Effective Porosity Research Articles

A parallel programming application of the A* algorithm in digital rock physics

Pore-scale analysis and characterization of reservoir rocks provide valuable information for the definition and management of underground hydrogen storage and CO2 storage or sequestration.This article presents an optimized implementation of the A* algorithm, the most popular pathfinding method in the presence of obstacles. In this context, the algorithm is applied to recognize the minimum length connected paths through each flow direction of 3D images of a porous medium representative of a reservoir rock. The identification of the main paths allows the characterization of the pore space and the calculation of fundamental petrophysical properties such as tortuosity and effective porosity, which can be used for permeability estimation. Compared to other algorithms available for pore-scale characterization, such as the pore centroid, A* provides a better approximation of the pore space available for the flow and, therefore, a reliable characterization of the petrophysical properties. On the other hand, path identification is significantly consuming in terms of time and memory. In this paper, an efficient and optimized implementation based on C++/OpenMP programming language is presented.The proposed implementation aims to the analysis of large-scale models profiting from parallelization, memory optimization, and enhanced managing of dead paths. Three test cases of increasing sizes are presented, to analyze the advantages and the disadvantages of the algorithm as the number of explored points increases. The 3D binary images analyzed are related to a synthetic domain (1 million voxels) and two actual sandstone samples (about 4 and 64 million voxels respectively). The code is validated against a Matlab serial implementation, showing a significant improvement in efficiency. Remarkable test cases of several millions of voxels were afforded, overcoming the memory and execution slowness issues. Moreover, the proposed implementation is suitable for large pore-scale models run in HPC environments.

3D geological and petrophysical modeling of Alam El-Bueib Formation using well logs and seismic data in Matruh Field, northwestern Egypt

There are several productive petroleum fields in the North Western Desert (WD) of Egypt, which received extensive investigations regarding their petroleum potential. However, a few studies tackled the Matruh Oil Field, which contains the oil prolific Early Cretaceous Alam El-Bueib Formation (AEB Fm) reservoir. The reservoir intervals of the AEB Fm show substantial lithological variations across the basin. Therefore, it is necessary to analyze the vertical and lateral distributions in terms of their lithological and petrophysical properties. To achieve this objective, wireline logs of four wells and 20-2D seismic lines were used to construct a depth-structure contour map for the studied part of the field. This map was used to build the field’s structure model and to identify the fault patterns in the basin through several seismic lines. Analyses of well logs data and lithology were used to estimate the petrophysical properties of AEB sandstone units AEB-1, AEB-3A, AEB-3C, and AEB-6. Results show that the AEB-6 Unit is the most promising hydrocarbon-bearing unit. It has a net pay of 20–160 feet, a shale volume of 5–20%, an effective porosity of 14–20%, and a hydrocarbon saturation of 70–88%. The structure-depth maps indicate a number of normal faults with two principal NE-SW and NW–SE trends, which probably act as structural traps in the Matruh Oil Field. The constructed structure-depth maps and calculated petrophysical parameters were used to build a three-dimensional reservoir model. A blind well was used to validate the accuracy and reliability of the facies, porosity, and saturation models for the AEB Fm units, ensuring a good match between log-derived data and built models. The AEB Fm shows regional heterogeneous variations in its petrophysical characteristics. It exhibits unconventional reservoir characteristics in a N–S direction and conventional reservoir characteristics in an E–W direction. This observed heterogeneity shows the need to carry out further investigations to comprehensively assess the hydrocarbon potential of AEB Fm in different areas of the Matruh Basin.

Ductile rupture under cyclic loadings at high triaxiality: The influence of strain hardening and elasticity

Previous works (Devaux et al., 1997; Cheng et al., 2017) have emphasized the effects of strain hardening and elasticity upon ductile rupture of metals under cyclic loading conditions. This work pursues the study and modelling of these two effects by distinct theoretical methods, each coupled with micromechanical finite element simulations of the behaviour of some “representative cell”. For the effect of strain hardening, we employ Morin et al. (2017)’s approach, based on the theory of sequential limit-analysis (Yang, 1993; Leu, 2007; Leblond et al., 2018). This approach is applied to various types of hardening of the metallic matrix: isotropic, linear kinematic, nonlinear kinematic with one or two kinematic variables (Armstrong and Frederick, 2007) , and even a simplified version of Chaboche (1991)’s model accounting for complex cyclic effects. Numerical micromechanical simulations of a hollow sphere made of elastic–plastic materials obeying the various hardening laws considered, and subjected to cyclic loadings at high triaxiality, fully confirm the predictions of the model developed, provided elasticity is made negligible by using an artificially high value of Young’s modulus. When a realistic value is employed, however, the agreement between theoretical predictions and numerical results is degraded, thus emphasizing again the importance of the effect of elasticity in cyclic ductile rupture. To deal with this effect we derive, apparently for the first time, an evolution equation of the porosity accounting for (compressible) elasticity. However, numerical micromechanical simulations reveal that simply using this new evolution law, while keeping all other aspects of the model unchanged, remains insufficient to get a good match of theoretical and numerical results. Such a match is achieved by introducing the ad hoc hypothesis that the yield criterion and flow rule derived from sequential analysis still apply in the presence of elasticity, but with some “effective porosity” slightly differing from the true one through some heuristic, adjustable factor.

Rock weathering: The effects of varying rock moisture on controlled weathering cycles in low porosity limestone

Examples of rockwall weathering processes include diurnal heating and cooling, diurnal and seasonal freezing, wetting and drying and thawing/seasonal active-layer thawing. These stress-loading processes often occur synergistically and cause a weakening of the rockwall through the propagation of sub-critical cracks. The Acoustic Emissions (AE) released by these cracking events can be measured in order to quantify the weathering efficacy. While the effects of thermal cycling are well studied, rock moisture content and its control on these weathering processes is rarely considered in detail.To better understand rock moistures effect on weathering processes we subjected Wetterstein limestone samples with different starting moisture contents (0 %, 25 %, 50 %, 75 %, 100 %) to thermal cycling above (5 to 35 °C) and below (5 to −10 °C) freezing and a longer freezing cycle with gradual stepped thawing (10 to −10 °C). In addition to this we simulated wetting and drying cycles at a constant temperature. For all of these weathering cycles, relative efficacy was assessed by amount of AE hits and change in effective porosity.Rock moisture was found to have little effect on the overall AE count and effective porosity increase over shorter thermal cycling. However, freeze-thaw cycling was shown to have similar weathering effect to thermal cycling of 3 K greater thermal gradient above freezing. Meanwhile longer duration freezing cycles see an increase of rock moisture create 4× as many cracking events compared to dry samples. More re-freezing events are seen in lower saturation samples and when considered with the synergistic effects of wetting and drying in natural open systems, the presence and mobility of pore water are considered to be more important than the quantity.

Petrographical and petrophysical rock typing for flow unit identification and permeability prediction in lower cretaceous reservoir AEB_IIIG, Western Desert, Egypt

The primary objective of this study is to identify and analyze the petrophysical properties of the newly investigated AEB_IIIG member reservoir in Meleiha West Deep (MWD) Field and to classify it into different rock types. Additionally, this research intends to develop mathematical equations that may be utilized to estimate permeability in uncored sections of the same well or in other wells where core samples are unavailable. The analysis focused on the pore hole records of ten wells that were drilled in MWD Field. The reservoir levels were identified, and their petrophysical parameters were evaluated using well logs and core data. We were able to recognize seven different types of rocks (petrophysical static rock type 1 (PSRT1) to PSRT7) using petrography data, the reservoir quality index (RQI), the flow zone index (FZI), R35, hydraulic flow units (HFUs), and stratigraphy modified Lorenz (SML) plots. The analysis of the petrophysical data shows that AEB_IIIG has unsteady net pay thicknesses over the area. It has a range of 8–25% shale volume, 12–17% effective porosity, and 72–92% hydrocarbon saturation. The RQI results show that psrt1, psrt2 and psrt3 have a good reservoir quality as indicated by high R35 and helium porosity, respectively. They contribute with more than 75% of the reservoir production. The equation derived for each rock type of AEB_IIIG reservoir can be employed to forecast the permeability value distribution inside the reservoir.

Reservoir Quality, Lithotype Assessment, and Geochemical Source Rock Analysis: Insights from Well Logs and Pyrolysis Data, Karama Field, North-Western Desert, Egypt

Reservoir characteristics and source rock geochemistry are essential for petroleum system investigation as they reveal reservoir quality and hydrocarbon generation capability, respectively. The primary Karama oil field reservoir of Abu El Gharadig Basin is the limestone-sand-shale Abu Roash G (AR/G) Member. This study examines AR/G, analyzes source rocks for maturity and organic elements, and defines the main reservoir lithotypes and evaluates reservoir properties. Five well log datasets and an AR/F pyrolysis analysis on another well were used in this study to characterize the AR/G’s 168-foot effective thickness and assess the AR/F source-rock maturation. The effective porosity is up to 30%. The highest shale concentration was 24% in central and western parts of the field. Therefore, drilling development wells in this area, especially east and north, demands caution. The composition and vertical and lateral lithofacies variations of the defined reservoir in the Karama field region are a significant control of its petrophysical properties. The pyrolysis of AR/F revealed 1.32–5.84% content of organic matter. That content qualifies AR/F as a hydrocarbon source if thermal maturity is reached. Type I and type II kerogen in the Abu Roash F Member suggests oil production. The Abu Roash G Member and Upper Bahariya (UB) formation produce oil and gas due to their own type II and III kerogen. GC biomarker data suggests that the research area is predominantly maritime, with most samples showing environmental degradation. The area under consideration has one reservoir, AR/G, and three members of source rocks in AR/F&G and UB. AR/G electrofacies revealed various lithotypes and flow units.

Determine the Reservoir Characterization, Using Seismic Data, Well Logs, Attribute Interpretation, and Static Modelling in the Duhok Province, Kurdistan Region, Iraq

Although the High Folded Zone in the Kurdistan Region of Iraq forms part of the Zagros-Taurus Folds and Thrust belt considered one of the potential hydrocarbon provinces, the oil fields within the zone are still lacking in geophysical exploration and scientific research. So, the rationale behind this study is the prospecting and evaluation of one of the Tertiary carbonate reservoirs at the “WN” oil field in the Duhok area by integrating the 3D seismic and well-log data. The methodology covered seismic interpretation, well logs and their relevant petrophysical analysis, attribute computation, and 3D static property modeling. The constructed reservoir maps revealed a double-plunging rollover anticlinal structure trending in the East-West direction parallel to the Taurus Mountain series. A total of nineteen minor reversal faults trending E-W to ENE-WSW dissecting the northern limb of the anticline were manually interpreted. The isopach map shows various thicknesses ranging from 160 to 330 m, averaging 245 m. The property models show the limited values of their parameters as the effective porosity is limited (0.97-23%), the secondary porosity (0.43-11.7%), permeability (0.00-238.8 mD), the water saturation (12.44-99.8%), and the clay volume (0.00-9.8%). The results of this research indicate that the horizon is a promising reservoir characteristic.

Disentangling slope‐scale spatial variability of saturated hydraulic conductivity in the black soil region of northeast China using noise‐assisted multivariate empirical mode decomposition

AbstractReliable estimates of saturated hydraulic conductivity (Ks) are usually difficult to obtain, as Ks is regulated by a variety of soil processes acting at different spatial scales that may obscure each other's impacts. We hypothesized that these scale‐specific relationships could be well characterized with the aid of the noise‐assisted multivariate empirical mode decomposition (NA‐MEMD), thereby serving as a solid foundation for an accurate Ks prediction. The objective was to evaluate whether the incorporation of NA‐MEMD could improve the estimation of Ks based on the multiscale associations it unraveled. On a typical slope transect of 860 m in the black soil region of northeast China, Ks, mollic epipedon thickness, bulk density, soil organic carbon content, total (ϕ) and effective porosities (ϕe), and particle size distribution were investigated at every 20 m. Prior to NA‐MEMD, Ks was most strongly correlated with ϕe, and the linear regression models based on ϕe solely were satisfactory for Ks estimation at the scale of investigation. Adding other predictors significantly improved Ks prediction in calibration, but impaired it in validation. Upon decomposition by NA‐MEMD, Ks was found to be significantly associated with each attribute at two scales of oscillation at least. Summing up the estimates of each Ks component derived from the properties at the equivalent oscillation scales, the results outperformed the traditional multiple linear regressions made at the investigation scale, when the same sets of predictors were used. The application of NA‐MEMD, moreover, could save the tedious measurements of ϕe and ϕ. Excluding these two porosity‐related properties, Ks estimates obtained by incorporating NA‐MEMD were statistically similar or even better than those involving them before NA‐MEMD. These findings demonstrate the great potential of NA‐MEMD in untangling scale‐dependent relationships of Ks with various processes and hold important implications for future estimations of Ks and other hydraulic properties in the black soil region of northeast China and similar regions.

Water transport and porosity trends of concrete containing integral additions of raw-crushed wind-turbine blade

Raw-Crushed Wind-Turbine Blade (RCWTB) is a novel material from the recycling and non-selective crushing of wind-turbine blades composed of fiberglass-composite fibers and polyurethane and balsa-wood particles. This research evaluates for the first time the water-transport and porosity behaviors of concrete with RCWTB through water-penetration-under-pressure, full-immersion water-absorption, capillarity-water-absorption and mercury-intrusion-porosimetry tests. RCWTB contents of 1.5%, 3.0%, 4.5%, and 6.0% were considered. All the RCWTB concretes yielded adequate results for depth of water penetration under pressure and water-absorption rate, although this waste slightly worsened both properties. RCWTB also increased the proportion of pores between 100 and 250 nm in size, which increased total and capillary effective porosities to maximum values of 13.54% and 13.51%, respectively, and sharply decreased the compression-related mechanical properties of concrete. Capillary effective porosity included the porosity effect of balsa-wood particles on concrete mechanical performance, so it allowed estimating the compression-related mechanical properties with a deviation lower than ±10%.

Gray correlation analysis between mechanical performance and pore characteristics of permeable concrete

Pervious concrete is a type of sustainable construction material used in pavement engineering due to its advantages in water permeability, skid resistance, and sound absorption performance. This study investigated the pore characteristics of five types of pervious concrete, along with the uniaxial compression behaviors and semi-circular bending (SCB) fracture performance. The critical stress intensity factor was obtained using the equivalent energy approach. Gray relational analysis was conducted between the mechanical performance and the pore characteristics. Pore indicators include the effective porosity, 2D porosity along the specimen height, 2D coordination number (CN) along the specimen height, 2D pore radius, 2D specific surface area, 3D CN, 3D pore radius, and 3D virtual porosity. Results indicated that from M1 to M3, when cement mortar content decreased from 520 kg/m3 to 408 kg/m3, the effective porosity increased from 18.95% to 27.43%, and the compressive strength and fracture toughness decreased obviously. For the same type of pervious concrete mixture, with the increase of notch length, the critical stress intensity factor decreased accordingly. The 2D porosity distribution, 2D pore size distribution, and 2D CN distribution presented a symmetrical trend of decreasing, then increasing, and then decreasing with the increase of specimen height. Aggregate with the gradation within the range of 9.5 mm to 19.0 mm generated a higher compressive strength, larger effective porosity and larger pore size compared to the gradation of 4.75 mm∼9.5 mm. The results of CN and pore radius generated from the 3D pore network model were larger than the corresponding 2D values. The gray correlation analysis revealed that 2D pore radius and 3D pore radius played critical effects on the uniaxial compressive strength and fracture resistance, while 2D CN and 3D CN were the least significant factors affecting the mechanical performance.

Bone cell response to additively manufactured 3D micro-architectures with controlled Poisson's ratio: Auxetic vs. non-auxetic meta-biomaterials

The Poisson's ratio and elastic modulus are two parameters determining the elastic behavior of biomaterials. While the effects of elastic modulus on the cell response is widely studied, very little is known regarding the effects of the Poisson's ratio. The micro-architecture of meta-biomaterials determines not only the Poisson's ratio but also several other parameters that also influence cell response, such as porosity, pore size, and effective elastic modulus. It is, therefore, very challenging to isolate the effects of the Poisson's ratio from those of other micro-architectural parameters. Here, we computationally design meta-biomaterials with controlled Poisson's ratios, ranging between -0.74 and +0.74, while maintaining consistent porosity, pore size, and effective elastic modulus. The 3D meta-biomaterials were additively manufactured at the micro-scale using two-photon polymerization (2PP), and were mechanically evaluated at the meso‑scale. The response of murine preosteoblasts to these meta-biomaterials was then studied using in vitro cell culture models. Meta-biomaterials with positive Poisson's ratios resulted in higher metabolic activity than those with negative values. The cells could attach and infiltrate all meta-biomaterials from the bottom to the top, fully covering the scaffolds after 17 days of culture. Interestingly, the meta-biomaterials exhibited different cell-induced deformations (e.g., shrinkage or local bending) as observed via scanning electron microscopy. The outcomes of osteogenic differentiation (i.e., Runx2 immunofluorescent staining) and matrix mineralization (i.e., Alizarin red staining) assays indicated the significant potential impact of these meta-biomaterials in the field of bone tissue engineering, paving the way for the development of advanced bone meta-implants. Statement of significanceWe studied the influence of Poisson's ratio on bone cell response in meta-biomaterials. While elastic modulus effects are well-studied, the impact of Poisson's ratio, especially negative values found in architected biomaterials, remains largely unexplored. The complexity arises from intertwined micro-architectural parameters, such as porosity and elastic modulus, making it challenging to isolate the Poisson's ratio. To overcome this limitation, this study employed rational computational design to create meta-biomaterials with controlled Poisson's ratios, alongside consistent effective elastic modulus, porosity, and pore size. The study reveals that two-photon polymerized 3D meta-biomaterials with positive Poisson's ratios displayed higher metabolic activity, while all the developed meta-biomaterials supported osteogenic differentiation of preosteoblasts as well as matrix mineralization. The outcomes pave the way for the development of advanced 3D bone tissue models and meta-implants.

Anisotropic dynamic permeability model for porous media

Based on the tortuous capillary network model, the relationship between anisotropic permeability and rock normal strain, namely the anisotropic dynamic permeability model (ADPM), was derived and established. The model was verified using pore-scale flow simulation. The uniaxial strain process was calculated and the main factors affecting permeability changes in different directions in the deformation process were analyzed. In the process of uniaxial strain during the exploitation of layered oil and gas reservoirs, the effect of effective surface porosity on the permeability in all directions is consistent. With the decrease of effective surface porosity, the sensitivity of permeability to strain increases. The sensitivity of the permeability perpendicular to the direction of compression to the strain decreases with the increase of the tortuosity, while the sensitivity of the permeability in the direction of compression to the strain increases with the increase of the tortuosity. For layered reservoirs with the same initial tortuosity in all directions, the tortuosity plays a decisive role in the relative relationship between the variations of permeability in all directions during pressure drop. When the tortuosity is less than 1.6, the decrease rate of horizontal permeability is higher than that of vertical permeability, while the opposite is true when the tortuosity is greater than 1.6. This phenomenon cannot be represented by traditional dynamic permeability model. After the verification by experimental data of pore-scale simulation, the new model has high fitting accuracy and can effectively characterize the effects of deformation in different directions on the permeability in all directions.

Geochemistry and Reservoir Properties of the Upper Jurassic Formations, in Selected Oilfield Central Iraq

Geochemical analysis of subsurface organic matter in the most productive source rocks, the Sargelu and Naokelekan formations, has provided insight into the potential of hydrocarbon production in the Jurassic strata of the selected oil field in central Iraq.The aim of this study is to conclude if the source rock can provide reservoir properties such as porosity and permeability. This attempt is made to support petroleum production from both reservoir and source rocks. The cause of this idea was adopted due to some of very good source rock were kept the produced hydrocarbons within the thin impermeable layers.Rock Eval pyrolysis returned high total organic carbon ranging from 0.55 to 34.82 wt%, Type II kerogen with a hydrogen index of up to 368 mg HC/gTOC, and a rock potential of 0.58 to 50.9 kghc/ton rock. Mature organic material was found in both formations, with a Tmax between 434 and 450 °C. This study of source rock properties shows that the rocks have good properties that need to be considered as the Sargelu and Naokelekan formations are the main sources of hydrocarbons in the studied area.The multi-story source-reservoir rocks are represented in this secession. The reservoir properties of the Naokelekan Formation are impressive in that it can draw crude oil from the underlying Sargelu Formation, which produces oil and releases it into the local petroleum system. The effective porosity in the Naokelekan Formation reached 14% in the main reservoir area, while permeability values mostly reached 4 mD. This indication potentially underscores the objective of this study to upgrade the oil-producing source rock into reservoir intervals.

Well Logs Analysis and Reservoir Evaluation of Hartha Formation in the East Baghdad oil field central Iraq

This study objective of ascertaining various petrophysical properties, which encompass volume shale, porosity, and water saturation. Well logging assumes a pivotal role in the comprehensive evaluation of reservoirs by providing measurements that can be effectively correlated with the volume fraction and composition of hydrocarbons within porous geological formations.In the course of this research, the quantification of shale volume was achieved through the utilization of gamma-ray logs, while the determination of effective porosity was facilitated by employing porosity logs, including the density log, neutron log, and sonic or acoustic log. The Hartha Formation has been stratified into distinct reservoir units based on their petrophysical characteristics. The interpretation of the findings involved the direct examination of well log readings, complemented by the application of well-established relationships and profiles to discern the critical lithological and petrophysical attributes inherent to the Hartha Formation. The selected wells from the East Baghdad oilfield, namely EB-93, EB-97, EB-51, and EB-42.

Well Logs Analysis and Petrophysical Properties of Shiranish Formation in the East Baghdad Oil Field, Central Iraq

The objective of this study is to characterize of the petrophysical properties of Shiransih Formation in East Baghdad oilfield. The analysis involves both of examination of Well Log data obtained from specific wells, namely EB-86, EB-84, EBSK-10-4, EBSK8-2, and EBSK-5-4. The Gamma Ray Log is utilized to quantify volume of shale within the formation, while Porosity Logs, including Density Log, Neutron Log, and Sonic Log, are employed to determine effective porosity and index secondary porosity. Water saturation, movable hydrocarbon, and residual hydrocarbon are calculated using Resistivity logs (LLd, MSFL, and ILD). Additionally, a cross-plot analysis is performed utilizing Density Log and Neutron Log to determine the lithology of the Shiransih Formation.

Integrating Well Logs and Core Data for Better Reservoir Characterization of Mamuniyat Formation, Murzuq Basin, Libya

Increasing the number of dry holes in the last two decades to more than twenty wells in Murzuq Basin necessitates a comprehensive reservoir evaluation study to resolve this issue. The current work combines well logging and core data analysis to precisely estimate petrophysical parameters and evaluate the Mamuniyat reservoir. The available data includes well logs from eleven wells and core data from one of the studied wells (I-14 Well). Utilizing well logs and core data, the Mamuniyat Formation is found to be made up of sandstone with a low shale content between 5 and 10%. It has effective porosity values that vary between moderate (13%) and good (16%), with oil saturation ranging from 62 to 91%. Using core data analysis, it was found that the grain density is 2.65 g/cc. A good match between the core-derived and log-derived porosity values is observed. It could be concluded that the Mamuniyat Formation is a sandstone reservoir with low shale volume, moderate effective porosity, and high oil saturation. The reason for the large number of dry holes in Murzuq Basin could be attributed to other factors other than reservoir quality.

Evaluation of Saturation Interpretation Methods for Ultra-Low Permeability Argillaceous Sandstone Gas Reservoirs: A Case Study of the Huangliu Formation in the Dongfang Area

Ultra-low permeability argillaceous sandstone reservoirs have become a significant focus for exploration and development. Saturation is a crucial parameter in evaluating such reservoirs. Due to the low porosity, low permeability, complex pore structure, and strong heterogeneity in ultra-low permeability argillaceous sandstone reservoirs, traditional evaluation methods are unable to achieve the required level of interpretation accuracy. To improve the accuracy of gas saturation calculations in ultra-low permeability argillaceous sandstone gas reservoirs, the conductivity characteristics of the ultra-low permeability argillaceous sandstone gas reservoirs in the Huangliu Formation in the Dongfang area, China, were analyzed through rock physics experimental data and geological information. The results revealed the clay content in the study area to range from 6% to 33.4%. Influenced by burial depth and temperature, kaolinite and montmorillonite transform into illite and chlorite, and the cation exchange capacity is not correlated with the clay content. This suggests that the effects of cation-attached conductivity can be ignored. The regional variation in rock electrical parameters is significant. When the lithology coefficient is a = 1, the consolidation index m varies between 1.25 and 1.75. When the lithology coefficient is b = 1, the saturation index n varies between 1.6 and 1.96. Under the influence of high temperature and pressure, the reservoirs in the study area exhibit two distinct characteristics on the capillary pressure curve, fractal dimension, and effective porosity index intersection diagram, (1) In Class I reservoirs, there is a strong correlation between the formation factor and natural gamma, as well as porosity, and a logarithmic relationship between the saturation exponent and the formation factor; and (2) in Class II reservoirs, there is a strong power-law relationship between the formation factor and porosity, as well as a logarithmic relationship between the saturation exponent and formation factor. Based on experimental and logging data, reservoir classification was conducted using core-scale logging and principal component analysis. Additionally, a saturation interpretation model was developed using multivariate regression, based on rock electrical parameters. The actual application results demonstrate that compared to the fixed rock resistivity saturation model, this model has reduced the average absolute error by 5.9%. The calculated values are consistent with the gas saturation analysis of the core at the pure gas section as determined by cable testing sampling. This model meets the requirements of practical production. The study of this interpretation method is of great significance for the formulation of development plans for ultra-low permeability offshore argillaceous sandstone gas reservoirs.

Unlocking the hydrocarbon potential: Formation evaluation and petrophysical properties of the upper Triassic Kurra Chine Formation in Sarta Oil Field, Kurdistan Region, Northern Iraq

The Upper Triassic Kurra Chine Formation in the Sarta oil field of the Kurdistan Region of Northern Iraq has garnered limited attention, notwithstanding the keen interest of numerous international oil companies in drilling wells within this geological epoch. This study endeavors to thoroughly investigate the Formation Evaluation and petrophysical properties of the Kurra Chine Formation in the production oil field, with a specific focus on Sarta Well-2 (S-2). The research incorporates diverse methods for formation evaluation and analysis of petrophysical properties, employing conventional wireline logs such as Gamm-Ray, Neutron, Density, Sonic, Resistivity, Caliper, and Bit size.The research findings reveal that the thickness of the Kurra Chine Formation in S-2 is approximately 380 m. The pay zones of S-2 exhibit an average shale volume of 17 %. The dominant lithology in S-2 comprises Limestone, Dolomite, Anhydrite, Shale, and Sandstone. The average total porosity within the pay zones is determined to be 6 % in S-2. Furthermore, the average effective porosity in reservoir zones of the S-2 is estimated to be 5 %, while the average secondary porosity in these zones is found to be 6 % in S-2. The average permeability in the pay zones of the Sarta well is reported to be 30.6 millidarcy (mD). Additionally, the average water saturation in the pay zones is determined to be 35 % in S-2, whereas the average hydrocarbon saturation is estimated to be 45 % in S-2.This study furnishes comprehensive descriptions and analyses of the formation evaluation and petrophysical properties of the Kurra Chine Formation in Northern Iraq, shedding light on the characteristics and potential of this oil-bearing formation.

A novel four phase slug single-well push–pull test with regional flux: forward modeling and parameter estimation

The single-well push–pull (SWPP) test has been widely used for several applications, including determination of transport parameters such as regional groundwater flux velocity, effective porosity and dispersivity. A complete SWPP test usually includes four phases of injection, chase, rest, and extraction, while previous models mostly ignore the chase phase for the sake of simplification. Actually, the chase phase is important to minimize the impact of well skins and wellbore storage on the shape of the breakthrough curves (BTCs), thus is necessary and should be included in the model. To this end, two simplified methods are proposed in this study based on two different time tp and ta during a four-phase SWPP test to estimate the parameters related to transport, where tp and ta correspond to the time of the peak concentration during the injection phase and the time when the center of tracer mass returns to the wellbore during the extraction phase, respectively. Specifically, the tp method can be used to estimate the regional groundwater flow velocity and dispersivity (transverse and longitudinal), while the ta method is used to estimate the regional groundwater flow velocity and the effective porosity. Finite-element numerical modeling of the SWPP test based on the coupling of two-dimensional transient groundwater flow and solute transport is employed to test the applicability of the proposed methods. Results indicate that both the tp and ta methods proposed in this study perform satisfactorily in estimation of regional groundwater flow velocity, effective porosity and dispersivity, and these two methods require fewer observations than traditional curve fitting methods and do not require any optimization algorithms. We have also compared the proposed two methods with several previous methods, and conclude that these two new methods generally perform better than those of previous studies in terms of parameter estimation reliability.

3D modelling of the hydraulic performance of open-graded asphalt using the DEM and CFD methods

In this study, we propose a modelling approach that combines computational fluid dynamics (CFD) and the discrete element method (DEM) to simulate the hydraulic performance of three-dimensional (3D) porous asphalt (PA) specimens. Initially, realistic aggregate appearances are captured through the image analysis technique. This information is then transferred to DEM software for the reconstruction of pore structure with distinct aggregate shapes following the real particle size distribution (PSD) as identified by local construction standards. The pore structure, reproduced via DEM, is used as input for CFD simulation to assess the hydraulic performance. To capture the dynamic of water motion simulation, the multiphase model, volume of fluid method (VOF), within CFD is applied to track and predict the interactions between different material phases, and the effect of porous structure to the hydraulic behaviour and performance. Results of numerical simulations indicate that PA samples with higher total porosity (air voids) have better pore connectivity and more effective porosity. For samples with the total porosity of 20%, the difference between the total porosity and the effective porosity was 14.8%; while a much lower difference of 8.3% was found for the higher porosity (25%) specimen. Compared with effective porosity, the reduction in active porosity reaches 58.8% in deeper layers for the sample at 20% total porosity, and only 32.2% for the sample at 25% total porosity. Overall, the results show that there is about a 4.57 times difference in hydraulic performance represented by mass flow rate among PA samples with 5% total porosity difference.