Hi, JH, I'm sorry but I must admit that I simply don't know the answer to your question.
All I can say is that a Christian believes prayer to be a gift from God. And since Christianity is a communal fellowship of the many, as opposed to a restricted, even exclusive membership, it is as much a communal activity as it is a deeply private affair.
The Pauline epistles were written by a man who was deeply committed to prayer. He is constantly breaking out into thanksgiving, adoration, petition, and doxology, A good summary of Paul's teaching on prayer is found at 1Tim 2:1-8.
Christianity has often been described not, as a religion, but a relationship. Not just a relationship of the individual, but the wider community of believers at large to God. As Paul shows at vs 8 of the above mentioned text, the prayers of the many evidently are as effective, if not more so, than that of an individual. Why? Dunno. Paul did'nt elaborate. He merely recommended.
Cheers