Development of spatial permeability variations in English chalk aquifers

2021 ◽  
pp. SP517-2020-93
Author(s):  
Stephen R. H. Worthington ◽  
Aidan E. Foley
Keyword(s):  
Water Table ◽  
Dissolution Kinetics ◽  
Stress Relief ◽  
Dual Porosity ◽  
Low Permeability ◽  
Dissolution Profile ◽  
Saturated Zone ◽  
High Permeability ◽  
Feedback Effects ◽  
Permeability Structure

AbstractThe Cretaceous Chalk in England forms dual-porosity aquifers, with low-permeability matrix and high-permeability network of fissures, which are predominantly stress-relief fractures that have been enlarged by dissolution. This enlargement is a function of the volume of water that has passed along a fracture (the flowrate effect) and its degree of chemical undersaturation. Feedback effects result in the development of a distinctive permeability structure, with four particular characteristics: i) troughs in the water table with high transmissivity and convergent groundwater flow; ii) substantial increases in transmissivities in a downgradient direction; iii) downgradient decreases in hydraulic gradient; and iv) discharge from the high-transmissivity zones to the surface commonly at substantial springs. This distinctive self-organised permeability structure occurs throughout unconfined chalk aquifers. Early enlargement of fissures at a depth of 50 - 100 m below the water table is slow, but is much more rapid close to the water table and in the uppermost bedrock due to non-linear dissolution kinetics. A modelled dissolution profile shows that more than 95% of dissolution takes place in the top 1 m of bedrock, and that enlargement of fissures in the saturated zone results from progressive dissolution occurring over a period of a million years or more.

Modeling of filtration processes in periodic porous media

2021 ◽  
pp. 90-93
Author(s):  
Gennadiy Sandrakov ◽  
Andrii Hulianytskyi ◽  
Vladimir Semenov
Keyword(s):  
Porous Media ◽  
Parabolic Equations ◽  
Initial Boundary ◽  
Dynamic Processes ◽  
Low Permeability ◽  
Initial Boundary Value Problems ◽  
High Permeability ◽  
Guaranteed Accuracy ◽  
The Media ◽  
Initial Boundary Value

Modeling of dynamic processes of diffusion and filtration of liquids in porous media are discussed. The media are formed by a large number of blocks with low permeability, and separated by a connected system of faults with high permeability. The modeling is based on solving initial boundary value problems for parabolic equations of diffusion and filtration in porous media. The structure of the media leads to the dependence of the equations on a small parameter. Assertions on the solvability and regularity of such problems and the corresponding homogenized convolution problems are considered. The statements are actual for the numerical solution of this problem with guaranteed accuracy that is necessary to model the considered processes.

A Novel Coreflood Test to Evaluate EOR Potential of Wettability-Altering Surfactants in Oil-Wet Heterogeneous Carbonate Reservoirs

2021 ◽  
Author(s):  
Yue Shi ◽  
Kishore Mohanty ◽  
Manmath Panda
Keyword(s):  
Oil Recovery ◽  
Carbonate Reservoirs ◽  
Wettability Alteration ◽  
Low Permeability ◽  
High Permeability ◽  
Matrix Permeability ◽  
Rock Heterogeneity ◽  
The Matrix ◽  
Flow Through ◽  
Main Factors

Abstract Oil-wetness and heterogeneity (i.e., existence of low and high permeability regions) are two main factors that result in low oil recovery by waterflood in carbonate reservoirs. The injected water is likely to flow through high permeability regions and bypass the oil in low permeability matrix. In this study, systematic coreflood tests were carried out in both "homogeneous" cores and "heterogeneous" cores. The heterogeneous coreflood test was proposed to model the heterogeneity of carbonate reservoirs, bypassing in low-permeability matrix during waterfloods, and dynamic imbibition of surfactant into the low-permeability matrix. The results of homogeneous coreflood tests showed that both secondary-waterflood and secondary-surfactant flood can achieve high oil recovery (>50%) from relatively homogenous cores. A shut-in phase after the surfactant injection resulted in an additional oil recovery, which suggests enough time should be allowed while using surfactants for wettability alteration. The core with a higher extent of heterogeneity produced lower oil recovery to waterflood in the coreflood tests. Final oil recovery from the matrix depends on matrix permeability as well as the rock heterogeneity. The results of heterogeneous coreflood tests showed that a slow surfactant injection (dynamic imbibition) can significantly improve the oil recovery if the oil-wet reservoir is not well-swept.

scholarly journals The possibility of the application of the zeolyte powders for the construction of the membranes for the carbon dioxide separation

2015 ◽  
Vol 21 (2) ◽  
pp. 277-284
Author(s):  
Dragutin Nedeljkovic ◽  
Marija Stevanovic ◽  
Mirko Stijepovic ◽  
Aleksandar Stajcic ◽  
Aleksandar Grujic ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Diffusion Mechanism ◽  
Composite Membranes ◽  
Polymer Chains ◽  
Mixed Matrix Membrane ◽  
Low Permeability ◽  
High Permeability ◽  
Mixed Matrix ◽  
Carbon Dioxide Separation ◽  
Inorganic Particles

The task of this work was to construct the mixed matrix membrane based on polymer that could be used for the treatment of the waste gases. Therefore, high permeability for the carbon dioxide and low permeability for other gases commonly present in the industrial combustion waste gases (nitrogen, oxygen, hydrogen, methane) are essential. Those membranes belong to the group of dense composite membranes, and mechanism for separation is based on the solution-diffusion mechanism. In this paper, feasibility of the application of poly(ethyleneoxid)-copoly(phtalamide) was tested. In order to enchase the permeability of carbon dioxide, three different zeolites were incorporated, and in order to improve compatibility between the inorganic particles and polymer chains, n-tetradecyldimethylamonium bromide (NTAB).was added. Three zeolites were with the 2-dimensional pores (IHW, NSI and TER). The best results in carbon dioxide/hydrogen selectivity were obtained with the membrane constructed with PEBAX 1657 and surface treated zeolites, while the better results concerning selectivity were gained with membranes based on the Polyactive.

Fractal Application in Micro Rock Mechanics of Low-Permeability Oil Reservoirs and Its Relationship with Enlarging Producing Reserves by Gemini Surfactant Flooding

2010 ◽  
Vol 29-32 ◽  
pp. 170-176 ◽  
Author(s):  
Heng Wei ◽  
Lei Wei ◽  
Jian Hui Yin ◽  
Fu Ling Yin ◽  
Jun Han Liu ◽  
...  
Keyword(s):  
Rock Mechanics ◽  
Gemini Surfactant ◽  
Fractal Dimensions ◽  
Oil Reservoirs ◽  
Low Permeability ◽  
Surfactant Flooding ◽  
High Permeability ◽  
Fractal Method ◽  
Pore Structures ◽  
Conventional Methods

Low permeability oil reservoirs were usually considered low quality reserves. However, low permeability oil reservoirs account for more and more percent of the proven reserves year by year in China. Conventional methods for analyzing medium-hign permeability cores are not suitable to low-permeability cores. Based on fractal method and the mercury injection curve data, the fractal dimensions of the pore structures of low permeability oil reservoirs are different from those of medium-high permeability oil reservoirs. The fractal dimensions of the pore structures of low permeability oil reservoirs are less than 2. Low permeability oil reservoirs which were not able to be developed are able to be developed by gemini surfactant flooding. This helps more and more low quality reserves be turned into producing reserves.

Understanding the Plugging Performance of HPAM-Cr (III) Polymer Gel for CO2 Conformance Control

SPE Journal ◽  
2020 ◽  
Author(s):  
Xindi Sun ◽  
Baojun Bai ◽  
Ali Khayoon Alhuraishawy ◽  
Daoyi Zhu
Keyword(s):  
Pressure Gradient ◽  
Low Permeability ◽  
Far Field ◽  
Polymer Gel ◽  
Co2 Flooding ◽  
High Permeability ◽  
Conformance Control ◽  
Gel Treatment ◽  
Plugging Performance ◽  
Breakthrough Pressure

Summary With the demand for conformance control in carbon dioxide (CO2) flooding fields, hydrolyzed polyacrylamide-chromium [HPAM-Cr (III)] polymer gel has been applied in fields for CO2 conformance control. However, the field application results are mixed with success and failure. This paper is intended to understand the HPAM-Cr (III) polymer gel plugging performance in CO2 flooding reservoirs through laboratory experiments and numerical analysis. We conducted core flooding tests to understand how the cycles of CO2 and water affect the HPAM-Cr (III) polymer gel plugging efficiency to CO2 and water during a water-alternating-gas (WAG) process. Berea Sandstone cores with the permeability range of 107 to 1225 md were used to evaluate the plugging performance in terms of residual resistance factor and breakthrough pressure, which is the minimum pressure required for CO2 to enter the gel-treated cores.We compared the pressure gradient from the near-wellbore to far-field with the gel breakthrough pressure, from which we analyzed under which conditions the gel treatment could be more successful. Results show that HPAM-Cr (III) polymer gel has higher breakthrough pressure in the low-permeability cores. The polymer gel can reduce the permeability to water much more than that to CO2. The disproportionate permeability reduction performance was more prominent in low-permeability cores than in high-permeability cores. The gel resistance to both CO2 and brine significantly decreased in later cycles. In high-permeability cores, the gel resistance to CO2 became negligible only after two cycles of water and CO2 injection. Because of the significant reduction of pressure gradient from near-wellbore to far-field in a radial flow condition and the dependence of breakthrough pressure on permeability and polymer concentration, we examined hypothetical reservoirs with no fractures, in which impermeable barriers separated high- and low-permeability zones and in which the gel was only placed in the high-permeability zone. We considered two scenarios: CO2 breaking through the gel and no CO2 breakthrough. No breakthrough represents the best condition in which the gel has no direct contact and can be stable in reservoirs for long. In contrast, the breakthrough scenario will result in the gel’s significant degradation and dehydration resulting from CO2 flowing through the gel, which will cause the gel treatment to fail.

Efficiency of foam flushing remediation in heterogeneous soil contaminated by nitrobenzene

2019 ◽  
Vol 15 (1) ◽  
pp. 28-37
Author(s):  
Su Yan ◽  
Cheng Weiguo ◽  
Li Yabin ◽  
Wang Jian
Keyword(s):  
Heterogeneous Media ◽  
Removal Rate ◽  
Low Permeability ◽  
High Permeability ◽  
Total Removal ◽  
Remediation Efficiency ◽  
Heterogeneous Soil ◽  
Dimensional Simulation ◽  
Remediation Process ◽  
Interface Effects

Abstract The spatial distribution of nitrobenzene in a heterogeneous medium during the foam flushing remediation process was investigated through a two-dimensional simulation device. The remediation efficiency and the mechanisms of action of the surfactant foam remediation process in heterogeneous media were also studied. The experiments showed that during the contamination process, nitrobenzene preferentially enters the low-permeability zones of the medium and is intercepted as a free phase, bypassing the high-permeability zones. In the surfactant foam remediation process, a total removal rate of 95.7% was achieved, with the mobilization effect contributing 69.5%, and the solubilization and volatilization contributing 21.6% and 1.5%, respectively. Mobilization, solubilization, and volatilization are the main mechanisms by which nitrobenzene is eliminated from the soil during the surfactant foam remediation process. Finally, it has also been observed that this process showed a higher removal efficiency in high-permeability media than in low-permeability media due to interface effects.

scholarly journals Enhanced Oil Recovery by a Suspension of Core-Shell Polymeric Nanoparticles in Heterogeneous Low-Permeability Oil Reservoirs

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 600 ◽  
Author(s):  
Long ◽  
Wang ◽  
Zhu ◽  
Huang ◽  
Leng ◽  
...  
Keyword(s):  
Enhanced Oil Recovery ◽  
Newtonian Fluid ◽  
Oil Recovery ◽  
Polymeric Nanoparticles ◽  
Low Permeability ◽  
High Permeability ◽  
Permeability Ratio ◽  
Nanoparticle Suspension ◽  
Shear Rates ◽  
Low Permeability Reservoirs

Polymeric nanoparticle suspension is a newly developed oil-displacing agent for enhanced oil recovery (EOR) in low-permeability reservoirs. In this work, SiO2/P(MBAAm-co-AM) polymeric nanoparticles were successfully synthesized by a simple distillation–precipitation polymerization method. Due to the introduction of polymer, the SiO2/P(MBAAm-co-AM) nanoparticles show a favorable swelling performance in aqueous solution, and their particle sizes increase from 631 to 1258 nm as the swelling times increase from 24 to 120 h. The apparent viscosity of SiO2/P(MBAAm-co-AM) suspension increases with an increase of mass concentration and swelling time, whereas it decreases as the salinity and temperature increase. The SiO2/P(MBAAm-co-AM) suspension behaves like a non-Newtonian fluid at lower shear rates, yet like a Newtonian fluid at shear rates greater than 300 s−1. The EOR tests of the SiO2/P(MBAAm-co-AM) suspension in heterogeneous, low-permeability cores show that SiO2/P(MBAAm-co-AM) nanoparticles can effectively improve the sweep efficiency and recover more residual oils. A high permeability ratio can result in a high incremental oil recovery in parallel cores. With an increase of the permeability ratio of parallel cores from 1.40 to 15.49, the ratios of incremental oil recoveries (low permeability/high permeability) change from 7.69/4.61 to 23.61/8.46. This work demonstrates that this SiO2/P(MBAAm-co-AM) suspension is an excellent conformance control agent for EOR in heterogeneous, low-permeability reservoirs. The findings of this study can help to further the understanding of the mechanisms of EOR using SiO2/P(MBAAm-co-AM) suspension in heterogeneous, low-permeability reservoirs.

Distribution, origin, and hydraulic influence of fractures in a clay-rich glacial deposit

1995 ◽  
Vol 32 (6) ◽  
pp. 957-975 ◽  
Author(s):  
L.D. McKay ◽  
J. Fredericia
Keyword(s):  
Hydraulic Conductivity ◽  
Groundwater Flow ◽  
Key Words ◽  
Water Table ◽  
Stress Relief ◽  
Fracture Density ◽  
Lacustrine Environment ◽  
Tritium Content ◽  
Glacial Deposit ◽  
A Site

In the unconsolidated clay-rich glacial deposits underlying a site in southwestern Ontario, fractures and root casts greatly influence hydraulic conductivity and groundwater flow. The fractures are predominantly vertical and have visible oxidation staining from surface to a depth of 6 m. Root casts commonly occur along fracture surfaces in the upper 3 m, but can also occur as holes in apparently unfractured blocks. The fractures are believed caused mainly by dessication during past periods of low water table. This hypothesis is supported by a decrease in fracture density with depth and the presence of a stiff crust, presumably caused by desiccation-induced consolidation. The random pebble fabric and faint layering indicate deposition in a calm lacustrine environment, which precludes the possibility of the fractures having been caused by overriding ice. Fractures were found below the depth of oxidation staining (6 m) but most of these appear to have been caused by stress-relief due to the excavation and subsequent drying. In the upper 3 m the fractures and root casts are responsible for field-measured hydraulic conductivity values that are up to 3 orders of magnitude greater than measured in the laboratory for samples of the unfractured matrix. High values of field-measured hydraulic conductivity, seasonal head variations greater than 0.5 m, and high tritium content all persist below the depth of root casts, indicating that hydraulically conductive fractures do exist to depths of at least 6 m and possibly as great as 12–15 m, which is well below the depth of oxidation staining. However, there is some uncertainty in this assessment of the extent of hydraulically conductive fractures because of the sensitivity to small leaks in the piezometer installations. Key words : clay, glacial, fractures, desiccation, hydraulic conductivity.

Sign in / Sign up

Export Citation Format

Share Document