Progress and prospects of EOR technology in deep,massive sandstone reservoirs with a strong bottom-water drive

The Triassic massive sandstone reservoir in the Tahe oilfield has a strong bottom-water drive and is characterized by great burial depth,high temperature and salinity,a thin pay zone,and strong heterogeneity.At present,the water-cut is high in each block within the reservoir;some wells are at an ultrahigh water-cut stage.A lack of effective measures to control water-cut rise and stabilize oil production have necessitated the application of enhanced oil recovery(EOR)technology.This paper investigates the development and technological advances for oil reservoirs with strong edge/bottom-water drive globally,and compares their application to reservoirs with characteristics similar to the Tahe oilfield.Among the technological advances,gas injection from the top and along the direction of structural dip has been used to optimize the flow field in a typical bottom-water drive reservoir.Bottom-water coning is restrained by gas injection-assisted water control.In addition,increasing the lateral driving pressure differential improves the plane sweep efficiency which enhances oil recovery in turn.Gas injection technology in combination with technological measures like channeling prevention and blocking,and water plugging and profile control,can achieve better results in reservoir development.Gas flooding tests in the Tahe oilfield are of great significance to identifying which EOR technology is the most effective and has the potential of large-scale application for improving development of deep reservoirs with a strong bottomwater drive.

Remaining Oil Distribution Law and Potential Tapping Strategy of Horizontal Well Pattern in Narrow Oil Rim Reservoir with Gas Cap and Edge Water

For thin oil rim reservoir with gas cap and edge water, it is helpful to improve the development effect to find out the distribution law of remaining oil in this kind of reservoirs. For this reason, taking the narrow oil rim reservoir with gas cap and edge water of Oilfield A in Bohai Sea as a case, the main controlling factors, including reservoir structure, fault, gas cap energy, edge water energy and well pattern, affecting the distribution of residual oil in this kind of reservoir were analyzed by using the data of core, logging, paleogeomorphology and production. Then, the distribution law of remaining oil was summarized. Generally, the remaining oil distribution is mainly potato-shaped or strip-shaped in plane. Vertically, it depends on the energy of gas cap and edge water. For the reservoir with big gas gap and weak edge water, the remaining oil mainly lies in the bottom of oil column. And for the reservoir with small gas gap and strong edge water, the remaining oil mainly locates at the top of oil column. Aiming at different distribution modes of remaining oil, the corresponding potential tapping strategies of horizontal wells are put forward: in the late stage of development, for the reservoir with big gas gap and weak edge water, the remaining oil concentrates at the bottom of the oil column, and the position of horizontal well should be placed at the lower 1/3 to the lower 1/5 of the oil column;for the reservoir with small gas cap and strong edge water, the remaining oil locates at the top of the oil column, and the position of horizontal well should be put at the upper 1/5 to the upper 1/3 of the oil column height, vertically. Based on the study on remaining oil of Oilfield A, a potential tapping strategy of well pattern thickening and vertical position optimization of horizontal well was proposed. This strategy guided the efficient implementation of the comprehensive adjustment plan of the oilfield. Moreover, 18 infill development wells were implemented in Oilfield A, and the average production of the infill wells is 2.1 times that of the surrounding old wells. It is estimated that the ultimate recovery factor of the oilfield will reach 33.9%, which is 2.3% higher than that before infilling wells. This study can be used for reference in the development of similar reservoirs.

中高渗强边水油藏合理采液强度研究

D油田是一边底水发育、处于中含水采油期的中高孔、中高渗透率、强边水油藏。对于此类油藏,开发中主要存在的矛盾是:既要保证油田高速高效开发,又要控制边水过快、过早上升。在实际生产过程中,D油田单井、区块液量与含水相关性很强,这说明该油田存在一个最佳的采液强度。针对上述问题,本文通过对构造位置与含水上升速度的关系、含水上升率与采液强度的关系等研究,确定了D油田合理采液强度,有效控制了单井的含水上升速度,提高了断块的开发效果,并为同类油藏开发提供经验。

强边水小断块油藏聚驱后期开发技术对策研究

针对双河油田强边水小断块油藏聚驱后期递减持续增加的问题,研究了影响聚驱后期开发效果的因素,主要包括:①边水能量强,边部油井见效率低;②聚驱井网不规则,聚窜严重;③地层堵塞油井的产液量降幅大等。为了改善聚驱后期开发效果,进一步提高采收率,开展了强边水小断块油藏的改善开发效果技术对策研究。运用数值模拟技术研究不同注采参数条件下边部井组聚驱驱替效果,界定强边水油藏边部井组合理注采比,拟合小井距聚驱井网不同注采方式对单井点窜流的抑制作用,明确了抑制单井点聚窜的最佳方式,运用油藏工程方法研究不同聚驱阶段油井堵塞半径,提出聚驱后期堵塞油井治理对策,现场应用取得了较好的效果。

双河油田强边水小断块普通稠油油藏聚合物驱开发实践与认识

双河油田核二段油层层数多、单层含油面积小、非均质性严重、边水活跃,属于典型的强边水小断块油藏,综合含水高,开发效果逐年变差,为此,开展小断块油藏聚合物驱边水控制技术、井网调整技术、注采参数优化技术、前缘段塞优化技术以及合理配产配注技术等研究和初步应用,应用结果表明,聚合物驱可有效提高强边水小断块油藏最终采收率。

CDG驱提高边水驱油藏采收率技术研究

受边水活跃的影响,强边水油藏开发后期会因层内非均质性的影响而导致水窜现象的发生,开发效果受到影响。为了进一步提高该类油藏采收率,在大港油田应用CDG驱油技术进行现场试验研究,设计方案实施后井组综合含水降低5.76%,阶段采出程度提高3.74%。

利用油藏动态方法计算强边水小砂体油藏的油水边界

强边水小砂体油藏的油水边界和砂体边界较难刻画,通常是利用地震均方根振幅属性来判断。小砂体油藏存在地质数据少、油水界面判断不准确的缺陷,为了准确判断油水界面,本文利用渗流力学原理和油藏生产动态资料来计算渗流速度,进而反向推算油水运移距离,从而判断油水边界,并与地震均方根振幅属性确定的油水边界进行对比分析。通过实例验证,油藏动态方法计算过程简便,计算结果与传统方法判断的油水边界差距不大。该方法可用来快速判断小砂体油藏的油水边界。

高孔渗强边水小规模砂岩油藏氮气人工气顶驱油矿场试验——以春光油田春22井区为例

春光油田高孔渗、强边水、小规模砂岩油藏采用天然边水驱动开发方式,进入高含水开发后期,在现有井网条件下,顶部剩余油、侧翼剩余油无法有效动用。为此,利用数值模拟技术,开展了氮气人工气顶驱油的油藏适应条件、注采方案设计优化等研究。该技术在春22井区进行了矿场试验,取得了较好的开发效果。对国内外类似高孔渗强边水小规模砂岩油藏高含水开发后期进一步提高采收率具有借鉴意义。

C油田强边水重油油藏开发特征研究

由于在实际生产中,天然能量开发强边水重油油藏表现出不同于普通边水油藏及热采稠油油藏的开发规律。因此,利用油藏工程方法等手段对哥伦比亚C油田的开发特征进行深入分析研究。结果表明,水体能量是影响该类油藏开发特征的主要因素;油田中低含水期含水率上升快,高含水期是主要产油期;受原油重度影响,油井在生产过程中易发生含水率突升、产油量突降;随着含水率上升,油田的采液指数上升,高含水期可通过提液增加油井产量。

GeoSphere地质导向工具在深水气田水平井钻井中的应用

L气田是中国在南海海域首个自主开发的深水气田,其气藏类型为强边底水气藏,受制于地震速度体模型精度及重力流沉积受后期泥质水道改造的影响,气藏构造误差及砂体横向展布存在着很大的不确定性,给水平井钻井轨道带来了“着陆”延后及错层的风险。为此,采用超深边界探测地质导向技术(GeoSphere)来提前预判储层顶面——该技术能探测工具前方20~30 m范围的地层电阻率,通过回传电阻率信息定量多层反演的气藏模型与原模型进行实时互动、匹配判断,在井眼轨迹稳斜井段及时发出稳斜、增斜或降斜指令,确保钻井轨迹处于最优“着陆”点。现场应用的A10H井实钻显示,在井深3670 m(垂深3430.7 m)时,以大套泥岩为主,目的层较钻前地球物理解释构造加深,而GeoSphere探边反演显示在垂深3455.7 m处识别到较连续的高阻抗顶界面,反演电阻率介于7~9Ω·m,决策降低增斜率钻进至反演显示更为连续的高阻层(10~20Ω·m),电测曲线的可对比性逐渐变好,在井深3853.3 m(垂深3460.1 m)进入目的层,探边反演目的层顶界面与实钻基本一致。结论认为,该技术对储层顶界的预测较为准确,可以在地震解释构造不确定性较大的区域辅助水平井钻井着陆或水平段实施。

强边水油藏双高阶段剩余油分布研究与挖潜

C油田开发37 a后,采出程度40%,综合含水率90%,稳产难度极大。为针对性地制定挖潜措施保障油田高效开发,开展了基于C油田地质油藏特征的三维可视化物理模型实验和油藏数值模拟研究,二者相互验证。对剩余油分布规律及影响因素分析研究的结果表明:边水主要沿储层底部推进,经过长时间驱替后,油藏类型由边水油藏逐渐转变为次生底水油藏,生产井井点处水锥严重,在井间及储层顶部剩余油富集;渗透率级差越大、地层倾角越小、原油黏度越高,水锥现象越明显。根据研究成果,在C油田实施了定向井井间水平井加密调整工作,取得较好挖潜效果,研究成果对于类似油田双高阶段剩余油挖潜具有较好的指导作用。

高含水率油藏人工强边水驱技术研究

天然能量开发的边底水油藏能否通过人工强边水驱改善开发效果、进一步提高采收率是需要研究的课题。基于此,本文从人工强边水驱技术入手,分析研究人工强边水驱提高采收率的机理和开发敏感因素,取得的主要认识与成果如下:广泛调研岩心驱替实验、数模、物模等文献,分析研究人工强边水驱提高采收率机理、敏感因素,建立适合人工强边水驱的储层筛选界限。人工强边水驱改善采收率的机理主要体现在三个方面:提高驱油效率、改善波及系数和加速剩余油再聚集。地层倾角越大,人工强边水驱对采收率的改善作用越大。含油条带的宽度越窄,采收率曲线上升速度越快;剩余油饱和度越高,人工强边水驱的最终采收率也越高。本文探索了适合特高含水率边底水油藏强化水驱技术,对于提高特高含水率边底水油藏的采收率,改善开发效果作用明显,此举可为同类型高含水率油藏提高采收率提供新的技术思路和指导。

气顶强边水油藏气顶区剩余油分布与挖潜——以渤海埕北油田为例

埕北油田为气顶强边水油藏,油田经过30多年开发后气顶区域内经历了长期的气窜、水进、油侵等复杂驱替,剩余油分布复杂,挖潜难度大。基于埕北油田地质油藏特征与开发生产特征,设计并开展物理模拟实验,同时进行了相应的油藏数值模拟机理模型研究与扩展分析,研究油气互侵机理及剩余油分布规律。研究结果表明,油气互侵规律主要表现为两方面:一是能量水平强弱,当地层能量较弱时(衰竭开发)以气侵为主,当地层能量较强时(强边水或人工注水)以油侵气顶为主;二是生产井的位置影响,对于气顶强边水油藏,在靠近气顶区有生产井存在的条件下,油井快速气窜,在强边水推动作用下气顶萎缩、油侵气顶,边水主要沿储层底部向构造高部位推进,剩余油主要分布在油侵气顶区和储层顶部。根据研究认识,在埕北油田原始气顶区实施水平井加密调整,挖潜原始气顶区剩余油,取得了较好效果。

海相砂岩油藏张型广适水驱曲线预测修正应用

XJ油田为强边底水砂岩油藏,边底水能量充足,属于高孔高渗储层,采出程度高,预测精度误差大。针对海相强边底水砂岩油藏目前水驱曲线预测存在的问题,以生产动态资料分析油藏驱替特征出发,研究油井水淹类型影响因素,并从地质因素和驱替特征说明水驱曲线的适应性。在前人对于水驱曲线预测方法研究的基础上,结合强边底水油藏的驱替特征以及生产特点,重点研究水驱特征曲线的适应性与驱替特征的关系、修正目前水驱特征曲线以适应预测极限采收率,并编制相应的计算模块,从水淹规律、适用性分析、水驱曲线修正三个方面总结强边底水砂岩油藏水驱曲线预测极限采收率的油藏工程方法。