Oil rigs vs. gas rigs

The stored liquefied natural gas in the pillars would cause a significantly larger secondary blast compared to that of crude oil. If my understanding is correct, a secondary gas blast (given that the pillar storage areas are full or semi full) would more or less completely destroy the structure and is likely to sink it. The devastation would be total. However, costs related to rig accidents are also related to secondary effects such as spills/pollution. Liquified gas is easily dispersed in water and would cause minimal pollution effects compared to that of crude oil which coagulates and poses a significant environmental threat (and hence results in extremely expensive cleanup operations). It is uncertain which target would result in the highest economical losses. If you have enough explosives (3000-6000 kg) I would go for the oil rig. However, if availability of explosives is scarce (1000-3000 kg) I would go for the gas rig.

Oil refineries vs. gas terminals/refineries

Refineries and gas terminals (linking sea based pipelines to land based pipelines) are all land based and are therefore less vulnerable to single source explosions.

The principle of availability of explosives can be applied here as well. Certain parts of gas terminals and refineries are significantly more vulnerable to explosions as the liquified gas will serve as a secondary blast catalyzator and enhance the devastation. However, it is essential that the correct part of the refining/terminal structure is targeted. The whole point is to trigger a secondary reaction or even a chain reaction resulting in maximum devastation and thus maximum direct and indirect economical losses.

Crude oil or gasoline/benzene storage facilities

Storage facilities are often intentionally placed at remote locations far away from valuable and expensive infrastructure. As such, targeting storage facilities will result in limited direct and indirect losses.

Using LNG vessels (liquified natural gas tanker ships and tanker trucks) as weapons

LNG vessels are considered significantly more potent as weapons compared to benzene/gasoline vessels.

LNG has a significant blast effect while the effect of benzene/gasoline is usually limited to an incinerating effect.

The problems however is that the hijacking of LNG tankers (for the purpose of detonating them close to rigs or priority coastal structures will be difficult due to the maritime anti-terror forces who have trained specifically for such scenarios and usually is within a 20 minute radius.