Dual-permeability Model Research Articles

A New Two-dimensional Dual-permeability Model of Preferential Water Flow in the Vadose Zone

LEAK2D (L2D) is a new, two-dimensional, dual-permeability model for the simulation of preferential water flow in the vadose zone, allowing for the continuous exchange of water between the matrix and the fracture domain. It is based on the two-dimensional Richards equation for the simulation of flow in the matrix domain and on the kinematic wave equation for the simulation of flow in the fracture domain. The Richards equation is solved by a combination of the Alternating Direction Implicit method and the Douglas-Jones predictor-corrector method. This combination leads to a very efficient, stable, and time-consuming method. A variable time step is used by which any instability of the numerical solution is avoided. The water transfer from the fracture to the matrix domain is estimated as a first-order approximation of the water diffusion equation. The model was used to satisfactorily simulate preferential flow under an extreme rainfall/irrigation event. The exchange of water between the two domains depends on parameters which have physical meaning; however, their exact values are difficult to be determined or measured. Based on the most common values of these parameters found in the literature, a sensitivity analysis was performed to define their effect on the output of the model.

Study on influence of geometric characteristics of cracks on HAM coupling transfer and thermal performance of multi-layer cellular concrete wall

The effect of concrete cracks on the evaluation of the thermal performance of walls has not been effectively considered within the assessment of the thermal and hygroscopic performance of buildings. Based on the dual permeability model, a conjugate method is proposed to reconstruct the PDE equation of unsaturated porous materials with cracks. The reliability of the model is verified from three angles: the heat-moisture coupling benchmark of matrix material, the analytical solution of two-dimensional single fracture heat flow coupling problem and the moisture absorption problem of unsaturated cracks. The reliability of the model is verified from three perspectives: the benchmark of thermal and hygroscopic coupling of matrix materials, the analytical solution to the two-dimensional single-break thermal flow coupling problem, and the hygroscopic problem of unsaturated cracks. The effect of heat and moisture transfer in cracked concrete was quantified by detailed modeling of cracks in terms of the probability of over-penetration, crack roughness, crack density, length, and angle of a two-dimensional discrete crack network, showing that cracks contribute to moisture transfer. This is followed by a 10 day experimental simulation of the meteorological environment, comparing the quantities of moisture accumulation, thermal performance, internal surface temperature and humidity within the fractured and non-fractured wall structures, illustrating the potential adverse effects of cracks on thermal performance and moisture transfer in walls under characteristic conditions. Finally, the necessity of applying moisture-proof layer to the damaged wall is demonstrated by comparing the results before and after the application of the moisture-proof layer.

Improved Permeability Model of the Binary Gas Interaction within a Two-Phase Flow and its Application in CO2-Enhanced Coalbed Methane Recovery.

In this paper, we develop a dual-porosity dual-permeability model for binary gas migration to explore the permeability evolution in the matrix and fracture in the process of a gas–water two-phase flow during CO2-enhanced coalbed methane (CO2-ECBM) recovery in coal reservoirs. This mechanistic model accommodates the effects of elastic deformation caused by the effective stress change in the matrix and fracture, the swelling/shrinkage deformation of the matrix caused by adsorption/desorption, the convection and diffusion of gas, and the discharge of water. Specifically, the time-dependent matrix swelling, from initially completely reducing the fracture aperture to finally affecting the coal bulk volume, is considered by the invaded volume fraction involving binary gas intrusion. The model is validated through laboratory data and applied to examine the permeability evolution of CO2-ECBM recovery for 10 000 days. Furthermore, we analyze the sensitivity of some selected initial parameters to capture the key factors affecting CO2-ECBM recovery. Our modeling results show that the permeability evolution can be divided into two stages during the process, where stage I is dominated by effective stress and stage II is dominated by adsorption/desorption. Increasing the injection pressure or initial permeability advances the start of stage II. The decrease in initial water saturation causes the permeability to change more drastically and the time of stage II to appear earlier until a time long enough, after which little effect is seen on the permeability results.

Triple-Porosity and Dual-Permeability Productivity Prediction Model of CBM Wells Considering Complex Flow Regimes

The productivity evaluation of CBM wells can yield significant insights into exploring the patterns of CBM production, predicting the effectiveness of the CBM well and reservoir stimulation, optimizing the gas reservoir development program, and developing a reasonable production system, for the purpose of facilitating efficient development of CBM. In particular, to accurately evaluate CBM productivity, we should establish the corresponding mathematical model of fluid flow through porous media and productivity evaluation model based on a clear understanding of CBM occurrence states and mechanisms of its flow through porous media. After considering the effects of slip flow, Knudsen diffusion, surface diffusion, stress sensitivity, and matrix shrinkage on fluid mass transfer, we have put forward a triple-porosity and dual-permeability mathematical model to predict CBM productivity that incorporates matrix gas desorption, complex flow in matrix pores, and gas–water two-phase flow in a cleat system. In combination with reservoir characteristic parameters, a case study of Ma-26 well in the Mabidong block in the south of the Qinshui Basin, we carried out a numerical simulation of the productivity of a fractured CBM well and analyzed the effects (on production performance) of occurrence states, cleat system permeability, complex flow regimes in the matrix, Langmuir pressure, and Langmuir volume on production are provided. The results show that 1) in the initial drainage and production stage of CBM wells, both free gas and adsorbed gas are produced simultaneously, while adsorbed gas dominates the production in later stages; 2) the peak output and cumulative output of CBM wells increase significantly with the rise in cleat system permeability; 3) the increase of Langmuir pressure, volume, and matrix porosity are conducive to the increase of CBM production. The research has considerable reference value for work on mechanisms of CBM flow in porous media and post fracturing productivity evaluation of CBM and also provides a theoretical basis for fieldwork in CBM development.

A new numerical simulation method of hydrogen and carbon compounds in shale reservoir

Hydrogen energy can be produced by the decomposition of hydrogen and carbon compounds. A numerical analysis method of accuracy and efficiency provides important reference value for optimizing development plans and predicting production performance of hydrogen and carbon compounds. In this work, embedded discrete fracture model (EDFM) is used to study the production performance of hydrogen and carbon compounds under non-liner seepage under the threshold pressure gradient and complex fracture systems consist of the hydraulic fractures, secondary fractures, natural fractures. A dual-permeability model of the same case is also constructed as a comparison study to analyze the development of hydrogen and carbon compounds. On this basis, the influence of threshold pressure gradient on production of hydrogen and carbon compounds is quantitatively evaluated in this paper to modify the numerical model and a novel method for the simulation of fractured hydrogen and carbon compounds reservoirs is provided. Through model comparison, the impact of fractures in the reservoir on production can reach 289.1%. A dual-permeability model of the same case is also constructed as a comparison study to analyze the development of the reservoir and the result shows a 7.9% distinction on the cumulative production. It is analyzed that when the threshold pressure gradient is increased from 0.1 MPa/m to 0.6 MPa/m, the output decline of different models ranges from 6% to 15% and a novel method improving model fidelity for the simulation of fracture reservoirs is provided.

Streamline Tracing and Applications in Dual-Porosity Dual-Permeability Models

Summary Streamline-based methods have proven to be effective for various subsurface flow and transport modeling problems. However, the applications are limited in dual-porosity and dual-permeability (DPDK) system due to the difficulty in describing interactions between matrix and fracture during streamline tracing. In this work, we present a robust streamline tracing algorithm for DPDK models and apply the new algorithm to rate allocation optimization in a waterflood reservoir. In the proposed method, streamlines are traced in both fracture and matrix domains. The interfluxes between fracture and matrix are described by switching streamlines from one domain to another using a probability computed based on the ratio of interfluxes to total fluxes within the domain. The approach is fundamentally similar to the existing streamline tracing technique and can be utilized in streamline-assisted applications, such as flow diagnostics, history matching, and production optimization. The proposed method is benchmarked with a finite volume (FV)-based approach where grid-based time-of-flight (TOF) distributions were obtained by solving the stationary transport equation. We first validated our method using simple examples. Visual TOF comparisons as well as tracer concentration and allocation factors at wells show good agreement. Next, we applied the proposed method to field-scale models to demonstrate the robustness. The results show that our method offers reduced numerical artifacts and better represents reservoir heterogeneity and well connectivity with subgrid resolutions. The proposed method is then used for rate allocation optimization in DPDK models. A streamline-based gradient-free algorithm is used to optimize net present value (NPV) by adjusting both injection and production well rates under operational constraints. The results show that the optimized schedule offers significant improvement in recovery factor, NPV, and sweep efficiency compared to the base scenario using equal rate injection and production. The optimization algorithm is computationally efficient, as it requires only a few forward reservoir simulations. A novelty of this work is the streamline tracing algorithm in DPDK reservoir models. The proposed method is simple and easy to implement to existing streamline-based frameworks and is applicable to field-scale reservoir models for flow diagnostics and rate allocation optimization.

Effect of fractional interporosity flow on elastic waves propagation through a fluid-saturated double-porosity interlayer

The reflection and transmission behaviors of elastic waves through a fluid-saturated double-porosity interlayer are studied in present work. In order to simulate the interporosity flow, which cannot be appropriately described by the Darcy’s law, a modified transport equation using fractional order derivative is introduced to the double-porosity, dual-permeability model for the wave propagation in fluid-saturated double-porosity solid. The reflection and transmission coefficients are derived by satisfying the interfacial conditions of tractions and displacements. As a main feature of fluid-saturated double-porosity solid, the influences of interporosity flow on the wave propagation behavior are mainly studied. The numerical results are provided and shown graphically. It is observed that the reflection/transmission and the energy dissipation behavior are affected noticeably by the interporosity flow.

Improving hydrogeological understanding through well-test interpretation by diagnostic plot and modelling: a case study in an alluvial aquifer in France

The study of groundwater resources using pumping test data is usually carried out with the Theis solution, which enables the hydraulic parameters of porous aquifers such as the transmissivity and storage coefficient, to be estimated from the water-level drawdown. However, the data fitting can fail and provide only an indication that the pumped aquifer has a complex structure. Here, a diagnostic plot on log-derivative drawdown is used to identify flow regimes and thus aquifer heterogeneities, leading to plausible conceptual models. Nevertheless, the diagnostic plot is insufficient and must be accompanied by further modelling because of the nonuniqueness of the drawdown log-derivative signal. The proposed approach is applied to an alluvial plain in France, known to be complex because the deposition processes change over time, resulting in channel belts limited by low-permeability deposits in the floodplain or three-dimensional (3D) interconnected structures. Six analytical models were used to simulate drawdown and its derivatives during a three-day transient pumping test. The diagnostic performed on the pumping well showed that four conceptual models, with highly contrasted hydrodynamic behaviours, may correspond to the diagnostic. The joint use of pumping-well and observation-well data allowed the only appropriate model to be identified—a dual-permeability model characterizing a multilayer aquifer. The conceptual model matched the geological observations in boreholes and corroborates the fluvial sequence stratigraphy of the alluvial plain. The pumping test used here is a tool to explore the 3D architecture of the fluvial reservoir at the scale of the depositional sequence in the floodplain.

Analyzing the Impacts of Meshing and Grid Alignment in Dual-Porosity Dual-Permeability Upscaling

SummaryThe discrete fracture network (DFN) model is widely used to simulate and represent the complex fractures occurring over multiple length scales. However, computational constraints often necessitate that these DFN models be upscaled into a dual-porosity dual-permeability (DPDK) model and discretized over a corner-point grid system, which is still commonly implemented in many commercial simulation packages. Many analytical upscaling techniques are applicable, provided that the fracture density is high, but this condition generally does not hold in most unconventional reservoir settings. A particular undesirable outcome is that connectivity between neighboring fracture cells could be erroneously removed if the fracture plane connecting the two cells is not aligned along the meshing direction.In this work, we propose a novel scheme to detect such misalignments and to adjust the DPDK fracture parameters locally, such that the proper fracture connectivity can be restored. A search subroutine is implemented to identify any diagonally adjacent cells of which the connectivity has been erroneously removed during the upscaling step. A correction scheme is implemented to facilitate a local adjustment to the shape factors in the vicinity of these two cells while ensuring the local fracture intensity remains unaffected. The results are assessed in terms of the stimulated reservoir volume calculations, and the sensitivity to fracture intensity is analyzed.The method is tested on a set of tight oil models constructed based on the Bakken Formation. Simulation results of the corrected, upscaled models are closer to those of DFN simulations. There is a noticeable improvement in the production after restoring the connectivity between those previously disconnected cells. The difference is most significant in cases with medium DFN density, where more fracture cells become disconnected after upscaling (this is also when most analytical upscaling techniques are no longer valid); in some 2D cases, up to a 22% difference in cumulative production is recorded. Ignoring the impacts of mesh discretization could result in an unintended reduction in the simulated fracture connectivity and a considerable underestimation of the cumulative production.

Fault-related fracture modeling in a pre-salt lacustrine carbonate reservoir from Santos Basin, offshore Brazil: Predicting preferential fluid flow paths using 3D geological and flow simulation models

The authors propose an integrated workflow from seismic to flow simulation to predict sub seismic and inter-well fracture distribution. This methodology provides insights in order to fulfill a knowledge gap in reservoir 3D modeling of naturally fractured carbonates applied in the industry. The workflow includes interpretation of borehole image logs, 3D seismic, geophysical and geomechanical attributes, and calibration with dynamic data. The main natural fracture parameters analyzed for the case study are direction, dip, and fracture intensity. The studied area is a naturally fractured Aptian lacustrine carbonate reservoir within the Santos Basin, offshore Brazil. The isolated platform developed over a series of elongated NE-SW horsts structures. The main seismic scale structures in the reservoir are NE-SW trending faults that show normal displacement, defining en échelon relay ramps that contain NW-SE sub seismic faults and diffuse fracture swarms. The damage zones that surround these main faults define continuous fracture corridors intercepted by oblique sub-seismic faults in relay-ramp zones. Structural analysis showed that fracture intensities are higher at the north domain in the Barra Velha Formation. The fractures were simulated stochastically using a discrete fracture network (DFN), generating a dual porosity and dual permeability model (DPDK) for the flow simulation resulting in a suitable model configuration for the history match.

Application of an Accurate and Efficient Modeling Approach to a Multiscale Fractured Reservoir in South China Sea

Carbonate reservoirs in the South China Sea mostly contain natural fractures with various length scales and different intensities, which causes great challenges in efficient reservoir modeling and flow simulation. Existing efforts based on dual-porosity and dual-permeability models could not reflect the characteristics of production data in certain wells. To accurately and efficiently characterize multiscale fractures, a hybrid fracture characterization method is proposed. Firstly, fractures are divided into two types according to the geometrical size and interpretation approach. Then, small-scale fractures, characterized mainly by image log interpretations, are modeled by the traditional dual-porosity/dual-permeability (DP) method. And large-scale fractures, which are characterized by seismic interpretations and dominate the flow regime, are modeled by the embedded discrete fracture method (EDFM) to achieve both accuracy and efficiency. Lastly, transmissibilities among these three types of grid mediums are calculated to generate the hybrid DP+EDFM model for flow simulation. The proposed approach is applied to a carbonate, fractured reservoir in the South China Sea. The overall procedure is fast and reliable, and water cut matches of both field and specific wells are dramatically improved. Comparing the simulation results with the conventional DP model, the proposed approach yields much more accurate predictions on rapid water breakthrough and high water cut in fractured reservoirs.

Model-Based Assessment of Groundwater Contamination with PFOS due to Fire-Training Activities

Aqueous film-forming foams (AFFFs) containing perfluoro-octane sulfonate (PFOS) were commonly used in fire trainings until the awareness of their toxicity started to increase in the 2000s. Our objective was to build a modeling framework for estimating groundwater pollution with PFOS, utilizing dual-permeability modeling still novel for groundwater studies. The framework was applied to an existing contamination site. According to the results, only 27% of PFOS released from the fire-training area reached the aquifer. Adsorption to unburnt fuels and removal via oil separation wells before discharging to the aquifer can substantially reduce the PFOS contamination of groundwater. Despite this, the PFOS concentration in a groundwater intake area 1.9 km from the pollutant source was predicted to exceed the limits set for drinking water, in contrast to earlier predictions based solely on monitoring. The study demonstrates the importance of modeling for groundwater management as the data on AFFF usage and composition, and on soil and groundwater contamination with perfluorinated compounds and co-pollutants typically are limited in terms of the spatial and temporal scale of contamination.

Conception the Fluid Flow Behavior within Oil Reservoir Rock by Using Computed Tomography (CT) Scan

The behavior of fluid flow has been studied during the different flow media over the past decades. In addition, the behavior of the flow of fluid through porous media has garnered much research interest. This paper sheds light on fissured rocks of oil reservoir media (as one of the porous media domain), and the effect of these fissured on fluid flow. In this article, the Finite Volume Method (FVM) has been used to visualize the behavior of single-phase fluid flow in an actual core according to the dualporosity dual permeability model. The study was conducted in two parts, the first was the image processing for one of the real oil reservoir fractured rock images, where the image was processed and simulated by ANSYSCFX software, and the results showed a complete visualizing of the fluid behavior during this domain. As for the other side, a simulation of a real reservoir rock belonging to the Al-Nour field in Iraq / Misan was made. The X-ray Computed Tomography (CT) scan has been used to convert the real fractured core to a dynamic domain. ANSYS-CFX program has been used and the results illustrated the pressure counter, the velocity counter, the velocity streamline, and the velocity vectors for the studied model in three dimensions. A comparison was made between the productivity index for fractured and non-fractured rock and the results explained that the presence of fracture can improve the productivity index to about 5.74%.

Novel Mathematical Model for Transient Pressure Analysis of Multifractured Horizontal Wells in Naturally Fractured Oil Reservoirs.

Multifractured horizontal wells have gained significant attention within the petroleum industry for commercial development. Despite considerable developments of transient pressure analysis or flow rate behaviors for horizontal wells in naturally fractured reservoirs, some significant problems are yet to be resolved, including high heterogeneity of reservoirs, pressure sensitivity of hydraulic fractures, and non-Darcy flow effect, which may occur during the production life. This paper presents a more pragmatic mathematical model for multifractured horizontal wells in naturally fractured reservoirs based on the fractal system, the theory of permeability modulus, and the time-fractional calculus correspondingly as an extension of the classic trilinear flow model. This new model comprises three modules: high heterogeneity of the reservoir based on the fractal system, the permeability modulus typically showing the pressure sensitivity of hydraulic fractures, and the anomalous diffusion describing non-Darcy flow turbulence. This investigation evaluates a trilinear dual-permeability dual-porosity flow model, with the dual-porosity model for the unstimulated outer reservoir flow region, the dual-permeability model for the stimulated inner reservoir flow region, and the permeability modulus for the flow region of hydraulic fractures. The comprehensive sensitivity analysis conducted indicates how the key parameters, such as fractal dimension, hydraulic fracture permeability modulus and conductivity, interporosity flow coefficient, storativity ratio, etc., affect the transient pressure behaviors, along with their reasons for the change in behavior. Application to a field case study further demonstrates the validity of the mathematical model, and the results presented may play a guiding role in well test interpretation.

Numerical Well Test Analysis of Condensate Dropout Effects in Dual-Permeability Model of Naturally Fractured Gas Condensate Reservoirs: Case Studies in the South of Iran

Naturally fractured reservoirs (NFR) represent an important percentage of worldwide hydrocarbon reserves and production. The performance of naturally fractured gas condensate reservoirs would be more complicated regarding both rock and fluid effects. In contrast to the dual-porosity model, dual-porosity/dual-permeability (dual-permeability) model is considered as a modified model, in which flow to the wellbore occurs through both matrix and fracture systems. Fluid flow in gas condensate reservoirs usually demonstrates intricate flow behavior when the flowing bottom-hole pressure falls below the dew point. Accordingly, different regions with different characteristics are formed within the reservoir. These regions can be recognized by pressure transient analysis. Consequently, distinguishing between reservoir effects and fluid effects is challenging in these specific reservoirs and needs numerical simulation. The main objective of this paper is to examine the effect of condensate banking on the pressure behavior of lean and rich gas condensate NFRs through a simulation approach. Subsequently, evaluation of early-time characteristics of the pressure transient data is provided through a single well compositional simulation model. Then, drawdown, buildup, and multirate tests are conducted to establish the condition in which the flowing bottom-hole pressure drops below the dew point causing retrograde condensation. The simulation results are confirmed through well test analysis in both Iranian naturally fractured rich and lean gas condensate fields. Interpretations of simulation analysis revealed that the richer gas is more prone to condensation. When the pressure drops below the dew point, the pressure derivative curves in the rich gas system encounter a more shift to the right, and the trough becomes more pronounced as compared to the lean one.

The method of fundamental solutions for the elastic wave scattering in a double-porosity dual-permeability medium

For materials that have a matrix porosity at the microscopic scale, and an interconnecting fracture system at the mesoscopic scale, the double-porosity dual-permeability model provides a better prediction of seismic wave attenuation than the single porosity model, due to the flow exchange mechanism between these different size pores. The current work offers for the first time a numerical solution tool based on the method of fundamental solutions for problems of 3-D wave scattering and dynamic stress concentration around scatterers, such as cavities and embedded inhomogeneous inclusions, in an infinite double-porosity dual-permeability medium. The method of fundamental solutions is based on the spherical wave potentials representing three compressional waves and one shear wave. The accuracy and stability of the method are tested against other available results, and are demonstrated to be excellent. Wave scattering and dynamic stress concentration problems due to spherical cavity and poroelastic inclusion are then investigated for incident plane P1 and SV waves in the frequency domain. The research shows that the seismic responses are sensitive to the incident frequency, the boundary drainage condition, and material properties such as porosity.

Determination of Unsaturated Hydraulic Properties of Seepage Flow Process in Municipal Solid Waste

The unsaturated hydraulic characteristics of waste soil are an essential basis for predicting and evaluating leachate migration and distribution in landfills. The saturated water content and permeability coefficient were measured, and a multi-step drainage monitoring experiment was conducted indoors at different dry densities, particle sizes, and degradation ages. Single and dual permeability models were adopted to determine the unsaturated hydraulic characteristic parameters of waste. Results show that dry density and particle size are the key factors affecting the saturated water content and permeability of waste. A single degradation age has little effect on it. Respectively, the saturated water content has a linear relationship with dry density, and permeability has an exponential relationship with dry density under limited experimental data. The overflow numerical inversion method can accurately obtain the unsaturated hydraulic characteristic parameters of wastes and summarizes the values of the unsaturated hydraulic characteristic parameters of wastes with different attributes in the literature and the results of this study. The dual-permeability model performed significantly better than the single-permeability model for water movement, suggesting that a dual-domain description is required for water flow in landfills.

Numerical study of water inflow into tunnels in stratified rock masses with a dual permeability model

Stratification planes form an anisotropic structural setting in the stratified rock mass, and strongly influence the water inflow into tunnels. However in the numerical simulation studies, the equivalent porous model pays little regard for the anisotropic structural setting and the discrete fracture network model costs too much computing power. In this study, a dual permeability model is utilized to calculate the water inflow into tunnels and the anisotropic flow behavior with finite element numerical simulations. The dual permeability model takes the stratification planes into artery fractures, and consider the rock matrix with other fractures as an equivalent isotropic medium. Parameters including the piezometric head above the tunnel center, the artery fracture angle, and the artery fracture spacing are studied and discussed. It is shown that both the piezometric head above the tunnel center and the artery fracture spacing affect the water inflow a lot. In this research, the influence of the artery fracture spacing on water inflow is larger than that of the piezometric head above the tunnel center when the artery fracture spacing 4.62 m. What is more, the artery fracture angle affects the water inflow slightly but it controls the flow direction. The water inflow case of the Huangjiagou Tunnel is used to verify the proposed model. The results show that the dual permeability model could give good predictions to the Huangjiagou Tunnel and describe the anisotropic flow behavior in stratified rock mass tunnels.

Pore-scale dual-porosity and dual-permeability modeling in an exposed multi-facies porous carbonate reservoir

Fracture networks in porous carbonates can control, assist, or even contribute negatively to reservoir quality. In scenarios where fractures and matrix pore systems are of similar importance, a dual-porosity/permeability (DP/P) modeling approach is necessary or at least recommendable for the reservoir characterization. These workflows are well established at the reservoir scale, however at the microscale, the interaction between fractures and porous matrix needs to be further investigated.The aim of this work is to assess the contribution of meter-scale fractures (macrofractures) to the porosity and permeability in a porous carbonate reservoir analogue at the microscale. To reach this objective, we created DP/P models at the microscale through the integration of two different methods of 3D imaging such as, high-resolution synchrotron X-ray microtomography (SR micro-CT) and Structure from Motion (SfM) photogrammetry. Quantitative analyses of pristine rock and DP/P models were performed to evaluate the contribution of macrofracture segments to the porosity and connectivity of the pore network. These results were integrated with single-phase flow simulations for calculating permeability values. Different scenarios were modeled in order to systematically evaluate the control exerted by fracture roughness parameters (i.e., asperity height distribution and fractal dimension) on porosity and permeability in various lithofacies.The key analyzed samples come from the Roman Valley quarry located at the Majella Mountain (central Italy), which has been widely investigated due to the presence of consistent bitumen impregnations distributed in pervious medium-to-coarse grainstones and along two main fault zones. The results of this study demonstrate the utility of obtaining DP/P microscale models as complementary approach to explain the hydrocarbon distribution in fractured multi-facies porous carbonates. We document the potential of macrofracture segments to provide neo-connected porosity by linking up adjacent isolated or partially isolated matrix pore networks in impervious carbonate rocks. In pervious carbonate lithofacies, fault-related macrofractures can enhance permeability and contribute to bitumen migration and distribution, whereas the increment of storage capacity is limited since these rocks are already fully connected. In the case of impervious carbonate lithofacies, results indicate that the actual contribution of neo-connected pores to fluid transport is limited, which agrees with outcrop observations.

Smart Proxy Modeling of a Fractured Reservoir Model for Production Optimization: Implementation of Metaheuristic Algorithm and Probabilistic Application

Numerical reservoir simulation has been recognized as one of the most frequently used aids in reservoir management. Despite having high calculability performance, it presents an acute shortcoming, namely the long computational time induced by the complexities of reservoir models. This situation applies aptly in the modeling of fractured reservoirs because these reservoirs are strongly heterogeneous. Therefore, the domains of artificial intelligence and machine learning (ML) were used to alleviate this computational challenge by creating a new class of reservoir modeling, namely smart proxy modeling (SPM). SPM is a ML approach that requires a spatio-temporal database extracted from the numerical simulation to be built. In this study, we demonstrate the procedures of SPM based on a synthetic fractured reservoir model, which is a representation of dual-porosity dual-permeability model. The applied ML technique for SPM is artificial neural network. We then present the application of the smart proxies in production optimization to illustrate its practicality. Apart from applying the backpropagation algorithms, we implemented particle swarm optimization (PSO), which is one of the metaheuristic algorithms, to build the SPM. We also propose an additional procedure in SPM by integrating the probabilistic application to examine the overall performance of the smart proxies. In this work, we inferred that the PSO had a higher chance to improve the reliability of smart proxies with excellent training results and predictive performance compared with the considered backpropagation approaches.