You might be interested in some previous threads on the reasoning and justification behind the Iraqi invasion of Kuwait:

• What were the causes behind the Iraqi decision to invade Kuwait? - 6 comments, over 2 months old.
• A commenter here gives a brief summary of the situation and the key facts that both pushed Saddam into action and made him think he would succeed.
• What was Saddam Hussein's game plan for holding and controlling Kuwait and what was his justification for invading in the first place? - 7 comments, over 5 months old.
• The commenters here talk in great depth about the political situation in the runup to the invasion as envisioned by Saddam Hussein and what he expected to happen in practical terms.
• Did Kuwait really cripple Iraq's economy before the Gulf War? If so, how? - 7 comments, over 4 months old.
• This gives a brief summary of the slant drilling issue and also discusses its direct relevance to the politics surrounding the invasion.
• Prior to Iraq's invasion and annexation of Kuwait, Iraq claimed that Kuwait was slant drilling, and essentially stealing, Iraq's oil. Were these claims ever substantiated or repudiated? - 48 comments, over 9 months old.
• This is the long story of the above, this time focusing on whether or not Kuwait was actually stealing Iraqi oil via slant drilling.