Sensitivity of Crossflow to Parametric Study of Complete Pressure Distribution Model for Horizontal Well in a Two-Layered Bounded Extended Reservoir

Abstract

A crossflow interface acts as a constant pressure external boundary. It provides recharge of energy within a layer by fluid influx from another layer. The extent of recharge is determined by the degree of crossflow. Since there is no direct way to determine the degree of crossflow at the scale of a reservoir, parameters that control the behavior of crossflow were used to study its effect on pressure responses. This article is aimed at determining the sensitivity of crossflow to changes in the values of the parameters that control its performance in a two-layered bounded reservoir. Conceptual, physical, and mathematical models were sequentially developed for a horizontal well in a two-layered bounded reservoir with a crossflow interface. A mathematical model for the crossflow interface was derived as a function of fluid properties, reservoir properties, and real time. Quantifying parameters were defined as degree of crossflow, D, and ease of crossflow, E. Various configurations of the two-layered reservoir, resulting in eighteen sets of data, were used to study behaviour of Crossflow. From the results obtained, the degree of crossflow increases as the dimensionless pressure reduces. As ease of crossflow increases, so also does the rate of decline in pressure derivative. Degree of crossflow varies directly as dimensionless well standoff, dimensionless well radius, and dimensionless well length. The degree of crossflow varies inversely as the time normalization factor, dimensionless reservoir width, and dimensionless reservoir length. However, the degree of crossflow is not affected by reservoir thickness and interlayer mobility ratio. Ease of crossflow varies directly as interlayer mobility ratio, dimensionless well length, and dimensionless well radius but inversely as dimensionless well standoff, dimensionless reservoir length, and dimensionless reservoir width. But ease of crossflow is not affected by reservoir thickness. It was observed that optimum oil production and effective reservoir management can be achieved if both layers are produced from the layer with higher mobility. It is therefore recommendable as the best completion strategy for a layered reservoir with a crossflow interface to produce both layers from the layer with higher mobility.