Chemical effects of sulfur dioxide co-injection with carbon dioxide on the reservoir and caprock mineralogy and permeability in depleted gas fields

The most suitable candidates for subsurface storage of CO₂ are depleted gas fields. Their ability to retain CO₂ can however be influenced by the effect which impurities in the CO₂ stream (e.g. H₂S and SO₂) have on the mineralogy of reservoir and seal. In order to investigate the effects of SO₂ we carried out laboratory experiments on reservoir and cap rock core samples from gas fields in the northeast of the Netherlands. The rock samples were contained in reactor vessels for 30 days in contact with CO₂ and 100 ppm SO₂ under in-situ conditions (300 bar, 100 °C). The vessels also contained brine with the same composition as in the actual reservoir. Furthermore equilibrium modeling was carried out using PHREEQC software in order to model the experiments on caprock samples.After the experiments the permeability of the reservoir samples had increased by a factor of 1.2–2.2 as a result of dissolution of primary reservoir minerals. Analysis of the associated brine samples before and after the experiments showed that concentrations of K, Si and Al had increased, indicative of silicate mineral dissolution.In the caprock samples, composed of carbonate and anhydrite minerals, permeability changed by a factor of 0.79–23. The increase in permeability is proportional to the amount of carbonate in the caprock. With higher carbonate content in comparison with anhydrite the permeability increase is higher due to the additional carbonate dissolution. This dependency of permeability variations was verified by the modeling study. Hence, caprock with a higher anhydrite content in comparison with carbonate minerals has a lower risk of leakage after co-injection of 100 ppmv SO₂ with CO₂.     

气藏盖储层压力配置类型及与储量丰度的关系

通过研究气藏盖层排替压力与储层压力特征,对其盖储层压力配置类型及与储量丰度关系进行了研究,结论为盖高储低压配置类型最有利于天然气富集,其次是盖高储常压配置类型和盖较高储低压配置类型,其它配置类型较差.通过统计得到:我国46个大中型气田盖储层压力配置类型有4种,以盖高储高压配置类型最多,其次是盖高储弱高压配置类型,再次是盖高储常压配置类型,盖高储低压配置类型最少;我国46个大中型气田中低储量丰度的大中型气田个数最多,其次是高、中储量丰度的大中型气田,特低储量丰度的大中型气田个数最少.通过我国46个大中型气田盖储层压力配置类型与天然气储量丰度之间关系研究发现,盖储层压力配置类型为盖高储常压配置类型和盖高储高压配置类型最有利于形成高、中天然气储量丰度的大中型气田.     

鄂尔多斯盆地西部下古生界风化壳优质储集层发育规律及成因机制: 以桃2区块马家沟组马五1-4亚段为例*

鄂尔多斯盆地下古生界马家沟组顶部遭受长期风化剥蚀,形成了以膏云岩为主的风化壳岩溶储集层。盆地西部包括桃2区块在内的马家沟组马五_1-4亚段以(含)膏云岩、白云岩和灰云岩互层发育为主。借助岩心观察、偏光显微分析和扫描电镜超微分析,识别出多层成层分布的(含)膏云岩;通过对硬石膏、白云石和方解石等矿物的物理和化学性质对比研究,认为(含)膏云岩的膏模孔、扩溶膏模孔及与之伴生的胀缩微裂缝为主要储集空间,孔隙大小具有明显的自限性,受硬石膏结核和石膏晶体大小的制约;岩性((含)膏云岩)和沉积微相(潮上带(含)膏云坪)是储集层形成的先天物质基础和环境条件,并导致(含)膏云岩储集层的层控分布特征;4期溶蚀作用过程中,硬石膏晶体和结核的组构选择性溶蚀和阶段性充填,是储集层形成的关键过程;储集层为层状相控、受岩溶作用影响,但岩溶地貌对储集层分布不再有决定性控制作用。(含)膏云岩发育区分散流的弥散性渗透溶蚀是大洞大缝不发育的主要原因。“层状相控岩溶作用岩性气藏”观点的提出将促使研究区下古生界从“岩溶古地貌气藏”向“相控岩性气藏”勘探的深刻转变。     

Thermo-hydro-mechanical modeling of carbon dioxide injection for enhanced gas-recovery (CO2-EGR): a benchmarking study for code comparison

The objective of this paper was to investigate the THM-coupled responses of the storage formation and caprock, induced by gas production, CO₂-EGR (enhanced gas recovery), and CO₂-storage. A generic 3D planer model (20,000?×?3,000?×?100?m, consisting of 1,200?m overburden, 100?m caprock, 200?m gas reservoir, and 1,500?m base rock) is adopted for the simulation process using the integrated code TOUGH2/EOS7C-FLAC3D and the multi-purpose simulator OpenGeoSys. Both simulators agree that the CO₂-EGR phase under a balanced injection rate (31,500?tons/year) will cause almost no change in the reservoir pressure. The gas recovery rate increases 1.4?% in the 5-year CO₂-EGR phase, and a better EGR effect could be achieved by increasing the distance between injection and production wells (e.g., 5.83?% for 5?km distance, instead of 1.2?km in this study). Under the considered conditions there is no evidence of plastic deformation and both reservoir and caprock behave elastically at all operation stages. The stress path could be predicted analytically and the results show that the isotropic and extensional stress regime will switch to the compressional stress regime, when the pore pressure rises to a specific level. Both simulators agree regarding modification of the reservoir stress state. With further CO₂-injection tension failure in reservoir could occur, but shear failure will never happen under these conditions. Using TOUGH-FLAC, a scenario case is also analyzed with the assumption that the reservoir is naturally fractured. The specific analysis shows that the maximal storage pressure is 13.6?MPa which is determined by the penetration criterion of the caprock.     

油气沿不同时期断裂穿过泥岩盖层渗滤散失的地质条件及其识别方法

为了研究含油气盆地断裂发育区油气分布规律,在确定油气沿活动期和静止期断裂穿过泥岩盖层发生渗滤散失机理的基础上,针对油气沿活动期和静止期断裂穿过泥岩盖层渗滤散失的地质条件及识别方法进行了研究。研究结果表明：油气沿活动期断裂穿过泥岩盖层渗滤散失所需的地质条件是活动期断裂在盖层内上下连接分布,作为油气穿过泥岩盖层的输导通道;油气沿静止期断裂穿过泥岩盖层渗滤散失所需的地质条件是下伏储层油气剩余压力大于断层岩排替压力。通过比较泥岩盖层断接厚度与油气沿活动期断裂穿过泥岩盖层渗滤散失所需最小断接厚度的相对大小和下伏储层剩余压力与断层岩排替压力的相对大小,分别建立了油气是否沿活动期断裂和静止期断裂穿过泥岩盖层渗滤散失的识别方法,并将其应用于渤海湾盆地南堡凹陷南堡5号构造天然气能否通过活动期和静止期NP5 2断裂穿过东二段泥岩盖层渗滤散失的识别。结果表明：在断裂活动期,仅在L2和L8测线处天然气可以沿着NP5 2断裂穿过东二段泥岩盖层渗滤散失,其余测线处(L1、L3、L4、L5、L6、L7、L9)则不能;但是在断裂静止期,天然气不能沿NP5 2断裂穿过东二段泥岩盖层渗滤散失,与目前南堡5号构造东二段泥岩盖层之下已发现的天然气分布相吻合,表明这2种方法分别用于识别油气是否通过静止期断裂和活动期断裂穿过泥岩盖层渗滤散失是可行的。     

辽河盆地东部凹陷天然气盖层评价

辽河盆地东部凹陷为辽河盆地三大凹陷之一，位于辽宁省境内的下辽河平原。本文通过东部凹陷盖层类型，岩石学特征与盖层品质的关系，压实作用对盖层封盖性能的影响及火山岩盖层封盖性能分析，指出东部凹陷虽缺乏区域性盖层，但局部盖层十分发育，其中火山岩是最好的盖层，不同层次的泥岩盖层变化较大，主要形成期为中深层的突变压实阶段和紧密压实阶段，浅层火山岩的发育弥补了泥岩的不足，并根据泥岩盖层与储层的匹配关系研究指出:“东部凹陷浅层是差的盖层匹配好储层，深层则相反”。从泥岩盖层角度出发认为中深层应是大中型气藏形成的有利场所，浅层则是小型气藏发育的有利部位，但本区封盖性能很好的火山岩发育，使其为主的盖层，增加了浅层形成较大型气藏的可能，从而打破了以泥岩盖层为主的纵向天然气分布格局，同时通过东部凹陷不同层位、不同深度层次泥岩盖层突破压力分布特点，结合火山岩分布特征，指出了本区下部勘探方向。     

Reservoir geochemistry of South Pass 61 Field, Gulf of Mexico: compositional heterogeneities reflecting filling history and biodegradation

Cluster analysis of GC data for gasoline and mid-range hydrocarbon ratios from fifty-one South Pass 61 Field oils reveals geochemically similar oil clusters corresponding to geographically coherent groups. Insight into the groupings is obtained from examination of indicators of geochemical processes, e.g., anaerobic biodegradation, aerobic biodegradation and extensive remigration of light ends. Six duplicate samples collected in 1986 and 1992 as well as replicate runs on a single sample showed excellent analytical reproducibility.Subtle but consistent differences in both gasoline and oil-range hydrocarbon maturity indicators are observed between the east, west, and far west flanks of the field, suggesting filling of different segments of the reservoir from different kitchens at slightly different stages of thermal maturity or with slightly different chemical character. The west flank of the salt dome was charged with slightly more thermally mature petroleum than the east flank. The stratigraphically oldest and deepest sand on the far west flank has received the most mature petroleum. Different fluid contacts and GORs are observed in different sands and different fault blocks. The stacked pay geometry of the field and widespread faulting have led to considerable remigration of gas and condensate as observed in other fields in the Gulf of Mexico (Thompson, 1987).Biodegradation varies in severity with depth and reservoir zone, but is frequently overprinted by remigration of light end hydrocarbons. Anaerobic biodegradation by sulfate-reducing bacteria is probably the cause of light to moderate alteration in intermediate depth Pliocene sands which are hydraulically connected to the salt dome (with dissolution of anhydrite from the salt dome providing the sulfate). Widespread late pyrite formation in reservoir sandstones is inferred to represent the ultimate sink for reduced sulfur from sulfate reduction during oil biodegradation. Co-produced water compositions suggest no oxygenated freshwater infusion.     

徐家围子断陷安达凹陷火石岭组天然气成藏条件分析

DS28井的勘探研究表明徐家围子断陷火石岭组具有良好的勘探前景.笔者通过对岩芯地化测试、铸体薄片、孔隙度测试等资料的分析,探究安达凹陷火石岭组天然气的气源条件、储层特征、盖层条件和成藏模式,以期深入认识松辽盆地北部火石岭组天然气富集规律,指出有利勘探区带和勘探方向.研究表明,安达凹陷火石岭组具备天然气藏形成的基本地质条...     

Sealing of fluid pathways in overpressure cells: a case study from the Buntsandstein in the Lower Saxony Basin (NW Germany)

We studied veins in the Triassic Buntsandstein of the Lower Saxony Basin (NW Germany) with the aim of quantifying the evolution of in-situ stress, fluids and material transport. Different generations of veins are observed. The first generation formed in weakly consolidated rocks without a significant increase in fracture permeability and was filled syntectonically with fibrous calcite and blocky to elongate-blocky quartz. The stable isotopic signature (δ¹⁸O and δ¹³C) indicates that the calcite veins precipitated from connate water at temperatures of 55–122°C. The second vein generation was syntectonically filled with blocky anhydrite, which grew in open fractures. Fluid inclusions indicate that the anhydrite veins precipitated at a minimum temperature of 150°C from hypersaline brines. Based on δ³⁴S measurements, the source of the sulphate was found in the underlying Zechstein evaporites. The macro- and microstructures indicate that all veins were formed during subsidence and that the anhydrite veins were formed under conditions of overpressure, generated by inflation rather than non-equilibrium compaction. The large amount of fluids which are formed by the dehydrating gypsum in the underlying Zechstein and are released into the Buntsandstein during progressive burial form a likely source of overpressures and the anhydrite forming fluids.     

断裂输导在我国高效和中效聚集的大-中型气田形成中的作用

基于对我国53个大.中型气田生储盖组合类型及天然气运移输导类型的研究,认为生储盖组合类型决定了断裂是我国大一中型气田天然气运移的主要输导通道.通过这53个大,中型气田天然气聚集效率与其输导通道之间关系的剖析,发现被断裂输导的大一中型气田主要为高效和中效聚集的气田.这主要是由于断裂本身具有较强的输导能力,同时其输导时期与源岩大量排气期匹配关系好.利用断裂输导天然气的输导能力综合评价参数对我国44个大-中型气田断裂输导天然气能力进行了研究,提出我国要形成高效和中效聚集的大-中型气田的条件是：断裂输导天然气速度一般应大于0.47×10^-12m/s.     

热化学硫酸盐还原作用对碳酸盐岩气藏的化学改造——以川东北地区长兴组-飞仙关组气藏为例

目前在川东北地区长兴组—飞仙关组已发现普光、渡口河、铁山坡、罗家寨等多个高含H2S的大、中型气田。通过天然气地球化学特征、流体包裹体盐度和岩心及薄片的镜下详细观察后认为,川东北地区长兴组—飞仙关组的大多数气藏遭受了热化学硫酸盐还原作用(TSR)的化学改造,TSR的改造主要表现在3个方面:1使C2 重烃相对于CH4、12C相对于13C优先被消耗,造成天然气干燥系数变大和碳同位素变重;2由于TSR产生的大量淡水的加入,使气藏的原生地层水被稀释,造成地层水盐度降低;3TSR相关流体(烃类和H2S等)与储层岩石之间的相互作用使储层被溶蚀和硬石膏发生蚀变,造成储层孔隙度增大,从而对改善其物性具有重要意义。     

鸡西含煤沉积盆地特征及早期油气勘探

鸡西盆地位于黑龙江省东部,1985年见天然气显示,有效勘探面积只占盆地面积的50%,而且生油坳陷（沉积坳陷）局部遭到破坏,地质条件复杂,勘探风险大。盆地内主要充填了白垩系及第三系,是一个中、新生代盆地,其中下白垩统分为鸡西群和桦山群,鸡西群是主要含煤地层,也是油气勘探的目的层。下白垩统东荣组含有海湾湖相暗色泥岩,而城子河组与穆棱组沼泽相煤和高碳泥岩发育。老第三系永庆组深湖相暗色泥岩丰富,生油岩类型及纵向分布层位差异受沉积充填序列控制。孔隙型储层物性较低,裂隙型储层具有实际意义。生储盖组合匹配,发现的天然气源于下伏的鸡西群,气层之上的盖层是厚层泥岩与4层凝灰岩。研究表明,鸡西盆地含有较丰富的天然气资源,大部分为煤层气,应以天然气勘探为目标。建议在梨树镇坳陷下白垩统找气,在平阳镇坳陷老第三系找油。     

断裂对盖层封气综合能力破坏程度的研究方法及其应用

为了研究断裂在油气成藏与分布中的作用,在分析盖层封气综合能力及其研究方法的基础上,利用天然气在剩余压力作用下通过盖层向外渗滤散失压力梯度的大小,表征盖层封气综合能力的好坏;依据被断裂破坏前后盖层封气综合能力差值与被断裂破坏前盖层封气综合能力的比值,建立了一套断裂对盖层封气综合能力破坏程度的定量研究方法。以渤海湾盆地南堡凹陷南堡5号构造东二段泥岩盖层为例,对NP5-2断裂对东二段泥岩盖层封气综合能力的破坏程度进行了定量研究。结果表明:南堡5号构造NP5-2断裂对东二段泥岩盖层封气综合能力的破坏程度较高,除L6测线处为弱破坏程度和L1、L5、L8测线处为中等破坏程度外,其余5条测线处均可达到较强和强破坏程度;且NP5-2断裂对东二段泥岩盖层封气综合能力的破坏程度西部强于东部,这与东二段泥岩盖层之下储气层中目前已发现的天然气主要分布在断裂东部相吻合。该方法用于定量研究断裂对盖层封气综合能力破坏程度是可行的。     

断盖配置渗漏油气时期确定方法及其应用

为了客观把握含油气系统中断裂处的油气纵向分布规律,在断盖配置渗漏油气机制及其渗漏油气时期构成研究的基础上,通过厘定断裂开始破坏泥岩盖层封闭时刻、断层岩开始封闭时刻和断裂活动停止时刻,确定断盖配置渗漏时期,并结合源岩排烃史,建立了一套确定断盖配置渗漏油气时期的方法,并将其应用于渤海湾盆地南堡凹陷南堡5号油田,研究F3断裂...     

Numerical simulation of carbon dioxide injection for enhanced gas recovery (CO2-EGR) in Altmark natural gas field

This paper studied the CO₂-EGR in Altmark natural gas field with numerical simulations. The hydro-mechanical coupled simulations were run using a linked simulator TOUGH2MP-FLAC3D. In order to consider the gas mixing process, EOS7C was implemented in TOUGH2MP. A multi-layered 3D model (4.4 km × 2 km × 1 km) which consists of the whole reservoir, caprock and base rock was generated based on a history-matched PETREL model, originally built by GDF SUEZ E&P Deutschland GmbH for Altmark natural gas field. The model is heterogeneous and discretized into 26,015 grid blocks. In the simulation, 100,000 t CO₂ was injected in the reservoir through well S13 within 2 years, while gas was produced from the well S14. Some sensitivity analyses were also carried out. Simulation results show that CO₂ tends to migrate toward the production well S14 along a NW–SE fault. It reached the observation wells S1 and S16 after 2 years, but no breakthrough occurred in the production well. After 2 years of CO₂ injection, the reservoir pressure increased by 2.5 bar, which is beneficial for gas recovery. The largest uplift (1 mm) occurred at the bottom of the caprock. The deformation was small (elastic) and caprock integrity was not affected. With the injection rate doubled the average pressure increased by 5.3 bar. Even then the CO₂ did not reach the production well S14 after 2 years of injection. It could be concluded that the previous flow field was established during the primary gas production history. This former flow field, including CO₂ injection/CH₄ production rate during CO₂-EGR and fault directions and intensity are the most important factors affecting the CO₂ transport.     

鄂尔多斯深盆气

鄂尔多斯盆地内石炭纪—二叠纪煤系含有机质丰富 ,演化程度高 ,不但形成了巨量的天然气 ,而且因储层致密、升降稳定、构造稀少而形成了盆地构造下倾部位天然气的大规模聚集 ,构造上倾部位则大面积含水 ,具有典型“深盆气”的特征。深盆气的主要含气层位为盒 8—本溪组各段 ,而盆地东部和北部可延至盒 5段。煤层是深盆气圈闭中的潜在储集层 ,起着“调节气库”的作用。多期砂体的叠置使深盆气的面积变得巨大 ,钻探成功率高 ,但因储集层的岩性致密 ,使自然产能低。     

鄂尔多斯盆地靖边气田区中奥陶统马家沟组五1-五4亚段古岩溶型储层分布特征及综合评价

鄂尔多斯盆地中部中奥陶统马家沟组最上部的马五1-马五4亚段是靖边气田区主要的产气层之一.按岩性及天然气勘探潜力每个亚段又可划分出2-4个小层,共12个小层.其中最佳产层为马五.12和马五13层,其次有马五11、马五14、马五22和马五41层.储层最主要的岩石类型是含硬石膏结核或含硬石膏柱状晶和结核的粉晶白云岩,其次为含...     

南海高压气田泥岩盖层封闭机制、封气能力及演化过程——以莺歌海盆地X13高压气田为例

近期在南海莺歌海盆地勘探发现了高压大气田和一批含气圈闭,随着勘探的深入,高压领域(高压区、高压层系)天然气规模成藏和气水分布的复杂性日益凸显。利用钻井、地震和分析测试资料,对莺歌海盆地X13高压气田上中新统黄流组一段泥岩盖层的封闭机制、封气能力进行了研究,认为泥岩盖层存在物性封闭和泥岩滞排超压封闭两种封闭机制,并建立了相应的封气能力评价方法。X13高压气田泥岩盖层封气能力形成时间约在6.1Ma;3.6Ma时,X13高压气田构造-岩性圈闭形成,这也是天然气成藏的早期,储层、泥岩盖层为常压,泥岩盖层以物性封闭为主,盖层的排替压力大于储层剩余压力,因而具备了封气能力;1.8~0Ma,是天然气晚期成藏时期,储层、盖层已发育超压,泥岩盖层既存在物性封闭,也存在泥岩滞排超压封闭,泥岩盖层的排替压力与滞排超压之和大于超压储层的剩余压力,其中滞排超压发挥了主要的封气作用。较之天然气成藏早期,成藏晚期的盖层泥岩具备更好的封气能力。提出了"中部滞排欠压实-底部畅排压实型盖层—大型储集体组合"的圈闭(带)是高压领域天然气成藏富集区,这一认识对南海高压领域天然气勘探具有指导意义。     

我国吉林油田大情字井区块CO2地下埋存试验区地质埋存格架

目前,我国在CO2地质埋存的试验研究才刚刚开始,其研究方法与研究思路需要不断探索。本文立足于吉林油田大情字井区块,从储层埋存潜力、埋存体稳定性及水文地质条件三个方面对试验区实施CO2地质埋存工程进行评价。通过对注CO2层段的储层砂体有效厚度、空间展布范围、储层物性及储层微观结构,以及在此基础上,对各砂体横向和垂向上的连续性、砂体间的连通性等等方面的分析和评价,试验区具备一定的埋存潜力,其有效储层厚度平均为273m;同时对试验区盖层的封盖性、断裂的稳定性及井筒的密封性三方面的评价,建立试验区埋存体稳定性评价体系。研究表明,试验区具备厚层泥岩封盖层、盖层内断裂不发育且比较单一以及储层内广泛发育隔夹层,可以有效地对CO2的运移或渗漏实施封盖和遮挡;另外,结合试验区矿化度、水化学成分的研究表明,试验区与邻近区域存在明显的矿化度分带特点、水化学成分也相对较单一以及含水层和隔水层均较发育。在一定程度上说明,试验区目的层段具有相对独立的地下水水体环境,比较有利于适合注入CO2,并进行地质埋存。通过这三方面的研究,建立大情字井区块适合CO2地质埋存的埋存格架,为该区实现CO2长期有效安全埋存奠定基础。     

地下储气库地应力模拟研究与地质完整性评估——以相国寺为例

为保障国家调峰保供需求,目前相国寺地下储气库(以下简称储气库)提出并正在进行扩压增量工程,为有效指导储气库运行上限压力优化,同时确保储气库长期安全运行,亟需对相国寺储气库开展地质体完整性评估。综合地质、地震、测井、动态监测资料以及各类室内岩芯实验数据,建立相国寺储气库三维静态及四维地质力学模型,分析了储气库地质体地质力学特征,分别对不同气藏孔隙压力特征下的盖层、底托层、断层稳定性进行应力应变模拟及评估。结果表明：梁山组盖层以及韩家店组底托层在储气库运行过程中产生的地层形变量小;5条控藏断层在储气库前期运行及现今注采条件下没有断层活化风险;模拟储气库注入压力高于原始气藏压力6 MPa时,储气库地质体完整性存在失稳风险。研究成果精细定量化评估了储气库在动态应力场影响下的运行安全,对优化储气库运行方案具有重要的指导意义。