Authors: Chenxi Wang (University of Alberta) | Yu Pang (University of Alberta) | Jesus Montero (University of Alberta) | Mohammad Haftani (University of Alberta) | Vahidoddin Fattahpour (RGL Reservoir Management Inc.) | Mahdi Mahmoudi (RGL Reservoir Management Inc.) | Alireza Nouri (University of Alberta)

Thermal stimulation techniques are widely used to exploit Western Canadian heavy oil assets. These techniques rely on injection of steam into the formation, inducing complex geomechanical stresses in the reservoir and surrounding strata during the life cycle of the project. In SAGD wells, the collapsed oil sand around the liner undergoes a stress buildup which causes gradual sand compaction. The stress buildup is influenced by several factors such as the in-situ stresses, reservoir poroelastic and thermal expansion, and reservoir shear dilation. However, the impact of stress level and anisotropy around the liner is not properly accounted for in previous research on slotted liner design. This paper investigates the effect of anisotropic stress buildup around slotted liners on their sanding and plugging performance under multiphase flow conditions.

A Scaled Completion Testing (SCT) facility was utilized to emulate multi-axial stress and multiphase flow conditions near the sand control liner. Brine, oil, and gas were used as flowing fluids. Sand-pack samples were prepared using commercial sands by matching the particle size, shape and, composition of the McMurray Formation oil sands. A constant lateral stress and several axial stresses were applied to simulate the stress conditions around the liner. The three-phase flow condition was used to evaluate the role of the steam breakthrough on the liner performance.

Experimental results indicate the critical role of stress conditions around the liner on its sanding and plugging responses. Results show gradual sand-pack compaction with the gradual increase of the axial stress. Higher axial stresses result in a smaller amount of produced sand, which can be attributed to the stronger inter-particle frictional resistance, hence, stronger and more stable sand bridges behind the slots. The higher compaction results in a lower porosity and permeability, hence, altering the plugging and sanding response of the liner. Also, higher retained permeabilities are found for stronger anisotropic stress conditions. Besides, it is found that the three-phase flow condition could cause a stronger fines migration and production, compared to single-phase flow.

The results of this study indicate that the stress and multiphase flow effects are crucial factors in the evaluation of slotted liner performance. The findings from the innovative experimental studies provide insights into the practicability of evaluating slotted liner performance with the consideration of sophisticated field conditions and optimizing the selection of the slotted liner aperture for the entire well lifespan.

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Authors: Anas Sidahmed (University of Alberta) | Alireza Nouri (University of Alberta) | Mohammad Kyanpour (RGL Reservoir Management Inc.) | Siavash Nejadi (University of Alberta) | Brent Fermaniuk (RGL Reservoir Management Inc.)

Canada has enormous oil reserves which ranks third worldwide with proven oil reserves of 171 billion barrels. Alberta alone contributes with 165.4 billion barrels found in oil sands. However, the oil in oil sands is extremely viscous, and only 10% is recoverable through open-pit mining. In-situ thermal recovery methods such as Steam-Assisted Gravity Drainage (SAGD) have been developed and adopted as an efficient means to unlock the oil sands reserves.

Different reservoir geological settings and long horizontal wells impose limitations and operational challenges on the implementation of SAGD technology. Wellbore trajectory excursions or undulations- unintentionally generated trajectory deviations due to suboptimal drilling operations- are some of the complications that lead to non-uniform steam chamber conformance, high cumulative Steam-Oil Ratio (cSOR) and low bitumen recovery.

Conventional dual-string completion scheme (a short tubing landed at the heel, and a long tubing landed at the toe) has been widely adopted in most of the SAGD operations. Such configurations allow steam injection at two points: the toe and the heel sections of the horizontal well. However, these completions have demonstrated poor efficiency when reservoir/well complications exist. Tubing-deployed Flow Control Devices (FCD’s) have been introduced to offer high flexibility in delivering specific amounts of steam to designated areas (such as low permeability zones) and ensure uniform development of steam chamber in the reservoir. The work in this thesis presents the results of a numerical effort for optimizing the design of Outflow Control Devices (OCD’s) in SAGD wells for different scenarios of well pair trajectory excursions.

A coupled wellbore-reservoir SAGD simulation model was constructed to optimize the placement and number of ports in every single OCD. Three different cases were generated from the constructed basic SAGD model with each case having a specific well pair trajectory which causes variable lateral distances between the well pair.

Results of the optimized OCD’s cases demonstrate a higher SAGD efficiency compared to their corresponding conventional dual-string cases. Those enhancements resulted in a higher steam chamber conformance, a higher cumulative oil production, and an improved Net Present Value (NPV).

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Authors: M. Roostaei (University of Alberta) | Y. Guo (University of Alberta) | A. Velayati (University of Alberta) | A. Nouri (University of Alberta) | V. Fattahpour (RGL Reservoir Management) | M. Mahmoudi (RGL Reservoir Management)

Unconsolidated sand was packed on a slotted-liner coupon in large-scale sand retention tests (SRT) and was subjected to several stress conditions, corresponding to the evolving stress conditions during the life cycle of a SAGD producer. Cumulative produced sand at the end of testing was measured as the indicator for sand control performance. Retained permeability was calculated by measuring pressure drops near the liner and was considered as the quantification of the flow performance of the liner. Experimental results indicate the liner performance is significantly affected by the stress induced compaction of the oil sand. The stress results in the sand compaction, leading to a denser sand, hence, a lower porosity and permeability. The lower porosity results in a higher pore-scale flow velocity, which can trigger more fines mobilization, hence, a higher skin buildup. With respect to sanding, the higher stress can stabilize the sand bridges: Increased normal forces between near-slot sand particles result in a higher inter-particle friction, hence, more stable sand bridges and less produced sand. The lower and upper bounds of slot window are governed by plugging and sand production, respectively. Experimental results indicate an upward shift in both the lower and upper bounds at elevated stress conditions.

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Authors: Arian Velayati (University of Alberta) | Morteza Roostaei (RGL Reservoir Management Inc.) | Vahidoddin Fattahpour (RGL Reservoir Management Inc.) | Mahdi Mahmoudi (RGL Reservoir Management Inc.) | Alireza Nouri (University of Alberta) | Ahmad Alkouh (College of Technical Studies) | Brent Fermaniuk (RGL Reservoir Management Inc.) | Mohammad Kyanpour (RGL Reservoir Management Inc.)

Several parameters affect the skin factor of the cased and perforated (C&P) wells completed with slotted liners. Existing skin factor models for slotted liners account for such factors as the flow convergence, pressure drop and partial production but neglect phenomena such as partial plugging of the screen or near-wellbore permeability alterations during the production. This paper discusses these factors and incorporates them into a skin model using a finite volume simulation.

The finite volume analysis evaluates the skin factor as a result of pressure drop in the gap between the casing wall and the slotted liner. This skin model accounts for: 1) the perforation density and phasing, 2) slotted liner specifications, and 3) different amount of sand accumulation in the annular space between the casing and the sand screen. A semi-analytical pressure drop model is also linked to the numerical model to incorporate the skin factor due to flow convergence behind the perforations.

The results of finite volume analysis reveal that a low perforation density would behave close to the open-hole completion for sand-free casing-liner annular space. Conversely, pressure drops were found to be significant for a partially or totally filled space. Additionally, it was found that the optimum completion design occurs if the slotted liner joints are in line with the casing joints. Besides, a partially perforated casing or a partially open sand screen increases the distance fluids have to travel in the annular space and intensifies the skin factor.

This paper provides skin models derived for vertical and perforated wells completed with slotted liner sand screens using the finite volume simulations. Each part of the model has been verified against existing numerical models in the literature. The model improves the understanding of flow performance of the sand screens and skin factor, which in turn leads to a better design of sand control completions.

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Authors: Mahdi Mahmoudi (RGL Reservoir Management) | Vahidoddin Fattahpour (RGL Reservoir Management) | Arian Velayati (University of Alberta) | Morteza Roostaei (RGL Reservoir Management) | Mohammad Kyanpour (RGL Reservoir Management) | Ahmad Alkouh (College of Technological Studies) | Colby Sutton (RGL Reservoir Management) | Brent Fermaniuk (RGL Reservoir Management) | Alireza Nouri (University of Alberta)

Sand control and sand management require a rigorous assessment of several contributing factors including the sand facies variation, fluid composition, near-wellbore velocities, interaction of the sand control with other completion tools and operational practices. A multivariate approach or risk analysis is required to consider the relative role of each parameter in the overall design for reliable and robust sand control. This paper introduces a qualitative risk factor model for this purpose.

In this research, a series of Sand Retention Tests (SRT) was conducted, and results were used to formulate a set of design criteria for slotted liners. The proposed criteria specify both the slot width and density for different operational conditions and different classes of Particle Size Distribution (PSD) for the McMurray oil sands. The goal is to provide a qualitative rationale for choosing the best liner design that keeps the produced sand and skin within an acceptable level. The test is performed at several flow rates to account for different operational conditions for Steam Assisted Gravity Drainage (SAGD) and Cyclic Steam Stimulation (CSS) wells. A Traffic Light System (TLS) is adopted for presenting the design criteria in which the red and green colors are used to indicate, respectively, unacceptable and acceptable design concerning sanding and plugging. Yellow color in the TLS is also used to indicate marginal design.

Testing results indicate the liner performance is affected by the near-wellbore flow velocities, geochemical composition of the produced water, PSD of the formation sand and fines content, and composition of formation clays. For low near-wellbore velocities and typical produced water composition, conservatively designed narrow slots show a similar performance compared to somewhat wider slots. However, high fluid flow velocities or unfavorable water composition results in excessive plugging of the pore space near the screen leading to significant pressure drops for narrow slots. The new design criteria suggest at low flow rates, slot widths up to three and half times of the mean grain size will result in minimal sand production. At elevated flow rates, however, this range shrinks to somewhere between one and a half to three times the mean grain size.

This paper presents novel design criteria for slotted liners using the results of multi-slot coupons in SRT testing, which is deemed to be more realistic compared to the single-slot coupon experiments in the previous tests. The new design criteria consider not only certain points on the PSD curve (e.g., D50 or D70) but also the shape of the PSD curve, water cut, and gas oil ratio and other parameters.

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Authors: Jesus David Montero Pallares (University of Alberta) | Chenxi Wang (University of Alberta) | Mohammad Haftani (University of Alberta) | Yu Pang (University of Alberta) | Mahdi Mahmoudi (RGL Reservoir Management Inc.) | Vahidoddin Fattahpour (RGL Reservoir Management Inc.) | Alireza Nouri (University of Alberta)

This study presents an evaluation of Wire-Wrapped Screens (WWS) performance for SAGD production wells based on Pre-packed Sand Retention Testing (SRT). The impacts of features such as flow rates, water cut, steam-breakthrough events and fluid properties on flow performance and sand production are analyzed. The aim is to obtain a better understanding of WWS performance under several SAGD operational conditions for typical sand classes in the McMurray Formation in Western Canada.

The study employs a large pre-packed SRT to assess the performance of WWS with different aperture sizes and standard wire geometries. The testing plan includes sand samples with two representative particle size distributions (PSD’s) and fines contents. Testing procedures were designed to capture typical field flow rates, water cut, and steam-breakthrough scenarios. The amount of sand production and pressure drop across the zone of the screen and adjacent sand were measured and used to assess the screen performance. Furthermore, fines production was measured to evaluate plugging tendencies and flow impairment during production.

The experimental results and data analysis show that aperture selection of WWS is dominated by their sand retention ability rather than the flow performance. The relatively high open flow area (OFA) makes WWS less prone to plugging. There is an increase in flow impairment after finalizing the injection scheme (oil+water+gas); however, it is controlled over the acceptable margins even with a narrow aperture. Further, a comparison of initial and final turbidity measurements showed that fines mobilization and production during single-phase brine flow was higher than in two-phase brine-oil flow at the same liquid flow rate. Excessive produced sand was observed for wider slots during the multi-phase (brine, oil, and gas) flow when gas was present, highlighting the impact of the breakthrough of wet steam on sand control performance. Flow impairment and pressure drop evolution were strongly related to the mobilization and accumulation of fines particles in the area close to the screen coupon; it is critical to allow the discharge of fines to maintain a high-retained permeability. Results also signify the importance of adopting adequate flow rates and production scenarios in the testing since variable water cuts and GORs showed to impact both sanding and flow performances.

This research incorporates both single-phase and multiphase flow testing to improve design criteria for wire-wrapped screens and provide an insight into their performance in thermal recovery projects. An improved post-mortem analysis includes fines production measurements to correlate these to the retained permeability caused by the pore plugging, which has hardly been evaluated in previous studies.

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Authors: Mahdi Mahmoudi (RGL Reservoir Management) | Morteza Roostaei (RGL Reservoir Management) | Vahidoddin Fattahpour (RGL Reservoir Management) | Alberto Uzcatequi (RGL Reservoir Management) | Jeff Cyre (RGL Reservoir Management) | Colby Sutton (RGL Reservoir Management) | Brent Fermaniuk (RGL Reservoir Management)

Although several workflows have been developed over the years for the design of the optimal sand control solutions in thermal applications, numerous sand control failures still occur every year. This paper aims at assessing the failure mechanism of different sand control techniques and the factors contributing to the failure by analyzing different failed sand control screen samples recovered from thermal and non-thermal wells.

Several failed standalone screens have been studied, which were collected from various fields and operational conditions. The screens were first inspected visually, and then certain sections of screens/pipes were selected for more detailed study on the failure mechanism. The liners/screens were cut into sections to be studied through SEM-EDX, reflective light microscopy, X-ray micro CT scan and petrographic thin sections to better understand the localized plugging mechanism. Through the studies of several polished sections, a statistical variation of the plugging zone was found. Moreover, we further focused on the critical zones such as the inlet and outlet of the aperture and the zone adjacent to the formation to better investigate the plugging mechanism.

The study on wire wrap screen samples revealed significant plugging of the annular space between the base pipe and the screen. Extensive clay/fines buildup in the annular space led to full to partial clogging in some sections. The base pipe corrosion study reveals that the corrosion mechanism is highly flow dependent since the perforation on the base pipe was enlarged to an oval shape from the original circular shape with its larger axis pointing toward the flow direction. The size of the plugged zone was significantly higher in the outer diameter section where a mixture of the clay and corrosion byproducts plugged the near screen pore space and the screen aperture. Examined premium mesh screen samples showed that the plugging mechanism is highly sensitive to the mesh size and assembly process. The highest pore impairments were associated with mesh screens in which the mesh was directly wrapped around the base pipe causing a reduced annular gap for the flow toward the perforations. The investigation of slotted liner samples showed widest plugging zone in the slot entrance and the lowest on the slot wall. A distinct interplay of the clay and corrosion byproduct led to the adsorption of clay, forming a compacted layer over the slot wall.

This paper reviews the plugging mechanism of the standalone sand control screen obtained from the field to provide first-hand evidence of the plugging mechanism and provides explanations for some of the poor field performances. The results could help engineers to better understand the micro-scale mechanisms leading to sand control plugging.

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Authors: Vahidoddin Fattahpour (RGL Reservoir Management) | Mahdi Mahmoudi (RGL Reservoir Management) | Morteza Roostaei (RGL Reservoir Management) | Patrick Nolan (Canadian Natural Resources Limited) | Colby Sutton (RGL Reservoir Management) | Brent Fermaniuk (RGL Reservoir Management)

With the aging of the SAGD projects and growing number of wells with hot-spot and sand production problems, there is a growing interest in the remedial completion with Inflow Control Device (ICD) and tubing deployed scab liner. The current study aims at better understanding the annular flow, sand transport in the annular space and the expected pressure drops and the produced sand for tubing deployed scab liner sand control solution using a large-scale experimental well simulator.

A large-scale wellbore simulator was developed to study the performance of the tubing deployed scab liner screen as remedial sand control, where the sand entry point, the concentration and PSD of the sand in addition to the flow rate and the ratio of different phases could be controlled precisely. Two-phase flow of oil and brine along with sand could be injected through different ports along the clear pipe, emulating the slurry flow entering into the wellbore. Clear pipe allows visualization of the sand transport and sand accumulation above the tubing deployed scab liner during the fluid injection. An experimental study of the performance of Wire Wrap Screen (WWS) with different aperture sizes is presented in this paper.

Results indicated the requirement of a different approach for designing the correct aperture size for remedial scab liners since using the current design sand control criteria leads to large amount of solid production. It seems that the design of aperture size for scab liners should be more toward the lower bound in comparison with the common screen designs in thermal applications. The sand entry point distance from the tubing deployed scab liner screen position was found to be the critical parameter in the sanding and flow performance of the remedial sand control. Fluid flow in the annulus causes the segregation of sand grains; finer grains are carried with fluid, while coarser grains settle closer to the injection ports. The slurry flow regime in the annulus results in continuous sand production until a stable bridge and later a stable sand bed is formed on top of the tubing deployed scab liner screen. Moreover, results showed that the main pressure drop happens across the nozzles on the tubing, while the pressure drop across the accumulated sand pack in the annulus and coupon was less significant.

This paper introduces an experimental tool for evaluating the tubing deployed scab liner performance as remedial sand control in thermal applications. The developed experimental testing and facility could help to better design and evaluate the remedial tubing deployed scab liner sand control solutions.

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