ZAB Controller providing OJT described potential conflict event when developmental was not familiar with refueling operations and failed to note the developing conflict.

Narrative

I was providing OJT on the R-side to a D-side Developmental as directed. The Developmental has a couple hundred hours of training between two sectors but the training program at ZAB allows and encourages D-side Developmentals to work R-sides when the traffic is low. When the three aircraft were being handed off to us I questioned the Developmental on what they were doing and what clearances needed to be given. I gave the refueling clearances to the two refueling aircraft and turned the sector back to the Developmental. The Developmental got involved in a situation on the West portion of the sector and did not descend the third refueling aircraft. When conflict alert went off I took over again and climbed the third refueling aircraft and established that the other involved aircraft was still at FL230 as far as I know actual separation was never lost. I told my trainee that I did not feel the need to fill out a report since I was filling one out on the situation. Recommendation; the ratio of trainees to trainers is very high and there is not much time for trainers to work by themselves; a little time to work alone is needed. D-side trainees should have to have at least a couple of D positions before being allowed to train on R positions so that they have a little more base knowledge.