In Divi, the feature image is displayed at the top of the blog post as standard.
If you have created a project for your portfolio, the feature image is also displayed at the top of the project (projects and blog posts are treated the same way).
You may not want your feature image being displayed on your blog post or project.
You may just want to have complete freedom over what image you display.
If this is the case for you then you want to turn of the setting that controls this.
From the WordPress dashboard go to Divi -> Divi Theme Options -> Single Post Layout
Find the setting ‘Place thumbs on post’ and set this to ‘disabled’.
Now, there will be no featured image in your post of project.
The other way to stop the feature image being added is to write your blog post or project using the Divi editor.
Once you click that purple Divi button and create your content in the editor, the feature image settings are over ridden.