One of the simplest op-amps looks like this:

^{simulate this circuit – Schematic created using CircuitLab}

And you can build it using NAND gates:

^{simulate this circuit}

One of the simplest op-amps looks like this:

^{simulate this circuit – Schematic created using CircuitLab}

And you can build it using NAND gates:

^{simulate this circuit}

^{simulate this circuit}

So the answer is YES.

Keep in mind that this will be crap, and will operate only over avery narrow range. The primary tool for operation that we have in the design of op-amps from transistors is playing with the widths and length of the transistors. We could do this here a little bit, especially in the diff pair as I could parallel several NAND gates.

Of course I haven't given you the necessary background to understand how this works, but the circuits (topology) are identical. To clarify things, if something is not hooked up, then ignore it and if you trace the connections you can see that I have duplicated the op-amp using 5 NANDs.