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Unconventional Reservoir Services

GRI (Crushed Shale) Analysis

The exceedingly fine-grained and fracture-prone nature of shale/mudrock reservoir core challenges efficient provision of fundamental core data sets that include porosity, permeability, grain density, and core saturations. To do so typically requires special sampling, analytical, and measurement techniques. Core Laboratories worked with investigators representing the Gas Research Institute in development of the core analysis method referred to as "GRI" (GRI final report: GRI-95/0496). The method involves determination of intact-sample as-received bulk density. Then, by reducing the sample to a quantity of small particles, 0.5 to 0.85mm diameter, coring- and sampling-induced fractures are eliminated and pore pathways are greatly shortened so that efficient processing for pore liquid removal and quantification by distillation-extraction can be accomplished. Subsequent dry grain volume determinations conclude the sequence providing porosity, grain density, and core saturations.

GRI-method permeability is an unsteady state gas pressure-decay technique and may be determined using particles containing as-received pore liquids, yielding an effective kg or using clean-dry particles, yielding an absolute kg. In some cases, both permeabilities are determined. The effects of coring- or sampling-induced fractures and cracks are eliminated by use of small-particle samples and because of this the results are often referred to as matrix permeability or km.

GRI Core Analysis Particles

GRI "crushed" core analysis method provides:

  • Bulk density (as-received conditions)
  • Grain density (will include insoluble organic matter)
  • Total interconnected porosity
  • Gas-filled porosity
  • Core saturations; Sw, So, Sg
  • Matrix permeability to gas (at one or both as-received and clean-dry conditions)

Particles in the 20-35 US mesh size range (0.85 to 0.5mm), above, are used in the GRI core analysis method. In typical shale or mudrock, each particle will contain many thousands of individual grains and the associated pore bodies and pore throats.

GRI SMP-200 GRI SMP-200 Chart

Core Laboratories has developed the SMP-200, a new, built-for-purpose, particle permeameter. It incorporates a modified helium pycnometer and proprietary algorithms for derivation of km from sample parameters and test data.