The Impact of Surfactants on Wettability Change and Level of Water Imbibition in Relation to EOR in Carbonate Reservoirs

Some anionic, cationic, and nonionic surfactants have been examined on actual reservoir samples. Thin section analysis and core flooding techniques were used for the petrophysical and mineralogical assessments of the rock samples. Spontaneous imbibition experiments were conducted using oil-saturated plugs in combination with reservoir brine and surfactant solutions separately. Capillary pressure measurements were conducted both before and after wettability alteration. Amott-Harvey and USBM wettability indices were determined. Brooks-Corey and Brooks-Corey-Mualem models were used. Among the surfactants a cationic one could best improve the spontaneous imbibition. Fairly good fit was observed between experimental capillary pressure curves and those calculated by Brooks-Corey model.     

Numerical Model of Countercurrent Spontaneous Imbibition in Underbalanced Drilling: Formation Damage Investigation

Abstract

Although mud filtrate invasion is mostly concerned in overbalanced drilling (OBD), it is shown that it also occurs during underbalanced drilling (UBD) operations. UBD is a drilling operation in which the hydrostatic head of a mud column is maintained at a pressure less than that of fluid in the porous medium. Formation damage due to mud invasion in OBD could be eliminated in UBD. However, this benefit of UBD can be missed when pressure suddenly turns to overbalance and/or spontaneous imbibition. During UBD it is difficult to maintain mud pressure less than formation pressure especially for short periods of time for operational reasons such as bit trips, and it will cause major damage due to nonexistence of internal and external mud cake. Also, spontaneous imbibition, which occurs in low-permeable reservoirs, causes drilling fluid invasion. In this case, the hydrostatic head of drilling mud is less than formation pore (oil phase) pressure, but it may be higher than water-phase pressure in the formation because of capillary pressure. This causes the flow of water into the formation, which causes formation damage. The aim of this study is to present a model for spontaneous imbibition of water into the water-wet formation during underbalanced drilling and to investigate the effect of drilling fluid, reservoir rock, reservoir fluid, and drilling operation parameters on the extension of damage in nonfractured formations. The numerical solution of governing equations and sensitivity analysis on different parameters are presented. The results show that in the case of strong capillary pressure, (1) the damage due to spontaneous imbibition is considerable and (2) the most effective criteria are temporary overbalanced and static drilling fluid situations where both increase the extend and amount of drilling filtrate invasion. Also, it was concluded that a low UBD pressure difference causes damage, whereas the very high UBD pressure difference is inefficient.     

Modelling and simulation of drop spreading on fibrous porous media

Various operations in petroleum processing, textile technology, printing and composite processing involve wetting and spreading phenomena of liquids in porous media. These phenomena are being investigated using various tools, prominent among them being the spreading of a liquid drop on a porous medium. The spreading is governed by the inertial, gravitational, viscous and capillary forces and their relative importance have been studied to understand the underlying phenomena. In this work, drop spreading on heterogeneous porous media, such as composite reinforcing fabrics, has been investigated. The liquid drop spreading has been modelled in two stages: the flow of liquid on the surface of fabric and the imbibition of the liquid into the fabric due to inter-tow and intra-tow flow of the fluid. The model equations are formulated by making a hypothetical equivalent model of the fabric. The resulting equations are solved numerically. The model is used to simulate the spreading of liquid drops on glass fabrics. The drop spreading is characterized by height, contact radius and contact angle. The front of the liquid within the porous media can also be monitored through the model. Initially, a parametric study on the effect of fabric and tow porosities, the tow radius and the droplet volume on the imbibition time is presented. Finally, the model results are compared with the experimental results from literature. It is shown that the model can capture the essential features and provide insight into drop spreading on heterogeneous porous media.     

Experimental study on preparation of nanoparticle-surfactant nanofluids and their effects on coal surface wettability

To improve the efficiency of coal seam water injection, the influence of nanofluids on coal surface wettability was studied based on the nano drag reduction and injection enhancement technology in the field of tertiary oil recovery. The composition optimization and performance evaluation of nanofluids with nano-silica and sodium lauryl sulfate as the main components were carried out, and the effects of the nanofluid with the optimal ratio on coal wettability were studied through spontaneous upward imbibition experiments. The results show that the composite nanofluid has a lower surface tension, and the lowest value of the interfacial tension is 15.79 mN/m. Therefore, the composite nanofluid can enhance the wettability of coal. However, its effects on coal samples with different metamorphic degrees is different, that is, low rank coal is the largest, middle rank coal is the second, and high rank coal is the least. In addition, a functional relationship between time and imbibition height is found for pulverized coal with different particle sizes. When the particle size of pulverized coal is 60–80 mesh, the wettability of nanofluid to coal is best. The findings in this paper provide a new perspective for improving the water injection efficiency for coal seams with low permeability.     

低渗透岩心渗吸实验研究

一般低渗透储层只有存在大量的天然裂缝才能经济有效的进行开发。由于毛管力的作用,油从岩心基质自发渗吸到裂缝中是一种十分重要的采出机制。因此,在评价低渗透油藏石油采收率时具有重要作用。实验采用长庆油田低渗透储层天然岩心,进行自发渗吸实验。实验结果表明,渗透率（0．1～1．0）×10^-3μm。级别的岩心,渗吸采收率在11％～12％之间;渗透率（2～4）×10^-3μm^2级别的岩心,渗吸采收率在14％～18％之间。同一块岩心不同渗吸液对比实验表明,活性水因降低了界面张力而显著提高的石油采收率,增幅可达10％。     

砂岩储层润湿性研究进展

润湿性是储层的一个基本特征参数,是影响油藏生产的一个重要因素,尤其在低渗透砂岩油藏中储层润湿性影响作用更为明显。本文通过对目前储层润湿性方面的研究进展进行了详细的调研,系统总结出储层润湿性的形成机理、表现特征、润湿程度的衡量标准及影响储层润湿性改变的因素等方面的研究成果,并介绍了测定储层润湿性的几种方法和技术。认为:弄清润湿性的形成机理是有效减低润湿性对储层伤害的关键;了解润湿性的表现特征是形象认识储层润湿性影响的有效方式;对储层润湿性影响因素的分析,有利于针对性的选用测定润湿性的方法和技术。在对相关研究成果进行全面系统总结的基础上,提出因润湿性改变而造成储层伤害的有效措施,合理利用各种方法减小砂岩储层润湿性伤害作用,提高砂岩油藏的开发效果。     

低渗透油藏裂缝动态渗吸机理实验研究

根据低渗透油藏裂缝与基质交渗流动的理论模型和物理模型,建立了裂缝与基质之间动态渗吸的实验方法并就裂缝内驱替速度、油水黏度比、润湿性,初始含水饱和度等参数对动态渗吸效果的影响进行了实验研究.对于低渗透裂缝性油藏,在压力梯度作用下水在裂缝内流动,同时由于毛细管力作用水渗吸到基质内,渗吸到基质中的水将油替换出来渗流到裂缝中,注入水再将裂缝中的油驱替到出口端,这就是裂缝与基质之间的交渗流动.动态渗吸实验结果表明:在本实验条件下,存在一个最佳驱替速度(3.0 mL/h),渗吸效率最高为35.5%;在一定的驱替速度范围内,由干毛细管力与黏性力的共同作用,渗吸效果最好.亲水岩心的动态渗吸效果最好.油水黏度比越小,动态渗吸效果越好.初始含水饱和度越高,毛细管力越小,动态渗吸效果越差.图6参20     

纳米孔隙储集层动态渗吸数学模型

在考虑动态接触角效应、纳米限域效应、惯性效应和入口端效应的基础上,建立了纳米尺度孔隙中油-水渗吸方程,推导出固-油-水三相接触线摩擦系数与界面区流体黏度的关系式,结合毛细管束模型和对数正态分布理论,得到了致密岩心渗吸模型,并对影响渗吸动态的关键参数进行了分析.研究表明,纳米孔隙渗吸过程中,动态接触角效应对渗吸的影响最为...     

Mathematical modeling of water uptake through diffusion in 3D inhomogeneous swelling substrates

Diffusion‐driven water uptake in a substrate (imbibition) is a subject of great interest in the field of food technology. This is a particular challenge for rice grains that are preprocessed to accelerate the water uptake, i.e., to reduce the cooking time. Rice preprocessing disrupts the mesostructural order of starch and induces a microporous structure in the grains. The meso‐ and microstructural length scales have not been considered in joint approach until now. The (re)hydration of rice grains can be modeled by free (concentration‐driven) diffusion or by water demand‐driven diffusion. The latter is driven by the ceiling moisture content related to the extent of gelatinization of the rice substrate network. This network can be regarded as a fractal structure. As the spatial resolution of our models is limited, we choose to model the apparent water transport by a set of coupled partial differential equations (PDEs). Current models of water uptake are often limited to a single dimension, and the swelling of the substrate is not taken into account. In this article, we derive a set of PDEs to model water uptake in a three‐dimensional (3D) inhomogeneous substrate for different types of water diffusion as well as the swelling of the substrate during water uptake. We will present simulation results for different 3D (macroscopic) structures and diffusion models and compare these results, qualitatively, with the experimental results acquired from magnetic resonance imaging. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Spontaneous imbibition in porous basalt mediated by microbial perturbations

The fate and transport of organic contaminants in subsurface depend on complex interactions between several system components such as fluid chemistries, geochemistry, microbiology, geology, and physical parameters. This study describes imbibition studies to assess the incipient interaction between selected hydrocarbons and pertinent mineral surfaces as a function of aqueous phase chemistry and microbiological perturbation. Microbial perturbations may have significant impact with respect to monitoring the contaminants and finding better strategies for remediation. Basalt cores used in laboratory experiments were obtained at depths of 200 to 300 ft from a test well located at the Idaho National Laboratory (INL). Thin section analysis of core samples showed that the basalt was formed from feldspar and pyroxene crystals with most of the pore space occurring as vugs. Mercury injection tests indicated a wide range of pore throat sizes through which the vugs could be accessed. All of the vugs were connected by inter/intra crystalline pores that were less than about 0.5 μm in width. Although most pore space occurs as vugs, miscible displacement tracer tests did not reveal significant heterogeneity. Base-case spontaneous imbibition tests were conducted on cores that had been fully saturated with dodecane using synthetic groundwater as the invading phase. Imbibition tests were then performed against basalt with cell-free supernatants and sonicants (diluted by synthetic groundwater) of three indigenous microorganisms, Acinetobacter genospecies, Arthrobacter globiformis and Bacillus atrophaeus that had been isolated from the test well. Waterflooding was performed on each core after imbibition testing to obtain the Amott wettability index to water.Imbibition tests show that, although the basalt/dodecane/synthetic groundwater system was strongly water-wetted, the scaled imbibition rate was much slower than previously observed for other core types such as sandstone and limestone. The production of organics obtained by waterflooding after spontaneous imbibition was close to zero, indicating that the basalt was strongly water-wet. At the same time, the water permeability by waterflooding was often extremely small at imbibition residual organic saturation. The distribution of trapped oil and its effect on relative permeability in the crystalline matrix may explain the relatively slow imbibition rates that were observed. The addition of microbial components in the invading aqueous phase resulted in higher imbibition rates and final recovery of organics than observed for synthetic groundwater.