I working on a project for open loop well (drain and supply) with Wilo pump (the GSHP needs 3 m3/h flow rate)

(a) Does anyone have good information resource about the design of the borehole and type of filter to protect pump from dirts
(b) One concern is the hard water which will build up limescale, what the most cost effective way to minimise them.
(c) Is there guideline to calculate the depth of the open loop well. I;m aware it is complex issue (Hydrogeology), I'm looking for presentation or website that demostated job well done.
(d) I know the soils is not hard rock, mostly sands and it has underground river or lake.
(e) I'm thinking of 20 meter deep well with pump at 15m deep. Any comment?
(f) Any further information or link is welcome.

R.

I would contact a local water well driller in the area of your project. A submersible pump has a filter built in. I also install a spin down filter. Set up the heat pump for easy cleaning of the coil with ice maker flush.

What is your geographic location?

A water supply driller in your immediate area is the one to best address this.  I have a fairly comprehensive overview on my website.  Gennerally three gpm per ton of load is recomended, 2gpm if you have to scrimp.  The hard water is going to be an issue with build up in the exchange coil.  A periodic flushing of the coil with a scale remover may be able to keep you in business.

Riscy: 

Well design is not something you learn from reading a few websites or presentations or from asking questions on a forum like this. Groundwater flow is extremely complex.  

Groundwater does not flow like water in a lake or a river.  Groundwater is not in an undergound lake or river.  it is in an aquifer.  The characteristics of the aquifer are critical to the design.  Plus well diameter is a critical factor.

The previous posters gave good advice.  Contact a local water well driller.

Best of luck to you.

this info pertains to nyc there is some info here that might help good luck http://home2.nyc.gov/html/ddc/downloads/pdf/geotherm.pdf