In fact, there is no real biblical support for this assumption, since prayer is always to God in the Bible and never to any creature, even an angel. (p. 349)*God is the only proper object of our prayers, Nowhere in Scripture is a prayer of anyone on earth actually addressed to anyone but God. (p. 350)
Genesis 19:15, 18-21 When morning dawned, the angels urged Lot, saying, “Arise, take your wife and your two daughters who are here, lest you be consumed in the punishment of the city.”. . . And Lot said to them, “Oh, no, my lords; behold, your servant has found favor in your sight, and you have shown me great kindness in saving my life; but I cannot flee to the hills, lest the disaster overtake me, and I die. Behold, yonder city is near enough to flee to, and it is a little one. Let me escape there — is it not a little one? — and my life will be saved!” He said to him, “Behold, I grant you this favor also, that I will not overthrow the city of which you have spoken.
Genesis 32:24-29 And Jacob was left alone; and a man wrestled with him until the breaking of the day. When the man saw that he did not prevail against Jacob, he touched the hollow of his thigh; and Jacob’s thigh was put out of joint as he wrestled with him. Then he said, “Let me go, for the day is breaking.” But Jacob said, “I will not let you go, unless you bless me.” And he said to him, “What is your name?” And he said, “Jacob.” Then he said, “Your name shall no more be called Jacob, but Israel, for you have striven with God and with men, and have prevailed.” Then Jacob asked him, “Tell me, I pray, your name.” But he said, “Why is it that you ask my name?” And there he blessed him.
[Someone might say about these two examples, “but the angels weren’t in heaven.” Location makes no difference: the angels still fulfilled intercessory requests made to them.]
Genesis 48:14-16 And Israel stretched out his right hand and laid it upon the head of E’phraim, who was the younger, and his left hand upon the head of Manas’seh, crossing his hands, for Manas’seh was the first-born. And he blessed Joseph, and said, “The God before whom my fathers Abraham and Isaac walked, the God who has led me all my life long to this day, the angel who has redeemed me from all evil, bless the lads; and in them let my name be perpetuated, and the name of my fathers Abraham and Isaac; and let them grow into a multitude in the midst of the earth.”
Revelation 5:8 And when he had taken the scroll, the four living creatures and the twenty-four elders fell down before the Lamb, each holding a harp, and with golden bowls full of incense, which are the prayers of the saints;
[These are dead human beings in heaven. Why would they have “the prayers of the saints, if those prayers could and should only be presented to God? They are obviously functioning as intercessory intermediators]
Revelation 8:3-4 And another angel came and stood at the altar with a golden censer; and he was given much incense to mingle with the prayers of all the saints upon the golden altar before the throne;  and the smoke of the incense rose with the prayers of the saints from the hand of the angel before God.
[Here angels are somehow associated with the prayers of the saints. It is plausible to conclude that they are interceding for human beings on earth, and that, therefore, they were asked to intercede by them.]