Diagenesis and Restructuring Mechanism of Oil and Gas Reservoir in the Marine Carbonate Formation,Northeastern Sichuan:A Case Study of the Puguang Gas Reservoir

Abstract: Based on the technology of balanced cross-section and physical simulation experiments associated with natural gas geochemical characteristic analyses, core and thin section observations, it has been proven that the Puguang gas reservoir has experienced two periods of diagenesis and restructuring since the Late Indo-Chinese epoch. One is the fluid transfer controlled by the tectonic movement and the other is geochemical reconstruction controlled by thermochemical sulfate reduction (TSR). The middle Yanshan epoch was the main period that the Puguang gas reservoir experienced the geochemical reaction of TSR. TSR can recreate the fluid in the gas reservoir, which makes the gas drying index higher and carbon isotope heavier because C2+ (ethane and heavy hydrocarbon) and 12C (carbon 12 isotope) is first consumed relative to CH4 and 13C? (carbon 13 isotope). However, the reciprocity between fluid regarding TSR (hydrocarbon, sulfureted hydrogen (H2S)?, and water) and reservoir rock results in reservoir rock erosion and anhydrite alteration, which increases porosity in reservoir, thereby improving the petrophysical properties. Superimposed by later tectonic movement, the fluid in Puguang reservoir has twice experienced adjustment, one in the late Yanshan epoch to the early Himalayan epoch and the other time in late Himalayan epoch, after which Puguang gas reservoir is finally developed.     

三角帆蚌(Hyriopsis cumingii)珍珠钙代谢的周年性变化研究

采用生态调查和生理生化方法,对植片后的1龄三角帆蚌(Hyriopsis cumingii)进行了为期一年的调查研究,拟探讨珍珠形成和钙代谢的相关性。定期测定珍珠囊和珍珠的重量、直径及水温,同时取其鳃、围心腔和外套膜组织进行酸、碱性磷酸酶活性检测及钙含量等测定。结果表明,1龄植片后的三角帆其蚌珍珠囊和珍珠在一周年之中出现三次快速生长期。外套膜中的酸、碱性磷酸酶均在165d时升至最高。鳃组织中钙含量显著高于围心腔和外套膜。经Pearson相关分析显示,珍珠囊和珍珠的重量、直径分别与三种组织中的碱性磷酸酶活性及外套膜中的钙含量呈显著性正相关(P<0.05);同时,外套膜中的钙含量与三种组织中的碱性磷酸酶呈显著性正相关(P<0.05);水温与外套膜、围心腔中的钙含量呈显著性负相关(P<0.05),与三种组织中的酸性磷酸酶呈显著性正相关(P<0.05)。提示:鳃是三角帆蚌钙吸收、贮存和钙调节的重要器官,形成珍珠的钙一部分来源于循环系统,另一部分可由外套膜直接从环境中吸收,碱性磷酸酶对珍珠生长起着重要的调节作用。     

东营凹陷民丰地区深部储层成岩环境变化研究

通过薄片鉴定、激光拉曼光谱分析、全岩和粘土矿物分析以及流体包裹体测试等手段,结合埋藏史分析,研究了东营凹陷民丰地区深部储层成岩环境的特点。分析认为,东营凹陷民丰地区深部储层成岩现象丰富,表现出不同成岩环境相叠合的特征,存在酸性、碱性和酸性碱性交替等多重成岩环境。着重利用不同成岩环境代表矿物中的流体包裹体分析成岩环境的变化,结果显示,3 000~3 200 m是碱性流体活动的重要深度。东营凹陷民丰地区深部储层在埋深过程中由浅到深大致经历了（弱）碱性（小于1 750 m）→酸性（1 750~3 200 m）→酸碱交替（3 200~4 000 m）→碱性（4 000~5 000 m）→弱碱性到弱酸性（大于5 000 m）多重成岩环境的变化,从而形成了现今复杂的成岩现象。埋深和温度是成岩环境变化的宏观主导因素,但并非绝对控制因素,局部流体性质的变化更能直接导致成岩环境的变化。     

胶莱盆地莱阳凹陷莱阳组储层成岩作用及孔隙演化

以野外露头、岩心观察为基础,综合采用普通薄片、铸体薄片、阴极发光薄片、扫描电镜、物性分析、黏土矿物X衍射等多种测试手段对胶莱盆地莱阳组砂岩储层特征、成岩作用及孔隙演化进行了研究。研究结果表明：受物源差异影响,凹陷东部以长石砂岩为主,凹陷西部以岩屑砂岩为主,富含各种塑性岩屑,莱阳组砂岩总体以低成分成熟度、中等结构成熟度为特征。压实作用、压溶作用和胶结作用是造成砂岩储层致密的主要原因。凹陷东部以胶结作用减孔为主,压实程度较弱,碳酸盐胶结物是造成砂岩孔隙度降低的主要胶结物。凹陷西部以压实作用为主,但绿泥石薄膜胶结物的存在有利于保存部分原生孔隙。莱阳组砂岩储层原生孔隙残留较少,多以次生孔隙为主。溶蚀作用,尤其是长石的溶解作用,对改善储层物性有重要作用。次生孔隙发育带主要在K₁llw、K₁ls中,成岩演化达中成岩A期,溶蚀型次生孔隙成为这一阶段主要的孔隙类型,其发育带往往是有利储层发育区。     

菲律宾蛤仔碱性磷酸酶的分离纯化及部分性质研究

经Tris-HCl缓冲液浸提、硫酸铵分级沉淀盐析、DEAE-Sepharose Fast Flow离子交换层析和Sephadex G-75凝胶过滤层析等步骤,从菲律宾蛤仔内脏团中分离得到碱性磷酸酶,SDS-PAGE显示为单一条带,提纯倍数为14.42,比活力达到131.08U/mg。酶学性质研究表明:该酶亚基分子量约44kD,最适反应温度为45℃,最适pH值为9.0,米氏常数Km为0.098mmol/L,最大反应速度Vmax为1.01μmol/(mL·min)。Ca2+、Mg2+对酶活力表现出显著的激活作用。     

辽东湾旅大地区古近系成岩作用与储集层孔隙关系研究

辽东湾旅大地区古近系储层砂岩类型主要为长石砂岩和岩屑长石砂岩,岩屑成分主要为岩浆岩和较多的变质岩.胶结类型以孔隙式胶结为主,孔隙类型以次生孔隙为主.砂岩成岩作用包括压实作用、胶结作用、溶蚀作用等,其中胶结作用使储层原生孔隙迅速变差,而溶蚀作用是次生孔隙发育的主要因素.成岩作用对砂岩储集层的孔隙结构起着显著的改造作用,孔隙度演化与成岩阶段有较好的对应关系.     

地壳再循环与大陆碱性玄武岩的成因：以山东新生代碱性玄武岩为例

      大陆碱性玄武岩在地球化学特征上与洋岛玄武岩高度相似,被看做是板内玄武岩在大陆上的典型代表。本文以山东 新生代碱性玄武岩为例,探讨大陆碱性玄武岩的成因。山东新生代碱性玄武岩按时空分布特征可以分为两类：早期定向分 布、相互平行的三个火山群（包括鲁西的潍坊火山群、沂水火山群和胶东的蓬莱火山群）和晚期杂乱分布的孤立小火山。 早期火山群碱性较弱,以碱性橄榄玄武岩和碧玄岩为主,微量元素特征和同位素组成变化大;晚期孤立小火山碱性强,以 碧玄岩和霞石岩为主,微量元素特征和同位素组成较均一。因此,从岩性组成和时空分布特征看,山东的火山群相当于洋 岛/海山的造盾期玄武岩,而孤立小火山接近于洋岛/海山上的复苏期玄武岩。潍坊火山群和沂水火山群在Sr-Nd,Nd-Hf同位 素相关图上都存在从亏损到富集的两端元混合排列趋势,但两者的排列趋势有一点区别。其中同位素富集的端元相对于原 始地幔具有偏低的Ce/Pb比和偏高的Ba/Th比,指示其为大陆下地壳物质。同时,这种富集端元的Th/La比值明显低于大陆下 地壳的平均值,其放射成因Hf相对于放射成因Nd过剩（即Nd-Hf同位素解耦）,说明这种富集端元不是岩浆上升过程中混染 的下地壳物质,而是经历过早期熔融的再循环大陆下地壳（榴辉岩或者石榴辉石岩）。鲁西两个平行火山群在同位素排列上 的区别类似于夏威夷玄武岩中的KEA链和LOA链,因此,山东的平行火山群的深部动力学背景可能是地幔柱,再循环大陆 下地壳物质可能是这种地幔柱的重要组成物质。晚期的孤立小火山在地球化学特征上与火成碳酸岩非常相似,如在原始地 幔标准化图上都具有K,Pb,Zr,Hf,Ti的负异常等特征,因此我们认为其地幔源区为碳酸盐化的橄榄岩。孤立小火山中等亏损 的Sr,Nd,Hf同位素特征支持碳酸岩熔体来自年轻的（中生代？）再循环洋壳。     

Encounters with an unearthly mudstone: Understanding the first mudstone found on Mars

The Sheepbed mudstone forms the base of the strata examined by the Curiosity rover in Gale Crater on Mars, and is the first bona fide mudstone known on another planet. From images and associated data, this contribution proposes a holistic interpretation of depositional regime, diagenesis and burial history. A lake basin probably received sediment pulses from alluvial fans. Bed cross‐sections show millimetre to centimetre‐scale layering due to distal pulses of fluvial sediment injections (fine‐grained hyperpycnites), fall‐out from river plumes, and some aeolian supply. Diagenetic features include mineralized synaeresis cracks and millimetre‐scale nodules, as well as stratiform cementation. Clay minerals were initially considered due to in situ alteration, but bulk rock chemistry and mineralogy suggests that sediments were derived from variably weathered source rocks that probably contained pre‐existing clay minerals. X‐ray diffraction analyses show contrasting clay mineralogy in closely spaced samples, consistent with at least partial detrital supply of clay minerals. A significant (ca 30 wt%) amorphous component is consistent with little post‐depositional alteration. Theoretical modelling of diagenetic reactions, as well as kinetic considerations, suggest that the bulk of diagenetic clay mineral formation occurred comparatively late in diagenesis. Diagenetic features (synaeresis cracks and nodules) were previously thought to reflect early diagenetic gas formation, but an alternative scenario of synaeresis crack formation via fabric collapse of flocculated clays appears more likely. The observed diagenetic features, such as solid nodules, hollow nodules, matrix cement and ‘raised ridges’ (synaeresis cracks) can be explained with progressive alteration of olivine/glass in conjunction with centrifugal and counter diffusion of reactive species. Anhydrite‐filled fractures in the Sheepbed mudstone occurred late in diagenesis when fluid pressures built up to exceed lithostatic pressure. Generating fluid overpressure by burial to facilitate hydraulic fracturing suggests a burial depth of at least 1000 m for the underlying strata that supplied these fluids.     

Formation of chlorite rims and the impact of pore-lining chlorite on reservoir quality: a case study from Shiqianfeng sandstones in upper Permian of Dongpu Depression,Bohai Bay Basin,eastern China

The source material, precursor and formation processes of chlorite rims, and impact of pore-lining chlorite on reservoir quality of the Shiqianfeng sandstones, Dongpu Depression, Bohai Bay Basin, China, are studied using an integrated approach, including core observation, point-count analysis of thin-sections, scanning electron microscopy, electron microprobe analysis and cathode luminescence. The petrographic analysis shows that chlorite rims consist of grain-coating chlorite, poorly crystalline pore-lining chlorite and euhedral-crystallised pore-lining chlorite. The chemical composition shows that pore-lining chlorite is mainly Fe-rich with an average of 0.785 for Fe/(Fe+Mg) ratio. Petrographic analysis shows a large amount of volcanic dust (3.0～16.0 vol%, average of 7.93 vol%) in Shiqianfeng sandstones, which determines the formation of poorly crystalline pore-lining chlorite. Transformation of volcanic dust to smectite rims started with shallow burial depth at an early diagenetic stage, followed by in situ alteration of the smectite rims to poorly crystalline chlorite rims. Euhedral-crystallised chlorite mainly develops in sandstones with high porosity, high permeability and open flow systems. Pore-lining chlorite can inhibit quartz overgrowth but cannot effectively prevent pore-filling of authigenic quartz, carbonate and kaolinite cements, and therefore cannot prevent porosity destruction. However, the occurrence of pore-lining chlorite is a barometer of good reservoir quality and intense hydrodynamic conditions.     

Diagenetic Evolution and Formation Mechanisms of High-Quality Reservoirs under Multiple Diagenetic Environmental Constraints: An Example from the Paleogene Beach-Bar Sandstone Reservoirs in the Dongying Depression, Bohai Bay Basin

The diagenetic environment, diagenetic responses, diagenetic transformation model and formation mechanisms of high-quality reservoirs (beach-bar sandstones of the Paleogene fourth member) in the Dongying depression were studied through the analysis of fluid inclusions, thin section and burial evolution history. The diagenetic fluids of the beach-bar sandstone reservoirs evolved from early high salinity and weak alkalinity to low salinity and strong acidity, late high salinity and strong alkalinity and late low salinity and acidity, which were accompanied by two stages of oil and gas filling. The fluids at the margins of the sandbodies were continuously highly saline and strongly alkaline. The western (eastern) reservoirs experienced early open (closed), middle open, and late closed diagenetic environments during their burial history. The flow pattern was characterized by upwelling during the majority of the diagenesis (in the east, a non-circulating pattern transitioned into an upwelling current). Due to the evolution of the diagenetic fluids, the diagenetic sequence of the beach-bar reservoirs was as follows: early weak carbonate cementation; feldspar and carbonate cement dissolution and authigenic quartz cementation; late carbonate and anhydrite cementation, authigenic feldspar cementation, and late quartz dissolution; and late carbonate cementation, feldspar dissolution, and authigenic quartz cementation. The diagenetic strength during these stages varied or was absent altogether in different parts of the reservoirs. Due to the closeness of the diagenetic environment and the flow pattern of the diagenetic fluids, the diagenetic products are variably distributed in the sandstones interbedded with mudstones and in the fault blocks. The evolution of multiple alternating alkaline and acidic diagenetic environments controlled the distribution patterns of the reservoir diagenesis and reservoir space, and the reservoir quality index, RQI, increased gradually from the margins to the centers of the sandstones. The closeness of the diagenetic environment and the flow patterns of the diagenetic fluids controlled the differences in the reservoir properties among the fault blocks. With increasing distance from the oil-source faults, the RQI values in the west gradually decreased and in the east initially increased and then decreased.