Optimization of the Development Layer Series Under Various Periods for High Dip Angle Reservoirs

The N Block in West Africa exhibits high dip angle characteristics and have multiple sets of oil-bearing layer series. Commingled water injection was initially employed, leading to uneven production between layers and poor overall development effects. Therefore, it is imperative to carry out optimization of layer series subdivision in order to improve the development of this oil reservoir. Currently, extensive research has been conducted to subdivide layer series of the reservoir, but the lack of consideration of reservoir dip angle has impeded the ability of existing research outcomes to guide efficient development of such reservoirs. Based on the evaluation of development effect for the N block, a set of charts guiding for subdividing the layer series at various periods of development are established. Considering the current development status, we propose adjustment strategies for subdivision. The results indicate that N block has undergone rapid depletion development as well as commingled water injection, leading to extremely uneven production of each layer. Moreover, there is also inclination in the reservoir, which further exacerbates the difference in development among layers. The main controlling factors of layer subdivision during depletion development are the pressure coefficient and thickness difference between layers, with the subdivision limits being 1 and 0.25, respectively. The permeability contrast must be taken into account when beginning the water injection stage, and the limit is 6. The influence degree of permeability and pressure coefficient are further enhanced during the water and gas injection periods, and their respective limitations are 4 and 1.5, respectively. In the future adjustment, it should be based on the overall two sets of development layers, supplemented by three sets locally, and track the dynamics in time to avoid water and gas channeling. This study clarifies the limit of layer subdivision in different development stages for high-dip reservoirs, and provides a significant theoretical guidance for efficient water and gas injection development of such reservoirs.