Lifting of water from borewell

I have a borewell of about 800 ft and am using a submersible pump ( at 670 ft) for lifting water. But the pump is giving frequent problems because of sand cut and has to be pulled for servicing frequently. In addition to the fact that this is expencive, there is considerable delay also due to non availability of experienced persons for the persons for the process.

I am aware that using compressed air to lift water is innefficient. Still I am seriously considering to switch over to use of compressed air in view of the problems mentioned above.I would be thankful, if any one can advice me whether using compressed air to lift water from 800 ft. is advisable.

I would like to know:

(1) Up to what depth air lifting method can be used to lift water from a borewell without problems?

(2) Whether use of present delevery pipe (1 1/2 " ) is advisable for this purpose.