Reservoir History Matching Using Constrained Ensemble Kalman Filter and Particle Filer Methods

Reservoir History Matching Using Constrained Ensemble Kalman Filter and Particle Filer Methods
Author: Abhiniandhan Raghu
Publisher:
Total Pages: 126
Release: 2014
Genre: Ecological heterogeneity
ISBN:

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The high heterogeneity of petroleum reservoirs, represented by their spatially varying rock properties (porosity and permeability), greatly dictates the quantity of recoverable oil. In this work, the estimation of these rock properties, which is crucial for the future performance prediction of a reservoir, is carried out through a history matching technique using constrained ensemble Kalman filtering (EnKF) and particle filtering (PF) methods. The first part of the thesis addresses some of the main limitations of the conventional EnKF. The EnKF, formulated on the grounds of Monte Carlo sampling and the Kalman filter (KF), arrives at estimates of parameters based on statistical analysis and hence could potentially yield reservoir parameter estimates that are not geologically realistic and consistent. In order to overcome this limitation, hard and soft data constraints in the recursive EnKF estimation methodology are incorporated. Hard data refers to the actual values of the reservoir parameters at discrete locations obtained by core sampling and well logging. On the other hand, the soft data considered here is obtained from the variogram, which characterize the spatial correlation of the rock properties in a reservoir. In this algorithm, the correlation matrix obtained after the unconstrained EnKF update is transformed to honour the true correlation structure from the variogram by applying a scaling and projection method. This thesis also deals with the problem of spurious correlation induced by the Kalman gain computations in the EnKF update step, potentially leading to erroneous update of parameters. In order to solve this issue, a covariance localization-based EnKF coupled with geostatistics is implemented in reservoir history matching. These algorithms are implemented on two synthetic reservoir models and their efficacy in yielding estimates consistent with the geostatistics is observed. It is found that the computational time involved in the localization-based EnKF framework for reservoir history matching is considerably reduced owing to the reduction in the size of the parameter space in the EnKF update step. Also, the geostatistics-based covariance localization performs better in capturing the spatial heterogeneity and variability of the reservoir permeability than the traditional methods. In the second part of the thesis, we extend the history matching implementation using the particle filtering. Reservoir models, being nonlinear, the distributions of the noise and parameters are generally non-Gaussian in nature. Since the EnKF may fail to obtain accurate estimates when the distributions involved in the model are non-Gaussian, we attempt to use a completely Bayesian filter, the particle filter, to estimate reservoir parameters. In addition, the geostatistics-based covariance localization is also coupled with the particle filter and is found to perform better than the filter without any localization.

Ensemble-based Reservoir History Matching Using Hyper-reduced-order Models

Ensemble-based Reservoir History Matching Using Hyper-reduced-order Models
Author: Seonkyoo Yoon
Publisher:
Total Pages: 106
Release: 2016
Genre:
ISBN:

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Subsurface flow modeling is an indispensable task for reservoir management, but the associated computational cost is burdensome owing to model complexity and the fact that many simulation runs are required for its applications such as production optimization, uncertainty quantification, and history matching. To relieve the computational burden in reservoir flow modeling, a reduced-order modeling procedure based on hyper-reduction is presented. The procedure consists of three components: state reduction, constraint reduction, and nonlinearity treatment. State reduction based on proper orthogonal decomposition (POD) is considered, and the impact of state reduction, with different strategies for collecting snapshots, on accuracy and predictability is investigated. Petrov- Galerkin projection is used for constraint reduction, and a hyper-reduction that couples the Petrov-Galerkin projection and a 'gappy' reconstruction is applied for the nonlinearity treatment. The hyper-reduction method is a Gauss-Newton framework with approximated tensors (GNAT), and the main contribution of this study is the presentation of a procedure for applying the method to subsurface flow simulation. A fully implicit oil-water two-phase subsurface flow model in three-dimensional space is considered, and the application of the proposed hyper-reduced-order modeling procedure achieves a runtime speedup of more than 300 relative to the full-order method, which cannot be achieved when only constraint reduction is adopted. In addition, two types of sequential Bayesian filtering for history matching are considered to investigate the performance of the developed hyper-reduced-order model to relive the associated computational cost. First, an ensemble Kalman filter (EnKF) is considered for Gaussian system and a procedure embedding the hyper-reduced model (HRM) into the EnKF is presented. The use of the HRM for the EnKF significantly reduces the computational cost without much loss of accuracy, but the combination requires a few remedies such as clustering to find an optimum reduced-order model according to spatial similarity of geological condition, which causes an additional computation. For non-Gaussian system, an advanced particle filter, known as regularized particle filter (RPF), is considered because it does not take any distributional assumptions. Particle filtering has rarely been applied for reservoir history matching due to the fact that it is hard to locate the initial particles on highly probable regions of state spaces especially when large scale system is considered, which makes the required number of particles scale exponentially with the model dimension. To resolve the issues, reparameterization is adopted to reduce the order of the geological parameters. For the reparameterization, principal component analysis (PCA) is used to compute the reduced space of the model parameters, and by constraining the filtering analysis with the computed subspace the required number of initial particles can be reduced down to a manageable level. Consequently, a huge computational saving is achieved by embedding the HRM into the RPF. Furthermore, the additional cost of clustering required to identify the geospatially optimum reduced-order model is saved because the advanced particle filter allows to easily identify the groups of geospatially similar particles.

History-matching of Petroleum Reservoir Models by the Ensemble Kalman Filter and Parameterization Methods

History-matching of Petroleum Reservoir Models by the Ensemble Kalman Filter and Parameterization Methods
Author: Leila Heidari
Publisher:
Total Pages: 224
Release: 2011
Genre:
ISBN:

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History-matching enables integration of data acquired after the production in the reservoir model building workflow. Ensemble Kalman Filter (EnKF) is a sequential assimilation or history-matching method capable of integrating the measured data as soon as they are obtained. This work is based on the EnKF application for History-matching purposes and is divided into two main sections. First section deals with the application of the EnKF to several case studies in order to better understand the merits and shortcomings of the method. These case studies include two synthetic case studies (a simple one and a rather complex one), a Facies model and a real reservoir model. In most cases the method is successful in reproducing the measured data. The encountered problems are explained and possible solutions are proposed. Second section deals with two newly proposed algorithms combining the EnKF with two parameterization methods: pilot point method and gradual deformation method, which are capable of preserving second order statistical properties (mean and covariance). Both developed algorithms are applied to the simple synthetic case study. For the pilot point method, the application was successful through an adequate number and proper positioning of pilot points. In case of the gradual deformation, the application can be successful provided the background ensemble is large enough. For both cases, some improvement scenarios are proposed and further applications to more complex scenarios are recommended.

An Ensemble Kalman Filter Module for Automatic History Matching

An Ensemble Kalman Filter Module for Automatic History Matching
Author: Baosheng Liang
Publisher:
Total Pages: 0
Release: 2007
Genre: Hydrocarbon reservoirs
ISBN:

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The data assimilation process of adjusting variables in a reservoir simulation model to honor observations of field data is known as history matching and has been extensively studied for few decades. However, limited success has been achieved due to the high complexity of the problem and the large computational effort required by the practical applications. An automatic history matching module based on the ensemble Kalman filter is developed and validated in this dissertation. The ensemble Kalman filter has three steps: initial sampling, forecasting through a reservoir simulator, and assimilation. The initial random sampling is improved by the singular value decomposition, which properly selects the ensemble members with less dependence. In this way, the same level of accuracy is achieved through a smaller ensemble size. Four different schemes for the assimilation step are investigated and direct inverse and square root approaches are recommended. A modified ensemble Kalman filter algorithm, which addresses the preference to the ensemble members through a nonequally weighting factor, is proposed. This weighted ensemble Kalman filter generates better production matches and recovery forecasting than those from the conventional ensemble Kalman filter. The proposed method also has faster convergence at the early time period of history matching. Another variant, the singular evolutive interpolated Kalman filter, is also applied. The resampling step in this method appears to improve the filter stability and help the filter to deliver rapid convergence both in model and data domains. This method and the ensemble Kalman filter are effective for history matching and forecasting uncertainty quantification. The independence of the ensemble members during the forecasting step allows the benefit of high-performance computing for the ensemble Kalman filter implementation during automatic history matching. Two-level computation is adopted; distributing ensemble members simultaneously while simulating each member in a parallel style. Such computation yields a significant speedup. The developed module is integrated with reservoir simulators UTCHEM, GEM and ECLIPSE, and has been implemented in the framework Integrated Reservoir Simulation Platform (IRSP). The successful applications to two and three-dimensional cases using blackoil and compositional reservoir cases demonstrate the efficiency of the developed automatic history matching module.

History Matching and Uncertainty Characterization

History Matching and Uncertainty Characterization
Author: Alexandre Emerick
Publisher: LAP Lambert Academic Publishing
Total Pages: 264
Release: 2012-04
Genre:
ISBN: 9783659107283

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In the last decade, ensemble-based methods have been widely investigated and applied for data assimilation of flow problems associated with atmospheric physics and petroleum reservoir history matching. Among these methods, the ensemble Kalman filter (EnKF) is the most popular one for history-matching applications. The main advantages of EnKF are computational efficiency and easy implementation. Moreover, because EnKF generates multiple history-matched models, EnKF can provide a measure of the uncertainty in reservoir performance predictions. However, because of the inherent assumptions of linearity and Gaussianity and the use of limited ensemble sizes, EnKF does not always provide an acceptable history-match and does not provide an accurate characterization of uncertainty. In this work, we investigate the use of ensemble-based methods, with emphasis on the EnKF, and propose modifications that allow us to obtain a better history match and a more accurate characterization of the uncertainty in reservoir description and reservoir performance predictions.

Continuous Reservoir Model Updating Using an Ensemble Kalman Filter with a Streamline-based Covariance Localization

Continuous Reservoir Model Updating Using an Ensemble Kalman Filter with a Streamline-based Covariance Localization
Author: Elkin Rafael Arroyo Negrete
Publisher:
Total Pages:
Release: 2007
Genre:
ISBN:

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This work presents a new approach that combines the comprehensive capabilitiesof the ensemble Kalman filter (EnKF) and the flow path information from streamlines to eliminate and/or reduce some of the problems and limitations of the use of the EnKF for history matching reservoir models. The recent use of the EnKF for data assimilation and assessment of uncertainties in future forecasts in reservoir engineering seems to be promising. EnKF provides ways of incorporating any type of production data or timelapse seismic information in an efficient way. However, the use of the EnKF in history matching comes with its shares of challenges and concerns. The overshooting of parameters leading to loss of geologic realism, possible increase in the material balance errors of the updated phase(s), and limitations associated with non-Gaussian permeability distribution are some of the most critical problems of the EnKF. The use of larger ensemble size may mitigate some of these problems but are prohibitively expensive inpractice. We present a streamline-based conditioning technique that can be implemented with the EnKF to eliminate or reduce the magnitude of these problems, allowing for the use of a reduced ensemble size, thereby leading to significant savings in time during field scale implementation. Our approach involves no extra computational cost and is easy to implement. Additionally, the final history matched model tends to preserve most of the geological features of the initial geologic model. A quick look at the procedure is provided that enables the implementation of this approach into the current EnKF implementations. Our procedure uses the streamline path information to condition the covariance matrix in the Kalman Update. We demonstrate the power and utility of our approach with synthetic examples and a field case. Our result shows that using the conditioned technique presented in this thesis, the overshooting/under shooting problems disappears and the limitation to work with non-Gaussian distribution is reduced. Finally, an analysis of the scalability in a parallel implementation of our computer code is given.

Re-sampling the Ensemble Kalman Filter for Improved History Matching and Characterizations of Non-gaussian and Non-linear Reservoir Models

Re-sampling the Ensemble Kalman Filter for Improved History Matching and Characterizations of Non-gaussian and Non-linear Reservoir Models
Author: Siavash Nejadi
Publisher:
Total Pages: 203
Release: 2014
Genre: Reservoirs
ISBN:

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Reservoir simulation models play an important role in the production forecasting and field development planning. To enhance their predictive capabilities and capture the uncertainties in model parameters, stochastic reservoir models should be calibrated to both geologic and flow observations. The relationship between production performance and model parameters is vastly non-linear, rendering history matching process a challenging task. The Ensemble Kalman Filter (EnKF) is a Monte-Carlo based technique for assisted history matching and real-time updating of reservoir models. EnKF works efficiently with Gaussian variables, but it often fails to honor the reference probability distribution of the model parameters where the distribution of model parameters are non-Gaussian and the system dynamics are strongly nonlinear. In this thesis, novel sampling procedures are proposed to honor geologic information in reservoirs with non-Gaussian model parameters. The methodologies include generating multiple geological models and updating the uncertain parameters using dynamic flow responses using iterative EnKF technique. Two new re-sampling steps are presented for characterization of multiple facies reservoirs. After certain number of assimilation steps, the updated ensemble is used to generate a new ensemble that is conditional to both the geological information and the early production data. Probability field simulation and a novel probability weighted re-sampling scheme are introduce to re-sample a new ensemble. After the re-sampling step, iterative EnKF is again applied on the ensemble members to assimilate the remaining production history. A new automated dynamic data integration workflow is implemented for characterization and uncertainty assessment of fracture reservoir models. This new methodology includes generating multiple discrete fracture network (DFN) models, upscaling the models for flow simulation, and updating the DFN model parameters using dynamic flow responses. The assisted history matching algorithm entails combining a probability weighted sampling with iterative EnKF. The performances of the introduced methodologies are evaluated by performing various simulation studies for different synthetic and field case studies. The qualities of the final matching results are assessed by examining the geological realism of the updated ensemble using the reference probability distribution of the model parameters and computing the predicted dynamic data mismatch.

Initial Member Selection and Covariance Localization Study of Ensemble Kalman Filter Based Data Assimilation

Initial Member Selection and Covariance Localization Study of Ensemble Kalman Filter Based Data Assimilation
Author: Yeung Yip
Publisher:
Total Pages:
Release: 2011
Genre:
ISBN:

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Ensemble Kalman Filter (EnKF) is a data assimilation technique that has gained increasing interest in the application of petroleum history matching in recent years. The basic methodology of the EnKF consists of the forecast step and the update step. This data assimilation method utilizes a collection of state vectors, known as an ensemble, which are simulated forward in time. In other words, each ensemble member represents a reservoir model (realization). Subsequently, during the update step, the sample covariance is computed from the ensemble, while the collection of state vectors is updated using the formulations which involve this updated sample covariance. When a small ensemble size is used for a large, field-scale model, poor estimate of the covariance matrix could occur (Anderson and Anderson 1999; Devegowda and Arroyo 2006). To mitigate such problem, various covariance conditioning schemes have been proposed to improve the performance of EnKF, without the use of large ensemble sizes that require enormous computational resources. In this study, we implemented EnKF coupled with these various covariance localization schemes: Distance-based, Streamline trajectory-based, and Streamline sensitivity-based localization and Hierarchical EnKF on a synthetic reservoir field case study. We will describe the methodology of each of the covariance localization schemes with their characteristics and limitations.