Recent Submissions

  • Technical Evaluation of Conformance Improvement Technology with Anionic Surfactant-Stabilized Microemulsions in Porous Media

    Pal, Nilanjan; Alzahid, Yara; AlSofi, Abdulkareem; Ali, Muhammad; Zhang, Xuan; Hoteit, Hussein (Elsevier BV, 2022-07-22) [Preprint]
    The application of microemulsion-assisted conformance improvement technology (ME-CIT) has the potential to significantly reduce the water-to-oil production ratio and operational costs during oilfield stimulation/production. However, the efficacy of this process is dependent on workflow planning and validation from an experimental viewpoint. The current article aims to develop a functional ME-CIT route and propose a viable microemulsion fluid system, based on this approach. Initially, the liquid-liquid phase behavior was classified using the ternary phase diagram. A phase envelope was identified to separate the multi-phase (2- and 3-phase) region from the uneconomical one-phase region. ME droplets were characterized via dynamic light scattering tests to understand the aggregation behavior of micelles and the extent of salt on coalescence. Relative phase volume investigations revealed the existence of Winsor I at low salinities upto 20,000 ppm total dissolved salts (TDS) content. The first phase transition occurred at 25,000 ppm TDS to exhibit a Winsor III system and continued till the salinity reached 40,000 ppm. At 50,000 ppm, the Winsor III changed into Winsor II phase behavior. In addition, the steady-state shear viscosity of ME fluids does not alter markedly with time, irrespective of their salt content. Viscosity plots show the pseudoplastic or shear-thinning flow behavior of MEs. The ME rheology can be discussed in terms of two opposing interaction effects: electro-shielding and micelle deformation. The viscosity is, therefore, a function of salinity-induced phase behavior on a macroscopic level and micelle morphology on a microscopic scale. Viscosity versus salinity plots at 7.34 s-1 depicts a unique ‘M’ shape with increasing salinity, characterized by an initial increase, followed by a decrease, then an increase, and finally a near-constant viscosity. Flow displacement tests of optimized ME slug illustrated a favorable pressure drop response after water-flood, which is accompanied by a significant decrease in water cut. Based on the physicochemical evaluation and subsequent displacement testing, the proposed laboratory workflow model contributes to a potentially useful method of optimizing and designing surfactant-based ME fluid systems for conformance improvement.
  • Red sea evaporites: Formation, creep and dissolution

    Smith, Joshua E.; Santamarina, Carlos (Earth-Science Reviews, Elsevier BV, 2022-07-21) [Article]
    Evaporite deposition and seafloor spreading are two salient geological processes in the geological history of the Red Sea. We piece together the available evidence about rift evolution and evaporite formation to constrain the deposition history, analyze creep, and advance a plausible explanation for the preservation of these soluble formations. At the end of evaporite deposition before the Indian Ocean flooded the Red Sea through the Bab al-Mandab's strait, the salt thickness must have exceeded ~1.5 times the current thickness. Reported plate rotation, rift rates and the presence of a salt suture zone in the central Red Sea allow us to estimate an effective large-scale viscosity of 1018 Pa·s. Thinned salt along the southern Red Sea flows up to 5 mm/yr, creep cannot keep up with seafloor spreading and oceanic crust remains exposed. Vast alluvial fans and carbonate platforms cause salt withdrawal; corresponding seafloor settlement rates can exceed ~10 mm/yr and overtake coral reef production. Salt dissolution leaves behind a residual sediment cap made of insoluble minerals that gradually retards further dissolution, i.e., self-armoring. New experimental evidence and the numerical solution of diffusion with a moving boundary show that self-armoring by selective dissolution controls early evaporite dissolution while background sedimentation dominates sediment accumulation over long time scales. Armoring-delayed evaporite dissolution prevents the formation of a vast regional brine pool.
  • HATCHFRAC: A fast open-source DFN modeling software

    Zhu, Weiwei; Khirevich, Siarhei; Patzek, Tadeusz (Computers and Geotechnics, Elsevier BV, 2022-07-19) [Article]
    This paper introduces a comprehensive C++ software package, HATCHFRAC, for stochastic modeling of fracture networks in two and three dimensions. The inverse cumulative distribution function (CDF) and acceptance–rejection methods are applied to generate random variables from the stochastic distributions commonly used in discrete fracture network (DFN) modeling. The multilayer perceptron (MLP) machine learning approach, combined with the inverse CDF method, generates random variables following any sampling distribution. We extend the Newman–Ziff algorithm to determine clusters in the fracture networks and make the code faster. When combined with the block method, the coding efficiency is further enhanced. The software generates the T-type fracture intersections in the network by simulating a fracture growth process, which can be used in applications involving fracture growth or incorporating geomechanics. Three applications of HATCHFRAC are introduced to demonstrate the versatility of our software: percolation analysis, fracture intensity analysis, and flow and connectivity analysis.
  • Estimation of Mercury Injection Capillary Pressure (MICP) from the Nuclear Magnetic Resonance (NMR) exponential decay with the Machine Learning (ML) Neural Network (NN) approach

    Ugolkov, Evgeny A. (2022-07-09) [Thesis]
    Advisor: Hoteit, Hussein
    Committee members: Santamarina, Carlos; Ahmed, Shehab
    Information about the capillary pressure has a wide range of applications in the petroleum industry, such as an estimation of irreducible water saturation, calculation of formation absolute permeability, determination of hydrocarbon-water contact and the thickness of the transition zone, evaluation of the seal capacity, and an estimation of relative permeability. All the listed parameters in the combination with petrophysical features, pressures, and fluid properties allow us to evaluate the economic viability of the well or the field overall. For this reason, capillary pressure curves are of great importance for petroleum engineers working on any stage of the field development: starting from exploration and finishing with production stages. Nowadays, capillary pressure experiments are provided either in the lab on the plugs of the rocks, either in the well on the certain stop points with the formation tester tools on the wire or tubes. Core extraction and formation testing are both laborious, expensive, and complicated processes since the newly-drilled well remain in the risky uncased condition during these operations, and for this reason, usually the listed works are provided in the exploration wells only. Afterward, the properties obtained from the exploration wells are assumed to be the same for the extraction or any other kinds of wells. Therefore, these days petroleum engineers have limited access to the capillary pressure curves: the modern tests are provided on the limited points of formation in the limited number of wells. An extension of capillary pressure measurements in the continuous mode for every well will dramatically expand the abilities of modern formation evaluation and significantly improve the field operation management by reducing the degree of uncertainty in the decision-making processes. This work is the first step toward continuous capillary pressure evaluation. Here we describe the procedure of finding the correlation between the results of the lab Nuclear Magnetic Resonance (NMR) experiment and lab Mercury Injection Capillary Pressure (MICP) measurements. Both experiments were provided on the 9 core plugs of the sandstone. Afterward, a Machine Learning (ML) algorithm was applied to generate additional samples of the porous media with different petrophysical properties representing the variations of the real cores of available sandstones. Overall, 405 additional digital rock models were generated. Thereafter, the digital simulations of MICP and NMR experiments were provided on the generated database of digital rocks. All the simulations were corrected for limited resolution of the CT scan. Based on the created database of experiments, we implemented a ML algorithm that found a correlation between the NMR echo data and MICP capillary pressure curves. Obtained correlation allows to calculate capillary pressure curve from the NMR echo data. Since NMR logging may be implemented in every well in the continuous mode, an extension of the created technique provides an opportunity for continuous estimation of capillary pressure for the whole logging interval. This extension is planned as future work.
  • Fluid-Driven Instabilities in Granular Media: From Viscous Fingering and Dissolution Wormholes to Desiccation Cracks and Ice Lenses

    Liu, Qi; Santamarina, Carlos (Frontiers in Mechanical Engineering, Frontiers Media SA, 2022-07-08) [Article]
    Single and multi-phase fluids fill the pore space in sediments; phases may include gases (air, CH4, CO2, H2, and NH3), liquids (aqueous solutions or organic compounds), and even ice and hydrates. Fluids can experience instabilities within the pore space or trigger instabilities in the granular skeleton. Then, we divided fluid-driven instabilities in granular media into two categories. Fluid instabilities at constant fabric take place within the pore space without affecting the granular skeleton; these can result from hysteresis in contact angle and interfacial tension (aggravated in particle-laden flow), fluid compressibility, changes in pore geometry along the flow direction, and contrasting viscosity among immiscible fluids. More intricate fluid instabilities with fabric changes take place when fluids affect the granular skeleton, thus the evolving local effective stress field. We considered several cases: 1) open-mode discontinuities driven by drag forces, i.e., hydraulic fracture; 2) grain-displacive invasion of immiscible fluids, such as desiccation cracks, ice and hydrate lenses, gas and oil-driven openings, and capillary collapse; 3) hydro-chemo-mechanically coupled instabilities triggered by mineral dissolution during the injection of reactive fluids, from wormholes to shear band formation; and 4) instabilities associated with particle transport (backward piping erosion), thermal changes (thermo-hydraulic fractures), and changes in electrical interparticle interaction (osmotic-hydraulic fractures and contractive openings). In all cases, we seek to identify the pore and particle-scale positive feedback mechanisms that amplify initial perturbations and to identify the governing dimensionless ratios that define the stable and unstable domains. A [N/m] Contact line adhesion.
  • A robust fully Mixed Finite Element model for flow and transport in unsaturated fractured porous media

    Younes, Anis; Hoteit, Hussein; Helmig, Rainer; Fahs, Marwan (Advances in Water Resources, Elsevier BV, 2022-06-25) [Article]
    A fully mixed finite element (MFE) model is developed for nonlinear flow and transport in unsaturated fractured porous media with matrix-fracture and fracture-fracture fluid and mass exchanges. The model is based on the discrete fracture matrix (DFM) approach and assumes cross-flow equilibrium in the fractures. The MFE method is employed for the spatial discretization of both flow and transport on the 2D-matrix elements as well as on the 1D-fracture elements. An upwind scheme is employed to avoid unphysical oscillations in the case of advection dominant transport. The temporal discretization is performed using high-order time integration methods and efficient automatic time-stepping schemes via the MOL. Two test problems dealing with flow and mass transport in saturated and unsaturated fractured porous media are simulated to show the validity of the new model by comparison against (i) a 1D-2D Comsol finite element model and (ii) a 2D-2D Discontinuous Galerkin (DG) model where both fractures and matrix continua are discretized with small 2D mesh elements. The robustness and efficiency of the developed 1D-2D MFE model are then investigated for a challenging problem dealing with infiltration of contaminated water into an initially dry soil involving a fracture network. The new model yields stable results for advection-dominated and advection-dispersion transport configurations. Further, the results of the 1D-2D MFE model are in very good agreement with those of the 2D-2D DG model for both configurations. The simulation of infiltration of contaminated water into a dry fractured soil shows that the 1D-2D MFE model is within 15 times more efficient than the 2D-2D DG model, which confirms the high benefit of using robust and efficient DFM models for the simulation of flow and transport in fractured porous media.
  • Thermodynamic modeling of hydrogen–water systems with gas impurity at various conditions using cubic and PC-SAFT equations of state

    Alanazi, Amer; Bawazeer, Saleh; Ali, Muhammad; Keshavarz, Alireza; Hoteit, Hussein (Energy Conversion and Management: X, Elsevier BV, 2022-06-22) [Article]
    Hydrogen (H2) has emerged as a viable solution for energy storage of renewable sources, supplying off-seasonal demand. Hydrogen contamination due to undesired mixing with other fluids during operations is a significant problem. Water contamination is a regular occurrence; therefore, an accurate prediction of H2-water thermodynamics is crucial for the design of efficient storage and water removal processes. In thermodynamic modeling, the Peng–Robinson (PR) and Soave Redlich–Kwong (SRK) equations of state (EoSs) are widely applied. However, both EoSs fail to predict the vapor-liquid equilibrium (VLE) accurately for H2-blend mixtures with or without fine-tuning binary interaction parameters due to the polarity of the components. This work investigates the accuracy of two advanced EoSs: the Schwartzentruber and Renon modified Redlich–Kwong cubic EoS (SR-RK) and perturbed-chain statistical associating fluid theory (SAFT) in predicting VLE and solubility properties of H2 and water. The SR-RK involves the introduction of polar parameters and a volume translation term. The proposed workflow is based on optimizing the binary interaction coefficients using regression against experimental data that cover a wide range of pressure (0.34 to 101.23 MPa), temperature (273.2 to 588.7 K), and H2 mole fraction (0.0004 to 0.9670) values. A flash liberation model is developed to calculate the H2 solubility and water vaporization at different temperature and pressure conditions. The model captures the influence of H2-gas (CO2) impurity on VLE. The results agreed well with the experimental data, demonstrating the model's capability of predicting the VLE of hydrogen-water mixtures for a broad range of pressures and temperatures. Optimized coefficients of binary interaction parameters for both EoSs are provided. The sensitivity analysis indicates an increase in H2 solubility with temperature and pressure and a decrease in water vaporization. Moreover, the work demonstrates the capability of SR-RK in modeling the influence of gas impurity (i.e., H2–CO2 mixture) on the H2 solubility and water vaporization, indicating a significant influence over a wide range of H2–CO2 mixtures. Increasing the CO2 ratio from 20% to 80% exhibited almost the opposite behavior of H2 solubility compared to the pure hydrogen feed solubility. Finally, the work emphasizes the critical selection of proper EoSs for calculating thermodynamic properties and the solubility of gaseous H2 and water vaporization for the efficient design of H2 storage and fuel cells.
  • Modeling lost-circulation in natural fractures using semi-analytical solutions and type-curves

    Albattat, Rami; AlSinan, Marwa; Kwak, Hyung; Hoteit, Hussein (Journal of Petroleum Science and Engineering, Elsevier BV, 2022-06-16) [Article]
    Drilling is a requisite operation for many industries to reach a targeted subsurface zone. During operations, various issues and challenges are encountered, particularly drilling fluid loss. Loss of circulation is a common problem that often causes interruptions to the drilling process and a reduction in efficiency. Such incidents usually occur when the drilled wellbore encounters a high permeable formation such as faults or fractures, leading to total or partial leakage of the drilling fluids. In this work, a semi-analytical solution and mud type-curves (MTC) are proposed to offer a quick and accurate diagnostic model to assess the lost-circulation of Herschel-Bulkley fluids in fractured media. Based on the observed transient pressure and mud-loss trends, the model can estimate the effective fracture conductivity, the time-dependent cumulative mud-loss volume, and the leakage period. The behavior of lost-circulation into fractured formation can be quickly evaluated, at the drilling site, to perform useful diagnostics, such as the rate of fluid leakage, and the associated effective fracture hydraulic properties. Further, derivative-based mud-type-curves (DMTC) are developed to quantify the leakage of drilling fluid flow into fractures. The developed model is applied for non-Newtonian fluids exhibiting yield-power-law (YPL), including shear thickening and thinning, and Bingham plastic fluids. Proposing rigorous dimensionless groups generates the dual type-curves, MTC and DMTC, which offer superior predictivity compared to traditional methods. Both type-curve sets are used in a dual trend matching, which significantly reduces the non-uniqueness issue that is typically encountered in type-curves. Usage of numerical simulations is implemented based on finite elements to verify the accuracy of the proposed solution. Data for lost circulation from several field cases are presented to demonstrate the applicability of the proposed method. The semi-analytical solver, combined with Monte Carlo simulations, is then applied to assess the sensitivity and uncertainty of various fluid and subsurface parameters, including the hydraulic property of the fracture and the probabilistic prediction of the rate of mud leakage into the formation. The proposed approach is based on a robust semi-analytical solution and type-curves to model the flow behavior of Herschel-Bulkley fluids into fractured reservoirs, which can serve as a quick diagnostic tool to evaluate lost-circulation in drilling operations.
  • A Geomechanical Model for Gas Hydrate Bearing Sediments Incorporating High Dilatancy, Temperature, and Rate Effects

    Zhou, Bohan; Sanchez, Marcelo; Oldecop, Luciano; Santamarina, Carlos (Energies, MDPI AG, 2022-06-10) [Article]
    The geomechanical behavior of methane hydrate bearing sediments (MHBS) is influenced by many factors, including temperature, fluid pressure, hydrate saturation, stress level, and strain rate. The paper presents a visco-elastoplastic constitutive model for MHBS based on an elastoplastic model that incorporates the effect of hydrate saturation, stress history, and hydrate morphology on hydrate sediment response. The upgraded model is able to account for additional critical features of MHBS behavior, such as, high-dilatancy, temperature, and rate effects. The main components and the mathematical formulation of the new constitutive model are described in detail. The upgraded model is validated using published triaxial tests involving MHBS. The model agrees overly well with the experimental observations and is able to capture the main features associated with the behavior of MHBS.
  • Evaluation of Rwanda’s Energy Resources

    Favero Bolson, Natanael; Patzek, Tadeusz (Sustainability, MDPI AG, 2022-05-25) [Article]
    Energy flows in a fertile environment drive societal development and progress. To develop a country sustainably, striking balance between environmental management, natural resource use, and energy generation is a must. However, developing a country with limited access to energy and critical levels of environmental depletion is challenging. This description fits Rwanda, which faces a dual crisis of energy supply shortages and environment depletion. Overpopulation is driving urban and agricultural expansion which in turn unbalance biomass demand to supply the growing energy needs and exacerbate environmental damage. Just when urgent actions must be taken to overcome this current debacle, political aspirations seek to turn Rwanda into a middle- and subsequently high-income country. From our analysis, the available energy resources can only maintain current population in Rwanda as a low-income country. To become an average middle-income country, Rwanda needs an equivalent of 3 Mtoe /yr (≈20 Mbbl /yr) of oil imports, and must install a nominal capacity of 90 GW of solar photovoltaics (PV). For a high-income country, it is necessary to obtain an extra power input of 11.4Mtoe /yr (≈77 Mbbl /yr) of oil imports and to install a nominal capacity of 400 GW of solar PV. Comparing current power generation capacity in Rwanda against the extra power needed to achieve the middle-income and high-income status indicates a mismatch between available resources and developmental goals.
  • Hydrothermal metalliferous sediments in the Red Sea: Characterization and properties

    Modenesi, M. Clara; Santamarina, Carlos (Engineering Geology, Elsevier BV, 2022-05-19) [Article]
    Sediment accumulations within the Red Sea central deeps have unique genesis and properties. We piece together available information to understand their geological setting and formation history, and conduct an extensive sediment characterization study to assess their geotechnical properties in order to anticipate engineering/mining implications. The various sediment columns reflect slow-rate background sedimentation (biogenic and detrital particles – Valdivia deep) and hydrothermal metalliferous sediments that nucleate and grow within the overlying brine pools (primarily in the Atlantis II, as well as in the Wando deep, and to a lesser extent in Discovery deep). All sediments are fine-grained silt and clay-size particles; smaller particles tend to have higher specific gravity and define the metalliferous content. Hydrothermal sediments exhibit extreme properties when compared to sediments worldwide: they have uncharacteristically large maximum void ratio and compressibility, and their self-compaction is very different from background Red Sea sediments. Their unique self-compaction trends have a strong effect on remote acoustic characterization and sampling, and must be carefully accounted for during field studies and resource assessment. Three distinct properties of hydrothermal metalliferous sediments are relevant for separation and enrichment: high specific surface area, high specific gravity, and ferromagnetic signature. Small grains and low-density flocs have low terminal Stokes' velocities and their residency times may be extended in convective stratified brine pools; this observation affects the environmental analysis of mining operations and tailings disposal.
  • Rapid bentonite-cement-oil hydration: Implications to fluid loss control

    Hafez, Ahmed; Liu, Qi; Finkbeiner, Thomas; Moellendick, Timothy E.; Santamarina, Carlos (Journal of Petroleum Science and Engineering, Elsevier BV, 2022-05-18) [Article]
    Conventional particulate additives fail to control drilling fluid losses into large-aperture fractures. The separate injections of a bentonite-cement-oil suspension and water can cause rapid hydration, swelling and hardening to effectively plug fractures. This experimental study investigates underlying processes and implications in view of optimal fluid flow control in fractures. Results identify several concurrent hydro-chemo-mechanical coupled processes: capillarity-driven water invasion; cement hydration and the release of Ca2+ and OH− ions; bentonite contractive aggregation and increased hydrophilicity; enlarged inter-aggregate pores that facilitate fluid flow; oil pressurization leading to the formation of oil-filled opening mode discontinuities that facilitate oil escape towards free draining boundaries, and calcium silicate hydrate formation and growth resulting in hardening. The hydration of bentonite-cement-oil suspensions proceeds several times faster than in bentonite-oil suspensions. The optimal mixture should balance competing requirements between flowability, water invasion speed, swelling pressure and plug strength.
  • Adsorption of Polar Species at Crude Oil–Water Interfaces: the Chemoelastic Behavior

    Saad, Ahmed Mohamed; Aime, Stefano; Chandra Mahavadi, Sharath; Song, Yi-Qiao; Yutkin, Maxim; Weitz, David; Patzek, Tadeusz (Langmuir, American Chemical Society (ACS), 2022-05-17) [Article]
    We investigate the formation and properties of crude oil/water interfacial films. The time evolution of interfacial tension suggests the presence of short and long timescale processes reflecting the competition between different populations of surface-active molecules. We measure both the time-dependent shear and extensional interfacial rheology moduli. Late-time interface rheology is dominated by elasticity, which results in visible wrinkles on the crude oil drop surface upon interface disturbance. We also find that the chemical composition of the interfacial films is affected by the composition of the aqueous phase that it has contacted. For example, sulfate ions promote films enriched with carboxylic groups and condensed aromatics. Finally, we perform solution exchange experiments and monitor the late-time film composition upon the exchange. We detect the film composition change upon replacing chloride solutions with sulfate-enriched ones. To the best of our knowledge, we are the first to report the composition alteration of aged crude oil films. This finding might foreshadow an essential crude oil recovery mechanism.
  • Late Pleistocene to Holocene Architecture of a Land-attached Carbonate Platform Lagoon in the African-Arabian Desert Belt (Al Wajh platform, N Red Sea, Saudi Arabia).

    Putri, Indah; Petrovic, Alexander; Sifontes, Rangelys; Vahrenkamp, Volker (Copernicus GmbH, 2022-05-12) [Presentation]
    Investigation of carbonate platform architecture is a crucial element to understanding the evolution of a platform. Extensive studies have been done on the architectures of various modern carbonate platforms. However, compared to humid climates, detailed studies in arid climates are rare, although many ancient carbonate reservoirs are developed under these conditions. This study investigates the Late Pleistocene architecture of the land-attached Al Wajh carbonate platform in the Northeastern Red Sea, Saudi Arabia. The platform is enclosed by a coral reef belt and characterized by a large lagoon (1,100 km2). The lagoon reaches 43 meters in depth and hosts more than 90 carbonate islands and numerous pinnacle and patch reefs. We utilize 700 km hydroacoustic data acquired using EdgeTech sub-bottom profiler during two research cruises with KAUST RV EXPLORER. An age model was established by utilizing a recently published Red Sea sea-level curve. Available climate data were used for the reconstructions of depositional environments. Data analysis reveals five depositional units: U1(Holocene) to U5(Late Pleistocene). Nine hydroacoustic facies are identified to describe the internal architecture, from homogenous reflection-free to wavy laminated facies. The oldest unit (U5) consists of homogeneous facies and reef facies. The unit is overlain by units 4 and 3, with up to five meters thick homogeneous facies and stratified facies. Unit 2 has a maximum thickness of 3 meters and consists of wavy laminated facies. Unit 1 is the youngest unit and consists of several facies, including heterogeneous, homogeneous, stratified, drift, reef, and reef debris facies. During MIS5e (U5), the Red Sea was experiencing a pluvial period, while the sea level was 10 meters higher than the present, leading to total flooding of the lagoon. Most of today's exposed carbonate islands in the lagoon correspond to carbonate accumulation during MIS5e. The depositional environment is interpreted as carbonate-dominated with the frequent siliciclastic influx in the coastal region during heavy rain. In the subsequent periods (MIS 5d to 5a), sea level dropped stepwise and exposed the platform partly. Stratified facies indicate terrestrial sediment input introduced during short pluvial periods. In the following glacial period (MIS 4 to 2), the platform was fully exposed for over 70,000 years. Due to the hyper-arid climate, we interpret unit 2 as an aeolian deposit likely reworked during Holocene transgression. During the platform's flooding in the Holocene, carbonate sedimentation restarted while coastal near stratified facies indicate an increased terrestrial influx during the short Holocene pluvial period (10,000-6000 years ago). The modern Al Wajh lagoon experiences an arid climate, with active carbonate sedimentations and minimal terrestrial input. Although the Red Sea has experienced several humid periods during the last 125,000 years, and extensive diagenetic alteration is recognized in the island's drill cores, no karst morphology has been identified. Results indicate that climate highly influences Al Wajh lagoon architecture, shown by its unique characteristics, including extensive carbonate deposition, intermittent terrestrial influx including aeolian deposits, and minimum karstification. Insights of this study will improve our understanding of the architecture of carbonate platforms in the subsurface deposited under similar conditions.
  • A Gradient-based Deep Neural Network Model for Simulating Multiphase Flow in Porous Media

    Yan, Bicheng; Harp, Dylan Robert; Chen, Bailian; Hoteit, Hussein; Pawar, Rajesh J. (Journal of Computational Physics, Elsevier BV, 2022-05-10) [Article]
    Simulation of multiphase flow in porous media is crucial for the effective management of subsurface energy and environment-related activities. The numerical simulators used for modeling such processes rely on spatial and temporal discretization of the governing mass and energy balance partial-differential equations (PDEs) into algebraic systems via finite-difference/volume/element methods. These simulators usually require dedicated software development and maintenance, and suffer low efficiency from a runtime and memory standpoint for problems with multi-scale heterogeneity, coupled-physics processes or fluids with complex phase behavior. Therefore, developing cost-effective, data-driven models can become a practical choice, and in this work, we choose deep learning approaches as they can handle high dimensional data and accurately predict state variables with strong nonlinearity. In this paper, we describe a gradient-based deep neural network (GDNN) constrained by the physics related to multiphase flow in porous media. We tackle the nonlinearity of flow in porous media induced by rock heterogeneity, fluid properties, and fluid-rock interactions by decomposing the nonlinear PDEs into a dictionary of elementary differential operators. We use a combination of operators to handle rock spatial heterogeneity and fluid flow by advection. Since the augmented differential operators are inherently related to the physics of fluid flow, we treat them as first principles prior knowledge to regularize the GDNN training. We use the example of pressure management at geologic CO2 storage sites, where CO2 is injected in saline aquifers and brine is produced, and apply GDNN to construct a predictive model that is trained with physics-based simulation data and emulates the physics process. We demonstrate that GDNN can effectively predict the nonlinear patterns of subsurface responses, including the temporal and spatial evolution of the pressure and CO2 saturation plumes. We also successfully extend the GDNN to convolutional neural network (CNN), namely gradient-based CNN (GCNN), and validate its capability to improve the prediction accuracy. GDNN has great potential to tackle challenging problems that are governed by highly nonlinear physics and enable the development of data-driven models with higher fidelity.
  • Numerical investigations of the PUGA geothermal reservoir with multistage hydraulic fractures and well patterns using fully coupled thermo-hydro-geomechanical modeling

    Gudala, Manojkumar; Govindarajan, Suresh Kumar; Yan, Bicheng; Sun, Shuyu (Energy, Elsevier BV, 2022-05-06) [Article]
    The Puga geothermal reservoir is located in the south-eastern part of Ladakh (Himalayan region, India), and it is providing encouraging results towards heat production. We proposed an improved mathematical model for the fully coupled thermo-hydro-geomechanical model to examine the variations in the Puga geothermal reservoir at between 4500 m from the surface with three, four, and seven hydraulic fractures in the reservoir along with four-spot, five-spot, seven-spot, and nine-spot well patterns. The distribution of low-temperature region is found in each fracture, and it is low in the reservoir with seven hydraulic fractures. The changes in the rock and fluid properties are examined effectively. Thermal strain is dominated in the fractures, and mechanical strain is impressive in the rock matrix; it is dependent on the number of hydraulic fractures and well patterns. The thermal performance of the Puga reservoir is examined with the geothermal life, reservoir impedance, and heat power and found that the number of hydraulic fractures and well patterns are influenced significantly in the multistage modeling of the Puga geothermal reservoir. Thus, the proposed mathematical model can effectively evaluate and predict the variations that occur in the Puga geothermal reservoir with dynamic rock, fracture, and fluid properties.
  • A robust Upwind Mixed Hybrid Finite Element method for transport in variably saturated porous media

    Younes, Anis; Hoteit, Hussein; Helmig, Rainer; Fahs, Marwan (Copernicus GmbH, 2022-04-27) [Preprint]
    The Mixed Finite Element (MFE) method is well adapted for the simulation of fluid flow in heterogeneous porous media. However, when employed for the transport equation, it can generate solutions with strong unphysical oscillations because of the hyperbolic nature of advection. In this work, a robust upwind MFE scheme is proposed to avoid such unphysical oscillations. The new scheme is a combination of the upwind edge/face centred Finite Volume (FV) method with the hybrid formulation of the MFE method. The scheme ensures continuity of both advective and dispersive fluxes between adjacent elements and allows to maintain the time derivative continuous, which permits employment of high order time integration methods via the Method of Lines (MOL). Numerical simulations are performed in both saturated and unsaturated porous media to investigate the robustness of the new upwind-MFE scheme. Results show that, contrarily to the standard scheme, the upwind-MFE method generates stable solutions without under and overshoots. The simulation of contaminant transport into a variably saturated porous medium highlights the robustness of the proposed upwind scheme when combined with the MOL for solving nonlinear problems.
  • Modelling the initiation of bitumen-filled microfractures in immature, organic-rich carbonate mudrocks: The Maastrichtian source rocks of Jordan

    Abu Mahfouz, Israa Salem; Wicaksono, Akbar Nugroho; Idiz, Erdem; Cartwright, Joe; Santamarina, Carlos; Vahrenkamp, Volker (Marine and Petroleum Geology, Elsevier BV, 2022-04-22) [Article]
    The initiation of bitumen-filled microfractures was analysed in the organic-rich Maastrichtian carbonate mudrocks of Jordan, which show great potential as source rocks and for a future unconventional hydrocarbon play. A modelling approach was performed to assess the possible scenarios causing horizontal small-scale (mm to cm in length) bitumen fractures (microfractures) at the immature stage. The aim was to back-calculate how much overpressure and bitumen generation was needed in the past to initiate horizontal microfracturing, comparing those simulated parameters with the actual generation potential from the source rock samples. The results show that the local overpressure resulting from the bitumen generation during early catagenesis was not high enough to initiate the microfracturing. We hypothesise that the increase of internal pressure was caused by the inability of the bitumen to be squeezed into the pore space during burial. The resulting overpressure induced a perturbation to the stable-state stress distribution around the kerogen boundary that eventually led to the initiation of horizontal microfractures along the tip of bitumen flakes. Subsequently, short-distance migration of bitumen and a significant decrease in pressure have prevailed in the study area. This proves that primary migration can occur long before the source rock reaches the oil or gas windows, at a comparatively shallow burial depth. This also indicates that the first framework pathways by the precursor horizontal microfractures may control the flow patterns of the hydrocarbons within source rocks. Understanding these factors is critical to predicting the impact of these microscale fractures on hydrocarbon expulsion and storage, and hence likely productivity of an analogous subsurface unconventional reservoir.
  • Pore-Scale Spontaneous Imbibition at High Advancing Contact Angles in Mixed-Wet Media: Theory and Experiment

    Saad, Ahmed Mohamed; Yutkin, Maxim; Radke, Clayton J.; Patzek, Tadeusz (Energy & Fuels, American Chemical Society (ACS), 2022-04-22) [Article]
    Mixed wettability develops naturally on a pore scale in oil reservoirs after primary drainage. The invading oil fills pore interiors that become oil-wet by asphaltene deposition, while the residual water retreats into the pore corners, masking them and retaining their water wetness. This wettability alteration hinders oil mobilization during secondary waterflood. Therefore, a proper understanding of the conditions controlling pore-scale imbibition into mixed-wet pores may lead to a substantial increase in oil recovery from the portions of reservoir rocks bypassed during the original waterflood. We use selective silane coating to fabricate reservoir-representative mixed-wet capillaries with angular cross-sections. We validate our procedure on silica and glass substrates and characterize the mixed-wet surfaces by atomic force microscopy, scanning electron microscopy, and contact angle measurements. Subsequently, we investigate experimentally the invasion of water against air in mixed-wet, water-wet, and oil-wet square capillaries and compare our findings with the theoretical predictions of dynamic (Washburn, Szekely, and Bosanquet) and quasi-static [Mayer–Stowe–Princen (MSP)] meniscus-invasion models. None of the dynamic models for ducts of uniform wettability can fully describe our experimental data in mixed-wet capillaries. However, the experimental results agree with the predictions of MSP theory. We discuss the similarities and differences between experiment and theory and the reasons for the failure of the dynamic models. To our knowledge, this is the first direct experimental validation of MSP theory under mixed-wet conditions in such a controlled manner. We confirm the possibility of spontaneous piston-type imbibition with high (>90°) advancing contact angles into mixed-wet pores, given that the contact angle is lowered below a critical value that is a function of the pore geometry and water saturation. In oil reservoirs, injection of custom-designed brines would be required to change the contact angle to values below the imbibition threshold
  • Fast Screening of LSW Brines Using QCM-D and Crude Oil-Brine Interface Analogs

    Yutkin, Maxim; Kaprielova, K. M.; Kamireddy, Sirisha; Gmira, A.; Ayirala, S. C.; Radke, C. J.; Patzek, Tadeusz (SPE, 2022-04-18) [Conference Paper]
    This work focuses on a potentially economic incremental oil-recovery process, where a brine amended with inexpensive salts (in contrast to expensive surfactants and other chemicals) is injected into a reservoir to increase oil production. Historically, this process received the name of low salinity waterflooding (LSW) although the salinity is not always low(er). Nevertheless, we keep using this terminology for historical reasons. The idea of LSW has been known for three decades, but to the best of our knowledge no specific brine recipes that guarantee success have been presented so far. The reasons hide in the problem's complexity, disagreements in the scientific community, and a race to publish rather than to understand the fundamental principles behind the process. In this paper, we present an experimental model system that captures many of the important fundamental features of the natural process of crude oil attachment to mineral surfaces, but at the same time decomposes this complex process into simpler parts that can be more precisely controlled and understood. We systematically investigate the first-order chemical interactions contributing to the well-known strong attachment of crude oil to minerals using SiO2 as a mineral for its surface chemistry simplicity. Our preliminary results suggest that magnesium and sulfate ions are potent in detaching amino/ammonium-based linkages of crude oil with a SiO2 surface. However, when used together in the form of MgSO4, they lose part of their activity to the formation of a MgSO4 ion pairs. We also find that sulfate-detachment propensity stems not from the interaction with prototype mineral surface, but rather from the interactions with the crude oil-brine interface analog. We continue the systematic study of the ion effects on crude oil detachment, with and more results following in the future.

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