TOC;
  • Total Organic Carbon;
  • ZTE;
  • Zero Time Echo
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