表面活性剂压裂液机理、压裂设计及评估技术研究

【作者】 李曙光；

【导师】 赵金洲； 刘富；

【作者基本信息】 西南石油学院 ， 油气田开发工程， 2005， 博士

【摘要】 本文在系统分析和深入调研国内外研究现状基础上,综合应用表面化学、流变学、流体力学、线弹性断裂力学、传热学、微分方程、最优化理论、计算数学等方面的知识,在表面活性剂压裂液机理、压裂优化设计、压裂分析评估三个方面开展研究工作,取得了以下主要研究成果: ①用透射电镜和扫描电镜等多种实验手段,结合表面活性剂溶液的基础理论,通过对表面活性剂内外在宏观与微观关联性质的分析,研究并认清了表面活性剂压裂液的成胶机理和破胶机理。 ②论证了表面活性剂压裂液以弹性携砂为主的机理,并提出了用悬浮切力指标来表征表面活性剂压裂液携砂性能的方法。 ③研究了压裂设计模型和方法,包括裂缝三维延伸模型、支撑剂运移分布模型、温度场的数值模型、压裂参数优化设计方法等。其中,建立的裂缝三维延伸新模型考虑了地层的多层和非均质特征,能模拟任意多层地层厚度、地应力和岩石力学参数(如泊松比、弹性模量、断裂韧性)变化的影响,适用于各种应力分布模式以及裂缝穿层前后的延伸情况。 ④完善了压裂优化设计的思想,即从实际地层条件出发,以最佳的压裂效果为目标,通过不断自动调整各段压裂液体积、施工排量、地面加砂浓度、支撑剂类型等施工参数,设计出既能得到最佳压裂效果又不发生砂堵的最优施工方案。 ⑤根据压裂井的流动机制,综合考虑变流量退液过程、井筒储存、裂缝壁面污染和多种边界条件等因素,建立了压裂退液阶段的地层与裂缝系统渗流数学模型,提出了渗流数学模型的解法。其中,对变流量问题的解决方法既提高了计算结果的精确度,也使计算速度提高了1000倍以上,可满足实时计算和快速响应的解释要求。 ⑥提出了压裂退液反演参数的自动拟合法,即综合应用逐步线性最小二乘法和约束变尺度法的数值计算方法。 ⑦遵循以数据为中心、可视化操作为主体的原则,研制了压裂优化设计软件和压裂退液反演裂缝参数软件,具有功能强、操作方便、算法稳定可靠、运行速度快、界面友好,结果合理、商品化程度高等特点。应用软件进行了大量的文献对比、理论验证和实例分析,说明了软件的可靠性和适用性,表明软件能满足实际问题的需要。 ⑧研究的表面活性剂压裂液在水敏性较强、地层压力系数低的石南21井区(陆梁)、石南4井区、莫北区块现场应用38井次,应用情况表明,表面活性剂压裂液性能稳定,操作方便,携砂能力强,增产效果良好,对地层的保护作用表现显著,特别适合于低压低渗油气井使用。2003年三区块累计增油60917吨,创利润58635810元,投入产出比更多还原

【Abstract】 This paper based on systematic analyzing and indepth surveying the present situation of researching at home and abroad, integrated applied the knowledge of surface chemistry, rheology, fluid mechanics, linear elastic fracture mechanics, heat transfer, differential equation, optimization theory, computational mathematics, etc., carried on research work in the aspects of surfactant fracturing fluid mechanics, fracturing optimum design, fracturing analyzing and evaluating, achieved the following research findings:(l)Adopted a great variety of experimental media, such as transmission electron and scanning electron microscope etc, integrated with the basic theory of surfactant solution, by means of analyzing the relevance of surfactant between inhesion and extrinsic, macroscopic and microscopic, investigated the gel forming mechanism and the gel breaking mechanism.(2)Put forward the mechanism that surfactant fracturing fluid is mainly elastic sand carry, and the method of using suspending shear force indicating the prop-carrying capacity of surfactant.(3)Investigated fracture design model and approach, that include fracture three-dimensional extension model, proppant migration distribution model, numerical model of temperature field, method for optimal design of fracture parameter etc.. Among others, multilayer and heterogeneity of formation were considered in the newly fracture three-dimensional extension model, therefore it could simulate variety affect, such as multilayer formation thickness, ground stress, rock mechanics parameter (like Poisson ratio, elasticity modulus, fracture toughness), apply to a variety of stress distribution mode and extension before and after fracture breaking through layer.(4)Improved concept for fracture optimal design, that is to say according to formation condition, for purpose of optimum fracture effect, by means of continually and automatically adjust volume of fracturing fluid in each block, displacement, sand proportion in the surface, proppant type, etc., designing optimum operational scheme which could arrive optimum fracture effect and no sand plug.(5)According to flow mechanism of fractured well, considering the process of the return flow of variable flow rate, well bore storage, contamination on fracture surface, and multi-boundary condition, etc., instituted percolation mathematical model between formation and fracture system in phase of the return flow, and put in the solution of the percolation mathematical model. The solution for problem of flow rate is both enhancing the accuracy of calculation and increasing calculation speed by more than 1000 times . It can meet the needs of real-time computation and fast response.(6)Put forward the automatic match method of inversion parameters of the return flow, i.e. the numerical calculation method of comprehensive application stepwise linear least square method and constraint variable measure method.(7)Optimized fracturing design software and inversion parameters software of the return flow has researched. It followed the principle of taking data as the center and can see the operation as main body. They are provided with function strong, operation convenience, calculation way stability and credibility, run speed quick, interface amity, result reasonable, commercialize degree high. The applied software carried on a great deal of literature contrast, theories verification and example analysis. That explained the credibility and the applicability of the software and express the software can satisfy the demand of actual problem.(8)Researched surfactant fracturing fluid has applied 38 wells which locate 21# well area of Shinan,4# well area of Shinan and Mobei.These areas are water sensitive, formation pressure coefficient low. Applied instance indicate, surfactant fracturing fluid is provided with performance stability, operation convenience, carry sand ability strong, increase production effect well, especially adapt to apply at oil field of low pressure and low permeability. In 2003,3 well areas increaseed the oil accumulation 60917t, created theprofits 58635810RMB, input output ratio reached 1: 4.49. It provided the technique guarantee for high efficiency recovery of oil field of low porosity and low permeability and water sensitivity.Returns of this paper in fracturing fluid was affluent in knowledge system of surface chemistry, rheology and hydrafrac engineering. It is good for technique popularizing and development new system of surfactant fracturing fluid. It is hopeful to develop new domain of environmental protection type fracturing fluid. Returns of this paper in fracturing design not only developed and perfected existing three dimensional fracture extend models, and can simulate extend of fracture height more finely, most of all it is importance meaning for fracture increase production reconstruct to oil and gas reservoir that have basal water or top water. Returns of this paper in fracture analyse evaluating technique formed new technique of analyse of fracturing fluid back process and inversion fracture parameter. Relational fracturing parameter can be realize fast and accurate by this technique.It attain the purpose of estimate fracture effect fast and accurate. After research result is transformed productivity.it can part replace buildup of pressure testing of fracture well, reduce testing expenses, make fracturing well produce in advance.更多还原