Table of Content

10 June 2020, Volume 42 Issue 3

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GEOLOGY EXPLORATION

Modeling of the Reservoir Architecture of Thin Interbedded Deposits

MOU Zhonghai, LIU Xue, CHANG Lin, SU Qiu, WU Qianran

2020, 42(3):  1-12.  DOI: 10.11885/j.issn.1674-5086.2018.11.21.06

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Taking the braided river deltas of the Q6 Block in the Kunbei Oilfield in the Qaidam Basin as an example, this study investigated methods to model the architecture of thin interbedded reservoir sandstones. Traditional methods are based on the relatively maximum values of natural gamma measurements and (or) positive spontaneous potential abnormalities to determine the boundaries of sub-layers. Meanwhile, the sub-layer division based on the tangent points of reflected and diffracted wavefronts can more accurately depict the thickness and depth of reservoir layers, insulating layers, and interlayers. The interlayers in the study area are dominated by localized mudstones. Hence, two parameters, the thickness of low-permeability layers and permeability return level, were adopted to identify the interlayers. This enhanced the model accuracy. Because the braided river deltas were under the hydrodynamic control of both river and lake waves and the strata are characterized by thin interbedded low-inclination sand-mudstones, this study proposes that strict data control, hierarchical modeling and reservoir layer/interlayer nesting should be included to construct an architectural model of the thin interbedded deposits. Subsequently, an architectural model for the braided river deltas of the Q6 Block in the Kunbei region was established. Analysis of the relationships between the architectural units of the model shows that there are four types of architecture in the target layers. They are lateral stitching, lateral separation, progradation, and accretion. Among them, the lateral stitching and vertical accretion modes of the sand bodies are the most developed. Compared to the traditional modeling method, the proposed method is more advantageous and sensible for thin interbedded deposits.

Quantitative Evaluation of Faults Convergence Ridges Transport Capability and Its Controlling Effect on Hydrocarbon Accumulation

LI Honglin, ZHANG Rucai, WANG Bingjie, ZHANG Jiangtao, WANG Xin

2020, 42(3):  13-20.  DOI: 10.11885/j.issn.1674-5086.2019.08.04.04

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In order to study the causes of differential enrichment of oil and gas in Lüda 16 Oilfield, we identified the convergence ridge of oil source fracture and evaluated their transporting capacity, and explored the controling effect of the convergence ridges of fault on the distribution of oil and gas by means of three-dimensional seismic, curvature property of faults and threedimensional thermal history simulation etc. The results show there are 10 convergence ridges developing in oil source faults in the study area. The transport abilities of converging ridges differ noticeable due to by the coupling of bending degree, matching relationship between activity and source rock and strike-slip tectonic stress. The comparison of drilling results shows that the convergence ridge of fault has obvious control effect on hydrocarbon accumulation:(1) converging ridges of faults control the shallow hydrocarbon distribution; (2) the transport ability of converging ridges control hydrocarbon enrichment degree of fault blocks. The study of convergence ridges of faults has important guiding significance for oil and gas exploration in complex fault block areas. The study can provide technical support and theoretical reference for the optimization of high-abundance fault blocks in complex fault areas.

The Formation Mechanism of the Complex Fault System and the Mode of Oil and Gas Enrichment in South Baxian

WANG Aiping, CHEN Tao, ZHANG Tingjing, WANG Gang, DU Binshan

2020, 42(3):  21-30.  DOI: 10.11885/j.issn.1674-5086.2018.11.19.01

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An in-depth study was performed on the formation mechanism of dominant faults and all levels of micro-faults in the South Baxian area, and on the relationship between their combination and the mechanism of its control over oil and gas, on the basis of which, the distribution of oil sands can be effectively predicted. By using seismic, drilling, and logging data, combined with knowledge of geometry and dynamics, we have obtained a more systematic understanding of the faults and their microstructures in the South Baxian area. On this basis, we have confirmed the mode of oil and gas enrichment in complex fault systems by analyzing the evolution history of oil and gas accumulation, reservoir lithology, and physical properties. This study shows that the Xianbei fault is a reversed-S-shaped right-lateral three-step strike-slip fault under the influence of the Maxian fault. The Xianbei fault controls the formation of the South Baxian middle and shallow tectonic belt. The associated microfaults of the extensional zone expand from west to east, developing into three types of micro-faults, namely oblique bands, pinnate bands, and horsetail bands. The South Baxian oil and gas field is a homologous oil-gas reservoir. It was formed in two stages, its middle and shallow reservoirs being the tectonic-lithologic secondary fault block reservoir type. Three modes of oil and gas enrichment, namely fault oil control, micro-structure oil control, and sedimentary-phase control, are established. It is determined that the micro-structure of small beach-bar sand bodies with single-layer thickness in the pinnate band of the Xianbei fault is the area of oil and gas enrichment. Accordingly, five development wells are deployed in this area and the result of gas-testing is good.

Analysis of Rock Types and Sedimentary Environment of Dengying Formation, Zhenba Area

HOU Mingcai, HE Liang, XU Shenglin, TANG Zhijiang

2020, 42(3):  31-42.  DOI: 10.11885/j.issn.1674-5086.2020.02.19.02

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As a high-quality reservoir of the lower assemblage, the Dengying Formation have been proved by the oil and gas exploration. However, the distribution of reservoir is not yet clear. Based on the outcrop of Dengying Formation at Luchi section, Zhenba Area, this paper carries out a detailed study of the sedimentary microfacies. Furthermore, combined with microscopic characteristics, the sedimentary characteristics and genesis of eight types of rocks are sorted out and explained. These rock types include micritic dolostones, residual dolarenite, stromatolite dolostones, thrombolite dolostones, microbe-bonded dolarenite, argillaceous siltstone, argillaceous dolostones and (dolomite-bearing) siliceous rock. The sedimentary environment of Dengying Formation in the study area is open carbonate platform, which has experienced two transgression-regressive cycles.The carbon and oxygen isotope and trace element data indicate that the sedimentary paleoenvironment during deposition of Dengying Formation changed dramatically. On the whole, the deposition period of the Dengying Formation is roughly featured with the decreasement of seawater salinity, increasement of seawater temperature and gradual increasement of oxygen content, but the environmental fluctuations may exist.

Micro-amplitude Structure Identification Method and Its Application in X105 Block

HE Yingwei, CHEN Guofei, BAO Peinan, TIAN Wei, FENG Deying

2020, 42(3):  43-50.  DOI: 10.11885/j.issn.1674-5086.2018.10.23.01

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The micro-amplitude structure is a remaining oil-enriched area that has not been affected by water injection in oilfield development. The micro-amplitude structure in X105 Block is well-developed. Because of its small scale, it is difficult to identify with seismic data. In order to improve the accuracy of micro-amplitude structure recognition, the author of this paper conducts technical research on three aspects to improve the accuracy of basic data. The first is to develop high-fidelity processing of seismic amplitude by improving the imaging precision of micro-amplitude structure. The second is to innovate the method of horizon interpretation of phase-constraints, which improves the interpretation accuracy of the top interface of sandstone formations. Thirdly, "contradiction between deep and shallow stratum" and other well-quake matching relationships are used to screen the micro-magnitude structure and eliminate the false. The above methods can be used to re-recognize the characteristics of the micro-amplitude structural development and guide the development of remaining oil.

Research on NMR Denoising Method Based on Empirical Mode Decomposition

LI Haitao, DENG Shaogui, WANG Yuexiang, HE Xuquan

2020, 42(3):  51-59.  DOI: 10.11885/j.issn.1674-5086.2019.09.16.32

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NMR has unique advantages in pore structure evaluation and fluid identification, but NMR signals are easy to be influenced by noise. This paper presents a kind of denoising method according to time and frequency domain characteristics of NMR noise based on EMD. Firstly we decompose noise and noisy NMR signals using EMD. Then we determine guidelines of signal-noise separation using curve trend method and improved zero-crossing rate curve. Finally we add useful signals to residual term to obtain pure signals. It is confirmed by core data and logging data experiments that the denosing results are better than wavelet threshold and EMD-wavelet threshold method and porosity calculated is closer to real porosity and the inversion results are consistent with actual pore structure. The denosing method based on EMD can improve signal to noise ratio and reserve pore structure information.

Application of Probability Method in the Reserves Risk Evaluation of Lithologic Gas Reservoirs

YIN Tao, YANG Yiming, JIN Suobao, JIANG Qianfeng, MENG Dewei

2020, 42(3):  60-68.  DOI: 10.11885/j.issn.1674-5086.2019.09.16.04

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Sulige Gas Field is a typical tight and lithologic gas reservoir, with the reservoir characters of variation and heterogeneity, which makes it difficult to evaluate the risk of reserves using determine method objectively. Probabilistic method is used in the X Block to evaluate the uncertainty and risk of reserves. Through the probability distribution function of each variable and multiple random simulation calculations, the uncertainty of gas reservoir parameters and reserves corresponding to different risks are quantitatively evaluated. Combined with single-factor sensitivity analysis, the main risk factors of gas reservoirs are identified and the reserves calculated by the geological model are optimized. And the following research results were obtained. First, the probability distribution of geological reserves simulated by probability method provides the geological reserves under different risks, which is helpful for investment decision and development plan formulation. Second, the sensitivity analysis of parameter variables can determine the main parameters affecting the reserves results of each layer, rank the sensitivity of parameters, estimate the impact of variable change interval on the reserves results, shorten the reserves evaluation cycle and improve the evaluation accuracy. Third, the reserves of the geological model were compared with the reference reserves (P₅₀) of the probabilistic method. Combined with the single-factor sensitivity analysis, the model attribute parameters were adjusted, and the error between the reserves of the optimized geological model and the reference reserves of each small layer in the X Block was within 10%. In conclusion, the probability method gives the reserve scale of lithologic gas reservoirs under different risks, which can objectively evaluate the reserve risk and achieve the purpose of optimizing the geological model.

Methods of Detailed Geological Modeling of Reservoir Interlayers in Thick Marine Sandstones

WANG Kaiyu, WANG Chao, FAN Jiawei, XU Yanlong, RAN Lijun

2020, 42(3):  69-79.  DOI: 10.11885/j.issn.1674-5086.2018.11.18.02

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This study takes the Carboniferous Donghe sandstone reservoir in the Donghe 1 Oilfield in the Tarim Basin as an example in geological modeling. It starts with a detailed single-well identification of interlayers and stratigraphic comparison of wells and employs a geological knowledge base for interlayers as well as test and dynamic data of cores to construct a three-dimensional geological model for the interlayers. It is believed that, by improving the division contrasts between the stratigraphic layers, the spatial distributions of the interlayers between and within the stratigraphic layers can be examined based on existing geological knowledge. Deterministic modeling is employed to place the spatial distributions of interlayers into the geological model. As a result, accurate three-dimensional spatial relationships between the interlayers and reservoir layers are obtained. Test data of interlayer core samples are used to establish an explanatory model for their physical properties. The explanatory results for porosity and permeability are adopted as inputs to create an interlayer property model. Thus, the results better reflected the actual underground conditions. Subsequent numerical simulation using tens of million grids demonstrates that geological modeling of reservoir interlayers in thick marine sandstones by integrating the geological knowledge base as in this study and numerical simulation with the geological model can yield satisfactory results.

OIL AND GAS ENGINEERING

A Study on the Influence of Property Structure Before and After the 9-point Well Pattern Arrangement

XIONG Yu, LIU Cheng, ZHOU Wensheng, LIU Chen, ZHONG Hao

2020, 42(3):  80-96.  DOI: 10.11885/j.issn.1674-5086.2019.10.04.02

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In the study, through the large-scale core experiment, the pressure structure time-varying curve caused by the difference of the physical structure from the homogeneous core to the multi-level heterogeneous core nine-point well network to the row-like encryption is tested. Combined with the time-varying test results of three-dimensional oil saturation in core, the variation law and characteristics of water drive under the double influence of physical structure difference and pressure structure difference are studied in detail, including characteristics of flow field change and remaining oil distribution are discussed. The results show that from large homogenization to interlayer heterogeneity, the pressure of high permeability layer is moderate, the pressure drop is small, and the pressure drop of low permeability layer is large, and the pressure difference between layers is 3 MPa, high permeability layer and low. The degree of water flooding control in the permeable layer differs by 14%. From the interlayer heterogeneity to the intralayer heterogeneity model, the heterogeneity between the wells leads to variable flow around the main flow line; the front edge of the water drive is difficult to regulate and promote effectively; the more serious the degree of heterogeneity, the lower the degree of water drive, the greater the pressure drop. After the well network encryption adjustment, the drainage of water discharge pushes the water-driven front edge in parallel, which significantly improves the plane contradiction between the pressure and heterogeneity between the wells. The pressure difference between the vertical and the upper layers gradually disappears, and the inter-layer contradiction is alleviated. The degree of water driving of the two types of heterogeneous models is improved by 30%, but for reservoirs with strong heterogeneity, the existence of large-scale low-permeability zones is still the main enrichment area of remaining oil.

Discussion on the Development Model of CO₂ Flooding in Low Permeability Reservoir in North Jiangsu

CHEN Zuhua, SUN Lei, YANG Zhengmao, ZHENG Yongwang, YU Xiaowei

2020, 42(3):  97-106.  DOI: 10.11885/j.issn.1674-5086.2019.10.25.02

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CO₂ flooding is an effective method for improving the develop effect of low-permeability reservoir. Sinopec East China Oil and Gas Field has been conducting field experiments in North Jiangsu low-permeability reservoir for 30 years. According to the experience, the current gas injecting blocks are divided into 4 types based on different reservoir characteristics and injecting periods. This paper elaborates the corresponding developing mode for each type of block. Among them, synchronizing injection is suitable for low-permeability reservoirs which are deep and water-sensitive; injection after exhaustion can substantially raise the single well deliverability of high-inclination-angle low-permeability reservoirs which are thin and steadily spreaded; the water-convert-gas injection is suitable for reservoirs with medium-high water cut after water injection; the secondary gas injection development mode is suitable for the low-permeability reservoir which is injected again after gas injection development. The recovery can be increased again by controlling gas channeling through the comprehensive adjustment of development series, injection production structure, injection mode and injection profile. The researching result has a reference significance for choosing CO₂ flooding mode in low-permeability reservoirs.

Research and Application of the Water Isolation Technology for Casing Damage in Jiyuan Oilfield

GOU Lipeng, ZHANG Jinke, YANG Jinfeng, WEI Jiangwei, ZHANG Qian

2020, 42(3):  107-114.  DOI: 10.11885/j.issn.1674-5086.2019.11.22.02

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With the development of the Jiyuan Oilfield for many years, the comprehensive water of the oilfield has gradually increased, the wellbore corrosion has become serious, and the number of the casing damage well has increased year by year. Because of the well casing damaging, the injection-extraction well pattern is out of control、the use of water drive degree is reducing, and the remaining oil is not producted effectively. The wells is not mined normally and oil fields is also not mined stablely, which causes huge economic losses in the Jiyuan oilfield. Therefore, how to govern the wells effectively, has become an important task in Jiyuan Oilfield. In this paper, on the one hand, the principle analysis and the effect comparison for field application of Y211, Y341 and bridge plug are firstly obtained, and aslo the defect of field application is got. On the other hand, the LEP long-term isolation packer and the soft metal casing subsidy tool are carried out for solving the problem of the conventional isolation tools. Through the advantages and disadvantages and practical range of different types of mechanical isolation tools are summarized, the effective measures for treating casing loss wells with mechanical isolation tools under different working conditions are obtained. It provides a direction for governing casing damage wells in Jiyuan Oilfield.

Critical Drawdown Pressure of Sanding Onset for Unconsolidated Sandstone Reservoirs when Reservoir Pressure Depleted

SHI Xianya, HUANG Xia, SHI Jingyan, ZHAO Guangyuan, XU Liyuan

2020, 42(3):  115-122.  DOI: 10.11885/j.issn.1674-5086.2019.08.12.01

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Offshore reservoirs are generally exploited without energy supplement, and reservoir pressure depletion will cause rock stress changes which results in an increasing likelihood of serious sand production in the unconsolidated sandstone reservoir. This paper aims at offshore unconsolidated sandstone gas reservoirs, analyzes rock stresses of the borehole wall with impact of reservoir pressure depletion on in-situ stresses. Combining with fully-polyaxial rock failure criterion Mogi-Coulomb, a new sanding Critical Drawdown Pressure (CDP) calculating model. Furthermore, an applicable sanding prediction method for pressure depleted gas reservoir in well whole life cycle is proposed. The model was applied in F gas reservoir, the chart of sanding CDP for Well F-1 in the whole production life cycle is plotted. The research results indicate:initially, the sanding CDP is relatively large; with formation pressure depletion, CDP is reduced step by step until depleted to the critical reservoir pressure, and sand will be produced no matter how small the drawdown is. The research outcomes are consistent with actual oilfield production situation, which can provide some theoretical supports for sand production gas wells.

Research and Application of Chelating Acid Blocking Removal System for Injection Wells

ZHAO Liqiang, CHEN Xiang, SHAN Jincheng, LIU Pingli, LIU Changlong

2020, 42(3):  123-131.  DOI: 10.11885/j.issn.1674-5086.2019.08.18.01

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Aiming at the problem of rock skeleton loosening caused by acidification with conventional fluorinated acid fluid system in offshore unconsolidated sandstone reservoirs, and containing the characteristics of acidification of immobile string in offshore oilfield injection wells and direct conversion of residual acid to normal water injection after acidification, a chelating acid blocking removal system with low corrosion and precipitation under surface conditions is developed. Taking the injection well in Block X of Bohai Oilfield as an example, the causes of poor injection capacity and the effect of plugging removal are analyzed. The results show that the chelating acid blocking removal system has good retardation, corrosion inhibition, scale inhibition, and medium corrosion ability. It can effectively increase the acid action distance, ensure the safety of water injection pipe string, avoid causing rock skeleton loosening and restrain secondary and tertiary precipitation, and effectively relieve the damage of inorganic substances and polymers. The main reasons for poor injection capacity in Block X are the formation plugging by multi-component complex formed by hydration expansion of clay minerals, particle migration, suspended particles, scaling and polymer. The apparent water absorption index of single well increased by more than 65.4% in field application, and the chelating acid blocking removal effect was remarkable, which could be popularized and applied in similar oilfields.

Factors Influencing the Productivity of the Multi-fractured Shale Oil Reservoir with Tighter Clusters

YU Xueliang, XU Yun, WENG Dingwei, JIANG Hao, DUAN Yaoyao

2020, 42(3):  132-143.  DOI: 10.11885/j.issn.1674-5086.2019.12.30.02

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The multi-fracturing horizontal well with tighter clusters is an effective means of developing shale oil reservoirs. Fracture spacing and well spacing are key parameters in the tight cluster hydraulic fracturing design. A discrete fracture network numerical model based on Comsol software is established, simulating multi-fractured reservoir with tighter clusters. The effects of fracture spacing, well spacing and fracture complexity on the stimulation effectiveness are discussed. The results show that, for the target reservoir, the cumulative production of a single well can increase to about 1.63 times by decreasing fracture spacing from 30 m to 10 m. The cumulative production of the target reservoir can increase about 51.17% by decreasing the well spacing from 400 m to 200 m. The 90 d cumulative production of a single well with complex fracture is 39.80% higher than that with simple rectangular fracture. Tight cluster hydraulic fracturing field experiments show that artificial fractures have non-uniform filling characteristics. Fractures characterized by equivalent refining methods can't reflect such characteristics. Therefore, the effects of the remote unpropped fracture on the stimulation effectiveness are also discussed. The effects of the remote unpropped fracture on the annual cumulative production of a single is about 4.38%. Field experiment shows that the multi-fractured horizontal well with tighter clusters could improve the single well production effectively by 79.70%.

Exploration a Downhole Visual Automatic Seeker Drilling Technology

WANG Wei, LI Yongjie, LIU Jiangtao

2020, 42(3):  144-152.  DOI: 10.11885/j.issn.1674-5086.2019.11.13.31

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Compared with traditional geological steering drilling, automatic seeker drilling is capable of automatic seeker information collection, which is the goal that drilling operators have been pursuing. The automatic navigation technology mainly includes several processes, such as formation prediction around wells and three-dimensional visualization, navigation model construction, automatic identification of stratigraphic boundary, and formation characteristics, automatic identification of highquality reservoirs and automatic optimization of trajectory. The first three processes consist of the construction of visual navigation stratum model, which can be used to make macroscopic prediction and indication of the location and ductility of oil and gas enrichment target stratum; automatic identification of stratigraphic boundary, real-time automatic analysis of stratum characteristics and automatic identification of high-quality formation for precise prediction of the boundary position of stratum near drill bit, and to provide real-time lithology, physical properties and oil-bearing property of stratum, so as to accurately determine the drilling side; the automatic trajectory optimization used for automatic plan for the next drilling plan. The implementation of this technology requires the combination of near-bit gamma-ray and far-detection resistivity instruments. The technology has been applied successfully, and the navigation model formed is basically consistent with the actual drilling strata. The application results show that the downhole visual automatic seeker drilling technology provides a new technical means for high-speed drilling construction and improving the drilling rate of high-quality reservoirs.

Relationship Between Water States and Electrical Conductivity of Cement Slurry in Early Hydration

LI Bin, CHEN Sha, GUO Jianhua, LIU Kaiqiang, CHENG Xiaowei

2020, 42(3):  153-160.  DOI: 10.11885/j.issn.1674-5086.2019.01.21.02

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In the cementing of oil and natural gas wells "short-term gas migration" is usually happened during the liquid-solid transition stage of the cement slurry. Understanding the process of cement hydration during this stage is the key to study the mechanism of "short-term gas migration". And electrical conductivity is one of effective method to investigate the hydration degree and microstructure of cement slurry. Therefore, the conductivity measurement instrument was applied to investigate the effects of the stability, hydration rate of the cement slurry on its electrical conductivity. Meanwhile, combining the principle of mass conservation and low-field nuclear magnetic resonance (LF-NMR), the relationship between the water states and electrical conductivity of the cement slurry was investigated. The experimental results showed that the initial electrical conductivity of the cement slurry was determined by the concentration of the pore solution and pore structure in the cement slurry. And the pore structure distribution was more uniformed with increasing stability of the cement slurry, which increases the initial electrical conductivity of the cement slurry from 16.8 mS/cm to 19.4 mS/cm. Moreover, with hydration degree increases a large amount of hydration products form on the surface of cement particles and in pores to change the solid-phase microstructure and pore structure of the cement slurry. It made the free water distributed in large pores change to capillary water or gel water in small pores. Finally, the experimental results show that it can be seen that the electrical conductivity is proportional to the content of free water, evaporable water in the cement slurry.

PETROLEUM MACHINERY AND OILFIELD CHEMISTRY

Full Parameter Analysis of Working Performance of Metallic Progressing Cavity Oil Pump

ZHONG Gongxiang, LEI Pengyan, ZHU Lingchuang

2020, 42(3):  161-169.  DOI: 10.11885/j.issn.1674-5086.2019.02.24.01

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Aiming at the problem that the influences of operation parameters and structural parameters of metallic progressing cavity oil pump (PCP) on its working performance is not clear, the influence of operation parameters and structural parameters of metallic PCP on its working performance was studied. The 3D numerical analysis technology of metallic PCP based on FLUENT computational fluid dynamics software was adopted in the study, and the effects of viscosity, rotational speed and pressure increasement of per stage on Pump displacement, power, volumetric efficiency and system efficiency were obtained. The influence of stator-rotor clearance, eccentricity and stator lead on pump displacement, power, volumetric efficiency and leakage are also discussed. It is further concluded that the structure should adopt higher rotational speed in thermal recovery of heavy oil and lower rotational speed in cold recovery of heavy oil. In addition, the recommended clearance value of stator and rotor is 0.1~0.3 mm, the recommended eccentricity value is 5.0~6.0 mm, the recommended stator lead is 170~200 mm, and the recommended clearance value of stator and rotor is 0.3~0.5 mm; in the heavy oil thermal recovery, the recommended eccentricity should be 4.0~5.0 mm, and the stator lead should be 110~150 mm in heavy oil thermal recovery.

Study on the Gas-liquid Swirling Annulus Flow with the Vortex Tool

SHI Shuzhe, HAN Guoqing, WU Xiaodong, ZHONG Ziyao, LU Kuan

2020, 42(3):  170-178.  DOI: 10.11885/j.issn.1674-5086.2019.04.17.02

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In order to explain the unloading effect of vortex tools, it is necessary to establish a gas-liquid two-phase flow model in accordance with its flow law. Considering the existence of angular velocity in vortex flow, this research adopts the radial and circumferential momentum and angular momentum balance of gas-liquid flow, the governing equation of gas-liquid flow and the parameters such as liquid film thickness, gas-liquid vortex intensity and pressure drop gradient are obtained. The vortex flow experiments are conducted to verify the model. The results of model calculation and experiment show that the pressure drop of gas-liquid flow can be reduced by 5%~20% after the vortex tool, and the mechanism of reducing pressure drop loss by vortex tools is also given. According to experiments and models, it can be concluded that small vortex angle and high vortex intensity tend to reduce pressure drop at low velocity(gas velocity is less than 13 m/s), while high vortex intensity increases additional friction resistance at high velocity(gas velocity is faster than 16 m/s). The decay rate of vortex intensity decreases with the rise of liquid phase velocity and increases with the rise of gas phase velocity. Therefore, based on the research, vortex tools can be optimized to achieve the best liquid unloading effect.

Relationship Between the Shear Effect of the Flowability and Composition of Typical Crude Oils

ZHANG Fusheng, SHAN Dalong, LI Xuening, LIU Guoliang, ZHU Zhuoyan

2020, 42(3):  179-186.  DOI: 10.11885/j.issn.1674-5086.2019.04.21.01

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In order to reveal the intrinsic effect mechanism of shear (including strong pump shear and weak pipeline shear) on the flowability of the crude oil modified with pour point depressant, and to provide decision-making basis for new pipeline construction and pipeline safe operation, crude oil components, wax structure and wax crystal morphology of the five kinds of crude oil are analyzed by GC, ¹H-NMR, DSC and polarization microscope and effect of pump strong shear and pipeline weak shear on the flowability of the five kinds of crude oil modified with pour point depressant are evaluated by the simulation experimental method reported. It is found that only a very small amount of wax crystals precipitate from the crude oil above the wax appearance temperature, the shear has little effect on the wax crystal structure and does not influence the flowability of the crude oil modified with pour point depressant. In the range of the wax appearance peak temperature, there are a large number of wax crystals in crude oil, the strong pump shear can deteriorate the flowability of the crude oil modified with pour point depressant, and deterioration degree is related to the crude oil composition (wax content, resin content, asphaltene content) and wax structure (carbon number distribution of wax, branched-chain degree of wax); the weak pipeline shear can improve the flowability of some crude oil but also can deteriorate the flowability of other crude oil, which is related to crude oil composition and wax structure. The main reason for the above-mentioned phenomenon is that the shear has a great influence on the wax crystal structure and the wax crystal growth at the wax appearance temperature range.