Step 1: Identify the nature of the deal.
An Indian company signed a 10 year LNG supply agreement worth up to 3 billion dollars with ADNOC Gas in 2026.
Step 2: Eliminate the other oil companies.
Bharat Petroleum, Indian Oil and Reliance Industries all deal in energy but were not named as the signatory in this particular ADNOC agreement.
Step 3: Recall the actual company.
Hindustan Petroleum Corporation Limited signed this long term LNG supply deal with ADNOC Gas to secure its future energy needs.
\[ \boxed{\text{Hindustan Petroleum Corporation Limited}} \]