頚城油田における水攻法評価 炭酸ガス攻法パイロットテストに向けて

Abstract

A part of the reservoir in the Kubiki Oil Field has been waterflooded since 1980. Several producers already experienced water breakthrough to this date. In this situation, the project of CO2 flood pilot to this reservoir has been initiated and is in its third year at present.Three investigation wells have been drilled during the last two years in the pilot test area, and the information, such as full series of the state-of-the-art logging data, has been obtained to improve the geological and petrophysical description and to modify our understandings of the reservoir conditions after waterflood.Some conclusions of waterflood evaluation in the pilot area derived from the above mentioned investigations are as follows.• Good vertical sweep efficiency has been achieved.• Irreducible water has been displaced by injection water.• Oil saturation is reaching to residual oil saturation (20-30%) around the target area.• Secondary recovery is about 5% of OOIP while primary recovery was 15%.• Steep pressure gradient exists locally.• Rock facies varies vertically and/or horizontally in relatively small region.The whole above informations will be examined more minutely and merged for the better understanding of the reservoir conditions, which will contribute to design, performance prediction and evaluation of CO2 flood pilot.