Analytical Model for Estimation of Pore Volume to Breakthrough in Carbonate Acidizing with Organic and Mineral Acids

2021 ◽  
Author(s):  
Sina Lohrasb ◽  
Radzuan Junin ◽  
Augustine Agi ◽  
Mohd Zaidi Jaafar ◽  
Afeez Gbadamosi ◽  
...  
Keyword(s):  
Empirical Model ◽  
Pore Volume ◽  
Reaction Rates ◽  
Coefficient Of Determination ◽  
Oil Well ◽  
Treatment Technique ◽  
Carbonate Formation ◽  
Carbonate Cores ◽  
Experimental Works ◽  
Carbonate Acidizing

Abstract Acidizing is one of the most useful methods in the oil well stimulations. This treatment technique creates capillary wormholes in the carbonate formations to enhanced fluids flow production of a reservoir. One of the main indexes for recognizing the wormhole characterization is the pore volume to breakthrough number. Therefore, calculating this number is one of the main goals in the carbonate acidizing. Obtaining this number is always required for experimental works, which needs time, energy and cost. In this article, an empirical model was used to evaluate carbonate acidizing procedure in the limestone and dolomite cores as the carbonate cores. This empirical model measures the number of wormholes formed in the carbonate cores after acid injection by using the conservation of mass law. In this method, the transport relative reaction rates of acid and core inside the structure of wormhole was maintained during the wormhole creation process. Growing the wormhole in the carbonate formation was developed step by step. Changes in acid concentration as an injected fluid flow were accounted for in this empirical model. Also, the changes in carbonate porosity, the effect of Damköhler number, and injection rate were included in the model. Two types of carbonate rocks and five types of acids with different molar masses were used in this model for the analysis and validation of the model. The results from experimental works was significance and justifies the use of use of the law for mass transport and chemical reactions. Evaluation of the developed model with other experimental and numerical results gave an excellent assessment of 95.45% for the average accuracy and 0.9933 for the average coefficient of determination. Therefore, an empirical technique to approximate the pore volumes to breakthrough number in the limestone and dolomite cores with high accuracy using physical core and acid properties is proposed.

scholarly journals Empirical Model of Human Thermal Comfort in Subtropical Climates: A First Approach to the Brazilian Subtropical Index (BSI)

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 391 ◽  
Author(s):  
João Gobo ◽  
Marlon Faria ◽  
Emerson Galvani ◽  
Fabio Goncalves ◽  
Leonardo Monteiro
Keyword(s):  
Thermal Comfort ◽  
Empirical Model ◽  
Thermal Sensation ◽  
Meteorological Data ◽  
Well Being ◽  
Global Solar Radiation ◽  
Coefficient Of Determination ◽  
Subtropical Climate ◽  
Human Thermal Comfort ◽  
The City

The bioclimatic well-being of individuals is associated with the environmental characteristics of where they live. Knowing the relationships between local and regional climatic variables as well as the physical characteristics of a given region and their implications on thermal comfort is important for identifying aspects of thermal sensation in the population. The aim of this study is to develop an empirical model of human thermal comfort based on subjective and individual environmental patterns observed in the city of Santa Maria, located in the state of Rio Grande do Sul, Brazil (Subtropical climate). Meteorological data were collected by means of an automatic meteorological station installed in the city center, which contained sensors measuring global solar radiation, air temperature, globe temperature (via a grey globe thermometer), relative humidity and wind speed and direction. A total of 1720 people were also interviewed using a questionnaire adapted from the model recommended by ISO 10551. Linear regressions were performed to obtain the predictive model. The observed results proposed a new empirical model for subtropical climate, the Brazilian Subtropical Index (BSI), which was verified to be more than 79% accurate, with a coefficient of determination of 0.926 and an adjusted R2 value of 0.924.

scholarly journals Kinetics of saccharose fermentation by Kombucha

2014 ◽  
Vol 20 (3) ◽  
pp. 345-352 ◽  
Author(s):  
Eva Loncar ◽  
Katarina Kanuric ◽  
Radomir Malbasa ◽  
Mirjana Djuric ◽  
Spasenija Milanovic
Keyword(s):  
Empirical Model ◽  
Black Tea ◽  
Reaction Rates ◽  
Yeast Cells ◽  
Inoculum Concentration ◽  
Viable Cells ◽  
Rate Of Reaction ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Very High

Kinetics of saccharose fermentation by Kombucha is not yet well defined due to lack of knowledge of reaction mechanisms taking place during this process. In this research kinetics of saccharose fermentation by Kombucha was analysed using the suggested empirical model. The data were obtained on 1.5 g L-1 of black tea, with 66.47 g L-1 of saccharose and using 10% (v/v) or 15% (v/v) of Kombucha. Total number of viable cells was as follows: approximately 5x105 of yeast cells per mL of the inoculum and approximately 2x106 of bacteria cells per mL of the inoculum. The samples were analysed after 0, 3, 4, 5, 6, 7 and 10 days. Their pH values and contents of saccharose, glucose, fructose, total acids and ethanol were determined. A saccharose concentration model was defined as sigmoidal function at 22oC and 30oC, and with 10% (v/v) and 15% (v/v) of inoculum quantity. Determination coefficients of the functions were very high (R2>0.99). Reaction rates were calculated as first derivatives of Boltzmann?s functions. No simple correlation between rate of reaction and independent variables (temperature and inoculum concentration) was found. Analysis of empirical model indicated that saccharose fermentation by Kombucha occurred according to very complex kinetics.

scholarly journals Direct Mass Spectrometry with Online Headspace Sample Pretreatment for Continuous Water Quality Monitoring

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1843
Author(s):  
Sun-Hong Lee ◽  
Eun-Ji Shin ◽  
Kyung-Duk Zoh ◽  
Youn-Seok Kang ◽  
Jae-Won Choi
Keyword(s):  
Mass Spectrometry ◽  
Water Quality ◽  
Detection Limit ◽  
Field Experiments ◽  
Water Quality Monitoring ◽  
Reaction Rates ◽  
Coefficient Of Determination ◽  
Gas Chromatography Mass Spectrometry ◽  
High Concentration ◽  
Selected Ion Flow Tube

This study investigates the use of selected ion flow tube mass spectrometry with an automated headspace pretreatment system for the continuous surveillance of water quality at wastewater treatment plants (WWTPs) and rivers. The reaction rates of the target compounds introduced using the headspace method were similar to those of the mass scan library, with a margin of error of <10%. Novel quantitative formulae were derived for the water samples of the target compounds, and the linearity of the calibration curves for both the purified and effluent matrix (0.1–2.0 mg/L) showed a coefficient of determination of 0.98–0.99 for most compounds. The detection limit for 74% of the target substances was 0.02–0.10 mg/L, and the average recoveries were 111.6% and 104.7% for the low- and high-concentration spiked samples, respectively, which are comparable to those of the headspace gas chromatography-mass spectrometry system. However, the variability in individual concentrations was still large, due to the unstable control of sample injection flow and pressure. Herein, 79% of the 28 compounds met one-tenth of the proposed method detection limit criteria for emergency operations in WWTP. Field experiments showed that the system was easy to maintain and could be used to monitor chemical accidents.

scholarly journals A MODIFIED EMPIRICAL MODEL FOR ESTIMATING THE WETTED ZONE DIMENSIONS UNDER DRIP IRRIGATION

2015 ◽  
Vol 76 (15) ◽  
Author(s):  
Ahmed A. M. Al-Ogaidi ◽  
Aimrun Wayayok ◽  
Md Rowshon Kamal ◽  
Ahmed Fikri Abdullah
Keyword(s):  
Empirical Model ◽  
Drip Irrigation ◽  
Irrigation System ◽  
Model Performance ◽  
Coefficient Of Determination ◽  
Irrigation Systems ◽  
Modified Model ◽  
Model Efficiency ◽  
The Mean ◽  
Statistical Criteria

Drip irrigation system has become one of the most common irrigation systems especially in arid and semi-arid regions due to its advantages in saving water. One of the most essential considerations in designing these systems is the dimensions of the wetted soil volume under emitters. These dimensions are significant in choosing the proper emitter spacing along the laterals and the suitable distance between laterals. In this study, a modified empirical equations for estimating the horizontal and vertical extend of the wetted zone under surface emitters were suggested. Data from published papers includes different conditions of soil properties and emitter discharge were used in deriving the empirical model using the nonlinear regression. The developed model has high value for coefficient of determination, R2. The results from the developed model were compared with results of other empirical models derived by other researchers. Some statistical criteria were used to evaluate the model performance which are the mean error ME, root mean square error RMSE, and model efficiency EF. The results revealed that the modified model showed good performance in predicting the wetted zone dimensions and it can be used in design and management of drip irrigation systems. 

Technique Proves Effective in Remediation of Phase-Trapping Damage in Tight Reservoirs

2021 ◽  
Vol 73 (07) ◽  
pp. 60-61
Author(s):  
Chris Carpenter
Keyword(s):  
Chemical Treatment ◽  
Water Saturation ◽  
Gas Permeability ◽  
Abu Dhabi ◽  
Absolute Permeability ◽  
Treatment Technique ◽  
The Core ◽  
Carbonate Formation ◽  
Irreducible Water Saturation ◽  
Damaged Zone

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 202996, “An Efficient Treatment Technique for Remediation of Phase-Trapping Damage in Tight Carbonate Gas Reservoirs,” by Rasoul Nazari Moghaddam, SPE, Marcel Van Doorn, and Auribel Dos Santos, SPE, Nouryon, prepared for the 2020 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, held virtually 9–12 November. The paper has not been peer reviewed. Aqueous- and hydrocarbon-phase trapping are among the few formation-damage mechanisms capable of significant reduction in effective permeability (sometimes near 100%). In this study, a new chemical treatment is proposed for efficient remediation of water- or hydrocarbon-phase-trapping damage in low-permeability porous media. The method proposed here is cost-effective and experimentally proved to be efficient and long-lasting. Such a chemical treatment is recommended to alleviate gas flow in tight gas with aqueous-trapping-damaged zones or in gas condensate reservoirs with condensate-banking challenges. Introduction Remediation techniques for existing aqueous- or hydrocarbon-phase-trapping damage can be categorized into two approaches: bypassing the damaged region by direct penetration techniques and trapping-phase removal. In the former category, the damaged zone is bypassed by creation of high-conductance flow paths through hydraulic fracturing or acidizing. However, for tight and ultratight formations, conventional acidizing may not be feasible (mostly because of injectivity difficulties). In the second category, direct removal and indirect removal have been used, but usually are seen as short-term solutions. The fluid used in the proposed treatment is comprised of a nonacidic chelating agent. The treatment fluid can be injected safely into the damaged region, while a slow reaction rate allows it to penetrate deep into the formation. In the proposed treatment, the mechanism is the permanent enlargement of pore throats where the nonwetting phase has the most restriction (to overcome the capillary forces) to pass through. In fact, phase trapping or capillary trapping occurs inside the pore structure when viscous forces are not strong enough to overcome the capillary pressure. The experimental setup and method are detailed in the complete paper. Results and Discussion Treatment of Outcrop Samples: Lueder Carbonate. The performance of the proposed treatment fluid initially was investigated on two outcrop core samples from the Lueder carbonate formation. The first treatment was conducted on the Le1 core sample with an absolute permeability of 1.46 md. To establish trapped water in the core, 10 pore volumes (PV) of 5 wt% potassium chloride brine were injected followed by nitrogen (N2) gas displacement. Then, to achieve irreducible water saturation, N2 was injected at a rate of 2 cm3/min for at least 100 PVs until no further water was produced. Next, the effective gas permeability was measured while N2 was injected at approximately 0.2 cm3/min. The effective gas permeability was obtained as 0.042 md. The trapped water saturation was also calculated (from the core weight) as 77.7%. After all pretreatment measurements, the core was loaded into the core holder for the treatment. The treatment injections with preflush and post-flush were performed at 130°C. In this test, 0.5 PV of treatment fluid was injected.

A Robust Rate of Penetration Model for Carbonate Formation

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Ahmad Al-AbdulJabbar ◽  
Salaheldin Elkatatny ◽  
Mohamed Mahmoud ◽  
Khaled Abdelgawad ◽  
Abdulaziz Al-Majed
Keyword(s):  
Compressive Strength ◽  
Drilling Fluid ◽  
Coefficient Of Determination ◽  
Percentage Error ◽  
Drilling Process ◽  
Rate Of Penetration ◽  
New Model ◽  
Carbonate Formation ◽  
Drilling Parameters ◽  
Fluid Properties

During the drilling operations, optimizing the rate of penetration (ROP) is very crucial, because it can significantly reduce the overall cost of the drilling process. ROP is defined as the speed at which the drill bit breaks the rock to deepen the hole, and it is measured in units of feet per hour or meters per hour. ROP prediction is very challenging before drilling, because it depends on many parameters that should be optimized. Several models have been developed in the literature to predict ROP. Most of the developed models used drilling parameters such as weight on bit (WOB), pumping rate (Q), and string revolutions per minute (RPM). Few researchers considered the effect of mud properties on ROP by including a small number of actual field measurements. This paper introduces a new robust model to predict the ROP using both drilling parameters (WOB, Q, ROP, torque (T), standpipe pressure (SPP), uniaxial compressive strength (UCS), and mud properties (density and viscosity) using 7000 real-time data measurements. In addition, the relative importance of drilling fluid properties, rock strength, and drilling parameters to ROP is determined. The obtained results showed that the ROP is highly affected by WOB, RPM, T, and horsepower (HP), where the coefficient of determination (T2) was 0.71, 0.87, 0.70, and 0.92 for WOB, RPM, T, and HP, respectively. ROP also showed a strong function of mud fluid properties, where R2 was 0.70 and 0.70 for plastic viscosity (PV) and mud density, respectively. No clear relationship was observed between ROP and yield point (YP) for more than 500 field data points. The new model predicts the ROP with average absolute percentage error (AAPE) of 5% and correlation coefficient (R) of 0.93. In addition, the new model outperformed three existing ROP models. The novelty in this paper is the application of the clustering technique in which the formations are clustered based on their compressive strength range to predict the ROP. Clustering yielded accurate ROP prediction compared to the field ROP.

Use of X-Ray CT to Measure Pore Volume Compressibility of Shaybah Carbonates

2010 ◽  
Vol 13 (01) ◽  
pp. 155-164 ◽  
Author(s):  
Shameem Siddiqui ◽  
James J. Funk ◽  
Ashraf M. Al-Tahini
Keyword(s):  
Pore Volume ◽  
Triaxial Tests ◽  
Dual Energy Ct ◽  
Ct Scanner ◽  
X Ray ◽  
Volume Compressibility ◽  
Diagenetic Alteration ◽  
Carbonate Formation ◽  
Triaxial Cell ◽  
Pore Volume Compressibility

Summary The Lower Cretaceous Shu'aiba formation (Shaybah field) in southeastern Saudi Arabia is a heterogeneous carbonate formation with various facies because of diagenetic alteration of the original rock fabric. Preliminary laboratory rock-mechanics studies indicated that the Shu'aiba carbonates are mechanically weak, with the majority of the rocks tested yielding very low strength values (less than 3,000 psi) when compared to samples from other carbonate reservoirs (Salamy and Finkbeiner 2002). On the basis of laboratory-derived rock-strength data from triaxial tests, the formation appears to behave in a plastic manner that strengthens the wellbore. To understand the stress behavior of the Shaybah rocks better, a set of pore volume compressibility tests was conducted in which the changes taking place within the samples were observed and quantified using an X-ray computerized-tomography (CT) scanner. A new technique involving dual-energy CT scanning was used to obtain the pore volume compressibility values, which were compared against the conventional triaxial-cell-generated data and published results by Harari et al. (1995) on cores taken from the same reservoir. Although the magnitude of the pore volume compressibility was the same between different setups, visual data showed some interesting behavior of the Shaybah cores including movement of grains in an irreversible manner even for a relatively low imposed effective stress of 2,000 psi. Some of the advantages of the new CT-based analysis technique include the generation of multiple pore volume compressibility curves from the same plug (a band of data, each at a different slice location), the "visualization" of the changes, the possibility of using either hydrostatic or triaxial cells to make the test more case-specific, and the possibility of measuring permeability under different stress conditions before, during, and after the test.

Global analysis of myocardial isotonic shortening: comparison with isometric dynamics

1991 ◽  
Vol 260 (2) ◽  
pp. H486-H498
Author(s):  
O. N. Nwasokwa ◽  
M. M. Bodenheimer
Keyword(s):  
Empirical Model ◽  
Global Analysis ◽  
Model Fit ◽  
Coefficient Of Determination ◽  
Papillary Muscles ◽  
Nonlinear Curve Fitting ◽  
Nonlinear Curve ◽  
Global Parameters ◽  
Isotonic Shortening

Although potentially analytically useful, a global empirical model of the myocardial isotonic curve, L(t), has not been described. We propose the following relation: L(t) = C(t/A)B-1e-(t/A)B, where A, B, and C are global parameters, L is length, and t is time. We evaluated this model in nine in situ canine papillary muscles studied with a servo-system to produce isotonic twitches at different isotonic forces (F). For each twitch, the parameters were determined by nonlinear curve fitting. The model fit the observed curves of L(t) closely, with the coefficient of determination being 0.995 +/- 0.002. C changed with F, but A and B varied little with F, averaging 0.262 +/- 0.021 s and 2.76 +/- 0.17, respectively. Our predictions that A reflects chronotropic, B reflects lusitropic, and C reflects heterotonic (different afterloads) and inotropic states were supported. Comparison done in five muscles showed that A was the same but B was higher for isotonic than for isometric twitches: 0.270 +/- 0.020 vs. 0.264 +/- 0.038 s (P = not significant) for A and 2.79 +/- 0.18 vs. 2.39 +/- 0.05 (P less than 0.008) for B. Dobutamine increased A but not B in isotonic twitches. Thus shortening is lusitropic but leaves no lusitropic reserve to be mobilized by dobutamine. The relation L(t) = C(t/A)B-1e-(t/A)B provides a framework that undergirds global analysis of myocardial shortening and enables comparison with isometric dynamics.

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