Romans 8:27 (ESV) … “And he who searches hearts knows what is the mind of the Spirit, because the Spirit intercedes for the saints according to the will of God.”
Most of us feel particularly helpless in the matter of prayer. We stand appalled at times before the deep antipathy of our own hearts to prayer. Perfunctorily enough we say our prayers, but seldom do we ever really pray. There is not much merit in saying prayers; even an unsaved person can do that. Only a Spirit-taught believer can really pray. It is because the ministry of prayer is a purely spiritual ministry that we stand in such deep need of the Holy Spirit to help our infirmities in this matter.
The word for “helpes” in verse 26 occurs elsewhere in the New Testament only in Luke 10:40 where its use is most enlightening. It is found in the story of Martha and Mary when the Lord Jesus was the guest in their home. Mary was found at the Master’s feet. But Martha could be heard banging the pots and pans around in the kitchen. Evidently her irritation was growing. Why should she have to slave at the sink while Mary sat on the rug in the living room? Suddenly she burst out, “Lord, dost thou not care that my sister hath left me to serve alone? bid her therefore that she help me.” That is the very idea behind the use of the word in Romans 8. What we need in prayer is help—the practical, down-to-earth, everyday kind of help that Martha needed in the kitchen. The very name “Comforter,” used by the Lord Jesus when promising a new dispensation of the Holy Spirit, means literally, “one called alongside to help.” The kind of help He gives is the help a doctor gives when he is called alongside the sick bed; the kind of help a fireman gives when he is called alongside a burning building; the kind of help a lawyer gives when he is called alongside to undertake our case. What a Helper!
This help expresses itself in “groanings which cannot be uttered” or as J. B. Phillips translates it, “his Spirit within us is actually praying for us in those agonizing longings which never find words.”
The word for “groanings” here is stenagmos, found only here and in Acts 7:34 where Stephen used it in his defense before the Sanhedrin. Stephen had been describing the call of Moses and recalling the words God had used on that occasion: “I have seen, I have seen the affliction of my people which is in Egypt, and I have heard their groaning.…” How suggestive! The burden of the oppressed Israelites could only find expression in groans. The Holy Spirit, in expressing His burden for our spiritual state, groans with the same type of groans. Oh, the things in our lives which must grieve the Holy Spirit of God!
It cannot be doubted that the prayers of the Holy Spirit are effective. Paul states three very good reasons why they must be. 
God knows and searches our hearts as only He can.
He knows the Spirit’s mind: “knows what is the mind of the Spirit.”
He prays according to the will of God. One day this groaning will give place to glory as we, who have been adopted into the family, are finally fully adapted for that family and receive our glorified bodies and enter into God’s new creation.