大港油田沧东孔二段页岩油与水的乳化特性及影响因素分析
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1.中国石油大港油田分公司;2.天津市三次采油与油田化学企业重点实验;3.中国石油天然气集团有限公司纳米化学重点实验室大港应用研究室

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TE133

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Emulsification Characteristics and Influencing Factors Analysis of Shale Oil and Water in the Second Member Kongdian Formation of Cangdong Sag in Dagang Oilfield
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    摘要:

    大港油田沧东凹陷孔二段页岩油藏一次压裂开采初期见效明显,但后期能量和产量下降较快,而且采出液乳化严重,导致页岩油采收率降低,集输阻力变大,开发难度增加。本文旨在深入探讨页岩油与水的乳化特性,并分析其影响因素,揭示页岩油与水的乳化原因和乳化机制,并提出解决页岩油乳化增黏的方法。研究结果表明:孔二段页岩油的平均蜡含量高于20%,凝固点高于35℃,而且页岩油重质烃含量越高越利于乳化现象的发生。页岩油中的胶质、沥青质等含氮极性组分,以及蜡晶的存在,导致页岩油与水在流动过程中形成油包水乳状液,产生乳化增黏现象。随着含水量的增加,页岩油黏度呈先增加后降低的趋势,含水量在50%~70%时乳化后页岩油黏度达到最大值,是脱水原油黏度的3.23~7.45倍。升高乳化温度、增加水相矿化度以及侵入压裂液组分,均会使页岩油与水乳化形成W/O乳状液稳定性增强。此外,当乳化页岩油再乳化时,会形成O/W/O多重乳状液,黏度则进一步升高,但当再乳化时添加少量PSG乳化剂可使乳化页岩油从W/O型反相为O/W型,从而降低页岩油黏度,提高其流动性。因此,开展页岩油注水增能时需要考虑页岩油的物理化学性质,同时研发高活性页岩油增产用表面活性剂将是后续工艺设计和产品研发的重点。

    Abstract:

    The primary fracturing in the second member of Kongdian Formation of Cangdong Sag in Dagang Oilfield exhibits significant effects during the initial stage, but energy and output decline rapidly in later stages, and the produced fluids are severely emulsified, resulting in a reduction of shale oil recovery, increasing difficulty of shale oil development, gathering, and transportation. This study aims to investigate the emulsification characteristics of shale oil with water in-depth and identify their influencing factors, thereby revealing the reasons and mechanisms behind shale oil emulsification, and thus proposing solutions for issues related to thickening due to this phenomenon. The findings reveal that the average wax content of shale oil in the second member of the Kongdian Formation exceeds 20%, with a pour point above 35°C. Moreover, the high content of heavy hydrocarbons favors the occurrence of the emulsification phenomenon. Nitrogen-containing polar compounds (i.e. asphaltenes and resins) and wax crystals facilitate the formation of water-in-oil (W/O) emulsions under flow conditions, resulting in thickening attributed to these emulsification processes. The viscosity of shale oil increases first and then decreases with the increase in water content. It reaches a maximum when water content ranges from 50% to 70%, attaining viscosities that are 3.23 to 7.45 times higher than that of dehydrated shale oil. The stability of W/O emulsion formed through the emulsification process of shale oil and water is enhanced by increasing emulsification temperature, increasing salinity of the water phase, and intruding fracturing fluid composition. Additionally, O/W/O multiple emulsions will be formed when emulsified shale oil is re-emulsified, further increasing the viscosity of the shale oil system. However, introducing a small amount of PSG surfactants during this re-emulsifying process can reverse the configuration from W/O back into an O/W structure for the resultant emulsion, thus reducing the viscosity of shale oil and improving its fluidity. Therefore, it is necessary to consider the physical and chemical properties of shale oil when conducting water injections and energy enhancement for shale oil reservoirs. Simultaneously, the development of high-activity surfactants for shale oil stimulation will be a focal point for subsequent process design and product research and development.

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  • 收稿日期: 2024-09-18
  • 最后修改日期: 2024-10-29
  • 录用日期: 2024-11-05
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