"When I worked on oil rigs Schlumberger, who is or was owned by Halliburton"
Martyn oh what blasphemy.........
Schlumberger (originally French) and Halliburton (US) are the two largest oilfield service companies on the planet..........and compete for everything......never the two have mixed...
We just about manage joint completions where we each install our bits and pieces...
The trucks in question are correctly logging trucks, used for monitoring a variety of oilfield processes.
They can be filled with electronic gear, beds, kitchenets, offices etc etc depending on the aplication.
Yes they are well tough...and normally overbuilt ...ie weigh huge ammounts....
when you charge $ 500,000 a day for a job...gas milage is un-important.