Qiu, Xiaoyong (University of Alberta) | Pan, Minfei (University of Alberta) | Gong, Lu (University of Alberta) | Huang, Jun (University of Alberta) | Mahmoudi, Mahdi (RGL Reservoir Management Inc.) | Sabbagh, Reza (RGL Reservoir Management Inc.) | Fattahpour, Vahidoddin (RGL Reservoir Management Inc.) | Sutton, Colby (RGL Reservoir Management Inc.) | Luo, Jing-Li (University of Alberta) | Zeng, Hongbo (University of Alberta)
Application of inflow control devices (ICDs) in a thermal producer has proven to be an effective solution to increase the wellbore performance and reduce production problems such as steam breakthrough. In challenging areas where the potential for scaling is greater, there is concern that the ICD could plug. Often, operators face severe nozzle plugging nozzles with silica and calcium carbonate scales. This work is intended to investigate the relative resistance of various materials to silica or calcium carbonate scaling. Bulk scaling tests on four types of coupons (4140 carbon steel, EN30B alloy steel, and two proprietary grades, proRC05 and proRS06) were conducted in the solution with similar chemical composition of common produced water in steam-assisted gravity drainage (SAGD), cyclic steam stimulation, and steamflood projects in Western Canada. Both silica scaling and calcium carbonate scaling tests were carried out to evaluate the anti-scaling performance of the material commonly used in manufacturing ICDs for these projects. The microstructure of the scale on the coupons after scaling tests were completed was investigated using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Force measurement using the atomic force microscopy (AFM) colloidal probe technique was applied to interpret the microscopic interactions between different substrate surfaces and silica or calcium carbonate particles. The detailed investigation on evaluating the scaling resistance of different materials provides useful insights into the selection of suitable materials for projects where scaling exists as a major problem.
Evaluating of VIT performance
Statistics, Finite Element Analysis (FEA), Computational Fluid Dynamics (CFD)
The utilization of Vacuum Insulated Tubing (VIT) is necessitated by the growing oil and gas development in northern regions of the Earth and application of thermal oil recovery methods. Conceptually, VIT consists of two (external and internal) pipes coaxially fixed at the ends, with the annular space filled with thermal insulation including getters (gas absorbers). After the pipes are assembled, air is evacuated from the annular space to create vacuum. Getters are fully activating within vacuumizing. Prior to commercial utilization at Gazprom, the VIT was tested at the Gazprom VNIIGAZ Institute (Russia) on a dedicated thermophysical testing bench. Tests were designed to measure the Coefficient of thermal conductivity (k-factor) of the VIT Vacuum Shield Thermal Insulation. Results obtained during the tests are as follows: with hot air (84…93°C) passing through the tube, the temperature of its external surface remained within the range of 28…35°C, while k-factor was 0.004…0.008 W/(m*K). Gazprom requirements k-factor with max. 0.012 W/(m*K). When VIT successfully passed bench tests, they were approved for utilization in the commercial development of the Bovanenkovskoye field operated by Gazprom. In order to gauge heat flux and effective k-factor of VIT walls at different gas flow rates and fluid temperatures, the design provides for satellite pipes to be installed within the gas well's cement column. At the moment, wellhead soil temperature observations are carried out regularly at VIT-equipped wells. Some gas wells have been monitored for 3 years now. The results of monitoring of 18 well pads (163 wells) the temperature stabilization of the permafrost soil at which is carried out only through the operation of seasonally active cooling systems (without the use of VIT) show temperature increases in the soil along the wellbore. Wells operated with VIT and cooling systems keep freezing temperatures within the cement column throughout the entire annual cycle. For steam injection technologies, may be used theoretically estimation about how temperature of steam decreases from top to bottom of well depending on VIT k-factor and length of VIT string. Such information needs for VIT well design.
Empirical information about VIT utilization
Part 1 of this study (SPE-187956-PA) presented a method to calculate the liquid pool level from temperature profile in observation wells, provided new insight into how factors like wellbore drawdown can compromise subcool control and cause steam breakthrough, and illustrated how liquid pool depletion may result in uncontrolled steam coning with time. In Part 1, the algebraic equation for liquid pool depletion based on wellbore drawdown, subcool and emulsion productivity was generated. However, not included in Part 1 was an examination of the effect of localized hot spots on well control, which is the focus of this paper.
As a part of this study, the effect of localized hot spots is mathematically included as a virtual skin factor representing the hot spot length in the algebraic equation for liquid pool depletion. The results of this work suggest that longer hot-spot will yield to lower differential pressure and make it harder to control the steam breakthrough by choking the well at a given rate. Two important finding of this work are that: (1) the zero-differential pressure (or steam coning) in reservoirs with higher permeabilities occurs in shorter hot-spots; and (2) it is harder to control the steam coning in high permeability reservoirs after hot-spots develop.
Flow control devices (FCDs) have been extensively used in horizontal wells for conventional oil and gas production in order to prevent early water break-through or gas coning. The benefits associated with this technology in SAGD industry have been studied with reservoir simulations and validated with field experience. The cost comparisons of bridge plug at the toe and scab-liners in heel with FCD installation along the producer is typically not large, which makes the FCDs the more attractive full life cycle option in producers experiencing hot-spots. Although installation of FCDs to prevent steam coning after steam breakthrough and hot-spots creation is part of the common practice as retrofits by SAGD operators, in recent years FCDs are now often installed to improve SAGD well pair performance as part of the initial completion. Although FCDs have demonstrated potential for improving recovery in SAGD production wells, vendors use a variety of approaches when designing their FCDs independent of the liquid pool element resulting in many cases where the field results showed no improvement. It is necessary to accurately characterize different FCDs under different reservoir conditions. In this study, the liner deployed FCD and liquid pool systems are coupled, and two criteria are suggested as for a design of liner deployed FCDs on the basis of pressure drop ratio of FCD relative to the liquid pool (ΔPFCD / ΔPpool) and the coefficient of variation (CoV) of inflow for the liner deployed FCD wellbore (CoVFCD).
Liners in the unconsolidated sand reservoirs common to SAGD applications are subjected to a unique combination of loads that arise due to re-established formation stresses combined with large temperature changes. Temperature changes that occur following frictional constraint of the liner induce axial strain that can yield the liner, which reduces its capacity to resist ovalisation under non-uniform re-established formation stresses. These types of liner deformations are undesirable because they can restrict wellbore access, compromise other liner functions (e.g., sand or inflow control) or, in the worst case, drive a complete collapse failure.
The magnitude, non-uniformity, and evolution of re-established formation stresses present in SAGD wells remains highly uncertain. Consequently, many of the liner designs deployed in early wells relied on approximations of the re-established formation stresses, for example, from experimental testing and analytical approximations provided by van den Hoek et. al. (2000b).
Industry experience with liners deployed in thermal applications has been mixed. Some projects have indicated very low rates of liner failures. Conversely, other projects in the same formations, or in formations with similar characteristics, have experienced higher failure rates with measured liner ovalisations that suggest re-established formation stress (REFS) distributions can be more severe than previously assumed.
This paper describes how REFS impacts long-term integrity of thermal liners in unconsolidated sand reservoirs and how uncertainty in those stresses can be the difference between success and failure. The sensitivity of thermal liner structural performance of several common liner systems to re-established formation stresses is examined. The results align with field experience and highlight the importance of developing a strong understanding of the downhole loading environment to ensure liner designs promote long-term integrity and sustained production. The paper recommends several activities that will enable industry to more rigorously determine re-established formation stress and proposes refinements to the design and selection basis for liners deployed in thermal wells to manage the risk of deformations that result from thermal loading.
Flow Control Devices (FCDs) in SAGD applications have succeeded and failed to varying degrees and their use has not been overly pervasive or fully accepted yet. However, recently it has been publicized that FCD technology has achieved upwards of 100% improvement in SAGD oil production and potential improvements in steam oil ratios (SOR), which has continued to spark interest in its application. SAGD reservoirs are inherently heterogeneous and this presents distinct operational complexities when attempting to expedite the production of the oil while attempting to avoid steam breakthrough. Producing the steam reduces the thermal efficiency of the project which results in an increased SOR while also creating a high potential of compromising the mechanical integrity of the production liner. FCDs can mitigate the operational negatives and enhance the operational positives, however, they are not a'silver bullet' for all ailments and their implementation needs to be carefully planned. This paper reviews FCD implementation workflows and highlights recent downhole instrumentation technology advancements that enhance FCD performance analysis and supports better deployment designs that should improve the economic viability of existing and upcoming SAGD projects.
Wang, Chenxi (University of Alberta) | Pang, Yu (University of Alberta) | Montero, Jesus (University of Alberta) | Haftani, Mohammad (University of Alberta) | Fattahpour, Vahidoddin (RGL Reservoir Management Inc.) | Mahmoudi, Mahdi (RGL Reservoir Management Inc.) | Nouri, Alireza (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.
This paper describes a novel approach in drilling production wells while implementing real-time mapping of the Bitumen-Water Contact (BWC) with extra-deep azimuthal resistivity (EDAR) logging while drilling (LWD) service, thereby resulting in an increase of exploited bitumen reserves by optimizing wellbore placement. Within the Athabasca Bitumen Reservoir, the EDAR LWD service confidently mapped the BWC within a range of 2-22 meters below the entire producer wellbore. It also provided an earlier warning of an approaching low resistivity boundary, which allowed the operator to optimize the wellbore placement using real-time proactive steering decisions. In contrast to the existing azimuthal resistivity tools, which have the limited depth of investigation, this approach significantly mitigated the risks of intersecting or giving an incomplete picture of BWC surface. The real-time interpretation of extra-deep azimuthal resistivity data provided better understanding of the lateral distribution of the McMurray Formation along the horizontal wellbore, lithologically varying from clean sand facies to mud-filled channel facies and inclined heterolithic stratification (IHS) facies. The fluid heterogeneity of the reservoir included partial reservoir charging, irregular BWC and lean zones, which compounded lithology complexity within the reservoir. In one of the case studies, 50 percent increase was achieved in actual exploited bitumen reserves in comparison to the projected exploited reserves if drilled per the planned trajectory. This new LWD approach was proven effective while drilling horizontal appraisal and producing wells in unconsolidated formations with high reservoir heterogeneity, it offered an opportunity to better understand the bitumen reservoir and ultimately led to increased production performance of Oil Sands projects.
Ansari, Shadi (University of Alberta) | Yusuf, Yishak (University of Alberta) | Kinsale, Lisa (University of Alberta) | Sabbagh, Reza (RGL Reservoir Management Inc.) | Nobes, David S. (University of Alberta)
Various slotted liners geometries are used to control the sand production in SAGD operations. The geometry of a slot (shape and size) not only affect sand production but it may also influence fine deposition and scaling at the slot entrance. Failure of SAGD wells due to the deposition of particles is an important issue that needs to be investigated at the pore scale. This study provides a fundamental understanding of fines transport and the plugging potential at the entrance of the slots on slotted liners. Three slot profiles including straight shape, keystone shape and seamed (rolled top) shape are examined experimentally in relation to the preceding conditions of pore spaces in porous media. The potential of slot plugging is also studied from the fluid flow motion perspective. This task is achieved by visualization of the flow passing through the near well bore region of different slot geometries using an optical technique, namely, particle image velocimetry. Motion of small particles (
Chen, Xun (Drilling and Production Technology Research Institute of Liaohe Oilfield) | Sun, Shouguo (Drilling and Production Technology Research Institute of Liaohe Oilfield) | Tong, Deshui (Drilling and Production Technology Research Institute of Liaohe Oilfield)
The trajectory control quality is the key technology when using SAGD dual horizontal wells to produce heavy/super heavy oil. The systematic study of trajectory control, CT scanning diagnosis and completion decision has been carried out to guarantee the forming and keeping of steam chamber and enhance the drainage continuity and well-bore life so as to realize economical and effective development. In order to realize precise control of the trajectory of dual horizontal wells, the method with space rectangular target for dual horizontal wells and MGT magnetic-steering technology as its core, has been developed. The CT scanning diagnosis system of SAGD trajectory based on the medical technique has been developed to realize real-time scanning and predicting of the horizontal intervals of the paired horizontal wells. The timely warning and guidance of trajectory adjustment are available when the deviation of the relative position of the two wells from the space rectangular target occurs. After drilling, the space position relation of arbitrary cross-section along the trajectory axis is analyzed through the scanning diagnosis system, and scientific evaluation of the SAGD production is conducted using the SAGD efficiency coefficient method. If the relative position of certain intervals of the two wells is pretty near and there will be the risk of steam breakthrough, physical isolation of the intervals are recommended with casing and thermal packers. The technology has been applied in 12 well-groups in the Liaohe Oilfield, most of the dual horizontal wells have kept favorable position relations. During the injection well of Du-A well-group, due to the large formation dip, the scanning diagnosis system sent out warning signals when 2/3 of the horizontal interval had been drilled, then technicians adjusted the trajectory timely. After drilling, it was found that the distance between the two wells was less than 4m for a 4-meter interval at the 2/3 of the horizontal interval. During the design of completion strings, a blind tube is used to replace the screen in the interval. Two thermally-setting packers are designed respectively for the upper and lower end of the blind tube to realize physical isolation so as to ensure the formation of the steam chamber in the later period and guarantee favorable oil drainage. The overall production of the block has been increased by 15% compared to the wells in the earlier stage. After study, the SAGD trajectory control and completion decision technology with integral constraints of the space rectangular target, real time control of CT scanning diagnosis system and decision guidance after completion has been developed to successfully remove the potential developing troubles caused by trajectory control quality. With favorable applications in the field, the technology has become an important method to guarantee SAGD development effects.
Fattahpour, Vahidoddin (RGL Reservoir Management) | Mahmoudi, Mahdi (RGL Reservoir Management) | Roostaei, Morteza (RGL Reservoir Management) | Nolan, Patrick (Canadian Natural Resources Limited) | Sutton, Colby (RGL Reservoir Management) | Fermaniuk, Brent (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.