Problem encountered while drilling a borewell

Sir/ Madam

We were drilling a borewell for our new house construction. After drilling for 200 feet we got rock. Above the rock, water is present, but it is not sufficient. After drilling in the rock for 920 feet (total depth) a dry gap has come through which drilling is not possible. Neither air, water or mud is coming out. What may be the problem and kindly suggest a solution for this.

With regards

Shikeeb Ali Khan