Helo Djudjuman,
In my opinion you should use HDSL. HDSL is cheap solution and does not need repeaters. Typical ranges (using two pairs) are like this:
wire 0,4 mm => range 4km
wire 0,6 mm => range 6km
wire 0,8 mm => range 8km
According to loop resistance, your wire is arround 0,6mm.
More important than loop resistance is attenuation measured at 150 KHz. Also cross-talk between pairs should be low.
Which type of HDSL you should choose?
1) Ask your vendor what type of modulation HDSL is using. If it is CAP (Carrierless Amplitude Phase), than it is OK. If modulation is 2B1Q, it is still OK, but it has approximatelly 10% shorter range.
2) Ask your vendor what is maximum attenuation in cable at 150 KHz. Choose HDSL with highest number, for example 35dB.
I would like to hear other opinions about HDSL....
Best regards
Radoje