Multiphase flow at the edge of a steam chamber

The use of steam‐assisted gravity drainage (SAGD) to recover bitumen from Athabasca deposits in Alberta has been growing. Butler [Butler, J. Can. Pet. Tech. 1985;24:42–51] derived a simple theory to calculate the production rate of oil during SAGD in an ideal reservoir. This simple and useful theory made several assumptions about the properties of the reservoir and operating conditions of the process. The theory also assumed that the highest mobility oil is at the edge of the steam chamber and that the oil phase velocity is highest at the chamber edge and reduces with distance into the oil sand. This research examines flow conditions at the edge of the steam chamber. Specifically, a new theory is derived that takes into account the impact of oil saturation and relative permeability on the oil mobility profile at the edge of a steam chamber. It is shown that the flow behaviour at the edge of a steam chamber is more complex and is not fully represented by Butler's theory. Contrary to Butler's theory, the oil mobility has its maximum some distance away from the edge of the steam chamber. The results reveal that the higher the thermal diffusivity of the oil sand, the deeper the location where the oil phase velocity is maximum. The developed model has been validated against published experimental and field data.     

Stability of the edge of a SAGD steam chamber in a bitumen reservoir

Steam-Assisted Gravity Drainage (SAGD) is a key in-situ recovery process being used today to extract oil from bitumen reservoirs. In SAGD, an oil-depleted chamber of steam grows within the oil sands formation along a pair of horizontal wells and heats bitumen-laden oil sands at its edge. The viscosity of bitumen drops by up to five orders of magnitude when heated to above 200 °C and mobilized bitumen at the chamber edge flows under gravity to a production well located at the base of the chamber. If the steam chamber does not grow uniformly along the wellpair, then bitumen recovery is less than ideal. To raise the thermal efficiency, and consequently the economics, of the process, efficient heat transfer from chamber to the oil sands must occur and the chamber must grow uniformly along the entire length of the wellpair. If steam fingers develop at the edge of the chamber, then the heat transfer area enlarges and raises the thermal efficiency of the process since more heat is directed to the oil sands. In this research, the stability of the interface between the steam chamber and oil sands is examined by using linear stability theory. The results show that the stability is controlled by the difference between the energy content-weighted Darcy–Rayleigh numbers of the steam/water phases (displacing fluid) and the oil phase (displaced fluid). Also, the results show that at typical SAGD steam saturation temperatures, the chamber edge is unstable providing the steam quality at the edge exceeds about 50%.     

Theoretical studies on the gravity drainage of heavy oil during in-situ steam heating

One concept for the in-situ production of oil from the tar sands involves the continuous injection of steam into a growing steam-saturated volume or steam chamber. Steam flow to the boundary of the chamber, condenses and gives up its heat to the surrounding oil sands. The condensate and heated oil flow by gravity to a production well located at the bottom of a chamber and are removed continuously. The well may consist of a horizontal slotted pipe. This paper describes the theory of operation of such a process and an equation is derived which predicts the rate of drainage.     

水平管内纯饱和蒸汽强制对流冷凝局部换热特性

通过对水平管内饱和纯蒸汽强制对流冷凝换热的实验研究, 分析在管内两相流型为环状流-半环状与波状流时, 质量含汽率、蒸汽入口流速和压力对蒸汽冷凝换热的影响, 并得到了同时适用于这两种流型的计算局部冷凝传热系数的经验关联式。结果表明:局部冷凝传热系数在环状流-半环状流及波状流下均随质量含汽率和压力的降低而减小;在环状流-半环状流下, 随蒸汽入口流速的升高而增大, 在波状流下, 随蒸汽入口流速的增大而减小;实验拟合所得到的换热经验关联式与实验结果符合良好, 偏差在±20%以内。     

特超稠油开发技术分析

特稠油和超稠油油由于极高的粘度导致开发的难度大大增加。本文在系统调研目前国内外特超稠开发技术的基础上,总结了六种最有潜力的技术并分别进行了分析评价,即水平裂缝辅助蒸汽驱技术、蒸汽加溶剂技术、重力辅助火烧油层技术、水平井火烧油层、水平井蒸汽辅助重力泄油、水平井注气体溶剂萃取技术、出砂冷采技术。     

新型无视固砂剂的研制

针对稠油热采井出砂的特点,以硅酸盐、铝酸盐、硅铝酸盐等为原料,合成了适合于高温蒸汽井(350℃)的无机固砂剂。结果表明,这类无机固砂剂具有优异的耐高温性能,固砂强度高,成本低廉。该类固砂剂在蒸汽驱或蒸汽吞吐井中的应用前景十分广阔。     

超稠油开发技术现状与实例

本文对五种有潜力的超稠油开发技术分别进行了分析评价,即水平井蒸汽辅助重力泄油、出砂冷采技术、水平井注气体溶剂萃取技术、重力辅助火烧油层技术、水平裂缝辅助蒸汽驱技术。其中出砂冷采和蒸汽辅助重力泄油技术均已工业化应用并取得了良好的开发效果,如E IK Po int和辽河杜84块超稠油油藏。     

稠油油藏蒸汽辅助重力泄油参数优化研究

在SAGD开采过程中,蒸汽腔的形成与发育直接影响着最终开发效果的好坏,在泄油过程中,蒸汽腔的大小、泄油能力不断在改变,蒸汽—油界面不断在移动,为防止蒸汽突破进入生产井或者热油积聚在蒸汽腔底部压迫蒸汽腔,必须对蒸汽腔的扩展状况以及油层温度场、压力场以及含油饱和度场进行动态模拟。本文应用STARTS数值模拟软件,对注采井间进行局部加密,精细模拟井间温度、压力场,对直井—水平井组合的SAGD技术的布井参数、注采参数等进行了优化设计,并对开发效果进行了预测。验证了运用数值模拟方法研究蒸汽辅助重力泄油技术开发效果的可行性和蒸汽辅助重力泄油技术开发超稠油油藏的可行性。     

Displacement of bitumen from reconstituted oil sands by aqueous solutions

A simple method has been developed for modelling the recovery of bitumen from packed beds of oil sand by water or caustic solution displacement. Batches of reconstituted oil sand were prepared by intimately mixing predetermined amounts of sand, water, and bitumen, thereby permitting the composition of the oil sand to be controlled and varied within a wide range. Dilution of the bitumen with hexadecane facilitated the mixing process and allowed experiments to be performed at low temperatures while maintaining oil-water viscosity ratios comparable to those prevailing at the higher temperatures encountered during hot water or steam displacements in the field. The effects of a wide range of compositional and operational variables were studied using a two-level fractional factorial design technique and the findings are discussed. Of particular interest are the observations that the density and initial connate water saturation of the oil sand exert significantly more effect on bitumen recovery efficiency for the case of water displacement than for caustic solution displacement.     

Design of stable steam injectors for continuous heating

Continuous direct steam injection systems are used in industry to rapidly raise the temperature of process streams either for heating or for sterilization purposes. High heat transfer rates can be achieved using this method, as compared with other methods e.g. shell and tube heat exchangers. Currently, there are no rational procedures available for designing steam injectors for stable operation. Flow visualization studies and pressure measurements have shown that three flow regimes; bubbling, jetting and intermittent steam/water flow exist, in direct steam injection into continuously flowing water. These flow regimes are a function of process conditions and orifice diameter. A semi-quantitative flow regime map for a range of process conditions has been drawn up. Bubbly flows give rise to the highest levels of noise due to bubble oscillations. This type of flow should therefore be avoided. The most stable flow regime, in terms of noise levels generated and hydrodynamic considerations is the jetting regime. Models have been derived for each flow regime; good agreement is found between experimental and theoretical data. A dimensionless number (Bubble/Jet number) has been defined, which can be used to predict transitions between bubbling and jetting flows. This dimensionless number, together with the flow regime map can be used to design stable, relatively quiet steam injection systems.     

蒸汽吞吐井热管采油工艺可行性分析

本文详细的分析了热管采油工艺技术原理,重力热管作为井筒伴热的一种方式是完全可行的,空心抽油杆为工质提供了工作环境;根据重力热管作用原理,并结合蒸汽吞吐的特点,与电加热相比,重力热管无需补充外来能量,因此能够节约大量的能源。在此基础上,分析了增油效果原理,一是井筒中的流动阻力增加的幅度变缓,产量也相对高;另外,延长了流体温度降低到原油滞留温度点的时间,增加周期产量。延长了流体温度降低到原油滞留温度点的时间,相应就延长了油井生产时间,增加周期产量。     

油砂沥青超声波减粘工艺研究

油砂沥青粘度较大,自然状态下不易流动,严重影响了管道输送及加工,针对目前油砂沥青研究中存在的问题,采用超声波进行了减粘的实验研究。实验综合考察了超声波作用时间、温度、超声波频率、超声波功率等因素对减粘效果的影响。实验结果表明,在适当的超声作用时间(20 min)、适宜的温度(30℃)、适宜的超声波频率(20 kHz)和超声波功率(250 W)的条件下,油砂沥青的减粘率可达80%以上。经超声波处理后的油砂沥青粘度略有恢复,但仍远低于处理前的粘度,超声波减粘效果良好。     

Processibility of athabasca oil sand: Interrelationship between oil sand fine solids,process aids,mechanical energy and oil sand age after mining

Processibility curves have shown that strong inorganic bases or anionic surfactants are effective as process aids in the hot water extraction of bitumen from oil sand, but maximum bitumen recovery for each oil sand type is the same for both types of aid. Nonionic surfactants were not useful and there was no general relationship between recovery and surface tension or pH. Bitumen recovery could be correlated with the fine solids component of oil sand. The amount of NaOH required to reach maximum recovery and the rate of aging of oil sand were also functions of the fine solids content. Shear during slurrying was also found to be important, and it was shown that, without a certain amount of mechanical energy, good bitumen recovery could not be achieved, regardless of how much process aid was used. A theory of processibility is proposed to explain the interactions among process aids, mechanical energy, oil sand fines, and age of oil sand after mining.     

春风油田浅层超稠油开发效果评价

对春风油田薄浅层超稠油开发效果进行了评价研究。水平井蒸汽吞吐开发技术利用水平井增大泄油面积,蒸汽在水平井段上部形成蒸汽腔室,实现隔热保温驱油。矿场实践证实水平井蒸汽吞吐辅助氮气、降粘剂开发薄浅层超稠油是可行的。稠油产量周期内、周期间快速递减的规律不可改变,但可以通过技术配套和加强管理减缓递减。通过开发规律研究,为指标预测、开发决策提供了依据。对于较厚油层,可以采用蒸汽吞吐辅助氮气、降粘剂开发。春风油田已建成产能65万吨/年,累产油115万吨。     

Investigation of Oil Sands Froth Treatment

Two oil sand froth treatment methods are investigated: 1) dilution with an aromatic solvent followed by centrifugation (AS Method); 2) dilution with a paraffinic solvent followed by gravity settling (PS Method). The effectiveness of the methods is assessed in terms of bitumen recovery and the water content in the recovered diluted bitumen. The optimum solventto‐bitumen ratios are identified considering process type, ore quality, temperature, and residence time.     

Optimization strategies and impact of low oil price on long term SAGD projects

Steam assisted gravity drainage (SAGD) has been known as a commercially proven high ultimate recovery process for bitumen and heavy crudes. It is an energy intensive process, which is economical when oil price is above certain value. When the oil price goes below the economic threshold of project, steam injection can be decreased or completely stopped for a certain period of time, and can resume thereafter when the condition alters. The objective of this study is to provide comprehensive information about the effect of steam injection interruptions on thermal project performance. An optimization strategy for the SAGD process, in cases where steam injection interruption occurs, is discussed using actual reservoir models of different geological formations. An economical model is used to evaluate operating strategy effect on the net present value (NPV) of the project. The parameters, like shut-in period, initial steam injection period, etc, are optimized for Athabasca type oil sand reservoirs. The results show several key mechanisms exist in the life cycle of the SAGD process that must be included to reflect the field scale behaviour; otherwise, the mechanistic simplicity of the models could lead to directional and semi-quantitative conclusions. Among the mechanisms, temperature effect on basic petrophysical properties of reservoir rocks was found to have an important role in the oil recovery, and considerably impacts the results of optimization. When the steam injection is interrupted, an optimum shut-in period can be determined to maximize the oil recovery. The optimum length of steam injection interruption depends on the initial steam injection period.     

Effect of supercritical water on upgrading reaction of oil sand bitumen

The advantages of supercritical water (SCW) as a reaction medium for upgrading oil sand bitumen were investigated through a comprehensive analysis of the output product, which includes gaseous products, middle distillate, distillation residue, and coke. Canadian oil sand bitumen mined by the steam assisted gravity drainage method was treated in an autoclave at 420-450 °C and 20-30 MPa for up to 120 min with three kinds of reaction media: SCW, high-pressure nitrogen, and supercritical toluene. The yields of gaseous products indicated that a very small amount of water was involved in the upgrading reaction. The analytical results of the middle distillate fractions were almost the same using water and nitrogen at 450 °C. The distillation residues produced in SCW had lower molecular weight distributions, lower H/C atomic ratios, higher aromaticities, and consequently more condensed structures compared to those produced in nitrogen. The coke produced using SCW also had lower H/C values and higher aromaticities. Judging from all the analytical results, the upgrading of bitumen by SCW reaction was primarily considered to be physical in nature. As a result, it is possible to highly disperse the heavy fractions by SCW. This dispersion effect of SCW led to intramolecular dehydrogenation of the heavier component and prevention of recombination reactions, and consequently gave the highest conversion.     

稠油井分层稳恒注汽技术

注蒸汽吸汽不均问题是稠油非均质油藏蒸汽吞吐开发主要矛盾之一,多年来工艺技术人员研究应用选配注技术,通过分隔纵向油层,实施配汽,取得了较好的效。但是不能同时给两个油层注汽,只能先注下层,然后投球配注上层,蒸汽的热损失大,而且存在人为误差和蒸汽的浪费,同时在热采井口投球存在不安全隐患。针对这类问题,研制应用了分层稳恒注汽技术,将分层稳恒注汽管柱下入指定位置。注汽时,蒸汽通过稳恒注汽阀按设计注汽量进入油层,达到调整和改善油层的吸汽剖面,使油井各层位产能达到均衡动用,提高热采效果和采收率。     

油层保护与高温蒸汽热洗清防蜡综合技术

中原油田采油三厂一般应用长期定量加高效表面活性剂、清蜡剂等化学药剂,降低原油粘度,提高原油溶蜡能力的方式,以维持结蜡油井的正常生产;但是对于严重结蜡油井,只能减缓石蜡、沥青等重组分的析出和附着速度,清防蜡效果有限。因此针对严重结蜡油井,开发应用油层保护与高温蒸汽热洗清防蜡综合技术,通过油层保护与高温蒸汽热洗相结合,定期对严重结蜡井进行蒸汽热洗,能清理油管内壁和抽油杆的积蜡,同时相比普通热洗和一般蒸汽热洗,大幅降低对油井生产的负面影响;对于维护严重结蜡井的正常高效生产,具有重要的意义。     

Prediction of bitumen content in oil sand based on FT-IR measurement

FT-IR spectra of bitumen are utilized to propose simple prediction method of bitumen content in oil sand. Analysis and fractionation of Athabasca oil sand were carried out by standard method. A fraction of bitumen dissolved in tetrahydrofuran (THF) was 9.1 wt% and insoluble fraction was found as concomitantly clean clay (sand). The asphaltene fraction of oil sand was 1.42 wt%, which has higher sulfur content and lower H/C molar ratio than that of maltene. The clean clay and bitumen were used to prepare clay/bitumen composites. FT-IR spectra of different clay/bitumen composite were measured and compared. From analysis of the absorbance data, the empirical equation to predict bitumen content in oil sand was acquired using linear least square fitting. Using this equation, bitumen content of Athabasca oil sand was predicted to have a value of 10.5 wt% which is similar to 9.1 wt% of bitumen content extracted by THF solvent from oil sand.