Journal of Petroleum Engineering The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. A New Approach in Pressure Transient Analysis: Using Numerical Density Derivatives to Improve Diagnosis of Flow Regimes and Estimation of Reservoir Properties for Multiple Phase Flow Sun, 12 Jul 2015 10:55:26 +0000 This paper presents the numerical density derivative approach (another phase of numerical welltesting) in which each fluid’s densities around the wellbore are measured and used to generate pressure equivalent for each phase using simplified pressure-density correlation, as well as new statistical derivative methods to determine each fluid phase’s permeabilities, and the average effective permeability for the system with a new empirical model. Also density related radial flow equations for each fluid phase are derived and semilog specialised plot of density versus Horner time is used to estimate relative to each phase. Results from 2 examples of oil and gas condensate reservoirs show that the derivatives of the fluid phase pressure-densities equivalent display the same wellbore and reservoir fingerprint as the conventional bottom-hole pressure BPR method. It also indicates that the average effective ranges between 43 and 57 mD for scenarios (a) to (d) in Example 1.0 and 404 mD for scenarios (a) to (b) in Example 2.0 using the new fluid phase empirical model for estimation. This is within the value used in the simulation model and likewise that estimated from the conventional BPR method. Results also discovered that in all six scenarios investigated, the heavier fluid such as water and the weighted average pressure-density equivalent of all fluid gives exact effective as the conventional BPR method. This approach provides an estimate of the possible fluid phase permeabilities and the % of each phase contribution to flow at a given point. Hence, at several stabilisation points, the relative can be generated. Victor Torkiowei Biu and Shi-Yi Zheng Copyright © 2015 Victor Torkiowei Biu and Shi-Yi Zheng. All rights reserved. Analytical Modeling and Contradictions in Limestone Reservoirs: Breccias, Vugs, and Fractures Thu, 30 Apr 2015 11:30:29 +0000 Modeling of limestone reservoirs is traditionally developed applying tectonic fractures concepts or planar discontinuities and has been simulated dynamically without considering nonplanar discontinuities as sedimentary breccias, vugs, fault breccias, and impact breccias, assuming that all these nonplanar discontinuities are tectonic fractures, causing confusion and contradictions in reservoirs characterization. The differences in geometry and connectivity in each discontinuity affect fluid flow, generating the challenge to develop specific analytical models that describe quantitatively hydrodynamic behavior in breccias, vugs, and fractures, focusing on oil flow in limestone reservoirs. This paper demonstrates the differences between types of discontinuities that affect limestone reservoirs and recommends that all discontinuities should be included in simulation and static-dynamic characterization, because they impact fluid flow. To demonstrate these differences, different analytic models are developed. Findings of this work are based on observations of cores, outcrops, and tomography and are validated with field data. The explanations and mathematical modeling developed here could be used as diagnostic tools to predict fluid velocity and fluid flow in limestone reservoirs, improving the complex reservoirs static-dynamic characterization. Nelson Barros-Galvis, Pedro Villaseñor, and Fernando Samaniego Copyright © 2015 Nelson Barros-Galvis et al. All rights reserved. Examination of Experimental Designs and Response Surface Methods for Uncertainty Analysis of Production Forecast: A Niger Delta Case Study Wed, 25 Mar 2015 07:56:52 +0000 The purpose of this paper is to examine various DoE methods for uncertainty quantification of production forecast during reservoir management. Considering all uncertainties for analysis can be time consuming and expensive. Uncertainty screening using experimental design methods helps reducing number of parameters to manageable sizes. However, adoption of various methods is more often based on experimenter discretions or company practices. This is mostly done with no or little attention been paid to the risks associated with decisions that emanated from that exercise. The consequence is the underperformance of the project when compared with the actual value of the project. This study presents the analysis of the three families of designs used for screening and four DoE methods used for response surface modeling during uncertainty analysis. The screening methods (sensitivity by one factor at-a-time, fractional experiment, and Plackett-Burman design) were critically examined and analyzed using numerical flow simulation. The modeling methods (Box-Behnken, central composite, D-optima, and full factorial) were programmed and analyzed for capabilities to reproduce actual forecast figures. The best method was selected for the case study and recommendations were made as to the best practice in selecting various DoE methods for similar applications. Akeem O. Arinkoola and David O. Ogbe Copyright © 2015 Akeem O. Arinkoola and David O. Ogbe. All rights reserved. Asphaltene Formation Damage Stimulation by Ultrasound: An Analytical Approach Using Bundle of Tubes Modeling Tue, 24 Feb 2015 15:34:51 +0000 This study presents a novel approach for bundle of tubes modeling of permeability impairment due to asphaltene-induced formation damage attenuated by ultrasound which has been rarely attended in the available literature. Model uses the changes of asphaltene particle size distribution (APSD) as a function of time due to ultrasound radiation, while considering surface deposition and pore throat plugging mechanisms. The proposed model predicts the experimental data of permeability reduction during coinjection of solvent and asphaltenic oil into core with reasonable agreement. Viscosity variation due to sonication of crude oil is used to determine the fluid mobility applied in the model. The results of modeling indicate that the fluid samples exposed to ultrasound may cause much less asphaltene-induced damage inside the porous medium. Sensitivity analysis of the model parameters showed that there is an optimum time period during which the best stimulation efficiency is observed. The results of this work can be helpful to better understand the role of ultrasound prohibition in dynamic behavior of asphaltene deposition in porous media. Furthermore, the present model could be potentially utilized for modeling of other time-dependent particle induced damages. Arash Rabbani, Mohammad Hossein Ghazanfari, and Mahmood Amani Copyright © 2015 Arash Rabbani et al. All rights reserved. A Comparative Study of Diesel Oil and Soybean Oil as Oil-Based Drilling Mud Wed, 11 Feb 2015 14:11:05 +0000 Oil-based mud (OBM) was formulated with soybean oil extracted from soybean using the Soxhlet extraction method. The formulated soybean mud properties were compared with diesel oil mud properties. The compared properties were rheological properties, yield point and gel strength, and mud density and filtration loss properties, fluid loss and filter cake. The results obtained show that the soybean oil mud exhibited Bingham plastic rheological model with applicable (low) yield point and gel strength when compared with the diesel oil mud. The mud density measurement showed that soybean OBM was slightly higher than diesel OBM with mud density values of 8.10 lb/gal and 7.98 lb/gal, respectively, at barite content of 10 g. Additionally, the filtration loss test results showed that soybean mud fluid loss volumes, water and oil, were 13 mL and 10 mL, respectively, compared to diesel oil mud volume of 15 mL and 12 mL. Furthermore, the filtration loss test indicated that the soybean oil mud with filter cake thickness of 2 mm had a cake characteristic of thin and soft while the diesel oil mud resulted in filter cake thickness of 2.5 mm with cake characteristic of firm and rubbery. In comparison with previous published works in the literature, the soybean oil mud exhibits superior rheological and filtration property over other vegetable oil-based muds. Therefore, the formulated soybean oil mud exhibited good drilling mud properties that would compare favourably with those of diesel oil muds. Its filter cake characteristic of thin and soft is desirable and significant to avert stuck pipe during drilling operations, meaning that an oil-based drilling mud could be formulated from soybean oil. Okorie E. Agwu, Anietie N. Okon, and Francis D. Udoh Copyright © 2015 Okorie E. Agwu et al. All rights reserved. An Integrated Approach for Drilling Optimization Using Advanced Drilling Optimizer Sun, 11 Jan 2015 11:24:15 +0000 The ability to optimize drilling procedures and economics involves simulation to understand the effects operational parameters and equipment design have on the ROP. An analysis applying drilling performance modeling to optimize drilling operations has been conducted to address this issue. This study shows how optimum operational parameters and equipment can be predicted by simulating drilling operations of preexisting wells in a Northwest Louisiana field. Reference well data was gathered and processed to predict the “drillability” of the formations encountered by inverting bit specific ROP models to solve for rock strength. The output data generated for the reference well was formatted to simulate upcoming wells. A comparative analysis was conducted between the predicted results and the actual results to show the accuracy of the simulation. A significant higher accuracy is shown between the simulated and actual drilling results. Once simulations were validated, optimum drilling parameters and equipment specifications were found by varying different combinations of weight on bit (WOB), rotary speed (RPM), hydraulics, and bit specifications until the highest drilling rate is achieved for each well. A qualitative and quantitative analysis of the optimized results was conducted to assess the potential operational and economic benefits on drilling operations. David Hankins, Saeed Salehi, and Fatemeh Karbalaei Saleh Copyright © 2015 David Hankins et al. All rights reserved. Geomechanical Properties of Unconventional Shale Reservoirs Wed, 03 Dec 2014 00:10:00 +0000 Production from unconventional reservoirs has gained an increased attention among operators in North America during past years and is believed to secure the energy demand for next decades. Economic production from unconventional reservoirs is mainly attributed to realizing the complexities and key fundamentals of reservoir formation properties. Geomechanical well logs (including well logs such as total minimum horizontal stress, Poisson’s ratio, and Young, shear, and bulk modulus) are secured source to obtain these substantial shale rock properties. However, running these geomechanical well logs for the entire asset is not a common practice that is associated with the cost of obtaining these well logs. In this study, synthetic geomechanical well logs for a Marcellus shale asset located in southern Pennsylvania are generated using data-driven modeling. Full-field geomechanical distributions (map and volumes) of this asset for five geomechanical properties are also created using general geostatistical methods coupled with data-driven modeling. The results showed that synthetic geomechanical well logs and real field logs fall into each other when the input dataset has not seen the real field well logs. Geomechanical distributions of the Marcellus shale improved significantly when full-field data is incorporated in the geostatistical calculations. Mohammad O. Eshkalak, Shahab D. Mohaghegh, and Soodabeh Esmaili Copyright © 2014 Mohammad O. Eshkalak et al. All rights reserved. How Do Thermal Recovery Methods Affect Wettability Alteration? Sun, 19 Oct 2014 00:00:00 +0000 We will investigate the effect of temperature on wettability. First, we will list and summarize the different schools of thoughts from previous literature describing wettability changes for sandstone and carbonate reservoirs at elevated temperature. Next, we will describe the properties that affect wettability: how they alter wettability and how they are affected by temperature. After that, we will present indications of wettability changes and current wettability measurement techniques. Following this, case studies describing how wettability change influences reservoir characteristics and field performance during thermal recovery processes will be discussed. The thermal recovery methods included in the case studies were steam flooding, cyclic steam injection, hot water flooding, and in situ combustion. The main and very important take away from this study is that temperature induced wettability change is determined by many possible mechanisms combined together and not by just one or two phenomena occurring simultaneously. Finally, we will propose a reasonable scheme for wettability alteration during dry forward combustion, which needs further investigation. Abhishek Punase, Amy Zou, and Riza Elputranto Copyright © 2014 Abhishek Punase et al. All rights reserved. A Novel Method for Improving Water Injectivity in Tight Sandstone Reservoirs Sun, 21 Sep 2014 11:24:05 +0000 Applicability of electrokinetic effect in improving water injectivity in tight sandstone is studied. DC potential and injection rate are varied for optimization and determination of their individual impact on clay discharge and movement. The liberated clays were characterized through size exclusion microfiltration and ICP-MS analysis. Real time temperature and pH monitoring were also informative. Results showed that severalfold (up to 152%) apparent increase of core permeability could be achieved. Some of the experiments were more efficient in terms of dislodgement of clays and enhanced stimulation which is supported by produced brines analysis with higher concentration of clay element. The results also showed larger quantity of clays in the produced brine in the initial periods of water injection followed by stabilization of differential pressure and electrical current, implying that the stimulation effect stops when the higher voltage gradient and flow rates are no more able to dislodge remaining clays. Additionally, fluid temperature measurement showed an increasing trend with the injection time and direct proportionality with the applied voltage. The basic theory behind this stimulation effect is predicted to be the colloidal movement of pore lining clays that results in widening of pore throats and/or opening new flow paths. Mohamad Yousef Alklih, Bisweswar Ghosh, and Emad Waleed Al-Shalabi Copyright © 2014 Mohamad Yousef Alklih et al. All rights reserved. Wettability Effects on Capillary Pressure, Relative Permeability, and Irredcucible Saturation Using Porous Plate Sun, 17 Aug 2014 09:33:02 +0000 An understanding of the mechanisms by which oil is displaced from porous media requires the knowledge of the role of wettability and capillary forces in the displacement process. The determination of representative capillary pressure () data and wettability index of a reservoir rock is needed for the prediction of the fluids distribution in the reservoir: the initial water saturation and the volume of reserves. This study shows how wettability alteration of an initially water-wet reservoir rock to oil-wet affects the properties that govern multiphase flow in porous media, that is, capillary pressure, relative permeability, and irreducible saturation. Initial water-wet reservoir core samples with porosities ranging from 23 to 33%, absolute air permeability of 50 to 233 md, and initial brine saturation of 63 to 87% were first tested as water-wet samples under air-brine system. This yielded irreducible wetting phase saturation of 19 to 21%. The samples were later tested after modifying their wettability to oil-wet using a surfactant obtained from glycerophtalic paint; and the results yielded irreducible wetting phase saturation of 25 to 34%. From the results of these experiments, changing the wettability of the samples to oil-wet improved the recovery of the wetting phase. Olugbenga Falode and Edo Manuel Copyright © 2014 Olugbenga Falode and Edo Manuel. All rights reserved. The Mechanism of Wellbore Weakening in Worn Casing-Cement-Formation System Tue, 24 Jun 2014 00:00:00 +0000 Maintaining casing integrity, in terms of downhole zonal isolations and well stability, is extremely important in oil/gas wells. Casing wear occurs not only in directional drilling, but also in vertical drilling with a slight deviation angle. In most hydrocarbon wells, deteriorated casing was reported from the onset of casing wear by the presence of friction force during the rotation of drillpipe. The friction force against the casing wall causes the reduction of casing strength. Furthermore, the rotation of drillpipe combined with corrosive drilling fluids could dramatically degrade the casing strength. We used a finite element analysis to focus on the stress evolution in worn casings. Comparison study between worn casing and perfect casing was conducted. Our study showed that the thermal load significantly increases the stress concentration of the worn casing in the wellbore. Finite element solutions indicated that the radial stress of the worn casing is not affected as much as the hoop stress. Along with the increased burst pressure or the elevated temperature, the unworn portion of the casing also suffers from severe compression stress. This work is important to broadening the understanding of well engineers through addressing the true stress profile of worn casing in cemented wellbore. Zheng Shen, Frederick E. Beck, and Kegang Ling Copyright © 2014 Zheng Shen et al. All rights reserved. Mysteries behind the Low Salinity Water Injection Technique Sun, 25 May 2014 05:03:16 +0000 Low salinity water injection (LSWI) is gaining popularity as an improved oil recovery technique in both secondary and tertiary injection modes. The objective of this paper is to investigate the main mechanisms behind the LSWI effect on oil recovery from carbonates through history-matching of a recently published coreflood. This paper includes a description of the seawater cycle match and two proposed methods to history-match the LSWI cycles using the UTCHEM simulator. The sensitivity of residual oil saturation, capillary pressure curve, and relative permeability parameters (endpoints and Corey’s exponents) on LSWI is evaluated in this work. Results showed that wettability alteration is still believed to be the main contributor to the LSWI effect on oil recovery in carbonates through successfully history matching both oil recovery and pressure drop data. Moreover, tuning residual oil saturation and relative permeability parameters including endpoints and exponents is essential for a good data match. Also, the incremental oil recovery obtained by LSWI is mainly controlled by oil relative permeability parameters rather than water relative permeability parameters. The findings of this paper help to gain more insight into this uncertain IOR technique and propose a mechanistic model for oil recovery predictions. Emad Waleed Al-Shalabi, Kamy Sepehrnoori, and Gary Pope Copyright © 2014 Emad Waleed Al-Shalabi et al. All rights reserved. CFD Method for Predicting Annular Pressure Losses and Cuttings Concentration in Eccentric Horizontal Wells Thu, 10 Apr 2014 17:39:34 +0000 In oil and gas drilling operations, predictions of pressure losses and cuttings concentration in the annulus are very complex due to the combination of interacting drilling parameters. Past studies have proposed many empirical correlations to estimate pressure losses and cuttings concentration. However, these developed correlations are limited to their experimental data range and setup, and hence, they cannot be applicable to all cases. CFD methods have the advantages of handling complex multiphase flow problems, as well as, an unlimited number of physical and operational conditions. The present study employs the inhomogeneous (Eulerian-Eulerian) model to simulate a two-phase solid-fluid flow and predict pressure losses and cuttings concentration in eccentric horizontal annuli as a function of varying drilling parameters: fluid velocity, diameter ratio (ratio of inner pipe diameter to outer pipe diameter), inner pipe rotation speed, and fluid type. Experimental data for pressure losses and cuttings concentration from previous literature compared very well with simulation data, confirming the validity of the current model. The study shows how reliable CFD methods can replicate the actual, yet complex oil and gas drilling operations. Titus N. Ofei, Sonny Irawan, and William Pao Copyright © 2014 Titus N. Ofei et al. All rights reserved. Investigation of Enhanced Oil Recovery Using Dimensionless Groups in Wettability Modified Chalk and Sandstone Rocks Wed, 26 Mar 2014 07:48:39 +0000 The paper addresses enhanced oil recovery in chalk and sandstone rocks by CO2 injection, with different wettability, porosity, and permeability as well as injection rate and flooding conditions. Results indicate that an increase in Bond number has a positive effect on oil recovery whereas for capillary number, there is a limit in which recovery is improving. This limit is estimated when the pressure drop by viscous force is approximately equal to the threshold balance between capillary and gravity forces. A dimensionless group is proposed that combines the effect of capillarity, injection rate, permeability, and CO2 diffusion on the oil recovery. Recovery from all experiments in this study and reported data in the literature shows a satisfactory relationship with the proposed group. Vahid Alipour Tabrizy Copyright © 2014 Vahid Alipour Tabrizy. All rights reserved. Effect of Polymer Adsorption on Permeability Reduction in Enhanced Oil Recovery Wed, 05 Mar 2014 09:03:43 +0000 In order to reduce the permeability to water or brine, there is a possibility of polymer injection into the reservoir. In the present work, special focus has been paid in polymer [partially hydrolyzed polyacrylamide (PHPA)] injection as a part of chemical method. Tests were conducted in the laboratory at the ambient temperature to examine the reduction in permeability to water or brine in the well-prepared sand packed after the polymer injection. The experiments were performed to study the effect of polymer adsorption on permeability reduction by analyzing residual resistance factor values with different concentrations of polymer solutions. The rheological behavior of the polymer has also been examined. The experimental results also indicate that the adsorption behavior of polymer is strongly affected by salinity, solution pH, and polymer concentration. To investigate the effect of polymer adsorption and mobility control on additional oil recovery, polymer flooding experiments were conducted with different polymer concentrations. It has been obtained that with the increase in polymer concentrations, oil recovery increases. Saurabh Mishra, Achinta Bera, and Ajay Mandal Copyright © 2014 Saurabh Mishra et al. All rights reserved. Study and Application of Polymer Film-Forming Shielding Plugging Drilling Fluid System Thu, 13 Feb 2014 00:00:00 +0000 To solve the low cementing quality of acoustic logging and some distensible well diameters in high permeable layer of Daqing Lamadian oilfield, we have carried out the study and field application of polymer film-forming shielding plugging drilling fluid system. By adding this polymer film-forming shielding plugging agent to macromolecule emulsion drilling fluid, the shielding and plugging effect will be improved. Combined with the experiment and analysis, we optimize the adding amount of this agent to improve the performance of drilling fluid system. From the application effect, the cementing quality of acoustic logging has been improved obviously. This system has been applied in 20 wells and there are 15 high quality wells. The merit factor of well cementing reaches 75%. Yuxue Sun, Fei Teng, and Jingyuan Zhao Copyright © 2014 Yuxue Sun et al. All rights reserved. Rethinking Petroleum Products Certification Tue, 10 Dec 2013 09:15:58 +0000 Facing various challenges in the everchanging refining landscape, it is essential that refiners raise their operations to new levels of performance. Advances in in-line blending (ILB) technology accuracy and reliability have encouraged refiners to take a step forward. Having ILB as a precursor, a new methodology is in concern: the so-called in-line certification (ILC) procedure. Blending processes make use of in-line measurements which, at least in principle, can be used to certificate the product, if the precision and accuracy of available in-line measurements are comparable to measurements provided by standard off-line tests. Such procedure may allow for significant reduction in refinery’s tank farming and product inventory, increase of process flexibility, and reliability with benefits to company image. The main limitations for real-world ILC applications in the oil industry remain at the legal and technological levels. This paper proposes novel concepts and foundations of a basic in-line certification model for petroleum products regarding current interdisciplinary challenges and promising solutions. Thiago Feital, Públio Lima, José Carlos Pinto, Maurício B. de Souza Jr., Gilberto Xavier, Mario Jorge Lima, and Marcel Joly Copyright © 2013 Thiago Feital et al. All rights reserved. Optimization of Multiple Hydraulically Fractured Horizontal Wells in Unconventional Gas Reservoirs Thu, 12 Sep 2013 18:00:01 +0000 Accurate placement of multiple horizontal wells drilled from the same well pad plays a critical role in the successful economical production from unconventional gas reservoirs. However, there are high cost and uncertainty due to many inestimable and uncertain parameters such as reservoir permeability, porosity, fracture spacing, fracture half-length, fracture conductivity, gas desorption, and well spacing. In this paper, we employ response surface methodology to optimize multiple horizontal well placement to maximize Net Present Value (NPV) with numerically modeling multistage hydraulic fractures in combination with economic analysis. This paper demonstrates the accuracy of numerical modeling of multistage hydraulic fractures for actual Barnett Shale production data by considering the gas desorption effect. Six uncertain parameters, such as permeability, porosity, fracture spacing, fracture half-length, fracture conductivity, and distance between two neighboring wells with a reasonable range based on Barnett Shale information, are used to fit a response surface of NPV as the objective function and to finally identify the optimum design under conditions of different gas prices based on NPV maximization. This integrated approach can contribute to obtaining the optimal drainage area around the wells by optimizing well placement and hydraulic fracturing treatment design and provide insight into hydraulic fracture interference between single well and neighboring wells. Wei Yu and Kamy Sepehrnoori Copyright © 2013 Wei Yu and Kamy Sepehrnoori. All rights reserved. Thermolysis of High-Density Polyethylene to Petroleum Products Thu, 30 May 2013 14:14:17 +0000 Thermal degradation of plastic polymers is becoming an increasingly important method for the conversion of plastic materials into valuable chemicals and oil products. In this work, virgin high-density polyethylene (HDPE) was chosen as a material for pyrolysis. A simple pyrolysis reactor system has been used to pyrolyse virgin HDPE with an objective to optimize the liquid product yield at a temperature range of 400°C to 550°C. The chemical analysis of the HDPE pyrolytic oil showed the presence of functional groups such as alkanes, alkenes, alcohols, ethers, carboxylic acids, esters, and phenyl ring substitution bands. The composition of the pyrolytic oil was analyzed using GC-MS, and it was found that the main constituents were n-Octadecane, n-Heptadecane, 1-Pentadecene, Octadecane, Pentadecane, and 1-Nonadecene. The physical properties of the obtained pyrolytic oil were close to those of mixture of petroleum products. Sachin Kumar and R. K. Singh Copyright © 2013 Sachin Kumar and R. K. Singh. All rights reserved. Simulation of Formation Damage after Long-Term Water Flooding Wed, 22 May 2013 16:32:09 +0000 Water flooding is a commonly used technology for enhancing oil recovery. Its main mechanism is to maintain higher pressure to sweep oil towards production wells. However, the strong water flooding will cause higher compression pressure around the injection wellbore. This high pressure in the reservoir causes stress redistribution and higher stress near the wellbore which induces material damage and permeability change. We developed a fluid-solid coupling finite element model to simulate and quantitatively analyze the pressure evolution in the reservoir as well as damage and permeability change in the formation during long-term water flooding process. The obtained results offer theoretical understanding of the benefits (pore pressure increase in the simulation domain), rock damage, permeability change of long-term water flooding, and the insights of how to detect and prevent wellbore failure and collapse due to water flooding. Liu He, Gao Yang, Li Guoxin, and Li Yiliang Copyright © 2013 Liu He et al. All rights reserved. Effect of Bed Deformation on Natural Gas Production from Hydrates Sun, 12 May 2013 10:55:55 +0000 This work is based on modelling studies in an axisymmetric framework. The thermal stimulation of hydrated sediment is taken to occur by a centrally placed heat source. The model includes the hydrate dissociation and its effect on sediment bed deformation and resulting effect on gas production. A finite element package was customized to simulate the gas production from natural gas hydrate by considering the deformation of submarine bed. Three sediment models have been used to simulate gas production. The effect of sediment deformation on gas production by thermal stimulation is studied. Gas production rate is found to increase with an increase in the source temperature. Porosity of the sediment and saturation of the hydrate both have been found to significantly influence the rate of gas production. Mohamed Iqbal Pallipurath Copyright © 2013 Mohamed Iqbal Pallipurath. All rights reserved. Improving the Demulsification Process of Heavy Crude Oil Emulsion through Blending with Diluent Sun, 21 Apr 2013 15:40:05 +0000 In crude oil production from brown fields or heavy oil, there is production of water in oil emulsions which can either be controlled or avoided. This emulsion resulted in an increase in viscosity which can seriously affect the production of oil from sand phase up to flow line. Failure to separate the oil and water mixture efficiently and effectively could result in problems such as overloading of surface separation equipments, increased cost of pumping wet crude, and corrosion problems. Light hydrocarbon diluent was added in varied proportions to three emulsion samples collected from three different oil fields in Niger delta, Nigeria, to enhance the demulsification of crude oil emulsion. The viscosity, total petroleum hydrocarbon, and quality of water were evaluated. The viscosity of the three emulsions considered reduced by 38, 31, and 18%. It is deduced that the increase in diluent blended with emulsion leads to a corresponding decrease in the value of viscosity. This in turn enhanced the rate of demulsification of the samples. The basic sediment and water (BS&W) of the top dry oil reduces the trace value the three samples evaluated, and with optimum value of diluent, TPH values show that the water droplets are safe for disposal and for other field uses. K. K. Salam, A. O. Alade, A. O. Arinkoola, and A. Opawale Copyright © 2013 K. K. Salam et al. All rights reserved. Well Screen and Optimal Time of Refracturing: A Barnett Shale Well Thu, 18 Apr 2013 15:23:10 +0000 Gas-production decline in hydraulically fractured wells in shale formations necessitates refracturing. However, the vast number of wells in a field makes selection of the right well challenging. Additionally, the success of a refracturing job depends on the time to refracture a shale-gas well during its production life. In this paper we present a numerical simulation approach to development of a methodology for screening a well and to determine the optimal time of refracturing. We implemented our methodology for a well in the Barnett Shale, where we had access to data. The success of a refracturing job depends on reservoir characteristics and the initial induced fracture network. Systematic sensitivity analyses were performed so that the characteristics of a shale-gas horizontal well could be specified as to the possibility of its candidacy for a successful refracturing job. Different refracturing scenarios must be studied in detail so that the optimal design might be determined. Given the studied trends and implications for a production indicator, the optimal time for refracturing can then be suggested for the studied well. Numerical-simulation results indicate significant improvement (on the order of 30%) in estimated ultimate recovery (EUR) after refracturing, given presented screen criteria and optimal-time selection. Shayan Tavassoli, Wei Yu, Farzam Javadpour, and Kamy Sepehrnoori Copyright © 2013 Shayan Tavassoli et al. All rights reserved. Electromagnetic Heating of Heavy Oil and Bitumen: A Review of Experimental Studies and Field Applications Tue, 16 Apr 2013 16:58:28 +0000 Viscosity is a major obstacle in the recovery of low API gravity oil resources from heavy oil and bitumen reservoirs. While thermal recovery is usually considered the most effective method for lowering viscosity, for some reservoirs introducing heat with commonly implemented thermal methods is not recommended. For these types of reservoirs, electromagnetic heating is the recommended solution. Electromagnetic heating targets part of the reservoir instead of heating the bulk of the reservoir, which means that the targeted area can be heated up more effectively and with lower heat losses than with other thermal methods. Electromagnetic heating is still relatively new and is not widely used as an alternate or addition to traditional thermal recovery methods. However, studies are being conducted and new technologies proposed that could help increase its use. Therefore, the objective of this study is to investigate the recovery of heavy oil and bitumen reservoirs by electromagnetic heating through the review of existing laboratory studies and field trials. Albina Mukhametshina and Elena Martynova Copyright © 2013 Albina Mukhametshina and Elena Martynova. All rights reserved. Dispersing of Petroleum Asphaltenes by Acidic Ionic Liquid and Determination by UV-Visible Spectroscopy Tue, 26 Mar 2013 15:13:26 +0000 Nowadays, constructing a mechanism to prevent the aggregation petroleum asphaltenes by the use of new acidic ionic liquids has become of fundamental importance. In this research, 3-(2-carboxybenzoyl)-1-methyl-1H-imidazol-3-ium chloride ([CbMIM] [Cl]) and other ionic liquids such as [CbMIM]BF4, [HMIM]Cl, [BMIM]Br, and [HMIM]HSO4 were tested. It should be noted that during the experiment the presence of the acidic ionic liquid moiety enhanced interactions between asphaltenes and acidic ionic liquids and it greatly limited asphaltene aggregation. We considered parameters such as temperature, amount of dispersant, effect of water: toluene ratio, the stirring time and effects of other ionic liquids, and determination of concentration of petroleum asphaltenes after dispersing by acidic ionic liquid under various parameters using UV-Visible spectroscopy. Eshagh Rezaee Nezhad, Fariba Heidarizadeh, Sami Sajjadifar, and Zahra Abbasi Copyright © 2013 Eshagh Rezaee Nezhad et al. All rights reserved. Review of Sand Production Prediction Models Wed, 09 Jan 2013 10:32:49 +0000 Sand production in oil and gas wells can occur if fluid flow exceeds a certain threshold governed by factors such as consistency of the reservoir rock, stress state and the type of completion used around the well. The amount of solids can be less than a few grams per cubic meter of reservoir fluid, posing only minor problems, or a substantial amount over a short period of time, resulting in erosion and in some cases filling and blocking of the wellbore. This paper provides a review of selected approaches and models that have been developed for sanding prediction. Most of these models are based on the continuum assumption, while a few have recently been developed based on discrete element model. Some models are only capable of assessing the conditions that lead to the onset of sanding, while others are capable of making volumetric predictions. Some models use analytical formulae, particularly those for estimating the onset of sanding while others use numerical models, particularly in calculating sanding rate. Although major improvements have been achieved in the past decade, sanding tools are still unable to predict the sand mass and the rate of sanding for all field problems in a reliable form. Hossein Rahmati, Mahshid Jafarpour, Saman Azadbakht, Alireza Nouri, Hans Vaziri, Dave Chan, and Yuxing Xiao Copyright © 2013 Hossein Rahmati et al. All rights reserved. A Field Study on Simulation of CO2 Injection and ECBM Production and Prediction of CO2 Storage Capacity in Unmineable Coal Seam Thu, 27 Dec 2012 17:04:39 +0000 CO2 sequestration into a coal seam project was studied and a numerical model was developed in this paper to simulate the primary and secondary coal bed methane production (CBM/ECBM) and carbon dioxide (CO2) injection. The key geological and reservoir parameters, which are germane to driving enhanced coal bed methane (ECBM) and CO2 sequestration processes, including cleat permeability, cleat porosity, CH4 adsorption time, CO2 adsorption time, CH4 Langmuir isotherm, CO2 Langmuir isotherm, and Palmer and Mansoori parameters, have been analyzed within a reasonable range. The model simulation results showed good matches for both CBM/ECBM production and CO2 injection compared with the field data. The history-matched model was used to estimate the total CO2 sequestration capacity in the field. The model forecast showed that the total CO2 injection capacity in the coal seam could be 22,817 tons, which is in agreement with the initial estimations based on the Langmuir isotherm experiment. Total CO2 injected in the first three years was 2,600 tons, which according to the model has increased methane recovery (due to ECBM) by 6,700 scf/d. Qin He, Shahab D. Mohaghegh, and Vida Gholami Copyright © 2013 Qin He et al. All rights reserved. Corrosion Inhibition of Tubing Steel during Acidization of Oil and Gas Wells Thu, 20 Dec 2012 10:53:58 +0000 Acidization is an oil reservoir stimulation technique for increasing oil well productivity. Hydrochloric acid is used in oil and gas production to stimulate the formation. The acid treatment occurs through N80 steel tubes. The process requires a high degree of corrosion inhibition of tubing material (N80 steel). In the present investigation effect of synthesized amino acid compounds, namely, acetamidoleucine (AAL) and benzamidoleucine (BAL) as corrosion inhibitors for N80 steel in 15% HCl solution was studied by polarization, AC impedance (EIS), and weight loss measurements. It was found that both the inhibitors were effective inhibitors and their inhibition efficiency was significantly increased with increasing concentration of inhibitors. Polarization curves revealed that the studied inhibitors represent mixed type inhibitors. AC impedance studies revealed that charge transfer resistance increases and double layer capacitance decreases in presence of inhibitors. Adsorption of inhibitors at the surface of N80 steel was found to obey Langmuir isotherm. M. Yadav, Sumit Kumar, and P. N. Yadav Copyright © 2013 M. Yadav et al. All rights reserved. Knowledge Discovery for Classification of Three-Phase Vertical Flow Patterns of Heavy Oil from Pressure Drop and Flow Rate Data Wed, 19 Dec 2012 08:42:00 +0000 This paper focuses on the use of artificial intelligence (AI) techniques to identify flow patterns acquired and recorded from experimental data of vertical upward three-phase pipe flow of heavy oil, air, and water at several different combinations, in which water is injected to work as the continuous phase (water-assisted flow). We investigate the use of data mining algorithms with rule and tree methods for classifying real data generated by a laboratory scale apparatus. The data presented in this paper represent different heavy oil flow conditions in a real production pipe. Adriane B. S. Serapião and Antonio C. Bannwart Copyright © 2013 Adriane B. S. Serapião and Antonio C. Bannwart. All rights reserved. Production of Biodiesel (B100) from Jatropha Oil Using Sodium Hydroxide as Catalyst Tue, 18 Dec 2012 10:08:39 +0000 This research work is about the production of biodiesel from jatropha oil. Other oils can also be used for the production, but jatropha was chosen because it is not edible therefore, it will not pose a problem to humans in terms of food competition. Before the transesterification process was carried out, some basic tests such as free fatty acid content, iodine value, and moisture content were carried out. This was done so as to ascertain quality yield of the biodiesel after the reaction. The production of the biodiesel was done with standard materials and under standard conditions which made the production a hitch-free one. The jatropha oil was heated to 60°C, and a solution of sodium methoxide (at 60°C) was added to the oil and stirred for 45 minutes using a magnetic stirrer. The mixture was then left to settle for 24 hours. Glycerin, which is the byproduct, was filtered off. The biodiesel was then thoroughly washed to ensure that it was free from excess methanol and soap. The characterization was done at NNPC Kaduna refinery and petrochemicals. The result shows that the product meets the set standard for biodiesel. Joshua Folaranmi Copyright © 2013 Joshua Folaranmi. All rights reserved.