非离子低分子表面活性剂优选及驱油效率研究

Optimization and oil displacement efficiency of non-ionic low molecular surfactant

郭平 焦松杰 陈馥 贺杰 李英强 曾辉

GUO Ping JIAO Songjie CHEN Fu HE Jie LI Yingqiang ZENG Hui

油气藏地质及开发工程国家重点实验室·西南石油大学，四川成都　610500 提高石油采收率国家重点实验室·中国石油勘探开发研究院，北京　100083 华北油田公司，河北任丘　062552

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu610500, China Research Institute of Petroleum Exploration and Development of CNPC, State Key Laboratory of EOR, Beijing 100083,China Huabei Oilfield Co., Renqiu 062552, China

目前国内外对低渗透油藏开发的主要趋势为注气开发，又以CO2混相驱居多。我国低渗油藏以陆上沉积为主，储量大且非均质性严重，油质较重黏度高一般不易达到CO2混相。为了降低驱油混相压力，在尽量少增加成本的情况下提高驱油效率，找到了一类不溶于水但溶于超临界CO2及原油中的非离子低分子表面活性剂，通过研制复配及溶解性与降黏评价实验，找到了2种表活剂CAE、CAF。以细管实验为载体，采用高温高压配样器配置地层油进行驱油效率评价，筛选确定了一种表活剂CAE。进行溶解式驱替及段塞式驱替以确定表活剂CAE的最佳注入方式；进行不同浓度的驱替实验确定表活剂CAE的最佳注入浓度。研究表明：段塞式驱替为该活性剂的最佳注入方式，最佳浓度为0.2%；表活剂CAE在最佳驱替方式下与纯CO2相比可以提高驱油效率约13.13百分点。该研究为国内低渗透油藏相对有效地降低混相压力、提高驱油效率找到了途径，是我国低渗油藏注气开发研究中值得探索和尝试的方法之一。

At present, the main technique used in developing low permeability reservoirs is gas flooding, especially CO2 miscible flooding at home and abroad. Low permeability reservoirs in China are mainly composed of offshore deposit, and are featured by large reserve but serious heterogeneity. High oil density and high viscosity have made it difficult to apply CO2 miscible flooding. In order to decrease the pressure of miscible flooding and enhance oil displacement efficiency with little cost increase, a kind of non-ionic low molecular surfactants was discovered in the lab which is insoluble in water but soluble in supercritical CO2 and crude oil. Through the experiments of compounded method research and solubility viscosity reduction evaluation, two surfactants CAE and CAF have been found. With small tube as carrier, formation oil compounded by high temperature and high pressure instrument was evaluated the flooding efficiency, and then a surfactant CAE was selected and determined. Soluble displacement and slug displacement tests were carried out to determine the optimal injection method of CAE; on the same time, displacement experiments with different liquid concentration were conducted to determine the optimal injection concentration. The results show that the best choice of CAE injection is slug displacement and the most favorite concentration is 0.2 percent. The application of surfactant CAE in above mentioned condition can improve displacement efficiency about 13.13 percent comparing to pure CO2 flooding. The researches have set a successful example for relative effectively decreasing miscible pressure and increasing flooding efficiency in developing low permeability reservoirs, and should become one of the effective means which we may explore and try in further study of these kinds of reservoirs.