改变低渗透油藏润湿性提高采收率技术研究进展

油藏岩石润湿性是储层物性的一个基本特征参数,是影响油田特别是混合润湿或油湿性低渗透油田开发的重要因素.文中针对目前通过改变油藏岩石润湿性以提高原油采收率方面的相关技术及研究进行了详细调研,系统总结了改变油湿性油藏岩石润湿性以提高原油采收率的方法.经过归纳总结,认为目前这些方法主要分为物理法、化学法和微生物法3大类.润湿...     

注蒸汽或热水诱导润湿性反转提高油藏采收率

油藏岩石的润湿性与岩石矿物成分及所接触的流体性质有关。在原油聚集成藏的初期 ,石油侵入孔隙时 ,孔隙周围的固体表面吸附着一层水膜。石油的侵入破坏了这一平衡 ,水膜破裂 ,原油与孔隙壁直接接触 ,原油中的表面活性成份沉积在固体表面 ,岩石开始变得亲油。在原油开采中 ,注入表面活性剂使岩石亲水是提高采收率的方法之一 ,但成本太高限制了其应用。本文讨论的是注入蒸汽或热水 ,提高储层温度 ,岩石在热力作用下发生润湿性反转 ,变亲油为亲水 ,从而提高原油产量和采收率。首先从水流过基质驱替原油的作用力机制入手进行分析。1 毛管力和重…     

硫酸盐浓度对水驱提高采收率的影响

水驱提高采收率对注入水的离子组成有一定的要求,为了验证润湿性改变不是硫酸盐水驱提高原油采收率的唯一因素,在岩心润湿性为水湿的条件下进行水驱,研究了硫酸盐浓度、温度、注入速率和原油类型对硫酸盐水驱采收率的影响.结果表明,在水驱过程中,原油采收率随着硫酸盐浓度的增加而增加.在40℃下水驱提高采收率无明显增幅,随着温度的升高...     

碳酸盐岩油藏低矿化度水驱作用机理实验

碳酸盐岩油藏低矿化度水驱应用潜力巨大,为了更好地推广其矿场应用而针对性开展作用机理的实验研究。首先,岩心驱替实验研究注入水矿化度和关键离子组成对采收率的影响;而后,润湿角测定实验分析注入水矿化度和关键离子组成对碳酸盐岩表面润湿性的影响;最终,根据实验结果建立碳酸盐岩油藏低矿化度水驱作用机理。研究发现：低矿化度水驱能有效改变碳酸盐岩表面润湿性进而提高油藏采收率,存在最优矿化度使得碳酸盐岩表面润湿性变化最大、采收率最高;Mg²⁺和SO₄^2-对碳酸盐岩表面润湿性和原油采收率的影响效果不同;随着溶液中Mg²⁺浓度升高,碳酸盐岩表面润湿性变化不断增强、原油采收率不断升高;随着溶液中SO₄^2-浓度增加,碳酸盐岩表面润湿性变化先增强后减弱、原油采收率先增加后稳定。碳酸盐岩油藏低矿化度水驱作用机理在于润湿性的改变：①SO₄^2-吸附在正电性的碳酸盐岩矿物表面,中和表面电荷,促进了Mg²⁺向矿物表面运动;②Mg²⁺与碳酸盐岩矿物表面的Ca²⁺发生取代反应,造成原油组分的解离。     

油藏润滑性及其测定方法

油藏湿性研究是提高原油采收率技术的重要理论基础,本文综述了原藏润湿性的实验测定方法,并讨论了这些方法的特点,包括三方面的内容,润湿性定量测定法,润湿性定性测定法和润湿性现场测定法。     

润湿性的改变对提高原油采收率的影响研究

注水开发几乎不能从低渗油湿性油藏中采出原油,如果油藏岩石的润湿性得到改变,通过自然的渗吸其采收率就能得到改进。因此,了解润湿性改变的影响因素及其机理对提高原油采收率意义重大。岩心流动试验表明:水驱时中性润湿岩心的采收率最高,强水湿岩心其次,强油湿岩心最低。润湿性由亲油向亲水方向的变化,油水相渗曲线右移,残余油饱和度下降了25%,油水共渗区范围明显增大,采出程度提高。目前认为加入表活剂改变油藏岩石的润湿性是提高原油采收率比较可行的方法。     

应用环境扫描电镜研究储集层砂岩样品润湿性的变化特征

润湿性是控制储集层流体分布和注水开发动态的重要参数之一,因而在实验室研究开发了许多测定润湿性的方法^[1]。对于油湿地层,若在注水过程中加入某种试剂,使亲油地层变为中性润湿或弱亲水地层,则可以大大提高油藏的采收率^[2]。分子沉积膜（MD膜）驱是一项新型的三次采油方法,MD膜剂在固体表面吸附后,固体表面的性质发生改变,使得原油剥离下来,从而达到提高原油采收率的目的。为了研究提高原油采收率的MD膜驱替微观机理,笔者用环境扫描电镜对辽河油田的较强亲油的未洗油砂、洗油后的强亲水油砂和经MD膜剂溶液（用模拟地层水配置,膜剂浓度为500mg/L）浸泡过的未洗油油砂（浸泡时间为7天,样品变为较弱亲油）等3种样品进行了试验研究。国际上有较多的文献^[3-5]报道了利用环境扫描电镜研究储集层岩石与流体相互作用及储集层润湿性特征的工作,但尚未见样品经MD膜剂处理后润湿性变化特征的报道。     

低矿化度注水提高砂岩储集层采收率的微观机理

低矿化度注水是一项前沿技术,因在碳酸盐岩和砂岩储集层中能提高驱油效果,目前受到广泛关注。本文梳理了砂岩储层低矿化度注水提高采收率的主要微观机理,即润湿性的改变、黏土的膨胀与运移、双电层的扩散等。低矿化度水的质量浓度、离子类型能改变多种黏土内部力平衡及黏土与原油之间的力平衡,造成双电层扩散,最终使黏土出现润湿性的改变以及膨胀运移的现象。低矿化度注水能提高大部分砂岩油藏的采收率。国内大部分砂岩油藏开发已进入中后期,进行低矿化度注水的微观机理研究对砂岩油藏开发有极大的指导意义。     

油藏岩石润湿性对采收率的影响

本文综述了油藏岩石润湿性对水驱油采收率影响的两种不同观点：一种认为弱水湿油藏水驱油采收率最高，另一种认为，弱水湿油藏水驱油采收率最高。本文所做理论分析表明，弱水湿油藏水驱油采收率最高较有依据。     

油藏岩石润湿反转与储层损害

本文综述了关于钻井液等外来液体引起油藏岩石润湿性改变及其机理研究方面的成果和进展;分析了钻井液及其处理剂、无机离子、pH 值以及温度、压力影响油藏岩石润湿性的原因;着重从润湿性与油、水相对渗透率和采收率的关系论述了钻井液引起的润湿反转对储层的损害,并总结了防止和克服这种损害的途径和措施。     

Comparison of in-situ and ex-situ microbial enhanced oil recovery by strain Pseudomonas aeruginosa WJ-1 in laboratory sand-pack columns

Microbial enhanced oil recovery (MEOR) applies biotechnology to improve residual crude oil production from substratum reservoir. MEOR includes in-situ MEOR and ex-situ MEOR. The former utilizes microbial growth and metabolism in the reservoir, and the latter directly injects desired active products produced by microbes on the surface. Taking biosurfactant-producing strain Pseudomonas aeruginosa WJ-1 for research objects, in-situ enhanced oil recovery and ex-situ enhanced oil recovery by biosurfactant-producing strain WJ-1 were comparatively investigated in sand-pack columns.The results showed that P.aeruginosa WJ-1 really proliferated in sand-pack columns, produced 2.66 g/L of biosurfactant, altered wettability, reduced oil-water interfacial tension (IFT) and emulsified crude oil under simulated in-situ process. Results also showed that higher biosurfactant concentration, lower IFT, smaller average diameters of emulsified crude oil were obtained in in-situ enhanced oil recovery experiment than those in ex-situ enhance oil recovery experiment. Similar wettability alteration was observed in both in-situ and ex-situ enhanced oil recovery experiment. The flooding experiments in sand-pack columns revealed that the recovery of in-situ was 7.46%/7.32% OOIP (original oil in place), and the recovery of the ex-situ was 4.64%/4.49% OOIP. Therefore, in-situ approach showed greater potential in enhancing oil recovery in contrast with ex-situ approach. It is recommended that the stimulation of indigenous microorganisms rather than injection of microbial produced active products should be applied when MEOR technologies were employed.     

The Role of Wettability in Petroleum Recovery

Various findings on core handling effects and crude oil/brine/rock (COBR) interactions have indicated how the wettability of a core sample is altered when retrieved from a reservoir. Moreover, it is revealed that wettability of a core will affect almost all types of physical parameters necessary for reservoir management, such as capillary pressure. However, the most accurate results are obtained when native or restored-state cores are used with native crude oil and brine at reservoir temperature and pressure. Such conditions provide core that have the same wettability as the reservoir. Equally, the wettability of originally water-wet rock can be altered by the adsorption of polar compounds and/or the deposition of organic material that was originally in the crude oil. The degree of alteration is determined by the interaction of the oil constituents, the mineral surface, and the brine chemistry. Factors that influence wettability alteration are considered, and how this in turn affects the capillary pressure, is determined. Due to the capillary pressure dependence on water saturation, the effect of wettability alteration on reserve estimation through the initial water saturation is shown. The implications for oil recovery prediction and reservoir management are discussed. The main objective is to do a critical analysis on how wettability alteration dictates the success or failure of reservoir management irrespective of the technical or operational input, early in the life of a reservoir. It is believed that reserve estimation at the early stage is either optimistic or pessimistic with the consequent effect on oil recovery prediction and reservoir planning. The overall effect would be poor reservoir management at the early life of the reservoir, which effects on the later life of the reservoir is inestimable. This explains why the petroleum business is the riskiest business in the world. This would continue to be so unless a method is devised to measure reservoir parameters in situ, devoid of wettability alteration to any extent.     

Variations in wetting behavior of mixed-wet cores resulting from probe oil solvency and exposure to synthetic oil-based mud emulsifiers

Mixed wettability (MXW) results from adsorption from crude oil on rock surface which is not overlain by bulk water. Crude oil/brine/rock interactions and their effect on oil recovery are often investigated after replacing the crude oil with a mineral oil. If crude oil is displaced directly by mineral oil, extreme wettability alteration, referred to as MXW-DF (direct flood), is observed. Less change is observed if an intermediate solvent, such as decalin, is used to avoid destabilization of asphaltenes contained in the crude oil; wettability conditions attained by this treatment are referred to as MXW-F (film). The oil used in a displacement test is referred to as the probe oil, the most common choice being either crude oil or mineral oil. There is strong practical interest in developing MXW-F cores that have wetting properties that are comparable to wettability at reservoir conditions. The main objective of this work is to compare the effect of probe oil solvency, characterized by refractive index, on wetting behavior, characterized by spontaneous imbibition, with MXW wettability given by the parent crude oil. The tested probe oils included mineral oils, alkanes, decalin, toluene, alpha-methylnaphthalene (AMN), crude oils and modified crude oils with both increased and reduced solvency, and base oils and solutions of emulsifiers used in synthetic oil-based mud (SBM) formulations. Wettability established by direct displacement of crude oil with an alkane (MXW-DF) showed systematic increase in water wetness with increase in solvency of the probe oil. Other approaches to tuning MXW-F wettability states by choice of probe oil are also presented. Base oils used in the formulation of SBM had essentially no effect on the imbibition behavior of MXW-F, whereas exposure of MXW-F cores to two kinds of emulsifier resulted in persistently suppressed imbibition for a wide range of probe oils.     

CO2驱油过程中孔喉结构对储层岩石物性变化的影响

注CO2提高储层原油采收率过程中,储层中流体的渗流和分布受岩石孔喉结构控制,且注入的CO2会引发原油中的沥青质沉淀,导致储层渗透率下降并改变储层的润湿性.通过在4块渗透率相似但孔喉结构不同的岩心上进行的混相和非混相的CO2驱油实验研究了 CO2驱油过程中岩石孔喉结构对储层岩石物性变化的影响.基于岩石孔径分布和压汞曲线,...     

X油藏注气混相驱可行性实验研究

针对X底水油藏油井注水后综合含水上升过快的问题,利用HB70/300型高压物性分析仪开展了该区块原油相态特征实验、注气相态特征实验,并运用细管法开展了注CO₂最小混相压力实验。对比分析了CO₂和N₂两种性质气体注入前后原油的相态特征变化,确定了该区块原油注CO₂最小混相压力,为X油藏注气提高采收率可行性提出依据。实验结果表明,X油藏原始地层压力为46.01 MPa,原油饱和压力为11.06 MPa,注N₂后饱和压力上升迅速,在原始地层条件下难以实现混相,表现出典型的非混相特征;注CO₂后饱和压力上升较平缓,细管法测得的最小混相压力为28.03 MPa,说明利用CO₂可实现CO₂的混相驱替,而且最终的驱替效果比较理想。说明该油藏可开展注CO₂混相驱,为进一步的开发方案调整提供了依据和合理的建议。      

表面活性剂对特低渗油藏渗吸驱油的影响

为了促进延长油田化学渗吸驱油提高采收率的目的,以延长HZP区块长6油藏为研究对象,针对水驱波及范围小,水驱动用程度低的问题,运用室内实验测试及分析的方法,分析不同润湿性和界面张力渗吸体系的渗吸驱油效率和规律。结果表明,润湿性不同的岩心渗吸驱油速度和效率由强到弱依次为亲水性、中性、亲油性,注入水体系中,原油在亲水岩心中的粘附功最小,仅有2.464 5×10^-3 J/m²,在亲油岩心中的粘附功达到16.743 7×10^-3 J/m²,是亲水岩心的6.8倍,不同表面活性剂均可以使粘附功不同程度的降低。十六烷基磺酸钠溶液渗吸效率最高,亲水岩心中渗吸效率达到25.2%,中性润湿岩心中渗吸效率为20%,均高于注入水渗吸驱油效率。矿场应用后油井综合含水下降20个百分点。对低渗油藏化学渗吸提高采收率具有重要意义。     

油气储层中的水膜

本文对油藏工程中有关油气储层中的水膜问题进行了评述,介绍了近代水膜理论及其在油气藏工程中的应用。     

化学驱后水淹层地质特征及测井响应分析

大庆长垣喇萨杏油田经多年开发,已进入水驱、聚驱、三元复合驱并存阶段。注入溶液改变了储层的物理性质,地层水矿化度、含油饱和度、孔隙结构以及岩石润湿性等都会发生变化,不同的驱替方式导致了不同的储层地质特征。油层水淹后,电阻率、自然电位、微电极幅度差等测井响应的变化规律也不同。本文利用大庆油田丰富的密闭取芯检查井资料,系统的研究了化学驱后水淹层地质特征及测井响应特征分析,对提高水淹层测井解释的精度奠定了基础。