Underground Test Facility Research Articles

CUTE: A Cryogenic Underground TEst facility at SNOLAB

Low-temperature cryogenics open the door for a range of interesting technologies based on features like superconductivity and superfluidity, low-temperature phase transitions or the low heat capacity of non-metals in the milli-Kelvin range. Devices based on these technologies are often sensitive to small energy depositions as can be caused by environmental radiation. The Cryogenic Underground TEst facility (CUTE) at SNOLAB is a platform for testing and operating cryogenic devices in an environment with low levels of background. The large experimental chamber (O(10) L) reaches a base temperature of ∼ 12 mK; it can hold a payload of up to ∼ 20 kg and provides a radiogenic background event rate as low as a few events/kg/keV/day in the energy range below about 100 keV, as well as a negligible muon rate (O1)/month). CUTE was designed and built in the context of the Super Cryogenic Dark Matter Search experiment (SuperCDMS) that uses cryogenic detectors to search for interactions of dark matter particles with ordinary matter. The facility has been used to test SuperCDMS detectors since its commissioning in 2019. In 2021, it was handed over to SNOLAB to become a SNOLAB user facility after the completion of the testing of detectors for SuperCDMS. The facility will be available for projects that benefit from these special conditions, based on proposals assessed for their scientific and technological merits. This article describes the main design features and operating parameters of CUTE.

A Simple Normalized Analytical Model for Oil Production of SAGD Process and Its Applications in Athabasca Oil Sands

Summary Since the late 1980s, when the Alberta Oil Sands Technology and Research Authority Underground Test Facility project first demonstrated the feasibility of the steam-assisted gravity drainage (SAGD) technology, many commercial SAGD projects were brought online in Western Canada. Now, many of these projects have late-life SAGD wells approaching their ultimate SAGD recovery factors. Although these projects have demonstrated highly variable production performance, there is an opportunity to use the industry production data to find what they have in common and develop a normalized SAGD model. For this paper, we collected oil production history from several leading SAGD projects with late-life production in the Athabasca oil sands area and confirmed the three stages in an SAGD project lifespan: chamber rising, chamber spreading, and chamber falling stages. By normalizing the field data, all SAGD projects converged to one type curve, regardless of reservoir quality and operating conditions. Based on this observation, a new simple normalized model is derived to model the bitumen production in a typical SAGD process for Athabasca oil sands. The new model bridges the gap between the existing SAGD analytical model and conventional decline analysis and provides oil production forecasts based on the inputs for the five-component recovery factor method defined in the Canadian Oil and Gas Evaluation Handbook(Society of Petroleum Evaluation Engineers 2018). The model has been applied to one of the thermal projects to history match the field production. By running a Monte Carlo simulation, this model further demonstrates its capability to capture the uncertainty of the production forecast for the project at different stages of SAGD operation. In addition, by properly modifying the type curve of the analytical model, a similar workflow can be used to model cases with special reservoir quality or different operational limitations.

Predicting Geomechanical Dynamics of Steam-Assisted Gravity-Drainage Process. Part II: Modified Cam-Clay Model

SummaryIn Part I of this study (Irani 2018), the geomechanical effects in the reservoir associated with steam-assisted gravity drainage (SAGD) steam chamber growth was evaluated on the basis of two core assumptions: reservoir yield behavior follows that of the Mohr-Coulomb (MC) dilative behavior, and the reservoir stress response follows that of a drained sand. In Part I, it was shown that although the dilative model nicely described the shearing and the sheared zone thickness at the front of the SAGD steam chamber, it could not predict the displacements associated with cold dilation in SAGD reservoirs, in which cold dilation refers to vertical displacement created in the zone ahead of the heated zone caused by isotropic unloading generated by the pore pressure increase and the increase in far-field horizontal stress. In cold dilation, the stresses do not reach the critical state line (CSL), which defines the yield surface and should, therefore, be analyzed considering elastic behavior. A modified Cam-Clay (MCC) model, however, can be used to describe the behavior of the oil sand in the cold dilation zone before reaching the CSL. In this study and as an extension to the results presented in Part I, strains developed in the reservoir during SAGD operation are calculated using an MCC model, and the associated oil rate enhancement and displacements are evaluated. The vertical strains and displacements are compared with measured values from the extensive monitoring program conducted at the Underground Test Facility (UTF) in the late 1980s. Two aspects of geomechanical effects are compared between the cap models (Part II) and dilative models (Part I): first, prediction of the sheared zone thickness and its effect on SAGD production enhancement, and second, prediction of vertical and horizontal displacements. It is shown that consideration of the material model effects on production rates are negligible for both models and that the MCC model can predict displacements in both the heated and cold zones of the reservoir reasonably accurately. Although dilative constitutive models can be used to predict horizontal and vertical displacements in the heated zone quite accurately, they lack the ability to predict the response in the “cold dilation zone.” Another main advantage of using an MCC model is that the MCC model provides a better description of a stress path and how the reservoir mobility can affect reservoir dilation, especially in the cold dilation zone.

An Improved Mathematical Model for Accurate Prediction of the Heavy Oil Production Rate during the SAGD Process

Steam-assisted gravity drainage (SAGD) is one of the most successful thermal enhanced oil recovery (EOR) methods for cold viscose oils. Several analytical and semi-analytical models have been theorized, yet the process needs more studies to be conducted to improve quick production rate predictions. Following the exponential geometry theory developed for finding the oil production rate, an upgraded predictive model is presented in this study. Unlike the exponential model, the current model divides the steam-oil interface into several segments, and then the heat and mass balances are applied to each of the segments. By manipulating the basic equations, the required formulas for estimating the oil drainage rate, location of interface, heat penetration depth of steam ahead of the interface, and the steam required for the operation are obtained theoretically. The output of the proposed theory, afterwards, is validated with experimental data, and then finalized with data from the real SAGD process in phase B of the underground test facility (UTF) project. According to the results, the model with a suitable heat penetration depth correlation can produce fairly accurate outputs, so the idea of using this model in field operations is convincing.

CUTE - A Cryogenic Underground Test Facility at SNOLAB

The excellent energy resolution and low threshold of cryogenic detectors have brought them to the forefront of the search for low-mass Weakly Interacting Massive Particles. The next generation of large cryogenic detectors for dark matter search promises further improvements in sensitivity, yet it is difficult and in some cases impossible to test and fully characterize these detectors in an unshielded environment. Therefore, the Queen’s SuperCDMS team is installing a well shielded Cryogenic Underground detector TEst facility (CUTE) at SNOLAB to support detector testing and characterization for SuperCDMS and future cryogenic rare event search experiments. Significant effort is put into achieving a very low background environment which may open the door for early science results with the first set of SuperCDMS detectors during the time the main experimental apparatus is being installed. We discuss some of the challenges and solutions implemented in the design of this facility as well as the status and schedule for the start of operations underground at SNOLAB.

New SAGD model for oil production using a concave parabola steam chamber geometry

In this paper, a new steam chamber growth model using a concave parabola interface is presented. Steam chamber shape is crucial in describing the expansion of injected steam and the propagation pattern of the temperature of the steam front towards the producing well. Steam chamber evolution is particularly important for predicting oil production during steam assisted gravity drainage (SAGD) processes.The new model is derived based on the orientation of the temperature isoline obtained for the underground test facility (UTF) project, the results of several experiments, and the numerical simulation of SAGD processes for major field projects. The analytical description of this steam chamber growth pattern will assist in evaluating and developing fields using SAGD scheme. The model employs the concept of heat conduction involving a moving solid to estimate the steam chamber interface temperature profile and, eventually, the oil production rate and associated steam injection rate required based on an energy balance approach. This study builds upon the assumptions of Butler and Reis’ linear interface by introducing a parabolic steam interface. It is demonstrated that the new model predicts oil production and steam injection rates with higher accuracy than existing models. It also showed the strong variation of oil rate with time unlike the constant rate assumption. The results of the model are compared with the experimental data from Cheng and Butler, simulation with a CMG STARS simulator and the results of the UTF phase B project, which show better agreement and robustness.

CUTE: A Low Background Facility for Testing Cryogenic Dark Matter Detectors

The Cryogenic Underground Test (CUTE) facility will be located 2 km underground in the SNOLAB laboratory, near Sudbury (Ontario, Canada). It is primarily designed to test the performances of cryogenic detectors of the Super-Cryogenic Dark Matter Search (SuperCDMS) experiment which will be installed next to CUTE. As a facility, it will also be accessible to scientists developing innovative cryogenic detectors for rare events search like dark matter or double-beta decay. The low temperature required to operate the cryogenic detectors is reached via an advanced dry dilution refrigerator from CryoConcept (France). The ‘Ultra Quiet Technique’ (UQT®) reduces the vibration transmission by using a proprietary gas-coupled thermal link between the two-stage pulse tube and the cryostat. In order to install the cryostat into a shielding water tank, we have developed a suspension system which decouples the cryostat from the environment with a low stiffness support, making a mechanical low-pass filter with a roll-off below 2 Hz for the vertical attenuation. We report the design choices made for the mechanical architecture to limit the vibration transmission and the material selection to achieve a low radioactive background rate in the detector. The expected background rate is less than 5 counts/day per kg of Ge detector in the 0–1 keV energy range.

Predicting Geomechanical Dynamics of the Steam-Assisted-Gravity-Drainage Process. Part I: Mohr-Coulomb (MC) Dilative Model

Summary In the steam-assisted-gravity-drainage (SAGD) recovery process, the injection of high-pressure/high-temperature steam causes significant stress changes at the edge of the heated zone or steam chamber. These stress changes include shear dilation, which can both enhance the absolute permeability and result in horizontal and vertical formation displacements. The importance of considering geomechanical effects in thermal-recovery processes has been extensively discussed in the literature, but the prediction and surveillance of the resulting effects, such as the impact on production enhancement and reservoir displacement, have in many cases been neglected. Furthermore, issues related to these geomechanical effects on thermal production have been the subject of considerable debate in the industry with no conclusive, meaningful assessments of the effect on reservoir deliverability and production, or of the associated risks that such geomechanical effects have on wellbore and caprock integrity. This study will focus on identification of the main findings from an extensive monitoring program conducted on the original SAGD pilot project conducted at the Underground Test Facility (UTF) in the late 1980s and a seismic program conducted during the last several years by an SAGD operator at a commercial thermal-recovery project. The measured displacements and identified dilation shear zones in these applications were compared with a Mohr-Coulomb (MC) dilative model. This paper illustrates some of the pros and cons of using such analytical models through comparison of the results based on field evidence of the dilation and shearing effects, and how these mechanisms affect both reservoir productivity (revenue) and wellbore and caprock integrity. Although the discussion on the geomechanical effects in thermal-recovery processes will no doubt continue, this study will provide field-supported results to illustrate both beneficial and potentially challenging impacts that these geomechanical effects can have in a thermal-recovery project.

In–Situ Dilation Affects Solvent–Assisted Steam–Assisted–Gravity–Drainage Performance: The Case of a Shallow Athabasca–Type Oil–Sands Reservoir

Summary It is generally accepted that solvent/steam injection in heavy-oil/bitumen reservoirs outperforms steam-only injection in terms of oil-recovery rate, ultimate oil recovery, and steam/oil ratio (SOR). Important parameters in the design of solvent-assisted steam-assisted-gravity-drainage (SA-SAGD) are solvent selection, injection strategy, and solvent retention in situ. The role of geomechanics in optimal application of SA-SAGD, however, remains largely unexplored. Recent studies suggest that solvent transport, solvent-dilution effect, and the temperature distribution around the edge of the steam chamber have major control over SA-SAGD performance. In SA-SAGD, elevated temperature and solvent concentrations within a few meters of the steam-chamber edge reduce the virgin-oil viscosity, causing oil drainage. However, this is the same region where geomechanically induced volume changes alter porosity, permeability, and relative permeability profiles. These alterations could improve the convective-heat transfer and solvent dispersion into the cold bitumen zone, and could also enhance the drainage rate. Consequently, the solvent/oil-phase behavior, steam-chamber growth, and solvent retention and distribution will be affected. This chain of events could have an effect on optimal solvent selection and solvent/steam-injection scenarios. These geomechanical considerations are of particular interest for bitumen deposits, both oil sands and carbonates, where chemical, thermal, and fluid pressures can impose significant volume changes within the reservoir, especially in shallower, lower-confining-stress settings. The role of geomechanics in SA-SAGD was explored numerically by use of a sequentially coupled modeling approach with STARS (CMG 2015a) and FLAC (Itasca 2016). A 2D shallow-depth homogeneous-oil-sands-reservoir geomodel, with properties similar to the Underground Test Facility (UTF) Phase A project, was constructed (Edmunds et al. 1994). Studies were conducted at two scales: the edge of the steam chamber and the reservoir scale including underburden and overburden. The results of these numerical studies revealed that geomechanics considerations directly affect the optimal solvent-type selection and injection strategy during a high-pressure SA-SAGD process. These studies provide valuable direction for further detailed mechanistic studies (both numerically and experimentally) and provide valuable input to the challenges of optimizing SA-SAGD processes in oil sands.

A New Mathematical Model to Understand the Convective Heat Transfer Mechanism in Steam-Assisted Gravity Drainage Process

Steam-assisted gravity drainage (SAGD) process has been an optimized method to explore heavy oil reservoirs in the world. The oil viscosity reduction and gravity force near the interface of steam–chamber are the main development mechanisms. In classical models, conductive heat transfer plays the only or dominant role in the heat transmission from high-temperature steam to low-temperature oil sands. Although some mathematical studies have paid attention to the convective heat transfer, the role of heat transfer by flowable oil normal to the steam–chamber interface has been given little attention. In SAGD, the viscosity of bitumen can be reduced by several orders of magnitude by the release of latent heat from injected steam. In this study, an analytical model is developed for the heat transfer process induced by flowable oil. Also, in order to accurately simulate the oil viscosity characteristics in steam–chamber, a correlation between oil viscosity and pressure is proposed. Results indicate that the oil mobility plays an important role on the flow normal to interface when the distance is smaller than 6 m. Even under the most extreme circumstances (μw = 0.1127 cp), the flowing of oil normal to steam–chamber interface also cannot be ignored. Comparing to Irani and Ghannadi model, it can be easy to draw the conclusion that the new model consists with the underground test facility (UTF) field data much better. This new analytical model will benefit to understanding the convective heat transfer mechanism in SAGD process.

Application of Analytical Proxy Models in Reservoir Estimation for SAGD Process: UTF-Project Case Study

Summary Steam-assisted gravity drainage (SAGD) has been used successfully for the last 25 years in Canada. SAGD is a thermal recovery process that was invented to extract highly viscous bitumen from deep Canadian oil-sands reservoirs. To date, the original idea of SAGD has not changed greatly since the first pilot test in 1987. However, field operation and reservoir management have been influenced by recent developments in technology. Advanced drilling techniques, automated production control, and real-time data monitoring are gradually transforming the SAGD process into smart fields. As such, improving current history-matching techniques would support fast decision-making requirements significantly in closed-loop reservoir management. This paper recommends analytical solutions for simulations with medium-to-high levels of uncertainty. This shows how an analytical simulator can be improved effectively to mimic the essential features of a SAGD field for fast history matching. Combined with the analytical model recently proposed by the authors, this paper investigates the methodology to apply uncomplicated analytical/mathematical solutions to practical cases. The two underground test-facility (UTF) pilot-test case studies covered in this paper provide a better understanding of the proposed methodology. History matching results show that the current analytical models are suitable to act as proxy models for optimization purposes.

SAGD with a Longer Wellbore

Abstract This paper investigates the feasibility of bitumen production using SAGD technology with a longer wellbore. A longer wellbore can be used to exploit a greater volume of the reservoir with a single wellpair as opposed to multiple wells; thus, decreasing pad and drilling costs. The major concern in using a longer wellbore from a reservoir engineering point of view is the potentially non-uniform steam chamber growth over the whole well length due to pressure drop in the horizontal well. Reservoir simulation was performed using Computer Modelling Group's STARS ™?simulator and the QFlow thermal wellbore simulator to address the issue. The pressure drop inside the wellbore was calculated using QFlow. Reservoir simulations were performed using STARS. A sectioned model was constructed, dividing the whole length of the horizontal wellbore into multiple sections, each with its own pressure restriction to match the pressure drop obtained from QFlow. The results showed that with a sufficiently large wellbore size that resulted in a sufficiently low pressure drop, one longer well performed as well as two shorter wells. When a smaller wellbore size was used, production from a longer well was significantly impeded due to the large pressure drop. Introduction Since the discovery of oil sands, many techniques have been tried - and improved upon - to recover the highly viscous bitumen for energy consumption. One of the methods of bitumen recovery that is becoming increasingly prevalent is a thermal in situ method called Steam-Assisted Gravity Drainage (SAGD). Butler(1) first proposed this method in the late 1970s and it was field tested in AOSTRA's Underground Test Facility (UTF) in the 1980s. The initial phase of UTF testing produced successful field results(2, 3). Following Phase A, Phase B was started, implementing the use of longer horizontal wells(4, 5). Surface-operated SAGD was studied in Phase D(6). Following these successful pilot tests, a number of commercial projects have been developed, including Petro-Canada's MacKay River project. One of the factors that needs to be considered in commercial projects is the optimization of the horizontal well length. Typically, the horizontal sections of the SAGD wells are 500 to 700 m long. This paper will examine the effectiveness of using a longer horizontal wellbore in SAGD. There is tremendous potential for economic savings in implementing longer wellbores in a SAGD project. A longer wellbore has the ability to reach greater lengths within a reservoir with one single wellbore as opposed to multiple wells. When multiple wells are drilled, multiple pads must also be built - one for each group of wells. Thus, to cover a given reservoir, the average pad cost will be lower for longer wellbores. Another significant cost advantage of the longer wellbore is the fact that fewer riser sections (also known as build sections) need to be drilled and completed. The riser section has a significantly higher cost than the horizontal section because it is generally much larger in diameter. By decreasing the number of wells in a pattern with the use of longer wells, the cost of all the riser sections is decreased significantly.

History Match of the UTF Phase A Project with Coupled Reservoir Geomechanical Simulation

Abstract Field operation of the Underground Test Facility (UTF) Phase A SAGD project started in November 1987 and terminated in October 1990. In order to understand the interactions between fluid flow and geomechanical behaviour of the reservoir during the SAGD operation, the coupled reservoir geomechanical simulation methodology was applied to history match the measured performance of the project. Reservoir and geomechanical responses were available from an extensive instrumentation program designed for this project. Reservoir pressure, temperature, horizontal displacement, vertical strain and volumetric strain from the coupled simulation were compared with the data obtained from the field survey. These comparisons show that the coupled reservoir geomechanical simulation methodology has the potential to capture both reservoir and geomechanical responses during SAGD. In addition, the steam chamber propagation modes, both in the field and in the simulation, were also discussed. Introduction The coupled reservoir geomechanical simulation methodology (called "coupled simulation" in this paper) has been developed and tested successfully(1). The UTF Phase A project provided a variety of data measured in the field during the SAGD operation which can be used to history match the SAGD process and verify this methodology. The objective of this paper is to establish the reservoir model and geomechanical model based on the available and assumed reservoir properties. Then, to conduct the coupled reservoir geomechanical simulation and compare the simulation performance with that obtained from the field. Finally, sensitivity analyses were conducted to examine the influence of reservoir parameters on the SAGD simulations. Project and Reservoir Description The UTF Phase A project is located 60 km northwest of Fort McMurray, Alberta, Canada. Field operation started in November 1987 and terminated in October 1990. Rottenfusser et al.(2) performed a detailed reservoir characterization. The bottom Clearwater Formation and the McMurray Oil Sands Formation were informally divided into units of A to H. Units D, E and G consist of the major pay zone. Unit F is located between Units E and G and is dominantly shale, grey to light brown in colour, and thinly bedded. Unit F is continuous across the pilot area. It separated the injectors and producers of well pairs Al and A3. Well pair A2 was deliberately drilled so that both wells were above the Unit F barrier(3). The effect of Unit F on the SAGD production performance will be discussed later. The typical reservoir properties are as follows: average porosity is 35%, horizontal permeability is 1 to 10 darcy, bitumen saturation is about 85% and initial reservoir pressure and temperature are 550 kPa and 8 °C, respectively. Bitumen viscosity at reservoir temperature is 5 ? 106 cP and can be reduced to 7 cP at 220 °C(4). Geotechnical Instrumentation In total, 14 dedicated thermocouples (AT series), 4 inclinometers (AGI series), 3 extensometers (AGE series) and 5 piezometers (AGP series) were installed (Figure 1). AT1 and AT7 were also used as inclinometer wells. Piezometers were installed in wells AT4, AT9, AT12 and AT14, and a traversing thermocouple string was used to measure temperature in wells AGI1, AGI2, AGI3 and AGI4.

Field Test of SAGD as Follow-Up Process to CSS in Liaohe Oil Field of China

Abstract The Du 84 block of the Shu-1 area in the Liaohe Oil Field is located in Panjin City, Liaoning Province, China. The production formation, Guantao, contains extra heavy oil with a depth of 530–640 m. The reservoir is characterized in thick pay, with high permeability and a very active aquifer. The dead oil viscosity is 230,000 mPa.s at 50 °C. Although the Cyclic Steam Stimulation (CSS) process using vertical wells has been applied successfully in producing oil from the reservoir, the anticipated ultimate oil recovery is less than 29% of the original oil in place (OOIP). To enhance oil recovery beyond that of the CSS, physical and numerical modeling studies were carried out. The Steam Assisted Gravity Drainage (SAGD) process using a combination of vertical and horizontal wells was proposed as a follow-up process to CSS. An additional 27% recovery is anticipated with the proposed follow-up process. This would give a total recovery of 56%. A pilot with four horizontal producers was implemented in the field. CSS was used initially in the horizontal wells for establishing the communication with the surrounding vertical wells. The pilot was then converted successfully to SAGD operations with horizontal wells as continuous producers and some of the surrounding vertical wells as continuous injectors. A total of 44,500 m3 of oil has been produced over the 12 months of SAGD operations between June 2005 and June 2006. The field implementation process and pilot performance, as well as the challenges with this project, are presented in this paper. Introduction This paper is the continuation of an earlier work(1) in which a field pilot was proposed for testing Steam Assisted Gravity Drainage (SAGD) as a follow-up process to CSS based on a reservoir model and feasibility studies. Two field pilot projects were constructed in 2003 in the Du 84 block of the Su-1 area in the Liaohe Oil Field. One pilot is producing from the Xinglongtai formation and the other one is producing from the Guantao formation. The pilot in the Guantao formation was converted to SAGD operations in early 2005 and the field results are encouraging. The field performance from this pilot is reported in this paper. The Steam Assisted Gravity Drainage (SAGD) process, which was described by Dr. R.M. Butler in the late 1970's(2), has been applied successfully for the production of bitumen and heavy oil since it was tested in the Underground Test Facility (UTF) in the Athabasca oil sands of Alberta, Canada(3). Several commercial projects have been implemented in the field in Canada since then. The Liaohe Oilfield Company constructed its first SAGD pilot in China in 1996 in the Xinlongtai formation, which contains extra heavy oil at a depth of 750 m from the surface. The pilot consisted of one stacked well pair and was operated for about one and a half years. The suspension of the pilot test was due to:insufficient lift capacity provided by the gas lift system; and,difficulties in communication resulting from too large a vertical separation between the injector and the producer.

Understanding SAGD Producer Wellbore/Reservoir Damage Using Numerical Simulation

Abstract This paper reports on the results of a numerical simulation study of a SAGD well pair at Husky's Pikes Peak thermal project in the Lloydminster area. The pressure difference between the injector and producer wells gradually increased over a period of a year followed by a sudden and significant decline in the fluid production rate. Initial numerical simulation identified the problem as being due to damage near the production well, because only this damage pattern matched observations of field production and pressure. A detailed history match of the field data was then conducted. By adjusting the value of skin factor, excellent matches on the production rate and injection and production pressure were obtained. It was shown that by the time the skin factor had increased by a factor of 8 as a result of damage, and the pressure difference was about 900 kPa, the production rate started to drop significantly. Thereafter, the skin factor increased rapidly, and reached 30 times its original value. An acid treatment was performed on the production well. After the treatment, the skin factor returned to its original value, and the well pair returned to normal production. This case study is an example of how numerical simulation can be used as a tool to diagnose, identify and analyze SAGD operational problems. Introduction SAGD has become the leading technology for in situ recovery of heavy oil and bitumen in northern Alberta, Canada. The development of the technology has gone through several stages. The concept was first proposed by Butler(1) in the late 1970's. It was then tested at AOSTRA's Underground Test Facility (UTF) starting in the late 1980's. Phase A of the UTF test proved the concept in the field(2, 3). A number of issues were considered during the test: start up, sand control, steam trap control, reservoir heterogeneities, effect of solution gas and numerical simulation. The Phase A results were successfully scaled-up to longer wells in Phase B(4, 5). Horizontal drilling from the surface and operation of SAGD from the surface was the purpose of the Phase D study(6). This report summarizes the results of a SAGD field case study. At Husky's Pikes Peak thermal project, located in the Lloydminster area, one SAGD well pair experienced a sudden decline in fluid production. A high pressure drop between the injector and producer wells identified the problem as being due to damage near the production well. Simulation revealed the pattern and extent of the damage. After an acid treatment of the production well, production returned to normal. Brief Description of the Field Project The Pikes Peak thermal project started in 1981 using cyclic steam stimulation (CSS) technology. The project was located in the Lloydminster area on the Saskatchewan side, as shown in Figure 1. Later on, SAGD technology was also used. The details of the project history and the area geology can be found in earlier publications(7, 8). In the subject area, the depth from the surface to the top of the pay zone was around 500 m.

The False Lucre of Low-Pressure SAGD

Abstract The recent trend in SAGD is towards low-pressure steam injection. The intention is to be more thermally efficient: steam at lower pressures has a greater proportion of its heat as latent heat, which is the dominant source of heat released to the cold reservoir. The oil sand then warms up to the steam temperature, thus mobilizing the bitumen. The SAGD process must be thermally efficient for optimal economic viability. However, a more rigorous examination of the SAGD process presented here, inclusive of surface processes, reveals that there are fewer thermal benefits in operating at lower pressures. In addition, SAGD will be hindered by low-pressure injection due to higher viscosities and the inhibited dilation of the unconsolidated sandstone reservoir. This paper demonstrates that a complete analysis of the SAGD process favours operation at high pressures, and that SAGD at low pressures will be less effective. Introduction Steam assisted gravity drainage (SAGD) has been successfully applied to the in-situ thermal recovery of bitumen beginning with AOSTRA's Underground Test Facility laboratory-scale pilot project, Phase A (1987 – 1991)(1), and the subsequent commercialscale pilot, Phase B (1991 – present)(2). Since then, a large number of commercial SAGD projects have emulated their success. The current trend in operating philosophy is towards low-pressure SAGD: LPSAGD. This is based on the fact that at lower pressures, a larger percentage of steam's total heat is latent heat. Attractiveness of Low-Pressure SAGD SAGD Process In SAGD, most of the heat transferred to the cold oil sands formation is by the condensation of steam into the periphery of the steam chamber. The latent heat released from the steam is transferred to the colder formation mainly by conduction. Therefore, along the slopes of the steam chamber, the predominant flow of condensed steam (i.e. hot water) and mobilized hot bitumen is perpendicular to the direction of conductive heat flow. Steam quality is the mass fraction of water converted from liquid to steam. In SAGD, the injection of less than 100% quality steam is counterproductive, since the injected liquid water fraction just falls from the injector well to the producer well under gravitational forces within the isobaric steam chamber. This adds to the water recycling costs while contributing neither to the release of energy to the formation nor to bitumen recovery. Steam Properties The energy in steam at constant pressure consists of sensible heat and latent heat. The sensible heat is the energy required to raise the temperature of the water from an initial source temperature to the steam temperature; the latent heat is the energy required for the phase change from that hot water to steam. It is this latent heat that provides the dominant source of heat for the SAGD process. While the enthalpy of steam over the pressure range of 1,000 to 3,500 kPa is relatively uniform (see Figures 1 and 2), at lower pressures the proportion of heat as latent heat is higher. Since latent heat is the dominant form of heat transfer to the formation, one can see the attraction of low-pressure injection, solely from a steam energy viewpoint.

Scientific investigation in deep wells for nuclear waste disposal studies at the Meuse/Haute Marne underground research laboratory, Northeastern France

Andra, the French National Radioactive Waste Management Agency, is constructing an underground test facility to study the feasibility of a radioactive waste disposal in the Jurassic-age Callovo-Oxfordian argillites. This paper describes the processes, the methods and results of a scientific characterization program carried out from the surface via deep boreholes with the aim to build a research facility for radioactive waste disposal. In particular this paper shows the evolution of the drilling programs and the borehole set up due to the refinement of the scientific objectives from 1994 to 2004. The pre-investigation phase on the Meuse/Haute-Marne site started in 1994. It consisted in drilling seven scientific boreholes. This phase, completed in 1996, led to the first regional geological cross-section showing the main geometrical characteristics of the host rock. Investigations on the laboratory site prior to the sinking of two shafts started in November 1999. The sinking of the shafts started in September 2000 with the auxiliary shaft completed in October 2004. The experimental gallery, at a depth of 445 m in the main shaft, was in operation by end 2004. During the construction of the laboratory, two major scientific programs were initiated to improve the existing knowledge of the regional hydrogeological characteristics and to accelerate the process of data acquisition on the shales. The aim of the 2003 hydrogeological drilling program was to determine, at regional scale, the properties of groundwater transport and to sample the water in the Oxfordian and Dogger limestones. The 2003–2004 programs consisted in drilling nine deep boreholes, four of which were slanted, to achieve an accurate definition of the structural features.

The Effect of Operating Pressure on the Growth of the Steam Chamber Detected at the Hangingstone SAGD Project

Abstract At the Hangingstone reservoir of the Athabasca oil sands, Japan Canada Oil Sands (JACOS) started initial steam circulation of the SAGD Phase I project in April 1999, and the regular operation in July. The expected performance was achieved in the early period. The operation pressures were gradually raised from 4,800 kPa in mid-November 1999 to 5,300 kPa in mid- December. In early 2000, initial circulation of the Phase II wells, which consist of three SAGD pairs of 750 m wells, were started. Steam produced at the Phase I steam generator was supplied to warm up these wells. Because of this dual use of steam, the injection pressure of the Phase I wells had to be reduced to 4,600 kPa. A significant change in the growth rate of the steam chamber was detected at some of the observation wells. This was reflected as a suspension of vertical growth of the steam chamber. A new generator to supply steam for Phase II wells was completed in July 2000. Accordingly, the steam injection pressures for Phase I wells were increased in August and the vertical growth of the steam chamber was resumed. The measured temperature changes in the observation wells, the results of numerical simulation study, and conceivable mechanism of the growth of steam chamber are presented in the paper. Introduction The Steam Assisted Gravity Drainage (SAGD) process has been widely accepted as an in situ recovery process of bitumen from oil sands reservoirs. There are many pilot and commercial scale projects currently underway in Alberta(1). Japan Canada Oil Sands Ltd. (JACOS) has participated in the Underground Test Facility (UTF) project since 1992 and has endeavored to develop a clear understanding of the process. The original recovery mechanism presented by Butler(2) has been improved by introducing more realistic convective heat flow(3–5) and accumulation of noncondensable gas(6) in the reservoir. The major effort, however, made during the last ten years was a field study using a numerical simulator. Special emphasis was placed on understanding the growth mechanism of the steam chamber by rigorous simulation of temperature changes at observation wells. Most of the temperature changes measured at observation wells and horizontal production wells for many SAGD projects, including Imperial Oil's vertical-horizontal well project(7), UTF Phases A, B, and D, and Hangingstone Phases I and II, have been reproduced by numerical simulation. A part of the above study involving the UTF Phase B and early Hangingstone Phase I projects(8) was presented in 2000. A phenomenon of "generation of an impermeable layer during the AGD process" was developed during the subsequent examination of the previous article(8), which is presented in this paper. Hangingstone SAGD A-Pair The Hangingstone Phase I SAGD project consists of two pairs (A-pair and B-pair) of 500 m horizontal wells. Initial circulation was conducted from April 14 to July 27, 1999, followed by a regular SAGD operation. The early performance was close to our expectation(8) and the steam chamber was detected in many observation wells.

Flue Gas Injection Into a Mature SAGD Steam Chamber at the Dover Project (Formerly UTF)

Abstract The Dover Project (formerly the Underground Test Facility) is the world's first field pilot of the Steam Assisted Gravity Drainage (SAGD) process using dual horizontal well pairs to recover bitumen. There have been four phases of SAGD piloting at the Dover site thus far. The Phase B pilot, which consists of three 500 m long horizontal well pairs spaced 70 m laterally apart, has been in continuous operation since early 1993. Phase B reached the peak production rate of 300 m3/d or 100 m3/d per well pair on average in the middle of 1994. After sustaining the peak rate for about two years, the production has been in decline with a steady increase in steam-oil ratio. Research carried out in the past few years suggested that the addition of a suitable amount of non-condensable gases (NCG) would be an effective method to wind-down the steam chamber. It provides an economic means to continue bitumen production by utilizing the large amount of heat stored in the SAGD chamber. Beginning in April 1998, a small amount of natural gas was added continuously to the steam injection. The concentration of NCG has increased steadily in the past 3.5 years. The resulting performance has been better than initially expected. Based on the success of this NCG-steam wind-down strategy, a four-month flue gas injection test was conducted in 2001 to investigate the possibility of using the more cost-effective flue gas, rather than natural gas as an injectant. This paper summarizes the rationale for selecting the NCG-steam wind-down strategy, the field implementation of the flue gas injection test, and the resulting pilot performance. The successful implementation of this technology will have a profound impact on the overall process economics. Introduction The Dover Project is an in situ bitumen recovery facility on the Oil Sands Lease Number 328 located 70 km northwest of the City of Fort McMurray. It was initiated by Alberta Oil Sands Technology and Research Authority (AOSTRA) in 1984 and was ater joined by industry participants to pilot the SAGD processsing dual horizontal wells. The Dover Project Area is located in eight sections of land at the extreme eastern edge of the lease, as shown in Figure 1. To the immediate east of Dover is Petro-Canada's MacKay River Project, which is expected to produce 30,000 BOPD using the SAGD process in 2003. Several papers(1–3) have been published to describe, in detail, the Dover Project from the beginning until mid-1997. The following is a brief summary. FIGURE 1: Dover project area. Available in Full Paper. The first phase of testing, Phase A, involved the drilling of horizontal wells from a limestone tunnel network located about 20 m below the oil sand formation. These well pairs had a horizontal length of about 60 m and were spaced 25 m apart, as shown in Figure 2. They were operated from 1987 to 1991. Encouraged by the results from Phase A, the Project proceeded to the secondphase of piloting in late 1991.

Heat Transfer Ahead of a SAGD Steam Chamber: A Study of Thermocouple Data From Phase B of the Underground Test Facility (Dover Project)

Abstract Phase B at the Underground Test Facility (Dover Project) is the longest running and most instrumented SAGD pattern in the world and is operated by Devon Canada (formerly Northstar Energy Corporation). Techniques are presented which allow for the interpretation of temperature data from the pilot to better understand the growth of a SAGD steam chamber over time. Calculating the rate and direction of steam chamber movement, the in situ thermal diffusivity and the role of conduction and convection in heat transfer provide a foundation for understanding the interaction between the SAGD recovery process and the reservoir. Introduction Over 12 years have passed since the first field test of the classical SAGD recovery process at the Underground Test Facility (UTF) near Fort McMurray, Alberta, Canada. In recent years the level of activity in thermal heavy oil has increased dramatically in Canada. Butler has identified four commercial SAGD projects currently under construction or where construction is to commence soon, and two additional projects were recently announced, all of which could total over one half million barrels per day of production by 2010(1). One of the most striking characteristics of the SAGD technology is that it has undergone relatively little change since its first field trial. Fundamentally, the commercial projects which are currently under construction look very much like the original 50 m Phase A horizontals, placed on production in 1988. One reason for little change in the SAGD technology is that, so far, it has delivered excellent results. The early piloting of the SAGD process at the UTF has proven that the SAGD process can deliver good rates and reserves from the reservoir at the UTF, which is considered to be inferior to 1/3 of the Athabasca resource(2). In spite of this perception that the UTF reservoir is marginal, the first commercial length wellpairs at Phase B were highly successful, reaching a normalized productivity of 0.2 m3/d per metre of well length(3). In addition to the success of the SAGD process in recovering oil, SAGD also benefits from the fact that the performance of the early pilots was highly predictable. Butler's equation(4), developed without the benefit of any field data, has been shown to accurately predict the performance of SAGD in the field. The high predictability of the process has meant that the results of early pilots, especially the UTF pilot, have been used to history match simulation models, which have been, in turn, used to predict the performance of SAGD in new reservoirs. In fact, the subject of much of the literature on SAGD is the results of simulation modeling(5–7). At times, the results of simulation modelling are used as a basis for scientific conclusion, typically reserved for real field evidence. Relatively little actual field data is available in the public domain, which exacerbates the situation. Typically, when a new reservoir process is developed and tested in the field, a great effort is required in studying the underlying physics of the process in light of the field data, prior to simulating the process.