Undeveloped oil reserve in Karamay Oilfield accounts for one-third of the proven oil reserve and is characterized by wide distribution

various reservoir types

complex in-situ condition and low produc-tion.The feasibility of developing this type of reserve is restricted by copious unfavourable factors

but it offers the advantage of economizing exploration cost and utilizing preexisting facilities in the deve-loped area.If a full use of it could be made

it will take an inestimable role in oilfield construction.In present paper

major geological and engineering factors that effect the reserve were analysed by application of development feasibility assessment technique.Based on the assessment of reserve reliabili-ty

water-injection method was selected

reasonable well spacing was determined

development index was predicted

and the economic assessment method of undeveloped oil reserve was proposed.The unde-veloped reserve was then classified as recoverable

hard to recover

unrecoverable and undetermined re-serves.In consideration of the economic effect of post-development

a set of indices(predominantly dy-namic)were optimized to economically classify the undeveloped reserve.The analysis examples have proved the realiability and coincidence of this economic classification and the criteria of the reserve assessment.