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。     

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.     

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%.     

薄层稠油油藏SAGD物理模拟研究

紧密围绕杜84块兴Ⅰ组油藏的地质特点与开发现状,依据相似原理设计建立了比例物理模型,开展SAGD比例物理模拟实验,探讨了薄层稠油双水平井SAGD开采中蒸汽腔的形成和发育过程,生产特征和开发效果,预测了盖层的热损失,可为开发方案编制提供借鉴。     

Integration of machine learning and data analysis for the SAGD production performance with infill wells

There have been numerous studies on predicting the production performance of the steam assisted gravity drainage (SAGD) process by data-driven models with different machine learning algorithms since their introduction into industry. Similar efforts on SAGD infill wells, nevertheless, remain rare for this advanced alteration in improving the classical SAGD performance. On the other hand, predictive tools to optimize an infill well start time is useful in maximizing bitumen production and minimizing its costs. In this paper, a series of SAGD infill well models are constructed with selected ranges of operational conditions. Three SAGD infill well production performance indicators, namely, an increased ratio ($R_{\text{increase}}$), a total steam–oil ratio (SOR_total), and a stolen ratio ($R_{\text{Stolen}}$) for each SAGD infill well, are calculated based on simulated infill well cases and control models. Five different machine learning algorithms (an artificial neural network [ANN] algorithm, three gradient boosting decision tree [GBDT] algorithms, and a support vector machine [SVM] algorithm) are trained, tested, and evaluated for their effectiveness in predicting those three indicators as output parameters, given seven SAGD relevant parameters as input parameters. Comparisons of different data sets show that the ANN is the best in predicting all three performance indicators under different infill well start times among all the above machine learning algorithms, while the GBDT algorithms have a better ability to learn a variation trend in the SAGD infill well performance.     

基于模糊综合评价的烟道气辅助SAGD过程评价

目前烟道气辅助蒸汽辅助重力泄油（SAGD）技术已在机理研究和数值模拟方面取得了进展,但由于实际投入油田试验的操作成本较高以及存在额外的能量消耗,所以无法直接判断和验证实际应用效果。为了更全面地评估注采方案,本文运用模糊综合评价法建立了多元评价体系,以环境、能量、工艺、经济为4个评价指标,对不同注采方案进行综合评价以选出综合性能最优的生产设计方案,为实际生产方案的选取提供参考,首次对烟道气辅助SAGD实际工程进行评价研究。基于“有无对比法”,将烟道气辅助SAGD与常规SAGD进行对比,结果表明烟道气辅助SAGD的综合效益更好,佐证了烟道气辅助SAGD驱油的优越性。为方便工程应用,开发了“烟气辅助SAGD驱油评价软件”,通过软件进行实例分析并进行方法对比,验证了本文方法的有效性、适用性和准确性。     

采用蒸汽辅助重力泄油技术汽包炉的给水水质研究

为了确定适合采用蒸汽辅助重力泄油技术（SAGD）汽包炉的给水水质要求,利用称重法研究了高温高压条件下给水的硬度的含量对锅炉管内结垢的影响,给水中的油的含量对汽水共腾的影响,以及给水的pH值、O2和CO2含量对锅炉管内腐蚀的影响,并结合现有水质标准进行对比最终确定了给水中铁、铜含量的要求,最终确定了SAGD汽包炉给水水质要求。结果表明：预定SAGD汽包炉的运行压力为10～14 MPa时,给水中溶解氧量、铜含量以及含油量与电站锅炉的指标一致;由于无需纳入汽轮机安全运行的影响,SAGD汽包炉给水中pH值、CO2含量、铁含量以及硬度可以在电站锅炉水质指标的基础上进行适当的放宽。给水中CO2含量无要求,pH值在8.8～10,铁含量≤30 μg/L,硬度≤2 μmol/L,可以满足SAGD汽包炉安全稳定运行的要求。     

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.     

A new analytical model to predict heavy oil production rate in the SAGD process

An analytical model for predicting the oil production rate in the steam-assisted gravity drainage (SAGD) process is presented in this article. The suggested correlation is found based on Butler's original work. It considers the most effective parameters of the process that emphasize the influence of gravity drainage and that are grouped together in the form of the Rayleigh's number. The present model introduces three coefficients (i, j, and k) into the equation, which are determined by minimizing an objective function based on the difference between the six experimental SAGD datasets and the calculated results. The tool chosen for the minimization is the genetic algorithm (GA). After the initial evaluation, the same approach is used for other reservoir characteristics to ensure the robustness of the new equation. Having considered various simulation outcomes with an average error of 8.9% makes this model a credible one for predicting the SAGD production rates. The novelty of the new predictive model lies within its unique approach, making it quite fast and applicable to a wide range of reservoirs with low associated estimation inaccuracies.     

风城油田重18井区超稠油油藏注气方式优化选择研究

水平井热采模式一直是改善特、超稠油油藏开发效果的有效手段。在热采中后期,常规同采同注的注气方式存在着蒸汽热利用率低、蒸汽波及范围小和剩余油量大等问题。研究不同注气方式对该类油藏开发效果和经济效益的影响,研究表明,水平井组一注多采和直平井组合吞吐方式均能很大程度提高蒸汽利用率,有效驱替井间的剩余油。     

Design,construction and operation of lab scale cylindrical steam assisted gravity drainage model for heavy oil recovery

Based on a theoretical background [1,2], a lab scale cylindrical SAGD (steam assisted gravity drainage) model was designed, constructed and operated. There are six different parts in the apparatus: (1) water supplier, (2) steam generator, (3) SAGD cylindrical model, (4) cooling system, (5) constant pressure maintaining system and (6) production system. Temperature, pressure and steam injection rate were controlled by computer, and product (mixture of oil and water) was collected/separated manually. Extra heavy oil (<10 cp at 200 °C) and glass bead (diameter 1.5 mm) were mixed homogeneously for making porosity of 0.3 and applied for simulating oil sand. For obtaining optimum operation conditions of SAGD apparatus, several attempts were made. When the steam at high temperature (160–180 °C), high pressure (8–9 atm) was injected with 20–25 cc/min, cSOR (cumulative steam to oil ratio) of about 5 was obtained with oil recovery of 78.8%.     

稠油蒸汽吞吐后期增产技术现状与前景

目前,国内外许多油藏已处于蒸汽吞吐的后期。此时的油藏油气比低、含水量高、地层压力低、井况差、周期注气量大、操作成本高,产油更加困难。改善蒸汽吞吐后期的采油技术,可以最大限度的提高油藏的采收率。如今,应用于蒸汽吞吐后期增产的方法有:应用助剂改善吞吐效果、间歇注汽技术、"一注多采"技术、多井整体吞吐技术、注采参数优化技术、侧钻水平井技术、蒸汽驱技术、蒸汽辅助重力泄油技术和火烧油层技术等。然而,现在我国还在尝试发展一些新的技术,如水平压裂辅助蒸汽驱和多井组整体优化蒸汽驱等等。这使得蒸汽吞吐后期的增产技术拥有更为广阔的前景。     

Enhanced oil recovery chemical needs

A large fraction of known petroleum resources will not be recoverable by conventional methods. Enhanced oil recovery (EOR) is costly, but a significant amount of production is possible at current world oil prices, and additional production is possible at prices equivalent to synthetic alternates. Many opportunities exist for uses of chemicals in EOR. In particular, polymers and surfactants that are effective and stable at high temperatures and high salinities are needed for surfactant flooding to achieve its potential. Potential markets can be large in the 1990s and beyond. Many factors other than improved chemicals will impact on the future development of EOR. Risks to the chemical industry in new product development would appear to be reasonable, as long as oil producers continue a major effort to develop EOR processes.     

Development of a data‐driven fuzzy screening model for enhanced oil recovery methods using an adaptive weighting system

Screening of enhanced oil recovery (EOR) methods is a main prerequisite for EOR planning and design. In this study, an integrated data‐driven screening model (DDSM) is developed to improve EOR screening using the combined capabilities of the fuzzy expert approach (FEA) and support vector regression (SVR) techniques. In this study, EOR field data from the past 40 years were reviewed to generate an updated and reliable EOR criteria table as a basis to construct a fuzzy screening model. The DDSM was evaluated to determine the quantitative screening and ranking of EOR methods using seven field datasets, including the fast forecasting of the nominated EOR methods. In order to improve screening performance, a fuzzy model was integrated using 4 SVR models to predict the adaptive weights of the screening parameter for decision making. The SVR models can predict the recovery factor (RF) of EOR methods including gas, chemical, steam, and combustion to calculate the adaptive effective weight of the screening parameters. The SVR models were trained with datasets generated from simulations of the EOR process. The absolute average error (AAE) of the SVR models from the simulation varied within the range of 0.078–0.095 for the prediction of the RF. The DDSM results were compatible to the data published in other literature. In addition, the developed model can provide comparable results to common screening software. The results showed improvements due to the adaptive weighting system on the EOR methods’ screening for the studied reservoirs relative to the fuzzy engine with constant weights. The presented integrated model can guide the screening process to select the efficient EOR method in practical applications.     

CO_2驱油提高采收率技术的研究现状与分析

针对化石能源利用过程中排放CO_2引起的温室效应问题,同时为满足油藏高效开发的要求,介绍一种CO_2驱油提高采收率技术,分析其驱油机理,并总结目前国内外EOR技术的应用与开发现状,指出目前我国EOR应用的前景。     

A developed smart technique to predict minimum miscible pressure—eor implications

Miscible gas injection (MGI) processes such as miscible CO₂ flooding have been in use as attractive EOR options, especially in conventional oil reserves. Optimal design of MGI is strongly dependent on parameters such as gas–oil minimum miscibility pressure (MMP), which is normally determined through expensive and time‐consuming laboratory tests. Thus, developing a fast and reliable technique to predict gas–oil MMP is inevitable. To address this issue, a smart model is developed in this paper to forecast gas–oil MMP on the basis of a feed‐forward artificial neural network (FF‐ANN) combined with particle swarm optimisation (PSO). The MMP of a reservoir fluid was considered as a function of reservoir temperature and the compositions of oil and injected gas in the proposed model. Results of this study indicate that reservoir temperature among the input parameters selected for the PSO–ANN has the greatest impact on MMP value. The developed PSO–ANN model was examined using experimental data, and a reasonable match was attained showing a good potential for the proposed predictive tools in estimation of gas–oil MMP. Compared with other available methods, the proposed model is capable of forecasting oil–gas MMP more accurately in wide ranges of thermodynamic and process conditions. All predictive models used other than the PSO–ANN model failed in providing a good estimate of the oil–gas MMP of the hydrocarbon mixtures in Azadegan oilfield, Iran. © 2013 Canadian Society for Chemical Engineering     

Well-pattern investigation and selection by surfactant-polymer flooding performance in heterogeneous reservoir consisting of interbedded low-permeability layer

Surfactant-polymer (SP) flooding has been demonstrated to be one of the most efficient methods of recovering the residual oil in the enhanced oil recovery (EOR) stage. However, the uses of SP flooding in horizontal or vertical well patterns are still being disputed from either technical or economic points of view, particularly in complicated reservoir systems. We investigated the successful application of SP flooding for many well-pattern combinations in a heterogeneous reservoir. A quarter five-spot pattern reservoir model is proposed with three different permeable layers; in particular, the interbedded layer has a much lower permeability than the other layers. The combinations of horizontal injectors and producers possess the most successful EOR processes, especially when the wells are interchangeably located in the high-permeability layers. However, the short-length horizontal-well combination is more preferable than the full-length horizontal-well pattern from the results of a comprehensive evaluation.     

热采井抗高温长效水泥固井技术研究与现场应用

稠油油藏大多采用热力降粘的方式开采,主要是采用蒸汽热采的方法。注蒸汽热采一般为蒸汽吞吐,后期转为蒸汽驱,因此热采稠油井的固井必须适合和满足蒸汽吞吐和蒸汽驱开采方式。后期注蒸汽开采时,由于地层的保温效果很差,高温蒸汽在注入过程中能量通过水泥环很快耗散到地层中,导致稠油油藏达不到注蒸汽热采的效果,严重影响稠油油藏的开发效果。在注蒸汽开采过程中,水泥石在高温蒸汽环境中强度衰减严重,导致水泥环破裂损坏,使原本封固好的环空失效,引发油气水窜,严重缩短油井寿命。针对稠油油藏固井存在的问题,须研究开发一种适用于封固稠油热采井的长效固井技术,使该固井技术具有水泥浆热容高、保温效果好,可延缓蒸汽注入过程中能量损失;水泥浆具有良好的强胶结性能,大大改善固井第二界面胶结强度,有效防止油气水窜的发生,提高浅层水泥封固段长期封固效果;水泥石强度高,抗高温性能好,其强度在高温下衰减缓慢,可经受稠油热采高温蒸汽的侵蚀的优点。有效解决稠油热采井在高温驱替环境下固井质量差、油井寿命短的问题,为稠油油藏勘探开发提供有力的技术支撑。     

Ethyl acetate as a bio-based solvent to reduce energy intensity and CO2 emissions of in situ bitumen recovery

We introduce ethyl acetate (EA), a bio-based chemical, as a potential solvent for bitumen recovery through comprehensive phase behavior and numerical simulation studies. Phase behavior and thermophysical properties of EA/live bitumen are measured at temperatures and pressures up to 190°C and 4 MPa, respectively. Experimental studies suggested that coinjection of EA with steam can reduce the bitumen viscosity by several orders of magnitude. Our numerical simulations show that coinjection of 2–8 mol% EA with steam can significantly reduce the steam-oil-ratio (SOR) by almost 0.9 units while increasing the bitumen production rate. This reduction in SOR can be translated to significant energy saving of ~2.2 GJ, emission reduction of ~120 kg of CO₂, and wastewater reduction of ~120 m³ per ton of the produced bitumen, which are almost 20–25% lower than the steam-assisted gravity drainage (SAGD) process.     

Characterizations of surfactant synthesized from Jatropha oil and its application in enhanced oil recovery

Surfactants are frequently used in chemical enhanced oil recovery (EOR) as it reduces the interfacial tension (IFT) to an ultra‐low value and also alter the wettability of oil‐wet rock, which are important mechanisms for EOR. However, most of the commercial surfactants used in chemical EOR are very expensive. In view of that an attempt has been made to synthesis an anionic surfactant from non‐edible Jatropha oil for its application in EOR. Synthesized surfactant was characterized by FTIR, NMR, dynamic light scattering, thermogravimeter analyser, FESEM, and EDX analysis. Thermal degradability study of the surfactant shows no significant loss till the conventional reservoir temperature. The ability of the surfactant for its use in chemical EOR has been tested by measuring its physicochemical properties, viz., reduction of surface tension, IFT and wettability alteration. The surfactant solution shows a surface tension value of 31.6 mN/m at its critical micelle concentration (CMC). An ultra‐low IFT of 0.0917 mN/m is obtained at CMC of surfactant solution, which is further reduced to 0.00108 mN/m at optimum salinity. The synthesized surfactant alters the oil‐wet quartz surface to water‐wet which favors enhanced recovery of oil. Flooding experiments were conducted with surfactant slugs with different concentrations. Encouraging results with additional recovery more than 25% of original oil in place above the conventional water flooding have been observed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2731–2741, 2017