吉木萨尔页岩油注入介质梯级提采实验评价

Experimental evaluation on EOR medium grading of shale in Jimusaer Oilfield

为了评价水、表活剂溶液和CO_(2)与储层的相互作用对页岩油采收率的影响,分析压差和渗吸作用对吉木萨尔页岩油的提采效果,并研究渗吸介质作用顺序对采收率的影响,对井底岩心饱和储层原油,开展离心实验,重水渗吸、表活剂溶液渗吸以及CO_(2)吞吐实验,结合核磁共振技术表征岩心孔隙中的原油量,并计算采收率。实验结果表明,渗吸作用是页岩油产出的主要动力,重水渗吸驱油采收率在30%~34%之间,表活剂溶液渗吸采收率在35%~40%之间,CO_(2)吞吐采收率在37%~50%之间,压差驱动对吉木萨尔页岩油的采出影响较弱,离心采收率在3%以下;实验中的3种介质提采能力,由低到高为重水、表活剂溶液和CO_(2);按照驱油采收率高低对提采介质分级(称为梯级),介质与储层接触顺序显著影响着最终采收率,将最高梯级介质首先注入储层,使得最高提采梯级介质与储层首先接触,有利于提高页岩油井的最终采收率。在油田生产中,建议在新井压裂中,首先在压裂前置液使用最高提采梯级的介质,使得最高提采梯级的介质可以首先与储层接触,以保证最终采收率最高,而不是逐级提采;在老井中,应当使用比已入井流体更高梯级的提采介质,通过渗吸作用可以继续产出原油。

To evaluate the influence of the interaction between water,surfactant solution and CO_(2) and reservoir on shale oil recovery factor,analyze the EOR effect of pressure difference and imbibition on shale oil in Jimusaer Oilfield,and study the influence of the action sequence of imbibition media on the recovery factor,centrifugal experiment was performed on the bottom hole cores saturated with reservoir oil,and then heavy water imbibition,surfactant solution imbibition and CO_(2) huff-n-puff experiments were carried out.In addition,the oil volume in the pores of the cores was characterized by means of NMR technology,and the recovery factor was calculated.It is experimentally indicated that imbibition is the main driving force of shale oil production,and the recovery factor by heavy water imbibition,surfactant solution imbibition and CO_(2) huff-n-puff are 30%-34%,35%-40%,and 37%-50%,respectively.Pressure difference drive has less influence on shale oil production in Jimusaer,and the recovery factor by centrifugal is less than 3%.Based on the EOR capability in the experiment,three kinds of media are ranked from low to high as heavy water,surfactant solution and CO_2.The EOR media are graded based on oil recovery factor(called as grading).The contact sequence of medium with reservoir has great influence on ultimate recovery factor.The medium of the highest grading shall be firstly injected into the reservoir to contact it firstly,which is favorable for improving the ultimate recovery factor of shale oil well.As for new well fracturing in oilfield production,it is suggested to firstly use the medium of the highest EOR grading before prepad fluid instead of successive EOR,so as to ensure the contact of the medium of the highest EOR grading with the reservoir firstly and maximize the ultimate recovery factor.As for old wells,it is suggested to use the EOR medium whose grading is higher than that of the fluid in the well,so as to continue to produce oil by virtue of imbibition.