CLOSED-LOOP EXTRACTION METHOD FOR THE RECOVERY OF HEAVY OILS AND BITUMENS UNDERLAIN BY AQUIFERS - THE VAPEX

In previous papers((1,2,3)) the authors described the results of injec ting saturated ethane or propane vapours into a scaled two-dimensional model to recover heavy oils and bitumen at or slightly above the rese rvoir temperature. The results were encouraging; Although the scaled o il production rates were lower than those obtained with SAGD((4)), the y showed that it may be possible to recover heavy oils and bitumens ec onomically using this method in conjunction with long horizontal wells . Apart from the low heat requirement inherent in the use of satu rate d propane, additional advantages derived from vapex are a partial in S itu deasphalting and a reduction in the content of heavy metals. The r esulting oil can be lighter, of a higher quality and better suited for a direct refining. In this paper these ideas are expanded further: a development of a closed-loop extraction is described and a technique f or spreading the hydrocarbon vapour underneath the oil bearing payzone is proposed to simulate the performance of a planar well Using this c oncept the vapour-oil contact is greatly increased and improved produc tion rates are obtained. The paper discusses scaled physical model res ults for Peace River bitumen and Lloydminster heavy oil. The mechanism involved is believed to be similar to that which was described earlie r on rising fingers of liquid solvent((5)). Experiments are presented that show that the rate of mobilization is a function of the areal dis tribution of the solvent vapour. The results demonstrate that oil prod uction rates exceed those of the SAGD in spite of the fact that no ext raneous heat is injected into the reservoir. This strategy may permit the economic production of marginal heavy oil and bitumen reservoirs.