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In a standard SC2 league map, how long do the mineral patches and vespene geysers last? I know that you should start expanding before the resources start to dry up, and so I'm curious what the time frame is.

I'm curious how long they last at your starting base (assuming you continuously produce workers until you have 30 to saturate collection), and how long they last in an expansion site, where you start by sending about 10 workers there, and then build more until 30ish.

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This will be hard to answer, since there's many things influencing how many workers you will have and how rapidly you get that many, whether the opponent harasses you... I think it would be better to ask what the optimal amount of workers per resource is, with the goal to deplete the resource asap –  Ivo Flipse Sep 3 '10 at 14:44
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@Ivo I believe such a question already exists: gaming.stackexchange.com/questions/1338 –  tzenes Sep 3 '10 at 14:59
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I agree there may not be a perfect answer, and that answers won't take into account MULEs, building construction, supply block, etc. But it'd be nice to know the average baseline, for reference and build planning. –  Wikwocket Sep 3 '10 at 15:35
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I think the most important part of tzenes extensive answer is the point that you should expand anytime you can do so safely, not because you might be running out of minerals. At my level (silver) I still win games by simply expanding ASAP while my opponent stays on one base until they run out of minerals. Then they realize I have taken over the whole map and they starve to death. –  Peter Recore Sep 3 '10 at 16:42
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2 Answers

up vote 28 down vote accepted

Using the numbers tzenes gave:

  • Start out with 8 mineral patches, each with 1500 minerals
  • Start with 6 SCVs (right?)
  • An SCV takes 22 seconds to build
  • The first 2 SCVs on a mineral patch will gather 45 minerals a minute each, while the last one can be considered to gather about 12

In other words, there are 12,000 total minerals to gather; the first 16 SCVs will gather 45/min, the last 8 will gather 12/min. Using this knowledge (and not taking MULEs into consideration!), we can construct a table:

 Seconds  | Number   |  Resource gather rate  |   Total minerals
 elapsed  | of SCVS  |  (minerals / minute)   |  gathered (approx)
------------------------------------------------------------------
        0 |     6    |          270           |        0
       22 |     7    |          315           |       99
       44 |     8    |          360           |      214.5
       66 |     9    |          405           |      346.5
      ... |   ...    |          ...           |      ...
      198 |    15    |          675           |     1485
      220 |    16    |          720           |     1732.5
      242 |    17    |          732           |     1996.5
      ... |   ...    |          ...           |      ...
      374 |    23    |          804           |     3672.9
      396 |    24    |          816           |     3967.7

So at the time your 24th SCV is built and you become fully saturated, you could have mined about 3968 minerals. The remaining 8032 will then be mined in about 590 seconds, giving an overall time of 986 seconds, or about 16 and a half minutes.

Of course, this is a lower bound. In a real game, the actual time will be slightly longer because:

  • Some SCVs will be building/scouting
  • Some SCVs will be mining gas instead
  • Not all mineral patches will deplete at the same time, so your resource gather rate will actually go down near the end. Hopefully by this point, you have several other expansions :)
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+1, you guys made it hard to pick the correct answer! –  Wikwocket Sep 3 '10 at 17:02
    
@Wikwocket pick his, its a much better answer than mine. –  tzenes Sep 3 '10 at 17:10
    
@Wikwocket No pick his, I just did some simple math. The explanations come from tzenes –  BlueRaja - Danny Pflughoeft Sep 3 '10 at 17:15
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This brings us back to square one of "you guys make it hard to pick the correct answer" –  Grace Note Sep 3 '10 at 17:46
    
@Grace: Which is what the community voting system is for :) –  BlueRaja - Danny Pflughoeft Sep 3 '10 at 17:51
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So there are a number of variables involved here, but I'll try to help you out:

  • Standard base has 8 mineral patches
  • Each mineral patch has 1500 minerals
  • If you have 2 SCVs on a patch they harvest ~90 minerals per in game minute (depending on distance)
  • Standard base has 2 Vespene Geysers
  • Each Geyser has 2500 gas
  • 3 SCVs harvest at 101-114 gas per in game minute

Here is the problem: when you have more than 2 SCVs per patch they start to ping pong around between patches. At this time your SCVs harvesting rate starts to become indeterminate. However, we can calculate an upper bound on the time it takes if you have at least 16 SCVs mining minerals. 1500/90 = 16m 40s. We can further provide a better estimate based on the fact that, on average, 3 SCVs harvest at ~102, giving us 1500/102 = 14m 42s. Gas takes understandably longer to mine out because of its higher amount, on average: 2500 / 107.5 = 23m 15s.

Both of these numbers are further influenced by: Distance of minerals to based, number of workers transfered, distribution of workers transfered, build rate of new workers, use of chrono boost and infuse larva, number of worker producers, resource gain rates, and MULES.

Its also worth noting that the influence of workers beyond the 16th is significantly reduced according to this table:

  • One SCV on one mineral patch harvests 39-45 minerals per game minute, depending on distance.
  • Two SCVs on one mineral patch harvest 78-90 minerals per game minute, depending on distance.
  • Three SCVs on one mineral patch harvest ~102 minerals per game minute.

Gas is similarly influenced:

  • One SCV on gas harvests 33-42 gas per game minute, depending on distance.
  • Two SCVs on gas harvest 67-84 gas per game minute, depending on distance.
  • Three SCVs on gas harvest 101-114 gas per game minute, depending on distance. In the case of far-diagonal gas placement you will need 4 SCVs for full saturation

You'll notice that going from 1->2 per patch is a significant increase in gain, but 2->3 is less so.

A longer explanation of how to fully saturate can be found here: Whats the correct number of workers to put on gathering vespene and minerals in?

It is also worth noting that when you expand should not be determined by how long it takes a base to mine out, but rather when you are capable of doing so. This usually requires map control.

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Those are not really bounds, since you do not start out with enough SCVs to put three to a patch. How long does it take to build an SCV (and on a side-note, where do you get your statistics? :) –  BlueRaja - Danny Pflughoeft Sep 3 '10 at 15:20
    
@BlueRaja extensive testing both here and on teamliquid.net. SCV build time is standardized at 22 seconds (in game), but Probe and Drone build times very based on larval production and chrono boost. Additionally the production rate of SCVs is proportional to the number of command centers you control. Finally, those are upper bounds on the time once you have full saturation. –  tzenes Sep 3 '10 at 15:31
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So really, that 3-SCV case is your lower bound (since it assumes full saturation, but you don't start out with 24 SCVs, so the actual time is going to be longer than that - the two SCV case isn't really a bound since you don't start out with 16, but once you have 16 you could still increase your resource collection rate). I can give a much more accurate lower bound, then, using the numbers you give, but it doesn't fit into the comment box; I'll make it an answer. –  BlueRaja - Danny Pflughoeft Sep 3 '10 at 16:21
    
@BlueRaja well said +1 to you –  tzenes Sep 3 '10 at 16:56
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