Absolutely not... Unfortunately. It will get cooked and the parts of the GPU that doesn't have good thermal monitoring that triggers shutdown (VRMs come to mind) will get toasted.
By running the card fanlessly, you are literally playing with fire. You know how hot a 100W light bulb gets when you leave it on for while ? That's how hot your video card will be (internally) when you run it fanless, since everything these days are GPU accelerated even if you don't game (like the Aero desktop composition, all video streams including Flash and H.264, etc...).