气液交替注入参数的选择

采用气液交替注入技术可以提高高含水油藏的波及效率，改善油层的动用程度，达到提高原油采收率的目的。针对氮气／起泡剂溶液交替注入方式，分别在静态和动态条件下评价了起泡剂的使用浓度、注入速度、气液比、注入方式、岩心渗透率等参数对泡沫封堵性能的影响。综合评价结果表明，气液交替注入方式好于气液同时注入方式，能够在岩心中形成性能稳定的泡沫，对岩心的封堵作用较强。     

克拉玛依油田五2西区克下组油藏气水交替驱开发效果预测及分析

对克拉玛依油田五2西区克下组油藏实施气水交替驱开发效果进行了数值模拟预测及分析,其结果表明与相同井网下注水开发效果相比,采用气水交替驱开发方式能够较大幅度提高原油采收率;在实施气水交替驱期间,不会产生严重的气窜现象而影响开采效果;采用气水交替驱开发方式,不仅注气增油持续时间较长,而且在注气期间和停止注气以后的较长时间内仍有相当比例的注入气存留于地层中,起到了很好的保持地层压力和增强溶解气驱的作用,从而提高了油层动用程度.     

巨厚块状稠油油藏高温调剖技术研究与应用

厚块状稠油油藏往往在开发过程中油层动用程度严重不均,汽窜现象突出,开发效果差,为此,结合辽河油田巨厚块状稠油油藏特点,开展了高温调剖技术研究,确定了调剖剂配方。矿场试验表明,研制的高温调剖剂能够封堵高渗油层,同时注入驱油助排剂对低渗油层进行驱油助排,达到了改善吸汽剖面、提高油层纵向动用程度、改善蒸汽吞吐效果的目的。     

气驱起泡剂综合性能评价

首先对2种起泡剂的发泡性、稳定性、抗盐性、抗温性、抗油性等静态性能进行了测试评价,并优选了起泡剂的最佳使用浓度。然后,针对氮气／水交替注入和氮气／起泡剂水溶液交替注入2种方式,在岩心中对起泡剂的发泡能力及封堵性能进行了评价实验。最后,从改善驱油效率的角度对起泡剂进行了评价。综合评价结果认为,B号起泡剂溶液在岩心中的封堵能力大于A号起泡剂溶液。B号起泡剂溶液与氮气交替注入的方式在岩心产生的阻力因子呈波浪增加这一特点,可能在一定程度上能够克服气水交替过程中注入能力降低的问题,对改善油藏的注入能力是有利的。从驱油效率看,B号起泡剂比A号起泡剂提高原油采收率幅度更大,降低残余油饱和度幅度更大,更适合该油藏的气驱过程。     

耐高温耐盐氮气泡沫调驱实验研究及应用

塔河油田碎屑岩水平井在长期生产后,底水抬升不均匀,导致平面低渗段和垂向上高部位潜力难以动用。氮气泡沫调驱技术可以有效地降低含水率,调整注入剖面,扩大波及体积和水平井顶部油层的动用程度,提高底水油藏采收率。针对塔河油田高温(120℃)、高矿化度(21×10~4mg/L)的地层条件,筛选出耐高温耐盐的HTS-1起泡剂。通过填砂管实验测试了泡沫体系的封堵性能,实验结果表明,氮气泡沫对高渗透率的地层具有较好的封堵性能,对低渗透率地层的封堵效果较差。利用数值模拟技术,优化了氮气泡沫的注入方式和工艺参数。现场的施工应用结果表明,注入氮气泡沫调驱后对应采油井组的采油量增加明显,有效地提高了油藏的采收率。     

氮气泡沫驱提高高渗透特高含水油藏采收率技术——以梁家楼油田纯56块为例

梁家楼油田纯56块高含水、高采出程度,剩余油主要富集于构造顶部及厚油层上部,常规措施挖潜效果越来越差,剩余储量动用难度大,油藏处于低效开发状况,为此,开展了氮气泡沫驱提高采收率技术的研究。重建了该区的三维地质模型,利用数值模拟进行历史拟合和注入参数优化,预测氮气泡沫驱开发指标及经济效益,通过对氮气水、氮气泡沫同注或交替注入4类36个方案开发指标的分析对比,选择氮气泡沫同注,6口注入井分为3组交替注入2个周期,平均单井氮气注入量为73.6×104m3,起泡剂用量为75t,预计提高采收率5.7%。先导试验选取井组1注7采,6口井见效,综合含水率下降0.8%,增油量为8.1t/d,取得了较好的降水增油效果。     

低渗透非均质油藏提高采收率实验研究

低渗透非均质砂岩油藏水驱开发时,注入水易沿渗透率相对高的部位窜流,而低渗透层动用程度差,整体开发效果不佳.对此类油藏,研究水驱后进一步改善开发效果的可行性,并探索提高低渗透层动用程度的有效方法具有重要意义.本文通过长岩心物理模拟实验,考察了低渗透非均质砂岩油藏常规水驱后,依次采用间歇开采、注氮气、水气交替注入等方法对改善开发效果的作用,也探讨了该类油藏水驱后进一步提高采收率的可行性.实验结果证明,通过采取合理方法可以在水驱基础上进一步提高采收率.其中采用间歇开采最多可以获得采收率近7%,但作用有效周期少;注入氮气可以得到约6%采收率,但在气窜后易导致注入气无效循环;水气交替注入方式效果最明显,可以进一步提高采收率15%左右.     

塔河高温高盐油藏冻胶泡沫调驱技术

针对塔河高温高盐油藏强非均质性储层提高采收率的需求,开展了高温高盐油藏冻胶泡沫调驱技术研究。采用Ross-Miles 法和GSC 强度代码法,优选了耐温抗盐起泡剂和冻胶稳泡体系,进而确定了强度可调的冻胶泡沫调驱体系,配方为0.4%~0.5%HTSP 聚合物+0.09%~0.16%RELMNE 交联剂+0.2%~0.3%HTS-1 起泡剂,泡沫综合值是普通泡沫的2 倍以上。通过物理模拟实验评价了冻胶泡沫体系的地层适应性和提高采收率性能。实验结果表明,冻胶泡沫对地层有较好的选择适应性, 在0.6~3.3 μm2 范围内,随着渗透率的增加,残余阻力系数增大,剖面改善效果明显。相比于普通泡沫、单纯气驱和水驱,冻胶泡沫技术能有效启动低渗油层,提高采收率幅度达到26.93%,是普通泡沫的2.3 倍,是注气调驱的6.2 倍,且比普通水驱最终采收率提高14.17%,具有广阔的应用前景,为塔河高温高盐油藏进一步提高采收提供了新方法。     

克拉玛依油田五2 西区油藏气水交替驱方案设计

针对克拉玛依油田五₂西区克下组油藏设计了23 个气驱方案并预测了各方案的开采动态指标,通过数值模拟对注气年限、日注气速度和气水交替周期等注入参数进行了敏感性分析论证。研究结果表明,五₂ 西区克下组油藏在气水交替驱开发方式下,气水交替周期的长短不是开发动态影响的敏感因素;气水交替年限和日注气速度对注气增产油量和气换油率影响较大。与注水开采相比,注气开采能够较大幅度提高原油采收率,是改善高含水油藏开采效果的有利手段。     

耐温抗盐CO_2驱油泡沫封窜体系实验研究

针对腰英台油田油层温度高、产出液矿化度高等特点,研制一种耐温抗盐CO_2驱油泡沫封窜体系。结果表明,在相同起泡剂浓度下,稳泡剂W3使泡沫半衰期提高10%。当起泡剂C与稳泡剂W3质量比为2∶1时,泡沫体系综合发泡能力最佳;另外,采用泡沫体系溶液和CO_2气体交替注入的方式进行封窜,封堵率95%以上,能满足腰英台矿场要求。     

Maximizing the Oil Recovery Through Miscible Water Alternating Gas (WAG) Injection in an Iranian Oil Reservoir

In recent years there has been an increasing interest in water alternating gas (WAG) processes, both miscible and immiscible. Microscopic oil displacement and sweep efficiency of waterflooding and continuous gas injection can be improved by WAG injection. In this work, by designing various scenarios of water and gas injection, WAG injection and simultaneously water and gas injection, the recovery and residual oil saturation obtained by implementing these methods are compared to choose the appropriate method of injection. The results showed that simultaneously the water and gas injection method has the highest recovery but from economic view, WAG process is the best enhanced oil recovery method to increase the recovery. In WAG method, the values of gas oil ratio and water cut are the smallest, so in this case, operational and process facilities problems and their costs are the minimum.     

Experimental Investigation of Miscible CO2 Flooding

Abstract

Management of water alternating gas (WAG) injection projects requires making decisions regarding the WAG ratio, half-cycle-slug size, and ultimate solvent slug size. The impact of these decisions affects the capital cost and ultimate incremental oil recovery. Core flooding runs were conducted on 2 and 4 ft core samples. Injection scheme (continuous gas injection [CGI] vs. WAG), WAG ratio, and slug size were investigated. In addition, miscible WAG flooding as a secondary process was investigated and its efficiency was compared to the conventional tertiary miscible gas flooding. Miscible gas flooding at different miscible WAG parameters (WAG ratio and slug size) indicate that 1:2 WAG ratio at 0.2 PV slug size is the best combination yielding the highest recovery and tertiary recovery factors. Miscible WAG flooding as a secondary process indicated a higher ultimate recovery compared to the conventional tertiary WAG flooding. However, a larger amount of gas injection is consumed particularly in the early stages of the injection process. Miscible CGI mode conducted using n-Decane as oleic phase appears to have better performance than miscible WAG injection in term of recovery. When light Arab crude oil was used as oleic phase, higher recovery was obtained for miscible WAG flooding. The reversal trend seen in is believed to be due to the presence of crude oil, which alters the rock wettability toward an oil-wet condition, preventing the water blockage during the WAG process.     

Simulation of WAG floods in an oil-wet micromodel using a 2-D pore-scale network model

In this paper, we describe some novel multi-cycle water-alternating-gas injection (WAG) floods in 2-D etched glass oil-wet micromodels, which we have simulated using our recently developed three-phase, 3-D mixed-wet network model. A similar approach was described previously for WAG floods in a water-wet system [van Dijke, M.I.J., Sorbie, K.S., Sohrabi, M., Tehrani, D., Danesh, A., 2002. Three-phase flow in WAG processes in mixed-wet porous media: pore-scale network simulations and comparison with micromodel experiments. SPE 75192, Proc. SPE/DOE Symposium on Improved Oil Recovery, Tulsa, Oklahoma, April 2002]. Although direct observation at the pore-scale is possible in the micromodel, some experimental data, required as input parameters for the network model, is not directly available. Therefore, a limited sensitivity study is performed, investigating the effects of the presence or absence of oil wetting films, around either gas or water, and the degree of oil wettability, leading to variation of the wetting order of gas and water. Based on these sensitivity calculations, oil wetting films are implemented around water only, in a limited fraction of all pores, such that the initial water pattern can be kept relatively sparse. Furthermore, the evidence support the micromodel being strongly oil-wet, since this more readily leads to gas displacing oil rather than water. With the estimated input parameters concerning films and wetting order, we then directly simulated the two oil-wet micromodel experiments, the first one starting with a water flood and the second one starting with a gas flood. Satisfactory agreement between simulation and experiment is found in terms of fluid distributions and oil recovery profiles. In addition, analysis of the displacement statistics, including the length (e.g. singles, doubles, multiples) and types of displacements (e.g. gas displacing oil), are broadly consistent with experiment, as far as this information is available. This paper illustrates the application of a network model to validate the local assumptions on the underlying pore-scale mechanism (on films and wettability), which are then used to predict what the emergent global properties are of the three-phase displacement processes in the micromodel.     

Estimation of the water–oil–gas relative permeability curve from immiscible WAG coreflood experiments using the cubic B-spline model

Immiscible water-alternating-gas (WAG) flooding is an EOR technique that has proven successful for water drive reservoirs due to its ability to improve displacement and sweep efficiency. Nevertheless, considering the complicated phase behavior and various multiphase flow characteristics, gas tends to break through early in production wells in heterogeneous formations because of overriding, fingering, and channeling, which may result in unfavorable recovery performance. On the basis of phase behavior studies, minimum miscibility pressure measurements, and immiscible WAG coreflood experiments, the cubic B-spline model (CBM) was employed to describe the three-phase relative permeability curve. Using the Levenberg– Marquardt algorithm to adjust the vector of unknown model parameters of the CBM sequentially, optimization of production performance including pressure drop, water cut, and the cumulative gas–oil ratio was performed. A novel numerical inversion method was established for estimation of the water–oil–gas relative permeability curve during the immiscible WAG process. Based on the quantitative characterization of major recovery mechanisms, the proposed method was validated by interpreting coreflood data of the immiscible WAG experiment. The proposed method is reliable and can meet engineering requirements. It provides a basic calculation theory for implicit estimation of oil–water–gas relative permeability curve.     

倾斜油藏水气交替驱提高采收率机理研究

以冀东油田柳北大倾角油藏为原型建立了剖面地质模型,在流体相态拟合基础上．应用数值模拟技术讨论了地层倾角、油层厚度、地层压力、注入速度、气水比等参数对倾斜油藏水气交替驱开发效果的影响。结果表明,倾角的存在可显著提高水气交替驱开发效果,模型中倾角15°时提高采收率比无倾角时大6．18％;对于倾斜油藏。油层厚度越大对水气交替驱越有利．而无倾角时,规律相反;通过控制注入速度,倾斜油藏水气交替驱在较低的适宜压力下也可获得较好的开发效果;此外注入速度、气水比等对倾斜油藏水气交替驱的影响与无倾角时规律不同且均存在最佳取值。     

The Areal Sweep Efficiency of the First-contact Miscible Displacements: An Experimental Approach

Abstract

Solvent flooding using the water alternating gas (WAG) technique is very important for predicting the process performance. This technique has been employed in a number of oil fields. However, little data are available in the literature. Therefore, there is an immense need for the sweep efficiency data resulting from first-contact miscible flooding, particularly in view of conducting reservoir simulation studies. In this article, we conducted a series of WAG displacements through glass bead packs. A number of miscible WAG displacement tests were conducted at WAG ratios of 1:1, 1:2, and 2:1. Constant flow rates were used to mask the effects of capillary number on sweep efficiency. Experimental results revealed that the WAG ratio affects the sweep efficiency of the miscible flooding process. In addition, new correlations of areal sweep as function of mobility ratio at various WAG ratios were developed. The data provided can be useful to the oil industry in conducting analytical and numerical modeling studies of miscible WAG processes.     

A laboratory study of hot WAG injection into fractured and conventional sand packs

Gas injection is the second largest enhanced oil recovery process,next only to the thermal method used in heavy oil fields.To increase the extent of the reservoir contacted by the injected gas,the gas is generally injected intermittently with water.This mode of injection is called water-alternating-gas(WAG).This study deals with a new immiscible water alternating gas(IWAG) EOR technique,"hot IWAG" which includes combination of thermal,solvent and sweep techniques.In the proposed method CO2 will be superheated above the reservoir temperature and instead of normal temperature water,hot water will be used.Hot CO2 and hot water will be alternatively injected into the sand packs.A laboratory test was conducted on the fractured and conventional sand packs.Slugs of water and CO2 with a low and constant rate were injected into the sand packs alternatively;slug size was 0.05 PV.Recovery from each sand pack was monitored and after that hot water and hot CO2 were injected alternatively under the same conditions and increased oil recovery from each sand pack and breakthrough were measured.Experimental results showed that the injection of hot WAG could significantly recover residual oil after WAG injection in conventional and fractured sand packs.     

Experimental investigation of effect of asphaltene deposition on oil relative permeability,rock wettability alteration,and recovery in WAG process

Asphaltene deposition is considered to be one of the most problems during oil productions. This work describes the effect of asphaltene precipitation and deposition on relative permeability of reservoir rock during water alternating gas (WAG) injection process. The main objective of this work is experimental investigating of relative permeability change of reservoir fluid due to asphaltene deposition on application of WAG process by use of core flood setup. Result of this paper investigate the relative permeability change during WAG process with different asphaltene content that help to make better development decisions for a reservoir with fluid with specific asphaltene content.     

多轮次调剖数值模拟研究

多轮次调剖是一项重要的稳油控水措施,提出了三维三相多轮次调剖数学模型,研制了多轮次调剖模拟器。综合考虑了模拟器中堵剂驱油过程中的物理特性,为高含水期油藏进行多轮次调剖油藏工程方案研究提供了有力的工具。结合具体油藏模型,进行了调剖时机、堵剂用量及封堵位置对调剖效果的影响研究。结果表明,在油田进入高含水期,要不断地进行调剖,及时进行各轮次调剖堵水措施间的接替,使油田含水得到控制,产量稳定增长。