Here is what works for me. I am using Wildfly 8.2.0, eclipselink 2.5.1.
Just add
<logger category="org.eclipse.persistence.sql">
<level name="DEBUG"/>
</logger>
<logger category="org.jboss.as.jpa">
<level name="DEBUG"/>
</logger>
for the registration subsystem in the standalone.xml file (in the configuration folder).
Only between
<subsystem xmlns="urn:jboss:domain:logging:2.0">
......
</subsystem>
The logging level for the console handler must be set to at least DEBUG, for example:
<console-handler name="CONSOLE">
<level name="DEBUG"/>
<formatter>
<named-formatter name="COLOR-PATTERN"/>
</formatter>
</console-handler>
.
.