"Prayer is an open door which none can shut," wrote Charles Spurgeon in Morning and Evening. "Devils may surround you on all sides," he continued, "but the way upward is always open, and as long as that road is unobstructed, you will not fall into the enemy’s hand."
Is there anywhere we can go where God is not present? Not according to the Bible. Psalm 139:7 asks, "Where can I go from your Spirit? Where can I flee from your presence?" In Jeremiah 23:23-24 we read, "’Am I only a God nearby,’ declares the LORD, "and not a God far away? Can anyone hide in secret places so that I cannot see him?’ declares the LORD. ‘Do not I fill heaven and earth?’ declares the LORD (NIV)."
Prayer and God’s Omnipresence
The fact that God is everywhere is known as omnipresence, meaning that He is present everywhere throughout His creation. This does not mean that God is creation, a worldview known as pantheism, but that God is ever-present in His creation. C.S. Lewis likened this relationship between God and His creation to that of a painter to a painting: "A painter is not a picture, and he does not die if his picture is destroyed. You may say, ‘He’s put a lot of himself into it,’ but you only mean that all its beauty and interest has come out of his head. His skill is not in the picture in the same way that it is in his head, or even in his hands." 
As a result of the reality of God’s omnipresence, we are assured that no matter where we are, God will hear our prayers—even from the belly of a fish: "From inside the fish Jonah prayed to the LORD his God" (Jonah 2:1 NIV). While not the most comfortable place to pray, we know that God heard the prayers of the prophet, even while Jonah was in the ocean depths.
But do we really believe that prayer is always available? If so, we must act on this truth. Nothing, then, can keep a believer from coming before God in prayer, except our own choices: "For I am convinced that neither death nor life, neither angels nor demons, neither the present nor the future, nor any powers, neither height nor depth, nor anything else in all creation, will be able to separate us from the love of God that is in Christ Jesus our Lord" (Romans 8:38-39). Prayer will always connect us to God.
Prayer Has No Barriers
In short, prayer has no barriers. Governments cannot stop it, our location cannot stop it and enemies in the spiritual realm cannot stop it.
As noted earlier, "Prayer is an open door which none can shut." But there is one way to shut it and that is when we choose disbelief over belief. Our own anxieties can stop the power of prayer, if we allow them to stifle the truth that prayer is always available to us. God is always ready to listen, no matter what our circumstances, but we must speak to Him in prayer.
In reference to the power of evangelism, the Apostle Paul wrote, "’Everyone who calls on the name of the Lord will be saved.’ How, then, can they call on the one they have not believed in? And how can they believe in the one of whom they have not heard? And how can they hear without someone preaching to them? And how can they preach unless they are sent? As it is written, ‘How beautiful are the feet of those who bring good news!’" (Romans 10:13-15 NIV). Similarly, when we pray to God we will be heard. But how can God hear unless we pray? How can our prayers be received unless they are sent? How beautiful are the prayers of those who seek the Lord, despite their circumstances.
Prayer is always available to us, but far too often we turn to God in prayer as a last resort, not a first response.
God Wants to Hear Our Prayers
Is God too busy to hear our prayers? Is He occupied with weightier matters than our lives and troubles? Unlike the worldview of deism, which claims that God created and wound up the universe like a watchmaker winds a watch, leaving it to run on its own, God really cares not only about the larger scheme of the universe, but also for each person. He is not a deaf god like the god of deism, but a caring and active God. He transcends His creation, but is immanent—or active—in it. No prayer is too small for God to hear. Neither is any prayer too large for God to handle.
As Christ said, "Look at the birds of the air; they do not sow or reap or store away in barns, and yet your heavenly Father feeds them. Are you not much more valuable than they?" (Matthew 6:26 NIV) The answer to the question asked by Jesus is that we are indeed "more valuable than they," for we are created in God’s image (Genesis 1:26), "we are God’s workmanship" (Ephesians 2:10), and He loves us.
An important step in receiving the blessings of prayer is to humbly and sincerely offer our prayers to God. Fortunately, we can do this anywhere and anytime, because prayer is always available to us. But we must take the initiative. If we do so, God is eager to hear us, comfort us, strengthen us, help us, and uphold us with His "righteous right hand" (Isaiah 41:10).
 C.S. Lewis, Mere Christianity (New York: Macmillan, 1952), 44.