Measuring Conductivity of Proppants

API RECOMMENDED PRACTICE 19D SECOND EDITION, NOVEMBER 2021

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Foreword

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Contents

Page

1. Scope 1

2. Normative References 1

3. Terms, Definitions, Symbols, and Abbreviations 1

   1. Terms and Definitions 1

   2. Symbols 2

   3. Abbreviations 2

4. Procedure for Evaluating Proppant Pack Conductivity 2

   1. Objective 2

   2. Discussion 3

5. Reagents and Materials 3

   1. Test Fluid 3

   2. Platen Material 3

   3. Stainless Steel Shims (Backup Support) 4

6. Equipment 4

   1. Conductivity Test Cell 4

   2. Hydraulic Load Frame 5

   3. Pack Width Measurement Device(s) 5

   4. Test Fluid Drive System 5

   5. Differential Pressure Transducers 5

   6. Back-Pressure Regulator 5

   7. Balance 6

   8. Oxygen Removal 6

   9. Temperature Control 6

   10. Silica Saturation and Monitoring 6

7. Equipment Calibration 7

   1. General 7

   2. Pressure Indicators 7

   3. Flow Rate 7

   4. Zero-pack Width Measurement 7

   5. Hydraulic Load Frame 8

   6. Timers 8

   7. Balances 8

   8. Temperature Measuring Systems 8

   9. Data Acquisition System 8

8. Leak Tests 8

   1. Hydraulic Load Frame 8

   2. Fluid System Test 9

9. Procedure for Loading the Cell(s) 9

   1. Determination of Cell Width 9

   2. Gasketing Platens 9

   3. Cell Set-up 10

   4. Setting Bottom Platen and Bottom Piston 10

   5. Placement of Wire Cloth Filters 11

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      Contents

      Page

   6. Calculating the Quantity of Proppant 12

   7. Loading Dry Proppant into the Cell(s) 12

   8. Setting the Top Platen 13

   9. Stacking the Cell(s) 13

   10. Loading Cell(s) in the Load Frame 13

10. Acquiring Data 14

    1. Baseline Conditions 14

    2. Conductivity Measurements 14

    3. Single Stress Point Conductivity Measurement 15

11. Calculation of Conductivity and Permeability of Proppant Pack 15

    f

    1. Proppant Pack Conductivity (kW ) 15

    2. Proppant Pack Permeability (k) 16

    3. Simplified Equations for Proppant Testing Cell 17

12. Data Reporting 18

Annex A (informative) Conversion Factors and Test Fluid 20

Annex B (normative) Silica-saturation Vessel Setup 24

Annex C (informative) Conductivity Cell Figures 26

Bibliography 34

Figures

1. Location of Differential Pressure Ports: Proppant Pack Thicker than Pressure Ports 11

2. Location of Differential Pressure Ports: Proppant Pack Thinner than Pressure Ports 11

3. Platen Thickness and/or Levelness Measurement Points Schematic 11

C.1a Exploded View of the Conductivity Cell Stack (2 cells) 27

1. 1b Conductivity Cell Stack—Assembled Side View (2 cells) 28

   1. Upper and Lower Piston 29

   2. Cell Body 30

   3. Square Ring Gland Detail (see Figure C.2 and Figure C.6) 31

   4. Width Slat 31

   5. Central Piston 32

   6. Proppant Leveling Device 33

Tables

1 Representative Properties of Buena Vista Sandstone Platen Material 4

1. 2 % KCl (w/w) Solution: Viscosity (SI units) versus Temperature in Degrees Celsius 21

2. 2 % KCl (w/w) Solution Viscosity (USC units) versus Temperature in Degrees Fahrenheit 22

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Introduction

This document is largely based on API Recommended Practice 61, “Recommended Practices for Evaluating Short Term Proppant Pack Conductivity.” Informative references are also included in the bibliography.

The tests and test apparatus herein have been developed to establish standard procedures and conditions for use in evaluating the conductivity of various hydraulic fracture proppant materials under laboratory conditions. This procedure enables users to compare the conductivity characteristics under the specifically described test conditions. The test results can aid users in comparing proppant materials for use in hydraulic fracturing operations.

The procedures presented in this publication are not intended to inhibit the development of new technology, materials improvements, or improved operational procedures. Qualified engineering analysis and sound judgment is required for their application to fit a specific situation.

This document may be used by anyone desiring to do so. Every effort has been made to ensure the accuracy and reliability of the data contained in it. However, API makes no representation, warranty, or guarantee in connection with this document, and hereby expressly disclaim any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state, or municipal regulation with which this document may conflict.

This document uses a format for numbers which follows the examples given in API Document Format and Style Manual, First Edition, June 2007 (Editorial Revision, November 2017). This numbering format is different than that used in API 19D, First Edition. In this document the decimal mark is a period and separates the whole part from the fractional part of a number. No spaces are used in the numbering format. The thousands separator is a comma and is only used for numbers greater than 10,000, i.e. 5000 items, 12,500 bags.

In this document, where practical, U.S. customary (USC) units are included in parentheses for information. The units do not necessarily represent a direct conversion of metric units (SI) to US Customary units, or USC units to SI units. Consideration has been given to the precision of the instrument making the measurement. Consideration has also been given to the nature of the measurement, is it critical or simply informational.

In this document, calibrating an instrument refers to assuring the accuracy of the measurement. Accuracy is the degree of conformity of a measurement of a quantity to its actual or true value. Accuracy is related to precision, or reproducibility, of a measurement. Precision is the degree to which further measurements or calculations will show the same or similar results. Precision is characterized in terms of the standard deviation of the measurement. The results of calculations or a measurement can be accurate, but not precise, precise but not accurate, neither or both. A result is valid if it is both accurate and precise.

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Measuring Conductivity of Proppants

1. Scope

   
   

   This standard provides recommended testing procedures for evaluating proppants used in hydraulic fracturing and gravel-packing operations.

   
   

   NOTE The “proppants” mentioned henceforth in this document refer to natural sand, ceramic media, resin-coated proppants, gravel packing media, and other materials used for hydraulic fracturing and gravel-packing operations.

   
   

   The objective of the document is to provide consistent methodology for testing procedures used to measure performance of hydraulic-fracturing or gravel-packing proppants, or both. The testing procedures in this document are not designed to provide values of proppant conductivity under downhole reservoir conditions. Long-term test data have shown that time, elevated temperatures, fracturing fluid residues, cyclic stress loading, embedment, formation fines and other factors further reduce fracture proppant pack conductivity. Also, this reference test is designed to measure only the frictional energy losses corresponding to laminar flow within a pack. It is recognized that fluid velocity within an actual fracture can be significantly higher than in these laboratory tests and can be dominated by inertial effects.

   
   

2. Normative References

   
   

   The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced standard (including any amendments) applies.

   
   

   API Standard 19C, Measurement of and Specifications for Proppants used in Hydraulic Fracturing and Gravel- packing Operations

   
   

   ISO 1 3506-1, Mechanical properties of corrosion-resistant stainless-steel fasteners — Part 1: Bolts, screws, and

   studs

   
   

3. Terms, Definitions, Symbols, and Abbreviations

3.1 Terms and Definitions

For the purposes of this document, the following terms and definitions apply.

3.1.1

conductivity

Width of the fracture multiplied by the permeability of the proppant pack

3.1.2

laminar flow Darcy flow

Type of streamlined flow for single-phase fluids in which the fluid moves in parallel layers, or laminae, such that the layers flow smoothly over each other with instabilities being dampened by the viscosity.

3.1.3

permeability (k)

A measure of the ability of a porous medium to allow flow of fluid or gases.

1 International Organization for Standardization, 8 chemin de Blandonnet, CP401, 1214 Vernier, Switzerland; www.iso.org.

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