Not exactly. I believe the 144,000 mentioned in chapter 14 are the same ones mentioned in chapter 7. These 144,000 are the sons and daughters prophesied in Joel 2:28-29 of which the day of Pentecost (Acts 2) was a type before this great tribulation that is to come. These servants of God are not sons and daughters of the gentile tribes or nations, but from the tribes of Israel, with the tribe of Dan (Genesis 49:16-17) being replaced by one of the two tribes from Joseph, Ephraim and Manasseh, who Jacob (Israel) gave a special blessing (Genesis 48).
The 144,000 from the tribes of Israel are sealed before the calamities of last times occur. The reason for their preservation is the sealing of God.
This is not the case with the 144,000 in chapter 14. They are not on the earth at all. They have been raptured out of the earth altogether. Two things are important.
1.) The fact that they are seen not on earth but in heaven signifying rapture.
2.) The timing of their having been taken to heaven.
First how do I know that they are in heaven and not on the earth ?
"And I heard a voice OUT OF HEAVEN like the sound of many waters ... etc." (14:2)
The sound of their singing is heard
"out of heaven" (14:2) . They have also been
"purchased FROM THE EARTH" (14:4) . They were not only purchased from among men. They are purchased
"from the earth".
I say they have been raptured to stand before the Lamb and the four living creatures which John saw in heaven (chapter 4 and 5).
However this alone does not call for them being a different group from the 144,000 in chapter 7 unless the timing of the vision is different. So #2.
2.) The 144,000 in chapter 7 are apparently sealed in order to be preserved THROUGH the damage of the winds (calamities of the last times and great tribulation).
" ... Do not HARM THE EARTH or the sea or the trees UNTIL we seal the slavs of our God upon their foreheads." (7:3)
They should be sealed so that the HARM does not HARM them apparently.
With the 144,000 Firstfruits of chapter 14 they are off the earth before the events of the great tribulation according to the layout of events of the chapter.
Here is how chapter 14 is laid out:
Verses 1- 5 The vision of the 144,000 Firstfruits in Heaven with the Lamb on some heavenly Mount Zion.
Verses 6-7 The proclamation of the eternal gospel to fear God the Creator.
Verse 8 The announcement of the judgment of Religious Babylon
Verse 9 - 12 The warning of earth dwellers not to worship Antichrist or his image.
Verse 13 The promise of blessing to the martyrs during the great tribulation.
Verses 14 -16 The Harvest of "ripe" believers at the end of the great tribulation.
Verses 17 - 20 The gathering of the grapes of wrath for the battle of Amegeddon at the end of the great tribulation.
It should be seen that the specific details which reveal the contents of the great triblation all follow the scene of the 144,000 Firstfruits already raptured into Heaven.
For these reasons the 144,000 preserved THROUGH the great tribulation (ch. 7) is probably a different group than the 144,000 purchased off the earth before the great tribulation (ch.14).
The Joel reference I may comment on latter.