致密油藏吸附油比例及转化率影响因素研究

Due to its large reserves and the advantages of wide distribution, tight oil has an important position in the field of unconventional oil and gas resources. However, reservoir characteristics of nanoscale pore throats connectivity system led to high proportion of adsorbed oil,poor natural energy supply, fast diminishing oil production and a low recovery. Various types of reservoir stimulation technology have become a key issue to enhance the current tight oil production. In the final analysis, to enhance the tight oil production needs to study the increase of free oil and the degree of movable, which makes content rate and transformation regulation of adsorbed oil become a key research. We take Yanchang formation(chang 7) tight oil reservoir in Longdong area of Ordos Basin as the research object, use technology of CT,NMR, rate-controlled mercury injection, multi-function core displacement instrument, effective displacement, spontaneous and dynamic imbibitions experiment, to carry out the research of content rate and transformation regulation in the different condition. To clarify Mathematical relationships the way for conversion of adsorbed oil to free oil in different temperature, time, rate and pressure of displacement, and establish the mathematical relationship of them. Provide a scientific basis for reservoir stimulation measures and development technology policy formulation of tight oil .

致密油因储量大与分布广的优点在非常规油气资源领域中具有重要地位，纳米-亚微米级的孔喉特征使其具有吸附油比例高、能量补给差、油层产能递减快的特点。各类储层改造及开发技术中，致密油产量的提升归根到底是吸附油向游离油转化、可动程度的提高，因此吸附油比例及向游离油的转化规律成为致密油研究的基础与重点。本项目拟以鄂尔多斯盆地陇东地区延长组长7段致密油为研究对象，对吸附油开展“在哪儿，有多少，转化率”由浅至深的系统研究，利用高压压汞、核磁共振及CT扫描技术，明确吸附油与游离油赋存空间的孔喉界限；结合含油饱和度测试，驱替实验和核磁共振技术，厘定吸附油含量及比例，明确吸附油比例与渗透率的关系；结合动态渗吸与核磁共振技术，探明温度、驱替压力/速率、焖井时间及界面张力对吸附油转化率的影响方式，并分别建立不同影响因素与吸附油转化率的数学关系，阐明吸附油向游离油的转化规律，为致密油开发技术的制定提供科学依据。

致密油是指以吸附或游离态赋存于生油岩中或与生油岩互层、紧邻的致密砂岩、致密碳酸盐岩等储集岩中，未经过大规模长距离运移的石油聚集。微观孔喉细小、孔喉分布非均质性强、纳米-亚微米级孔喉连通体系的储层特征导致了致密油藏具有束缚水及残余油饱和度高、可动油饱和度低、自然能量补给差、油层产能递减快、一次采收率低的特点。各类储层改造及开发技术成为目前提升致密油产量的关键，而产量的提升归根到底是致密油藏中吸附油向游离油转化、可动程度的提高，这就使得致密油藏中吸附油比例及向游离油的转化规律成为研究的基础与重点。本次研究以鄂尔多斯盆地陇东地区延长组致密油藏为研究对象，对吸附油开展了“在哪儿，有多少，转化率”由浅至深的系统研究，分析了致密油藏中吸附油与游离油赋存空间特征，明确了吸附油与游离油赋存空间的孔喉界限，建立了区分吸附油与游离油的实验表征方法，测定了吸附油与游离油含量及比例，明确了渗透率与吸附油与游离油含量及比例的关系，建立了吸附油转化率实验测试方法，明确了吸附油转化率的影响因素。相关研究成果和认识可为致密油开发技术的制定提供科学依据。