Organic geochemistry and source rock potential assessment of Late Paleocene Patala Formation in Margalla Hill Range,North Pakistan

Black shales of the Paleocene Patala Formation are proven source rocks for conventional hydrocarbons in southern Potwar Basin of Pakistan and are assumed to be effective source rocks towards north in the Margalla Hill Range of Pakistan. In this regard, the current study focuses on source rock geochemistry of the Paleocene Patala Formation to assess its source rock potential, organic matter types and thermal maturity levels in the Mar-galla Hill Range of North Pakistan. Source rock generative potential, kerogen types and thermal maturation of the analysed rock samples were unraveled by using Rock-Eval pyrolysis Tmax, TOC (total organic carbon) and vitrinite reflectance ( R0 ) analyses. TOC analysis coupled with S2 yield revealed poor to fair source rock quality encountered within the formation. The pyrolysis Tmax vs Hydrogen Index ( HI) , showed mostly Type Ⅲ kerogen dominated by thermally immature to mature organic matter. The HI and genetic potential is low and revealed poor hydrocarbon generation potential of the formation. The S1 vs TOC plots confirm the indigenous nature of the hydrocarbons hosted by Patala Formation. The vitrinite reflectance outcomes indicated immature to mature source rock beds lying in dry gas zone. The HI and OI signatures and abundance of Type Ⅲ kerogen are indica-ting dominance of terrestrial organic matter within the formation. Overall, the investigated Patala Formation ex-posed at the studied section of Margalla Hill Range, Pakistan acts as a poor source rock unit for liquid hydrocar-bon generation but holds prospects for dry gas generation in the study area.     

小波分析在天然地震初震及震相识别中的应用

地震灾害给人类带来了很大的伤害,为了有效地减轻地震灾害,加强地震监测非常必要的。为了达到理想的地震监测效果,需要对地震波初震和震相进行准确的识别。主要研究小波分析方法在初震和震相识别中的应用,先用小波包变换确定信号的初动位置,再用小波变换分解信号,分离出信号不同频率所对应在信号中的不同位置,从而确定信号的初动时间和相应的震相。通过该方法对模拟信号和实际天然地震信号进行处理,有效的识别了天然地震初震及其震相。     

中央亚洲活动带多岛海地质演化与砂岩型铀矿时空定位模式

中央亚洲活动带是世界上重要的铀成矿带之一,我国的天山-阴山-燕山以北地区正处于此带内。文章以成熟陆壳控矿理论和多岛海地质构造演化理论为基础,在系统分析该成矿带不同构造单元古生代岩石地球化学特征及其反映的大地构造属性的基础上,探讨了该带地壳成熟度及其对后期砂岩型铀矿成矿作用的影响,并建立了相应的砂岩型铀矿时空定位模式。     

Determination of partial factors for the verification of the bearing capacity of shallow foundations under open channels

The limit state design method has been introduced into the design criteria for geotechnical structures. The current paper attempts to apply the reliability-based design method, at Level II, to the bearing capacity of the foundations of open channels from the viewpoint of the limit state design. To examine the applicability of the proposed procedure for practical structures, the reliability index is computed for evaluating the stability of the foundations of existing open channels designed by the conventional method. The conventional design procedure makes excessively safe side design. We applied the FORM to the existing open channels designed by the conventional design procedure, and consequently, large values of reliability index, 3 and 5 were obtained for clayey and sandy soils, respectively. Finally, the partial factors for the soil parameters have been determined, corresponding to the target reliability indices β _t =1, 3 and 4.     

基于数值模拟对一次广西前汛期回流暴雨形成机制的分析

使用WRF对发生在2010年4月28—29日一次广西前汛期回流暴雨过程进行了数值模拟,并通过诊断分析,研究了回流暴雨的形成机制。结果表明：冷空气受南岭、武夷山脉阻挡未能直接影响华南西部,其东移入海后,华南西部处入海高压后部,等压线呈“东南—西北”向,低层风向顺转为东南风,由于经南海回流的东南气流相对于孟加拉湾西南气流和越赤道气流是干冷的,不同性质气流汇合形成锋面、辐合线,提供了抬升条件,这是回流形势的形成过程;从θe和湿位涡诊断发现,边界层条件性对称不稳定和中低层对流性不稳定是此次暴雨中尺度对流系统发生发展的不稳定机制;边界层辐合和能量锋锋生是暴雨的主要触发条件;在暴雨增幅前不稳定能量有一个积累过程,边界层能量锋锋生和辐合抬升促使不稳定能量释放,使暴雨增幅;湿位涡负异常对暴雨预报具有指示意义,水平螺旋度正值增大与暴雨增幅有较好的对应关系;此次回流暴雨发生在边界层锋的两侧,边界层存在锋区表明此次回流暴雨在基本性质上仍属锋面降水。     

Geochemical characteristics of Ordovician crude oils in the northwest of the Tahe oil field,Tarim basin

Forty-six crude oil samples were selected from the Ordovician in the northwestern part of the Tahe oilfield for detailed molecular geochemical and isotopic analysis, including group compositions, carbonhydrogen isotopes and gas chroma-tograms of saturated hydrocarbons, as well as the characteristics of terpane, sterane and other biomarkers, indicating that crude oils are of the same origin from different districts in the Tahe oilfield and were derived from the same source kitchen (or oil source formation), i.e., mainly stemming from marine hydrocarbons. Detailed studies of oil physical properties of 25-honpane revealed that such oils have heavy or thick oil qualities due to biodegradation. Comprehensive assessment in terms of five maturity parameters shows that the oils from the Ordovician with Ro values varying from 0.80% to 1.59% are widely distributed in the northwest of the Tahe oilfield.     

吐哈盆地生物气-低熟气评价的元素平衡法及其应用

吐哈盆地探明的源于非高温热成因天然气(生物气—低熟气)的储量虽然已近千亿方,但尚未见评价其生成量及资源量的有效方法报道,这影响了对其勘探潜力及有利目标的决策。针对这一难题,考虑到无论生物气、低熟气的生成机理如何,都是一个有机元素之间的物质平衡过程,探索并建立了评价生物气—低熟气生成量的元素平衡法。利用吐哈盆地大量的实际分析数据,对这一评价方法(模型)进行了标定和应用。结果表明,吐哈盆地Ⅱ型有机质产生物气—低熟气的成气率高于Ⅲ型,二者分别累计可达134.40 ml/g和83.99 ml/g,吐哈盆地生物气—低熟气的生成总量约为1 436.28×1012 m3;资源量可能介于7.09×1011～24.42×1011m3之间。表明吐哈盆地的非高温热成因气具有较大的勘探潜力。台北凹陷的J2x和J1及其附近层位是勘探的有利目标。     

准噶尔盆地玛西斜坡低饱和度油藏微观赋存状态及高含量胶质和沥青质成因

低饱和度油藏中存在明显可动水,明确低饱和度油藏的孔隙分布及不同尺度孔隙中石油微观赋存状态是认识低饱和度油藏特征的关键。利用原油性质、荧光薄片、铸体薄片及试油试采资料等对准噶尔盆地玛西斜坡八道湾组一段低饱和度油藏的微观赋存状态进行研究。研究表明：1）玛西斜坡侏罗系八道湾组一段低饱和度油藏为轻质原油,原油组分主要有油质和胶质—沥青质两种类型,而三叠系百口泉组原油组分主要为油质组分,八道湾组一段原油组分具有“高含量胶质—沥青质、低含量油质”的特征。2）玛西斜坡八道湾组一段为低孔低渗储层,储层孔隙结构较差,主要发育原生粒间孔、次生粒内溶孔和微裂缝,其中原生粒间孔为大孔,次生粒内溶孔为小孔,原生粒间孔对于储集物性的贡献占主导地位。3）玛西斜坡八道湾组一段低饱和度油藏储层中原生粒间孔富含油质,发育微裂隙的粒内溶孔也富含油质,而次生粒内溶孔和晶间孔富含胶质和沥青质。4）八道湾组一段低饱和度油藏经历了早期充注、晚期调整的过程,早期充注在大孔中的油质组分由于分子链小而逸散,而大分子链的胶质和沥青质在小孔的粒内溶孔和晶间孔中富集,形成了高含量的胶质和沥青质。结论认为：高含量胶质和沥青质加剧了砂砾岩储层的非均质性,为八道湾组一段的油藏成藏调整提供了侧向封堵条件,被胶质和沥青质影响的小孔中存在共存水,随着油藏的开发,大孔中的轻质油和小孔中的共存水一起被开采出来,表现出油水同出的生产特征。

     

涠洲岛海域美丽鹿角珊瑚和秘密角蜂巢珊瑚的性腺发育研究

性腺发育是造礁珊瑚有性繁殖的重要过程,珊瑚会在性腺发育成熟后待环境适宜时进行大规模排卵。了解造礁珊瑚的性腺发育过程对预测其排卵时间具有重要的意义,但目前尚未有关于涠洲岛海域造礁珊瑚性腺发育的报道,且该海域造礁珊瑚的排卵时间也不明确。因此,本文于2021年9月至2022年5月,以涠洲岛海域的美丽鹿角珊瑚（Acropora formosa）和秘密角蜂巢珊瑚（Favites abdita）为研究对象,观察其在自然海域的性腺发育过程及排卵时间。结果显示,在自然海域美丽鹿角珊瑚的卵母细胞从9月开始发育,约经9个月发育成熟,精巢从11月开始发育,经2～3个月成熟;秘密角蜂巢珊瑚的卵母细胞在10–11月间开始发育,经7～8个月发育成熟,精巢发育周期为1～2个月;2种珊瑚的配子均在2022年5月份同步成熟,并于2022年5月19–22日（农历四月十九至二十二日）间观察到了室内2种珊瑚的排卵行为,与其在自然海域的排卵时间基本一致。基于上述证据,本文推测涠洲岛海域美丽鹿角珊瑚和秘密角蜂巢珊瑚主要的排卵时间在农历四月十五日前后。本研究为涠洲岛造礁珊瑚的繁殖生物学提供了宝贵的信息,为进一步利用其有性繁殖进行珊瑚礁的生态修复等提供了理论依据。     

辽河盆地西部凹陷未熟油的成藏条件

钻探结果表明,在辽河盆地西部凹陷北部及中南部沙河街组四段、三段中浅层储层中均见到了一定数量的未熟原油,探明储量也很可观。从原油生成、运移聚集成藏特征等几个方面进行了较为详细地分析。认为未熟油在成藏的整个过程中,主要受到源岩沉积环境、运移通道及构造活动所控制,是特定条件下的产物,其成藏规模受未熟源岩的排烃数量以及储集岩体物性条件所制约,与成熟油藏比较,既有相似之处又有一定的差异性。随着油区勘探程度的提高和研究的不断深入,岩性构造型未熟油藏才逐步被人们所认识。因此,开展此项研究无疑对拓宽油气勘探领域具有一定的指导意义。