鄂尔多斯盆地晚古生代以来构造-沉积演化与致密砂岩气成藏

鄂尔多斯盆地上古生界主要发育致密砂岩气藏,已发现地质储量超过5万亿m3,勘探潜力大。文中通过盆地构造演化史分析,结合包裹体测温、锆石U Pb定年、自生伊利石K Ar测年等分析方法,明确了晚古生代以来构造演化对上古生界致密砂岩气藏的控制作用。研究表明：石炭纪-二叠纪沉积古地形平缓,构造沉降缓慢,形成了大面积分布的煤系烃源岩和砂岩储层;三叠纪-中侏罗世快速沉降,压实作用及硅质胶结作用明显,水岩作用强,致密砂岩储层形成;晚侏罗世-早白垩世构造活动强烈,伴随构造热事件的发生,天然气大量生成并运聚成藏,致密气藏形成;早白垩世末-现今地层抬升剥蚀,天然气散失,低压气藏形成。     

鄂尔多斯盆地东南部气田上古生界致密砂岩气藏气源对比

本文通过碳同位素数据比对、常规天然气组分分析,结合区域地质背景,对鄂尔多斯盆地东南部气田的气源进行了研究.结果表明:鄂尔多斯盆地东南部气田的主力烃源岩为煤层,含气层位出现碳同位素倒转现象,山西组山2段和本溪组主要为煤型气中混入少量油型气,而山西组山1段和石盒子组盒8段则是成藏期经历了多期充注所导致;CH4、CO2和iC...     

陕北斜坡上古生界构造裂缝及其天然气成藏意义

鄂尔多斯盆地陕北斜坡上古生界气藏发育多套储层,中上部储层（石盒子组及石千峰组）与烃源岩（山西组下部及本溪组煤系地层）之间发育280~350 m致密砂泥岩隔层,由于盆地断裂构造不发育,天然气运移通道及成藏模式成为该区气藏研究的焦点。在岩心观察、微裂缝研究、测井解释、岩心孔隙度-渗透率实验研究的基础上,结合成岩作用及裂缝形成时间分析,对研究区上古生界隔层裂缝分布与中上部气藏之间的匹配关系进行了系统研究。结果表明:研究区上古生界主要发育剪性裂缝,裂缝形成于晚侏罗世－早白垩世,裂缝的形成在改善储层渗透性的同时,为天然气的纵向运移提供了必要的运移通道。综合分析认为：研究区上古生界隔层裂缝与中上部气藏在时空上具有良好的耦合关系,形成了基于裂缝运移及砂岩储存的石盒子组与石千峰组“岩性-裂缝型”气藏。     

苏里格低渗砂岩大气田天然气充注运移及成藏特征

苏里格气田位于鄂尔多斯盆地伊陕斜坡西北部,属于典型的低渗砂岩大气田.苏里格气田上古生界天然气组分和碳同位素组成特征变化较小,反映其来源和成藏过程的一致性.基于对成藏地质背景、储层物性、天然气地球化学特征、烃源岩成熟度、甲烷碳同位素动力学的综合分析,认为苏里格气田天然气主要为近源充注、近距离运移和聚集,为石炭系一二叠系煤系烃源岩生成的累积聚气.天然气运移输导体系主要包括砂体一孔隙、微裂缝及小断层等,由孔隙和裂缝构成的网状输导体系在成藏过程中起了重要作用,表现为动力圈闭成藏.苏里格气田形成过程经历了早侏罗世末期、晚侏罗世至早白垩世末期、早白垩世末期至今3个演化阶段,存在下生上储和自生自储两种成藏方式.     

鄂尔多斯盆地上古生界天然气藏类型辨析

针对鄂尔多斯盆地上古生界天然气藏是否为深盆气藏的问题,从成藏条件、成藏期次和气水分布特征等方面与典型的加拿大阿尔伯达深盆气藏进行综合对比。研究结果表明鄂尔多斯盆地上古生界气藏烃源岩分布广泛、生气中心不明显、生气速率较低、持续供气条件较差且供气分散,难以形成满足深盆气藏气驱水的动力;储层物性差、非均质性强、展布方向与构造走向一致且上倾方向为物性较差的致密层,不具备深盆气藏储层向上倾方向物性变好的条件;源储配置样式为"自生自储"式和"垂向叠置"式,由于砂体规模小、分布不连续,源储接触局限,不具备深盆气藏源储大面积接触的特征;天然气发生3期成藏,在盆地埋藏期与抬升期均可成藏,成藏时间较早,后期气藏调整改造强烈,不具备深盆气藏的保存条件。气水分布主要受储层物性和区域构造控制,分布复杂、分异不明显,没有气驱水形成的"气水倒置"界面。成藏特征综合对比分析表明鄂尔多斯盆地上古生界气藏并非深盆气藏,应为主要由储层物性控制的岩性气藏,该区油气勘探应以优质储层研究为重点。     

Coupling relationship between reservoir diagenesis and hydrocarbon accumulation in Lower Cretaceous Yingcheng Formation of Dongling,Changling fault depression,Songliao Basin,Northeast China

The Lower Cretaceous Yingcheng Formation in the southern Songliao Basin is the typical tight oil sandstone in China. In order to better predict the petrophysical properties of the tight sandstone reservoirs in the Lower Cretaceous Yingcheng Formation, Songliao Basin, Northeast China, the diagenesis and porosity evolution was investigated using a suite of petrographic and geochemical techniques including thin section analysis, scanning electron microscopy, mercury intrusion and fluid inclusion analysis, on a set of selected tight sandstone samples. Combined with the histories of burial evolution, organic matter thermal evolution and hydrocarbon charge, the matching relationship between reservoir porosity evolution and hydrocarbon accumulation history is analyzed. The result showed that the tight sandstone reservoirs characterized of being controlled by deposition, predominated by compaction, improved by dissolution and enhanced by cementation. The hydrocarbon accumulation period was investigated using a suite of hydrocarbon generation and expulsion history, microfluorescence determination and temperature measurement technology. According to the homogenization temperature of the inclusions and the history of burial evolution, Yingcheng Formation has mainly two phases hydrocarbon accumulation. The first phase of oil and gas is charged before the reservoir is tightened, the oil and gas generated by Shahezi source rocks enter the sand body of Yingcheng Formation, influenced by the carrying capability of sand conducting layer, oil and gas is mainly conducted by the better properties and higher connectivity sand body and enriched in the east, which belongs to the type of densification after hydrocarbon accumulation. The second phase of oil and gas charge after densification, which belongs to the type of densification before the hydrocarbon accumulation.     

苏里格西部致密砂岩气藏储层成岩作用特征及孔隙度定量演化

为了探究鄂尔多斯盆地苏里格西部地区储层致密成因及孔隙演化规律,本文基于铸体薄片、电镜分析和高压压汞等室内测试,通过建立理论计算模型,对其苏48区储层的孔隙演化进行定性分析与量化表征。分析结果表明,区内盒8段储层岩性主要为石英砂岩和岩屑石英砂岩,储层成岩阶段处于早成岩和中成岩阶段,部分达到晚成岩期,成岩作用顺序依次为:压实-硅质胶结-绿泥石胶结-黏土矿物胶结-溶蚀溶解-碳酸盐胶结;量化结果显示:压实作用和胶结作用是造成储层孔隙度下降的主要因素,其中压实作用使得原始孔隙度下降22%,胶结作用使其下降9.81%,溶蚀作用对储集空间有所改善,增加了3.88%的孔隙,最终形成了当今平均孔隙度为7.47%的致密砂岩储层。据理论计算与实测物性数据进行对比,计算结果与实测结果基本吻合,相对误差小于3%。根据成岩作用的作用强度,结合岩石特征分析,可将研究区盒8段储层成岩相划分出4种,即弱-中胶结强溶蚀相、中胶结中溶蚀相、中溶蚀强胶结相和强压实致密相。综合试气成果可知,弱-中胶结强溶蚀相区域气产量较为可观,可将弱-中胶结强溶蚀相区域作为天然气持续上产的主要研究区域。     

Geological and Geochemical Characteristics and Exploration Prospect of Coal‐Derived Tight Sandstone Gas in China: Case Study of the Ordos,Sichuan, and Tarim Basins

This work extensively investigated global tight sandstone gas, and geologically and geochemically analyzed the tight sandstone gas in China's Ordos, Sichuan, and Tarim basins. We compared typical tight sandstone gas in China with that in North America. We proposed six conditions for the formation of China's tight sandstone gas, and illustrated the geological characteristics of tight sandstone gas. In China, gas-bearing tight sandstones were mainly deposited in continental lake deltas and marine-terrigenous facies basin environments, associated with coal-measure strata, and were mostly buried deeper than 2000 m under a formation pressure of 20–30 MPa, with pressure coefficients varying from overpressure to negative pressure. In other countries, tight gas bearing sandstones were dominantly deposited in marine to marine-terrigenous facies environments, occurred in coal-measure strata, and were mostly buried shallower than 2000 m in low-pressure systems. We systematically analyzed tight sandstone gas in the Ordos, Sichuan, and Tarim basins in terms of chemical compositions, geochemical characteristics of carbon isotopes, origins, and sources. Tight sandstone gas in China usually has a hydrocarbon content of 95%, with CH4 content 90%, and a generally higher dry coefficient. In the three above-mentioned large tight sandstone gas regions, δ13 C1 and δ13 C2 mainly ranges from-42‰ to-28‰ and from-28‰ to-21‰, respectively. Type III coal-measure source rocks that closely coexist with tight reservoirs are developed extensively in these gas regions. The organic petrology of source rocks and the carbon isotope compositions of gas indicate that tight sandstone gas in China is dominantly coal-derived gas generated by coal-measure strata. Our analysis of carbon isotope series shows that local isotope reversals are mainly caused by the mixing of gases of different maturities and that were generated at different stages. With increasing maturity, the reversal tendency becomes more apparent. Moreover, natural gas with medium-low maturity(e.g., Xujiahe Formation natural gas in the Sichuan Basin) presents an apparent reversal at a low-maturity stage, a normal series at a medium-maturity stage, and a reversal tendency again at a high-maturity stage. Finally, we proposed four conditions for preferred tight sandstone gas "sweep spots," and illustrated the recoverable reserves, proven reserves, production, and exploration prospects of tight sandstone gas. The geological and geochemical characteristics, origins, sources, and exploration potential of tight sandstone gas in China from our research will be instructive for the future evaluation, prediction, and exploration of tight sandstone gas in China and abroad.     

致密砂岩气储层有效性识别和定量评价 ——以鄂尔多斯盆地东南部上古生界山西组一段为例

储层有效性识别和定量评价是制约致密砂岩油气勘探的关键难题。以鄂尔多斯盆地东南部上古生界山西组一段为研究对象,从储层非均质性研究入手,开展砂岩微观—岩芯—测井尺度的细致观测,将含气储层砂岩划分为三种主要的岩石相,其中贫塑性颗粒岩屑石英砂岩构成了物性和含气性相对较好的有效储集岩石。运用薄片和岩芯数据标定不同岩石相的常规测井响应,建立了基于主成分统计分析的有效储集岩石测井识别模型,认识了有效储层的空间分布规律。将储层有效性研究从微观尺度的岩石相描述拓展到宏观尺度的量化表征,实现了致密砂岩气有效储集空间分布的定量评价。     

Critical conditions for natural gas charging and delineation of effective gas source rocks for tight sandstone reservoirs

Although it has been shown that the potential of tight‐sand gas resources is large, the research into the mechanisms of hydrocarbon charging of tight sandstone reservoirs has been relatively sparse. Researchers have found that there is a force balance during hydrocarbon charging, but discriminant models still have not been established. Based on the force balance conditions observed during gas migration from source rocks to tight sandstone reservoirs, a calculation formula was established. A formula for identifying effective source rocks was developed with the gas expulsion intensity as the discrimination parameter. The critical gas expulsion intensity under conditions of various burial depths, temperatures, and pressures can be obtained using the calculation formula. This method was applied in the Jurassic tight sandstone reservoirs of the eastern Kuqa Depression, Tarim Basin, and it was calculated that the critical expulsion intensity range from 6.05 × 10⁸ m³/km² to 10.07 × 10⁸ m³/km². The critical gas charging force first increases with depth and later decreases with greater depths. The distribution range of effective gas source rocks and total expelled gas volume can be determined based on this threshold. This method provides new insight into and method for predicting favourable tight‐sand gas‐bearing regions and estimating their resource potentials. Copyright © 2014 John Wiley & Sons, Ltd.     

同沉积期火山作用对鄂尔多斯盆地上古生界砂岩储层形成的意义

鄂尔多斯盆地上古生界主要为一套陆源碎屑沉积体系，其中广泛发育河流-三角洲相砂岩储集体，是该区上古生界天然气聚集成藏的主要场所。但由于陆源杂基的充填以及成岩压实作用、胶结作用的改造，大部分砂层储集性能都较差而无工业性储集意义。本文通过对鄂尔多斯盆地上古生界砂岩储层孔隙成因的分析，提出在局部层段集中分布的孔隙性砂岩，其孔隙主要为次生溶蚀成因。进一步的研究表明，由同沉积期火山作用形成的、分布于砂岩层中的火山碎屑组分的成岩溶蚀是次生溶孔形成的主要原因。因此，同沉积期火山作用控制了该区上古生界主要砂岩储层的发育和分布。中基性火山作用由于能提供较多的“易溶组分”，从而控制了次生溶孔发育的较高渗透性砂岩储层的分布； 而影响更为广泛的酸性火山作用则主要形成以蚀变高岭石晶间孔为主的低渗透性储层。     

鄂尔多斯盆地榆林气田陕151井区天然气富集高产因素简析

榆林气田陕151井区山西组二段储集层是实现增储上产的主力产层。影响该区天然气富集高产的主要因素:石炭—二叠系煤系烃源岩提供了丰富的生气母质,在低孔、低渗背景上发育了多期水下分流河道石英砂岩和岩屑石英砂岩有效储层,在平缓构造背景上发育的低幅度鼻隆构造带严格控制着气、水分布;山西组顶部发育的浅湖相泥岩提供了良好的盖层条件。     

海拉尔盆地呼和湖凹陷致密砂岩气成藏特征

海拉尔盆地呼和湖凹陷具备形成大面积致密砂岩气藏的地质条件,其断陷期地形比较宽缓,后期改造弱,主要发育低幅度的断背斜或宽缓的向斜,在局部具备稳定的构造条件。南二段煤系源岩广泛发育,丰度均达到中等--好烃源岩级别,为致密砂岩气藏的形成提供了充足的物质基础。洼槽区南二段储层属低孔--特低渗型储集层。南二段致密储层与煤、泥岩呈频繁互层状分布,形成致密砂岩气有利的的生储盖组合。构造高部位在一定程度上控制油气丰度,稳定的负向构造区有利于寻找储层富集区。呼和湖凹陷致密砂岩气主要表现为两种成藏组合,自生自储型和内生外储型,油气呈南北向条带状分布。     

Diagenesis of the Triassic Yanchang Formation Tight Sandstone Reservoir in the Xifeng–Ansai Area of Ordos Basin and its Porosity Evolution

This work aims to reveal the evolution of the porosity in the Triassic Yanchang Formation tight sandstone reservoir of the Xifeng–Ansai area of Ordos Basin. Based on destructive diagenesis(compaction and cementation) and constructive diagenesis(dissolution) of sandstone reservoirs, this study analyzed the diagenesis characteristics of the tight sandstone reservoirs in this area, and discussed the relationship between sandstone diagenesis and porosity evolution in combination with present porosity profile characteristics of sandstone reservoir. The effect simulation principle was employed for the mathematical derivation and simulation of the evolution of porosity in the Yanchang Formation tight sandstone reservoirs. The result shows that compaction always occurs in tight sandstone reservoirs in the Yanchang Formation, and cementation occurs when the burial depth increases to a certain value and remains ever since. Dissolution occurs only at a certain stage of the evolution with window features. In the corresponding present porosity profile, diagenesis is characterized by segmentation. From the shallow to the deep, compaction, compaction, cementation and dissolution, compaction and cementation occur successively. Therefore, the evolution of sandstone porosity can be divided into normal compaction section, acidification and incremental porosity section, and normal compaction section after dissolution. The results show that the evolution of sandstone porosity can be decomposed into porosity reduction model and porosity increase model. The superposition of the two models at the same depth in the three stages or in the same geological time can constitute the evolution simulation of the total porosity in sandstone reservoirs. By simulating the evolution of sandstone reservoir porosity of the eighth member in Xifeng area and the sixth member in Ansai area, it shows that they are similar in the evolution process and trend. The difference is caused by the regional uplift or subsidence and burial depth.     

鄂尔多斯盆地上古生界煤层气与致密气联合优选区评价

鄂尔多斯盆地上古生界具有煤层气和致密砂岩气成藏的有利条件。上古生界煤层气与致密砂岩气具有相同的烃源岩,且煤层与致密储层垂向上相互叠置,为二者联合勘探开发奠定了地质基础。在综合考虑煤层气与致密砂岩气成藏地质条件的基础上,建立了鄂尔多斯盆地煤层气与致密砂岩气共同勘探选区的评价指标体系,包括煤层厚度、烃源岩热演化程度、生气强度以及致密储层厚度4个指标。依据建立的评价指标体系,对鄂尔多斯盆地内5个区块进行煤层气与致密砂岩气共同选区评价,评价结果为区块Ⅱ、Ⅲ和Ⅴ为勘探目标区,主要分布在盆地的东西缘,煤层厚度大、烃源岩生气强度大,勘探前景好;区块Ⅰ和Ⅳ为勘探有利区,呈条带状分布在盆地的东北部和西北部,煤层气与致密砂岩气协同勘探潜力较大。     

Coupled accumulation characteristics of Carboniferous-Permian coal measure gases in the Northern Ordos Basin,China

The northern Ordos Basin provides a favorable geological environment for the accumulation and development of coal measure gases (CMG). The hydrocarbon generation potential and reservoir systems of the coal measures have been studied based on data from experimental tests and production and exploration wells, respectively. Further, the coupled accumulation characteristics were determined. The results show that the source rocks are characterized by favorable hydrocarbon generation potential, high thermal evolution (Ro%?=?1.3–2.3%), and mainly type III kerogen. Coals, typically aggregated organic matter, with a huge hydrocarbon generation potential (avg. 89.11 mg/g) and total organic content (TOC) (avg. 65.52%), are predominantly involved in gaseous hydrocarbon generation. Shales with good TOC contents (avg. 2.36%) and large cumulative thicknesses have an important role in gaseous hydrocarbon generation. Coal seams, shale layers, and sandstone layers occur as variably interbedded deposits, which form a favorable environment for CMG coupled accumulation. The porosity and permeability are ranked as follows: sandstone?>?coal?>?shale, with significant stress sensitivity and anisotropy. Two continuous gas generation peaks occurred in the Late Jurassic and Late Cretaceous, with an abundant amount of coal-derived and thermogenic gas generation, respectively. Potential gas-bearing sandstone layers can be formed by gas migration via short distances from nearby coal seams and shale layers. Coupled accumulation of CMG occurred in three stages: (1) stacked and interbedded reservoirs formation stage; (2) gas generating and charging stage; and (3) coupled accumulation adjustment stage. Coalbed methane (CBM)–tight sandstone gas (TSG) assemblage is a favorable target for CMG accumulation and development.     

Hydrocarbon Generation and Expulsion of the Upper Triassic T3x5 Source 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(T3x5) 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(Ro1.2%) 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 T3x5 source rocks is 3.14×1010 t and 1.86×1010 t, respectively, with a residual amount of 1.28×1010 t 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 T3x5 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 9.3×108 t. Geological resources of shale gas are up to 1.05×1010 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.     

http://www.sciencedirect.com/science/article/pii/S167498711200031X

Upper Paleozoic coal measures in the Ordos Basin consist of dark mudstone and coal beds and are important source rocks for gas generation.Gas accumulations include coal-bed methane（CBM）, tight gas and conventional gas in different structural areas.CBM accumulations are mainly distributed in the marginal area of the Ordos Basin,and are estimated at 3.5×10¹² m³.Tight gas accumulations exist in the middle part of the Yishan Slope area,previously regarded as the basin-centered gas system and now considered as stratigraphic lithologic gas reservoirs.This paper reviews the characteristics of tight gas accumulations:poor physical properties(porosity < 8%,permeability < 0.85×10^-3μm²),abnormal pressure and the absence of well-defined gas water contacts.CBM is a self-generation and selfreservoir, while gas derived from coal measures migrates only for a short distance to accumulate in a tight reservoir and is termed near-generation and near-reservoir.Both CBM and tight gas systems require source rocks with a strong gas generation ability that extends together over wide area.However,the producing area of the two systems may be significantly different.     

松辽盆地南部深层致密砂岩气储层形成机制及成藏主控因素

为了加快松辽盆地南部（简称松南）深层致密砂岩气勘探开发进程,开展致密砂岩储层形成机制及成藏主控因素研究。通过对松南深层致密砂岩的分析,根据致密砂岩岩性组合特征将已发现的深层致密气类型划分为稳定厚层砂型、砂泥互层型、泥包砂型3种类型,储层物性普遍差,孔隙度多小于6%,渗透率主体<0.10×10^-3 μm²,属于特低孔、特低渗储层。通过对松南典型致密储层矿物成分与微观特征的分析发现,致密砂岩有效储层形成主要受3个方面因素控制：一是早成岩期发育绿泥石包壳,有效抑制成岩中后期粒间钙质胶结、硅质胶结的发生,保护原生残余粒间孔隙;二是富火山岩岩屑溶蚀形成次生孔隙;三是生烃增压产生大量微裂缝,改善储层渗流特征。在此基础上总结出松南致密砂岩气成藏控制因素,即充足气源提供物质基础、斜坡古沟谷与断裂控砂、次生溶蚀与微裂缝控储、断裂活动与稳定盖层控富。     

三肇凹陷扶余油层致密油资源评价与参数研究

松辽盆地三肇凹陷扶余油层发育河流-浅水三角洲环境下形成的低渗透致密砂岩储集层,已发现的探明储量以常规砂岩储层中的岩性油藏为主。剩余资源以赋存于孔隙度小于10%、渗漏率小于1×10^-3 μm²储集层中的致密油为主。本文分析三肇凹陷扶余油层致密油成藏条件,采用致密油的资源评价方法(小面元容积法、资源丰度类比法及EUR类比法)对研究区源下致密油资源进行评价,并初步估算青山口组一段泥岩的生烃量,获取了泉四段致密油的地质资源量、运聚系数、最终可采资源量、可采系数、地质资源丰度和可采资源丰度等关键参数,这类参数代表了松辽盆地源下致密油资源评价的关键参数,对评价其它地区相同类型的致密油具有借鉴意义。