Combustion Kinetics of Athabasca Bitumen from 1D Combustion Tube Experiments

There are two basic requirements for heavy-oil recovery processes: first, mobilize the bitumen, and second, have a drive mechanism deliver the mobilized bitumen to a production wellbore. In situ combustion has the potential to be an important heavy-oil recovery method. Before design of in situ combustion recovery processes can start, it is necessary as a first step to understand the kinetics of various complex chemical reactions and determine kinetic constants associated with the reactions. Even with modern reservoir simulation capabilities, this is a significant challenge. In this research, an Athabasca bitumen combustion tube experiment, conducted by the ISC Research Group at the University of Calgary, was history matched by using a reservoir thermal simulator to determine a set of kinetic parameters as well as the transport parameters for the system. The main results of the history match was a match of air injection rate, bitumen and gas production volumes, average product gas compositions, temperature profiles along the tube through time, and pressure. Gridding sensitivities were examined to determine if the derived kinetic and transport parameters were dependent on gridblock size. The results revealed that the grid was refined enough to sufficiently capture thermal, mass transfer, and reaction length scales. After this single match was achieved, the same constants were used to successfully predict several other combustion tube experiments. The results suggest that the fuel (coke) for high-temperature oxidation (HTO) originates mainly from low-temperature oxidation (LTO) and not from thermal cracking. This implies that the major control on HTO is upstream oxygen transfer into the LTO region. If LTO does not occur, then a relatively small amount of coke is deposited in the matrix due to thermal cracking and this may be insufficient to start or sustain HTO.     

Applicability of Kinetic Models for In Situ Combustion Processes with Different Oil Types

The in situ combustion (ISC) process is of interest as an enhanced oil recovery method because it is an alternative to traditional steam-based processes for heavy oil and bitumen recovery. ISC is a technique applicable outside the window of reservoir conditions deemed appropriate for steam injection (such as deeper and thinner reservoirs). The process involves complex chemical reactions and physical recovery mechanisms, and predicting the likelihood of successful ISC in field applications remains challenging. This paper describes a numerical investigation of the capability of different ISC kinetic models to predict the combustion behaviors of different types of oils (light oil, heavy oil, and bitumen). Three kinetic models (of Coats, Crookston, and Belgrave) were selected from literature and compared using data from four published combustion-tube experiments. The comparison procedure is as follows: (1) validate the numerical modeling of each kinetic model by matching the selected experimental results or duplicating the numerical results found in published literature; (2) adjust fluid viscosities and densities to match the fluid properties of each experiment;and (3) use each validated kinetic model to predict the performance of the other experiments without further tuning the kinetic parameters. The knowledge derived from the experiments provides guidance for choosing the appropriate kinetic model when no other data are available and for the preliminary design and screening study of a potential ISC project.     

On the Impact of Permeability Heterogeneity on SAGD Steam Chamber Growth

Evolution of steam assisted gravity drainage (SAGD) steam chambers in heavy oil and bitumen reservoirs is tied to uniformity of steam pressure and quality along the length of the perforated interval of the well and reservoir geology and fluid properties adjacent to the well. If the reservoir geology has poor permeability at an interval along the wellpair, then steam delivery to and fluids production from the reservoir is not uniform. If the steam is well distributed throughout the injection well, then the key factor for a uniform steam chamber along the wellpair is reservoir geology. This is especially important in highly heterogeneous, variable thickness reservoirs where geology and reservoir oil composition may vary significantly over the length of a wellpair. Heterogeneity of a growing SAGD steam chamber is related to heterogeneity of the underlying geology. In this study the oil sands models are geostatistically populated to model spatial heterogeneity of permeability. The temperature profile (chamber growth), steam chamber height, conductive, convective, and total heat fluxes have been examined in each case. The results reveal that the length scales of steam chamber growth depend on the permeability heterogeneity. This provides a means to decide length scales for placement of in-well control devices in steam injectors in SAGD.     

Optimization of SAGD Well Elevation

The application of steam-assisted gravity drainage (SAGD) to recover heavy oil sands is becoming increasingly important in the northern Alberta McMurray Formation because of the vast resources/reserves accessible with this mechanism. Selecting the stratigraphic elevations of SAGD well pairs is a vital decision for reservoir evaluation and planning. The inherent uncertainty in the distribution of geological variables significantly influences this decision. Geostatistical simulation is used to capture geological uncertainty, which is used can be transformed into a distribution of the best possible well pair elevations. A simple exhaustive calculation scheme is used to determine the optimum stratigraphic location of a SAGD well pair where the recovery R is maximized. There are three basic steps to the methodology: (1) model the uncertainty in the top continuous bitumen (TCB) and bottom continuous bitumen (BCB) surfaces, (2) calculate the recovery at all possible elevation increments within the TCB and BCB interval, and (3) identify the elevation that maximizes R. This is repeated for multiple TCB/BCB pairs of surfaces to assess uncertainty. The methodology is described and implemented on a subset of data from the Athabasca Oilsands in Fort McMurray, Alberta.     

Stratigraphic Dip Analysis – A Novel Application for Detailed Geological Modeling of Point Bars,and Predicting Bitumen Grade,McMurray Formation,Muskeg River Mine,Northeast Alberta

At the Muskeg River Mine, bitumen is hosted in the clastic sediments of the lower Cretaceous McMurray Formation. Within the mine area, the McMurray Formation is divided informally into mappable units representing fluvial, continental floodplain, open estuarine, estuarine channel complex (ECC), and marine environments. Fluvial, open estuarine, and ECC deposits host more than 90% of the mineable bitumen reserves. Bitumen grade is more consistent within the fluvial and open estuarine units (12–15 mass%), whereas ECC sediments are characterized by significant lateral and vertical grade variability (0–15 mass%). In the ECC deposits, bitumen grade is controlled by significant reservoir heterogeneity. Facies assemblages including point-bar deposits (PB), abandoned channel-fills (AC), and tidal flat deposits (TF), create complex internal geometries, architectures and associated reservoir properties. Traditional facies mapping and correlation has proven to be difficult even in closely spaced wells for the ECC deposits of the McMurray Formation; thus, an alternative technique using concepts of Stratigraphic Dip Analysis (SDA) was developed to assess bitumen grade for the deposits at the Muskeg River Mine. This approach involves three main steps: (l) juxtaposing azimuth maps (rose diagrams) over horizon slice facies maps for selected stratigraphic intervals to identify major channel trends (paleo-current directions); (2) comparison of dips, with corresponding sedimentary structures allows for a better prediction and geometries of point bars and abandoned channel-fills; and (3) comparison of dip trends with dominant lithology of facies assemblages and available bitumen grades provides a base for accurate delineation of architectural elements. A detailed case study is presented and shows that this approach provides a base for accurate delineation of architectural elements and confirms that bitumen grade decreases laterally with inferred maturity of point bar successions.     

Exhumed hydrocarbon traps on the North Atlantic margin: Stratigraphy,palaeontology, provenance and bitumen distribution,an integrated approach

Previous work has demonstrated the presence of a number of exhumed hydrocarbon traps in central East Greenland. Re-evaluation of the stratigraphy alongside detailed investigation of the occurrence of bitumen within the Mols Bjerge and Laplace Bjerg exhumed hydrocarbon traps provides new perspectives on these structures, as well as the petroleum geology of East Greenland and the wider North Atlantic. Sedimentological and stratigraphic studies, augmented with palynological and provenance investigations, have constrained the dating and correlation of the strata exposed in the Mols Bjerge and Laplace Bjerg. Petrographic analysis, alongside analysis of the bitumen identified, has highlighted a much wider distribution of hydrocarbon than previously recognized. It was previously considered that Jurassic strata formed the main reservoir interval within the Mols Bjerge and Laplace Bjerg exhumed hydrocarbon traps. It is shown here that the reservoir intervals in the Laplace Bjerg trap lie within the Late Triassic Ørsted Dal and Vega Sund members, which contain up to 18% pyrobitumen and were previously misidentified as Jurassic. The Jurassic Bristol Elv Formation is the most extensively bitumen stained unit in the Mols Bjerge trap. However, occurrences of pyrobitumen (up to 3%) are recorded throughout the Triassic stratigraphy, including the Early Triassic Wordie Creek Formation. Faults, thick calcrete development and regionally continuous mudstone units play an important role in compartmentalizing the palaeohydrocarbon accumulations.     

Data-Driven Modeling Approach to Predict the Recovery Performance of Low-Salinity Waterfloods

Natural Resources Research - Low-salinity waterflooding (LSWF) has, in the past decade, attained a lot of attention to enhance oil recovery. In LSWF, diluted water is injected into an oil reservoir...     

Prediction of Shale Plugs between Wells in Heavy Oil Sands using Seismic Attributes

A fundamental geologic problem in the Steam-Assisted Gravity Drainage (SAGD) heavy oil developments in the McMurray Formation of Northern Alberta is to determine the location of shales in the reservoirs that may interfere with the steaming or recovery process. Petrophysical analysis shows that a key acoustic indicator of the presence of shale is bulk density. In theory, density can be derived from seismic data using Amplitude Versus Offset (AVO) analysis of conventional or multicomponent seismic data, but this is not widely accepted in practice. However, with billions of dollars slated for SAGD developments in the upcoming years, this technology warrants further investigation. In addition, many attributes can be investigated using modern tools like neural networks; so, the density extracted from seismic using AVO can be compared and combined with more conventional attributes in solving this problem. Density AVO attributes are extracted and correlated with “density synthetics” created from the logs just as the seismic stack correlates to conventional synthetics. However, multiattribute tests show that more than density is required to best predict the volume proportion of shale (Vsh). Vsh estimates are generated by passing seismic attributes derived from conventional PP, and multicomponent PS seismic, AVO and inversion from an arbitrary line following the pilot SAGD wells through a neural network. This estimate shows good correlation to shale proportions estimated from core. The results have encouraged the application of the method to the entire 3D.     

海泡石对水菱镁矿/EVA体系阻燃性能的影响

水菱镁矿是一种新开发的高镁矿,可以作为阻燃填料使用。水菱镁矿作为单一填料时,阻燃效率较低。为了解决这一问题,使用海泡石(SEP)为协效剂,水菱镁矿(HM)作为阻燃剂,制备SEP-HM/EVA复合阻燃材料。对材料进行了极限氧指数(LOI)、垂直燃烧(UL-94)、锥形量热(CCT)和力学性能测试,研究了海泡石对该复合材料阻燃性能及力学性能的影响。研究结果表明:在水菱镁矿和海泡石总添加量为60%,其中海泡石为9%时,相比于未添加海泡石的复合材料,拉伸强度增加了51.59%,断裂伸长率增加了67.54%,LOI上升了3.5%,垂直燃烧等级均维持在V-0级别,热释放总量(THRR)降低了16.65%,烟释放总量(TSP)降低了22.93%。总的来说,在显著提高复合材料力学性能的同时,海泡石也能较好的提高复合材料的阻燃性能。通过该研究能够对水菱镁矿作为阻燃填料方面的应用提供新的思路。     

Architecture,formation and implication of active structure-controlled intraslope channel system southeast offshore Sendai,Tohoku, Japan

Located off the Pacific coast of central Tohoku (NE Japan), the Ishinomaki slope channel (ISC) provides an excellent opportunity to study a structure-controlled intraslope channel and downslope sedimentation along the active margin. The seismic reflection data across ISC show an extensive basal surface and overlying channel complexes between the basement structures of the Abukuma ridge to the south and Kitakami massif to the north, indicating that the formation of the intraslope basin, channelization of ISC and sedimentation of the downstream channel-lobe transition zone (CLTZ) are very likely to be structure-controlled. The oblique channel stacking pattern, faulting of the seafloor and subsurface Abukuma ridge in the upper and lower domains of ISC, collectively suggest that ISC has migrated northward and is currently under the influence of active compression. Differences in styles of accommodation space between the upper and lower domains of ISC suggest that differential subsidence occurred along the strike-slip tectonic line. Based on the regional strike-slip tectonic line, we propose that a Kitakami-Abukuma ridge existed before the formation of ISC. The strike-slip faulting divided the Kitakami-Abukuma ridge into the Kitakami massif to the north and the Abukuma ridge to the south, and an intervening fault trough as the precursor of the intraslope basin and ISC. As the subduction of the Pacific Plate and associated compressional events continued, the Abukuma ridge was reactivated to narrow the intraslope basin into a confined channel. Located near the epicentre of the devastating 2011 Tohoku earthquake event, the ISC, downstream CLTZ and underlying intraslope basin provide information on active basement structure and the evolving sediment routing system on the tectonically active margin.     

Wood burning for residential space heating in the United States: an energy efficiency analysis

Biomass combustion is commonly perceived as an alternative energy source which will reduce reliance on, and thus conserve, conventional non-renewable fuels. However, in the United States wood collection is energy intensive and requires the expenditure of high-quality fossil fuels to support the technology. The efficiency of an energy collection or delivery system can be estimated by using a net energy analysis (NEA). An energy accounting framework is employed to compare the total output of energy (in joules) delivered for residential space heating to the total energy input required to make the wood energy available. Energy inputs are either direct, such as the petrol used to power the transport vehicle, or indirect, such as the energy required to manufacture the transport vehicle. This study analyses the energy efficiency of three wood-gathering strategies commonly practised in the United States. Energy output-input ratios, calculated for each of the three cases, indicate that the ratios are strongly influenced by situation-specific variables, particularly (1) the distance fuelwood must be transport, (2) the load capacity of the transport vehicle and (3) the combustion efficiency of the wood-burning unit. Incorporating indirect energy costs significantly reduces the energy ratio but, in some situations, burning renewable wood can be as energy efficient as conventional heating systems based on non-renewable fossil fuels, thus providing a locally viable alternative.     

Determining Wettability of Fractured Carbonate Reservoirs

Wettability plays a pivotal role in oil recovery processes in reservoirs owing to the fact that it has a direct impact on the proportion of oil recovery. Reservoir rocks are a complex of a variety of mineral types, and each mineral may have a different wettability. Typically most aquifer materials such as quartz, carbonate, and dolomite are water-wet prior to oil migration. Some oil recovery processes are designed to alter the wetting preference of the oil formation to be more oil-wet. There are three techniques used in the laboratory for the characterization of the capillary pressure properties of core samples: mercury injection, centrifuge, and porous plate. This article provides an in-depth review of wettability. It also entails a case study from one of the Iranian carbonate reservoirs and measurements, which have been carried out for selected samples to clarify the nature of the wettability of reservoir rock. Samples were chosen from three wells of oil field which is composed of limestones and dolomites, rarely inter-bedded by shales, and their wettability was measured by Amott–Harvey method, which is one of the main methods for measuring wettability. After cleaning and drying the samples, measurements were carried out. According to the results, it can be said that the range of Amott–Harvey index for these samples is between ?0.48 and ?0.8. In Amott–Harvey method, if IAH varies from ?1 to ?0.3, the rock is oil-wet. Therefore, it can be concluded that the reservoir is oil-wet.     

气候变化背景下人为热估算和效应研究

人为热是指由人类活动产生而释放到大气中的热量,这部分热量以感热和潜热的形式释放到城市冠层和城市边界层中,是城市生态系统的重要能量来源之一。在城市系统中,建筑物、交通运输和人类新陈代谢所释放的热量构成了总的人为热,具有明显的日变化和季节变化特征:清晨和傍晚出现一天中的两大峰值,而冬季和夏季分别是全年中最显著的两个季节。人为热的计算方法通常分为仪器观测法和能源消费清单法,其中能源消费清单法是目前普遍使用的方法。人为热主要通过改变大气的热力学能量方程和水汽方程中的热量和水汽量来影响区域和全球气候。在城市中,人为热是冬季和夜间城市热岛形成的主要原因,会影响大气边界层的稳定度和增加边界层高度。在全球范围内,人为热会对大气环流产生扰动,但对全球增温效应不显著。随着全球能源消费和人口的增加,人为热将成为气候变化的重要人为因子之一,因此如何观测和估算出一套高精度的人为热数据集极为重要。     

Subsurface Sequestration of CO<Subscript>2</Subscript> in the U.S: Is it Money Best Spent?

The continuously decreasing average coal rank (heating value), inadequate investment, and ever stricter air-emission controls have caused the average efficiency of electricity generation from coal in the U.S. to plummet to a mere 32% by the year 2008. The U.S. gas-fired powerplants are 30% more efficient than the coal-fired ones, with average efficiency of 43% in 2008. Replacing each 1,000 MW _e generated by an average coal-fired powerplant with an average gas-fired powerplant would avoid today 7 million tonnes of CO₂ emissions, 1.2 million tonnes of toxic ash, and significant issues with water contamination. The parallel upgrades to the more efficient supercritical steam turbines would decrease current emissions by up to 50% (from the current average plant efficiency of 32% to over 45%). The CO₂ captured in the new combined-cycle powerplants might be used to enhance oil recovery in local fields, where feasible. The CO₂ enhanced oil recovery (EOR) can never become the main sink for the gigantic CO₂ volume generated each year by electric powerplants. Currently, EOR could absorb only 1% of that volume.     

Bitumen Prices and Structural Changes in North American Crude Oil Markets

In an earlier report, changes in bitumen prices at Hardesty, Alberta, Canada, were modeled as the responses to changes in monthly prices of Hardesty light/medium crude oil for the period 2000–2006 with a simple error correction econometric model. This note re-examines that price relationship for the period 2009–2014. Over the period 2006–2014, there was also rapid growth in North American light oil production from low-permeability carbonate, sandstone, and shale reservoirs. During that period, Canadian raw bitumen production grew by more than 12% per year and there was significant geographical diversification in its markets. Results of the statistical analysis showed that the change in the dynamic relationships between bitumen prices and Hardesty light oil prices probably reflected, in part, the maturation of bitumen markets and closer integration with North American light oil markets. The analysis also examines the dynamic relationships between bitumen prices and West Texas Intermediate and Brent international benchmark crude oil prices. Ideally, if bitumen prices are found to be closely related to a widely traded benchmark crude oil, the benchmark crude oil price forecasts could be used as a basis for predicting bitumen prices. However, neither of international benchmark crude oils tested had high explanatory power.     

青藏高原土壤水热分布特征及冻融过程在季节转换中的作用

利用GAME-Tibet期间所取得的高分辩率土壤温度和含水量资料，对青藏高原（主要是藏北高原）土壤水热分布特征及冻融过程在季节转换中的作用进行了分析。指出藏北高原4cm学深处土壤在10月份开始冻结，次年4-5月份开始消融，冻结持续时间长达5-7个月。冻结过程有利于土壤维持其水分，因此，在刚刚开始消融时土壤含水量仍然很高。从而为夏季风爆发前土壤通过蒸发向大气提供水分打下了基础。指出土壤冻融过程可能在高原季节转换中起着重要作用。     

Cost Implications of Uncertainty in CO<Subscript>2</Subscript> Storage Resource Estimates: A Review

Carbon capture from stationary sources and geologic storage of carbon dioxide (CO₂) is an important option to include in strategies to mitigate greenhouse gas emissions. However, the potential costs of commercial-scale CO₂ storage are not well constrained, stemming from the inherent uncertainty in storage resource estimates coupled with a lack of detailed estimates of the infrastructure needed to access those resources. Storage resource estimates are highly dependent on storage efficiency values or storage coefficients, which are calculated based on ranges of uncertain geological and physical reservoir parameters. If dynamic factors (such as variability in storage efficiencies, pressure interference, and acceptable injection rates over time), reservoir pressure limitations, boundaries on migration of CO₂, consideration of closed or semi-closed saline reservoir systems, and other possible constraints on the technically accessible CO₂ storage resource (TASR) are accounted for, it is likely that only a fraction of the TASR could be available without incurring significant additional costs. Although storage resource estimates typically assume that any issues with pressure buildup due to CO₂ injection will be mitigated by reservoir pressure management, estimates of the costs of CO₂ storage generally do not include the costs of active pressure management. Production of saline waters (brines) could be essential to increasing the dynamic storage capacity of most reservoirs, but including the costs of this critical method of reservoir pressure management could increase current estimates of the costs of CO₂ storage by two times, or more. Even without considering the implications for reservoir pressure management, geologic uncertainty can significantly impact CO₂ storage capacities and costs, and contribute to uncertainty in carbon capture and storage (CCS) systems. Given the current state of available information and the scarcity of (data from) long-term commercial-scale CO₂ storage projects, decision makers may experience considerable difficulty in ascertaining the realistic potential, the likely costs, and the most beneficial pattern of deployment of CCS as an option to reduce CO₂ concentrations in the atmosphere.     

东南极中山站附近湖冰与固定冰热力学过程比较

2006年对东南极中山站附近湖冰和固定冰的热力学过程进行了系统观测.基于观测数据比较湖冰和固定冰热力学生消过程;分析湖冰和固定冰温度对气温变化的响应规律;计算不同深度层湖冰和固定冰的垂向热传导通量.结果表明:观测的湖泊和海岸区均在2月底至3月初形成连续冰层;湖冰9月底至10月初达到最大冰厚,早于固定冰1-2个月,湖冰最...     

Numerical modelling of the hydrocarbon generation of Tertiary source rocks intruded by doleritic sills in the Zhanhua depression,Bohai Bay Basin,China

An igneous hydrocarbon reservoir had been found in the Zhanhua depression, Bohai Bay Basin, eastern China. Two doleritic sills successively intruded into the immature source rock of the third member of the Shahejie Formation (Es3). The heat released from the magma changed the mineral composition of wall rocks and accelerated the maturity of organic matter. Thin hornfels and carbargilite zones were found next to the sills. The vitrinite reflectances (%R_o) of these heated wall rocks increased to at least 1.4% near the contacts (<50 m), and accumulation of oil was found in the hornfels zone and dolerite bodies. With the aim of understanding the influence of the sills on the hydrocarbon generation process, a complex heat conduction model was used to simulate the thermal history of the organic‐rich wall rocks, in which both the latent heat of crystallization of intrusions and vapourization heat of pore water in wall rocks were considered. The simulation results suggested that the cooling of each sill continued for about 0.1 Ma after its emplacement and the temperature of wall rocks was considerably raised. The peak temperature (T_peak) that wall rocks experienced can reach 460–650°C in the region of 10 m away from the contacts. The thermal model was qualitatively verified by comparing the experimental data of vitrinite reflectances and mineral geothermometers of the wall rocks with the simulation results. Furthermore, we modelled the hydrocarbon generation of the source rocks based on the simulated thermal history. In the region of about 100 m from the contacts, the organic matter was heated and partially transformed into hydrocarbon within only a few 1000 years, which was significantly faster than the normal burial generation process.