Maybe this will help from New Advent
Immensity and ubiquity, or omnipresence
Space, like time, is one of the measures of the finite, and as by the attribute of eternity, we describe God’s transcendence of all temporal limitations, so by the attribute of immensity we express His transcendent relation to space. There is this difference, however, to be noted between eternity and immensity, that the positive aspect of the latter is more easily realized by us, and is sometimes spoken of, under the name of omnipresence, or ubiquity, as if it were a distinct attribute. Divine immensity means on the one hand that God is necessarily present everywhere in space as the immanent cause and sustainer of creatures, and on the other hand that He transcends the limitations of actual and possible space, and cannot be circumscribed or measured or divided by any spatial relations. To say that God is immense is only another way of saying that He is both immanent and transcendent in the sense already explained. As some one has metaphorically and paradoxically expressed it, “God’s centre is everywhere, His circumference nowhere.”
That God is not subject to spatial limitations follows from His infinite simplicity; and that He is truly present in every place or thing — that He is omnipresent or ubiquitous — follows from the fact that He is the cause and ground of all reality. According to our finite manner of thinking we conceive this presence of God in things spatial as being primarily a presence of power and operation — immediate Divine efficiency being required to sustain created beings in existence and to enable them to act; but, as every kind of Divine action ad extra is really identical with the Divine nature or essence, it follows that God is really present everywhere in creation not merely per virtuten et operationem, but per essentiam. In other words God Himself, or the Divine nature, is in immediate contact with, or immanent in, every creature — conserving it in being and enabling it to act. But while insisting on this truth we must, if we would avoid contradiction, reject every form of the pantheistic hypothesis. While emphasizing Divine immanence we must not overlook Divine transcendence.
http://www.newadvent.org/cathen/06612a.htm#IIB