Air Emissions From Fossil Fuel Combustion

J. Energy Resour. Technol. 2012;135(1):011101-011101-10. doi:10.1115/1.4007913.

In the present paper, we analyze numerically the disproportionate permeability reduction (DPR) water-shutoff (WSO) treatments in oil production well, i.e., the ability to reduce relative permeability (RP) to water more than to oil. The technique consists of bullhead injection of polymer solutions (gelant) into the near-wellbore formation without zone isolation. By assuming the low dissolution of polymer in oil and the low mobility of the gel in porous medium, we reduced the compositional model of the process to a simple two-phase model, with RP and capillary pressure (PC) dependent on the water and gel saturation. We proposed the extension of the LET correlations used to calculate RP and PC for the case of three phases (oil–water–gel). The problem is divided into two stages: the polymer injection and the post-treatment production. Both of these processes are described by the same formal mathematical model, which results from incompressible two-phase flow equations formulated in terms of normalized saturation and global pressure. The thermal effects caused by the injection of a relatively cold aqueous solution are taken into account. The numerical solution shows favorable results for the DPR WSO treatments. Other techniques, such as the creation of impermeable barrier and downhole water sink (DWS) technology, are also tested in order to check the validity of the developed numerical model with experimental data.

Commentary by Dr. Valentin Fuster

Alternative Energy Sources

J. Energy Resour. Technol. 2012;135(1):011201-011201-7. doi:10.1115/1.4007689.

A photobioreactor (PBR) for microalgae culture is a highly efficient system for biomass production. In the present study, the performance of an airlift (ALR) (with a centric-tube column) and a bubble column (BC) photobioreactors were compared considering Nannochloropsis sp. growth. The experiments were carried out keeping average light intensity, temperature, volume culture, and CO2 supply constant, while cell concentration and pH level were measured and examined. Furthermore, a computational fluid dynamics (CFD) simulation in cfx, ansys 11.0, was developed using a multiphase flow model with an Eulerian approach to evaluate the hydrodynamic behavior of both systems. The results showed that a higher cell concentration (375 × 105 cell/ml) was obtained in the airlift PBR yielding a better growth rate than the bubble column PBR. In terms of hydrodynamic performance, the existence of the centric-tube in the airlift system shows a well-defined flow pattern, better light distribution cycle, and more effective mixing. These hydrodynamic characteristic of the airlift PBR may allow a better yield for the microalgae biomass production.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;135(1):011202-011202-6. doi:10.1115/1.4007692.

The acorn (Quercus frainetto L.) kernel oil is extracted from the kernels of the acorn that is grown in Sakarya which is in the Marmara region, Turkey. Acorn kernel oil (AKO) is obtained in 10 wt. %, by solvent extraction. Acorn kernel oil is investigated as an alternative feedstock for the production of a biodiesel fuel. The fatty acid profile of the oil consists primarily of oleic, linoleic, palmitic, and stearic acids. Before processing alkalin transesterification reaction, the high free fatty acid (FFA) of the crude acorn kernel oil is decreased by using acid esterification method. Biodiesel is prepared from acorn kernel (AK) by transesterification of the acid esterified oil with methanol in the presence of potassium hydroxide (KOH) as catalyst. The maximum oil to ester conversion was 90%. The viscosity of biodiesel is closer to that of diesel and the heating value is about 6.4% less than that of petroleum diesel No. 2. All of the measured properties of the produced acorn kernel oil methyl ester (AKOME) are being compared to the current quality requirements according to EN14214 and ASTM D 6751. The comparison shows that the methyl esters of acorn kernel oil could be possible used as diesel fuel replacements.

Commentary by Dr. Valentin Fuster

Energy Conversion/Systems

J. Energy Resour. Technol. 2012;135(1):011601-011601-7. doi:10.1115/1.4007717.

The chemical potential (free energy) of mixing two aqueous solutions can be extracted via an auto generative capacitive mixing (AGCM) cell using anionic and cationic exchange membranes together with porous carbon electrodes. Alternately, feeding sea and river water through the unit allows for the system to spontaneously deliver charge and discharge the capacitive electrodes so that dc electric work is supplied. Having a stack of eight cells coupled in parallel demonstrated the viability of this technology. An average power density of 0.055 W m−2 was obtained during the peak of the different cycles, though reasonable optimization suggests an expectation of 0.26 W m−2 at 6.2 A m−2. It was found that 83 ± 8% of the theoretical driving potential was obtained during the operating process. By studying the polarization curves during charging and discharging cycles, it was found that optimizing the feed fluid flow is currently among the most beneficial paths to make AGCM a viable salinity difference power source. Another parallel route for increasing the efficiency is lowering the internal ohmic resistances of the cell by design modifications.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;135(1):011602-011602-8. doi:10.1115/1.4007912.

Mass conservation equation is employed to study the time evolution of the mass of oil in a reservoir, according to the actual mass flow rate of extraction. It is also possible to define the critical mass flow rate of extraction, which is the value exhausting the reservoir in an infinite time. The evolution with time of the price of the resources extracted and sold to the market is investigated in case of no-accumulation and no-depletion of the resources, i.e., when the resources are extracted and sold to the market at the same mass flow rate. The total energy conservation equation is transformed into a money or capital per time conservation equation, which allows to study the price evolution with time, which is dependent on the following parameters. The price evolution with time of the extracted resource is dependent on the parameter PIFE, “Price-Increase Factor of Extracted resource,” which is the difference between the basic interest rate of the capital, e.g., the inflation rate, and the mass flow rate of extraction. The price evolution with time of the sold resource is dependent on the parameter PIFS, “Price-Increase Factor of Sold resource,” which is the difference between the interest rate of the capital, e.g., discount or prime rate, and the mass flow rate of extraction. The parameter CIPS, “Critical Initial Price of Sold resource,” depends on the initial price of the extracted resource, on the interest rate of nonextracted resource, and on the difference between PIFS and PIFE. The parameter CIPES, “Critical Initial Price Extreme of Sold resource,” depends on the initial price of the extracted resource, on the interest rate of nonextracted resource, and PIFS. The time evolution of the oil price during the 8 months of 2009, when the inflation rate was negative, and following the economic crisis of 2008, is investigated introducing a new category of cases, i.e., the negative inflation rate one. The paper presents and discusses the results of the forecasting for different values of the interest rate of the capital, i.e., prime and discount rate, with the conclusion that the present theory can forecast the evolution of the oil price with a reasonable confidence using the prime and the discount rates as extreme limits.

Commentary by Dr. Valentin Fuster

Energy Extraction From Natural Resources

J. Energy Resour. Technol. 2012;135(1):011701-011701-8. doi:10.1115/1.4007661.

The recycling of plastic waste is important both in the conservation of resources and the environment. A plastic waste (polyethylene(PE)/polypropylene(PP)/polystyrene(PS)/polyvinyl chloride(PVC)) was pyrolyzed over a series of post-use fluid catalytic cracking (FCC) catalysts using a fluidizing reaction system similar to the FCC process operating isothermally at ambient pressure. Experiments carried out with these catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. A model based on kinetic considerations associated with chemical reactions and catalyst deactivation in the catalytic degradation of plastics has been developed. Greater product selectivity was observed with a hybrid catalyst (SAHA/CAT-R1) of amorphous silica-aluminas (SAHA) and a recycle FCC catalyst with regeneration (CAT-R1) with more than 68.6 wt. % olefins products. It is demonstrated that the catalytic degradation of postconsumer plastics over these recycled catalysts using fluidizing cracking reactions was shown to be a useful method for the production of potentially valuable hydrocarbons.

Commentary by Dr. Valentin Fuster

Energy Systems Analysis

J. Energy Resour. Technol. 2012;135(1):012001-012001-5. doi:10.1115/1.4007657.

Plants and photosynthetic bacteria hold protein molecular complexes that can efficiently harvest photons. This article presents fundamental studies to harness photochemical activities of photosynthetically active protoplast extracted from Arabidopsis plants. The conversion of photonic energy into electrical energy was characterized in the presence and absence of light. The photoinduced reactions of photosynthesis were measured using a patch clamp measurement system at a constant voltage. The optical characterization was also performed on the extracted protoplast. It showed absorption bands at a number of wavelengths. The current–voltage measurements done on protoplast extracts showed two orders of magnitude increase in current from dark to light conditions. The absorbance measurements showed very large bandwidth for extracted protoplasts. The analysis of the optical data measurements showed that protein complexes obtained from photosynthetic cells overcame the limitation of traditional organic solar cells that cannot absorb light in the visible-near infrared spectrum. The demonstration of electrical power scavenging from the protoplast of the plant can open avenues for bio–inspired and bio-derived power with better quantum electrical efficiency.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;135(1):012002-012002-5. doi:10.1115/1.4007940.

The output characteristics of multiple photovoltaic (PV) arrays at partial shading are characterized by multiple steps and peaks. This makes that the maximum power point tracking (MPPT) of a large scale PV system becomes a difficult task. The conventional MPPT control method was unable to track the maximum power point (MPP) under random partial shading conditions, making the output efficiency of the PV system is low. To overcome this difficulty, in this paper, an improved MPPT control method with better performance based on the genetic algorithm (GA) and adaptive particle swarm optimization (APSO) algorithm is proposed to solve the random partial shading problem. The proposed genetic algorithm adaptive particle swarm optimization (GAAPSO) method conveniently can be used in the real-time MPPT control strategy for large scale PV system, and the implementation of the collect circuit is easy to gain the global peak of multiple PV arrays, thereby resulting in lower cost, higher overall efficiency. The proposed GAAPSO method has been experimentally validated by using several illustrative examples. Simulations and experimental results demonstrate that the GAAPSO method provides effective, fast, and perfect tracking.

Commentary by Dr. Valentin Fuster

Petroleum Wells-Drilling/Production/Construction

J. Energy Resour. Technol. 2012;135(1):013101-013101-11. doi:10.1115/1.4007691.

Riserless drilling poses numerous operational challenges that adversely affect the efficiency of the drilling process. These challenges include increased torque and drag, buckling, increased vibration, poor hole cleaning, tubular failures, poor cement jobs, and associated problems during tripping operations. These challenges are closely associated with complex bottomhole assemblies (BHAs) and the vibration of the drillstring when the topholes are drilled directionally. Current methods lack proper modeling to predict drillstring vibration. This paper presents and validates a modified model to predict severe damaging vibrations, analysis techniques, and guidelines to avoid the vibration damage to BHAs and their associated downhole tools in the riserless highly deviated wells. The dynamic analysis model is based on forced frequency response (FFR) to solve for resonant frequencies. In addition, a mathematical formulation includes viscous, axial, torsional, and structural damping mechanisms. With careful consideration of input parameters and judicious analysis of the results, the author demonstrates that drillstring vibration can be avoided by determining the 3D vibrational response at selected excitations that are likely to cause them. The analysis also provides an estimate of relative bending stresses, shear forces, and lateral displacements for the assembly used. Based on the study, severe vibrations causing potentially damaging operating conditions were avoided, which posed a major problem in the nearby wells. The study indicates that the results are influenced by various parameters, including depth of the mud line, offset of the wellhead from the rig center, wellbore inclination, curvature, wellbore torsion, and angle of entry into the wellhead. This study compares simulated predictions with actual well data and describes the applicability of the model. Simple guidelines are provided to estimate the operating range of the drilling parameter to mitigate and avoid downhole tool failures.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;135(1):013102-013102-9. doi:10.1115/1.4007767.

Managing oil production from reservoirs to maximize the future economic return of the asset is an important issue in petroleum engineering. In many applications in reservoir modeling and management, there is a need for rapid estimation of large-scale reservoirs. The capacitance-resistive model (CRM), regarded as a promising rapid evaluator of reservoir performance, has recently been used for simulation of single-layer reservoirs. Injection and production rates are considered as input and output signals in this model. Connections between the wells and the effects of injection rates on production rates are calculated based on these signals to develop a simple model for the reservoir. In this study, CRM is improved to model a multilayer reservoir and is applied to estimate and optimize waterflooding performance in an Iranian layered reservoir. In this regard, CRM is coupled with production logging tools (PLT) data to study the effects of layers. A fractional-flow model is also coupled with the developed CRM to estimate oil production. Genetic algorithm (GA) method is used to minimize the error objective function for the total production history and oil production history to evaluate model parameters. GA is then used to maximize oil production by reallocating the injected water volumes, which is the main purpose of this research. The results show that our fast method is able to model liquid and oil production history and is in good agreement with available field data. Taking into account the reservoir constraints, the optimal injection schemes have been obtained. For the proposed injection profile, the field hydrocarbon production will increase by up to 1.8% until 2016. Also, the wells will reach the water-cut constraint 2 yr later than the current situation, which increases the production period of the field.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;135(1):013103-013103-7. doi:10.1115/1.4007915.

Drillstring vibration is one of the limiting factors maximizing drilling performance. Torsional vibrations/oscillations while drilling is one of the sever types of drillstring vibration which deteriorates the overall drilling performance, causing damaged bit, failure of bottom-hole assembly, overtorqued tool joints, torsional fatigue of drillstring, etc. It has been identified that the wellbore-drillstring interaction and well face-drill bit interaction are the sources of excitation of torsional oscillations. Predrilling analysis and real time analysis of drillstring dynamics is becoming a necessity for drilling oil/gas or geothermal wells in order to optimize surface drilling parameters and to reduce vibration related problems. It is very challenging to derive the drillstring model considering all modes of vibrations together due to the complexity of the phenomenon. This paper presents the mathematical model of a torsional drillstring based on nonlinear differential equations which are formulated considering drillpipes and bottom-hole assembly separately. The bit–rock interaction is represented by a nonlinear friction forces. Parametric study has been carried out analyzing the influence of drilling parameters such as surface rotations per minute (RPM) and weight-on-bit (WOB) on torsional oscillations. Influences of properties of drillstring like stiffness and inertia, which are most of the times either unknown or insufficiently studied during modeling, on torsional oscillation/stick-slip is also studied. The influences of different rock strength on rate of penetration (ROP) considering the drilling parameters have also been studied. The results show the same trend as observed in fields.

Commentary by Dr. Valentin Fuster

Underground Injection and Storage

J. Energy Resour. Technol. 2012;135(1):013301-013301-7. doi:10.1115/1.4007799.

Reactions of CO2 with formation rock may lead to an enhancement in the permeability due to rock dissolution, or damage (reduction in the core permeability) because of the precipitation of reaction products. The reaction is affected by aquifer conditions (pressure, temperature, initial porosity, and permeability), and the injection scheme (injection flow rate, CO2:brine volumetric ratio, and the injection time). The effects of temperature, injection flow rate, and injection scheme on the permeability alteration due to CO2 injection into heterogeneous dolomite rock is addressed experimentally in this paper. Twenty coreflood tests were conducted using Silurian dolomite cores. Thirty pore volumes of CO2 and brine were injected in water alternating gas (WAG) scheme under supercritical conditions at temperatures ranging from 21 to 121 °C, and injection rates of 2.0–5.0 cm3/min. Concentrations of Ca++, Mg++, and Na+ were measured in the core effluent samples. Permeability alteration was evaluated by measuring the permeability of the cores before and after the experiment. Two sources of damage in permeability were noted in this study: (1) due to precipitation of calcium carbonate, and (2) due to migration of clay minerals present in the core. Temperature and injection scheme don't have a clear impact on the core permeability. A good correlation between the initial and final core permeability was noted, and the ratio of final permeability to the initial permeability is lower for low permeability cores.

Commentary by Dr. Valentin Fuster


J. Energy Resour. Technol. 2012;135(1):013401-013401-8. doi:10.1115/1.4007662.

Many operators of tight gas reservoir fields are interested in determining the infill well potential in these fields. Over drilling may prove to be uneconomical; whereas, under drilling would leave unexplored reserves under the ground. In predicting EUR (expected ultimate recovery) of a potential infill well, operators are interested in knowing what percentage of the production will be come from incremental reserves (newly accessed) and what percentage is from acceleration reserves (which can be produced from existing wells). So, higher the percentage of incremental reserves better is the potential of an infill well. In this paper, we present a novel method for determining the incremental versus acceleration potential for infill well in a tight gas reservoir. We evaluate the existing wells by plotting the data in a form so that the data can be linearly extrapolated. Then, we can predict the EUR for individual wells before and after new wells in the vicinity are drilled. By knowing how much gas is “diverted” from the older wells, we determine the acceleration component of an infill well. By repeating the process as the field is being developed, we can determine the fraction of acceleration and incremental components of the EUR at each stage of infill drilling. We will also know how the EUR is changing as the well spacing is slowly reduced. To ensure our results are reasonable, we also compare our EUR values with EUR’s reported by the operator as proved reserves. Armed with this information, we can extrapolate infill well potential for a smaller spacing, including the contribution due to acceleration versus incremental production. We applied this procedure for Wamsutter field in Wyoming. Using the procedure, we recommended infill well locations to the operator. Operator has drilled seven wells based on our recommendations. Using this new method, we can predict the EUR for infill well as well as acceleration and incremental contribution of the infill well. Thus, potential of infill wells at different locations can be evaluated and compared.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2012;135(1):013402-013402-10. doi:10.1115/1.4007766.

Development of shale gas reservoirs has become an integral part of the North American gas supply. The Marcellus shale reservoir contains large untapped natural gas resources and its proximity to high demand markets along the East Coast of the United State makes it an attractive target for energy development. The economic viability of such unconventional gas development hinges on the effective stimulation of extremely low permeability reservoir rocks. Horizontal wells with multistage hydraulic fracturing technique are the stimulation method of choice and have been successful in shale gas reservoirs. However, the fundamental science and engineering of the process are yet to be fully understood and hence the protocol that needs to be followed in the stimulation process needs to be optimized. There are several factors affecting the hydraulic fracture treatment and the postfracture gas production in shale gas reservoirs. In this paper, we used numerical reservoir simulation techniques and quantified the effect of the following pertinent factors: multiphase flow, proppant crushing, proppant diagenesis, reservoir compaction, and operating conditions on the performance of the designed multistage hydraulic fracturing process. The knowledge generated in this study is expected to enable engineers to better design fracture treatments and operators to better manage the wells in the Marcellus shale gas reservoir.

Commentary by Dr. Valentin Fuster

Technology Reviews

J. Energy Resour. Technol. 2012;135(1):014001-014001-9. doi:10.1115/1.4007660.

Biomass gasification has gained significant attention in the last couple of decades for the production of heat, power, and second generation biofuels. Biomass gasification processes are highly complex due to the large number of reactions involved in the overall process as well as the high sensitivity of the process to changes in the operational conditions. This report reviews the state-of-the-art of biomass gasification by evaluating key process parameters such as gasifying agent, temperature, pressure, particle size, etc., for fluidized bed and entrained flow gasifiers. The pros and cons of each technology and the remaining bottlenecks are also addressed.

Commentary by Dr. Valentin Fuster

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