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.

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.

The oil detailed classification and oil-source correlation are important topics for organic geochemistry in petroliferous basins.Analysis with GC-MS reveals that the relative abundances of 17α(H )-C30 diahopanes (C?30 )are various both in Mesozoic Yanchang Formation lacustrine source rocks and oils of Ordos Basin.Correspondingly,the contents of rearranged sterane,C2 9 Ts and Ts are also different.Therefore,according to the abundance of C?30 ,such as the diagrams of C?30/C2 9 norhopane value-C?30/C30 hopane value and C2 9 Ts/C2 9 norhopane value-C?30/C30 hopane value,the Mesozoic lacustrine oil can be divided into three genetic types including exceptional richness of C?30 ,relative richness of C?30 and lower C?30 contents.By studying the distribution of sterane and terpane biomarkers in oil-source rock with relevant parameters,and carbon isotopic compositions of monomer hydrocarbon,based on source rock distribution and reservoir forming combination,it has been proved that Chang-7 high-quality sources are the main oil source rocks in Mesozoic reservoirs of Ordos Basin,and the black mudstones of Chang-7 and Chang-9 are the secondary source rocks,while the contribution of dark mudstone of Chang-6 and Chang-8 is limited.In conclusion,the Mesozoic oil supply is characterized by “one source is dominating, multiply sources are participated”.This study is significant in Mesozoic resource assessment and further exploration of 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.

评价已开发油田或区块可采储量的方法有很多,究竟采用哪种方法评价采储量,一方面取决于被评价单元所处开发阶段及拥有资料的齐全程度,另一方面要充分考虑各种评价方法的适用条件。对于同一个单元而言往往适用的方法很多,但只有精度最高方法的测算结果才能作为最终的标定选值,其它方法评价结果通常用于对比分析。相关研究表明,当条件均适用的情况下,动态法评价结果精度要高于静态法。为此,本文以注水开发较早,注水状况较好的贝301区块南屯组油层为例,应用动态法进行了评价,并与以往静态法标定结果进行了对比分析,以期更客观的反映该区块的可采储量,也为动态法在海拉尔油田可采储量评价中全面应用提供借鉴。

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.