Theoretically, in vitro fertilisation could be performed by collecting the contents from a woman's fallopian tubes or uterus after natural ovulation, mixing it with sperm, and reinserting the fertilised ova into the uterus.
Upstream operations deal primarily with the exploration stages of the oil and gas industry, with upstream firms taking the first steps to first locate, test and drill for oil and gas. Later, once reserves are proven, upstream firms will extract any oil and gas from the reserve.
The downstream sector commonly refers to the refining of petroleum crude oil and the processing and purifying of raw natural gas, as well as the marketing and distribution of products derived from crude oil and natural gas.he downstream sector commonly refers to the refining of petroleum crude oil and the processing and purifying of raw natural gas, as well as the marketing and distribution of products derived from crude oil and natural gas.