低渗裂缝性砂岩凝析气藏损害机理及有效保护开发一体化新方法研究

The development and utilization of low permeability unconventional reservoirs have been becoming the newly important base of oil & gas reserves growth and energy provision all over the world, and also presenting strongly developing state in the activity of exploration and development. However, these kinds of reservoir have complicated geologic conditions, and then cannot easily be protected and stimulated. For a long time, scholars all over the world still focus almost their attention on finding a single method or single operation and realize certain solution to the problem of effective protection and utilization, and it is lack of systematically research from reservoir characterization, damage mechanisms and effective protection and utilization. Therefore, reservoir characterization should be studied in this project firstly, and then carry out the research on the macroscopic and microscopic damage mechanism of fluid-blocking, retrograde condensation and stress sensitively as well as their influential factors during the drilling/completion, production, fracturing and workover operations, and its prediction software will be also developed. Secondly, the mechanisms and methods are developed for keeping proper formation pressure, enhancing formation pressure and improving drainage rate to minimize fluid-block and retrograde condensation damage, and then low damage film drilling fluids and composite polymer surfactant discharge aiding system should be developed. Thirdly, according to the characteristic of the formation low-permeability and natural microfractures, improving the mechanism of action and the performance of fracturing fluid and operating technology to obtain good fracturing results. Finally，the integrated new method of damage mechanism and effective protection will be developed for low permeability condensate gas reservoir development through systematic, prospective and original research.

低渗难动用储层的开发利用正成为世界各国油气储量增长和能源供应的新生力量，在勘探开发活动中呈现强劲发展态势。低渗裂缝性砂岩凝析气藏有效保护和改造的难度大。长期以来，国内外学者在如何有效保护和高效动用该类储层方面仍多局限于某一环节或单一方法的研究，缺乏对储层特征、损害机理及有效保护开发一体化新方法的系统研究。本研究拟首先从研究致密砂岩凝析气藏储层特征入手，系统研究钻采过程液锁、反凝析、应力敏感等宏观和微观潜在损害机理和主要影响因素，研发出凝析气藏损害预测软件。第二，为有效降低储层钻采过程中的液锁和反凝析损害，建立保压、增能、助排等综合防治机理及方法，并研发防液锁低损害成膜钻井液、复合聚合物表面活性助排剂体系。第三，针对储层基质渗透率低、天然微裂缝发育等特点，改进压裂液作用机理，提高综合性能，改善压裂改造效果。通过系统性、前瞻性和原创性研究，形成低渗凝析气藏损害机理及储层保护开发一体化新方法。

本项目主要针对吐哈丘东油田致密砂岩凝析气藏低孔低渗的地质特点和现有钻采技术的不足之处，系统研究了储层潜在液锁损害机理和多项减轻损害的改进方法和技术。提出了低渗气藏因温度、压力条件改变在储层内部反凝析出的烃基流体及钻采过程中侵入的液相流体在细小孔喉处滞留的实质均为液锁损害不同表现形式的观点。依据凝析气藏生产过程中地层压力对渗流相态变化的影响，全面分析了反凝析现象的动态变化过程，提出了旨在提高凝析油及凝析气采收率的注汽保压、热处理等综合方法，以及控制生产压差和预置醇类加氟硼酸深部酸化相结合的方法，在现场应用中均取得了较好生产效果。.项目主要研究内容和创新点包括：1）在液锁损害试验的基础上，建立了预测液锁损害的灰关联分析方法，研制了智能化快速预测软件，其自检符合率达到95%以上。2）利用不同性能表面活性剂间的协同增效作用，研发了由能够降低表面张力、界面张力以及可增加接触角的表面活性剂和辅助表面活性剂组成的高效助排剂ZPJ－CUP。试验表明，该助排剂可明显提高各种入井液的返排率，有效防止或解除液锁损害。3）应用防液锁、理想充填及成膜剂三项技术的“叠加增效”作用，研制了防止液锁损害的两性离子成膜聚磺钻井液体系。该体系可在井壁上形成致密泥饼和屏蔽暂堵环，显著降低了钻井液对丘东低渗油气层的污染损害程度。4）研发了新型低损害、无固相多功能修井液，使储层岩心的渗透率恢复值明显提高。5）优选出低损害压裂液－双破胶剂配方，既满足地层造缝要求，又具有低伤害、低滤失特点。以上创新改进技术在现场应用中取得了显著的保护丘东低渗气层的效果。由于我国低孔低渗油气藏储量大，分布区域广，预期研究成果对类似油气藏储层保护具有一定的实用性和借鉴意义。