How to do a sexual energy exchange?

[Infinite]

So is it Tantra to move the orgasm point from lower up to the heart through releasing blockages?

Something like that. The goal of Tantra is to transmutate the sexual energy into a higher energy. Mantras and other techniques are used in the sexual intercourse and real love is necessary. The alchemic myth of philospher's stone is about that process. Quote of Ra:

Contrary-wise, the positively oriented entity will be transmuting strong red-ray sexual energy into green-ray energy transfers and radiation in blue and indigo and will be similarly transmuting selfhood and place in society into energy transfer situations in which the entity may merge with and serve others and then, finally, radiate unto others without expecting any transfer in return.

(54.25)