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.

薄层砂岩边底水油藏空气辅助内源微生物驱油技术

针对边底水油藏“双高阶段”零散分布剩余油如何有效动用、低成本高效微生物驱油体系如何研发、微生物驱效果评价及配套技术攻关等难题,建立微生物驱筛选图版并评价了油藏微生物驱的适应性;利用微生物分子生态学技术全面解析了油藏微生物群落结构,筛选了乳化效果好的采油功能菌株H3;通过对主要营养成分碳源、氮源、磷源的筛选,开展单因素实验和正交实验,确定了可实现原油乳化分散和抑制硫酸盐还原菌生长的复合粉激活体系;研究了底水油层“船底形”剩余油富集特征,形成了“微生物乳化+空气提效+稠化剂封堵”提高采收率驱油模式,明确了提高采收率幅度与注入菌体浓度、注入孔隙体积倍数正相关。将研究成果应用于准噶尔盆地陆梁油田薄层砂岩边底水油藏,实施“4注20采”微生物驱提高采收率矿场先导试验,注入微生物激活剂0.13倍孔隙体积,2017至2023年阶段增油5.6×104 t,采收率提高4.0个百分点,增油效果好的井主要分布在总菌浓度高、石油地质储量大、构造高部位、油层厚度大、底水薄、采出程度较高的区域。研究成果对丰富微生物驱提高采收率技术序列具有借鉴作用。

单2块稠油油藏高含水后期提高采收率对策

针对单家寺稠油油藏主力油层水淹严重 ,开发效果变差的实际 ,在重新建立地层、构造、储层及流体模型的基础上 ,描述出动态油水界面及剩余油富集区 ,探索出稠油油藏高轮次吞吐高含水后期的挖潜对策 ,并通过上、下扩射 ,注氮气调剖等技术 ,提高老油田注汽质量和强化注汽效果 。

活跃边水气藏水侵系数与稳产期关系研究

目前对活跃边水气藏稳产期末的采出程度预测没有特别有效的手段,经常出现产量在没有任何征兆的情况下发生快速递减。以雅克拉水驱气藏储层长岩心物理模型为基础,通过水驱气实验模拟水侵过程气水两相渗流特征;以水驱物质平衡方程为理论方法,引入水侵系数概念描述气藏水侵特征。由于注入水的含烃孔隙体积与水侵系数概念一致,通过水驱实验模拟活跃边水气藏水侵对气藏的影响是可行的。实验结果表明,当注入水达到0.3~0.45倍HPV(含烃孔隙体积)时,水驱前缘突破,天然气产能从稳产期进入快速递减期。生产历史表明,中下气层水侵系数达到0.33~0.36时,天然气产能快速递减,实验和生产实际基本吻合。通过对上气层开展水侵系数计算,2019年8月至2020年2月水侵系数达到0.33~0.36时,进入稳产末期,和数值模拟结果基本一致,需及时对高风险井进行调整。

海上油田特高含水期油井大幅提液研究

渤海C油田为典型的海上强边底水油藏,开发方式为单砂体水平井天然水驱开发,具有水体能量充足、含水上升极快的特点。针对油田这一特征,通过开展大幅提液增油可行性研究,分析了特高含水期油井提液机理,充分论证了油井地下产液能力,与现场井筒、地面实际情况相结合确定油井提液幅度。在此基础上,选择C油田A33井进行特高含水期油井大幅提液试验,在渤海油田范围内首次成功下入3000 m^(3)·d^(-1)超大排量电泵,取得了良好的提液增油效果,对同类型油井大幅提液增油工作具有较好的借鉴意义。