鄂尔多斯盆地上三叠统延长组长7段富有机质页岩是这一区域页岩油、致密油的主要烃源岩,其生排烃特征是石油勘探开发的关键问题.采取鄂尔多斯盆地西南缘三叠系延长组长7段低熟(Ro=0.55％)页岩岩心样品(TOC=3.59％),设置不同模拟温度(300～570℃),开展原岩岩心柱状样品的半封闭体系生排烃模拟实验,获得了不同成熟度梯度的页岩模拟样品残余及排出烃类.利用低熟煤样标定各模拟温度点的成熟度(0.60％

The Jurassic Yan'an Formation (J1y) crude oil-associated gas in the Pengyang area of the Ordos Basin contains a certain amount of H2S. The study of its genesis is important for us to predict the distribution of H2S in Mesozoic in the basin. The Chang7 source rock of the Yanchang Formation (T3y) is the principal source of crude oil in the Jurassic Yan'an Formation area. However, H2S is not detected in the crude oil-associated gas of Chang10 to Chang3 members of the Yanchang Formation. As a result, the formation of H2S in the crude oil-associated gas of Yan'an Formation may be related to reservoir and accumulation factors. The study shows that Jurassic formation water has a high salinity and is rich in divalent sulfur, which inhibits the development of sulfate-reducing bacteria (SRB). It is less likely to biologically reduce sulfate to produce H2S. The δ34S values of H2S in crude oil-associated gas of Yan'an Formation are greater than 25‰, which are obviously different from those of volcanic hydrothermal fluid, organic matter, and microbial reduction products, but similar to divalent sulfur isotope values in formation water and about 10‰ negative to sulfate ion in formation water. TSR has generated sulfur isotope distribution and fractionation characteristics in H2S. The temperature measurement of reservoir inclusions in the Jurassic Yan'an Formation shows that the initial filling temperature of oil and gas is higher than 100 °C, and the maximum accumulation forming temperature is 150 °C. The formation water of Yan'an Formation contains a large number of sulfate ions from anhydrite or buried stage. Those rich sulfate ions meet the conditions for a sulfate thermochemical reduction reaction. At the same time, the rich magnesium ions in formation water catalyzed the reaction. Therefore, H2S in Jurassic crude oil-associated gas in the Pengyang area of the Ordos Basin has thermochemical sulfate reduction (TSR) genesis.

鄂尔多斯盆地伊陕斜坡发现多个长9烃源岩邻近的下组合含油有利区,为推进该区下组合石油勘探,亟需深化长9烃源岩特征及生烃潜力研究.利用测井、录井和岩心资料,分析研究区长9烃源岩分布特征.应用岩石热解、总有机碳、干酪根显微组分分析及饱和烃色谱-质谱生物标志化合物分析等方法,研究长9烃源岩地球化学特征与生烃潜力.结果表明,长91烃源岩在吴起、靖边、志丹、安塞等地区均有分布,厚度最大超20 m.长92烃源岩主要发育在甘泉—洛川地区,厚度最大超12 m.长9烃源岩有机质丰度较高,有机质来源于低等水生生物和陆源高等植物.有机质类型以Ⅰ型和Ⅱ1型为主,处于成熟阶段,烃源岩生烃转化率高、生烃能力较强的区域主要为志丹—安塞地区.长9烃源岩多数为较好—好烃源岩,少数为优质烃源岩,具备较强的生烃能力和排烃能力,为伊陕斜坡延长组下组合石油聚集成藏提供了物质基础.

鄂尔多斯盆地彭阳地区侏罗系延安组原油伴生气含有一定量的H2S,其成因研究对预测盆地中生界H2S的分布具重要意义.研究区侏罗系延安组原油主要来自于延长组7段(长7段)主力烃源岩,而具有相同油源的长10段—长3段原油伴生气中均未检测到H2S.因此,延安组原油伴生气中H2S的形成可能与储集和成藏因素有关.分析表明,侏罗系地层水具高矿化度且富含二价硫,抑制了硫酸盐还原菌的发育,因此生物还原硫酸盐生成H2S的可能性较小.延安组原油伴生气中H2S的δ34S值均大于25‰,明显不同于火山热液、有机质及微生物还原生成物的δ34S分布特征,而与地层水中二价硫同位素值相近,比地层水中硫酸根离子的δ34S值偏低约为10‰,具有TSR生成H2S的硫同位素分布和分馏特征.研究区侏罗系延安组储层岩石包裹体测温显示,油气初次充注温度高于100℃,最大成藏温度高达150℃,延安组地层水中含有大量的来自于硬石膏或埋藏时赋存的硫酸根离子,满足了发生硫酸盐热化学还原反应的条件,同时地层水中丰富的镁离子催化了反应的发生.因此,鄂尔多斯盆地彭阳地区侏罗系原油伴生气中H2S为TSR成因.

以长庆油田采油十二厂Z240区块NH7-1单井乳化层为研究对象,采用红外光谱、热分析、核磁共振光谱、扫描电镜能谱等仪器分析方法,全面剖析了乳化层有机组分分布与无机矿物组成,探讨了单井非常规乳化层存在的主要原因.结果表明:乳化层质量含水率53.5％,标准密度909.8kg/m3、二甲苯可溶有机组分含量43.0％,渣含量3.5％;有机组成主要为原油,胶质、沥青质含量比例较高,约10.05％～14.01％;无机组分以地层水中的氯化钠、氯化钙为主,附以少量石英、硫酸钡、碳酸钙等;乳化层还包括极少量的化学药剂,主要成分为短直链、含硝基或含氮类化学药剂.非常规乳化层存在的主要原因为压裂返排药剂与矿物颗粒分散于原油乳状液中,加之胶质、沥青质含量较高,使乳化层异常稳定,难以破乳.

为了研究鄂尔多斯盆地长7段泥页岩中高含量的沥青质组分对页岩油可流动性的影响,将一定量页岩油与过量的沥青质进行溶解试验,利用原油族组分分析检测试验前后页岩油中沥青质的百分含量,进而判断页岩油与沥青质溶解作用的强弱.研究结果表明:溶解试验前后,页岩油中沥青质的百分含量未发生明显变化,长7页岩油与泥页岩中沥青质溶解作用有限,因此泥页岩中高含量沥青质对页岩油的可流动性的影响很小.

Well X96 from the central lacustrine basin in Huachi area of Ordos Basin was selected to carry out a whole core analysis including organic carbon content,pyrolysis,gas chromatography-mass spectrometry of saturated hydrocarbons,kerogen observed under microscopy,etc.,and comprehensive geological research on hydrocarbon expulsion,accumulation,etc.,for further study on tight oil mechanism.The detailed evaluation of the geochemical characteristics of Chang-7 source rock and the relationship between high-quality source rock and tight oil accumulation using various analytical data were focused.There are three kinds of source rocks of Chang-7 from Well X9 6 , including oil shale,mudstone and silty mudstone.The oil shale has high content of organic carbon (mean content of 1 5 .8%),its organic matters are mainly amorphous mass with fine organic matter type (mainly type Ⅰ),and it is in the peak stage of hydrocarbon generation,so the oil shale belongs to the high-quality source rock.The high-quality source rock has high quantities of hydrocarbon generating,and the strong action of hydrocarbon generation expanding can provide enough energy for oil primary migration, which can cause strong hydrocarbon expulsion.As a result,the oil shale has low conversion rate of chloroform bitumen “A”,low ration of saturated hydrocarbon to aromatic hydrocarbon, and low yield index, and the hydrocarbon expulsion efficiency can more than 70%. Regionally, the oil shale is stably distributed at the bottom of Chang-7 with large-scale overlaying tight sandstone,the reservoirs contact with the source rocks directly.This kind of widely distributed high-quality source rock with large-scale and strong hydrocarbon expulsion is significant in the near-source tight oil accumulation providing both materials and powers.

页岩油是重要的非常规油气资源之一.利用地球化学、测井、X射线衍射、扫描电镜等资料对鄂尔多斯盆地延长组长7页岩油的地质特征展开了研究.研究结果表明,鄂尔多斯盆地延长组长7湖相页岩层十分发育,根据岩性组合、地球化学等特征可以将长7页岩划分为"砂岩-页岩互层"、"厚层状Ⅰ类页岩"与"厚层状Ⅱ类页岩"等三种类型.长7湖相页岩层分布范围广且厚度较大,提供了页岩油成藏的基本地质条件;岩石中脆性矿物含量高,为页岩油勘探开发的必要条件;有机质丰度高、有机质类型好且有机质热演化程度适中,奠定了页岩油聚集成藏的物质基础;虽然长7页岩十分致密,但在扫描电镜下可见微米级裂隙,并且湖盆中部等地区发育物性相对较好的薄砂岩夹层,提供了页岩油的储集空间.分析测试资料显示,长7页岩含油性较好,并具有一定的含气量;薄砂岩夹层油源充足,紫外光下具有较强的荧光显示.综合地质条件及含油气性研究,"砂岩-页岩互层"分布区被评价为最有利的页岩油勘探目标区,"Ⅰ类页岩"较"Ⅱ类页岩"生烃条件更好,脆性更强,微米级裂缝更为发育,含油气性较好,为第二类有利勘探目标区.

The extra-low permeability and tight reservoir of the Yanchang formation in Ordos Basin has small pore and tiny throat. As we all know, the lower the permeability the dis-placement pressure is greater and the median radius is smaller. The permeability of differentpermeable grade reservoir is often controlled by the levels of throat radius. The extra-low permeability and tight reservoir has non-Darcy flow seepage characteristics which means high start-up pressure gradient. Especially in the tight reservoir whose permeability is less than 0.3 mD, the start-up pressure gradient is generally greater than one MPa per meter, so the oil need larger displacement pressure to migrate. As a result of tiny throat and high cap-illary resistance, additionally the pore shape is irregular and the clay was enriching on min-eral particle and throat surface, and the specific surface area is large, and the frictional re-sistance was large when the oil flow through, so the gravitational differentiation of oil and water which relied on natural buoyancy is difficult occur in the extra-low permeability and tight reservoir and the oil can’t free migrate in separate phase that relied on gravity differ-ence, then hydrocarbon need to be driven to migrate by external force. The Chang7 high quality source rocks has high rate of hydrocarbon production and hydrocarbon expulsion. Be-cause the hydrocarbon volume expansion during hydrocarbon generation process was obvious, so superpressure generated, which was the primary driving force for migration of the extra-low permeability and tight reservoir of the Yanchang formation in Ordos Basin.

For thick-bedded argillaceous rock of Upper Paleozoic,Ordos Basin,its geochemical,petrological,and gas-bearing characteristics,and physical properties are analyzed.Results show that(1) the Upper Paleozoic Shanxi 2 Member of Shanxi Formation is composed of thick-bedded argillaceous rock with wide distribution area and large thickness;(2) with humic type as the main organic-matter one,its organic-matter abundance is higher;(3) its maturity is higher,and also it is a favorable region to form shale-gas reservoir;(4) in the argillaceous rock,there are a lot of quartz with stronger brittleness;and(5) its porosity and permeability are low,meanwhile some microfractures can be found.After many experiments of isothermal adsorption,gas-bearing saturation measurement,porosity measurement,and gas analysis of bulking samples from field coring,the total gas-bearing volume of argillaceous rock is determined.Finally,favorable regions to form Upper Paleozoic shale-gas reservoir are pointed out and their resource extent is calculated.

The geochemical features, origin and genesis are studied systematically by using group composition, stable carbon isotope and saturated hydrocarbon analysis. The results show that oil is typical lacustrine-derived oil, with δ13CPDB value generally from -32.79 ‰～-30.69 ‰ . Sterane and terpane biomar kers of compounds in oil from the region and source rock from Ordos basin were systematically analyzed. The oil contains a certain amount of pregnane, homo-pregnane, rearranged sterane and enriches αβ and βα isomers,while ααα-20R sterane isomers display an asymmetric "V"type distribution pattern. Its terpane distribution is characterized by high content of pentacyclic terpane, low content of gammacerane and there are significant differences in relative abundance of 17α (H)-diahopanes. The biomarker distributions of the oils show that they were formed under a weak reducing and fresh water environment. The results of oil-source rock correlation showed that the oil was mainly derived from Chang-7 source rock.

The basic principle of using gas chromatographic finger print technique in reser-voir development was that the changes of full hydrocarbon gas chromatographic fingerprint were representations of heterogeneity of oil. The gas chromatography fingerprint technique was applied to understanding of oil layers connectivity of chang 6 oil of a certain area in Ordos Basin. According to the chromatographic fingerprint parameters, the oil of studied area can be divided into five types: Ⅰ-Ⅳ types and the special type. Except for the special type oil, the oil of same type was basically in agreement with reservoir sand distribution charac-teristics and was in good connectivity. There was difference in oil layer connectivity and preservation condition among different sandbodies. The results of the well logging, testing for oil, and layering data shows that crude oil chromatographic fingerprint technology was a re-liable method in researching connectivity of layers.

对采自鄂尔多斯盆地延长组的8块渗透率为(0.050～2.812)×10-3μm2的特低渗—致密砂岩岩芯样品进行石油驱替成藏模拟试验.试验采用驱动压力分段逐级提升式连续油相充注.结果表明:特低渗—致密砂岩储层石油运移、聚集、成藏机理与常规储层明显不同.随着石油不断注入和驱动压力的不断增高,岩芯中孔隙水逐渐排出,含油饱和度随之增高,并且增高趋势呈现先快后慢的指数式特征;样品最终含油饱和度与渗透率相关关系不显著,与孔隙度呈正相关;特低渗—致密储层具有原油活塞式驱替运移的成藏机理,成藏效率高,石油成藏富集受到油源规模、驱动压力、成藏流体性质等因素的影响;优质烃源岩是特低渗—致密储层石油富集的主控因素.

Chang 8 oil reservoir is one of the most important hydrocarbon accumulation horizons in Jiyuan region of Ordos Basin.However,the research on genesis of the oil is still known little.In this paper,sterane and terpane biomarkers of compounds in oil from the region and source rock from Ordos basin were systematically analyzed.The oil is typical lacustrine-derived oil,with d13CPDB value generally from-31.11 ～-31.57‰.Its terpane distribution was characterized by relatively abundant 17α(H),21β(H) – hopanes.The relative content of C29 hopane of Chang 8 oil in NE migration-accumulation zone was higher,C29Ts takes second.The relative content of C30 rearranged hopane in SW migration-accumulation zone is higher,C30* hopane / C29 norhopanes is greater than 1.The oil contains rich pentacyclic triterpanes,a certain amount of pregnane,homo-pregnane,rearranged sterane and enriches αβ and βα isomers,while ααα-20R sterane isomers display an asymmetric "V"type distribution pattern.The biomarker distributions of the oils show that they were formed under a weak reducing and fresh water environment.The results of oil-source rock correlation showed that the oil was mainly derived from Chang-7 source rock.

The Chang 10 oil reservoir was discovered through the exploration in the Zhidan region of Ordos Basin, where the crude shows a density of 0. 8152 g /cm3 and a main peak at nC15 in the whole hydrocarbon chromatogram. The crude consists mainly of light hydrocarbons, which include abundant naphthenic hydrocarbons and low content of aromatic hydrocarbons, and has an equilibrial ratio of Pr / Ph, varing from 1. 21 to 1. 45, and - 31. 78‰ of δ13CPDB for the whole crude. Its terpane distribution is characterized by relatively abundant rearranged hopanes, low content of gammacerane, and high ratios of Ts /Tm (5. 54 - 7. 26), C30* /C30 hopane (0. 67 - 0. 72), and C29Ts / C30 hopane (0. 38 - 0. 52). The steranes in the crude mainly consist of rearranged steranes, and show abundant αβ and βα isomers, while ααα-20R sterane isomers display an asymmetricVtype distribution pattern, representing a typical lacustrine-derived oil. The oil-oil and oil-source correlations indicate that the crude oil of Chang 10 oil reservoir is originated from the excellent hydrocarbon source rocks of the Chang 7 member in the center of the basin, and migrated vertically into the Chang 10 oil layer, and then accumulated laterally. Therefore, it can be predicted that the Chang 9 and Chang 10 oil reservoirs in the Ordos Basin have favorable reservoir-forming conditions and great potential for exploration.

The oil source rocks of the Chang 7 member of the Yanchang Formation in the Erdos Basin were deposited during maximum lake extension during the Late Triassic and show a remarkable positive uranium anomaly, with an average uranium content as high as 51.1μg/g. Uranium is enriched together with organic matter and elements such as Fe, S, Cu, V and Mo in the rocks. The detailed biological markers determined in the Chang 7 member indicate that the lake water column was oxidizing during deposition of the Chang 7 member. However, redox indicators for sediments such as S2− content, V/Sc and V/(V+Ni) ratios demonstrate that it was a typical anoxic diagenetic setting. The contrasted redox conditions between the water column and the sediment with a very high content of organic matter provided favorable physical and chemical conditions for syngenetic uranium enrichment in the oil source rocks of the Chang 7 member. Possible uranium sources may be the extensive U-rich volcanic ash that resulted from contemporaneous volcanic eruption and uranium material transported by hydrothermal conduits into the basin. The uranium from terrestrial clastics was unlike because uranium concentration was not higher in the margin area of basin where the terrestrial material input was high. As indicated by correlative analysis, the oil source rocks of the Chang 7 member show high gamma-ray values for radioactive well log data that reflect a positive uranium anomaly and are characterized by high resistance, low electric potential and low density. As a result, well log data can be used to identify positive uranium anomalies and spatial distribution of the oil source rocks in the Erdos Basin. The estimation of the total uranium reserves in the Chang 7 member attain 0.8×108t.

The Triassic Yanchang Formation is an important reservoir in Changqing Oilfield,with obvious starting pressure phenomenon.After the discussion on the cause,it is believed that the phenomenon was resulted from multi-factors.The analysis testing is carried out in Houshi area,and the result shows that the Triassic Yanchang Formation in Houshi area has obvious startingpressure,with a startingpressure gradient of0.327 MPa/m.

Starting with the six aspects such as formation temperature,formation water salinity,depositional rate,organic matter abundance and type,microbial population and shallow inhibition effect,this paper analyzes in detail each factor influencing the microbial activity,the growth and reproduction of methane bacteria and the generation of biogas of the Neogene-Quaternary in Hetao basin.It is revealed that the favorable layer of biogas source rock development lies to the upper and middle sections of the Pleistocene in Hetao basin.

The core of Yanchang Formation Chang-7 high quality source rock (oil shale) is black,hard,light,and it looks slip-shape after demorphism. Rock slice observation and SEM-energy spectrum test show that the Chang-7 high quality source rocks are characterized by the extraordinary development of organic matter laminas,being rich in framboidal pyrite and abundant cellophane,and crystal fragment and tuff laminae are often observed. Comprehensive test results reveal that the chemical compositions of Chang-7 high quality source rock are characterized by high S2-,Fe,P2O5 contents and relatively low Al2O3,SiO2,CaO and MgO contents. In trace elements,Mo,Cu and U are obviously positive anomalies,V and Pb are positive anomalies,and the others are no or negative anomalies. ∑ REE is low. Low Sr/Ba ratios and B content reflect nonmarine lake-basin deposition feature with little salinity. Some geochemical parameters,such as high V/(V+ Ni) and very high U/Th ratios,indicate anoxic sedimentary environment.

The analysis of natural gas composition and carbon isotopes of methane confirms the existence of biogenic gas around the Tertiary Pliocene series and the Quaternary Pleistocene series in the Hetao basin. Detailed organic geochemistrcal data shows that the biogenic gas source rock of the middle and upper Pleistocene series in this area contains a high content of organic matters and typesⅡ2 and Ⅲ kerogens. The organic matter in the biogenic gas source rock is in low-mature stage, which is benefit for the formation of biogas. In addition, this article establishes a generation-evolution model of biogas, taking into account the region geology feature and temperature affection on the biogas generation, and puts forward that the best vertical extent for biogenic gas formation in the Hetao basin is in the middle of the Quaternary Pleistocene series, between 685 meters and 926 meters.