Effect of Organosilicon-Acrylic Emulsion Treatment on Wettability of Porous Media

To investigate the influence of the organosilicon-acrylic on wetting properties of porous media, contact angle tests were performed on two different sandstones. In addition, the effectiveness of the emulsion on wettability alteration of porous media was validated by capillary rise and spontaneous imbibition tests. The results of wettability tests showed that the wettability of two sandstones was altered from water-wet to gas-wet after treatment with the emulsion. The principle that the critical radius of pore throats and wettability of porous media affect liquids flow was derived analytically and verified experimentally. Coreflood results demonstrated that the latex resulted in increasing the water permeability through altering the rock wettability to gas-wetting, then decreasing the friction drag between liquids and rocks surface. Thereby, the emulsion treatment could increase the flowback rate of trapped liquids. Experimental results were in good agreement with the theoretical analysis. In conclusion, all results indicated that the emulsion could alter the wettability from water-wet to intermediate gas-wet and enhance water permeability in porous media. It was extrapolated that the emulsion had the tremendous potential to be applied in field conditions, enhancing gas productivity through the cleanup of trapped water in the vicinity of the wellbore.     

Comparison of Flow and Transport Experiments on 3D Printed Micromodels with Direct Numerical Simulations

Understanding pore-scale flow and transport processes is important for understanding flow and transport within rocks on a larger scale. Flow experiments on small-scale micromodels can be used to experimentally investigate pore-scale flow. Current manufacturing methods of micromodels are costly and time consuming. 3D printing is an alternative method for the production of micromodels. We have been able to visualise small-scale, single-phase flow and transport processes within a 3D printed micromodel using a custom-built visualisation cell. Results have been compared with the same experiments run on a micromodel with the same geometry made from polymethyl methacrylate (PMMA, also known as Perspex). Numerical simulations of the experiments indicate that differences in experimental results between the 3D printed micromodel and the Perspex micromodel may be due to variability in print geometry and surface properties between the samples. 3D printing technology looks promising as a micromodel manufacturing method; however, further work is needed to improve the accuracy and quality of 3D printed models in terms of geometry and surface roughness.

     

A Hierarchical Sampling for Capturing Permeability Trend in Rock Physics

Among all properties of reservoir rocks, permeability is an important parameter which is typically measured from core samples in the laboratory. Due to limitations of core drilling all over a reservoir, simulation of rock porous media is demanded to explore more scenarios not seen in the available data. One of the most accurate methods is cross correlation based simulation (CCSIM) which recently has broadly applied in geoscience and porous media. The purpose of this study is producing realizations with the same permeability trend to a real sample. Berea sandstone sample is selected for this aim. Permeability results, extracted from smaller sub-samples of the original sample, showed that classic Kozeny–Carman permeability trend is not suitable for this sample. One reason can be due to lack of including geometrical and fractal properties of pore-space distribution in this equation. Thus, a general trend based on fractal dimensions of pore-space and tortuosity of the Berea sample is applied in this paper. Results show that direct 3D stochastic modeling of porous media preserves porous structure and fractal behavior of rock. On the other hand, using only 2D images for constructing the 3D pore structures does not reproduce the measured experimental permeability. For this aim, a hierarchical sampling is implemented in two and three steps using both 2D and 3D stochastic modeling. Results showed that two-step sampling is not suitable enough, while the utilized three-step sampling occurs to be show excellent performance by which different models of porous media with the same permeability trend as the Berea sandstone sample can be generated.     

3D打印混凝土各向异性力学性能研究

近年来,混凝土3D打印技术在土木建筑等领域取得了快速的发展和应用。与模板浇筑工艺不同,3D打印在逐行逐层堆叠的建造过程中引入了一定量的层间弱面和空隙,造成了细观非均质性;而且3D打印过程无法自动嵌入钢筋,制备纤维混凝土作为打印材料可有效改善力学性能。本文首先制备了一种适用于挤出型3D打印工艺的玄武岩纤维增强陶砂混凝土,将水平打印层作为XY平面,然后从三个正交方向加载,实验测试了3D打印混凝土的抗压、抗弯等力学性能,提出了各向异性系数及其评估方法。研究结果表明,对于单轴压缩,X方向强度最高,而对于抗弯性能,Y方向强度最高。纤维对挤出型3D打印材料的各向异性影响较大,纤维掺量越大,各向异性越大。     

Pore Network Modelling of Electrical Resistivity and Capillary Pressure Characteristics

In order to model petrophysical properties of hydrocarbon reservoir rocks, the underlying physics occurring in realistic rock pore structures must be captured. Experimental evidence showing variations of wetting occurring within a pore, and existence of the so-called 'non-Archie' behaviour, has led to numerical models using pore shapes with crevices (for example, square, elliptic, star-like shapes, etc.). This paper presents theoretical derivations and simulation results of a new pore space network model for the prediction of petrophysical properties of reservoir rocks. The effects of key pore geometrical factors such as pore shape, pore size distribution and pore co-ordination number (pore connectivity) have been incorporated into the theoretical model. In particular, the model is used to investigate the effects of wettability and saturation history on electrical resistivity and capillary pressure characteristics. The petrophysical characteristics were simulated for reservoir rock samples. The use of the more realistic grain boundary pore (GBP) shape allows simulation of the generic behaviour of sandstone rocks, with various wetting scenarios. The predictions are in close agreement with electrical resistivity and capillary pressure characteristics observed in experiments.     

Analysis of Microscopic Displacement Mechanisms of a MIOR Process in Porous Media with Different Wettability

Transport in Porous Media - The wettability of the reservoir rock has an important effect on the displacement of fluids on a microscopic scale in all EOR processes, especially in the microbial...     

3D打印多孔热固性聚酰亚胺含油复合材料

以氯化钠(NaCl)作为致孔剂与流变性能调节剂,碳纤维(CF)作为增强填料与流变性能调节剂,苯乙炔基封端聚酰胺酸溶液(PAA)作为基体树脂,配制适用于直书写3D打印的复合墨水,室温下打印成形后经热固化处理和NaCl刻蚀去除后制备了多孔热固性聚酰亚胺/碳纤维(TSPI/CF)复合材料. 研究表明:NaCl与CF对复合墨水的流变学性能具有好的调节作用;打印制备的TSPI/CF复合材料具有低的各向同性尺寸收缩和优异的耐热性能,且耐热性能随着CF含量的增加而提高;CF含量升高,TSPI/CF复合材料的孔隙率提高,平均孔径降低,力学性能增强;多孔TSPI/CF复合材料表现出优异的储油、出油性能以及浸油摩擦学性能.      

Permanent Alteration of Porous Media Wettability from Liquid-Wetting to Intermediate Gas-Wetting

Wettability of Berea and low permeability reservoir rocks are permanently altered from liquid-wetting to intermediate gas-wetting. We use water and decane as model liquid, and air and nitrogen as model gas in the experiments. New chemicals with various functional groups are used in the wettability alteration. We perform compositional analyses of the treated chemical solutions extracted from rock treatment by gas chromatography–mass spectrometry (GCMS) and by inductively coupled plasma-mass spectrometry (ICPMS). The analyses demonstrate reaction between the chemicals and the rock substrate. There is no measurable change in permeability from the chemical reaction for the low molecular weight chemicals. The results reveal the permanent alteration of wettability. Tests are conducted to measure contact angle, spontaneous imbibition, and flow to assess the effect of wettability alteration on flow performance as a function of chemical concentration and functionality. For Berea, the contact angle for the water–air–rock is altered from 0° to ~150° depending on the chemical concentration. For the reservoir rock, the contact angle is altered from ~70° to ~130°. As a result of the treatment, the water flow rate may increase two and a half times for a given pressure drop in the Berea. The permanent alteration of wettability with the new chemicals is intended for prevention of water blocking in gas production from tight reservoirs. Instead of hydraulic fracturing when water is introduced in formations with most of the water retained by the water-wet rocks, one may use the new chemical surfactants in fracturing to avoid water retention for high gas well productivity.     

Transport of Polymer Particles in Oil–Water Flow in Porous Media: Enhancing Oil Recovery

Transport in Porous Media - 3D printing with powders offers the most analogous method to the natural way in which clastic reservoir rocks are formed, resulting in pore network textures and...     

Does ITZ Influence Moisture Transport in Concrete?

Simulations of nuclear magnetic resonance (NMR) signal from fluids contained in porous media (such as rock cores) need to account for both enhanced surface relaxation and the presence of internal magnetic field gradients due to magnetic susceptibility contrast between the rock matrix and the contained fluid phase. Such simulations are typically focussed on the extraction of the NMR T₂ relaxation distribution which can be related to pore size and indirectly to system permeability. Discrepancies between such NMR signal simulations on digital rock cores and associated experimental measurements are however frequently reported; these are generally attributed to spatial variations in rock matric composition resulting in heterogeneously distributed NMR surface relaxivities (ρ) and internal magnetic field gradients. To this end, a range of synthetic sediments composed of variable mixtures of quartz and garnet sands were studied. These two constituents were selected for the following reasons: they have different densities allowing for ready phase differentiation in 3D μCT images of samples to use as simulation lattices and they have distinctly different ρ and magnetic susceptibility values which allow for a rigorous test of NMR simulations. Here these 3D simulations were used to calculate the distribution of internal magnetic field gradients in the range of samples, these data were then compared against corresponding NMR experimental measurements. Agreement was reasonably good with the largest discrepancy being the simulation predicting weak internal gradients (in the vicinity of the quartz sand for mixed samples) which were not detected experimentally. The suite of 3D μCT images and associated experimental NMR measurements are all publicly available for the development and validation of NMR simulation efforts.

     

Experimental and numerical study of the effect of silica filler on the tensile strength of a 3D-printed particulate nanocomposite

Polymers are commonly found to have low mechanical properties, e.g., low stiffness and low strength. To improve the mechanical properties of polymers, various types of fillers have been added. These fillers can be either micro- or nano-sized; however; nano-sized fillers are found to be more efficient in improving the mechanical properties than micro-sized fillers. In this research, we have analysed the mechanical behaviour of silica reinforced nanocomposites printed by using a new 5-axis photopolymer extrusion 3D printing technique. The printer has 3 translational axes and 2 rotational axes, which enables it to print free-standing objects. Since this is a new technique and in order to characterise the mechanical properties of the nanocomposites manufactured using this new technique, we carried out experimental and numerical analyses. We added a nano-sized silica filler to enhance the properties of a 3D printed photopolymer. Different concentrations of the filler were added and their effects on mechanical properties were studied by conducting uniaxial tensile tests. We observed an improvement in mechanical properties following the addition of the nano-sized filler. In order to observe the tensile strength, dog-bone samples using a new photopolymer extrusion printing technique were prepared. A viscoelastic model was developed and stress relaxation tests were conducted on the photopolymer in order to calibrate the viscoelastic parameters. The developed computational model of nano reinforced polymer composite takes into account the nanostructure and the dispersion of the nanoparticles. Hyper and viscoelastic phenomena was considered to validate and analyse the stress–strain relationship in the cases of filler concentrations of 8%, 9%, and 10%. In order to represent the nanostructure, a 3D representative volume element (RVE) was utilized and subsequent simulations were run in the commercial finite element package ABAQUS. The results acquired in this study could lead to a better understanding of the mechanical characteristics of the nanoparticle reinforced composite, manufactured using a new photopolymer extrusion 5-axis 3D printing technique.     

Generic strength model for dry jointed rock masses

A new nonlinear thermo-mechanical model for heavily jointed rock masses is presented. The model describes poroelasticity, shear-enhanced compaction and brittle–ductile transition in dry porous rocks. The key input parameters of the model, such as elastic moduli, tensile and compressive strength are expressed as functions of the reference porosity of the rock. These functions are based on empirical data for limestones and sandstones and assume that the medium is isotropic. The effect of joints is modeled by scaling down the key model parameters. The scaling rules are found with the help of explicit numerical modeling of randomly jointed media.     

The evaluation of the influence of various parameters on the velocity of elastic wave propagation in a rock medium

A full waveform recording in a borehole during acoustic logging makes it possible to determine the elastic parameters of a medium under in-situ conditions.The velocity of elastic wave propagation in rocks and elastic moduli are influenced by factors connected with its macrostructure and microstructure, as well as with rock overburden and porous pressure and temperature.The results of the calculations of the relationships between the elastic and reservoir parameters of sedimentary rocks are presented in this paper. The theoretical Kuster and Toksöz model has been applied.The influence of the porosity, the pore space coefficient, and the saturation of different media of porous rocks on elastic moduli and on compressional and shear wave propagation have been considered in this model. The complex composition of the skeleton and the influence of clay material in the porous rock are taken into account.     

Permeability mapping in porous media by magnetization prepared centric-scan SPRITE

The ability of porous media to transmit fluids is commonly referred to as permeability. The concept of permeability is central for hydrocarbon recovery from petroleum reservoirs and for studies of groundwater flow in aquifers. Spatially resolved measurements of permeability are of great significance for fluid dynamics studies. A convenient concept of local Darcy’s law is suggested for parallel flow systems. The product of porosity and mean velocity images in the plane across the average flow direction is directly proportional to permeability. Single Point Ramped Imaging with T ₁ Enhancement (SPRITE) permits reliable quantification of local fluid content and flow in porous media. It is particularly advantageous for reservoir rocks characterized by fast magnetic relaxation of a saturating fluid. Velocity encoding using the Cotts pulsed field gradient scheme improves the accuracy of measured flow parameters. The method is illustrated through measurements of 2D permeability maps in a capillary bundle, glass bead packs and composite sandstone samples.     

An Improved Method for Reconstructing the Digital Core Model of Heterogeneous Porous Media

The heterogeneous pore space of porous media strongly affects the storage and migration of oil and gas in the reservoir. In this paper, the cross-correlation-based simulation (CCSIM) is combined with the three-step sample method to reconstruct stochastically 3D models of the heterogeneous porous media. Moreover, the two-point and multiple-point connectivity probability functions are used as vertical constraint conditions to select the boundary points of pore and matrix, respectively. The heterogeneities of pore spaces of four rock samples are investigated, and then our methods are tested on the four samples. Quantitative comparison is made by computing various statistical and petrophysical properties for the original samples, as well as the reconstructed model. It was found that the results from CCSIM-TSS are obviously better than that from CCSIM. Finally, the analysis of the distance (ANODI) was used to measure of the variability between the realizations of the four rock samples. The results demonstrated that the results from CCSIM-TSSmp are better than that from CCSIM-TSStp as the complexity of connectivity and heterogeneities of pore spaces increase.     

Pore-Scale Imaging and Modelling of Reactive Flow in Evolving Porous Media: Tracking the Dynamics of the Fluid–Rock Interface

Transport in Porous Media - Fluid–mineral and fluid–rock interfaces are key parameters controlling the reactivity and fate of fluids in reservoir rocks and aquifers. The interface...     

Pore-Scale Monitoring of Wettability Alteration by Silica Nanoparticles During Polymer Flooding to Heavy Oil in a Five-Spot Glass Micromodel

It is well known that the oil recovery is affected by wettability of porous medium; however, the role of nanoparticles on wettability alteration of medium surfaces has remained a topic of debate in the literature. Furthermore, there is a little information of the way dispersed silica nanoparticles affect the oil recovery efficiency during polymer flooding, especially, when heavy oil is used. In this study, a series of injection experiments were performed in a five-spot glass micromodel after saturation with the heavy oil. Polyacrylamide solution and dispersed silica nanoparticles in polyacrylamide (DSNP) solution were used as injected fluids. The oil recovery as well as fluid distribution in the pores and throats was measured with analysis of continuously provided pictures during the experiments. Sessile drop method was used for measuring the contact angles of the glass surface at different states of wettability after coating by heavy oil, distilled water, dispersed silica nanoparticles in water (DSNW), polyacrylamide solution, and DSNP solution. The results showed that the silica nanoparticles caused enhanced oil recovery during polymer flooding by a factor of 10%. The distribution of DSNP solution during flooding tests in pores and throats showed strong water-wetting of the medium after flooding with this solution. The results of sessile drop experiments showed that coating with heavy oil, could make an oil-wet surface. Coating with distilled water and polymer solution could partially alter the wettability of surface to water-wet and coating with DSNW and DSNP could make a strongly water-wet surface.     

The determination of biot's parameters for sandstones

One of the acceptable theories in describing the wave motions in fluid saturated porous rocks is Biot's theory² In this paper, we present the procedures in the determination of the parameters in Biot's theory. One artificial rock “Alundum’ and three types of natural sandstones were tested. The calculated wave speeds in the rock specimens, based on the experimentally determined Biot's parameters, were found in good agreement with the measured dilatational wave speeds using the ultrasonic pulse method     

Contributions of 3D Printed Fracture Networks to Development of Flow and Transport Models

Transport in Porous Media - Conventional experiments using natural rock samples have trouble in observing rock structures and controlling fracture properties. Taking advantage of 3D printing...