APPLIED ENERGY
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2022
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IF 11.446
Rukuan Chai,Yuetian Liu,Liang Xue,Zhenhua Rui,Ruicheng Zhao,Jingru Wang
Water reinjection was widely implemented in the geothermal development for not only disposing tailwater but also maintaining reservoir pressure. Accompanying this was the formation damage, especially in the injection of decreased salinity water which was synthesized by adding surface water and condensed water into produced water for inhibiting the process equipment corrosion, treating the cooling tower condensate, and etc. Fine migration is the prevailing mechanism; however, it is insufficient in some scenarios. Multiple experiments were conducted to investigate the characteristics and mechanisms of formation damage of sandstone geothermal reservoirs during the decreased salinity water injection. First, coreflooding (CF), nuclear magnetic resonance (NMR), and contact angle (CA) experiments were conducted to analyze the characteristics of the formation damage. Subsequently, scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), and nanoindentation experiments were implemented to study the corresponding mechanisms. Finally, the damage mode of sandstone geothermal reservoirs in decreased salinity water injection was proposed. The CF, NMR, and CA experimental results indicated that the decreased salinity water injection resulted in severe formation damage, as manifested by the reduction of permeability, shrinkage of the pore-throat, and enhancement of the water-wettability of core samples. That is, formation damage not only indicates that the fluid is more difficult to be injected but also that it is more difficult for the injected fluid to flow. As the salinity decreases, these trends gradually enhance. The SEM results illustrated that fine migration is noticeable in decreased salinity water injection, meanwhile mineral dissolution which causes secondary pores and microfracture is also apparent. Both reactions are enhanced as the salinity decreases. The same conclusion was validated by the XRD and ICP-OES results, as manifested by the decrease in the concentrations of clay, K-feldspar, and plagioclase, and the increase in quartz, as well as the emergence of Si 4+ , Mg 2+ , Ca 2+ , and K + in the effluents produced during the decreased salinity water injection. The nanoindentation results explicated that mineral dissolution weakened the mechanical strength of the minerals, which might effectively facilitate compaction. The elastic modulus and hardness of the quartz, K-feldspar, and plagioclase decreased from 107.5&93.7&72.3GPa and 13.7&10.1&7.4GPa of the original sandstone to 108.1&86.0&69.5GPa and 13.6&10.3&6.4GPa of the deionized water flushed one, respectively. In conclusion, formation damage was synergistically dominated by the external cause of compaction and the internal causes of fine migration and mineral dissolution. These factors compressed the pore-throat, decreased the connectivity of the porous media, enhanced the water-wettability of the sandstone surface, and consequently impeded water flow.
研究领域:
地质学
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石油工程
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地热能开发
✓ 已验证
DOI
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
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2025
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IF 5.2
Quanhang Wang,Jincheng Mao,Jinzhou Zhao,Yanshan Guo,Yvxing Zhang,Jinhua Mao,Zhangxing Chen,Dandan Su,Jianfei Cui,Zhimeng Song,Xu Ping,Shuhui Zhang
Traditional hydraulic fracturing techniques have long been criticized for their deficiencies, including low recovery efficiency, rapid production decline and complex processes. In order to overcome these shortcomings, fracturing-oil displacement integration has been proposed and attracted great attention in the past few years. In this study, a novel hydrophobically associating polymer (HETP) was synthesized and used as an additive to develop a low-damage and high-efficiency imbibition fracturing fluid that meets the fracturing fluid requirements in fracturing-oil displacement integration. A series of experiments were conducted to systematically study and evaluate the properties of the HETP fracturing fluid, including rheology, shear recovery, proppant transport capacity, gel-breaking performance, oil imbibition efficiency, and formation damage rate. The rheology test results showed that the viscosity retention rate of the fracturing fluid was 100.44% at 100℃. The performance tests demonstrated that the HETP fracturing fluid exhibited superior shear recovery and proppant transport capabilities. The evaluations of the broken fluids showed that the HETP fracturing fluids can effectively alter formation wettability, and can promote oil-washing efficiency and emulsifying ability. The spontaneous imbibition test results showed that the broken HETP fracturing fluid exhibited excellent general performance, with a low formation permeability loss of 8.12% and a high imbibition enhanced oil recovery (IEOR) rate of 36.4%, surpassing other molecular fracturing fluids. The oil recovery mechanisms of the HETP factoring fluid are also discussed in details, implying that HETP has enormous potential for future tight oil development.
研究领域:
石油工程
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
ENERGY & FUELS
·
2019
·
IF 3.021
Kaiyu Zhang,Guodong Zhang,Zhuojing Li,Jirui Hou
Low pH fracturing fluids, such as the transition metal cross-linked guar derivative, can reduce the formation damage caused by clay swelling and fines migration in hydraulic fracturing treatments. However, a major disadvantage of the fluids is the uncontrollable rapid viscosity development, especially cross-linking under a pH below 3.0. In this paper, a novel delayed organic zirconium cross-linker with lactate and ethylene glycol as ligands was designed to overcome the shortcoming. Carboxymethyl hydroxypropyl guar (CMHPG), which results in a low gel residue after breaking, was used as the polymer at low concentration. The impact of gelation parameters on the properties of zirconium-CMHPG gel system was systematically investigated using a Sydansk bottle-testing method combined with a controlled stress rheometer. Desirable gelation time delay with agreeable rheological performance could be obtained by optimizing the polymer and cross-linker concentrations even at a pH as low as 2.0. Uniformly and compactly generated 3D network microstructures could firmly lock the free water within the gel, which further improved the thermostability and acid-resistance of the system. Meanwhile, the structures could also maintain the viscoelasticity of the fluid at a high level to ensure the efficient transportation of the proppants. Proppant settling and gel breaking tests demonstrated that the low pH and low polymer concentration gel system generated fewer insoluble residues with an uncompromised suspension performance. Moreover, the formation damage evaluation revealed that the low pH fracturing fluid system produced a better return permeability than the high pH system.
研究领域:
石油工程
·
化学工程
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）