American Petroleum Institute

RECOMMENDED PRACTICES FOR LABORATORY EVALUATION OF SURFACE ACTIVE AGENTS FOR WELL STIMULATION - Second Edition
 N RP 42

Annotation

A. Surface active agents are frequently added to treating fluids for stimulation of oil, gas, and injection wells to perform one or more of the following functions:

1. prevent or minimize emulsification of treating fluid with formation fluid,

2. reduce water saturation,

3. alter wettability,

4. suspend fine particles dislodged by the treatment for removal or redistribution, and

5. stabilize foam or emulsion in the treating fluid.

B. This diversity of function has resulted in the availability of a large number of products for use in petroleum production operations. Testing of surface active agents as described herein is primarily for qualitative comparison of performance and for general screening related to preceding Paragraph A, items 1-4. Procedures are given for the following:

1. emulsion and sludge tests,

2. measurement of fluid flow through cores,

3. measurement of interfacial tension, and

4. measurement of wettability.

C. Since chemical activity of a surface active agent (surfactant) depends on its chemical environment, pressure, temperature, and time, the user is advised to test the surface active agent in the presence of all additives to be used in a field treatment at their appropriate concentration. Production batch and shelf life may effect variations in surface active agents' properties, so that in many cases even these items must be considered in evaluating a surface active agent.