I'm guessing each sample doesn't have the xy of the well, but probably (hopefully) does have which well it came from. All you would need is to add an x and y field/column to the csv and populate it with the xy coordinates of the corresponding well.
You could even just have the wells mapped, then join by attributes (e.g. matching well names) to append the values to the well feature.
It kind-of depends whether you would want a feature for every sample, or to append every new sample to a single well feature each time - resulting in multiple columns, or possible a single column populated with a delimited list of values e.g [ [Monday 1 Dec, 1.2 mmol/L U, 4 mmol/L Ra], [Friday 5 Dec, 9 mmol/L U, 8 mmol/L Ra] ]
Do you have any gis software or are you looking to use arcgis online?
