Every time I try to generate a map I keep getting this error and I don't know how to fix it.

Error while running on_init: OmniSea/control.lua:13: attempt to index field 'omnitech-base-impure-extraction-1' (a nil value)

I've made sure I have all dependencies downloaded and nothing helped.
Hope someone knows what I did wrong.

Can you post your game version, and the version numbers of the mods you installed? Please note any mods you've installed that aren't in the mod list (so we can test with or without them)

version 0.16.51(build 36654, win64, steam)
a sea block config - 0.2.4
angels addons warehouse - 0.3.0
angels bioprocessing(alpha update) - 0.5.6
angels infinate ores - 0.7.3
angels petro chemical processing - 0.7.9
angels refining - 0.9.12
angels smelting - 0.4.4
base mod - 0.16.51
bobs adjustable inserters - 0.16.8
bobs assembling machines - 0.16.1
bobs electronics - 0.16.0
bobs enemies - 0.16.0
bobs functions library mod - 0.16.6
bobs logistics mod - 0.16.23
bobs metals and inermediates - 0.16.4
bobs mining - 0.16.0
bobs modules - 0.16.0
bobs ores - 0.16.2
bobs power - 0.16.5
bobs revamp mod - 0.16.2
bobs tech - 0.16.6
bobs warfare - 0.16.7
circuit processing - 0.1.2
explosie excavation - 1.1.4
fnei - 0.1.8
ks power - 0.2.4
landfill painting - 0.2.4
nuclear feul - 0.1.3
omnilibrary - 2.0.30
omnimatter - 2.0.16
ore eraser - 1.4.1
resource spawner overhaul - 3.7.7
science cost tweaker mod(mexmer) - 0.16.44
sea block - 0.2.12
sea block omnimatter compatibility - 1.3.0
sea block pack - 0.16.0
seablock tweaks - 0.2.1
space extension mod - 0.3.8

those are all the mods and they are all active

Well, okay. You've added a few extra mods, Which is always a tricky thing. And the one that's causing the error is the OmniSea mod (sea block omnimatter compatibility - 1.3.0)

The error is specific to that mod (Nil Value). You're going to have to contact that mod author. Here's a link to his profile. https://mods.factorio.com/user/Samuel2507

okay thanks