The most challenging aspect of reservoir management in a highly fractured carbonate reservoir is determining a completion that has the ability to control the production flux and prevent early unwanted fluid breakthrough while maintaining the production. Throughout the years, Saudi Aramco has made much advancement in the field of reservoir optimized completions, by continuously implementing new technology and techniques that enhance the design and deployment of these completions.When designing an ICD completion, it is critical to design a completion that is best able to provide production flux control while meeting production requirements, as well as considering key operational factors such as, safety, cost and the time required completing the design.
During the last decade, inflow control device (ICD) technology has rapidly developed and widely been used in horizontal wells due to its effectiveness in flux equalization and mitigation of unwanted fluid breakthrough. An ICD completion achieves flux equalization and manages water breakthrough by introducing an extra pressure drop in the ICD and redistributing the drawdown across the sandface between high and low permeable intervals of a horizontal well. This additional pressure loss in the ICD completion will cause reduction of effective productivity of the well, in other words it will require lower flowing bottom-hole pressure for a well with ICD completion to produce the same liquid rate compared to a well with a barefoot completion. The higher the pressure drop across the ICD completion, the better will be the equalization effect and water mitigation. Subsequently, the reservoir pressure has to be used wisely during field development as expensive pressure maintenance programs are utilized in many fields as part of the field development plans. This study tries to answer an important question: What should the optimum pressure regulation in an ICD completion be to realize the benefits of ICD without excessive reduction of well productivity? The effect of ICD regulation on flux equalization and well productivity reduction for various cases of well productivity index (PI) and permeability variation were studied through numerous static near wellbore simulation runs. Dynamic reservoir simulation was conducted to verify the results from the static simulation and dependence of the degree of flux equalization along the horizontal section on water breakthrough deferment and the oil recovery factor. An ICD design workflow is presented, which can be used to select an optimum ICD design, which maximizes the benefits of ICD with the least reduction in well productivity. A trade-off chart between well productivity and the degree of influx equalization has been built, which helps to determine the optimum pressure drop across an ICD completion in the presence of various levels of permeability variation along the wellbore. This approach can provide quick and simple calculation for the required ICD strength or number of ICD joints along the wellbore to maximize recovery of hydrocarbons. A real field case is used to illustrate the effectiveness of this workflow for optimum ICD design.
The industry has faced rapid advances in openhole completions in recent years, mainly in horizontal wells. Among these innovations, multistage fracturing and inflow control devices (ICDs) have gained notoriety as popular methods for field development, especially in unconventional reservoirs. Fracturing a horizontal well may be considered when formation permeability is low and laminated shales are present. Compartmentalization or anisotropies are also a reason for this type of completion. In the same manner, ICDs can be de-ployed in a heterogeneous reservoir to mitigate the potential for early water and/or gas breakthrough. To compare the features and benefits of both completion methods, the water breakthrough time was investigated in a full-field simulation model. Initially, a near-wellbore simulator was used to evaluate the applicability of the hydraulic multifrac and ICD completion. Then, a full-field simulation model was used to quantify the benefits of these completion techniques, where flow performance and completion optimization were accounted for. A degree of increase of recovery factor due to optimized completion was investigated. The multistage frac was modelled with explicit gridding techniques. These used local grid refinement and a single porosity approach around the well and induced fractures. ICDs were modelled with a multisegment well model, which analyzed the lateral well branches, fluid phase changes and pressure variations. This paper provides an example of the unconventional reservoir development for both a multistage frac option and an ICD completion. The optimization designs were aimed to achieve the optimum well completion strategy to fit specific reservoir conditions and an increasing recovery factor. The work was based on a real field case from Russia. The simulation runs were carried out using a commercial black oil simulator. Evaluation and selection criteria of these optimized completions are discussed in this paper.
Field development of a mature, highly fractured carbonate field presents several challenges. Most of the horizontal wells drilled in such fractured reservoirs suffer from early gas or water breakthrough because conductive fractures dominate the influx from the reservoir and cause an unbalanced flux profile along the wellbore. Premature gas or water breakthrough can result in poor sweep efficiency and reduced oil recovery for the well. To address the aformentioned challenges, passive inflow control devices (ICDs) can be used to equalize influx from the reservoir to the wellbore, thereby delaying gas or water breakthrough. However, during the life of the well, as water or gas breakthrough occurs, a passive ICD can be less effective in preventing water or gas production. This can effect well productivity and reduce the production life of the well, especially for a naturally flowing well. This paper describes how adjustable ICD technology with a sliding sleeve can be used as an effective reservoir management tool in mitigating challenges faced in a naturally fractured Middle Eastern carbonate field. Various examples from the subject field are presented to describe production challenges faced by barefoot and passive ICD-completed horizontal wells. The field cases suggest the need for adjustable ICD with sliding sleeve technology which provides a zonal shut-off option in case of water or gas breakthrough. A detailed workflow for usage of adjustable ICDs is described, and which includes well candidate selection, well monitoring and pre and post shifting well performance evaluation to determine which ICD unit must be shifted to a closed or open position. A dynamic simulation using a single-well model was also conducted to establish the benefits of a sliding sleeve on well production performance. An adjustable ICD with a sliding sleeve was chosen as the preferred completion technology over the passive ICD for horizontal wells for the subject field with a naturally fractured carbonate reservoir. A sliding sleeve integrated in an ICD is a simple and cost-effective tool for zonal water or gas shut off compared to conventional intervention technology available for horizontal wells. Sliding sleeves maximize the value of ICD technology by adding an adjustability feature to ICD to overcome the challenges faced by unexpected changes in well behavior and premature water or gas breakthrough. Dynamic simulation results also confirm the sliding sleeves can prolong the life of the well by reducing high water and free gas production, thereby increasing cumulative oil production.
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