The ever increasing need for hydrocarbons and their increasing rarity has led to the development of many new methods for recovering oil from previously worked formations. Many of these methods are very difficult to optimize in the field due to the great number of variables which can be encountered. Accordingly, it is desired to provide laboratory apparatus for modeling a real oil reservoir. More particularly, one method which appears promising is the use of steam flooding, in which steam is introduced at one point in a reservoir to encourage the movement of oil towards a well from which it can be recovered. However, there are numerous problems which are encountered in such operations and it is very difficult to determine what variable is causing a particular effect in the field. Accordingly, it is desirable to provide laboratory apparatus for modeling such situations. Such an apparatus would desirably allow variation of numerous process variables and physical models of the reservoir, and would furthermore allow testing of coinjectant materials mixed with the steam.