Characteristics and exploration targets of Chang 7 shale oil in Triassic Yanchang Formation, Ordos Basin, NW China

The geological characteristics and enrichment laws of the shale oil in the third submember of the seventh member of Triassic Yanchang Formation(Chang 7_(3)) in the Ordos Basin were analyzed by using the information of core observations, experiments and logging, and then the exploration potential and orientation of the Chang 7_(3) shale oil were discussed. The research findings are obtained in three aspects. First, two types of shale oil, i.e. migratory-retained and retained, are recognized in Chang 7_(3). The former is slightly better than the latter in quality. The migratory-retained shale oil reservoir is featured with the frequent interbedding and overlapping of silty-sandy laminae caused by sandy debris flow and low-density turbidity current and semi-deep-deep lacustrine organic-rich shale laminae. The retained shale oil reservoir is composed of black shale with frequent occurrence of bedding and micro-laminae. Second, high-quality source rocks provide a large quantity of hydrocarbon-rich high-quality fluids with high potential energy. The source-reservoir pressure difference provides power for oil accumulation in thin interbeds of organic-poor sandstones with good seepage conditions and in felsic lamina, tuffaceous lamina and bedding fractures in shales. Hydrocarbon generation-induced fractures, bedding fractures and microfractures provide high-speed pathways for oil micro-migration. Frequent sandstone interlayers and felsic laminae provide a good space for large-scale hydrocarbon accumulation, and also effectively improve the hydrocarbon movability. Third, sand-rich areas around the depression are the main targets for exploring migratory-retained shale oil. Mature deep depression areas are the main targets for exploring retained oil with medium to high maturity. Theoretical research and field application of in-situ conversion in low-mature deep depression areas are the main technical orientations for exploring retained shale oil with low to medium maturity.

Organic matter transformation ratio, hydrocarbon expulsion efficiency and shale oil enrichment type in Chang 7_(3) shale of Upper Triassic Yanchang Formation in Ordos Basin, NW China

The major enrichment type of shale oil in the Chang 7_(3) shale of Upper Triassic Yanchang Formation in the Ordos Basin is unknown.This paper analyzes the organic matter transformation ratio,hydrocarbon expulsion efficiency and roof/floor sealing conditions of the Chang 7_(3) shale,and evaluates the major enrichment type of shale oil in this interval.The average organic matter transformation ratio of the Chang 7_(3) shale is about 45%;in other words,more than 50%of the organic matters have not transformed to hydrocarbons,and the lower the maturity,the greater the proportion of untransformed organic matters.The cumulative hydrocarbon expulsion efficiency of the transformed hydrocarbon is 27.5% on average,and the total proportion of untransformed organic matters plus retained hydrocarbons is greater than 70%.The relative hydrocarbon expulsion efficiency of the Chang 7_(3) shale is 60%on average,that is,about 40% of hydrocarbons retain in the shale.The Chang 7_(3) shale corresponds to Chang 7_(1+2) and Chang 8 sandstones as the roof and floor,respectively,and is further overlaid by Chang 6 shale,where extensive low porosity and low permeability–tight oil reservoirs have formed in the parts with relatively good porosity and permeability.Moreover,the Chang 7_(3) shale is tested to be in a negative pressure system(the pressure coefficient of 0.80–0.85).Therefore,the roof/floor sealing conditions of the Chang 7_(3) shale are poor.The retained hydrocarbons appear mostly in absorbed status,with low mobility.It is concluded that the medium–high mature shale oil is not the major enrichment type of shale oil in the Chang 7_(3) shale,but there may be enrichment opportunity for shale oil with good mobility in the areas where the sealing conditions are good without faults and fractures and oil reservoirs are formed off Chang 7_(1+2),Chang 6 and Chang 8.Furthermore,low–medium mature shale oil is believed to have great potential and is the major enrichment type of shale oil in the Chang 7_(3) shale.It is recommended to prepare relevant in-situ conversion technologies by pilot test and figure out the resource availability and distribution.

Predicting the present-day in situ stress distribution within the Yanchang Formation Chang 7 shale oil reservoir of Ordos Basin, central China

The Yanchang Formation Chang 7 oil-bearing layer of the Ordos Basin is important in China for producing shale oil.The present-day in situ stress state is of practical implications for the exploration and development of shale oil;however,few studies are focused on stress distributions within the Chang 7 reservoir.In this study,the present-day in situ stress distribution within the Chang 7 reservoir was predicted using the combined spring model based on well logs and measured stress data.The results indicate that stress magnitudes increase with burial depth within the Chang 7 reservoir.Overall,the horizontal maximum principal stress(SHmax),horizontal minimum principal stress(Shmin) and vertical stress(Sv) follow the relationship of Sv≥SHmax>Shmin,indicating a dominant normal faulting stress regime within the Chang 7 reservoir of Ordos Basin.Laterally,high stress values are mainly distributed in the northwestern parts of the studied region,while low stress values are found in the southeastern parts.Factors influencing stress distributions are also analyzed.Stress magnitudes within the Chang 7 reservoir show a positive linear relationship with burial depth.A larger value of Young's modulus results in higher stress magnitudes,and the differential horizontal stress becomes higher when the rock Young's modulus grows larger.

Geological characteristics and exploration of shale oil in Chang 7 Member of Triassic Yanchang Formation, Ordos Basin, NW China

A set of shale-dominated source rocks series were deposited during the heyday of lake basin development in the Member 7 of Triassic Yanchang Formation,Ordos Basin,and the thickness is about 110 m.Aimed at whether this layer can form large-scale oil enrichment of industrial value,comprehensive geological research and exploration practice have been carried out for years and obtained the following important geologic findings.Firstly,widely distributed black shale and dark mudstone with an average organic matter abundance of 13.81%and 3.74%,respectively,lay solid material foundation for the formation of shale oil.Secondly,sandy rocks sandwiched in thick organic-rich shale formations constitute an oil-rich"sweet spot",the average thickness of thin sandstone is 3.5 m.Thirdly,fine-grained sandstone and siltstone reservoirs have mainly small pores of 2–8μm and throats of 20–150 nm in radius,but with a large number of micro-pores and nano-throats,through fracturing,the reservoirs can provide good conductivity for the fluid in it.Fourthly,continued high-intensity hydrocarbon generation led to a pressure difference between the source rock and thin-layer reservoir of up to 8–16 MPa during geological history,driven by the high pressure,the oil charged into the reservoirs in large area,with oil saturation reaching more than 70%.Under the guidance of the above theory,in 2019,the Qingcheng Oilfield with geologic oil reserves of billion ton order was proved in the classⅠmulti-stage superimposed sandstone shale reservoir of Chang 7 Member by the Changqing Oilfield Branch through implementation of overall exploration and horizontal well volume fracturing.Two risk exploration horizontal wells were deployed for the classⅡthick layer mud shale interbedded with thin layers of silt-and fine-sandstones reservoir in the Chang 73 submember,and they were tested high yield oil flows of more than 100 tons per day,marking major breakthroughs in petroleum exploration in classⅠshale reservoirs.The new discoveries have expanded the domain of unconventional petroleum exploration.

Black shale formation enviro nment and its control on shale oil enrichment in Triassic Chang 7 Member,Ordos Basin,NW China

Based on geochemical analysis results of core samples from the Triassic Chang 7 Member of Well Feng 75 drilled in the northwest margin of Ordos Basin,combined with geological characteristics of this region,the formation environment of the black shale and its control on shale oil enrichment are comprehensively studied.From the Chang 73 to Chang 71 Sub-members,the black shale have organic carbon contents decreasing from 5.70%to 3.55%,hydrogen indexes decreasing from 345 mg/g to 269 mg/g,while the oxygen indexes increasing gradually from 6 mg/g to 29 mg/g,indicating that the sedimentary environment during the depositional period of Chang 72 and Chang 73 Sub-members was anoxic.Biomarkers in the black shale change regu-larly,and have an obvious“inflection point”at the depth of 2753–2777 m in the Chang 73 Sub-member,indicating that the input of terrigenous organic matter increased.However,there is a negative drift about 2%of organic carbon isotopic composition near the“inflection point”,which is in conflict with the results of biomarker compounds.This is because the extreme thermal and anoxic events caused by continental volcanic activity in the ancient Qinling region caused negative drift of carbon isotopic composition of the black shale in the Ordos Basin.The volcanic activity caused rise of temperature,polluted air,extreme weathers,more floods and thus more input of terrigenous organic matter,and gave rise to extremely anoxic environment con-ducive to the preservation of organic matter.Terrigenous organic matter is more conducive to the formation of light oil than aquatic organic matter,so these sections in Yanchang Formation are major“sweet spots”for shale oil enrichment.

The origin and accumulation model of crude oils from oil reservoirs Chang 9 and Chang 10 in the Yanchang Formation of the Ordos Basin

In the lower parts of oil reservoirs Chang 9 and Chang 10 of the Yanchang Formation are oil-bearing layers newly found in oil exploration in the Ordos Basin.Based on GC,GC-MS analyses of saturated hydrocarbons from crude oils and source rocks,reservoir fluid inclusions and BasinMod,the origin of crude oils,accumulation period and accumulation models are discussed in combination with other petroleum geology data in this paper.The result shows that(1) there are two different types of crude oils in oil reservoir Chang 9 in the Longdong and Jiyuan regions:crude oils of typeⅠ(Well D86,Well A44,Well A75,Well B227,Well X62 and Well Z150) are mainly de-rived from the Chang 7 source rocks(including mudstones and shales) and distributed in the Jiyuan and Longdong regions;those of typeⅡ(Well Z14 and Well Y427),are distributed in the Longdong region,which are derived from the Chang 9 source rocks.Crude oils from oil reservoir Chang 10 in the Shanbei region are mainly derived from the Chang-9 source rocks;(2) there are two phases of hydrocarbon filling in oil reservoir Chang 9 in the Jiyuan and Longdong regions and oil reservoir Chang 10 in the Shanbei region:The first phase started at the early stage of J2z.The process of hydrocarbon filling was discontinuous in the Late Jurassic,because of the tectonic-thermal event in the Ordos Basin.The second phase was the main accumulation period,and hydrocarbons began to accumulate from the late stage of J2a to the middle-late of K1,mainly at the middle-late stage of K1;(3) there exist two types of accu-mulation models in oil reservoirs Chang 9 and Chang 10 of the Yanchang Formation:source rocks of the reservoirs in oil reservoir Chang 9 in the Jiyuan region and oil reservoir Chang 10 in the Shanbei region,the mixed type of reservoirs on the lateral side of source rocks and source rocks of the reservoirs in oil reservoir Chang 9 in the Long-dong region.

鄂尔多斯盆地中部罗庞塬地区长7储层控油性及有利区评价

致密油分布的控制因素研究与有利区评价影响着非常规油气的勘探部署。以鄂尔多斯盆地罗庞塬地区长7油层组致密油为研究对象,利用测井、钻井、岩心、压汞、试油成果等资料,研究储层砂体厚度、岩性、储集空间和物性等特征,明确油藏类型,探讨储层条件对致密油的控制作用并评价了有利区。研究表明:罗庞塬地区长7砂体厚度平均为22.6 m,储层岩性主要为细粒度的长石砂岩,储集空间以粒间溶蚀孔和粒间孔为主,其孔隙度平均为8.04%,渗透率平均为0.36×10^(-3)μm^(2),发育小孔-细喉型、细孔-细喉型和微孔-微喉型储层,油藏类型为透镜状致密油藏,呈现出成群、成带的准连续型分布特征,其分布主要受砂体厚度、砂地比、孔隙度、渗透率和砂岩泥质含量的控制,砂体厚度大、泥质含量低、物性好的细砂岩有利于致密油的富集。采用综合指数法,评价出长7油层有4个Ⅰ类区和5个Ⅱ类有利勘探区。

鄂尔多斯盆地合水地区三叠系长7段夹层型页岩油储层特征及主控因素

运用铸体薄片、扫描电镜、黏土矿物X射线衍射、电子探针、阴极发光、高压压汞、物性测试等资料,对鄂尔多斯盆地西南部合水地区三叠系延长组长7段夹层型页岩油储层特征及储层致密化主控因素进行了研究,建立了储层定量评价标准,并预测出有利储层分布。研究结果表明:(1)鄂尔多斯盆地合水地区三叠系长7段夹层型页岩油储层主要为岩屑长石砂岩与长石岩屑砂岩,成分成熟度低、填隙物含量高、孔喉结构复杂,具有高孔低渗特征。(2)胶结作用是研究区长7段夹层型页岩油储层致密化的主控因素,储层平均视胶结率为86.3%,达到强胶结程度,以自生黏土矿物中的伊利石胶结为主;压实作用对储层致密化起次要作用,储层平均视压实率为46.0%,为中等压实程度;溶蚀作用降低了储层的致密化程度,但储层渗流能力较低,酸性流体难以大规模溶蚀,平均视溶蚀率仅为13.8%,为弱溶蚀程度。(3)受中等压实—弱溶蚀—强胶结成岩作用的影响,储层非均质性较强,成岩系数差异较大。Ⅰ类储层成岩系数大于2.4,Ⅱ1类储层成岩系数为1.8~2.4,Ⅱ2类储层成岩系数为1.2~<1.8,Ⅲ类储层成岩系数小于1.2,Ⅰ类与Ⅱ1类储层为有利储层。区域上中部混源区有利储层发育规模最大,是勘探的主要目标区。

鄂尔多斯盆地东南部长7段页岩油气富集主控因素

为明确鄂尔多斯盆地东南部长7段页岩油气富集主控因素,综合钻井、测井、岩心分析化验等资料,对研究区长7段页岩油气富集程度及其机理进行研究。页岩解析气量与烃源岩总有机碳含量呈正比,有机质含量控制页岩油气的总含量,有机质发育大量孔隙,页岩油气以吸附态和游离态赋存于有机孔隙中。储集层孔隙结构和孔隙度影响页岩油气的含量及赋存状态,吸附油气主要赋存于微孔中,游离油气主要赋存于中孔和大孔中,但中孔中游离气含量高于大孔,而孔隙度越大,页岩中油气绝对含量越高。砂岩夹层和富有机质页岩的配置关系控制着页岩油气的富集部位,根据粉砂岩、细砂岩与页岩的关系,延长组长7段页岩油气可划分为近源和源内2类,源内又可分为砂岩与页岩互层型、页岩夹砂岩型和页岩型;下伏于富有机质页岩中的砂体和透镜状砂体油气含量最高,其次是上覆于富有机质页岩的砂体和呈舌状或指状与富有机质页岩接触的砂体。

鄂尔多斯盆地西南部HQ地区长7段烃源岩地球化学特征与长8段原油来源分析

鄂尔多斯盆地西南部HQ地区是玉门油田的流转区块,是增储上产的重要勘探新区,受多期构造运动影响,油气来源备受争议。本文选取上三叠统延长组长7不同亚段泥页岩和长8段原油样品,采用总有机碳测定、岩石热解、显微组分、饱和烃气相色谱-质谱等实验分析方法,对选取的样品的地球化学特征进行研究,结合谱系聚类、多维标度、主成分分析进行油源对比,并从烃源岩有效性和油气成藏条件对油源对比结果进行合理性探讨。结果表明,(1)研究区东部长7段烃源岩总体为好-优质烃源岩级别,西部长7段烃源岩为中等-好烃源岩级别;东部长7段烃源岩以Ⅰ-Ⅱ_(1)型干酪根为主,西部长7段烃源岩以Ⅱ_(1)-Ⅱ_(2)型干酪根为主;长7段烃源岩有机质热演化程度总体上处于成熟阶段;(2)HQ东部地区长8段原油由本地长7_(3)亚段黑色页岩供烃,西部长8段原油由本地长7_(3)亚段深灰色泥岩与东部长7_(3)亚段黑色页岩混合供烃;(3)长7_(3)亚段黑色页岩有机碳含量高,为优质排烃源岩;长7_(3)亚段深灰色泥岩有机碳含量较高,可作为有效排烃源岩。晚侏罗世为长8段油藏第I期油气成藏期,此时东部烃源岩生成的低熟油主要向着研究区西部的构造高部位运移;早白垩世末期研究区西部烃源岩达到成熟,西部烃源岩生成的原油对本地长8油藏供烃。研究成果对鄂尔多斯盆地西缘进一步油气勘探具有理论指导意义。

Sedimentary and geochemical characteristics of the Triassic Chang 7 Member shale in the Southeastern Ordos Basin,Central China

The Ordos Basin is the largest petroliferous basin in China, where the Chang 7 Member shale serves as the major source rock in the basin, with an area of more than 100,000 km^2 So far, sedimentary and geochemical characterizations have rarely been conducted on the shale in shallow(< 1000 m) areas in the southeastern part of the basin, but such characterizations can help identify the genesis of organic-rich shale and promote the prediction and recovery of shale oil. In this paper,several outcrop sections of the Chang 7 Member in the Tongchuan area were observed and sampled, and sedimentary and geochemical characterizations were conducted for the well-outcropped YSC section. The study results show that the Chang7 Member shale is widely distributed laterally with variable thickness. The organic-rich shale is 7-25 m thick in total and exhibits obvious horizontal variation in mineral composition. In the eastern sections, the shale contains organic matter of TypeⅡ_2-Ⅲ and is low in thermal maturity, with high clay mineral content, low K-feldspar content, and no pyrite. In the western sections, the shale contains Type Ⅱ_1 organic matter and is low in thermal maturity, with high clay mineral, K-feldspar, and pyrite contents. The YSC section reveals three obvious intervals in vertical mineral composition and organic abundance.The Chang 7 Member organic-rich shale(TOC > 10%) contains mainly sapropelite and liptinite, with Type Ⅱ kerogen. It is generally characterized by a hydrocarbon potential of more than 70 mg/g, low maturity, and shallow-semideep lacustrine facies. In the western sections, the shale, still in a low maturity stage, has a higher hydrocarbon potential and is optional for shale oil recovery. However, the Chang 7 Member shale in the study area is highly heterogeneous and its shale oil recovery is practical only in the organic-rich intervals.

陆相页岩层系岩性组合模式及其对原油差异性富集的控制作用:以鄂尔多斯盆地三叠系延长组长7段为例

为明确陆相页岩层系原油岩性组合模式类型及其对原油富集的影响,优选下一步勘探的有利目标,本次研究在岩心观察与测井解释的基础上,通过储层物性测试、镜下观察、地球化学分析等技术手段,对鄂尔多斯盆地三叠系延长组长7段烃源岩和储层叠置关系与特征进行分析,并基于不同区块油藏解剖,探讨不同岩性组合模式对原油差异性富集的控制作用。本次研究将长7段岩性组合模式划分为8种类型(A型—H型)。其中,A型—C型为重力流型,以长7段发育厚层重力流砂体和黑色页岩与暗色泥岩为主要特征,A型、C型主要分布在陇东地区,B型在全盆地均有分布。D型—G型为三角洲前缘型,以发育三角洲前缘砂和暗色泥岩为主要特征,主要分布在陕北地区。H型为页岩型,长7_(3)至长7_(1)均为泥页岩,中间夹薄层泥页岩。重力流型(A型—C型)烃源岩有机质丰度明显好于三角洲前缘型(D型—G型)烃源岩,是重力流沉积地区原油富集程度高于三角洲前缘沉积地区的主要原因。B型、G型和H型储层物性最差,导致同一沉积地区、不同区块原油富集程度存在差异。不同岩性组合模式岩性变化控制不同亚段和不同区块原油富集程度,A型岩性组合原油富集程度最高,长7_(1)和长7_(2)均有规模性油藏被发现;G型岩性组合原油富集程度最低,长7_(1)至长7_(3)油藏零星分布。

鄂尔多斯盆地庆城地区三叠系长7段烃源岩特征及控藏作用

鄂尔多斯盆地三叠系长7段是页岩油的重点研究领域。通过总有机碳测定、氯仿抽提、岩石热解、XRD全岩矿物分析、扫描电镜观察等,对鄂尔多斯盆地庆城地区三叠系长7段烃源岩特征进行了分析,并利用多元回归线性法建立了有机碳与测井曲线的三维电测模型,明确了烃源岩的空间展布特征及其的控藏作用。研究结果表明:(1)鄂尔多斯盆地庆城地区三叠系长7_(1)、长7_(2)和长7_3小层泥页岩样品TOC平均值分别为5.01%,6.04%和6.76%,氯仿沥青“A”的平均值分别为0.63%,0.67%和0.73%,整体有机质类型以Ⅱ_(1)型和Ⅱ_(2)型为主,处于成熟—高成熟阶段,含油性与可动性均较好,达到较好—极好烃源岩级别。(2)研究区泥页岩样品主要由石英长石与黏土矿物组成,孔隙类型主要为原生粒间孔、晶间孔及有机质收缩缝,但各样品的孔径分布不同。(3)研究区烃源岩TOC下限为1.50%,庆城地区附近长7_(2)小层、庆城与环县地区附近长7_(3)小层为主要有效烃源岩发育区。(4)有效烃源岩的TOC含量及其空间展布特征影响了页岩油藏的含油性,其中TOC含量直接决定了产油量的高低。距离生烃中心越近越有利于油气聚集。

鄂尔多斯盆地陕北地区三叠系长7段致密油分布特征及控制因素

综合利用地球化学、扫描电镜、岩心薄片、测井等资料以及油井生产数据等,对鄂尔多斯盆地陕北地区三叠系延长组7段储层特征、烃源岩特征和致密油分布特征进行了分析,从烃源岩展布、输导体系和源-储组合关系3个方面对致密油差异富集控制因素进行了探讨,并总结了成藏模式。研究结果表明:(1)陕北地区长7段致密砂岩储层主要分布在一亚段(长71)和二亚段(长72),以灰色—灰白色长石砂岩和岩屑长石砂岩为主,长71和长72平均孔隙度分别为5.56%和7.32%,平均渗透率分别为0.097 m D和0.110 m D,长72储层物性更好;孔隙空间以溶孔为主,发育少量粒间孔。(2)研究区烃类主要来源于本地长72顶部和长73这2套烃源岩,平均厚度大于20 m,有机质丰度高,平均TOC值为3.02%,干酪根类型以Ⅰ型和Ⅱ1型为主,处于生烃高峰期,平均生烃量为270.2×10^(4)t/km^(2),长73烃源岩生烃潜力更大,供烃至长72储层,长71致密油来源于长72烃源岩;新安边地区三角洲前缘亚相末端的长72储层中致密油由湖盆烃源岩侧向供烃。(3)研究区致密油富集受烃源岩展布、砂体连通性以及源-储组合共同控制,在长72更富集,在新安边地区分布面积最大,安塞地区无大规模致密油聚集;纵向上和平面上致密油的聚集差异受控于烃源岩厚度和源-储组合关系,下生上储、上下生油而中间储集和砂泥互层时含油性更好;新安边地区三角洲前缘亚相末端的长72致密油聚集规模大于三角洲前缘主体,是由于三角洲前缘末端发育的局部连通砂体阻碍了湖盆烃类物质的侧向运移。(4)研究区致密油为“源控-砂控”成藏模式,远源河道优势砂体尖灭处和近源局部连通的砂体是有利勘探区。

吴起油田白豹地区东部长8、长9储层特征研究

对鄂尔多斯盆地吴起油田白豹东部地区长8、长9储层进行储层特征研究。结果表明:白豹东部长8和长9储层的砂岩多为长石砂岩和岩屑长石砂岩;储层孔喉类型属于细孔粗喉,渗透率为强非均质型;长8砂体发育好,长9砂体发育程度差。同时储层敏感性研究表明:白豹项目区的长8、长9储层均为弱-中速敏、弱水敏和弱碱敏及中偏弱应力敏特征,但长8储层显示为弱酸敏,长9储层为强酸敏。

吴起油田W油区长7油层油气成藏因素分析

针对油气藏分布及主控因素认识不清等问题,文章在烃源岩、储层等方面进行油气地质条件分析的基础上,从油水层识别、油气藏类型及分布等方面开展了油气控制因素分析工作。研究表明:(1)吴起油田W油区长7油页岩厚度在15~25 m,TOC含量远大于2%、Ro为0.8%;长73、长72、长71东北部砂体较为发育,主河道砂体厚度分别为15~25 m、15~23 m、15~28 m。(2)吴起油田W油区长7主要发育鼻状构造、砂岩透镜体、致密砂岩遮挡等类型油藏,主要富集三角洲前缘水下分流河道,河道砂岩与分流间湾泥岩的合理有效配置是成藏的关键。

鄂尔多斯盆地华池地区X96井长7烃源岩地球化学特征及其对致密油成藏的意义

为深化致密油成藏机理,优选湖盆中部华池地区X96井展开全取芯的有机碳、热解、饱和烃色谱色质、干酪根镜检等分析及排烃、成藏等综合地质研究。重点利用这些分析测试资料对X96井长7烃源岩地球化学特征展开详细评价并探讨优质烃源岩在致密油成藏中的作用。X96井长7烃源岩包括油页岩、泥岩与粉砂质泥岩等3种类型,其中油页岩的有机质丰度高(平均15.8%),有机质组分以无定形体为主,有机质类型好(Ⅰ型为主),并处于生油高峰阶段,属于优质烃源岩。优质烃源岩生烃量大,强大的体积膨胀作用为其提供了充足的排烃动力,排烃作用较强,造成油页岩相对较低的残留沥青"A"转化率、饱和烃/芳烃值与产率指数,排烃效率超过70%。区域上,油页岩稳定分布于长7底部,上覆大范围致密砂岩,源储直接接触。此类广覆式展布的优质烃源岩大范围、高强度的排烃作用为致密油成藏提供了物质基础与动力来源,对近源致密油的成藏意义重大。

吴起、定边地区上三叠统延长组长7—长9储层特征研究

为研究鄂尔多斯盆地吴起、定边地区延长组长7—长9油层组的储层特征,利用薄片、粒度、压汞、物性等资料,对储层的岩石学、孔隙结构、物性等特征进行了分析,并分析了沉积作用、成岩作用对储层物性的影响。研究结果表明:吴起、定边地区上三叠统延长组长7—长9油层组的储层主要发育岩屑长石砂岩;孔隙以溶蚀粒间孔为主,孔隙度主要为8%～12%,渗透率主要为0.1～1mD。压实作用使储集层的原始孔隙空间损失;胶结作用不仅破坏了部分原生孔隙,而且使部分次生溶孔也遭到了破坏;溶解作用使储层物性得到了改善。

胡尖山—姬塬地区长7段油页岩定性定量评价及长9油藏勘探评价

鄂尔多斯盆地胡尖山—姬塬地区长9油藏油水分布关系复杂,给勘探带来较大困难。长9油藏的油源来自于长7段油页岩,并与长9油藏构成了“上生下储”型生储组合。为此,以长9油藏的成藏理论为指导,开展了基于测井资料的长7段油页岩识别,用以指导长9油藏有利区的快速识别。通过岩性与测井系列分析认为,研究区长7段油页岩测井表现为“高自然伽马、高电阻率、高声波时差、低密度、低自然电位”的特性,依据该特性,形成了定性识别油页岩的“三步法”:第1步,利用自然伽马曲线排除砂岩;第2步,依据页岩渗透性特点,利用自然电位曲线确定页岩;第3步,综合声波时差、密度及电阻率曲线的特征,最终确定油页岩。在油页岩定性识别的基础上,通过砂岩基线与自然伽马曲线、泥岩基线与自然电位曲线、自然电位与自然伽马曲线、声波时差与密度曲线的交会面积及油页岩厚度共5项参数,定义了油页岩“综合影响系数”参数,用以定量表征油页岩发育程度。应用长7段油页岩的量化评价结果指导长9油藏的勘探评价,发现了H89等3个油藏,应用效果较好。

鄂尔多斯盆地甘泉地区长7页岩油储层非均质性及其控油规律

为揭示鄂尔多斯盆地伊陕斜坡东南部甘泉地区长7油层组页岩油储层的宏观非均质性及其对石油分布的控制作用,通过隔夹层识别统计、渗透率统计及劳伦兹曲线构建等方法,定量表征并比较了长7_(1)、长7_(2)油层亚组的宏观非均质性,利用相关分析和多因素叠合的方法,分析了宏观非均质性对石油分布的影响。研究结果表明:研究区长7_(1)、长7_(2)页岩油储层平均发育夹层数分别为3.8、5.1层,砂体渗透率以复合韵律为主,且非均质性强;平均发育隔层数分别为3.4、2.8层,单隔层的平均厚度分别为6.0、4.9 m;长7_(1)较长7_(2)表现为稍弱的层内非均质性和较强的层间非均质性。页岩油砂岩储层的韵律性对含油饱和度有明显的影响,厚度大于10.0 m的隔层对油气有明显的封盖作用,“物性”隔夹层则构成油气聚集的侧向遮挡。长7_(1)油层亚组较长7_(2)油层亚组隔层更为发育,而长7_(2)油层亚组油气更富集。平面上,油气富集区分布呈条带状,多位于砂体厚度大且连续性较好、渗透率大于0.2 mD的区域,顺河道砂体延伸的方向上油层厚度变化小,垂直河道延伸方向上变化较大。研究结论可为鄂尔多斯盆地伊陕斜坡东南部长7夹层式页岩油有利区评价及开发参数优选提供理论参考。