查看更多>>摘要：In current storage unit, spiral tubes were employed which is full of hot hybrid nanomaterial. The hybrid fluid become hot due to existence of sun and to use such heat the pipe was employed in storage unit which is full of RT82. To make it more effective, instead of straight pipe, spiral one was utilized. Two types of configurations were implemented with equal PCM volume. The difference of two cases is position where hybrid fluid exits the system. For validation, LF was evaluated and data were compared with experimental data. Outputs in term of temperature and solid fraction distribution as well as velocity distribution can help us to find which style is more applicable. Using spiral pipe is very common in industry because of lower sedimentation. In taypel, changing time from 10 to 30 min leads to change in solid fraction from 0.638 to 0.094.
查看更多>>摘要：The most recent study shows that a rigorous Darcy flow does not exist in hydraulic fractures due to the effect of viscous shear from fracture walls, and the Brinkman equation can be a more accurate method to characterize the fracture flow (Teng et al., 2020). For Darcy flow, the fracture permeability is equivalent to the proppant-pack permeability, whereas, for the Brinkman flow, the fracture permeability is related to the fracture width as well as to the proppant-pack properties. In this work, the authors conducted a comprehensive study of the effect of Brinkman flow on the performance of fractured wells by use of a proposed semi-analytical model. In addition to the Brinkman flow, this proposed semi-analytical model also can account for the geomechanical effect to describe the stress-dependent proppant-pack properties and fracture width. The calculated results in this work show that the fracture permeability is lower than the proppant-pack permeability ascribing to the effect of Brinkman flow. As the production proceeds, the Brinkman flow will play a more important role in influencing the fluid transport within propped fractures. The effect of Brinkman flow on the well performance is significant only if the geomechanical effect is considered. If the fracture volume is sufficiently large or the proppant-pack permeability is sufficiently high, a longer fracture can be more favorable for improving the well productivity. If the Darcy parameter (defined in Eq. (22)) of the hydraulic fracture is less than 0.001, the long-term cumulative production of the fractured wells will not be influenced by the Brinkman flow. If the Darcy parameter is larger than 0.001, the effect of Brinkman flow cannot be neglected unless the Darcy-flow dimensionless conductivity is sufficiently large.
查看更多>>摘要：Implementing an effective automatic history matching (AHM) is essential for the shale gas reservoir characterization and production optimization. Embedded discrete fracture model (EDFM) has been recognized as an efficient forward model used in AHM, in which the properties of multiscale fracture planes are required to be properly assigned. However, the multiscale fracture characterization based on the induced microseismic events (MEs) is still unclear, resulting in the over-simplified fracture planes used in the EDFM simulator. To estimate the properties of multistage fractured reservoir more accurately with both production and microseismic data, a new two-step history matching workflow is proposed. The energy-based K-means clustering (EBKC) is applied to characterize the distribution and geometry of multiscale fracture planes based on mutistage microseismic events (MEs). The obtained fracture planes are then used as prior model parameters in the Ensemble Kalman Filter (EnKF) based history matching method to assimilate the production data. The performance of the proposed workflow is verified by a synthetic case study, and the updated ensemble of production forecast successfully matches the observation data. The uncertainties associated with the updated ensemble of fracture property and permeability of primary fractures are significantly reduced, but substantial uncertainties are still remain for the secondary and tertiary fracture permeability. It indicates that the production data is more sensitive to the permeability of primary fracture. Notably, the highest-frequency component of the updated ensembles matches the observations with less than 20% discrepancy. With the case study, it elucidates that our EBKC approach can successfully characterize the multistrand fractures implemented into a computationally efficient forward model, i.e., EDFM for multistage fractured shale gas reservoir. Therefore, the proposed AHM workflow is recommended for field application.
查看更多>>摘要：Formation damage and the associated injectivity loss of wells induced by the produced water re-injection can be often overcome by injecting in the fracturing injection regime. This paper presents an experimental investigation of fracturing mechanisms induced in unconsolidated sand reservoirs under fluid injection using a new radial injection setup. The development of the injection cell is based on a radial injection configuration within a classical triaxial cell to simulate the injection wells conditions and this cell allows the whole specimen to be scanned using X-ray Computed Tomography (X-ray CT). Typical test results exhibit pressure drops during fluid injection corresponding to fracturing of the specimen, and consequently to an increase of the overall permeability. This can be confirmed by the detection of small radial fractures ('pseudo-cracks') around the injection point either by visual observation when disassembling the specimen or by 3D X-ray CT. Fractures appear as localized zones of higher porosity and larger pore size resulting from dilatant shearing and subsequent particles transport. The impact of various parameters (confining pressure, stress ratio coefficient, flow rate, permeability) on the fracturing process in sand specimens is explored. The obtained experimental results suggest that confining pressure is a key parameter controlling fracture initiation.
Vladimir A. NovikovDmitriy A. MartyushevYingwen Li
14页
查看更多>>摘要：Acid stimulation of carbonates is the most common method of production intensification in practice of hydrocarbon field development. Injection of acid compositions improves hydrodynamic connection of the wellbore with the reservoir by creating extended filtration channels - wormholes. Wormholes increase the effective drainage radius of production wells, which provides incremental oil. Scientists around the world have conducted a considerable amount of experimental and numerical research at the fundamental level aimed at studying the complex process of interaction of acid compositions with carbonate rock. The results of the studies repeatedly noted the critical role of technological parameters of acid treatment, the competent choice of which often provides a positive result of stimulation. However, a significant number of studies have been performed and tested only at the theoretical level or under ideal laboratory conditions, and their transfer to real heterogeneous productive reservoirs turns out to be a failure. Our study demonstrated a fundamentally new approach to justify the technological parameters of acid stimulation of carbonates (volume of acid and reaction time) based on laboratory experiments and field studies. We developed a rating matrix that characterized the effectiveness of acid treatments in terms of changes in well performance and reservoir properties, as well as the multiplicity of exposure, for a wide range of technological parameter changes. The application of this approach allows not only to evaluate the effectiveness of actually performed acid treatments, but also to quickly determine the perspective of different design options for future interventions. The operability of matrix was confirmed by positive pilot tests at wells in Perm Krai (Russia), and the test results were 8-31% higher than the planned results. The algorithm we described was useful in designing acid treatments. This method effectively improved the oil and gas recovery under the condition that the reserve structure deteriorated annually and the number of candidate wells decreased.
查看更多>>摘要：Effective spacer design is a key factor in cement's ability to produce a strong bond between the cement-casing and the cement-formation. Mud displacement, mud cake removal, and cement contamination with drilling mud are the different applications of the spacer. Furthermore applications include changing the wettability of the formation and casing, particularly when drilling is carried out with oil-based mud and the production zone is expected to be oil-wet. Oil wet formations can limit cement bonding with the formation, resulting in pressure transmission between hydraulic fracture stages and lack of zonal isolation. This paper investigates how adding surfactants to cement spacer design affects cement bond performance under reservoir temperatures, where the surfactants will help to mitigate the impact of oil base mud on cement performance, reduce drilling mud compatibility issues, change formation - casing wettability from oil-wet to water-wet, and reduce interfacial tension (IFT) between the mud and the cement. The investigation was conducted using Wolfcamp core samples. To simulate the oil well, the core samples were chopped into small pieces and aged in oil-based mud (8.8 ppg and 12.5 ppg) at reservoir temperature for 10 days. The wettability of the chip was then determined using the captive bubble method. The chips were then submerged in a spacer mixture. The experiment was carried out using three different surfactants (Anionic, Nonionic, and Zwitterionic surfactant). The wettability of the chips was tested again after they were exposed to the aforementioned spacers to see how surfactants affected the wettability. The interfacial tension (IFT) between the spacer and the crude oil was also measured. To investigate the mixability issue caused by the presence of surfactants in the spacer design, oil-based mud and spacer compatibility tests were done. In addition, beaker and rotor cleaning experiments were used to assess the efficacy of various surfactants in removing mud.
查看更多>>摘要：Due to the mechanical structure and operating principle of sliding vane pump (SVP), an all-metal artificial lift equipment with high temperature resistance and high pump efficiency, an unbalanced radial hydraulic force always exists in it during oil recovery, which will cause damage on efficiency, safety and service life of production system. What's more, the flow behavior of fluid through the pump cannot be accurately characterized because current related works fails to capture the influence of the force mentioned. To bridge this knowledge gap, in this paper, the computational fluid dynamics method was introduced and used to analyze the radial hydraulic force under different operating parameters for the first time. On this basis, novel measures to reduce this unbalanced force were put forward, and a design scheme of concentric stator-rotor to completely eliminate the radial hydraulic force was proposed. Main results show that a) increase in eccentricity will contribute to the enhancement of discharge capacity, which will simultaneously aggravate the radial hydraulic force. And this force is proportional to the fluid viscosity, lifting pressure difference and rotation speed, b) The direction of radial hydraulic force of adjacent stages in multistage SVP is opposite. To reduce this unbalanced force, it is recommended to use even-numbered (odd-numbered) multistage pump when the number of total stages is small (large), c) The concentric design eliminates the radial hydraulic force at the expense of the function of self-regulating flow rate. Besides, the stator curve under concentric stator-rotor condition will degrade the kinetic characteristic of vanes.
查看更多>>摘要：Salt crystallization will affect the mechanical strength of shale. In the present work, experiments on salt crystallization of shale were carried out, and static and dynamic rock mechanics of shale were analyzed. Meanwhile, the crystallization stress of nanopores and throats with different shapes was calculated. Crystallization stress will induce the initiation and expansion of shale fractures, which will further reduce the mechanical strength of shale. When the pore radius of shale is less than 50 nm, the crystallization stress decreases rapidly. When the pore radius is constant, the larger the throat radius, the smaller the crystallization stress, and the crystallization stress generated when the throat radius is 5 nm is much larger than that generated when the throat radius is greater than 10 nm. Salt crystallization will weaken the mechanical strength of shale, increase the embedding degree of proppant, reduce the effective crack width, and finally hinder the multi-scale transportation of shale gas.
查看更多>>摘要：When designing control valves for multiphase applications using conventional valve sizing methodologies, it is assumed that the flow properties such as mixture density and volume fraction of phases are uniform throughout the valve trim. In reality, however, the properties may be different due to the difference in the gas and liquid densities as well as velocities within the valve which cause phase stratification. Furthermore, complex geometric effects can also cause phase non-uniformity within the valve. Current valve sizing methodologies are based on global parameters such as overall valve coefficient (Cv) which do not consider local phase non-uniformities within the trim during the design phase. Among these methodologies, it has previously been shown that the harmonised Cvs method is the most accurate method of sizing control valves under multiphase flow conditions across a wide range of flow regimes. The current study provides additional equations to be used with the harmonised Cvs method to ensure that the local flow quality compliance is achieved, which seems to be the major weakness of the existing method. In order to obtain local gas and liquid flow rates, pressure drops and phase fractions, well-validated computational fluid dynamics (CFD) simulations were carried out. Two valve opening positions of 60% and 100% were considered each with 5,10, and 15% inlet air volume fractions to simulate real life conditions. The results show that there is severe non-uniformity in the local gas and liquid distributions within the valve trim. To quantify the phase non-uniformities observed, a distribution parameter (Co) based on the drift-flux model was used. The harmonised Cv method was used to calculate the local Cvs and the local equivalent area factor (Ψ). A new equation was derived that considers the local variation of the Ψ factor within the trim and which incorporates the distribution parameter. Based on the foregoing analyses, additional flow distribution equations have been proposed that when used with the harmonised Cvs valve design method for multiphase flow applications will ensure that the deviation in performance of the valve is minimal from the design conditions.
查看更多>>摘要：Due to highly uncertain underground conditions, most estimations of drilling and geological parameters must be performed using numerical modeling, thus by fitting empirical models to measurement data or by using an approach based on data analysis. In this paper, a combination of these two solutions is proposed for a realistic replication of historical drilling data in a drilling software simulator environment e.g., the DrillSIM:600 at Drilling Simulator Celle (Clausthal University of Technology). The whole process ranging from the modeling over the model evaluation and selection to the integration in the simulator environment is integrated within the presented framework. For this study several empirical models and five machine learning algorithms were applied to benchmark the performance on predicting the drilling parameter Rate of Penetration (ROP) using data from a single geothermal well located in northern Germany. The results of the comparison between the classical and the data driven models prove that the use of data analysis methods is a very valuable alternative to explore, describe, diagnose, and predict the underground conditions and drilling parameters. Those can be used to optimize the entire drilling process by replicating critical situations, recommending better practices or emphasizing the proper performance of a whole drilling project. Thus, by turning raw historical data in valuable insights, the further education of decision makers and rig crews can be significantly enhanced.
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