Field Application of Evaluation Model for Development Effect on Horizontal Waterflooding in Thin Low-permeability Carbonate Reservoirs

Abstract

Low-permeability carbonate reservoirs with layered characteristics generally exist in Middle East district. The reservoirs achieved low recovery efficiency using vertical well by depletion mode in the early stage, and low horizontal and vertical sweep efficiency by vertical waterflooding due to high permeability streak and interlayer. Some oilfields in the district has successively implemented horizontal waterflooding technology and achieved good development results. Feasible and effective report has not been provided yet on the problem that the range of recoverable reserves and recovery efficiency can be increased by horizontal waterflooding. Considering some oilfields accomplished horizontal waterflooding in quick succession and some oilfields were just developed by horizontal waterflooding, practical resolution should be recommended such as the corresponding evaluation model for enhancing recovery efficiency range of the technology. The paper put forward an evaluation model for enhancing recovery reserves and recovery efficiency of horizontal waterflooding based on production decline model and waterflooding curve model. The resolution can also provide an evaluation basis of enhancing recovery efficiency for optimization and adjustment of horizontal water flooding. Applications of these concepts are illustrated with D oilfield in Oman. Results indicated that recovery efficiency by horizontal waterflooding after natural depletion development may be increased around 25% and about 4% by the optimization and adjustment process. The evaluation model will be used effectively to predict IOR effect of the similar reservoirs in Middle East oilfields.