裂缝性白云岩油藏酸压滤失机理与应用研究

【作者】 吴芒；

【导师】 赵金洲；

【作者基本信息】 西南石油大学 ， 油气田开发工程， 2006， 博士

【摘要】 低渗透非均质白云岩油气藏是目前我国很重要的一类碳酸盐岩油气藏，酸化压裂工艺技术逐渐成为这类油气藏勘探、开发和增储稳产的关键技术之一。低渗透非均质白云岩储层具有储层渗透率低、天然微裂缝比较发育、储层纵向上非均质性较强、缝洞系统是油气储集和渗流的主要介质等特点。在高排量的酸压施工过程中，过量酸液溶蚀较大的孔隙或天然裂缝而形成形态复杂的酸蚀蚓孔，因此常常出现酸液过度滤失，严重制约了酸蚀主裂缝的延伸，引起酸蚀作用距离不够、酸压改造作用范围有限，直接导致了油气藏增产效果不佳甚至施工失败。主要原因是对酸液的滤失机理了解不明了，酸液滤失量计算不准确。 因此，研讨酸液滤失机理、建立合适的酸压计算模型、设计控制滤失方法为增产技术人员历来所关注，对于提高酸化压裂效果具有重要的意义。 本论文在采用长岩心酸岩反应与滤失综合实验基础上，建立了不同地质条件下的酸液滤失物理模型，对酸液滤失进行了室内实验，以研究酸压过程中酸蚀蚓孔发育机理和酸液滤失机理；并将酸蚀蚓孔简化为单圆管模型，利用酸液流动反应物质平衡方程来反应传质和扩散作用，建立了考虑酸蚀吲孔的酸液滤失计算模型，并在此基础上建立了考虑酸液在纵向上的流动和反应以及纵向上压力变化的酸压数学模型；同时针对这种裂缝发育的非均质白云岩储层，通过大量的有机合成试验以及酸液体系综合评价试验研制了一套粘弹性表面活性剂降滤失酸液体系。 论文研究表明： 1、酸压施工中酸液滤失量应由酸液人工裂缝壁面基质滤失、蚓孔壁面滤失和蚓孔的体积扩展三部分组成。酸蚀蚓孔滤失占酸液总滤失的比例较大，对酸压效果具有不可忽视的影响。 2、酸蚀蚓孔滤失量与排量、酸液粘度、酸液浓度、注酸时间以及储层物性有密切关系。通过优化相关施工参数和采取相应工艺措施可以有效降低酸蚀蚓孔滤失，提高酸蚀有效作用距离。 3、结合三维裂缝延伸模型以及考虑酸液纵向传质的基础上的酸液流动反应模型，利用Visual Basic 6.0编程语言编制了考虑酸蚀蚓孔滤失的酸压设计程序，以便能更好地指导酸压施工设计，并在现场实际应用中对本文模型不断修正和完善。 4、常规的聚合物酸液在裂缝性白云岩酸压中的效果不好，可在酸液中加入粘弹性表面活性剂，在储层中形成粘弹性表面活性剂凝胶的高粘性来降低滤失。因此，研制新型的粘弹性表面活性剂酸液体系对于提高这类油气藏的酸压效果具有重要的意义。更多还原

【Abstract】 Low permeability and herterogenous dolomite reservoir is one of the vital cartonate-rock reservoirs. Acid fracturing technology is becoming a key technology of petroleum exploration,development and increase reserves and stabilize production for this reservoir.low permeability and herterogenous dolomite reservoir is chariterisized with low permeability in matrix, the natural fracture and developed cavity, storng heterogeneity . so, the fracture and cavity system is the main medium of the oil/gas storage and penetration. Wormhole is formed inevitabiy during the process of high pumping rate acid fracturing treatment, which results in serious acid leak-off and short acid penetration distance. Thus this directly leade to a bad effect on the carbonate stimulation, and even brings the treatment into failure. Generally, the main reasons for the failure are the unclearness of acid leak-off mechanisms and the inaccurate calculation of the acid leak-off in the naturally fractured carbonates.So, the acid leak-off mechanism and the design of the controlling the leak-off method have been the concerned for the stimulation technician, and it plays a significant role in improving the acid fracturing effects.Based on the long core parallel plate acid-rock reaction model and the acid dynamic leak-off experiment, we have developed a set of acid leak-off physical model for different geologic condition and have developed a set of acid leak-off experiment,which is to analysis the initiation and propagation mechanisms of wormhole and the acid leak-off mechanisms during the process of the acid fracturing.acid leak-off mathematical model was built up bymodeling the wormhole as a cylinder and numerically solving the mass balance equation that describes acid transport by convertion and duffusion.baded on that and considered the acid fracturing model is developed.for fractured heingt and the variational pressure,the acid fracturing model is developed .for fractrured herterogenousdolomite reservoir,on the other hand,we have developed a suit of Viscoelastic surfactant fluid loss acid system by a number of organic synthesis experiment and a series of comprehensive ecaluation experiment for this acid system.It’s illustrated in this paper sa following:1、 The acid leak-off in the acid fracturing treatment falls into three parts:1)the leak-off in matrix,2)the leak-off on the wormhole wall and 3)the increase of wormhole volume.this paper presents an acid fracturing mathematic model,including wormhole leak-off.2、 The acid wormhole leak-off volume is concerned with the pumping rate,the acid viscosity,the acid concentration,acid injection time and the formation physical property.The acid wormhole leak-off can be decreased effectively and the available acid penetration diatance is improved by optimixing the interest treatment parameter and adopting thecorresponding procedure treatment.3、 Based on the three-dimensional model of fracture extension and the model of acid flowing and resction with rock, a acid fracturing design procedure,considering the acid wormhole leak-off,has been programmea with the Visual Basic 6.0 software to guiding the acid fracturing treatment in the carbonate reaervoir,and the model in this paper is modified and improved during the application on the field.4、 the effect of acid fracrueing is not good by using the conventional polymet acid system,so we can adding the ciscoelastic surfactant into the acidixing fluids to low fluid loss更多还原