Introducing New API/ISO Procedures for Proppant Testing

Abstract

In 2001, the International Organization for Standardization (ISO) and American Petroleum Institute (API) formed a new committee to write procedures for measuring the properties of proppants used in hydraulic fracturing. API Recommended Practices (RP) for testing of proppants are generally "reviewed and revised, reaffirmed, or withdrawn at least every five years?? in accordance to API instructions.  The last recommended practice was published in December 1995. The committee was charged with re-writing the API RP 56, 58, and 60 relating to sand as a proppant, gravel packing, and high strength proppants, respectively. This new document, ISO 13503-2 "Measurement of Properties of Proppants Used in Hydraulic Fracturing and Gravel-Packing Operations?? is considered a standard. Any company may follow these procedures and state on their published data that they followed ISO procedures to generate the specifications on their product. Several changes have been made to the recommended practices, and the goal of this paper will be to highlight these changes, and to discuss the potential impact on the proppant industry.

In 2003 a second committee was formed to write procedures on measuring long term conductivity of a proppant pack. The industry was using for years a procedure based on API RP 61 "Recommended Practices for Evaluating Short Term Proppant Pack Conductivity??, 1989, which is an obsolete document.  Roughly a dozen facilities worldwide are running long term conductivity tests, all slightly different.  Recent advances in technology have been incorporated in this standard to increase the accuracy of the results, and to standardize the equipment and testing procedures. The new standard is ISO 13503-5 "Procedures for Measuring the Long-term Conductivity of Proppants??.

These two new procedures will enable users to evaluate and to compare proppant characteristics under the specifically described test conditions for use in hydraulic fracturing operations. They are not designed to provide absolute values of proppant conductivity under downhole reservoir conditions.  Test data has shown that time, elevated temperatures, fracturing fluid residues, cyclic stress loading, embedment, formation fines, and other factors will further reduce proppant pack conductivity.

Introduction:

Over the past several years, the International Organization for Standardization (ISO) and the American Petroleum Institute (API) have been working to revise international standards. Two ISO committees drafting standards for the petroleum industry are Technical Committee 28- Petroleum Products and Lubricants and Technical Committee 67- Materials, Equipment, and Offshore Structures for the Petroleum and Natural Gas Industry.  Subcommittees are examining standards in drilling fluids, cementing, completion fluids and materials.

Three proppants sub-committees have been formed to work specifically on quality control testing procedures, long term conductivity, and specifications. In 2006 two standards were published ISO 13503-2¹ replacing American Petroleum Institute's Recommended Practices (API RP) 56², 58³ and 60⁴ for proppant quality control testing, and ISO 13505-5⁵ replacing API RP 61⁶ for long term conductivity testing.  The specifications standard is in the drafting stage.

These two new standards will enable users to evaluate and compare proppant characteristics under specifically described test conditions. The tests and test apparatus have been developed to establish standard procedures and conditions for use in evaluating proppant materials under laboratory conditions. The test results can aid users in comparing proppant materials for use in hydraulic fracturing operations.

The standards 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 will be required for their application to fit a specific situation.  This paper is not a comprehensive procedures document, but is intended to highlight the changes made from API Recommended Practices to the ISO Standard.