Inflow Control Devices (ICDs) are typically deployed as parts of the lower well completion in horizontal wells to equalize the pressure drop along the drain length and to achieve a uniform flow through the formation. Therefore, ICDs can delay undesired water or gas breakthroughs and maximize the reservoir recovery, particularly when producing from heterogeneous reservoirs. However, by imposing additional pressure drops across segments, ICDs can reduce the production potential in the early stages of well life. This paper presents a novel design methodology, using dynamic reservoir modeling, to make ICDs responsive to the well flowing conditions and to eliminate the pressure drops across segments in early well life by using the shifting technique.
The reservoir contains several sublayers and exhibits significant contrast in rock and fluid properties. The horizontal oil producer targets all sublayers simultaneously. A five-spot water injection pattern is planned to maintain the reservoir pressure. Usually, ICDs are designed based on well models that do not cover the entire expected well life. In our methodology, we rely on the dynamic reservoir model to predict changes of pressure and fluids along the drain and to find the optimal ICDs design that can respond to these changes. Sliding sleeves are combined with ICDs to allow choking back unwanted water production over time. Moreover, the design is tested with a systematic sensitivities approach for different well and reservoir conditions to ensure a robust design against reservoir uncertainties. The proposed completion design methodology was successfully implemented in a horizontal well crossing a layer-cake heterogeneous carbonates reservoir in offshore Abu Dhabi.
The well deliverability analysis suggests that the well cannot produce more than 25% water cut without artificial lift. Sensitivities were conducted at varying water cuts for each ICD compartment in addition to specific sensitivities for the high permeability compartments. To reach the optimal completion design, reservoir simulations were used to evaluate the benefits of various combinations of ICDs and nozzles sizes and their overall impact on well performance. The optimal design consisted of five compartments in the horizontal section with 14 ICDs and proved to be more effective in delaying water breakthrough into the compartments with high permeability without affecting the initial production rates.
The benefits of ICDs are well known in the industry to equalize the well flux based on permeability contrast by choking production selectively. The novel technique presented in this paper eliminates the choking effect on proction during the early well life while retaining the full benefits of ICDs for later stages; using the shifting technique, the offending layers can be choked back or closed completely to maximize oil production rates and reserves.