Design of Hybrid Steam-In Situ Combustion Bitumen Recovery Processes

Given enormous capital costs, operating expenses, flue gas emissions, water treatment and handling costs of thermal in situ bitumen recovery processes, improving the overall efficiency by lowering energy requirements, environmental impact, and costs of these production techniques is a priority. Steam-assisted gravity drainage (SAGD) is the most widely used in situ recovery technique in Athabasca reservoirs. Steam generation is done on surface and consequently, because of heat losses, the energy efficiency of SAGD can never be ideal with respect to the energy delivered to the sandface. An alternative to surface steam generation is in situ combustion (ISC) where heat is generated within the formation through injection of oxygen at a sufficiently high pressure to initiate combustion of bitumen. In this manner, the heat from the combustion reactions can be used directly to mobilize the bitumen. As an alternative, the heat can be used to generate steam within the formation which then is the agent to move heat in the reservoir. In this research, alternative hybrid techniques with simultaneous and sequential steam-oxygen injection processes are examined to maximize the thermal efficiency of the recovery process. These hybrid processes have the advantage that during ISC, steam is generated within the reservoir from injected and formation water and as a product of oxidation. This implies that ex situ steam generation requirements are reduced and if there is in situ storage of combustion gases, that overall gas emissions are reduced. In this research, detailed reservoir simulations are done to examine the dynamics of hybrid processes to enable design of these processes. The results reveal that hybrid processes can lower emitted carbon dioxide-to-oil ratio by about 46%, decrease the consumed natural gas-to-oil ratio by about 73%, reduce the cumulative energy-to-oil ratio by between 40% and 70% compared to conventional SAGD, and drop water consumption per unit oil produced. However, oil recovery is between 25% and 40% below that of SAGD. Design of successful hybrid steam–oxygen processes must take into account the balance between injected steam and amount of injected oxygen and combustion gas products that dilute injected and in situ-generated steam in the depletion chamber by lowering its partial pressure, and thus its saturation temperature which in turn impacts production rates and recovery.     

中国沿海集装箱港口体系的形成演化机理

立足当今中国的现实,从现代经济学观点与港口地理学原理相结合的新视角,对沿海集装箱港口体系的形成演化机理进行理论探索,揭示出竞争与合作机制的交互作用是推动沿海集装箱港口体系形成演化的内在动力,并归纳演绎了由低级均衡→非均衡相对集中→非均衡高度集中→高级均衡的沿海集装箱港口体系的一般演化模式。实证分析表明,中国沿海集装箱港口体系正处于由非均衡相对集中向非均衡高度集中阶段演化的过渡时期,其动力机制主要有：转型经济的促进作用、政府行为的调控作用和中心枢纽港的极化作用。     

Assessment of oil and gas geopolitical influence

This paper investigated several stages in the formation of the geopolitical influence of oil and gas, including the basis of its gestation, the means of transformation, and the formation and exercise of power. Based on this theoretical framework, a system for assessing the geopolitical influence of oil and gas was developed. This system is comprised of 13 indicators, each with its own method of measurement. Then 21 representative oil and gas importing, exporting, and transit countries were selected as assessment subjects. A quantitative assessment of the geopolitical influence of oil and gas in the selected countries was carried out using the proposed indicators, and factor analysis was used to obtain the main factors of these indicators and the composite score of each country. The empirical results showed that the 13 indicators could be summarized into five main factors, in the order of contribution rate, specifically comprehensive national strength, energy, transportation, risk, and geopolitics, each with its own variance contribution rate. Results of the assessment indicated that the selected countries could be classified into five categories in terms of oil and gas geopolitical influence: strong, relatively strong, moderate, relatively weak, and weak.     

Uncovering Influences on the Form of Oil and Gas Field Size Distributions

A detailed understanding of the processes that led to empirical oil and gas field size distributions, especially the dynamic character of the discovery process, is needed to improve the quality of forecasts of oil and gas resources. An empirical distribution results from a complex interaction of economic, technical, and social factors with geology in the form of a distribution of deposits. These factors may cause an empirical distribution to mutate nonrandomly through time. Changes in the price of oil, the cost of exploration and development, technology, and access to prospects influence the discovery process. Failure to recognize and account for them in the modeling process can result in serious bias in estimates of the number and volume of future discoveries. In addition, the broad range of some forecasts for a given region may be explained by differences in perspective of those involved in the process. Geologists who understand the basic processes and collect the data may be scientific determinists. Statisticians who model and analyze the data are trained to think in terms of random variables and stochastic processes.     

Tee-SVX: Enhanced Oil Flow Rate in Solvent Vapor Extraction Process

The production rate in classical vapor extraction (VAPEX) is far too low for the process to be considered commercially viable. This is largely because the classical process utilizes forces of buoyancy and mass transfer by diffusion and dispersion to distribute the solvent and gravity to drain the diluted oil to the producer. This article presents a new well pattern Tee-SVX which may enhance the oil-flow rate by two to ten times over that of the classical approach. In the new well pattern, additional horizontal injectors, perpendicular to the injector and the producer in Classical VAPEX, are placed in the topmost region of a reservoir. The oil-rate-enhancement mechanism for this new well pattern involves two features. First, the operation pressure of the top injectors is set slightly higher than the bottom injector pressure. This facilitates a downward driving force to assist gravity drainage of diluted oil to the producer. Second, the supplementary injectors generate an additional diluted oil profile perpendicular to the diluted oil profile of the Classical VAPEX process. Therefore, in the new well pattern, the heavy oil is solvent contacted and diluted in both vertical planes (one plane perpendicular to and the other parallel to the horizontal producer), whereas in Classical VAPEX, the heavy oil is diluted in only one. A series of numerical simulations were conducted to evaluate this process. In order to obtain reliable evaluation results, the numerical dispersion was eliminated through extrapolating the simulation results at different grid sizes to an infinitesimal grid size (Δy → 0). The simulation results suggest that the oil-flow rate can be enhanced two to ten times greater than that with Classical VAPEX, depending on the well spacing of the top injectors. For example, for a well spacing of the top horizontal injectors of 120 m, the oil-flow rate from the original producers will be 5.5 times higher than that of Classical VAPEX. For thinner reservoirs, the Tee-SVX can enhance the oil-production rate higher compared with Classical VAPEX. For reservoirs with a small gas cap, Lateral-SVX with vertical injector is quite effective.     

Study on Phase Behavior of CO2/Hydrocarbons in Shale Reservoirs Considering Sieving Effect and Capillary Pressure

The phase behavior of fluid is essential for predicting ultimate oil recovery and determining optimal production parameters. The pore size in shale porous media is nanopore, which causes different phase behaviors of fluid in unconventional reservoirs. Nanopores in shale media can be regard as semipermeable membrane to filter heavy components (sieving effect) in shale oil, which leads to the different distributions of fluid components and different phase behaviors. In addition, the phase behavior of fluid in nanopores can be significantly altered by large capillary pressure. In this paper, the phase behavior of fluid in shale reservoirs is investigated by a new two-phase flash algorithm considering sieving effect and capillary pressure. Firstly, membrane efficiency and capillary pressure are introduced to establish a thermodynamic equilibrium model that is solved by Rachford–Rice flash calculation and Newton–Raphson method. The capillary pressures in different pore sizes are calculated by the Young–Laplace equation. Then, the influences of sieving effect and capillary pressure on phase behavior are analyzed. The results indicate that capillary pressure can suppress the bubble point pressure of fluid in nanopores. The distributions of fluid components are different in various parts of shale media. In the unfiltered part, density and viscosity of fluid are higher. Finally, it is found that the membrane efficiency can be improved by CO₂ injection. The minimum miscibility pressure for shale oil–CO₂ system is also studied. The developed model provides a better understanding of the phase behavior of fluid in shale oil reservoirs.

     

A Simple Way to Model Nonsynchronous Generation of Oil and Gas from Kerogen

Many kinetic models for oil and gas generation use the same kinetics for generation of both oil and gas. In these models, gas is generated at precisely the same time as oil, despite agreement among geochemists that oil generation in nature largely precedes gas generation. Here we present a method for deriving separate kinetics for oil generation and gas generation from the available kinetics for total hydrocarbon generation. The method is based on published data in which oil kinetics are compiled separately from gas kinetics, but it is generalized to be applicable to any of the main kerogen types (I, IIa, IIb, or III), or to any mixtures of those types. Application of this new nonsynchronous model shows that the traditional synchronous models overpredict gas generation by about a factor of two within the oil window, and conversely severely underpredict late gas generation. The nonsynchronous model may predict gas generation several tens of million years later than does the synchronous model. The errors inherent in the synchronous models can be of significance in exploration decisions.     

Methane hydrate formation comparisons in media with and without a water source supply

Water is a necessary element during gas hydrate formations. Therefore, by analyzing water depletion changes in media, the reaction characteristics of methane hydrate in media can be studied. In this study, two water sources supplying some liquid water which may be consumed by the methane hydrate formation reactions were designed and assembled. Using them, the full formation processes of methane hydrate was studied. Experimental results show the following： If heat released from nucleation reaction of methane hydrate is diffused rapidly, the nucleation ratios will be enhanced discernibly. While the hydrate is formed, a force is generated that sucks fresh water from the source into the vicinity of the hydrate, slowing down the cementation process and causing some hydrate grain dissociation. As a result of cementation differences, the hydrate reaction processes with different water sources present linear or quadratic equation characteristics. After a few repeated dissociation and formation processes of some hydrate grains caused by the fresh water, the gas amounts contained in hydrate will be significantly enhanced.     

藏东地区斜坡土壤冻融侵蚀力学机制及敏感性分析

冻融侵蚀是青藏高原草甸覆盖区的主要侵蚀方式,以气候条件一致的藏东地区斜坡表层土壤侵蚀为对象,基于区域地质条件和土体赋存特征,分析了土壤剥蚀输移的力学过程,探索了缓变的隐性因子和灾变的显性因子对冻融侵蚀的作用机制.结果表明:①地表冻融侵蚀是自基岩风化和土壤演化起始,经历冻融拉裂破坏与沙土输移,到重新裸露基岩的一个循环演化...     

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.     

中国陆上天然气资源的经济效用影响因素研究(英文)

本文研究了中国陆上天然气经济效用的地质及相关影响因素。主要研究结论如下:天然气勘探开发成本主要与气田(藏)的深度及储盖层的岩性参数相关,开采成本主要受自然地理因素以及相应储层物性参数影响,而气田(藏)丰度、有效厚度、孔隙度、渗透率和气藏类型是影响天然气产量的主要因素。基于上述研究结论,建立了针对投资成本、价格因素和气田经济价值的千米井深日产量计算公式和区域判断标准。根据判别标准,本文分析了中国不同区域且具有指标意义的天然气田(藏)的经济效用,并针对中国天然气产业经济发展提出了相应的结论和建议。     

Distinction Between Oil Expulsion History and Gas Expulsion History

The process of organic matter transformation into oil and gas is also a balance process of hydrocarbon transformation. This article probes to distinguish the oil expulsion history from gas expulsion history based on the hydrocarbon generation, hydrocarbon residual, and hydrocarbon expulsion processes of the source rocks. In this method, the first step is to study the hydrocarbon expulsion rate by means of hydrocarbon generation potential method; the second step is to study the oil generation rate by means of the heating–pressuring experiment method; the third step is to study the oil residual rate by means of the mathematical method. The difference between the values of oil generation rate and oil residual rate is defined as the oil expulsion rate, while that between the values of hydrocarbon expulsion rate and the gas expulsion rate is defined as the gas expulsion rate. Then, combined with the geological parameters of source rocks, the oil and gas expulsion history can be obtained. This study on Es₁ Source rocks, Nanpu Sag, Bohai Bay Basin, China shows that the primary expulsion period of Es₁ source rocks is Guantao–Minghuazhen period.     

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.     

A probabilistic method for resource appraisal in a petroleum play and its application

A probabilistic method that is based upon conditional probability theory and the laws of expectation has been developed for estimating the undiscovered oil and gas resources in a petroleum play. It takes into account the favorable geological conditions that influence the accumulation of oil and gas and those factors which influence the distribution and the quantity of undiscovered oil and gas. Information about the number and size of undiscovered resources is provided. A practical application in the Turpan-Hami Basin in northwestern China is described. An erratum to this article is available at .     

Oil and gas resource assessment: The linkage between geological analysis and discovery process model results

Two widely-used techniques to estimate the volume of remaining oil and gas resources are discovery process modeling and geologic assessment. Both were used in a recent national assessment of oil and gas resources of the United States. Parallel estimates were obtained for 27 provinces. Geological-based estimates can typically see into areas not available to discovery process models (that is areas with little or no exploration history) and thus, on average, yield higher estimates. However, a linear relation does exist between the mean estimates obtained from these two methods. In addition, other variables were found in a multiple regression model that explained much of the difference. Thus, it is possible to perform discovery process modeling and adjust the estimates to yield results that might be expected from geological-based assessments.     

An assessment of oil supply and its implications for future prices

This paper examines three issues related to both the U.S. and world oil supply: (1) the nature of the long-term, postpeak production profile for the U.S. and, by inference, other regions (the Hubbert curve is used as a “strawman” model); (2) implications on U.S. energy security of using a modified Hubbert-type conceptual model of prepeak production, testing the adequacy of Latin America to be the primary source of U.S. oil imports; and (3) the cyclic behavior of oil prices. it shows that U.S. production will exhibit a more attenuated decline than that simulated by the Hubbert curve and not decline to zero. it asserts that U.S. production is better predicted by past reserves than past production, but that this argument does not apply to nations that keep a much larger proportion of reserves in the ground. Such nations could considerably expand production without any growth in reserves. The paper concedes that the potential total production for these nations could be examined with a Hubbert curve model linked to reserves, but with great uncertainty. Such an uncertain optimistic forecast predicts that the cumulative production of Latin America could far exceed that of the United States. Nevertheless, a statistical model of oil prices since 1870 implies that real wellhead oil prices in the United States are on a long-term upward path, underlying a much more “noisy” cyclical pattern estimated to include 22- and 27-year cycles. The statistical model predicts a severe oil shock within a few years (of 1998) but also predicts that through 2030, real oil prices will not reach 1981 levels again. The paper examines U.S. and world trends in seismic exploration, drilling locations and depths, drilling costs, oil/gas reserves, oil/gas use rates, and oil demand. After taking these factors into consideration, it concludes that the statistical model of oil prices cannot be disputed, despite its lack of basis in economic theory.     

东濮凹陷盐湖盆地油气富集规律研究

国内外油气勘探实践表明,含盐盆地的油气富集和分布与盆地内沉积的盐岩密切相关。东濮凹陷是我国东部地区典型的含盐油气富集盆地,作者通过深入研究其地层层序特征及盐岩纵横向分布特点,进一步剖析了盐岩沉积的主要控制因素及其与生储盖层的关系,搞清了含盐盆地油气的分布和富集与盐岩的关系,指出无论在垂向上还是横向上,东濮凹陷盐岩一般都与暗色烃源岩共生,而且盐岩与同期沉积的砂岩表现为长消关系。研究认为盐岩可作为油气上盖或侧向遮挡,与源岩、储集层可组成良好的生储盖配置关系,利于油气富集区带的形成,对构造和隐蔽油气藏的形成都发挥了积极的作用,并指出与盐岩有关的文东北部和胡状集地区是下一步挖潜的有利勘探方向。研究成果也可为国内外同类含盐盆地的油气勘探提供一定的借鉴经验。     

山前洪积扇坡面细沟侵蚀跌坑特征的试验研究

跌坑的出现是坡面侵蚀过程中的重要现象,标志着细沟侵蚀正在发育,跌坑的贯穿标志着细沟的形成。采用土槽冲刷模型试验,选取流量、坡度、冲刷时间和坡面形态作为影响跌坑发育的因子结合正交试验调查了不同试验条件下跌坑发育特征及影响因素。结果表明：影响跌坑发育的因素主次为冲刷时间、流量、坡面形态、坡度;跌坑沿坡面连续分布,深度具有波动性,沿坡向下呈现先增大后减小的趋势,最大值一般发育在坡面中部;根据跌坑的发育特征将坡面细沟侵蚀划分为片蚀、细沟雏形、细沟发育和细沟调整四个阶段;坡面细沟侵蚀跌坑深宽积与土壤侵蚀量具有较显著线性关系。研究结果对输油管线水毁及水土流失防治具有一定的参考价值。     

塔里木盆地绿洲形成与演变

塔里木盆地的绿洲按形成历史可划分为古绿洲、旧绿洲和新绿洲,它们分别代表绿洲发展演变的三个阶段。本文对绿洲未来演变趋势作了预测,探讨了盆地古绿洲衰亡原因、认为除了风沙、盐碱及河流改道等自然原因外,人类活动引起的地表水资源时空分配发生变化是主要原因。     

Heavy Oil and Oil (Tar) Sands in North America: An Overview & Summary of Contributions

As conventional oil and gas reservoirs become depleted other unconventional energy sources have to be recovered and produced. Four of the major unconventional resources that are strategic for North American interests are heavy oil, oil sands, oil shales, and coal-bed methane. Recent interest and activity in Canada’s vast oil sands are progressing rapidly as soaring oil prices are fueling a ‘gold rush’ in oil sands development in Alberta. This interest is evident by the record-number of oil sands and heavy oil presentations at Energy Minerals Division (EMD)-sponsored sessions at the 2004 and 2005 Annual Conventions of the American Association of Petroleum Geologists (AAPG), held in Dallas, TX and Calgary, AB.