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Middle East Karst Carbonate: An Integrated Workflow For Prediction Of Karst Enhancement Distribution 中东岩溶碳酸盐岩:岩溶强化分布预测的综合工作流程
Pub Date : 2019-09-17 DOI: 10.2118/196619-ms
F. Bigoni, M. Pirrone, G. Trombin, Fabio Vinci, Nicola Raimondi Cominesi, A. Guglielmelli, Al Attwi Maher Ali Hassan, Kubbah Salma Ibrahim Uatouf, M. Bazzana, E. Viviani
The Mishrif Formation is one of the important carbonate reservoirs in middle, southern Iraq and throughout the Middle East. In southern Iraq, the formation provides the reservoir in oilfields such as Rumaila/West Qurna, Tuba and Zubair. The top of the Mishrif Formation is marked by a regional unconformity: a long period of emersion in Turonian (ab. 4.4 My) regionally occurred boosted by a warm humid climate, associated to heavy rainfall. In Zubair Field, within the Upper interval of Mishrif Formation, there are numerous evidences of karst features responsible of important permeability enhancements in low porosity intervals that are critical for production optimization and reservoir management purposes. In the first phase, the integration of Multi-rate Production logging and Well Test analysis was very useful to evaluate the permeability values and to highlight the enhanced permeability (largely higher than expected Matrix permeability) intervals related to karst features; Image log analysis, on the same wells, allowed to find out a relationship between karst features and vug densities, making possible to extend the karst features identification also in wells lacking of well test and Production logging information. This approach has allowed to obtain a Karst/No Karst Supervised dataset for about 60 wells. In the second phase different seismic and geological attributes have been considered in order to investigate possible correlations with karst features. In fact there are some parameters that show somehow a correlation with Karst and/or NoKarst wells: the Spectral Decomposition (specially 10 and 40 Hz volumes), the detection of sink-holes at top Mishrif on the Continuity Cube and its related distance, the sub-seismic Lineaments (obtained from Curvature analysis and subordinately from Continuity), distance from Top Mishrif. In the light of these results, the most meaningful parameters have been used as input data for a Neural Net Process ("Supervised Neural Network") utilizing the Supervised dataset both as a Trained dataset (70%) and as a Verification dataset (30%). A probability 3D Volume of Karst features was finally obtained; the comparison with verification dataset points out an error range around 0.2 that is to say that the rate of success of the probability Volume is about 80%. The final outcomes of the workflow are karst probability maps that are extremely useful to guide new wells location and trajectory. Actually, two proof of concept case histories have demonstrated the reliability of this approach. The newly drilled wells, with optimized paths according to these prediction-maps, have intercepted the desired karst intervals as per the subsequent image log interpretation, which results have been very valuable in the proper perforation strategy including low porous intervals but characterized by high vuggy density (Karst features). Based on these promising results the ongoing drilling campaign has been optimized accordingly.
Mishrif组是伊拉克中部、南部乃至整个中东地区重要的碳酸盐岩储层之一。在伊拉克南部,该地层为Rumaila/West Qurna、Tuba和Zubair等油田提供储层。米什里夫组的顶部是一个区域性不整合的标志:在暖湿气候的推动下,在Turonian (ab. 4.4 My)发生了长时间的区域性隆起,与强降雨有关。在Zubair油田,在Mishrif组上段,有大量证据表明,喀斯特特征对低孔隙度层段的渗透率提高起着重要作用,这对优化生产和油藏管理至关重要。在第一阶段,多速率生产测井和试井分析的整合对于评估渗透率值和突出与岩溶特征相关的增强渗透率(大大高于预期的基质渗透率)非常有用;通过对同一井的图像测井分析,发现了岩溶特征与溶洞密度之间的关系,为在缺乏试井和生产测井信息的井中扩展岩溶特征识别提供了可能。这种方法可以获得大约60口井的岩溶/无岩溶监督数据集。在第二阶段,考虑了不同的地震和地质属性,以研究与岩溶特征的可能相关性。事实上,有一些参数显示出与喀斯特和/或非喀斯特井的某种相关性:频谱分解(特别是10和40 Hz的体积),连续立方体上顶部Mishrif的下沉孔检测及其相关距离,次地震线(从曲率分析和从连续性中获得),到顶部Mishrif的距离。根据这些结果,最有意义的参数被用作神经网络过程(“监督神经网络”)的输入数据,利用监督数据集作为训练数据集(70%)和验证数据集(30%)。最后得到了岩溶特征的概率三维体;与验证数据集的比较,误差范围在0.2左右,即概率体积的成功率约为80%。该工作流程的最终结果是岩溶概率图,这对于指导新井的位置和轨迹非常有用。实际上,两个概念验证案例历史已经证明了这种方法的可靠性。新钻的井根据这些预测图优化了路径,并根据随后的图像测井解释截获了所需的岩溶层段,这些结果对于合适的射孔策略非常有价值,包括低孔隙层段,但具有高空洞密度(岩溶特征)。基于这些有希望的结果,对正在进行的钻井作业进行了相应的优化。
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引用次数: 0
Deep Recurrent Neural Network DRNN Model for Real-Time Step-Down Analysis 实时降压分析的深度递归神经网络DRNN模型
Pub Date : 2019-09-17 DOI: 10.2118/196621-ms
S. Madasu, Keshava P. Rangarajan
A new real-time machine learning model has been developed based on the deep recurrent neural network (DRNN) model for performing step-down analysis during the hydraulic fracturing process. During a stage of the stimulation process, fluids are inserted at the top of the wellhead, while the flow is primarily driven by the difference between the bottomhole pressure (BHP) and reservoir pressure. The major physics and engineering aspects involved are complex and, quite often, there is a high level of uncertainty related to the accuracy of the measured data, as well as intrinsic noise. Consequently, using a machine learning-based method that can resolve both the temporal and spatial non-linear variations has advantages over a pure engineering model. The approach followed provides a long short-term memory (LSTM) network-based methodology to predict BHP and temperature in a fracturing job, considering all commonly known surface variables. The surface pumping data consists of real-time data captured within each stage, such as surface treating pressure, fluid pumping rate, and proppant rate. The accurate prediction of a response variable, such as BHP, is important because it provides the basis for decisions made in several well treatment applications, such as hydraulic fracturing and matrix acidizing, to ensure success. Limitations of the currently available modeling methods include low resolution BHP predictions and an inability to properly capture non-linear effects in the BHP/temperature time series relationship with other variables, including surface pressure, flow rate, and proppant rate. In addition, current methods are further limited by lack of accuracy in the models for fluid properties; the response of the important sub-surface variables strongly depends on the modeled fluid properties. The novel model presented in this paper uses a deep learning neural network model to predict the BHP and temperature, based on surface pressure, flow rate, and proppant rate. This is the first attempt to predict response variables, such as BHP and temperature, in real time during a pumping stage, using a memory-preserving recurrent neural network (RNN) variant, such as LSTM. The results show that the LSTM can successfully model the BHP and temperature in a hydraulic fracturing process. The BHP and temperature predictions obtained were within 5% relative error. The current effort to model BHP can be used for step-down analysis in real time, thereby providing an accurate representation of the subsurface conditions in the wellbore and in the reservoir. The new method described in this paper avoids the need to manage the complex physics of the present methods; it provides a robust, stable, and accurate numerical solution throughout the pumping stages. The method described in this paper is extended to manage step-down analysis using surface-measured variables to predict perforation and tortuosity friction.
基于深度递归神经网络(DRNN)模型,开发了一种新的实时机器学习模型,用于水力压裂过程中的降压分析。在增产过程的某一阶段,流体被注入井口顶部,而流动主要由井底压力(BHP)和油藏压力之间的差异驱动。所涉及的主要物理和工程方面是复杂的,而且往往与测量数据的准确性以及固有噪声有关,存在高度的不确定性。因此,使用基于机器学习的方法可以解决时间和空间非线性变化,比纯工程模型具有优势。接下来的方法提供了一种基于长短期记忆(LSTM)网络的方法,可以在考虑所有已知的地面变量的情况下预测压裂作业中的BHP和温度。地面泵送数据包括在每个阶段捕获的实时数据,如地面处理压力、流体泵送速率和支撑剂速率。对响应变量(如BHP)的准确预测非常重要,因为它为水力压裂和基质酸化等几种井处理应用的决策提供了基础,以确保成功。目前可用的建模方法的局限性包括低分辨率BHP预测,以及无法正确捕捉BHP/温度时间序列与其他变量(包括地面压力、流量和支撑剂用量)之间的非线性影响。此外,目前的方法还受到流体性质模型精度不足的限制;重要地下变量的响应在很大程度上取决于模拟的流体性质。本文提出的新模型使用深度学习神经网络模型,根据地面压力、流量和支撑剂用量来预测BHP和温度。这是第一次尝试在泵送阶段实时预测响应变量,如BHP和温度,使用记忆保留递归神经网络(RNN)变体,如LSTM。结果表明,LSTM可以很好地模拟水力压裂过程中的BHP和温度。得到的BHP和温度预测的相对误差在5%以内。目前对BHP的建模可以用于实时降压分析,从而提供井眼和油藏地下状况的准确表示。本文描述的新方法避免了对现有方法复杂物理特性的管理;它在整个泵送阶段提供了一个强大、稳定和准确的数值解决方案。本文所描述的方法被扩展到管理降压分析,使用表面测量的变量来预测射孔和扭曲摩擦。
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引用次数: 1
Optimization of Waterflooding Strategy Using Artificial Neural Networks 基于人工神经网络的注水策略优化
Pub Date : 2019-09-17 DOI: 10.2118/196643-ms
J. Bruyelle, D. Guérillot
Waterflooding is the main technic to recover hydrocarbons in reservoirs. For a given set of wells (injectors and producers), the choice of injection/production parameters such as pressures, flow rates, and locations of these boundary conditions have a significant impact on the operating life of the wells. As a large number of combinations of these parameters are possible, one of the critical decision to make is to identify an optimal set of these parameters. Using the reservoir simulator directly to evaluate the impact of these sets being unrealistic considering the required number of simulations, a common approach consists of using response surfaces to approximate the reservoir simulator outputs. Several techniques involving proxies model (e.g., kriging, polynomial, and artificial neural network) have been suggested to replace the reservoir simulations. This paper focalizes on the application of artificial neural networks (ANN) as it is commonly admitted that the ANNs are the most efficient one due to their universal approximation capacity, i.e., capacity to reproduce any continuous function. This paper presents a complete workflow to optimize well parameters under waterflooding using an artificial neural network as a proxy model. The proposed methodology allows evaluating different production configurations that maximize the NPV according to a given risk. The optimized solutions can be analyzed with the efficient frontier plot and the Sharpe ratios. An application of the workflow to the Brugge field is presented in order to optimize the waterflooding strategy.
水驱是油藏采油的主要技术。对于给定的一组井(注水井和生产水井),注入/生产参数的选择,如压力、流速和这些边界条件的位置,对井的使用寿命有重大影响。由于这些参数可能有大量的组合,因此需要做出的关键决策之一是确定这些参数的最优集合。考虑到所需的模拟次数,直接使用油藏模拟器来评估这些集合的影响是不现实的,一种常用的方法包括使用响应面来近似油藏模拟器的输出。提出了几种涉及代理模型的技术(如克里格、多项式和人工神经网络)来代替油藏模拟。本文主要讨论人工神经网络(ANN)的应用,因为人们普遍认为人工神经网络是最有效的网络,因为它具有普遍的近似能力,即重现任何连续函数的能力。本文提出了一套利用人工神经网络作为代理模型来优化水驱井参数的完整工作流程。所提出的方法允许根据给定的风险评估不同的生产配置,从而最大化NPV。利用有效边界图和夏普比对优化解进行了分析。为了优化注水策略,将该工作流程应用于布鲁日油田。
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引用次数: 5
Petro-Elastic Modeling Applied to Multi-Porosity/Multi-Permeability Cores through a Simulation to Seismic Method 多孔隙度/多渗透率岩心的石油弹性建模-地震模拟方法
Pub Date : 2019-09-17 DOI: 10.2118/196685-ms
T. Ramsay, Aravind Prabhakar
Multi-rock type cores can be characterized by complex higher order connectivity relationships within an agglomerated petrophysical system. A solution that relates multiphase flow simulation in cores to time-lapse seismic properties in order to examine closed-loop 4D integration is performed at a high level on a plug. While a 4D workflow is not explicitly examined in this work, the requisite petro-elastic modeling (PEM) method based on a simulation-driven interpretation of the Gassmann equation is described and a comparison is made with its empirically derived counterpart. This work illustrates that a simulation-driven petro-elastic modeling approach can be used to generate time-dependent saturated rock properties consistent with seismic attribute description at the plug and core scales. The results demonstrate the simulation-driven approach, of a petro-elastic model embedded in a reservoir simulator, as an alternative to relating pressure and saturation from reservoir simulator-to-seismic-derived properties using a priori empirically based correlations. The method discussed in this paper maintains appreciable continuity with the results of empirically based petro-elastic methods but demonstrates differences commensurate with principal fluid differentiation capability inherent to reservoir simulator-derived data and observed time-lapse seismic response. The significance of applied multi-porosity relationships is further realized upon examination of the time-dependent petro-elastic model results.
多岩型岩心在一个砾岩物性系统内具有复杂的高阶连通性。一种将岩心多相流模拟与时移地震特性联系起来的解决方案,在一个桥塞的高水平上进行了闭环四维积分测试。虽然在这项工作中没有明确检查4D工作流,但描述了基于模拟驱动的Gassmann方程解释的必要的石油弹性建模(PEM)方法,并与经验推导的对应方法进行了比较。这项工作表明,模拟驱动的石油弹性建模方法可以用于生成与桥塞和岩心尺度上的地震属性描述一致的随时间变化的饱和岩石属性。结果表明,油藏模拟器中嵌入的石油弹性模型是一种模拟驱动的方法,可以替代使用先验经验相关性将油藏模拟器的压力和饱和度与地震衍生性质联系起来。本文讨论的方法与基于经验的石油弹性方法的结果保持了相当大的连续性,但也显示出与油藏模拟器导出数据和观测到的时移地震响应固有的主要流体分异能力相称的差异。通过对随时间变化的石油弹性模型结果的检验,进一步认识到应用多孔隙度关系的意义。
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引用次数: 0
An Integrated Workflow for Quantifying the Impact of Geological Uncertainty and Modelling Decisions On STOIIP Estimates and History Matching - A Case Study from the Middle East 地质不确定性量化和建模决策对STOIIP估算和历史匹配影响的集成工作流——以中东地区为例
Pub Date : 2019-09-17 DOI: 10.2118/196679-ms
Mohamed AlBreiki, S. AlAmeri, S. Geiger, P. Corbett
An innovative multi-deterministic scenario workflow was applied to one of the giant and complex carbonate reservoirs in the Middle East. The application of this workflow had the objective to quantify how geological uncertainties and different modelling decisions impact the stock tank oil-initially-in-place (STOIIP) estimates and flow behaviour in this reservoir. In particular, we focused on the uncertainties related to the presence of fractures, reservoir rock typing, and modelling the initial hydrocarbon distribution. Based on the available static and dynamic data we considered two key scenarios, the absence of fractures and the presence of sparse, fault-controlled fractures. In the first scenario, we investigated how different reservoir rock typing methods impact permeability distributions. We further quantified changes in hydrocarbon distribution and analysed how a novel approach that combines capillary pressure and log-derived J-function affects the saturation models. In the second scenario, we used the effective medium theory to calculate permeability multipliers for the regions where fractures are expected. This enabled us to effectively represent fractures in a single-porosity reservoir model. The representativeness of the different models was analysed through blind tests using static data as well as history matching using dynamic data. The most significant findings of our work are that subtle changes in modelling decisions and reservoir rock typing have major consequences for the saturation model, leading to up to 20% change in STOIIP estimates. Such uncertainties must be carried forward in future reservoir management decisions and when estimating reserves. The blind tests showed that a saturation model based on the combination of core- and log-derived J-functions gave the most robust STOIIP estimates. These particular saturation models further led to a much-improved history match, especially for wells located in the transition zone of the reservoir. The best history matches were obtained once sparse, fault-controlled fractures were included in the reservoir model using effective medium theory. The presence of fractures specifically improved the history matching quality for wells located close to the faults; these wells were very difficult to match in the past. Our work clearly demonstrates that a multi-deterministic scenario workflow is key to explore the appropriate range of geological uncertainties, and that, equally important, the impact of different modelling decisions must be accounted for when quantifying uncertainty during reservoir modelling. This is particularly applicable to giant carbonate reservoirs where relatively minor changes in the workflow and data interpretation can have major consequences on STOIIP estimates, dynamic behaviours, and reserve estimates. Multi-stochastic modelling workflows which anchor the reservoir to a single base case are not capable of achieving this.
将一种创新的多确定性情景工作流应用于中东一个大型复杂碳酸盐岩储层。应用该工作流程的目的是量化地质不确定性和不同的建模决策如何影响储罐初始油(STOIIP)估算和该油藏的流动行为。我们特别关注了与裂缝存在、储层岩石类型和初始油气分布建模相关的不确定性。基于现有的静态和动态数据,我们考虑了两种关键情况,即没有裂缝和存在稀疏的断层控制裂缝。在第一个场景中,我们研究了不同的储层岩石类型方法对渗透率分布的影响。我们进一步量化了油气分布的变化,并分析了一种结合毛细管压力和测井衍生j函数的新方法如何影响饱和度模型。在第二种情况下,我们使用有效介质理论来计算可能存在裂缝的区域的渗透率乘数。这使我们能够有效地表示单一孔隙度油藏模型中的裂缝。通过静态数据的盲检验和动态数据的历史匹配,分析了不同模型的代表性。我们工作中最重要的发现是,建模决策和储层岩石类型的细微变化对饱和度模型有重大影响,导致STOIIP估计值变化高达20%。在未来的油藏管理决策和估计储量时,必须考虑到这些不确定性。盲测试表明,基于岩心和对数衍生j函数组合的饱和度模型给出了最稳健的STOIIP估计。这些特殊的饱和度模型进一步提高了历史拟合的准确性,特别是对于位于储层过渡区的井。利用有效介质理论,将稀疏的断控裂缝纳入储层模型,得到最佳历史拟合。裂缝的存在特别提高了断层附近井的历史匹配质量;这些井在过去很难与之匹敌。我们的工作清楚地表明,多确定性情景工作流是探索地质不确定性适当范围的关键,同样重要的是,在油藏建模期间量化不确定性时,必须考虑不同建模决策的影响。这尤其适用于大型碳酸盐岩储层,在这些储层中,工作流程和数据解释的相对微小变化可能会对STOIIP估算、动态行为和储量估算产生重大影响。将油藏固定在单一基本情况下的多随机建模工作流程无法实现这一点。
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引用次数: 1
An Enhanced NMR Workflow for Heterogeneous Carbonates Characterization, Offshore Abu Dhabi 非均相碳酸盐表征的增强核磁共振工作流程,阿布扎比近海
Pub Date : 2019-09-17 DOI: 10.2118/196710-ms
A. Serry, S. Yousif, A. Abouzaid, Piyanuch Kieduppatum, A. Soliman
Full field development of the Upper Jurassic carbonates, offshore Abu Dhabi is exceedingly challenging. The heterogeneous texture, complicated pore systems and intensive lithology changes all mark the regressive cycles of sedimentation. Such complicated characteristics obscure formation evaluation of these formations. Advanced well logging tools and interpretation methodologies are implemented to minimize the petrophysical uncertainties to qualify the products as field development critical elements. This case study highlights a newly applied NMR log interpretation approach. The results help to understand the complex pore system in a tight carbonate layer, along a horizontal drain drilled close to the oil-water contact. NMR log data was acquired in real-time while drilling simultaneously with Gamma Ray, Resistivity and Image Logs. Earlier field studies recommended swapping standard T2 free fluid relaxation cutoff values by actual laboratory NMR measurements for a higher precision suitable for the reservoir texture heterogeneity, the study itself supported the application of higher cutoff values to better discriminate the free fluid in well-connected macro pores from the irreducible which will have a direct impact on the computed permeability. In this case study, a variable free-fluid T2 cutoff was firstly implemented based on arbitrary estimations to match the computed Coates permeability to the offset core values. Free-fluid, irreducible fluids were sequentially computed. A unique NMR-Gamma Inversion (NMR-GI) workflow is further utilized as a mathematically defined approach to process the raw data using probabilistic functions. The result is a more precise pore size distribution, coherent with the geological variations. NMR Capillary pressure was computed. The complex formation texture could be accurately tracked for thousands of feet drilled along the horizontal drain. After validation with offset core, the NMR-GI interpretation was combined with, Archie saturation and Image log analysis for a conclusive assessment. Hydraulic flow units were combined. Successful completion design and production zone selection articulated on the defined open hole log interpretation. NMR while drilling logging and the applied (NMR-GI) methodology prove to be leading tools to assist in resolving carbonate reservoir complexities. Not only that they help to understand the pore system characteristics, but they effectively support well placement, completion and production.
阿布扎比海上上侏罗统碳酸盐岩的全油田开发极具挑战性。非均匀的结构、复杂的孔隙体系和强烈的岩性变化标志着沉积的回退旋回。这些复杂的储层特征给储层评价带来了困难。采用先进的测井工具和解释方法,最大限度地减少岩石物理不确定性,使产品成为油田开发的关键因素。本案例研究强调了一种新应用的核磁共振测井解释方法。该结果有助于了解致密碳酸盐层中复杂的孔隙系统,这些孔隙系统沿着靠近油水接触面的水平泄孔钻取。在钻井过程中,与伽马、电阻率和图像测井同时实时获取核磁共振测井数据。早期的现场研究建议通过实际的实验室核磁共振测量来交换标准的T2自由流体松弛截止值,以获得适合于储层结构非均质性的更高精度,该研究本身支持更高的截止值的应用,以更好地区分连接良好的宏观孔隙中的自由流体和不可还原流体,这将直接影响计算的渗透率。在本案例中,首先基于任意估计实现可变自由流体T2截止,将计算得到的Coates渗透率与偏移岩心值相匹配。依次计算自由流体、不可约流体。一种独特的NMR-Gamma反演(NMR-GI)工作流程被进一步用作一种数学定义的方法来处理使用概率函数的原始数据。结果是更精确的孔径分布,与地质变化一致。计算核磁共振毛细管压力。复杂的地层结构可以沿着水平排水管精确跟踪数千英尺。在偏移岩心验证后,将核磁共振成像解释与阿奇饱和度和图像测井分析相结合,进行结结性评估。液压流量单元组合。成功的完井设计和产层选择是根据裸眼测井解释确定的。核磁共振随钻测井和应用(核磁共振- gi)方法被证明是帮助解决碳酸盐岩储层复杂性的领先工具。它们不仅有助于了解孔隙系统特征,而且有效地支持了井的布置、完井和生产。
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引用次数: 1
The Decomposition of Volumetric Sweep Efficiency and Its Utility 体积扫描效率的分解及其应用
Pub Date : 2019-09-17 DOI: 10.2118/196632-ms
A. AlSofi, M. Blunt
The traditional definition of volumetric sweep efficiency sums the effects of both fingering (arising due to contrasts in mobility) and bypassing (arising due to contrasts in permeability as well as well placement). Accordingly, we cannot quantitatively attribute poor sweep to either bypassing or fingering. Similarly, in EOR, the incremental recovery cannot be quantitatively associated with the reduction of those effects. For such purposes, we rely on visualization and mapping of saturation profiles to quantify and characterize the remaining oil in place including its distribution. . In this work, we propose a complementary method to obtain an instantaneous insight of the remaining oil distribution. We demonstrate the decomposition of fingering and bypassing effects and its utility. We first redefine recovery factors such that we decouple bypassing and fingering effects. We then validate those redefined sweep indicators by examining a 5-spot waterflood and two idealistic polymer floods. Later, we demonstrate the possible utility of those redefined sweep indicators through different examples. In one example, we compare the performance of a shear - thinning polymer to a recovery-equivalent Newtonian polymer. Using fingering and bypassing sweep indicators, we can immediately conclude that the shear-thinning polymer exacerbates bypassing. We recommend the adoption of our redefined sweep indicators in any simulation suite. They provide instant understanding of sweep and hence can be complementary to standard practices of oil saturation mapping and of special value when analyzing the results of multiple realizations and/or development scenarios.
体积扫描效率的传统定义综合了指进(由于流动性的差异)和旁通(由于渗透率和井位的差异)的影响。因此,我们不能定量地将扫频差归因于旁路或指法。同样,在EOR中,增量采收率不能定量地与这些影响的减少联系起来。为此,我们依靠饱和度曲线的可视化和映射来量化和表征剩余油的分布。在这项工作中,我们提出了一种补充方法来获得剩余油分布的瞬时洞察。我们演示了指法和旁路效果的分解及其效用。我们首先重新定义恢复因子,这样我们就可以解耦旁路和指法效应。然后,我们通过测试5点注水和两种理想聚合物驱来验证这些重新定义的波及指标。稍后,我们将通过不同的示例演示这些重新定义的扫描指示器的可能用途。在一个例子中,我们比较了剪切减薄聚合物与恢复等效牛顿聚合物的性能。使用指法和旁路扫描指标,我们可以立即得出结论,剪切减薄聚合物加剧了旁路。我们建议在任何模拟套件中采用我们重新定义的扫描指示器。它们提供了对扫描的即时理解,因此可以补充油饱和度测绘的标准实践,并且在分析多种实现和/或开发方案的结果时具有特殊价值。
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引用次数: 0
Simulation of Enhanced Oil Recovery in Pre-Salt Reservoirs: The Effect of High CO2 Content on Low Salinity Water Alternating Gas Injection 盐下油藏提高采收率模拟:高CO2含量对低矿化度水交替注气的影响
Pub Date : 2019-09-17 DOI: 10.2118/196684-ms
A. S. Carvalhal, G. Costa, S. V. D. Melo
The high CO2 content of Brazil’s pre-salt fields, which may reach values from 20% to 44% molar, presents both a challenge as well as an opportunity. CO2 stripped from the produced gas cannot be released into the atmosphere due to environmental restrictions. Therefore, the whole amount of CO2 produced should be continuously reinjected into the reservoir. This work investigates the effect of CO2 content on the low salinity water alternating CO2 injection technique (CO2LSWAG) using a commercial compositional reservoir simulator. In these field-scale simulations, CO2 is stripped from the produced gas and reinjected into the reservoir. Primary oil recovery methods such as CO2 flooding and LSW flooding are also simulated. Chemical reactions between CO2 and the minerals present in the reservoir are modeled. Wettability change is assumed to be the main mechanism for improved oil recovery due to low salinity water injection. Compositional simulations of CO2 injection usually assume a constant injected gas rate. In this case, CO2 is supposed to come from an external source. In many petroleum reservoirs this assumption is true. Three factors are assessed in the present work. The first one is the natural reservoir pressure, which is the main driving force in primary production. The second factor is the amount of CO2 available for injection. The third one is the wettability change promoted by the reaction involving CO2. It is shown that in primary production, higher CO2 content leads to quicker depletion of the natural energy of the reservoir, leading to lower oil recovery. Nevertheless, higher CO2 content also means that more gas is available for reinjection, potentially leading to increased oil production. Finally, as CO2 reacts with minerals it promotes a change in wettability from an oil-wet to a water-wet state. It is shown that the CO2 content is an important variable to be assessed in a high CO2 content reservoir. Optimal injection practices must take these three aspects into consideration.
巴西盐下油田的二氧化碳含量很高,可能达到20%至44%摩尔摩尔,这既是挑战,也是机遇。由于环境限制,从生产气体中剥离的二氧化碳不能释放到大气中。因此,产生的全部CO2应连续回注到储层中。本研究利用商业油藏组成模拟器研究了CO2含量对低矿化度水交替CO2注入技术(CO2LSWAG)的影响。在这些油田规模的模拟中,二氧化碳从采出气体中剥离出来并重新注入储层。模拟了CO2驱油和LSW驱油等初级采油方法。模拟了二氧化碳和储层中存在的矿物质之间的化学反应。润湿性变化被认为是低矿化度注水提高采收率的主要机制。二氧化碳注入成分模拟通常假设注入气体速率恒定。在这种情况下,二氧化碳应该来自外部来源。在许多油藏中,这种假设是正确的。在目前的工作中评估了三个因素。一是储层自然压力,它是一次开采的主要动力。第二个因素是可供注入的二氧化碳量。三是CO2反应促进的润湿性变化。结果表明,在初采阶段,CO2含量越高,储层自然能量消耗越快,采收率越低。然而,较高的二氧化碳含量也意味着有更多的天然气可用于回注,这可能导致石油产量的增加。最后,当二氧化碳与矿物质发生反应时,它会促进润湿性从油湿状态转变为水湿状态。研究表明,在高CO2含量油藏中,CO2含量是一个重要的评价变量。最佳的注射方法必须考虑这三个方面。
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引用次数: 2
Thief Zone Characterization and its Impact on Well Performance Based on Surveillance Data, Experimental Data and Theoretical Analysis for a Carbonate Reservoir 基于监测数据、实验数据和理论分析的碳酸盐岩储层贼层特征及其对油井性能的影响
Pub Date : 2019-09-17 DOI: 10.2118/196627-ms
Chenji Wei, Jie Zheng, Xiaohu Ouyang, Yutao Ding, Mingming Ding, Shiyao Lin, Hongqing Song
Understanding the heterogeneity is critical for a successful water injection in a carbonate reservoir. Thief zone is one of the most obvious forms of heterogeneity, which indicates the thin layer with higher permeability compared to the average reservoir permeability. The existence of thief zone results in earlier water breakthrough and faster water cut increase, which then lead to lower sweep efficiency and smaller recovery factor. Therefore, determining the distribution of thief zone and its impact towards production, and proposing a corresponding development plan are very important. In this paper, a novel method is established to determine the thief zone distribution based on dynamic surveillance data. A new index is proposed as the relative contribution index to characterize the relative contribution of a certain layer, which is fundamental for thief zone determination. In addition, effect on water flooding development of thief zone's location is studied by experimental and theoretical analysis. The changes of water cut and production rate are analyzed under different conditions such as location of the thief zone, injection rate, and variogram. Finally, optimized development strategy is proposed to deal with the existence of thief zone. Distribution of thief zone is characterized based on the proposed method, which indicates that thief zone development has intimate relationship with depositional facies and diagenesis. Experimental and theoretical analysis results show that the present model considering stratified water-flood is consistent with the experimental results. The water displacement effect is the best when the thief zone is located in the upper reservoir. This paper also points out the optimal adjustment period for water shutoff and profile control of the reservoir with thief zones. In addition, the greater the injection rate, the faster the water cut increase. Furthermore, the smaller the variogram, the slower the water cut increase, and the later the water breakthrough time. This study provides a method to characterize thief zone, which can be used as a reference for similar oilfield development. In addition, it provides a quick and reasonable guide in the later adjustment of water flooding development of carbonate reservoirs with thief zones.
了解碳酸盐岩储层的非均质性对于成功注水至关重要。“贼”层是非均质性最明显的一种表现形式,其厚度较薄,渗透率高于平均渗透率。小偷层的存在导致侵水时间早,含水增加速度快,从而导致波及效率低,采收率小。因此,确定盗贼带的分布及其对生产的影响,并提出相应的开发方案是非常重要的。本文提出了一种基于动态监控数据确定盗贼区域分布的新方法。提出了一种新的相对贡献度指标来表征某一层的相对贡献度,这是确定盗贼区域的基础。此外,通过实验和理论分析,研究了储层位置对水驱开发的影响。分析了盗窃层位置、注入速度和变异函数等不同条件下含水率和产量的变化规律。最后,针对“贼带”的存在,提出了优化的发展策略。利用该方法对盗贼带的分布特征进行了表征,表明盗贼带的发育与沉积相和成岩作用密切相关。实验和理论分析结果表明,考虑分层水驱的模型与实验结果一致。当贼带位于上部储层时,驱水效果最好。指出了带贼层油藏堵水调剖的最佳调整期。此外,注入速率越大,含水率增加越快。变异函数越小,含水率增加越慢,破水时间越晚。本研究提供了一种储层特征的方法,可为类似油田的开发提供参考。为含贼带碳酸盐岩储层水驱开发后期调整提供了快速合理的指导。
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引用次数: 2
Optimization of Oil Production in an Oil Rim Reservoir Using Numerical Simulation with Focus on IOR/EOR Application 应用数值模拟优化油环油藏产油量——以IOR/EOR应用为重点
Pub Date : 2019-09-17 DOI: 10.2118/196709-ms
Maroua Jaoua, M. Rafiee
Development of oil rim reservoirs is challenging and could lead to low oil recovery, if multiple determining factors are not well understood, that influences successful field development concept. It requires detailed analysis and development of specific procedures to optimize the oil production from a thin oil rim underlaying gas cap. Few IOR/EOR applications for oil rim development have been reported in the literature so far. This study presents a concept for the optimization of oil production from an oil rim reservoir by numerical simulation. As a starting point, a representative sector of the field was selected for the initial analysis. It was decided to perform IOR/EOR methods including water/gas flooding/injection and surfactant flooding using inverted five-spot horizontal well pattern, for the application in the selected sector. Upon execution of the detailed sensitivity analysis, the pattern was optimized by its characteristic geometric variables including the length of the vertical/horizontal section of the well, the location of the wells, lateral well distances and the orientation of the pattern. The optimization was performed by setting an objective function to improve recovery factor and reduce water/gas cut by using the differential evolution algorithm. The latter was run until converging, and the optimal solution was used to perform further IOR/EOR studies. Finally, after selection of a base-case scenario and best well pattern, IOR/EOR options were evaluated, and the comparative results were reported. The generated results show that the application of 5-spot horizontal well pattern in the oil rim reservoir could increase the oil recovery by water flooding, but with low sweep efficiency. The losses of injected water into the underlaying aquifer and up laying gas gap are large. Immiscible gas injection into the gas cap can support the pressure but massively increases the gas cut. In addition, displacement efficiency by gas flooding is poor. Simulation results of the surfactant flooding case shows better displacement efficiency compared to water flooding. Also, the possibility of reducing residual oil saturation could increase the ultimate oil recovery but at very late time.
油环油藏的开发具有挑战性,如果对多个决定因素的理解不到位,可能会导致采收率低,从而影响油田的成功开发理念。这需要详细的分析和开发特定的程序来优化气顶下薄油环的产油量。到目前为止,文献中很少有关于油环开发的IOR/EOR应用的报道。本文提出了一种利用数值模拟方法优化油环油藏产油量的概念。作为起点,选择了该领域的一个代表性部门进行初步分析。为了在选定的区块中应用,决定采用水/气驱/注入和表面活性剂驱等IOR/EOR方法,采用倒五点水平井模式。在进行了详细的灵敏度分析后,根据井的垂直/水平段长度、井的位置、水平井距离和井的方向等特征几何变量对该模式进行了优化。利用差分进化算法设定了提高采收率、减少水/气侵的目标函数,进行了优化。后者一直运行到收敛,然后使用最优解进行进一步的IOR/EOR研究。最后,在选择了基本情景和最佳井网后,对IOR/EOR方案进行了评估,并报告了对比结果。结果表明,在油环油藏中应用5点水平井网可以提高水驱采收率,但波及效率较低。注入水进入下垫含水层和上垫气隙损失较大。向气顶注入非混相气可以支撑压力,但会大大增加气侵。此外,气驱驱替效率较差。模拟结果表明,表面活性剂驱的驱替效果优于水驱。此外,降低残余油饱和度的可能性可以提高最终采收率,但时间很晚。
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引用次数: 4
期刊
Day 3 Thu, September 19, 2019
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