Sentry Drop to deny Mining like Oracle

This Sentry drop deny mining crossed my mind when I was going over the Oracle in HOTS again and read on Teamliquid somewhere about the 4 Sentry Warp Prism drop to Forcefield workers from escaping but I can't seem to find it. I hope some one can link the video and original post here.

You can basically disrupt all mining at a mineral line with 4 Force Fields. According to Liquidpedia here

-At 2 SCVs/mineral and 3 SCVs/gas, a base with 8 minerals and 2 gas will harvest ~672 minerals and ~215 gas per game minute.

-A fully saturated base with 8 minerals and 2 gas will harvest ~816 minerals and ~228 gas per game minute.

A force field lasts 15 seconds. If you can deny 2 workers mineral line, it will cost your opponent 168 minerals. If it is fully saturated it will cost them 204 minerals. This does not include any mining form Mules.

Let's take a look at a rough build.

-9 Pylon
-13 Gate>scout
-14 Gas
-16 Pylon
-18 Core
-Zealot>Staler>Sentry>Sentry
- 23 2nd Gas
-Robo after first Sentry

When your Warp Prism is done, Your Sentries will have slightly less than 4 Force Fields but by the time you reach your opponents base, you should have 4. Load your initial 4 units into Warp Prism and head to his mineral line and drop them. Cast 4 Force Fields to block off all mining. In addition your army will take down a couple of SCVs here.

For eg if you managed to kill 3 SCVs, you have just dealt 150+168=318 to 150+204= 354 minerals. That's a lot of damage at early phase of the game. You can also scout your opponent's army composition and tech path with this. This indirectly forces your opponent to be more careful like what the Oracle does by keeping some army at the mineral line.

Risk and Downside
-Is it justifiable to use your initial Force Fields to deal this damage? I don't know, just make sure your opponent isn't pushing across the map with your Probe at Watch tower.

-Your opponent will still get to mine the extra minerals if it goes to long macro mine out main base.

-I have not tried any other builds except, the Gate + Robo build. Probably something can be worked out with 1 Gate Double gas expand, into Robo 2 Gate. Fast expanding is getting very common

-Is the cost to get a Robo and Warp Prism justified for itself? You can get Obs too. Dealing ~340 damage early game is a lot. That is close to an expansion.

-The drop will most likely only work once.

You can also load some 4 Sentries and drop them at Zerg's main and natural to deal around 300+ damage and scouting too.

This is just an idea so feel free to comment.

Sometimes you may miss a mineral patch.

Edit: I feel this is a better way than boxing against Terran, as Terran can just lift the Command Centre.