Several things to consider:
Tax: You will be liable to pay US taxes on anything above 82.5k (so 38.5k is subject to US federal taxes at the 82.5k rate) and also on the entire 120k in Singapore. Singapore's tax rate for that income bracket level is 17% this year assuming you cannot get any deductions that take yr income to below S$160k (~US107k). The next rate is 14%. So make sure your company covers for one of the two taxes for which you are liable for.
Accommodation: If you get an allowance of around US$2.5-3k a month, you should be able to find something very, very decent though not in the heart of town. Those nice 2 bedrooms in town are going for about US$4-5k.
Transportation: Well, Singapore's public transport system is very convenient and arguably one of the best in the world. But if the company provides any sort of allowance, that's really a plus point.
Schooling: This I can't really comment because I've none of my own. Post something in the other areas of the forums or search around. Plenty of that around.
Apart from that, you should receive a home leave allowance or allocation and the standard stuff like "hardship" allowance (which is a joke cos it's SG), Movers
, apartment search allowances/assistance, temporary housing etc...
Coming from the O&G industry, your relo/expat packages shd be definitely above and beyond most other industries....