TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractIn long horizontal wells, production rate is typically higher at the heel than at the toe. The resulting imbalanced production profile may cause early water or gas breakthrough into the wellbore. Once coning occurs, well production may be severely decreased due to limited flow contribution from the toe. To eliminate this imbalance, inflow control devices (ICDs) are placed in each screen joint to balance the production influx profile across the entire lateral length and compensate for permeability variation. Passive ICDs should be designed to control the influx without the need for intervention.There are two basic pressure drop mechanisms used currently in ICDs, restriction or friction. Restriction mechanisms rely on a contraction of the fluid flow path to generate an instantaneous pressure drop across the device. A frictional device creates a pressure drop due to fluid flow along the length of a channel or tube.There is an industry misconception that all ICDs will create a uniform influx. The reality is that none of these mechanisms alone meets the ideal requirements of an ICD designed for the life of the well: high resistance to plugging, mud flowback assurance, high resistance to erosion and high viscosity insensitivity. This paper will detail the development of a new hybrid design that incorporates all the positive features necessary to effectively produce a well from startup, peak production, through eventual water onset and beyond. Available in standard or field-adjustable versions, this unique design maximizes flow areas to reduce velocities and increase erosion resistance. Fullscale performance testing validates that the hybrid design offers the highest level of viscosity insensitivity available. Because ICDs are permanent downhole components, their long-term reliability is imperative, and these new developments will improve their performance and ability to effectively balance inflow for the life of the well.

In long horizontal wells, production rate is typically higher at the heel of the well than at the toe. The resulting imbalanced production profile may cause early water or gas breakthrough into the wellbore. Once coning occurs, well production may be severely decreased due to limited flow contribution from the toe. To eliminate this imbalance, inflow control devices (ICDs) are placed in each screen joint to balance the production influx profile across the entire lateral length and to compensate for permeability variation. Pressure drop in an ICD is created through either restriction or friction mechanisms. Restriction mechanisms rely on a contraction of the fluid flow path to generate an instantaneous pressure drop, resulting in higher velocities, and are thus more prone to long-term erosion damage as well as plugging during mud flowback. A restriction device, however, is less sensitive to viscosity properties of the fluid. A frictional device, which creates a pressure drop over a distributed length, is less likely to erode due to lower fluid velocities, but is more sensitive to viscosity changes. Viscosity insensitivity is desired to minimize preferential water flow whenever water breaks through into the well. This paper will detail the development of a new hybrid design concept that uses the best features of the restricting and friction designs, while minimizing the less desirable characteristics. Because these ICDs are permanent downhole components, their long-term reliability is imperative, and these new developments will improve their resistance to erosion and their ability to effectively balance inflow. Conceptual fluid dynamics analysis was used extensively to characterize the new design, along with actual full-scale flow testing. Introduction The purpose of inflow control devices (ICDs) is to effectively balance well production throughout the entire operational life of the completion to optimize hydrocarbon recovery. Since a typical well with ICDs can be in production from 5 to >20 years, the long-term reliability of such a device is crucial to the well's overall success. The significant factor in the reliability of an ICD is its ability to maintain a uniform influx over the well life. If an ICD is not able to maintain a uniform flux rate, increased localized production rates will occur and the well will become unbalanced. This will render the ICD ineffective, leading to premature water and/or gas breakthrough and possible loss of sand control. At some stage in a well's life, water may break through into the wellbore in certain sections due to heterogeneity of the formation and/or vertical fractures. Ideally, once this occurs, flow contribution from these water-producing zones should not be greater than the oil-producing sections. In production wells with higher-viscosity oil (>10 cp.), ICD type selection becomes a more critical factor due to the larger difference in viscosity between the oil and produced water. The pressure reduction mechanism in an ICD in this situation must have the lowest sensitivity to viscosity to maintain an even flow profile across the entire lateral wellbore. A restrictive-type ICD thus will provide best results in this regard due to its lower sensitivity to viscosity. This type of ICD however, has a greater potential for long-term erosion and lower plugging resistance. The ideal solution is to provide the lower viscosity sensitivity of the restrictive device with the lower erosion and higher plugging resistance of the frictional design. This means using the restrictive pressure loss mechanism while limiting the fluid velocity through the device below the critical level which will cause erosion. Limiting the fluid velocity also can result in increased minimum flow area if configured efficiently.

No abstract

Calculation of a representative particle impacting velocity is an important component in calculating solid particle erosion inside a pipe geometry. Experiences in calculating erosion for solid-gas systems indicate that gases normally do not affect particle motion near a solid wall. However, solid particles that are entrained in a liquid system tend to undergo a considerable momentum exchange before impacting the solid wall. Currently, most commercial CFD codes allow the user to calculate particle trajectories using a Lagrangian approach. Additionally, the CFD codes calculate particle impact velocities with the pipe walls. However, these commercial CFD codes normally use a wall function to simulate the turbulent velocity field in the near wall region. This wall-function velocity field near the wall can affect the small particle motion in the near wall region. Furthermore, the CFD codes assume particles have zero volume when particle impact information is being calculated. In this investigation, particle motions that are simulated using a commercially available CFD code are examined in the near wall region. Calculated solid particle erosion patterns are compared with experimental data to investigate the accuracy of the models that are being used to calculate particle impacting velocities. While not considered in particle tracking routines in most CFD codes, the turbulent velocity profile in the near-wall region is taken into account in this investigation and the effect on particle impact velocity is investigated. The simulation results show that the particle impact velocity is affected significantly when near wall velocity profile is implemented. In addition, effects of particle size are investigated in the near wall region of a turbulent flow in a 90 degree sharp bend. A CFD code is modified to account for particle size effects in the near wall region before and after the particle impact. It is found from the simulations that accounting for the rebound at the particle radius helps avoid non-physical impacts and reduces the number of impacts by more than one order-of-magnitude for small particles (25 μm) due to turbulent velocity fluctuations. For large particles (256 μm), however, non-physical impacts were not observed in the simulations. Solid particle erosion is predicted before and after introducing these modifications and the results are compared with experimental data. It is shown that the near wall modification and turbulent particle interactions significantly affect the simulation results. Modifications can significantly improve the current CFD-based solid particle erosion modeling.

In recent years, the study of flow-induced erosion phenomena has gained interest as erosion has a direct influence on the life, reliability and safety of equipment. Particularly significant erosion can occur inside the drilling tool components caused by the low particle loading (<10%) in the drilling fluid. Due to the difficulty and cost of conducting experiments, significant efforts have been invested in numerical predictive tools to understand and mitigate erosion within drilling tools. Computational fluid dynamics (CFD) is becoming a powerful tool to predict complex flow-erosion and a cost-effective method to re-design drilling equipment for mitigating erosion. Existing CFD-based erosion models predict erosion regions fairly accurately, but these models have poor reliability when it comes to quantitative predictions. In many cases, the error can be greater than an order of magnitude. The present study focuses on development of an improved CFD-erosion model for predicting the qualitative as well as the quantitative aspects of erosion. A finite-volume based CFD-erosion model was developed using a commercially available CFD code. The CFD model involves fluid flow and turbulence modeling, particle tracking, and application of existing empirical erosion models. All parameters like surface velocity, particle concentration, particle volume fraction, etc., used in empirical erosion equations are obtained through CFD analysis. CFD modeling parameters like numerical schemes, turbulence models, near-wall treatments, grid strategy and discrete particle model parameters were investigated in detail to develop guidelines for erosion prediction. As part of this effort, the effect of computed results showed good qualitative and quantitative agreement for the benchmark case of flow through an elbow at different flow rates and particle sizes. This paper proposes a new/modified erosion model. The combination of an improved CFD methodology and a new erosion model provides a novel computational approach that accurately predicts the location and magnitude of erosion. Reliable predictive methodology can help improve designs of downhole equipment to mitigate erosion risk as well as provide guidance on repair and maintenance intervals. This will eventually lead to improvement in the reliability and safety of downhole tool operation.