Variperm Archives

Sand Control Testing for Steam Injection Wells

Injector wells in thermal field developments in Western Canada are usually completed by slotted liners. The purpose of liner installation is preventing sand production after a shut-in, keeping a stable wellbore, and providing an appropriate steam distribution. The objective of this paper is to quantify the role of slot width and slot density on the sanding performance of the liner in cycles of injection and shut-in in a SAGD injection well, through a series of laboratory sand control tests.

A large-scale sand retention testing facility was developed and employed to conduct a series of tests on slotted liner coupons with different slot widths and densities. These tests were tailored to simulate steam injection and backflow during the shut-in. Three representative particle size distributions for the McMurray Formation were used in this study ranging from coarse to fine sand. The experimental set-up allows to measure the amount of produced sand.

Since the produced sand in steam injection wells is not usually cleaned out, the acceptable threshold for sand production in the injector should be more conservative than the same for producer wells. Testing results indicate that the sand control performance of the liner is governed by the slot width and density, and formation particle size distribution. Results indicate a negligible amount of produced sand with gas backflow for a properly designed liner even at very high gas velocities.

Historically, there has been little attention to the sand control design for injector wells. This work highlights the significance of slot density and slot width in the sand control performance for steam injection wells. The paper provides the basis for the proper design of an effective sand control in SAGD injectors.

Download paper

Evaluation of inflow control device performance using computational fluid dynamics

Authors: M. Miersma (University of Alberta) | M. Mahmoudi (RGL Reservoir Management) | V. Fattahpour (RGL Reservoir Management) | L. Li (University of Alberta) | C. F. Lange (University of Alberta)

In steam injection thermal recovery, it is essential to have a uniform flow to improve the recovery and to avoid the localized steam breakthrough which could lead to damage to well completion. In this paper, we propose three quantitative criteria to assess the performance of inflow control devices (ICD) based on computational fluid dynamics (CFD) modeling. The new performance criteria are exemplified in the evaluation of a few basic ICD designs.

To evaluate the response of the ICD to flow rate and fluid type, three new performance criteria, defined as (1) quadratic flow coefficient, (2) viscosity coefficient, and (3) erosion potential, are proposed and evaluated based on a set of CFD simulations. The first criterion measures the flow rate response and the ability of the ICD to restrict high velocity flow, the second quantifies the viscosity sensitivity, and the third predicts the potential for erosion in the device.

Four different liner deployed ICD designs, based on two passive design types (nozzle and channel) and one autonomous design type (Tesla flow diode), were analyzed using a rigorous CFD model. The model includes the surrounding slotted liner and inner tubing to identify any interactions of the ICD with the surrounding completion. The CFD model has been verified for grid and domain independence and it was applied to a range of flow rates representative of the field condition. In addition, simulations were run for a range of single-phase incompressible fluids with varying viscosities.

Using the newly proposed criteria, the ICDs were evaluated and compared. The comparison shows that, of these devices, the diode does the best job of restricting the flow at high flow speeds and low viscosities. At high viscosities, such as in the case of oil, the diode is the least restrictive device. Although the two straight nozzles tested are slightly worse at restricting the flow, they have the lowest erosion potential. Based on this comparison and the proposed criteria, the channel design performs poorly. At low viscosities it does not sufficiently restrict the flow, and at high viscosities it overly restricts the production of oil. It also has a high erosion potential, because of the steep entrance angle.

In this work, a new set of quantifiable criteria are defined and assessed that allow multiple aspects of different ICD designs to be compared simultaneously. Overall, these three criteria give a highly sensitive, quantitative means of comparing ICD designs. With these three criteria together, a more comprehensive comparison can be made in support of selection and improvement of ICDs.

Download paper

Artificial Intelligence Aided CFD Analysis Regime Validation and Selection in Feature-based Cyclic CAD/CFD Interaction Process

Authors: Li, Lei & Lange, Carlos & Ma, Yongsheng

Multiple-view feature modeling is supposed to keep the information consistency during product development. However, for products involving fluid flow, the information consistency is difficult to keep because the application of CFD (Computational Fluid Dynamics) requires specific knowledge and rich experience. To conquer this deficiency, an expert system is proposed to update the CFD analysis view in response to the changes in the design view which is embedded in the CAD fluid functional features. The CAE interface protocol is used to convert the features in the design view into the CAE boundary features in the CFD analysis view. The CFD analysis view also includes the fluid physics features and dynamic physics features which constitute the expert system. The expert system is enhanced with the capability to model complex turbulent phenomena and estimate the discretization error. A case study of contracted pipe is illustrated to show the effectiveness of the proposed multiple-view feature modelling method by comparing with empirical results.

Download paper

Comparative study on performance of standalone screens in thermal wells

Stand-alone sand screen (SAS) is proven to be effective for sand control in unconsolidated sands in thermal wells. The characteristic design parameter to specify SAS is the aperture size, while the Open to Flow Area (OFA) is chosen to balance between the mechanical integrity of the screen, the completion cost, and the plugging risk. The objective of this study is to compare the performance of common SAS types for a certain geological condition.

A series of three-phase large-scale sand retention tests (SRTs) is performed on slotted liner, wire-wrapped screen, and punched screen coupons. The tests are performed using two common representative PSDs of the McMurray Formation. The test matrix includes the common aperture sizes and OFA for each screen and PSD based on the current best practices in the industry. The test procedure is designed to mimic the near wellbore flow velocities, with three-phase flow ranging from 0%-100% water cut and produced gas-oil ratio ranging from 0-277 scf/bbl. The gas flow was supposed to simulate the steam breakthrough incidents. Live measurements are obtained of the sanding amount and pressure drops along the sand-pack and across the screen. Screen plugging is assessed after the completion of each test.

The sanding and flow performance are shown to be a function of the aperture size, PSD, near-wellbore flow velocities, and the water cut. In low fluid flow rates, all the screen types show minimal pressure drops and perform similarly. As near-wellbore velocities increase or gas flow occurs, pressure drops show a significant increase for all devices. Results show OFA, aperture size, and screen type affect the pressure drop and sanding. In all cases, the produced sand in three-phase flow is the determining design parameter for the upper-bound acceptable aperture. The gas flow is observed to accompany large amounts of sanding for larger aperture sizes. Further, test results indicate high pressure drops for three-phase flow conditions. Test results reveal the complexity of the interaction between different design parameters, which affect the sand and flow performance, hence, necessitating an SRT test for each specific case.

This paper presents the results of physical model testing of different standalone screens in terms of flow performance and sand control. This will help to identify the main factors that influence the performance of each specific screen type and develop the rationale for the screen type selection in new developments.

Download paper

Comparative study on the performance of different stand-alone sand control screens in thermal wells

Download paper

Sand Control Design through Assessment of Mathematical Models Representing Particle Size Distribution of Reservoir Sands

Authors: Roostaei, Mohammad & Nouri, Alireza & Fattahpour, V. & Mahmoudi, Mahdi & Izadi, M. & Ghalambor, Ali & Fermaniuk, B.

Standalone screen (SAS) design conventionally relies on particle size distribution (PSD) of the reservoir sands. The sand control systems generally use D-values, which are certain points on the PSD curve. The D-values are usually determined by a linear interpretation between adjacent measured points on the PSD curve. However, the linear interpretation could result in a significant error in the D-value estimation, particularly when measured PSD points are limited and the uniformity coefficient is high. Using the mathematical representation of the PSD is an efficient method to mitigate these errors. The aim of this paper is to assess the performance of different mathematical models to find the most suitable equation that can describe a given PSD.

The study collected a large databank of PSDs from published SPE papers and historical drilling reports. These data indicate significant variations in the PSD for different reservoirs and geographical areas. The literature review identified more than 30 mathematical equations that have been developed and used to represent the PSD curves. Different statistical comparators, namely, adjusted R-squared, Akaike’s Information Criterion (AIC), Geometric Mean Error Ratio, and Adjusted Root Mean Square Error were used to evaluate the match between the measured PSD data with the calculated PSD from the formulae. The curve fit performance of the equations for the overall data set as well as PSD measurement techniques were studied. A particular attention was paid towards investigating the effect of fines content on the match quality for the calculated versus measured curves.

It was found that certain equations are better suited for the PSD database used in this investigation. In particular, Modified Logestic Growth, Fredlund, Sigmoid and Weibull models show the best performance for a larger number of cases (highest adjusted R-squared, lowest Sum of Squared of Errors predictions (SSE), and very low AIC). Some of the models show superior performance for limited number of PSDs. Additionally, the performance of PSD parameterized models is affected by soil texture: For higher fines content, the performance of equations tends to deteriorate. Moreover, it appears the PSD measurement techenique can influence the performance of the equations. Since the majority of the PSD resources used here did not mention their method of measurement, the effect of measurement technique could only be tested for a limited data, which indicates the measurement technique may impact the match quality.

Fitting of parameterized models to measured PSD curves, although well known in sedimentology and soil sciences, is a relatively unexplored area in petroleum applications. Mathematical representation of the PSD curve improves the accuracy of D-values determination, hence, the sand control design. This mathematical representation could result in a more scientific classification of the PSDs for sand control design and sand control testing purposes.

Download paper

A Large-Scale Sand Retention Test Facility for Evaluation and Selection of Optimal Standalone Sand Screen for Injection Wells in Thermal Operations

Sand production is not usually considered a major concern during the injection phase in injection wells. However, well shut-in for service requirements or sudden pump failure, hence the backflow towards the wellbore and potential generation of water hammer pressure pulsing, can lead to massive sand production under favorable conditions. With the aim of sanding prevention, this paper examines the design criteria for standalone screens (SAS) in injection wells using a novel sand control testing facility.

This paper presents a new large-scale sand retention testing (SRT) facility to simulate the effect of pressure pulsation and backflow in injection wells on the sand control performance of SAS. The SRT facility can be used in the selection of the best sand control method for injector wells. It can be also used to provide further understanding on the impact of formation damage on well injectivity decline, as well as study the effect of water hammer pressure pulsation on sand production in injection wells.

Test results show a rapid fall off in the pressure and drastically high backflow rates due to the sudden shut-in. Higher pressure drops are observed to result in a greater backflow volume and a longer backflow period. Results also show that the slot width has a drastic influence on the sanding performance of the screen. Testing observations, for the studied PSD, indicate that the injection well requires narrower slots 1.4 D10 to meet the sand production requirements due to a high fluidization potential in the near-screen zone. Higher flow velocities during the backflow period and the tossing effect caused by the pressure waves increase the sanding potential. The produced sand during the backflow period, is observed to mainly relate to the ratio of the slot width to the mean formation grain size. It is observed that higher effective stresses around the screen work towards stabilizing the sand bridges and reducing the amount of produced sand.

This paper presents a new experimental test facility for the sand control type selection and evaluation for injection wells with the aim of limiting the amount of produced sand and sustaining the wellbore injectivity. The proposed testing facility allows the performance comparison of different sand control devices and designs.

Download paper

Design Optimization of Slotted Liner Completions in Horizontal Wells: An Analytical Skin Factor Model Verified by Computational Fluid Dynamics and Experimental Sand Retention Tests

The term skin is used to describe pressure drop caused by a flow restriction near the wellbore. The skin factor of wells completed using slotted liners can be explained by a number of phenomena including: the flow across the slots, flow convergence towards slots, near wellbore permeability, and occlusion of liner open area due to corrosion and scale deposition. This paper introduces an analytical skin model for the slotted liner, which incorporates these phenomena, and can be used to optimize the slotted liner design. The introduced analytical model was verified by physical and Computational Fluid Dynamics (CFD) models.

The proposed analytical skin factor model for slotted liners is based on slot width, slot density, the spatial distribution of slots, and near-liner permeability. The model also incorporates partial plugging of slots. The model is validated using experimental Sand Retention Testing (SRT) data. A series of SRT experiments were conducted at different flow rates for two Particle Size Distributions (PSD) from the McMurray Formation in Northern Alberta. The experiments were also modeled by the CFD to better understand the flow dynamic near the liner.

Results of the analytical model and experimental tests were generally in agreement. However, results of the analytical model deviate from experimental tests for narrow slots and high flow rates. In these cases, the analytical model predicts smaller skin than the experimental tests. For cases related to narrow slots and higher velocity the pore plugging close to the liner is significant which was not modeled in the analytical model. Moreover, for very fine sand (low permeability) sand-pack the deviation from the experimental results is higher in comparison with medium uniform sand (higher permeability) sand-pack. CFD simulations showed the effect of the slot width on the depth of the convergence zone, which is not included in the analytical model. Since the analytical model follows the experimental results for common flow rates in thermal production, the model could be used to assess the skin for different possible designs and choose the best slot specifications that minimize the skin.

This paper presents the details of an analytical model for the skin factor verified by experimental data and CFD simulation. This analytical model can be used to optimize the liner specification for the best flow performance. This paper also outlines the limitations of the analytical models for calculation the skin/pressure drop.

Download paper

Intelligent CFD analysis regime validation and selection in feature-based cyclic CAD/CFD interaction process

Authors: Lei Li, C. F. Lange, Yongsheng Ma

Multi-view feature modelling provides a specific view for each phase in product development. The analysis view should be fully integrated with CAD models in a multi-view product development environment for simulation-based design. In the development of fluid flow products, CFD (Computational Fluid Dynamics) is increasingly used as an advanced support. However, the successful application of CFD requires special knowledge and rich experience, which is a barrier for the conversion from the design view to the analysis view, and the maintenance of information consistency. Several approaches to multiple feature views have been proposed, such as design by features, feature recognition and feature conversion. In one-way feature conversion, features in a specific view are usually derived from the original design view. Bronsvoort and Noort put forward a multiple-way approach which enables a designer to modify the product model from an arbitrary view. In this paper, the CAE interface protocol is used to convert the features in the design view into the CAE boundary features [5] in the analysis view. Based on the physical knowledge, an expert system is established to further process those features and generate a robust simulation model with the help of fluid physics features and dynamic physics features in the analysis view.

Download paper

CFD expert system for steam simulation

Authors: Li, Lei & Ma, Yongsheng & Lange, Carlos

The complexity in configuring the CFD solver imposes a barrier for users to efficiently setup the solver and obtain satisfactory results. Such kind of deficiency becomes more obvious when it comes to simulation-based design where the CFD solver is expected to respond to design changes automatically. By applying artificial intelligence, expert systems can be used to capture the knowledge involved in CFD simulation and then assist the solver configuration. This paper proposes an expert system for both dry and wet steam simulation. According to the product design, the expert system is able to select the right module to model the steam flow. Based on the derived non-dimensional numbers, appropriate physics models can be selected to run the simulation. Grid adaption, higher order schemes, and a subroutine for advanced turbulence models help to improve the accuracy of the CFD model after rounds of simulation. The output of the expert system is a robust simulation model with accurate results which are guaranteed by flow regime validation, grid independence analysis, and error estimation. The effectiveness of the proposed system is demonstrated by the analysis of a contracted pipe. In dry steam simulation scenario, the error induced by the expert system is smaller than that of the traditional ANSYS batch mode. The results obtained by the expert system also match well the empirical results when it comes to wet steam simulation.

Download paper