Assessment of Existing Design Criteria for Wire-Wrapped Screens in Thermal Wells

A three-phase flow large pre-packed Sand Retention Test (SRT) assembly was employed with different screen specifications for typical sand prints within McMurray Formation in Western Canada. Cumulative sand production and retained permeability are utilized as the sand control and plugging performance indicators. Measurements indicate that sand production is highly dependent on the flow dynamics and near-wellbore velocities. Most aperture sizes smaller than two and half times of the mean grain size show a good performance during liquid stages, but wider apertures dramatically failed during steam-breakthrough emulation (three-phase flow). Wire-wrapped screens exhibited an excellent flow performance due to the high open-to-Flow Area (OFA). Existing criteria provide reasonable aperture sizes, especially for finer sands and challenging conditions such as steaminflux. However, the criteria underestimate the slot aperture for coarser sands and conventional liquid production operations. This conservative approach may result in lower productivity performances and diminish the benefits of the high OFA.

Download paper

An Analytical Model for Hydraulic Fracture Initiation in Deviated Wellbores

Authors: M. Roostaei (RGL Reservoir Management Inc.) | A. Sharbatian (RGL Reservoir Management Inc.) | V. Fattahpour (RGL Reservoir Management Inc.) | M. Mahmoudi (RGL Reservoir Management Inc.) | A. Velayati (University of Alberta, Edmonton) | A. Ghalambor (Oil Center Research International) | A. Nouri (University of Alberta, Edmonton)

This paper presents an analytical model to calculate the hydraulic fracture initiation pressure from an arbitrarily oriented wellbore in an elastic medium with and without perforations and investigates the competition between axial and transverse fractures. The model predicts the location of fractures and their initiation pressures, in relation to the in-situ stress condition and wellbore azimuth and inclination. Not only has the model been applied to different states of in-situ stress and wellbore orientations, but also the results have been presented in terms of non-dimensional parameters to improve the applicability of the study.

The presence of both transverse and axial hydraulic fractures can cause significant near-wellbore tortuosity. Besides, the stress distribution around the perforation tunnel has a substantial impact on the fracture initiation pressure and thus the fracture geometry near the wellbore. The introduced analytical model was verified against existing models. The model has been successfully applied to different conditions of in-situ stress and wellbore orientations, which were not addressed in previous studies. The results can be used to obtain the optimum well and perforation design in deviated wellbores by providing the minimum fracture initiation pressure and the perforation orientation that minimizes the near-wellbore fracture tortuosity.

Download paper

Investigation of the antifouling mechanism of electroless nickel–phosphorus coating against sand and bitumen

Antifouling coatings have attracted much attention in applications of industrial equipment and systems. The accumulation of foulants on downhole equipment used in the steam-assisted gravity drainage process for oil sand extraction reduces the recovery efficiency of bitumen and causes failures of the equipment. Applying suitable coatings is expected to endow antifouling property to the related substrate surface. Understanding the interaction mechanism between foulants and antifouling coating is critical for the evaluation and prediction of antifouling performance. In this work, antifouling coating consisting of Ni and P was prepared on the L80 carbon steel substrate, which is a commonly used material in downhole equipment. The surface properties (e.g., morphology and surface energy) of the Ni–P coating and pristine L80 substrates were characterized. The intermolecular and surface forces between typical foulants (e.g., silica and bitumen-coated silica) and Ni–P coated and uncoated L80 substrates were directly measured using the atomic force microscope colloidal probe technique to investigate the fouling mechanisms and predict the fouling behaviors of the foulants at the nanoscale. It was found that the Ni–P coating possessed lower surface energy, weaker attractive van der Waals interaction, and smaller adhesion to both silica and bitumen as compared to the uncoated L80 substrate. Bulk soaking experiments were also conducted accordingly which further demonstrated the antifouling performance of Ni–P coating against silica and bitumen, agreeing well with the surface force measurements. This work has improved the fundamental understanding of fouling behaviors of silica and bitumen and the antifouling mechanism of Ni–P coating at the nanoscale, with potential applications in many related processes in chemical and petroleum industries. The methodologies employed in this work can be readily extended for investigating fouling and antifouling mechanisms of different materials in various engineering fields.

Download paper

Unsupervised and Self-Adaptive Algorithm for Particle Size Distribution Clustering. Presented at the Geoconvention

Authors: Izadi, Hossein & Fattahpour, Vahidoddin & Roostaei, Morteza & Mahmoudi, Mahdi & Devere-Bennett, Noel.

Particle size distributions (PSDs) plays an important role in designing sand control screens. Using different techniques (Dry Sieving, LPSA, and Dynamic Image Analysis (DIA)), large number of PSDs could be measured for core samples in a certain project. Moreover, large-scale sand retention tests are becoming common practice in recent years. These tests usually use duplicated sand mixtures of representative PSDs. Therefore, clustering the PSD data is essential for sand control design and sand retention tests. Supervised and unsupervised machine learning algorithms are getting more attention in computational petroleum engineering. Usually there is no clear idea that how many clusters are supposed to be detected in each PSD database. Therefore, due to the limitation for setting the number of clusters, PSD clustering could not be accomplished using conventional clustering algorithms such as k-means or artificial neural networks. As a new approach, PSD clustering based on an incremental clustering algorithm is used here. The proposed algorithm has online incremental learning capability and it is based on adaptive resonance theory (ART). Besides, the number of clusters is not needed to be assigned as an input parameter in the algorithm. The algorithm, based on a self-adaptation approach, tries to minimize the number of clusters. Accordingly, it is appropriate for PSD clustering of big databases. The proposed algorithm can be used in industrial applications such as sand control design and sand control evaluation testing.

Download paper

An Investigation into the Effect of Brine Salinity on Fines Migration in SAGD Operations

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

In Steam Assisted Gravity Drainage (SAGD) operations, condensed water dissolves the formation minerals and mixes with formation water, and its salinity changes over time. For the salinity levels below a critical salt concentration, brine reacts with the formation clays and affects their mobilization towards the production well. Migrated fine particles may plug the pore spaces around the well and reduce wellbore productivity. This paper aims to investigate the impact of water salinity on fines migration and permeability reduction.

A large-scale pre-packed Sand Retention Tests (SRT) facility was employed to simulate SAGD well conditions. Brine with different NaCl salt concentrations was injected into synthetic sand-pack samples that are representative of the McMurray Formation. Flow rates were varied during the test, and fines migration along the sand-pack was traced. Differential pressures along the sand pack were recorded to calculate the permeability changes during the test. Samples of produced water were collected immediately below the coupon to measure the fines concentration. Testing parameters such as pH, clay mineralogy, temperature, and sand control specifications were kept constant in all tests.

Fines concentration in the produced water during the test and retained permeability were considered as the indicators of the fines migration inside the sand-pack. Results of step-rate testing display a jump in fines concentration in produced water right after each flow rate increase. Besides, fines concentration results show that fines migration was insignificant when using brine with high salt concentrations. Fines migration was stronger for a relatively narrow salinity range with low NaCl concentrations, resulting in the highest pore plugging. The findings in this research are consistent with past studies which relate clay dispersion to the zeta potential of clay materials: the higher the zeta potential, the stronger the fines dispersion and migration.

Based on this study, it is recommended that the operating companies monitor the chemical properties of the produced water. Field operators could preserve the reservoir productivity by manipulating the formation salinities to lower the dispersion and detachment of fines and their migration towards the production well.

Download paper

Parametric Study of the Frequency of Bubble Formation at a Single Orifice With Liquid Cross-Flow

Authors: Miguel A. Balzan, Franz Hernandez, Carlos F. Lange, Brian A. Fleck

The bubble formation frequency from a single-orifice nozzle subjected to the effects of a crossflowing liquid was investigated using high-speed shadowgraphy, combined with image analysis and signal processing techniques. The effects of the nozzle dimensions, orientation within the conduit, liquid cross-flow velocity, and gas mass flow rate were evaluated. Water and air were the working fluids. Existing expressions in the literature were compared to the experimental values obtained. The expressions showed modest agreement with the experimental mean average frequency magnitude. It was found that increasing the gas injection diameter could decrease the bubbling frequency approximately 12% until reaching a certain value (0.52 mm). Further increasing the nozzle dimensions increase the frequency by around 20%. Bubbling frequency is more sensitive to the liquid velocity where changes up to 63% occurred when the velocity was raised from 3.1 to 4.3 m/s. Increasing gas mass flow rates decreased the gas jet breakup frequency in all cases. This phenomenon was primarily attributed to changes in the bubbling mode from discrete bubbling to pulsating and jetting modes. The nozzle orientation plays a role in modifying the bubbling frequency, having a higher magnitude when oriented against gravity.

Download paper

Smeared modeling of hydraulic fracture using partially coupled reservoir and geomechanics simulators

Authors: Morteza Roostaei, Siavash Taghipoor, Alireza Nouri, Vahidoddin Fattahpour, Dave Chan

A smeared fracture type hydraulic fracture simulator is developed through numerical coupling between an in-house reservoir simulator and a geomechanical commercial software (FLAC2D). The new package falls within the category of partially decoupled model and is versatile, flexible and efficient. This approach can be used to couple any other advanced commercial fluid flow or geomechanical simulators for an accurate description of the initiation and propagation of hydraulic fractures.

The paper contains a discussion of the partial coupling technique to link fluid flow and geomechanical calculations in modeling fracture initiation and propagation. The models use a common gridblock for the fracture and reservoir and use the deformation calculations to update the porosity and permeability. The method captures the interactive effects of the fracture on reservoir fluid flow and formation geomechanics through stress dependent permeability and porosity.

The developed smeared fracture model can capture both tensile and shear fractures in the formation. Major features of this model include modeling poroelasticity and plasticity, matrix flow, shear and tensile fracturing with concomitant permeability enhancement, saturation-dependent permeability, stress-dependent stiffness and gradual degradation of oil sands due to dilatant shear deformation. The model has been applied to numerically simulate field size hydraulic fracturing in oil sands during cold-water injection to show the predictive capability of the simulator.

Download paper

Evaluation of the scaling resistance of different coating and material for thermal operations

Several alloys and coating techniques have been used by industry for their anti-corrosion and anti-fouling properties in the industry. One of the major problems in thermal operation is related to silica and calcium carbonate scale. In this study, we intend to better understanding the relative scaling resistance performance of different coatings and alloys exposed to typical formation water in thermal operations. This paper provides a study on failed samples collected from various projects in Western Canada. Moreover, a review of research work on scaling properties of different materials in thermal applications will be presented.

Different failed screens were collected from various projects in Western Canada. Thin section analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) joined with energy dispersive X-ray spectroscopy (EDX) were performed on collected failed pipeline samples to determine the composition of the scale material. Obtained results revealed that the main scaling materials are silicates and carbonates. Chert, clays and carbonates act as cement to bind sand grains (mainly quartz).

Later, a review was performed on an ongoing investigation regarding the materials and coatings for improving the anti-scaling properties. Bulk scaling tests, Atomic Force Microscopy (AFM), and in-situ field trials were used to investigate the anti-scaling properties of two RGL proprietary grade materials, proRC05, and proRS06, as well as electroless nickel (EN) coating. Carbon steel L80, carbon steel 4140 and EN30B alloy steel were used for comparison. The microstructural change of the material surface was studied using complementary techniques (e.g., XRD, SEM, and EDX). The tests have been performed under a complex chemical environment that represents the chemistry of the near screen condition in thermal operation, to assess the relative performance of different coatings. Among proRC05, proRS06, 4140 carbon steel and EN30B alloy steel, the anti-scaling performance follows the order of proRC05 > proRS06 > 4140 carbon steel > EN30B alloy steel. Comparison between EN-coated and uncoated samples shows that the EN-coated carbon steel L80 provides better anti-corrosion and fouling resistance performance with a small amount of iron oxides and silica foulants. Field trials of EN-coated technology have been also proven to be effective.

This work provides a detailed review on recent attempts on evaluating the anti-scaling properties of various materials and coatings to minimize the silica and calcium carbonate scale. Furthermore, field trials were reviewed for evaluating the scaling and corrosion properties in thermal production. The results of this study will help engineers select material for projects in which silica and calcium carbonate scaling could be a significant issue.

Download paper

Optimization of Outflow Control Devices Placement and Design in SAGD Wells with Trajectory Excursions

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).

Download paper

Design Optimization of Slotted Liner Completions in Cased and Perforated Wells: A Numerical Skin Model

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.

Download paper