bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a Thermal Wellbore Simulator With Focus on Improving Heat Loss Calculations for SAGD Steam Injection
Authors: Xiong Wanqiang , Bahonar Mehdi , Chen Zhangxin 
Published: May 2015

Abstract
Typical thermal processes involve sophisticated wellbore configurations, complex fluid flow and heat transfer in tubing, annulus, wellbore completion, and surrounding formation. Despite notable advancements made in wellbore modeling, accurate heat loss modeling is still a challenge using the existing wellbore simulators. This challenge becomes even greater when complex but common wellbore configurations such as multi-parallel or multi-concentric tubings are used in thermal processes such as Steam Assisted Gravity Drainage (SAGD).
To improve heat loss estimation, a standalone fully-implicit thermal wellbore simulator is developed that can handle several different wellbore configurations and completions. This simulator uses a fully implicit method to model heat loss from tubing walls to the surrounding formation. Instead of implementing the common Ramey method (1962) for heat loss calculations that has been shown to be a source of large errors, a series of computational fluid dynamical (CFD) models are run for the buoyancy driven flow for different annulus sizes and lengths and numbers of tubings. Based on these CFD models, correlations are derived that can conveniently be used for the more accurate heat loss estimation from the wellbore to the surrounding formation for SAGD injection wells with single or multiple tubing strings. These correlations are embedded in the developed wellbore simulator and results are compared with other heat loss modeling methods to demonstrate its improvements. A series of validations against commercial simulators and field data are presented in this paper.
Feasibility of Wider Well Spacing With Solvent Aided Process: A Field Test Based Investigation
Authors: Gupta Subodh , Gittins Simon , Benzvi Amos , Dragani Jarrett 
Published: May 2015

Abstract
The objective of the investigation was to establish from a field trial feasibility of employing fewer wells for SAGD projects using solvent co-injection. An implicit issue in in situ recovery process of bitumen or extra-heavy is the requirement of heat which in the case of SAGD translates into the use of expensive steam. Gupta and Gittins (2006) have previously described a solvent co-injection based improvement to SAGD called Solvent Aided Process (SAP) which combines the benefit of using steam with solvents. As Edmunds et al. (2010) describe, over the years, significant work has been done to show the effectiveness of SAP in improving the energy efficiency of SAGD. SAGD is carried out in repeated patterns of side-by-side horizontal well-pairs, injector and producer lying approximately in a vertical plane, with these planes spaced from each other at a distance known as well-spacing. An optimal well spacing balances well capital cost against steam related capital and operating costs.
SAP, as previously postulated (Gupta et al., 2006), allows this spacing to be larger (as much as by 100%, depending on reservoir conditions) requiring fewer well pairs to drain a given reservoir pool. To test the hypothesis Cenovus Energy conducted a field test at its Christina Lake thermal project, starting in 2009. The test location was specifically chosen to be in an isolated region which allowed for a larger lateral development of the vapor chamber without being intersected by any of the neighboring SAGD patterns.
Presented in this paper are the results of this field test showing the expected production enhancement and reduction of steam to oil ratio. Furthermore, the results are interpreted in light of the allowance of a larger well spacing. The field results presented in this work confirm the feasibility of employing wider well spacing with SAP compared with steam-alone process or SAGD. This finding will be of interest to the wider industrial community as it holds the promise to improve the economics of the oil sands and similar projects.
The findings of this investigation add to the knowledge base information related to well-spacing that has a significant impact on the economics of SAGD/SAP based projects.
Use of Flow Control Devices (FCDs) to Enforce Conformance in Steam Assisted Gravity Drainage (SAGD) Completions
Authors: Vachon G. P. , Klaczek W. , Erickson P. J. , Langer D. C. , Booy D. , Baugh A. 
Published: May 2015

Abstract
Flow Control Devices (FCDs) have demonstrated significant potential for improving recovery in Steam Assisted Gravity Drainage (SAGD) production wells. One initial hypothesis was that steam breakthrough was delayed because the FCDs better homogenized injection and production by equalizing flow and compensating for pressure changes along the wellbore. However, in many cases, the field results were far greater than such an approach would have justified. The actual physics for this process are unclear, and not demonstrated in literature. Upon review of field data published by ConocoPhillips, the possibility of a steam blocking effect was proposed (Stalder, 2012), although the physical basis for this effect was not explored. This paper proposes an updated hypothesis to explain this effect, presents preliminary data to support the assumption, and introduces a new apparatus and methodology to characterize FCDs for SAGD applications.
The traditional approach to steam control states that steam flashing at the producer should be avoided, as it will eventually lead to a completion failure. Alternatively, the proposed hypothesis contemplates using steam flashing at the producer to regulate flow in various segments of the completion, thus better enforcing conformance. The physics of this process will primarily be described analytically; however, this effect was also observed qualitatively in a small-scale experiment where water was flashed across an orifice.
In order to design SAGD completions that leverage FCDs (and this effect), it was necessary to accurately characterize different FCDs under these challenging multiphase flow conditions. Since vendors use a variety of approaches when designing their FCDs, a protocol was developed to create a characterization procedure which was independent of the underlying FCD design and architecture, resulting in a direct comparison of the overall performance of each FCD. Part of this protocol required the construction of a new, high temperature multiphase flow loop capable of subjecting FCDs to representative SAGD operating conditions. Through fine control of the relevant test parameters, accurate performance measurements can be obtained for each FCD. This paper will present some information regarding the design and specifications of this new flow loop, as well as impart some of the lessons learned from its commissioning and initial operation.
Evaluation of Diffusion of Light Hydrocarbon Solvents in Bitumen
Authors: Diedro Franck , Bryan Jonathan , Kryuchkov Sergey , Kantzas Apostolos 
Published: May 2015

Abstract
Solvent-based processes are often used as potential recovery agents in bitumen systems, with and without the addition of heat to the solvent. Solvents can sometimes be applied as a liquid phase, during SAGD start-up operations or processes aimed at developing injectivity into the oil. Light hydrocarbon liquids are traditionally tested for this application. Solvent injection may also occur in a vapour state and its objective is to reduce oil viscosity and improve mobility of bitumen under low temperatures &lt;100°C. In general, hydrocarbon solvents such as propane are often used for this application. The objective of this study is to conduct CT-based measurement of static mixing of bitumen and both liquid and vapour phase solvents, and to quantify some of the time-dependent changes that occur during solvent mixing with bitumen.
Diffusion experiments have been conducted with propane and DME (vapour phase) and with propane, DME, pentane and toluene (liquid phase) solvent systems. Solvents are mixed with medium viscosity Peace River bitumen and high viscosity Grosmont bitumen. The Tests are run under constant pressure and temperature, and Computer-Assisted Tomography (CT) is used to monitor mass transfer of solvent into oil as a function of time. The outcome of this study is measurements of mass transfer rates of solvent into oil, and the degree of oil phase swelling during the tests.
During solvent injection processes in the field, the rate of mixing is a key parameter that will help in deciding which solvent is optimal for different processes. This study focuses on the rate of solvent mixing with oil. In vapour phase solvent systems, the analysis of the CT images allows for an understanding of the impact of oil phase swelling on the effective rate of penetration of solvent into oil. Overall, the test data provided in this work demonstrates that DME mixes into oil faster than other solvents, and leads to more swelling in a vapour solvent-bitumen system. The analysis of CT data provides an understanding of concentration-dependent diffusion coefficients and limitations from predicting mass transfer using constant coefficients in liquid and vapour solvent systems.
Optimizing Steam Injection Scheduling Using Analytical Models in a Probabilistic Approach
Authors: Oliveira Felipe Silva , Gomes Diego Miranda , Cavalcante José Reinaldo , Leitão Hélio Chagas 
Published: May 2015

Abstract
In a heavy oil field producing through cyclic steam stimulation, one of the most complex and time spending tasks, for the reservoir team, is scheduling steam injection across the field. Because there are so many wells, optimizing steam quota and soaking time are usually calculated or simulated for a well, defined as representative for the entire field or at least for an area. That method optimizes the steam stimulation for each cycle of the representative well, but not necessarily optimizes the net present value or reserves for the entire field. Optimizing an entire field through numerical simulation can be frustrating as it consumes lots of time and requires expensive computational infrastructure. This paper shows that analytical methods can be used to optimize net present value (NPV) or reserves in a heavy oil field through massive computing in a probabilistic approach in a much shorter time than it would be done with a numerical simulator, above all in an uncertainty assessment. It can help, also, to analyze the economical convenience of buying new steam generators or moving them between fields or areas.
Thermal Conductivity Measurements of Bitumen Bearing Reservoir Rocks
Authors: Arthur James Kofi , Akinbobola Oluwaseyi , Kryuchkov Sergey , Kantzas Apostolos 
Published: May 2015

Abstract
The increasing imperative to reliably forecast thermal recovery in bituminous reservoirs has heightened interest to study thermal properties of rock-fluid systems, notably that of thermal conductivity. Several measurement techniques have been developed. However, these are typically fraught with limitations aiming at an amenable analytical asssessment. As a result, complex calibrations are implemented, which are susceptible to numerous errors. In this paper, an alternative, more accurate and unique method of thermal conductivity measurement is presented. The method combines two different measurement systems that are capable of measuring heat flux axially and radially. Nonetheless, in both experimental systems, heat is transferred across the test sample after a temperature gradient is established between two defined regions of the sample. The apparati are complemented by computational fluid dynamic models that mimic the physical models at the measurement conditions. A combination of the physical measurements and numerical simulations under steady state conditions is used to provide the final thermal conductivity values. A number of fluid and reservoir samples are tested in order to demonstrate the capabilities of the method. These tests provide evidence of the utility of the method in allowing for variability of sample form, as well as temperature and pressure conditions. Furthermore, both physical experiments and computational models permit and sufficiently account for fluid flow while thermal conductivity is being measured. It is shown that this method is distinctively able to yield accurate results irrespective of the sample size and shape limitations, and attendant heat losses.
Geochemical Bitumen Characterization for the Saleski Steam Pilot in the Grosmont Carbonate Reservoir
Authors: Wei Wei , Yang Daniel 
Published: May 2015

Abstract
Since 2012, horizontal wells at the Saleski Pilot are operated with cyclic steam injection and production, recovering bitumen from the naturally fractured Grosmont carbonate reservoir. A recent geochemical characterization study indicates distinctive vertical variation in fluid compositions within the reservoir. The Grosmont is a highly fractured carbonate rock. Targeted production horizons in this reservoir are Grosmont C (20 m pay) and Grosmont D (30 m pay) units, which are separated by a laterally extensive, 1-2 m thick Marl. The Marl is partially oil saturated, interlaminated with green shale, and fractured. It is indistinguishable by core observation whether the Marl layer is a barrier or a baffle for fluid flow. The geochemical bitumen characterization provides indications to address this question.
For the Saleski Pilot project, a number of bitumen samples were extracted from vertical cores to determine the molecular composition of the bitumen in place and to identify biomarkers for production correlation. There is evidence that the oil in Grosmont C and D units originated from the same source rock. However, the observation of biomarker discontinuity between the two units, C and D, indicates the Marl was likely a barrier (no fluid communication) during the biodegradation process. The significant differences in degraded oil compositions above and below the Marl further suggest different conditions lead to independent biodegradation processes in each unit.
Continuous production samples were taken from Saleski Pilot wells (both in Grosmont C and D units) and analyzed to allocate production intervals. The results have shown evidence of mass communication between the two units, which suggests the Marl is being a baffle rather than barrier during thermal operation. This finding suggests that the oil was biodegraded in the formation prior to any fracturing.
Evaluation of Thermal Efficiency of the Pre-Heat Period in the SAGD Process for Different Completion Methods
Authors: Saks Delon , Kyanpour Mohammad , Onamade Ola 
Published: May 2015

Abstract
In the Steam Assisted Gravity Drainage (SAGD) process, the pre-heat is a very important step in the successful development of the steam chamber. The pre-heat period lasts months and is deemed complete when the temperature between the injector and producer is high enough to establish hydraulic communication. A uniform pre-heat along the wellbore is crucial to achieve steam chamber conformance throughout the life of the well pair. The efficiency of the pre-heat can be affected by several factors, with completion type being one of the most important among them. The objective of this study is to evaluate the impact of this factor on thermal efficiency during the pre-heat phase of the SAGD process.
In this study, the completion practices in five major SAGD projects in Alberta, Canada (Suncor's Firebag and Mckay River, Cenovus' Christina Lake and Foster Creek, and ConocoPhillip's Surmont) were evaluated. The critical factor used to determine the efficiency of any completion type in the pre-heat process is the heat loss and heat exchange along the producer and injector wellbores and the completion components. This variation in thermal efficiency results from factors such as concentric versus eccentric dual tubing completion, and tubular size, length and configuration.
The results of the study provide a comparison of different completion practices in the five major SAGD operations in Canada. The simulation modeling of the process, along with field experience and observations, helped to understand the impact of counter-current heat exchange and heat loss in concentric versus eccentric completions. Also, the results were used to quantitatively evaluate the impact that vacuum insulated tubing has on delivering energy to the reservoir and its associated thermal efficiency during the pre-heat process.
This paper is aimed at providing a better understanding of the impact of different completion methods on thermal efficiency during the pre-heat period in the SAGD process. The study also incorporated actual field performance of the 5 major SAGD projects available in the public domain and AER reports.
Oil Recovery From Gas Over Bitumen (GOB) Reservoirs - Results From the AIDROH Pilot Project in Alberta
Authors: Hogue Bill , Gutiérrez Dubert , Hong Claire , Steiner Jennifer , Freeman Larry 
Published: May 2015

Abstract
Producing from bitumen reservoirs overlain by gas caps can be a challenging task. The gas cap acts as a thief zone to the injected steam used during oil recovery operations and hinders the effectiveness of processes such as steam assisted gravity drainage (SAGD). Moreover, gas production from the gas cap can accentuate the problem even more by further depressurization of the gas zone.
Following a September 2003 ruling by the Alberta Energy Regulator (AER), the Oil & Gas Industry in the province of Alberta, Canada, had about 130 million standard cubic feet per day of sweet gas shut- in to maintain pressure in gas zones in communication with bitumen reservoirs. This decision led to the development of EnCAID (Cenovus’ Air Injection and Displacement process), a process where air is injected into a gas over bitumen (GOB) zone and combustion gases are used to displace the remaining formation gas while maintaining the required formation pressure.
An EnCAID pilot was started in June 2006 and preliminary results were reported in 2008. After eight years of operations, the EnCAID project not only has proven to be effective at recovering natural gas and maintaining reservoir pressure; it has also shown it can heat up the bitumen zone and make the oil more mobile and amenable for production. This led to the development of the Air Injection and Displacement for Recovery with Oil Horizontal (AIDROH) process.
The AIDROH process is the second of two distinct stages. First, an air injection well is drilled and perforated in the gas cap. The well is ignited and air injection is performed to sustain in-situ combustion in the gas zone. This phase is characterized by a radially expanding combustion front, accompanied by conduction heating into the bitumen below. The second stage begins when horizontal wells are drilled in the bitumen zone. The pressure sink caused by drawing down the wells alters the dynamics of the process and creates a pressure drive for the combustion front to push towards the producers in a top- down fashion, taking advantage of the combustion front displacement as well as gravity drainage.
In light of the temperature increases observed in the bitumen overlain by the EnCAID project, a horizontal production well was drilled in late 2011 and commenced producing in early 2012. This paper provides an update of the EnCAID pilot results and presents a summary of the technical aspects of the AIDROH project, pilot results, and interpretation of the data gathered to date such as observation well temperatures, pre and post burn cores and temperatures along the horizontal producer.
Results indicate that the AIDROH process has the potential to maximize oil production from GOB reservoirs and efforts continue to be made to optimize its design and operation.
Simultaneous History Matching for Multiple Different Oil Sands Reservoir Models: Case Study of Hangingstone Demo Area
Authors: Kato Kodai , Doan Luong T. 
Published: May 2015

Abstract
SAGD process is highly affected by geological conditions such as reservoir heterogeneities caused by the existence of shale layers and/or Clast Breccia, impairment zones and so on. To evaluate SAGD performance with satisfactory precision, detailed geological models which reflect complex sedimentary heterogeneities should be constructed based on data such as well control points, 3D seismic data and Training Image. On the other hand, the relationships between complexity and simulation time conflict with each other. Although detailed geological models are needed, simulation time takes longer.
At Hangingstone Demo area, (Demo area), there are 24 well pairs which have been producing bitumen by SAGD process. The objective of this study is to obtain a unique set of parameters, such as permeabilities and extent of heterogeneities, from simultaneous history matching using different geological models (well pairs) from the Demo area. These parameters will be used for forecasting the performance of the nearby analogue Hangingstone Expansion area (HE area) development. At least a couple of well pairs coming from different well pads were chosen as representative models which indicate each typical type of reservoir. These are called Clean Sand rich type, Clast rich, and Sandy-IHS (Inclined Heterolithic Stratification) rich.
If different single models are applied to history matching, at least the same number of history matching studies are needed separately. Obtaining an optimum parameter combination will require a significant number of simulation runs. Furthermore, applying complex geological models for simulation requires significant time to finish running. Figure 1 shows the comparison between individual optimization and simultaneous optimization, which is our new workflow. By use of this, not only multiple different models but also different realizations for the same well pair are matched simultaneously by a single optimization without any time loss.
Our new workflow is composed of mainly 3 sections. The first one is vertical upscaling and coupling between the modeling package and reservoir simulator. The second one is the simultaneous history matching using multiple different models. The third one is the interpretation of the vertical observation well temperature data and history matching utilizing such data. This new technique along with field observation data will be discussed.