Production logging, openhole-log interpretation help discover new oil reserves

In this paper, the authors examine the evaluation of a low-resistivitypay siliciclastic reservoir in Bohai Bay, China. A significant amount of irreducible water is bound to the rock surface, dramatically lowering the resistivity of the pay zone. The authors explore a theory that the low resistivity is caused by bound water trapped in clay minerals, using production logging to provide the ground truth of reservoir fluids in the low-resistivity pay and improve the petrophysics model. With the improved model, production predictions were made for offset wells based on their openhole logs. The production histories of these wells are highly consistent with the authors' predictions. © 2021 Society of Petroleum Engineers. All rights reserved.