特低渗透油藏CO_2驱油室内实验与矿场应用

延长石油特低渗透油藏储量丰富,注水开发中存在易水敏、注水困难等问题。CO_2驱能有效补充地层能量,改善地层原油性质,进而提高油藏采收率。利用CO_2-地层原油接触实验、岩心渗流和驱替室内实验,描述CO_2-地层原油两相渗流特征,分析CO_2驱油机理和驱油特征,并在靖边特低渗油藏进行了矿场实验。研究表明,特低渗储层CO_2-原油油气两相共渗范围大,CO_2具有降低原油黏度,使原油体积膨胀等作用,非混相驱和混相驱均可较好地开发特低渗透油藏,其中生产井见气前与低气液比阶段是油藏主要生产期。CO_2驱矿场试验表明,特低渗透油藏注气能力是注水能力的2倍,注气能快速有效补充地层能量,增加油田产量,目前试验区生产整体呈日产液、日产油上升态势。

INDOOR EXPERIMENT AND FIELD APPLICATION OF CO2 FLOODING IN ULTRA-LOW PERMEABILITY OIL RESERVOIRS

The ultra-low permeability reservoirs are abundant in Yanchang Petroleum,and moreover the following problems occur in the process of the oilfield development:easy to water sensitivity,difficult to water inject and so forth.CO2 flooding can effectively complement the reservoir energy,improve the crude oil properties and enhance the oil recovery.With the help of CO2-stratigraphic crude oil contact experiment,core seepage and displacement laboratory experiments,the two-phase seepage characteristics of the CO2 and stratigraphic crude oil were characterized,and the CO2 oil flooding mechanism and the oil displaced characteristics were analyzed,and furthermore the field test was implemented in Jingbian ultra-low permeability oil reservoir.The research results show that the CO2-oil two-phase flow has a large two-phase seepage zone in the ultra-low permeability reservoir,and the CO2 has the obvious effects of reducing the viscosity of the crude oil and expanding the volume of the crude oil,both immiscible and miscible floodings can more better develop the ultra-low permeability reservoir,before the gas breakthrough for the producers and in the interval of low gas-liquid ratio are the main production periods of the reservoir.The CO2 flooding field test shows that for the ultra-low permeability reservoir,the gas injectivity is two times than that of the water;the injected gas can rapidly add the formation energy and enhance the oilfield production.At present,the promising prospects of the daily liquid and oil productions occur in a while for the test block.