An evaluation on mechanisms of miscibility development in acid gas injection for volatile oil reservoirs

International audienceProduced gas containing the acid gas reinjection is one of the effective enhanced oil recovery methods, not only saving costs of disposing acid gases and zero discharge of greenhouse gases but also supporting reservoir pressure. The subsurface fluid from the Carboniferous carbonate reservoir in the southern margin of the Pre-Caspian basin in Central Asia has low density, low viscosity, high concentrations of H2S (15%) and CO2 (4%), high solution gas/oil ratio. The reservoir is lack of fresh water because of being far away onshore. Pilot test has already been implemented for the acid gas reinjection. Firstly, in our work a scheme of crude oil composition grouping with 15 compositions was presented on the basis of bottomhole sampling from DSTs of four wells. After matching PVT physical experiments including viscosity, density and gas/oil ratio and pressure–temperature (P–T) phase diagram by tuning critical properties of highly uncertain heavy components, the compositional model with phase behavior was built under meeting accuracy of phase fitting, which was used to evaluate mechanism of miscibility development in the acid gas injection process. Then using a cell-to-cell simulation method, vaporizing and/or condensing gas drive mechanisms were investigated for mixtures consisting of various proportions of CH4, CO2 and H2S in the gas injection process. Moreover, effects of gas compositions on miscible mechanisms have also been determined. With the aid of pressure-composition diagrams and pseudoternary diagrams generated from the Equation of State (EoS), pressures of First Contact Miscibility (FCM) and Multiple Contact Miscibility (MCM) for various gases mixing with the reservoir oil sample under reservoir temperature were calculated. Simulation results show that pressures of FCM are higher than those of MCM, and CO2 and H2S are able to reduce the miscible pressure. At the same time, H2S is stronger. As the CH4 content increases, both pressures of FCM and MCM are higher. But incremental values of MCM decrease. In addition, calculated envelopes of pseudoternary diagrams for mixtures of CH4, CO2 and H2S gases of varying composition with acid gas injection have features of bell shape, hourglass shape and triangle shape, which can be used to identify vaporizing and/or condensing gas drives. Finally, comparison of the real produced gas and the one deprived of its C3+ was performed to determine types of miscibility and calculate pressures of FCM and MCM. This study provides a theoretical guideline for selection of injection gas to improve miscibility and oil recovery

Laser ablation resistance and mechanism of Si-Zr alloyed melt infiltrated C/C-SiC composite

Ablation resistance of C/C-SiC composite prepared via Si-Zr alloyed reactive melt infiltration was evaluated using a facile and economical laser ablation method. Linear ablation rates of the composite increased with an increase in laser power densities and decreased with extended ablation time. The C/C-SiC composite prepared via Si-Zr alloyed melt infiltration presented much better ablation resistance compared with the C/SiC composite prepared by polymer infiltration and pyrolysis process. The good ablation resistance of the composite was attributed to the melted ZrC layer formed at the ablation center region. Microstructure and phase composition of different ablated region were investigated by SEM and EDS, and a laser ablation model was finally proposed based on the testing results and microstructure characterization. Laser ablation of the composite experienced three distinct periods. At the very beginning, the laser ablation was dominated by the oxidation process. Then for the second period, the laser ablation was dominated by the evaporation, decomposition and sublimation process. With the further ablation of the composite, chemical stable ZrC was formed on the ablated surface and the laser ablation was synergistically controlled by the scouring away of ZrC melts and evaporation, decomposition and sublimation process.This work is supported by National Natural Science Foundation of China (51641502)

Concurrent nephrotic syndrome and acute renal failure caused by chronic lymphocytic leukemia (CLL): a case report and literature review

Kidney injury associated with lymphocytic leukemia (CLL) is typically caused by direct tumor infiltration which occasionally results in acute renal failure. Glomerular involvement presenting as proteinuria or even nephrotic syndrome is exceptionally rare. Here we report a case of 54-year-old male CLL patient with nephrotic syndrome and renal failure. The lymph node biopsy confirmed that the patients had CLL with remarkable immunoglobulin light chain amyloid deposition. The renal biopsy demonstrated the concurrence of AL amyloidosis and neoplastic infiltration. Combined treatment of fludarabine, cyclophosphamide and rituximab resulted in remission of CLL, as well as the renal disfunction and nephrotic syndrome, without recurrence during a 12-month follow-up. To our knowledge, this is the first case of CLL patient showing the nephrotic syndrome and acute renal failure caused by AL amyloidosis and neoplastic infiltration. Though AL amyloidosis caused by plasma cell dyscrasia usually responses poorly to chemotherapy, this patient exhibited a satisfactory clinical outcome due to successful inhibition of the production of amylodogenic light chains by combined chemotherapy

Pore network modeling of thin water film and its influence on relative permeability curves in tight formations

Acknowledgments We acknowledge the Beijing Natural Science Foundation of China (No. 2204093), Science Foundation of China University of Petroleum, Beijing (No.2462018YJRC033) and financial support from China Scholarship Council ((No. 201906440134). Dr. Yingfang Zhou would like to acknowledge the support from State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Southwest Petroleum University), PLN201602.Peer reviewedPostprin

Analysis of fine grained sand and shale sedimentary characteristics in estuary based on sediment dynamics

Due to the dual effects of fluvial and tides, the tidal sand bars in estuaries have complex sedimentary characteristics and complex internal structures, making them difficult to predict and describe. In this paper, the sedimentary dynamics numerical simulation method is used to establish a tidal-controlled estuary model. The effects of tidal range and sediment grain size on tidal sand bars are simulated. The length, width, and thickness of tidal sand bars, as well as the length and thickness of the internal shale layer, are also analyzed. The results show that in the environment of a tide-controlled estuary, the tidal range has a more significant effect on tidal sand bars compared to the sediment grain size under the specific conditions used in this study. The main effect of tidal range on tidal sand bars is that the greater the tidal range, the greater the length-to-width ratio of the sandbank, and the higher the degree of sandbank development. In a tidal-controlled estuary environment, the formation and distribution of shale layer structures are also affected by tides: the length of the shale layer increases as the tidal energy increases, but the changes in the thickness are not obvious. Numerical simulations of the development and distribution of the tidal sand bars and shale layers in estuaries based on sedimentary dynamics will provide a basis for the sedimentary evolution of tide-controlled estuaries and will provide guidance for the exploration and development of tidal estuaries

A model of production data analysis for horizontal wells

The production data analysis is one of hot spots of reservoir engineering recently, which combines conventional reservoir engineering analysis and modern well test analysis. Based on the theory of transient porous flow, the analysis provides a mathematical model, which not only reasonably predicts the production decline of oil or gas wells but also effectively evaluates the physical properties of reservoirs. Theoretical charts of Agarwal-Gardner production decline curves and derivative curves for common horizontal wells are presented by solving the transient 3D porous flow in the bounded reservoir. The Agarwal-Gardner curves can be divided into two stages: the derivatives are dispersed in the early transient decline stage and drawn to Arps harmonious decline in the late pseudo-steady state stage. The influence of vertical location of horizontal wells on production decline in the mid-long term is negligible in a homogenous reservoir. A field example illustrates that, given production data, the results in this article can be directly used to evaluate the reservoir characteristics and effectively forecast the long-term productivity for horizontal wells. 摘要: 生产数据分析是近年来油藏工程的研究热点之一, 它以不稳定渗流理论为基础, 集常规油藏工程分析和现代试井分析之优势形成新的数学模型, 既能合理预测油气井产量递减又能有效评价油气层物性。通过求解封闭地层水平井的三维不定常渗流问题, 可得普通水平井的Agarwal-Gardner型产量递减曲线以及产量递减导数曲线理论图版。分析表明, Agarwal-Gardner型产量递减曲线可以分成2个阶段, 前一段是不稳态递减段, 其导数曲线不归一, 而后一段为拟稳态递减段, 其导数曲线归一, 接近于Arps调和递减趋势; 对于均质储集层, 水平井的垂向位置对中长期产量递减规律影响很弱, 可以忽略。矿场实例说明在已知生产数据的条件下利用该结果可直接评价储集层特性, 并对水平井中长期产能进行有效预测。 Key words: horizontal well, production data analysis, rate decline, material balance time, transient 3D porous flo

Digital Predistortion Combined with Iterative Method for MIMO Transmitters

In this article, an auxiliary module is proposed to mitigate the crosstalk effect in multiple input–multiple output (MIMO) transmitters. Other branches do not need considering when linearizing the local branch, which reduces the complexity of the auxiliary module, and some branches can be linearized selectively to make the module application more flexible. In the end, the feasibility of the proposed algorithm is verified through the experimental platform. Experimental results demonstrate that for a 2 × 2 MIMO transmitter with −20 dB nonlinear crosstalk, the proposed DPD improves the adjacent channel power ratio (ACPR) more than 16 dB, and normalized mean square error (NMSE) more than 12.8 dB, which has similar performance to the PH model. The predistorter can be implemented with fewer coefficients by separating the crosstalk from the nonlinearity, enabling the technique to be used in 5G massive MIMO scenarios

Different-Shaped Ultrafine MoNbTaW HEA Powders Prepared via Mechanical Alloying

Different-shaped ultrafine MoNbTaW high-entropy alloy powders were firstly prepared by a convenient mechanical alloying method. The phase composition and microstructure of the powders were characterized. The powders are ultrafine with nano-sized grains and a good homogeneous microstructure. All the powders have a single body-centered cubic solid solution phase and form the high-entropy alloy during mechanical alloying. These powders with different shapes are quite attractive for developing high-performance MoNbTaW high-entropy alloy bulk and coatings combined with a following sintering, spraying, or additive manufacturing technique

Measurement Method of Magnetic Field for the Wire Suspended Micro-Pendulum Accelerometer

Force producer is one of the core components of a Wire Suspended Micro-Pendulum Accelerometer; and the stability of permanent magnet in the force producer determines the consistency of the acceleration sensor’s scale factor. For an assembled accelerometer; direct measurement of magnetic field strength is not a feasible option; as the magnetometer probe cannot be laid inside the micro-space of the sensor. This paper proposed an indirect measurement method of the remnant magnetization of Micro-Pendulum Accelerometer. The measurement is based on the working principle of the accelerometer; using the current output at several different scenarios to resolve the remnant magnetization of the permanent magnet. Iterative Least Squares algorithm was used for the adjustment of the data due to nonlinearity of this problem. The calculated remnant magnetization was 1.035 T. Compared to the true value; the error was less than 0.001 T. The proposed method provides an effective theoretical guidance for measuring the magnetic field of the Wire Suspended Micro-Pendulum Accelerometer; correcting the scale factor and temperature influence coefficients; etc