Shale Hydrocarbon Development Based on Drill Cuttings &TOC Analysis: Case Study of Brownshale Drill Cuttings of Well BS-03, Pematang Formation, Bengkalis Trough, Central Sumatra Basin

Brownshale is a lithology unit in the middle of the Pematang Formation consisting of brown to black shale that is deposited in the lacustrine environment. Brownshale from the results of previous studies stated as the main source rock in the Central Sumatra Basin, which is spread over several troughs, namely Balam, Aman, Rangau, Kiri, and Bengkalis Troughs, where Bengkalis Trough is the most extensive Trough. In the shale hydrocarbon prospecting analysis, Brownshale from previous researchers concluded that it had good prospects, based on several parameters including: TOC values with poor to very good quality. Brownshale formation is a type of kerogene as kerogen type of II/III, brittleness index greater than 0.48, and rock compressive strength below 10,000 Psi. One method in the development phase of shale hydrocarbon is to determine the fracable sweetspot window using drill cuttings and TOC, because there is no core data available. Based on the results of the well log analysis of well BS-03, it is obtained information that the Brownshale formation has a thickness of 1028 feet with intercalation laminated shale/sand section, so the mineral content varies greatly. From the ternary diagram of XRD (bulk analysis) results of drill cuttings of Brownshale formation of well BS-03, it can be seen that mineral distribution of Quartz-Clay-Calcite (Q-C-C) is spread between zone 1 to zone 3, namely: Dominant Quartz - Minor Clay & Carbonate (Zone 1: Brittle Quartz Rich), Dominant Carbonate - Quartz & Minor Clay (Zone 2: Brittle Carbonate Rich), and Quartz & Carbonate Balance - Clay minor (Zone 3: Ductile, hard to frac). This shows that not all Brownshale formation intervals are easy to frac (high fracability). From the XRD result, percentage of mineral content (bulk analysis) of Brownshale drill cuttings, there is an interesting phenomenon, i.e. the presence of sillimanite and kaliophilite minerals significantly starting at a depth of 10,780 ft and below, where both minerals have tenacity: brittle, and also from the results of the MBT analysis seen an interesting phenomenon, i.e. at a depth interval of about 10,780 ft the value of CEC drops below 3 meq/100 grams, and can be categorized as the brittle shale. Referring to the presence of sillimanite and kaliophilite minerals, as well as low MBT values, then at intervals of 10,780 ft below, it can be seen that at the bottom of the depth interval as a fracable sweetspot window, and at the upper depth interval of the Brownshale formation, it is believed to be a fracture barrier.

Correlation of Sillimanite &Kaliophilite Minerals, TOC, Ro, and MBT from Drill Cutting of Well BS-03 in the Development of Shale Hydrocarbon, Brownshale Formation, Bengkalis Trough, Central Sumatra Basin, Indonesia

Sillimanite is a brittle mineral as a metamorphic mineral product which is generally derived from clay, along with an increase in pressure and high temperature (600°C - 900°C), and kaliophilite is also a brittle mineral as a potassium bearing in the sand-shale series, which contributes to the clay diagenesis process. In the development of shale hydrocarbon in the Brownshale formation in the Bengkalis Trough, Central Sumatra Basin, using the correlation of the XRD (bulk and clay oriented), TOC, Ro, and MBT analysis results from the drill cuttings of well BS-03, so that the fracable zone interval can be determined. From this correlation, it shows that the presence of sillimanite and kaliophilite minerals as minor minerals greatly affects the changes in shale character and hydrocarbon generation, where at depth intervals of 10,780 ft downward (sand series-shale) there is an interesting phenomenon, i.e. low MBT, low TOC, and high Ro, so it is believed that the depth interval of 10,780 ft downward is a fracable zone interval (brittle shale) which is a good candidate for hydraulic fracking planning, while the upper depth interval is a fracture barrier.

Correction Method of Light Hydrocarbons Losing and Heavy Hydrocarbon Handling for Residual Hydrocarbon (S_1) from Shale

In China, hot researches on shale oil were raised by the important breakthrough of shale oil in America. Obviously, the first important issue is the actual shale oil resource potential of China, and the selection of the key appraisement parameter is vital to the shale oil resource amount. Among the appraisement parameters, the oil content parameter（S1） is the key one, but the evaluation result is generally lower because of light hydrocarbon losing and heavy hydrocarbon handling. And the more important thing is that the light hydrocarbon with small molecular weight is more recoverable, and therefore its amount is important to the total shale oil yields. Based on pyrolysis experiments and the kinetic model of hydrocarbon generation, correction factors and a model of light hydrocarbon losing and heavy hydrocarbon handling were established. The results show that the correction factor of heavy hydrocarbon handling is 3.2, and that of light hydrocarbon losing is controlled by kerogen type, maturity and hydrocarbon generation environment（closed or open）.

Kinetic simulation of hydrocarbon generation and its application to in-situ conversion of shale oil

The kinetic parameters of hydrocarbon generation are determined through experimental simulation and mathematical calculation using four typical samples selected from the Cretaceous Nenjiang Formation in the northwest of Songliao Basin,Chang 7 Member of Triassic Yanchang Formation in the southwest of Ordos Basin,Paleogene in the southwest of Qaidam Basin,and Lucaogou Formation of Jimusar Sag in the east of Junggar Basin.The results show that activation energy of hydrocarbon generation of organic matter is closely related to maturity and mainly ranges between 197 kJ/mol and 227 kJ/mol.On this basis,the temperature required for organic matter in shale to convert into oil was calculated.The ideal heating temperature is between 270℃and 300℃,and the conversation rate can reach 90%after 50-300 days of heating at constant temperature.When the temperature rises at a constant rate,the temperature corresponding to the major hydrocarbon generation period ranges from 225 to 350℃at the temperature rise rate of 1-150℃/month.In order to obtain higher economic benefits,it is suggested to adopt higher temperature rise rate(60-150℃/month).The more reliable kinetic parameters obtained can provide a basis for designing more reasonable scheme of in-situ heating conversion.

Connotation and strategic role of in-situ conversion processing of shale oil underground in the onshore China

In-situ conversion processing (ICP) of shale oil underground at the depth ranging from 300 m to 3 000 m is a physical and chemical process caused by using horizontal drilling and electric heating technology, which converts heavy oil, bitumen and various organic matter into light oil and gas in a large scale, which can be called"underground refinery". ICP has several advantages as in CO2capture, recoverable resource potential and the quality of hydrocarbon output. Based on the geothermal evolution mechanism of organic materials established by Tissot et al., this study reveals that in the nonmarine organic-rich shale sequence, the amount of liquid hydrocarbon maintaining in the shale is as high as 25%in the liquid hydrocarbon window stage (R o less than 1.0%), and the unconverted organic materials (low mature-immature organic materials) in the shale interval can reach 40%to 100%. The conditions of organic-rich shale suitable for underground in-situ conversion of shale oil should be satisfied in the following aspects, TOC higher than 6%, R o ranging between 0.5%and 1%, concentrated thickness of organic-rich shale greater than 15 meters, burial depth less than 3 000 m, covering area bigger than 50 km2, good sealing condition in both up-and down-contacting sequences and water content smaller than 5%, etc. The shale oil resource in China’s onshore region is huge. It is estimated with this paper that the technical recoverable resource reaches 70-90 billion tons of oil and 60-65 trillion cubic meters of gas. The ICP of shale oil underground is believed to be a fairway to find big oil in the source kitchen in the near future. And it is also believed to be a milestone to keep China long-term stability of oil and gas sufficient supply by putting ICP of shale oil underground into real practice in the future.

Geochemical Assessments and Potential Energy Sources Evaluations Based on Oil Shale and Geothermal Resource in Wadi Al-Shallala—North Jordan

Oil shale deposit is considered as one of the fossil fuel sources in Jordan. Despite that, the needs of renewable energy resources become a must in Jordan. Wadi Al-Shallala oil shale is investigated in this work for geochemical, petrographic features and hydrocarbon potential as a conventional energy resource. Various petrographic and geochemical techniques were applied. Oil shale resource potential is evaluated for cooling and heating Sal village houses. Geothermal heat pumps, as renewable energy resource in the study area, were simulated for comparison purposes. Results show that Calcite is the main mineral component of oil shale. Magnesite, Ferrisilicate and Zaherite are exhibited in the studied samples. Other trace elements of Zinc, Cobalt and Molybdenum were presented, too. Calcium oxide of 41.01% and Silicon oxide of 12.4% are the main oxides reflected in this oil shale. Petrographic features of the analyzed oil shale found that the primary mineral constituent is micritic calcite, while the secondary minerals include carbonate mud and opaque minerals. Furthermore, it’s found that total organic carbon averages 3.33% while the total carbon content averages 20.6%. ModerateTOCvalues suggest that Wadi Al-Shallala oil shale has a good source rock potential. Even though nitrogen and sulfur are of low contents in Wadi Al-Shallala oil shale, direct combustion of the reserve for electricity generating will increase CO2 emissions by 2.71 Million m3. Two systems were simulated to cover Sal village cooling and heating demands. The conventional system is compared with geothermal heat pumps. Geothermal heat pumps are found to save 60% of electricity consumption in heating and 50% in cooling systems. The environmental benefits for geothermal system implementation will be a reduction in energy consumption as electricity. The savings in fuel oil will be about 9.35 Million barrels. While the reduction of CO2 emissions will drop to 1.5 Million m3. Results suggest that geothermal heat pumps are the best for satisfying cooling and heating needs in Sal village near Wadi Al-Shallala.

Modes of Shale-Gas Enrichment Controlled by Tectonic Evolution

The typical characteristics of shale gas and the enrichment differences show that some shale gases are insufficiently explained by the existing continuous enrichment mode. These shale gases include the Wufeng–Longmaxi shale gas in the Jiaoshiba and Youyang Blocks, the Lewis shale gas in the San Juan Basin. Further analysis reveals three static subsystems（hydrocarbon source rock, gas reservoirs and seal formations） and four dynamic subsystems（tectonic evolution, sedimentary sequence, diagenetic evolution and hydrocarbon-generation history） in shale-gas enrichment systems. Tectonic evolution drives the dynamic operation of the whole shale-gas enrichment system. The shale-gas enrichment modes controlled by tectonic evolution are classifiable into three groups and six subgroups. Group I modes are characterized by tectonically controlled hydrocarbon source rock, and include continuous in-situ biogenic shale gas（Ⅰ_1） and continuous in-situ thermogenic shale gas（Ⅰ_2）. Group Ⅱ modes are characterized by tectonically controlled gas reservoirs, and include anticline-controlled reservoir enrichment（Ⅱ_1） and fracture-controlled reservoir enrichment（Ⅱ_2）. Group Ⅲ modes possess tectonically controlled seal formations, and include faulted leakage enrichment（Ⅲ_1） and eroded residual enrichment（Ⅲ_2）. In terms of quantity and exploitation potential, Ⅰ_1 and Ⅰ_2 are the best shale-gas enrichment modes, followed by Ⅱ_1 and Ⅱ_2. The least effective modes are Ⅲ_1 and Ⅲ_2. The categorization provides a different perspective for deep shale-gas exploration.

Organic Geochemical Evaluation of Shale Units of Bokh Formation, Ogaden Basin, Ethiopia

Shale sample from Bokh Formation, Ogaden basin, Ethiopia was assessed for their petroleum potential by Rock-Eval pyrolysis. The Total Organic Carbon (TOC) values range from 0.76 to 0.86 wt%. These values exceed the minimum value of 0.5 wt% required for potential petroleum source rocks. The genetic potential (GP) and hydrogen index (HI) values range from 0.09 to 0.5 mg/g and 8 - 32 mgHC/gTOC, respectively. These values are generally lower than the minimal 2 mg/g GP and 200 mgHC/g HI required for a potential source rock. Several plots from the Rock-Eval pyrolysis data classify the samples as type IV kerogen with no potential to generate hydrocarbons. The Tmax and Production Index (PI) values range from 388°C to 453°C and 0.28 to 0.46, respectively. These values indicate that the shales are thermally matured. These results show that the shales from the Bokh Formation in Ogaden basin have no potential to generate hydrocarbons mainly crude oil, but are thermally matured and may generate natural gas.

南襄盆地泌阳凹陷古近系核桃园组页岩含油性及烃类赋存特征

南襄盆地泌阳凹陷古近系核桃园组发育优质湖相页岩层系,页岩油资源潜力巨大。前人针对该层系页岩含油性及烃类赋存状态的研究相对薄弱,可能是制约泌阳凹陷页岩油勘探突破的重要因素之一。以泌阳凹陷南部Y1井核三段Ⅲ亚段页岩为研究对象,通过岩石热解、多温阶热解、X射线衍射等地球化学分析技术,系统开展了页岩含油性、烃类赋存特征及影响因素研究。研究结果显示:核三段Ⅲ亚段页岩岩相组合主要包括长英质页岩相、云灰质页岩相和混合质页岩相,纹层结构发育。烃源岩类型整体处于好—优质范围,热演化程度处于生油阶段。有机显微组分以腐泥型为主,有机质类型为Ⅰ—Ⅱ1型。页岩含油性随埋深增大呈递增趋势,烃类赋存特征由中上部以吸附烃为主,过渡至下部以游离烃为主。碎屑矿物及有机碳含量是控制游离烃和吸附烃含量的主要因素。总体认为,核桃园组下部页岩含油饱和度指数整体高于100 mg/g,游离烃含量平均高于3 mg/g,具备较好的页岩油勘探开发前景。

泸州地区五峰组——龙马溪组页岩气成藏特征

为寻找四川盆地泸州地区五峰组—龙马溪组页岩气有利区,在开展流体包裹体检测、页岩微观孔隙观测、气泡变孔模拟等研究基础上,查明了泸州地区构造埋藏过程和生烃热演化过程,总结了泸州地区页岩气成藏特征和成藏规律。研究结果表明:泸州地区五峰组—龙马溪组富有机质页岩厚度大,在二叠纪—早三叠世生油,经历了中三叠世和燕山运动期—喜马拉雅运动期2次构造抬升,中三叠世抬升幅度有限,未导致大规模烃散失,燕山运动期—喜马拉雅运动期构造抬升晚于川东南且幅度小,利于页岩气保存;泸州地区五峰组—龙马溪组页岩有机孔发育,是由于中三叠世隆升时间短,强度小,未发生大规模排烃,大量液态烃保留在储集层中,有利于后期有机孔的大量形成,同时在晚三叠世—中白垩世,地层深埋发生液态烃裂解产气,地层广泛超压,有利于有机孔的后期保存;泸州地区三叠纪隆升虽然时间短、强度小,但是从模拟实验结果来看,可以导致原油稠化和气孔形成,对页岩气富集成藏有利。因此,发生在印支运动期的泸州地区的隆升造成原油稠化,有利于页岩气富集成藏;泸州地区地层抬升时间晚,页岩气散失时间短,低角度层理缝发育,而纵向裂缝少,均有利于形成超压页岩气富集区。提出的泸州地区五峰组—龙马溪组页岩富集成藏规律,对于指导其他同类型油气勘探具有借鉴意义。

Preliminary Study on PAHs Distribution in High-grade Oil Shale and Its Spontaneous Combustion Product in Fushun,Liaoning Province

Spontaneous combustion of oil shale is very common as a result of long-time exposure to the air in the Fushun West Open-Pit Mine and West Dump. The PAHs in the high-grade off shale and its spontaneous combustion product were analyzed semiquantitatively by GC-MS in order to investigate their distribution in different states and their potential negative effects on the environment. Totally 57 and 60 PAHs and their alkyl homologues were identified in the two analyzed samples, among which the alkyl derivatives were predominant, taking up to about 65% in the total PAHs. Those low-molecular mass PAHs （3- or 4-ring） were the main compounds in the two samples. Ten of sixteen USEPA priority pollutant PAHs were detected in two samples, of which phenanthrene was the richest whose contents were 6.93% and 15.03%. Based on comparison of analysis results, the amount and contents of PAHs, except for triaromatic steroid group, were higher in the burning oil shale. So it can be determined that the effects caused by spontaneous combustion of oil shale would be more serious and that the effects of the Fushun oil shale and its spontaneous combustion on the environment should not be ignored in the future work.

国内外油页岩工业发展现状

油页岩可作为锅炉燃料直接燃烧产生蒸汽发电,也可经热解后分解生成页岩油、页岩半焦和类似天然气的干馏气,是石油的重要补充能源,开发前景广阔,对世界能源结构的改变具有重要战略意义。梳理世界主要油页岩国家油页岩资源特点、加工利用技术和开发利用现状,世界各国对油页岩的勘探、开采和干馏技术不断革新提升,包括爱沙尼亚、巴西、美国在内的许多国家已经拥有了较先进的油页岩处理技术,对油页岩进行合理开采并进行产业化利用。目前,中国在抚顺、新疆、甘肃等地加工利用油页岩,抚顺页岩油年产量最大。与世界主要油页岩国家相比,中国油页岩开发利用程度总体较低,新技术开发利用不够成熟,尚未形成以油页岩为基础的完整产业链,未来发展还需要更多相关国家政策支持,进一步加大油页岩的科研投入,研究开发适应中国特点的新型技术,不断提高油页岩的工业利用水平和资源化利用水平,在提高处理量、产油率的同时减少生态污染,坚持走新型工业化道路。

Hydrocarbon Generation and Expulsion of the Upper Triassic T3x5Source Rocks in the Western Sichuan Depression: Assessment for Unconventional Natural Gas

Tight-sand gas in the Jurassic and shale gas within the fifth member of Xujiahe Formation （T3xs） in the Western Sichuan Basin （WSD） are currently regarded as the most prolific emerging unconventional gas plays in China. This study conducted a conventional evaluation of T3x5 source rocks in the WSD, and investigated their hydrocarbon generation and expulsion characteristics, including intensity, efficiency and amount. The results show that, the T3x5 source rocks are thick （generally 〉200 m）, and have a high total organic content （TOC）, ranging from 2.5 to 4.5 wt%. It is thus indivative of a great hydrocarbon generation potential when they underwent high thermal evolution （Ro〉1.2%） in the area. In addition, an improved method of hydrocarbon generation potential is applied, indicating that the source rocks reached a hydrocarbon expulsion threshold with vitrinite reflectance （Ro） reaching 1.06%. and that the comprehensive hydrocarbon expulsion efficiency is about 60%. The amount of hydrocarbon generation and expulsion from Tax5 source rocks is 3.14x10^10 t and 1.86x10^10 t, respectively, with a residual amount of 1.28x10^10t within them. Continuous-type tight-sand gas is predicted to have developed in the Jurassic in the Chengdu Sag of the WSD because of the good source-reservoir configuration; the Jurassic sandstone reservoirs are tight, and the gas expelled from the T3xs source rocks migrates for very short distances vertically and horizontally. The amount of gas accumulation in the Jurassic reservoirs derived from T3x5 source rocks is up to 9.3x10s t. Geological resources of shale gas are up to 1.05x10TM t. Small differences between the amounts calculated by the volumetric method and those obtained by hydrocarbon generation potential method may be due to other gas accumulations present within interbedded sands associated with gas shales.

川中大安寨段页岩排烃效率及其勘探启示

烃源岩的排烃效率是油气资源评价中的重要参数,排烃效率的研究既可以指导资源评价,又可以作为验证资源评价结果可靠性的重要科学手段。基于目前生烃潜力法的缺陷,提出了改进的生烃潜力法,并利用此方法求取了四川盆地中部侏罗系大安寨段页岩的排烃效率。研究结果表明,当前地质条件下,大安寨段页岩的排烃效率分布于0∼62.6%。随着有机质成熟度(R_(o))的增加,排烃效率逐渐上升,含油饱和度指数先增加后降低。R_(o)处于0.95%∼1.72%,含油饱和度指数大于100 mg/g,页岩层系的可动烃含量较高。岩相组合对排烃效率具有明显的影响,在纵向上有页岩向介壳灰岩排烃的趋势,相较于纯页岩储层而言,互层型组合层间缝发育,有利于页岩油流动和产出。综合认为,R_(o)>1.25%的大一亚段下部互层型组合是大安寨段页岩油的重点勘探目标。该成果可为川中侏罗系大安寨段页岩油的勘探开发提供理论指导。

西加拿大盆地都沃内(Duvernay)海相页岩油气富集机制研究

西加拿大盆地上泥盆统Duvernay页岩是最大海侵期形成的一套页岩油气富集与生产层系。为明确Duvernay页岩油气富集控制因素,在Duvernay页岩地质背景分析的基础上,运用岩心、测井、薄片、扫描电镜、3D孔隙重建信息及有机地化资料,对有机质富集的沉积因素、流体分布、储层质量及影响因素进行了分析,认为Duvernay页岩油气富集主要受盆内成因的硅质页岩沉积环境、有机质热演化、页岩储层质量及稳定构造背景的共同控制。研究发现,Duvernay组为晚泥盆世的深水陆棚环境,岩性以泥灰岩、灰泥岩和泥页岩为主,可识别出10种岩石相,其中硅质页岩最为发育;Duvernay页岩中主要发育Ⅱ、Ⅲ型海相有机质,有机质热演化程度中等,处于凝析气-湿气阶段,因此凝析油含量高;油气主要富集在黏土级矿物形成的富含有机孔的硅质页岩中,孔隙类型以有机质孔和粒内孔为主,有效孔隙度占比高,连通孔隙非常发育且横向连续分布,并具有垂向上相互连通的特征;成岩作用改善了页岩储层物性,天然裂缝提高了页岩储层的渗透率,而稳定的构造发育特征是Duvernay页岩油能够较好地保存至今的关键。

陆相中高成熟页岩油“组分流动”条件及其在提高页岩油产量中的作用

基于中国陆相页岩油区重点试采井的生产曲线、生产制度、烃产物数量和产出烃构成随时间的变化等资料,开展页岩油精细馏分切割和页岩油组成变化对宏观流动性影响的试验以及分子动力学数值模拟,提出页岩油“组分流动”概念,并对组分流动的形成机理与条件进行探讨。研究表明:(1)在地下页岩微纳米孔隙中,轻烃、中质烃和重烃会按相似相溶原理发生混相,使重烃等难流动组分以分子聚集体方式“悬浮”在轻烃和中质烃溶剂中,从而显著降低其黏度并增加流动性和流动量;(2)小分子芳烃是组分流动发生的载体,气态烃和轻烃含量越高,越利于抑制胶质和沥青等重组分形成尺寸更大的聚集体,并增加其塑性变形能力,组分流动效果越好;(3)较高的地层温度可降低蜡质等重烃组分黏度,提高其流动性;(4)保存条件、地层能量和生产制度对控制轻烃组分含量、流出速度和形成稳定的“组分流动”都有重要作用,是页岩油多组分烃形成最优配伍和最大流动量的重要影响因素。地下页岩油“组分流动”概念的提出对于提高页岩油单井产量和累计采出量具有重要意义。

Development and exploration practice of the concept of hydrocarbon accumulation in rifted-basin troughs: A case study of Paleogene Kongdian Formation in Cangdong sag, Bohai Bay Basin

Based on the merged 3 D seismic data, well logging, formation testing, analysis and testing data, the structural evolution, sedimentary reservoirs, thermal evolution of source rocks were investigated of Paleogene Kongdian Formation in the trough area of Cangdong sag, Bohai Bay Basin. A conventional-unconventional hydrocarbon accumulation pattern in the trough area of rifted basin was revealed. The reservoir forming elements in the trough area of Cangdong sag have a zonation feature in terms of reservoirs and source rocks. There are two types of reservoir forming models, primary trough and reformed trough. The formation and evolution of trough controlled the orderly distribution of conventional oil to unconventional oil in the trough. Particularly, structural reservoirs occur in the upper part of the trough, stratigraphic-lithologic reservoirs are likely to form in the delta front deposits at the outer ring of trough, the middle ring transitional belt is the favorable site for tight oil reservoirs, while the fine grain deposits zone in the inner ring is shale oil and gas exploration area. The study has pointed out the new domains and directions for searching reserves in the secondary exploration of mature oilfields.

松辽盆地北部青山口组富烃页岩形成环境与成因

通过古地温、古地貌、沉积环境定量恢复及地质事件综合研究,分析青山口组富烃页岩形成环境及成因。结果表明,松辽盆地青山口组富烃页岩R_(o)介于0.75%~1.60%,游离烃含量高,介于(4~12)mg/g,形成于古地温梯度(50~70)℃/km的高温热盆背景;在拉伸大地动力学及热沉降背景下形成了正断层密集断裂带控制的页岩层系,两凹一凸的古地貌为页岩形成演化提供富集场所;湖相温湿气候及岩浆热液为藻类繁殖成为厚层富烃页岩发育奠定物质基础;缺氧的半深湖—深湖还原—强还原环境有利于有机质埋藏。综合分析表明,构造、湖相沉积与古地温耦合作用奠定了富烃页岩的构造背景和热动力条件,温湿气候、缺氧环境及火山热液带来的营养物质是富烃页岩形成的重要原因。

古龙页岩油注CO_(2)/烃类气相态特征及多周期作用机制

基于PVT实验和多周期注CO_(2)/烃类气采油物理模拟实验,结合相态模拟计算揭示古龙页岩油注气前后的高压物性和流体类型演化规律,评价多周期注气作用下的原油采出效果,分析多组分间的抽提传质机理。实验结果表明:古龙页岩油属于轻质弱挥发性油藏,当压力降低至泡点压力以下时,原油的黏度和密度快速增大,原油物性急剧变差。因此,对于成熟度较高的页岩油,利用注气补充地层能量并维持良好的原油物性是提高采收率的关键,且注CO_(2)对原油的膨胀、降黏效果均优于注烃类气。此外,注CO_(2)/烃类气可使古龙页岩油由弱挥发性油藏向挥发性油藏转变,先注烃类气再注CO_(2)使得古龙页岩油呈现出由挥发性油藏进一步向凝析气藏过渡的趋势。古龙页岩油脱气后的溶解气驱效果更优,产出油相呈现连续的泡沫油状态。注CO_(2)/烃类气可为地层原油补充溶解气和弹性能量,注CO_(2)对原油中间烃组分(C_(5)—C_(10))和重烃组分(C_(11)+)的抽提效果均较好,注烃类气对原油中间烃组分的抽提效果更好。