David Geffen may be in for a battle, because his estranged husband has just filed legal docs strongly suggesting his estranged hubby wants a chunk of David’s fortune.

David Andrew Armstrong (aka Donovan Michaels) filed a response to Geffen’s divorce petition. In the docs, obtained by TMZ, Armstrong’s lawyer, Samantha Spector, checked a box that asks the judge to “Determine rights to community and quasi-community assets and debts.”

That’s significant, because TMZ has previously reported, Geffen, an 82-year-old whose wealth is estimated at $8.7 BILLION, has been retired for 15 years. Our understanding is he has no income other than investments, including property sales and dividends from stocks and equities. Those assets are all separate property.

Apparently, 32-year-old Armstrong is not convinced. He is also asking for spousal support, which Geffen agreed to pay when his lawyer, disso queen Laura Wasser, filed divorce docs.

The 2 have been married for just under 2 years, and under Cali law, Armstrong would only be entitled to 1 year of spousal support.