大庆外围油田注空气提高采收率机理研究

中文标题

大庆外围油田注空气提高采收率机理研究  英文标题

Study on Air Injecton EOR Mechanism for Daqing Peripheral oil field

作者

刘勇

专业与研究方向

油气田开发工程 注气提高采收率

指导教师

孙良田；孙雷

申请学位等级

博士

机构

西南石油大学

论文完成年度

2008

中图分类号

TE357.7;O643

中文关键词

高压注空气；低温氧化反应；相态；最低混相压力；反应动力学；提高采收率

英文关键词

high pressure air injection; low-temperature oxidation; phase behavior; minimum miscibility pressure; reaction kinetics; enhanced oil recovery

中文摘要

将空气注入到轻质油藏，提高原油采收率，是注气提高原油采收率开发技术新的应用领域。国外油田矿场试验表明轻质油藏高压注空气能够取得较好的开发效果。轻质油藏高压注空气工艺能够应用于注水开发效果差的低渗及特低渗油藏，也能用于水淹油藏的开发。注空气技术的研究和应用在我国起步较晚，对相关领域的研究还比较少。开展高压注空气驱油技术的研究，将有助于丰富适合我国油田的提高采收率技术。

在综合调研国内外文献的基础上，运用加拿大DBR公司JEFRI无汞油气藏流体PVT分析系统以大庆外围某低渗透油藏地层流体为研究目标，开展地层原油相态特征实验，注空气、N2过程地层原油膨胀实验、多次接触实验等相态特征综合研究；进行了注空气、N2和烟道气三种气体细管实验，考察了温度对细管实验累计驱油效率的影响；通过在RUSKA2370-601PVT筒中进行的脱气原油与空气恒温恒压氧化反应实验数据，获取轻质油藏注空气低温氧化反应动力学参数，研究了低温氧化反应对原油物性的影响。通过以上研究得到如下结论：

（1）该油藏在开发过程中仍处于单相状态，溶解气尚未脱出。其地层原油膨胀能力较低。注入空气、N2后，注入气难溶于原油中，饱和压力迅速升高；注入等摩尔量的空气、N2后，注入空气后的地层原油饱和压力要稍低于注N2后的地层原油饱和压力。地层原油注空气、N2向前接触中，随接触次数的增加，气相相对体积先快速下降再趋稳定，地层原油气油比逐级增加，但增幅逐级减小，地层原油密度稍有降低。地层原油注空气、N2向后接触实验中，随接触次数的增加原油的相对体积先增加再减小，后趋稳定，地层原油气油比先增加再逐渐减小，地层原油密度呈现先降后增最后趋于稳定的变化趋势。

（2）在地层温度和相同注入压力下，1.2PV时细管实验的累积驱油效率由高到低依次是：烟道气驱、氮气驱、空气驱。三种注入气均难以与此地层原油混相。空气作为注入气时，由采出流体气相组成可以发现，仅有微量的CO和CO2气体生成。注空气、烟道气的驱油效率随着温度的升高而上升，但空气的升幅较大。数值模拟结果表明，当温度到达300℃时，烟道气驱细管实验累计驱油效率高于50%。

（3）由氧化反应动力学实验获得了该原油的低温氧化反应速度常数、阿仑尼乌斯活化能、指前因子和反应级数。

（4）在地层温度条件下，注入油藏的空气中的氧气能与原油发生低温氧化反应，少部分氧原子与碳原子结合生产一氧化碳和二氧化碳，大部分以杂原子的形式进入原油组分的分子中；氧化反应导致脱气原油表观粘度上升，反应后脱气原油的密度稍有降低。

由此可见：注空气不是普通的注气提高采收率技术，高温氧化前缘的形成与否对采收率的提高具有重要的影响。

英文摘要

High pressure air injection is a new method of gas injection enhanced oil recovery for light oil. Some foreign field experiments show great promise for improved oil recovery. High pressure air injection for light oil reservoirs can applied to both low permeability oil reservoir and flooded oil reservoirs. Research and application of this technology is later in china. Development of high pressure air injection will enrich enhanced oil recovery technologies in china.

Based on an in-depth literature review, Daqing periphery low permeability reservoir formation fluid was studied using JEFRI mercury-free reservoir fluid PVT analysis system made by Canadian DBR company. The phase behavio study includes the phase behavior of formation fluid, and swelling experiment and multiple contact experiment for air and nitrogen injection. Slim tube test of nitrogen, air and flue gas injection were done, and the effect of temperature on slime tube test displacement efficiency was study. Formation fluid low-temperature oxidation kinetics parameters were acquired by using RUSKA2370-601 mercury-free reservoir fluid PVT analysis system, and the effect of LTO on crude physical property was studied. The results of this paper as follows:

(1) Resident fluid of the oil reservoir is single phase behavior yet, and dissolved gas can’t escape. Its swelling capacity is low. When air or nitrogen is injected into oil reservoir, saturation pressure of resident fluid quickly ascend. When equal molal weight injectant is injected, in place oil saturation pressure injected air is a little lower than of nitrogen. For air or nitrogen forward multiple contact experiment, with contact order increament, gas bulk volume fraction quickly decreases first, then steadies; GOR of in place oil increases; and oil density a little descent. For air or nitrogen backward multiple contact experiment, with contact order increament, oil bulk volume fraction quickly increases first, then decreases, last steadies; GOR of in place oil increases first, then decreases; and oil density first decreases, then increases, last steadies.

(2) At reservoir temperature and equal injection pressure, the order of 1.2PV displacement efficiency is flue gas, nitrogen and air. It is difficult that these inject gas with in place oil achieves miscible phase. When air is injected into slim tube, a little CO and CO2 yield. With the increase of reservoir temperature, displacement efficient increase of flue gas injection is more than of air injection. Numerical simulation result is that it can more than 50% at 300℃.

(3) Reaction rate constant, Arrhenius activity energy and reaction order of low temperature oxidation were acquired through oxidation experimentm of oxygen and dead oil.

(4) At reservoir temperature, oxygen can react with formation oil. A little oxygen atom and carbon generates carbon monoxide and carbon dioxide, most part oxygen atom become as heteroatom of oil components. Low temperature oxidation induced apparent viscosity increase and density decrease of dead crude.

This shows, high pressure air injection isn’t an ordinary gas injection enhance oil recovery, and the thermal front has important affect on recovery for light oil reservoirs.