This is covered in the Marionette JS Docs here:
There may be some cases where you need to change the template that is used for a view, based on some simple logic such as the value of a specific attribute in the view's model. To do this, you can provide a getTemplate function on your views and use this to return the template that you need.
Reusing your code,
InfoWellsView = Backbone.Marionette.CompositeView.extend({
tagName : "div",
id : "info-well-list",
template : "#template-infowells",
itemView : InfoWellView,
getTemplate: function () {
if (this.model.get("infotype") === "blog") {
// use different template (#template-blogwell)
}
}
});