"may well affect" is a correct and usable phrase in written English.
It is used to express the possibility that something could have an impact or influence on a situation or outcome. It can be used in many contexts, such as describing potential consequences, speculating on future events, or discussing potential factors that could contribute to a result. Example: The ongoing trade war between the two countries may well affect the global economy in the coming months.
That perception, in turn, may well affect the types of decisions they actually make.
Turkish losses may well affect individual institutions in the Eurozone visibly.
This may well affect the application of nano-materials in concrete.
She added, however, that state laws vary widely and that the circumstances of a case may well affect whether a court would uphold a waiver.
The prosecutor's conclusions about Mr. Godineaux may well affect what he does with Mr. Taylor, even though retardation is not at issue with him.
A spokesman for the Justice Department referred to a 2009 letter that said "these studies may well affect the scope of the government's reopener claim".
Later, he had a long private exchange with the judge about his ailments, which may well affect the course of his trial.
This programme may well affect the way fictional courtroom dramas are presented in future, not because screenwriters will see it – they presumably go to court all the time – but because we have.
Some of those compounds in that sprig of thyme may well affect my digestion of the dish I add it to, helping to break down one compound or possibly stimulate production of an enzyme to detoxify another.
The escalation of the conflict in southern Lebanon may well affect -- some say jeopardize, others say kick-start -- the resumption of talks with Syria, which Israel holds responsible for the recent fighting in southern Lebanon.
But of course, this simple calculation is static: such a large increase in taxes may well affect the economic behaviour of the rich and the income they report pre-tax, the broader economy and, ultimately, the tax revenue generated.
