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。     

深水疏松砂岩储层微粒运移损害的控制方法

中国南海深水疏松砂岩油气层钻完井作业中，易发生微粒运移、堵塞，造成储层损害，需要探索微粒运移损害的控制方法。选用南海深水疏松砂岩储层岩样，通过微粒吸附和释放实验以及岩心动态损害评价实验，探讨了纳米材料控制微粒运移损害的作用效果；实验分析了纳米颗粒吸附对岩石表面形貌、粗糙度及电性的影响；利用微粒与吸附纳米颗粒的岩石孔壁之间的相互作用能计算模型，分析了不同离子强度下储层微粒与岩石孔壁之间的总相互作用势能及作用机制。结果表明，纳米颗粒能有效控制深水储层微粒的运移，将其吸附并固定在孔壁表面。随着流体离子强度增加，控制运移的作用效果增强。其中，纳米氧化铝NP-1的作用效果最好，可明显提高深水储层岩心的渗透率恢复值，并且与深水钻井完井液具有良好的配伍性。模型计算结果表明，吸附纳米颗粒后，岩石孔壁与储层微粒之间的总相互作用势能下降，有利于岩石孔壁吸附、固定微粒，原因是纳米颗粒的吸附增加了岩石表面粗糙度及黏附力矩，也影响了表面电荷分布，有利于降低排斥势垒，并使初级势阱加深，提高岩石表面固定微粒的能力。因此，深水钻完井中，可通过加入纳米颗粒、适当提高工作液矿化度来减少微粒运移引起的储层损害。     

Adsorption of natural surfactants on sandstone rocks: Effect on the quality of the recovered asphaltenic oil

Natural surfactants are important for any enhancing oil recovery applications since these kinds of surfactants have less detrimental effects and also lower cost in comparison to the industrial surfactants. Adsorption of surfactants on sandstone minerals is an important issue which needs to be considered before applying any surfactant-based enhanced oil recovery technique. In this study, a new model based on adaptive neuro-fuzzy interference system was developed in order to simulate the kinetic behavior of natural surfactants adsorption on sandstone minerals with high accuracy. Performance of the model was investigated by comparing the results of the proposed model with the results of previous well-known kinetic models. Results demonstrated that this model has the highest accuracy compared to the other well-established models found in literature. Finally, in order to show the importance of modeling surfactants adsorption, the effect of a natural surfactant on the quality of the produced oil was investigated by performing SARA analysis on the recovered oil at various conditions of surfactant adsorption. It is shown that in the case of lower surfactant adsorption on sandstone minerals, the produced oil has higher asphaltene fractions.     

Thermal Resistance and Application of Nanoclay on Polymer Flooding in Heavy Oil Recovery

High molecular weight and water-soluble synthetic organic polymers are currently being used in the field with the hope of enhancing the recovery of oil by water flooding. Nanotechnology has been used in many applications and new possibilities are discovered constantly. Recently, a renewed interest arises in the application of nanotechnology for the upstream petroleum industry. The author focuses on roles of clay nanoparticles on polymer viscosity. Polymer-flooding schemes for recovering residual oil have been in general less than satisfactory due to loss of chemical components by adsorption on reservoir rocks, precipitation, and resultant changes in rheological properties. Rheological properties changes are mainly determined by the chemical structure and mix of the polymers, surface properties of the rock, composition of the oil and reservoir fluids, nature of the added polymers, and solution conditions such as salinity and temperature. On the other hand, the author's focus is on viscosity, temperature, and salinity of solutions polyacrylamide polymer solutions with different nanoparticles. Results show that ultimate oil recovery by nanoclay polymer flooding enhances by a factor of 5.8% in comparison to polymer flooding high salinity and temperature.     

原油组分、孔隙结构对自吸的影响

自吸是裂缝性油藏采油的一个特别重要的现象。自吸过程取决于许多复杂的因素相互作用。主要研究了原油组成,孔隙结构对自吸的影响。研究中使用的多孔介质有两种类型：分别为砂岩和石灰岩。研究结果表明,原油组分、孔隙结构对自吸速度及最终采收率有较强影响。对砂岩体系,在不同束缚水饱和度条件下,自吸最终采收率变化不大,而对石灰岩体系,最终采收率与束缚水饱和度有限大关系。原油组分对自吸的影响表现为润湿性改变而产生的毛管力变化。     

低渗透砂岩油藏注入阴阳离子聚合物深部调剖技术研究

针对具有窜流大孔道的低渗透砂岩油藏条件,对交替注入阴、阳离子聚合物的深部调剖技术进行了研究。通过室内试验评价了各种因素对聚合物吸附量的影响。结果表明,随着温度的升高,聚合物吸附量减小,且地层对阳离子聚合物比对阴离子聚合物更容易吸附。随着矿化度、吸附时间、聚合物浓度的增加,聚合物吸附量也增加。阳离子聚合物的吸附平衡浓度为1 500mg/L,吸附平衡时间为8h;阴离子聚合物的吸附平衡浓度为1 000mg/L,吸附平衡时间为6h。物理模拟试验表明,采用阴阳离子聚合物交替注入方式比注入单一聚合物有更好的封堵效果,并且先注入阳离子聚合物效果好于先注入阴离子聚合物的效果。随着注入轮次的增加,封堵性能提高。但是,综合考虑经济成本,不要超过3个轮次。交替注入阴阳离子聚合物可以大大提高采收率,水驱采收率增值为41%。     

Experimental investigation of the effect of dispersed silica and alumina nanoparticles on oil-aqueous phase interfacial tension

This work experimentally investigated silicon oxide and aluminum (III) oxide nanoparticles as enhanced oil recovery agents and their effects on wettability and interfacial tension of oil-wetted sandstone and carbonate rocks. The two nanoparticles were selected based on a screening of commercially available nanoparticles with considering the most important parameters. The required time and treatments for the rock samples to become oil-wet, and the required time for the nanofluid to treat each rock sample were also experimentally investigated. Results of this study show that the nanoparticles alter wettability of sandstone and carbonate rocks from oil-wet to water-wet state. It is also observed that sandstone samples are more effected than limestone ones and alumina nanoparticles have greater potential to alter the rock wettability.     

离子组成及矿化度对低矿化度水驱采收率的影响

低矿化度水驱提高采收率对注入水和地层水的离子组成有一定的要求。在室内砂岩岩心驱替实验的基础上,采用对比的方法,研究了注入水和地层水的离子组成对低矿化度水驱提高采收率的影响。结果表明：在进行三次采油模式下的低矿化度水驱时,地层水中含有二价阳离子Ca²⁺或Mg²⁺均可提高采收率,且Ca²⁺的效果要好于Mg²⁺;只有注入水的矿化度低于油藏油水系统低矿化度效应启动阈值时,采收率才会提高。分析实验结果确定,地层水中含有二价阳离子Ca²⁺或Mg²⁺,以及注入水的矿化度低于由油藏油水系统决定的矿化度阈值,是实现低矿化度水驱提高采收率的必要条件。     

Silica nanofluid flooding for enhanced oil recovery in sandstone rocks

Enhanced oil recovery is proposed as a solution for declining oil production. One of the advanced trends in the petroleum industry is the application of nanotechnology for enhanced oil recovery. Silica nanoparticles (SiNPs) are believed to have the ability to improve oil production, while being environmentally friendly and of natural composition to sandstone oil reservoirs.In our work, we investigated the effect of silica nanoparticles flooding on the amount of oil recovered. Experiments were carried using commercial silica of approximately 20 nm in size. We used sandstone cores in the core flooding experiments. For one of the cores tertiary recovery is applied where brine imbibition was followed by nanofluid imbibition. While in the other cores secondary recovery was applied where primary drainage is directly followed by nanofluid imbibition. We investigated the effect of concentration of nanofluid on recovery; in addition, residual oil saturation was obtained to get the displacement efficiency. Silica nanofluid of concentration 0.01 wt%, 0.05 wt%, 0.1 wt% and 0.5 wt% were studied.The recovery factor improved with increasing the silica nanofluid concentration until optimum concentration was reached. The maximum oil recovery was achieved at optimum silica nanoparticles concentration of 0.1 wt%. The ultimate recovery of initial oil in place increased by 13.28% when using tertiary flooding of silica nanofluid compared to the recovery achieved by water flooding alone. Based on our experimental study, permeability impairment was investigated by studying the silica nanoparticles concentration, and the silica nanofluid injection rate. The permeability was measured before and after nanofluid injection. This helped us to understand the behavior of the silica nanoparticles in porous media. Results showed that silica nanofluid flooding is a potential tertiary enhanced oil recovery method after water flooding has ceased.     

稠油采出水制备纳米颗粒及其泡沫驱油研究

针对油田采出液难处理、纳米颗粒制备成本高的问题,采用鲁克沁稠油采出液合成菱-球混合形纳米碳酸钙颗粒,通过泡沫稳定性实验及岩心驱替实验,研究纳米碳酸钙颗粒的稳泡性能及该泡沫体系的驱油效果。结果表明:合成的纳米碳酸钙颗粒可有效增强泡沫稳定性;当纳米颗粒质量分数为0.2%、体系矿化度为5 000 mg/L、温度为80 ℃时,纳米颗粒发泡体积为530 mL,析液半衰期达528 s;泡沫体系具有良好的耐盐、耐温及抗吸附性能;水驱油藏(含水率为达80%)转泡沫驱,纳米颗粒泡沫可形成3 MPa左右的稳定驱替压差,采出率由39.84%增至80.16%。利用油田采出液稳定合成出纳米碳酸钙颗粒,可作为泡沫稳定剂提高泡沫稳定性,并用于矿场驱替试验改善泡沫驱油效果。     

Effect of nanoparticles on clay swelling and migration

Clay migration/swelling has been widely documented as the main reason leading to oil recovery impairment. Interactions of clay particles with the medium surface in the presence of permeating fluid have been recognized as a critical parameter controlling the fate of clay particles. These interactions are strongly functions of the ionic strength of the permeating fluid. It is widely reported that reducing the salinity of the reservoir environment facilitates the challenges induced by clay particles. On the other hand, low salinity reservoir environment has been recognized as a very favorable condition for oil recovery. Accordingly, one should consider the positive effect of reducing salinity on oil recovery and its deteriorative effect on clay particles at the same time to improve oil recovery in a controlled formation damage mode. This experimental work aims to investigate the potential remedial effect of different metal oxide nanoparticles to treat clay swelling. Several core flood experiments and micro-model tests have been conducted to achieve the mentioned goal. Furthermore, swelling tests were quantified in terms of swelling indices to explain the effect of nanoparticles on clay swelling. We concluded that although nanoparticles can be used as a permanent stabilizer to prevent clay migration, they are not able to prevent clay swelling and may also increase the pressure drop due to fitting between clay crystals and blocking pores.     

核磁共振T_2分布评价阳离子交换容量方法研究

阳离子交换容量是基于泥质砂岩电阻率的含水饱和度解释模型中的关键项。文中根据含油气泥质砂岩体积模型和扩散偶电层理论,推导了阳离子交换容量与黏土束缚水孔隙度、总孔隙度和溶液矿化度之间的理论关系式。在此基础上,结合核磁共振实验和湿式的化学阳离子交换容量测试资料,提出了一种利用核磁共振T2分布计算阳离子交换容量的方法。实际应用表明,利用该方法计算的阳离子交换容量与岩心分析结果吻合较好,证实该方法是可行的。这一研究成果对于扩展核磁共振测井储层评价应用具有参考价值。     

聚合物溶液对岩石电阻率及岩电参数的影响

摘要：砂岩油层经过聚合物驱替后,聚合物的吸附和滞留是否会导致岩石的导电特征发生变化,是否会引起岩电参数发生变化,将决定饱和度解释模型及参数的选取。通过对不同浓度、不同矿化度的聚合物溶液驱岩石电阻率的实验测量,研究了聚合物溶液对岩石电阻率及岩电参数的影响。得到如下结论：当聚合物溶液矿化度大于4 000 mg/L时,聚合物浓度对溶液电阻率、岩石电阻率及岩电参数的影响均很小,测井解释时可以不予考虑,研究成果为聚合物驱后饱和度解释奠定了基础。     

低渗透砂岩油藏渗吸采油影响因素研究

通过对低渗透砂岩应用静态渗吸实验方法,研究界面张力、渗透率、原油黏度、渗吸液矿化度对渗吸过程的影响规律,认识不同因素对渗吸采油效率的影响。结合渗吸机理,通过渗吸速度、渗吸采收率的比较,发现一定范围内,界面张力为10-1mN/m数量级、较高渗透率、较低原油黏度、较高渗吸液矿化度条件下,表现出较好的渗吸效果。     

Effects of magnesium and potassium sulfates on oil recovery by water flooding

Conventional water flooding has been applied successfully worldwide using sea water and/or formation brine. Two processes are proposed to improve oil recovery by water flooding such as; lowering water salinity as LoSal (300 to 5,000 ppm) and changing concentration of cations and/or anions as designer water.This experimental study investigates combined effects of concentration of magnesium and potassium sulfates with consideration of sodium chloride salinity on oil recovery by water flooding. To achieve the objectives of the study, nine flood experiments were conducted using actual sea water and synthetic water injected through actual sandstone reservoir cores. Three experiments were achieved using actual Egyptian sea waters of Al-Obayied, Balteam and Abo Rudies to investigate the combined effect of magnesium and potassium sulfate concentration on oil recovery. Three experiments were conducted to study the combined effect of Magnesium sulfate and sodium chloride contents on oil recovery. In addition, three other experiments were carried out to investigate the effect of potassium chloride concentrations associated with sodium chloride salinity (higher than the 5000 ppm stated for low salinity process) on oil recovery.The results revealed that sea water of higher content of magnesium sulfate and potassium sulfate increases the oil recovery by water flooding. In addition, the increase of concentration of magnesium sulfate with lower sodium chloride increases the oil recovery by designer water injected containing sodium chloride. It is also concluded that the increase of potassium sulfate increases the oil recovery. The increment in oil recovery by increase of magnesium, and/or potassium sulfate is attributed to wettability alteration to more water-wet, higher pH condition and also to the decrease in sodium chloride associated in the same water injected.The application of the attained results will have real importance in designing the concentration of magnesium and/or potassium concentration of the designer water injected with consideration of sodium chloride salinity of the reservoir.     

阳离子表面活性剂在不同砂岩表面的吸附与吸附焓变研究

驱油过程中，阳离子表面活性剂不仅能够降低油水界面张力，而且能够改变岩石表面的润湿性。为了加深对阳离子表面活性剂与砂岩表面作用机理的认识，用紫外分光光度法测定了阳离子表面活性剂在不同润湿性砂岩表面的吸附量，并利用相应的数学公式计算了吸附焓变。吸附量的测定说明阳离子表面活性剂在砂岩表面的吸附符合Langmuir吸附规律，不同润湿性砂岩表面的饱和吸附量不同，油砂表面的饱和吸附量最大，亲油表面的饱和吸附量中等，亲水表面的饱和吸附量最小。吸附焓变与吸附量相对应，油砂表面吸附焓变最大，亲油表面的吸附焓变中等，亲水表面的吸附焓变最小。这说明阳离子表面活性剂与油砂表面的作用最强，有利于改变储层岩石表面的性质，提高洗油效率。     

Study of the numerical simulation of tight sandstone gas molecular diffusion based on digital core technology

Diffusion is an important mass transfer mode of tight sandstone gas. Since nano-pores are extensively developed in the interior of tight sandstone, a considerable body of research indicates that the type of diffusion is mainly molecular diffusion based on Fick’s law. However, accurate modeling and understanding the physics of gas transport phenomena in nanoporous media is still a challenge for researchers and traditional investigation (analytical and experimental methods) have many limitations in studying the generic behavior. In this paper, we used Nano-CT to observe the pore structures of samples of the tight sandstone of western of Sichuan. Combined with advanced image processing technology, threedimensional distributions of the nanometer-sized pores were reconstructed and a tight sandstone digital core model was built, as well the pore structure parameters were analyzed quantitatively. Based on the digital core model, the diffusion process of methane molecules from a higher concentration area to a lower concentration area was simulated by a finite volume method. Finally, the reservoir’s concentration evolution was visualized and the intrinsic molecular diffusivity tensor which reflects the diffusion capabilities of this rock was calculated. Through comparisons, we found that our calculated result was in good agreement with other empirical results. This study provides a new research method for tight sandstone digital rock physics. It is a foundation for future tight sandstone gas percolation theory and numerical simulation research.     

用动界面张力方法研究原油/盐水界面的性质Ⅱ.起始界面吸附速率和表观扩散系数的测定

定量地计算了原油天然表面活性剂和破乳剂在原油 /盐水界面形成初始阶段时的吸附速率。结果表明 ,破乳剂的起始界面吸附速率远远高于原油天然表面活性剂的相应值 ;水相盐度、体系温度和破乳剂的浓度对原油 /盐水起始界面吸附速率有明显的影响。另外计算了破乳剂在油相中的表观扩散系数 ,并分析了其影响因素。     

砂岩油藏双子表面活性剂渗吸配方研究

本文评价了砂岩油藏低浓度双子表面活性剂（0.2%）渗吸提高采收率效果,考察了双子表面活性剂结构和配方对渗吸的影响。将岩心依次经地层水和原油自吸后放入表面活性剂溶液中测定,发现阳离子双子表面活性剂12-3-12不出油;阴离子双子表面活性剂AAAS采收率为37.27%;阴离子双子表面活性剂12-2-12和磺基甜菜碱C14AB复配后的采收率为38.8%;AAAS和月桂醇醚硫酸钠AES复配体系采收率达53.95%;脱水山梨醇单硬脂酸酯聚氧乙烯醚TW-60和AES复配后的采收率为60.2%。TW-60分子中的酯键不稳定,高温下容易水解断裂,因此选用AAAS和AES的基础配方。加碱（偏硼酸钠）配方渗吸采收率达到59.85% ,比无碱配方渗吸采收率高20.17%。室内一维均质岩心流动实验表明,双子表面活性剂渗吸配方比水驱提高采收率29.8%。     

Evaluation of enhanced oil recovery fromclay-rich sandstone formations

In the last few years, there has been a growing interest in smart water (SW) flooding as economically and environmentally friendly method to Enhanced Oil Recovery (EOR) in sandstone and carbonated reservoirs. Formation damage especially fines migration and clay swelling by lowering salinity and changing the ionic environment, causes the significant decrease in permeability of the sandstone reservoirs. In this study, an experimental study has been undertaken to illuminate the effect of formation damage during smart water injection as the function of clay types. The state of the art procedure has been established in direction of sandpack construction containing favorable clay content. Injection of smart water was performed in sandpacks with different clay types (montmorillonite and kaolinite). The results show that the presence of montmorillonite augments formation damage and enhances oil recovery. Analyzing Interfacial Tension (IFT) experimental data showed that interaction of oil/SW had no great influence on increasing oil recovery. The results have been achieved based on extensive experiments including Differential Pressure (DP) measurements, Zeta potential, and Recovery Factor (RF). Two mechanisms were proposed to interpret permeability reduction and amount of oil produced values which are clay swelling, and detachment/re-attachment for montmorillonite and kaolinite, respectively.