Andres R. ValdezBernardo Martins RochaGrigori Chapiro
12页
查看更多>>摘要：Foam injection in porous media is often used to control the gas fingering in multi-phase flow. Mathematical models of foam dynamics involve non-Newtonian formulations. To numerically simulate these complex phenomena, experimental data is gathered and used to estimate the parameter values of models via optimization techniques. The present work improves this procedure by introducing a new objective function based on the mobility reduction factor and does not require further experimental observations other than those usually obtained in core-flooding experiments. A series of numerical experiments were carried out to show the features and robustness of the proposed approach. In particular, the identifiability analysis results show that key parameters of the models are practically non-identifiable when using traditional objective functions that rely only on apparent viscosity. When the proposed objective function is used for parameter estimation, the identifiability issues are solved. In addition, the uncertainty quantification analysis revealed that lower uncertainty is achieved when using the new objective function when compared to the one that uses only apparent viscosity. In summary, we show that the new objective function generates better-calibrated models with high fidelity and low uncertainties and alleviates parameter non-identifiability issues. Therefore, the results suggest the new objective function is better suited for calibrating foam displacement models for enhanced oil recovery.
查看更多>>摘要：Production from heavy asphaltenic oil reservoirs poses several challenges that require new and innovative techniques for improved production and recovery. The main objective of this study is to experimentally investigate the influences of ultrasonic waves and solvent on oil viscosity, asphaltene precipitation behavior, and recovery of a heavy asphaltenic crude oil. This study is divided into two main parts. In the first part, crude oil samples were subjected to ultrasonic radiation with a frequency of 20 kHz and varying output powers (30, 60, and 100 W) for various durations. The viscosity of each oil sample was measured immediately after stopping ultrasonic radiation and also after 24 h of irradiation. An optimum time for ultrasound radiation was determined when the cooled-down radiated oil reached a minimum viscosity. We then measured the viscosity of the ultrasonically treated oil samples blended with a solvent (i.e., n-heptane) to assess the synergetic effect of ultrasonic radiation and solvation on the oil viscosity. In the second part, the application of ultrasonic radiation on the asphaltene aggregates and oil recovery was examined using solvent flooding in a transparent porous medium. Four sets of experiments were undertaken where the solvent was injected into the micromodel saturated with the untreated and ultrasonically treated oil free from or blended with the solvent. The results showed that ultrasonic treatment decreased the size of asphaltene aggregates and consequently reduced the viscosity of the crude oil. As a result, the suspension of asphaltene in the ultrasonically treated oil increased and reduced its tendency to precipitate at the optimum radiation time. Furthermore, the results indicated that the combined use of ultrasound and solvent had the greatest reduction in the oil viscosity compared to the untreated crude oil with ultrasonic waves or solvent.
查看更多>>摘要：High-voltage electro-pulse boring (EPB) rock-breaking can produce tensile damage, which has significant advantages in deep hard rock drilling. To develop a bit with high drilling efficiency and low energy consumption has become one technical problem in EPB technology. First, based on the electrode structure arrangement and the previous research on EPB mechanism, this paper developed three lands of electrode bits with a coaxial cylindrical structure, electrode cross structure and multi-electrode pair structure. Second, it established a numerical simulation model of EPB with different-structure bits, and analyzed the influence of different structural arrangements on EPB. Based on the idea of parametric design of electrode bit parts, the influence of the high-voltage electrode shape on EPB was further analyzed. Finally, it built the EPB test units, and carried out the EPB tests of the bits with different structures, and made clear the influence of different structural arrangements on EPB. Compared with EPB experimental results, the bit with a coaxial cylindrical structure had the best drilling effect, followed by the one with a multi-electrode pair structure, and then the one with an electrode cross structure with the same setting of electrical parameters. At the same time, this paper made the EPB experiments on different high-voltage electrode shapes by using a coaxial cyUndrical electrode bit. The results showed that the bit with a conical high-voltage electrode had the best drilling effect, followed by the one with a spherical high-voltage electrode, and then the one with a flat bottom high-voltage electrode. Through the simulation analysis and experimental study, this paper concluded the influence law of the bit structure on EPB. The application of the findings was helpful to guide the design of electrode bit structure, reduce energy consumption, and improve drilling efficiency.
查看更多>>摘要：Considerable lost circulation of oil-based drilling fluid often occurs because of pores and fractures that develop in formations, which can significantly increase drilling costs. In this study, we prepared a ternary composite self-swelling oil-absorbing resin and investigated the synthesis conditions on its oil-absorption properties. The resin molecular structure and properties were characterized by infrared spectroscopy, thermal stability, and scanning electron microscope, and we subsequently analyzed the fracture plugging mechanism of the resin. The results indicated that when the content ratio of butyl acrylate and stearyl methacrylate was 2:1, the sodium-p-styrenesulfonate content was 1%, the initiator content was 0.3%, and the cross-linker dosage was 0.16%, the resin exhibited good toughness and oil-swelling performance. The unsaturated groups in the copolymer were grafted, forming a three-dimensional network structure. At 120 °C, composite resin particles were used to seal fractures with width of 1-3 mm, with the pressure bearing capacity reaching 4.7 MPa. The fracture was compacted and sealed through deformation, compaction, and filling. Compared to conventional lost circulation materials, the oil-absorbing resin exhibited good thermal stability and self-adaptability, and could easily enter pores and micro-fractures, effectively reducing lost circulation of the oil-based drilling fluid.
查看更多>>摘要：In this work, the dynamic formation process of wax depositions for a series of water-in-oil emulsions was explored in situ using the PVM (particle video microscope) apparatus. Two types of wax deposition structures were observed: wax crystal clusters enclosing water droplets and water droplet floes with surfaces covered by wax crystals, either of which could build up a wax deposition. These two structures were formed by the collision, flocculation, aggregation, and encapsulation of two scattered phases: wax crystals and water droplets. The organization of the deposition gradually converted from wax crystal clusters to water droplet floes was depicted considering the surfactant concentration (0.05, 0.1, 0.5 wt%) and water content (10, 20, 30, 40 vol%) used in emulsion formulation. Furthermore, the variation of water content in the deposition even employing the emulsion with the same water cut was elucidated, which was closely related to these two deposition structures. This in situ study revealed that the surfactant in the wax deposition process of emulsion not only operated as an emulsifier but also tailored the type of deposition structure by inducing the dispersion of wax crystals from oil phase to oil-water interface. These structures partially or entirely involved water droplets into deposition. The findings provide a thorough description of wax deposition formation in water-in-oil emulsions.
查看更多>>摘要：One of the most important constituents of oil and gas reservoirs is clay minerals; they may cause formation damage by swelling and migration. When water with lower salinity than formation water invades clay-rich porous media, the clays absorb the water, which results in swelling and, therefore, limit the available space for fluids to flow. Clays may also detach from rock surfaces and start to migrate and block pore throats. Both mechanisms lead to permeability impairment as a critical formation damage element. A better understanding of damage due to clays helps us to control and overcome the problem, which affects oil recovery. In this work, the swelling and migration of clays are studied at the pore scale using clay coated micromodels. The effect of the composition and salinity of injected brines on sodium bentonite swelling and migration were visualized, investigated, and analyzed by a novel approach based on an image processing technique. The effect of simultaneous clay swelling and migration on porosity alteration at different sections of the micromodel was studied to estimate damage, qualitatively and quantitatively. Our experiments showed that the presence of KCl salt in the brine used in drilling, completion, and development operations is vital to control formation damage. The best damage remedy performance was reached when a salt with small hydrated radius cations, such as KCl is combined with a salt with divalent and small hydrated radius cations, such as CaCh- The combination of KCl and CaCh showed only 2.8% reduction of porosity, while KCl showed around 7% reduction of porosity. In migration control, KCl showed the best ability to control migration and most of the migrated clays were re-adsorbed in the porous media.
查看更多>>摘要：Multiphase flow metering in oil and gas production wells is essential for monitoring the production performance from oil and gas reservoirs. Accurate measurements of multiphase flow rate diat passes through the chock at the wellhead assembly is highly important as it provides a crucial information to estimate production to asses and optimize the reservoir performance. The current practice is to conduct production rate tests monthly for the entire wells that are connected through the same manifold. Another way to estimate the flow rate at the surface is using any of the several correlations to calculate the flow rate using production and wellhead chock data. The high uncertainty in production rate predictions is very well expected and the main source of this uncertainty is the reliance on sporadic well test data and empirical multiphase flow correlations. The objective of this study is to develop a machine learning model that outperforms the industry's widely used correlations in predicting the flow rate of critical and subcritical multiphase flow through the wellhead choke. This objective is achieved by developing a detailed workflow to generate a choke performance prediction model. Validating the accuracy and reliability of the developed model is done using actual data from more than 4000 production rate tests from different fields to investigate the model's accuracy. Testing the developed models showed that it provides a higher accuracy than the several correlations it was compared against in critical and subcritical flow. The average accuracy (correlation coefficient) of prediction was around 0.92 for critical and subcritical flow models. The developed models using machine learning provided a reliable method to predict flow rate through the wellhead chock by utilizing readily available surface data.
查看更多>>摘要：Formation damage can occur in any phase of oil and gas operation from drilling, completion, or stimulation. Fluids used to drill, complete, and fracture the formation may invade and damage the formation. These fluids may interact with clays present in the formation and adversely affect the flow performance. The change in flow performance could occur due to flow restriction or decrease in permeability, change in relative permeability, or unintended flow restriction during the specific operation. In this work, ionic liquids are proposed as clay swelling additives in completion fluid to overcome the formation damage problem. Imidazolium-based ionic liquids and three different salts are tested with 0.5 wt % and 3 wt % concentration, respectively, on tight sandstone formation containing high clay contents. Completion fluids prepared using ionic liquids resulted in complete stabilization of clays and therefore nearly maintain the in-situ permeability of tight sandstone. The completion fluids are prepared in deionized water for experimental consistency. Coreflooding experiments were performed on Scioto sandstone core samples containing an average porosity and permeability of 16.9% and 0.72 mD, respectively. Cores were saturated with completion fluids based on salts such as calcium chloride (CaCl2), magnesium chloride (MgCl2), and ammonium chloride (NH4Cl) and with Imidazolium-based ionic liquids before the coreflooding experiments. These coreflood experiments involve a preflush with the prepared completion fluid and post-flood with deionized water. Moreover, Nuclear Magnetic Resonance (NMR) tests were performed on all samples before and after coreflood to estimate the change in porosity and pore size distributions of the rock samples. Results showed that the porosity and permeability loss were significantly large in cores flooded with CaCl2 and NH4Cl salts solution when flooded with water. MgCl2 salt solution showed exceptionally stable porosity and permeability compared to other completion fluids. Furthermore, the results of ionic liquid-based completion fluids showed no significant loss in porosity and permeability when flooded with water. Therefore, the proposed ionic liquid-based completion fluids can be used for well-completion operation without any formation damage.
查看更多>>摘要：Whirl is a kind of serious lateral vibration. Accurate numerical simulation of whirl for drill string is important for drilling engineering. In this study, a new finite element (FE) model using shell element is established, which can accurately describe the whirl and realize the visualization of motion. Rolling model of drill string in the borehole is proposed. Kinematic contact with clearance, Coulomb friction model and initial imperfection are considered in this model. The explicit dynamic method is selected to solve the convergence difficulty caused by complex contact between shell elements. Compared with the experiment results, the accuracy and reliability of the model are verified. Meanwhile, the effects of rotation speed, friction coefficient, weight-on-bit (WOB) and clearance between the drill string and the borehole wall on the whirl of vertical wells are also studied in the numerical simulation. The rotation speed and friction coefficient have an obvious positive effect on the random motion and backward whirl of drill string: The continuous increase of rotation speed or friction coefficient can cause backward whirl, after that, velocity, acceleration of drill string, contact force and friction will increase significantly. When the rotating speed increases from 400 rpm to 800 rpm, the whirling speed increases by 160%, the average friction and contact force increase by 290%, which is much higher than the increase of 100% of the rotating speed. Instead, WOB has little influence on the drilling parameters mentioned-above and the variations of average friction and contact force for different WOB does not exceed 10%. In addition, properly increasing the distance between the drill string and the borehole wall will make backward whirl easily occur. However, when the clearance is large enough, there will be no contact and the drill string will make irregular non-contact forward whirl. What's more, forward whirl has a positive impact on eccentric wear, and backward whirl reduces WOB transmission and increases risk of sticking. Therefore, drill string whirl should be reasonably utilized or its harm should be reduced in practical drilling engineering.
Ahmed H. GowidaSidqi A. Abu-KhamsinMohammed A. Mahmoud
9页
查看更多>>摘要：Sand production that occurs in poorly consolidated oil and gas reservoirs causes many serious operational problems. Industry experts have used both chemical and mechanical sand control techniques to overcome this challenge; however, these techniques have various technical and economic limitations. For example, a technique that employed in-situ low-temperature oxidation (LTO) of an asphaltic solution saturating the near-wellbore area helped increase the formation's compressive strength while retaining its permeability; however, this technique was time-consuming at low reservoir temperatures. This study employed thermochemicals to preheat the sand and thereby accelerate the LTO reaction and shorten the consolidation process. First, small packs of loose sand saturated with an asphaltic solution were oxidized via external heating until consolidation. The optimal conditions involved continuous airflow for 6 h at 180 °C, which produced consolidated sand with a compressive strength exceeding 12.4 MPa. Second, a similar but insulated saturated sand pack was flooded with several pore volumes of thermochemicals, which raised its temperature from 75 °C to 188 °C; this was followed by 6 h of air injection. The consolidated sand had a compressive strength of 10.27 MPa and showed excellent stability against acid and crude oil floods as well as prolonged soaking in toluene. This study demonstrated the potential of using thermochemicals for the in situ heating of the wellbore area to elevated temperatures for sand consolidation. By shortening the treatment time, the thermochemicals improved the cost-effectiveness of sand consolidation via LTO without adversely affecting the consolidation quality.
NSTL