The Effect of Rock-crude Oil-fluid Interactions on Wettability Alteration of Oil-wet Sandstone in the Presence of Surfactants

The aim of the present work was to study the rock-fluid interaction in presence of surfactants and thereby their effects on wettability alteration of oil-wet sandstone for its essentiality in enhanced oil recovery. Characterization of sandstone sample and its interaction with crude oil, brine and surfactants were investigated by Fourier Transform Infrared spectroscopy. Scanning electron microscope and X-ray diffraction studies were performed to characterize the sandstone sample. Critical micelle concentrations of sodium dodecyl sulfate, cetyltrimethylammonium bromide, Tergitol 15-S-7, Tergitol 15-S-9, and Tergitol 15-S-12 were determined by interfacial tension measurement method. Wettability alteration of sandstone was studied by contact angle method.     

Application of Biosurfactants to Wettability Alteration and IFT Reduction in Enhanced Oil Recovery From Oil–Wet Carbonates

To obtain potentially applicable microorganisms to an effective in situ microbial enhanced oil recovery operation, bacteria that were compatible with the harsh conditions of a petroleum reservoir were isolated from a crude oil sample. The application of an oil spreading technique showed that all of the isolates were capable of producing biosurfactants from both the glucose and crude oil as carbon sources. The secreted biosurfactants could at least reduce the surface tension 20 mN/m and for one of the isolates; the surface tension value dropped below 40 mN/m. In addition, the contact angle measurements revealed that the produced biosurfactants could effectively alter the wettability of the oil saturated rock samples. At last, the effect of isolates and their biosurfactants on improving oil production from oil saturated rock samples was investigated. It was observed that the presence of bacteria in the system could increase the amount of produced oil in comparison with the case where cell free biosurfactants were utilized.     

Wettability alterations due to aging in crude oil; wettability and Cryo-ESEM analyses

Several studies of fluid distribution and wettability on the pore scale have been reported, but to our knowledge, none of them have attempted to obtain quantitative measurements. In this paper, quantitative wettability results from Cryo Environmental Scanning Electron Microscopy (Cryo-ESEM) are reported and compared to wettability measurements with traditional methods. The wetting properties of sandstone cores, aged in crude oil, have been investigated using the combined Amott/USBM method. The results show that with increasing aging time, the wetting properties changed from water wet to mixed wetting. Pieces of the same cores have then been analyzed using an Electroscan 2020 ESEM with an attached Cryo unit. Combined with Energy Dispersive X-ray Spectroscopy (EDS), these analyses have given images of the surface, showing the liquid distribution and which phase is contacting the mineral surface.The combination of these methods has proved that using a Cryo-ESEM to investigate wetting properties can give very valuable information although the results are somewhat scattered. Compared to the traditional wetting analyses, this method also gives us an image of the liquid distribution, which is a very valuable input for pore network simulation. It is shown that there is a good agreement between the fraction of the pore walls that are contacted with brine and the Amott/USBM index. A new index based on ESEM data is proposed, with the same range as the Amott–Harvey index.Cryo-ESEM avoids two problems encountered in other SEM methods. First, there is no possibility of a coating layer showing up in the element analyses, since these samples are uncoated. Secondly, the same sample can easily be reexamined by simply refracturing.     

Wettability Alteration by Salinity and Calcium Bridge in a Crude Oil/Brine/Rock System

Wettability alteration has been considered to be a key factor behind low salinity water effect. Though the wettability alteration is widely accepted to be determined by oil components, mineral surfaces and ions in aqueous phase, how the brine chemistry (ionic type and strength) impacts the wettability is still unknown. In this study, the auhtors conducted spontaneous imbibition, contact angle, and zeta potential measurements to investigate: (a) how the ions of the thin film of water between oil and mineral interact with oil and rock to alter the wettability of crude oil/brine/rock system and (b) the mechanism of wettability alteration behind low salinity water effect.     

Simulation of Wettability Alteration by Low-Salinity Water Injection in Waterflooded Carbonate Cores

Low-salinity water injection is an emerging improved oil recovery technique due to its simplicity compared to other water based improved oil recovery methods. In this study, the wettability alteration option in the authors’ in-house simulator is used to history match and provide some insights in different seawater dilution cycles based on recently published corefloods. Two newly proposed methodologies to model dilution cycles are employed. The authors successfully modeled the experiments enhancing the wettability alteration model in the simulator using two different scaling factors. The study also revealed that the process is more sensitive to oil relative permeability compared to that of the water phase. A linear interpolation model for residual oil saturation (S_or) was proposed.     

凝析油气藏气湿反转解水锁的实验研究

气湿反转是目前解决油气藏水锁损害的有效方法之一.通过溶胶-凝胶法和氟烷基甲基丙烯酸共聚物Zonyl 8740的修饰,使岩心表面的润湿性发生了气湿反转.通过做接触角测量实验,发现溶胶的陈化时间、溶胶-凝胶处理时间、热处理温度、氟化浓度和氟化时间对岩心的浸润性有明显的影响.毛细管上升实验结果表明,用溶胶和Zonyl 8740处理后,气/水体系和油/气体系中的润湿性由优先液湿转变为气湿.利用扫描电子显微镜对处理岩心表面的形貌和能谱进行分析显示,用溶胶和Zonyl 8740共同处理岩心后,岩心表面具备了微细的粗糙结构和低表面能物质.岩心驱替实验结果表明,通过Zonyl 8740处理后,岩心中水的渗透率比未处理时增大了4倍.     

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.     

伊拉克Ahdeb油田稠油层测井识别及分布特征研究新方法

伊拉克Ahdeb油田Khasib油藏的开发现状迫切需要明确稠油的分布特征,以降低钻井风险。探讨了稠油层的测井响应特征,研究了稠油含量指数计算方法,在三维空间刻画出稠油的分布特征。分析稠油和轻质油基本性质的差别出发,通过理论模型分析阐述了稠油层和轻质油层在电阻率、中子孔隙度、密度以及核磁共振测井响应特征上的差异。利用阿尔奇公式计算冲洗带残余油饱和度结合中子孔隙度与密度曲线的分离幅度,定量计算了稠油含量指数,将其应用于三维地质模型中,直观地展示了稠油在各小层的分布特征。结果表明水平井轨迹穿过稠油含量指数高于0.2的区域或低产,或无法投产,生产特征与稠油分布特征完全吻合,充分证明了稠油分布特征描述的可靠性。     

新型Elman网络在乙烯精馏塔软测量建模中的应用

针对前馈神经网络在石油化工软测量建模中存在的不足，采用递归型Elman网络实现动态石化生产过程的建模。提出了一种新型的Elman网络——HF Elman网络，将其应用在某石化厂600kt／a乙烯生产装置乙烯质量指标的软测量建模，并与前馈网络和Elman网络的建模性能进行了比较，仿真结果表明，HF Elman网络具有良好的动态建模能力，能够更好地实现乙烯精馏塔出口成分含量的软测量建模。     

一种确定低渗透油藏启动压力梯度的新方法

原油中的表面活性组分在多孔介质的孔道壁面上吸附形成了边界层,从而使得低渗透油藏的启动压力梯度远大于中高渗油藏的启动压力梯度。首先分析了边界层的形成及影响因素,然后建立一个孔隙网络模型来进行渗流模拟。通过在孔道中引入边界层,可以利用孔隙级网络模型作出压力梯度与渗流速度之间的关系曲线,即渗流曲线。由渗流曲线便可进一步确定启动压力梯度。该方法首次在确定启动压力梯度时直接考虑了边界层的影响,而且将孔隙级网络模型的应用进一步扩展到了低渗透油藏。     

一种识别抽油机井示功图的新方法

在现有示功图模式识别方法的基础上,运用矩特征法撮了示功图的８个特征量,借助人工神经网络作为分类器,实现了采油 抽油机井示功图的自动识别。通过油田实例的检验,取得了较好的效果。     

A New Approach to the Modeling of a Simple Re-infiltration Gravity Drainage Process in Naturally Fractured Reservoirs

Abstract

One of the most important concerns regarding prediction of production performance in naturally fractured reservoirs is the issue of re-infiltration phenomena.

In this study, the modeling of a simple re-infiltration process with no effect of capillary continuity between blocks is presented by extending the gravity drainage mechanism for a single block.

First, a qualitative analysis of the gravity drainage process through porous media was conducted and the role of gravity and capillary forces was investigated.

Then a model for one-dimensional gravity drainage in a single block was developed in dimensionless form, a modified version of which can be found in the literature. Then, using the method of separation of variables, the corresponding partial differential equation was solved for a single block with certain boundary and initial conditions.

The upper boundary is a no-feed boundary and at the lower boundary the gas saturation is always zero. At the initial condition, the gas saturation is equal to zero throughout the block.

In order to model the simple re-infiltration process, the above-mentioned problem for concept was used and, based on the fact that the blocks of a stack governed by simple re-infiltration process act as single block, using a MATLAB program (The MathWorks, Inc., Natick, MA), the rate of drainage and cumulative production as function of time were obtained. The results are in very good agreement with the nature of the process in an actual case. This method can be extended to solve the problem of a stack of N blocks.     

A New Method to Prevent Stealing Gas in a Natural Gas Supply System

The problem of stealing gas through natural gas supply system is getting increasingly serious in China and other countries. The authors introduce a new technique to prevent and reduce behavior of stealing gas. The new technique is to establish a monitoring network through which data of consumed gas volume and gas flow rate of home gas meters can be monitored dynamically. Through analysis of these data, the monitoring center can automatically discriminate the potential users with stealing gas behavior and then report list of the users to the monitoring center. This method prevents the occurrence of stealing gas effectively.     

复杂天然气管网周转量计算模型及其应用——以川渝天然气管网为例

管网周转量测算是控制管道运行现金成本、管道能源消耗,实现降本增效的措施之一。川渝天然气管网作为目前国内最复杂的区域性管网（由枝状管网和环形管网交错结合在一起）,具有进出气点多、管线压力等级复杂、管网输配调度灵活、调峰方式多样等特点,同时存在天然气气体流向复杂、原始数据采集不实时、计算周期难确定等问题。为此,根据该复杂天然气管网特点,建立了枝状管网和环状管网管线图模型,采用“微元法”原理和方法,建立了较为适合复杂天然气管网特点的周转量计算模型,将整个管网系统按照管理层级层层分解,将周转量的测算细分到每一管段,以作业区作为一个计算区间进行测算,再进行层层累加求和,即得到整个系统的周转量。通过对比实例计算,得出了用“微元法”计算复杂天然气管网周转量的方法较为符合川渝管网的实际的结论。该成果可为全国联网天然气管道周转量的测算提供借鉴,有助于联网管道的销售管理、结算管理和运行管理。鉴于复杂天然气管网的特殊性,可采用年度或季度平均法,在统计分析的基础上计算周转量。     

西气东输水网地段管道施工系列方法和技术

水网地段管道施工是西气东输管道工程的难点,施工单位按照"以水治水,因地制宜"的总体思路,结合大口径管道施工特点,探索形成了水网地段管道施工系列方法和技术,为今后类似工程提供了宝贵经验.文章归纳总结了西气东输水网地段管道施工中具有创新性和实用性的施工方法和技术便道和便桥修筑、加固系列方法;施工作业带清理系列方法;运布管系列方法;管段下沟系列技术;管道穿越系列技术.     

海上稠油油田蒸汽吞吐产量确定新方法

针对目前蒸汽吞吐产量预测模型假设条件简单、普适性差等问题,一般采用测试法和类比法综合确定海上稠油油田蒸汽吞吐初期产量。由于目前海上油田通常只开展常规测试,无法直接获得热采开发初期产量。笔者提出海上稠油油田蒸汽吞吐初期产量确定新方法,建立蒸汽吞吐相对于常规开发的初期产量倍数预测模型,通过蒸汽吞吐产量倍数,将常规测试确定的产量转化为蒸汽吞吐产量。研究表明,蒸汽吞吐初期产量倍数主要受储集层渗透率、原油黏度、注入强度、蒸汽干度等因素影响,利用正交试验设计和多元回归等方法,建立海上稠油油田蒸汽吞吐初期产量倍数与油藏地质参数及注入参数之间的非线性预测模型,该模型经实际生产数据验证,预测误差小于5%,可靠性高,能够为海上稠油油田蒸汽吞吐初期产量的确定提供依据。