Middle Permian Mixed Siliciclastic-Carbonate System on the Northwestern Margin of the Indian Plate,Pakistan:Implications for Paleoclimate and Carbonate Platform Evolution

A mixed siliciclastic-carbonate system that responds to changes in Permian climate and subsequent carbonate platform evolution is investigated using microscopic details of the Middle Permian Amb Formation(Fm.),in Saiyiduwali section,Khisor Range,northern Pakistan.Thin sections were made from rocks throughout the stratigraphic section of the Amb Fm.and analyzed with an emphasis on carbonate and clastic microfacies,and the latter interpreted within the existing chronostratigraphic framework.Outcrop observations reveal that the units comprise coarse-grained,channelized,ripplemarked,and burrowed sandstone and sandy,fossiliferous limestone with minor marls and shale intercalations,suggesting deposition in a subaqueous tide-dominated delta to beach barrier.Based on the determined seven microfacies coupled with outcrop observation,the Amb Fm.was deposited in a tide-influenced subaqueous delta to middle shelf environment under fluctuating sea level.The deposition of compositionally mature sandstone in the lower part of the formation suggests reworking of detritus from the rift shoulders and an adjacent source area with an ambient warm and humid climate.The stratal mixing of carbonates and compositionally mature siliciclastic units in the middle part suggest deposition under tectonic and climate-induced terrigenous and carbonate fluxes to the basin.Thus the deposition shows a perfect transition from clastic-dominated deltaic to pure carbonate platform settings as a result of warm climate and tectonics.This Middle Permian warming is confirmed by sea-level rise and the presence of a temperature-sensitive fusulinid fauna in association with photozoan-based ooids.Deposition of the Amb Fm.and establishment of a carbonate platform are envisaged to be associated with major rifting of northern Gondwana,which subsequently resulted in the development of a rift basin at the passive margin of the NW Indian Plate then in northern Pakistan.

Factors controlling tight oil and gas reservoir development in the Jurassic siliciclastic-carbonate rocks in Sichuan Basin, China

The prediction of“sweet spot”of multi-lithology composite tight oil and gas reservoirs within mixed siliciclastic-carbonate sequences is a hot topic in oil and gas exploration.There are mixed lacustrine carbonate-siliciclastic rocks in the Da'anzhai Member of Ziliujing Formation in the Eastern Slope of western Sichuan Depression.The reservoir lithology is complex,and the main factors controlling the development of high-quality reservoirs are yet to be known.Based on a large number of drilling,core and thin section observation,well log and seismic data,this paper systematically studies the characteristics and factors controlling the development of the mixed siliciclastic-carbonate reservoir.The results show that the reservoir is composed primarily of coquina,sandstone,breccia and shale in lithology,and its development is mainly controlled by sedimentary microfacies,diagenesis,tectonism(fracturing)and paleogeomorphology during the sedimentary period.The effective fractures in reservoirs of the low-energy shell shoal facies are well developed with relatively good physical properties.With the change of sedimentary microfacies from low-energy shoal to high-energy shoal to arenaceous shoal,the hy-drocarbon production capacity worsens step by step.Diagenesis,such as dissolution and fracturing,has a certain effect on reservoir physical properties.The palaeogeomorphic highs and slopes had well-developed fractures during the sedimentary period which are conducive to constructive dissolution,and thus they are favorable zones for reservoir development.The development of structural fractures further amplifies the influence of dissolution;thus the fracture zones are also favorable for the devel-opment of high-quality reservoirs.The favorable sedimentary facies zone and fracture development degree serve as the core factors for the formation of high-quality mixed reservoirs.The muddy limestone with certain dissolved pores and structural fractures deposited under the low-energy shell shoal setting is of relatively high-quality reservoir in the Da'anzhai Member.

Mixed Siliciclastic-Carbonate Sediments in China: Recent Advances and Prospects

Until 1980s,mixed siliciclastic-carbonate sediments(MSCSs)had been thought as odd exception and not important.However,MSCSs are quite common in the modern and the ancient times and can be important in

Oil-source rock correlation and quantitative assessment of Ordovician mixed oils in the Tazhong Uplift, Tarim Basin

The origin of the marine oils in the Tarim Basin has long been a disputed topic. A total of 58 DST （drill stem test） crude oil and 8 rock samples were investigated using a comprehensive geochemical method to characterize and identify the origin of the Ordovician oils in the Tazhong Uplift, Tarim Basin, northwest China. Detailed oil–oil and oil–source rock correlations show that the majority of the oils have typical biomarker characteristics of the Middle-Upper Ordovician （O2＋3） source rock and the related crude oil. These characteristics include a distinct ＂V-shaped＂ relative abundance of C27, C28 and C29 regular steranes, low abundance of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. Only a few oils display typical biomarker characteristics indicating the Cambrian–Lower Ordovician （∈-O1） genetic affinity, such as linear or anti ＂L＂ shape distribution of C27, C28 and C29 regular sterane, with relatively high concentrations of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. It appears that most of the Ordovician oils in the Tazhong Uplift were derived from the O2＋3 intervals, as suggested by previous studies. However, the compound specific n-alkane stable carbon isotope data indicate that the Ordovician oils are mixtures from both the ∈-O1 and O2＋3 source rocks rather than from the O2＋3 strata alone. It was calculated that the proportion of the∈-O1 genetic affinity oils mixed is about 10.8%-74.1%, with an increasing trend with increasing burial depth. This new oil-mixing model is critical for understanding hydrocarbon generation and accumulation mechanisms in the region, and may have important implications for further hydrocarbon exploration in the Tarim Basin.

EXPERIMENTAL AND THEORETICAL STUDY OF STATIC-DYNAMIC MIXED MODE BRITTLE FRACTURE OF ROCK

A new criterion of static dynamic state mixed mode brittle fracture initiation in rock is suggested, i.e. the distortion strain energy criterion.When t →∞, the static state distortion strain energy criteria and the formula for determiming static state fracture angle are obtained. The new static state criterion, suggested by authors, is in good agreement with the author′s experimental results. In addition, the relative accuracy of three current fracture theories and the new criterion in predicting static state mixed mode initiation fracture loading and fracture angle in rock have been evaluated experimentally.

Growth Characteristics of Mixed Bacteria and Its Solubilizing Effect on Low-grade Phosphate Rock

In this paper, the growth characteristics of Acidithiobacillus ferrooxidans （At.f） and Acidithiobacillus thiooxidans （At. f） in mixed culture has been studied, explored mixed bacteria phosphate solubilization effect, from a kind of low-grade phosphate rock. The results show that mixed bacteria has strong ability to produce acid, and have stronger oxidation activity to energy source -Fe^2＋. Mixed bacteria can significantly increase the rate of phosphate solubilization from phosphate rock in low concentration pulp. It goes against mixed bacteria reproduction when pulp concentration increased, makes phosphate solubilization rate decreased.

DYNAMIC MIXED MODE FRACTURE INITIATION IN ROCK^+

In this paper, a distortion dynamic strain energy density factor criterion for dynamic mixed-mode fracture initiation in rock is suggested.The results of the investigation on 14 three-point bending (TPB) and four-point bending(FPB) rock specimens tested u

Paleogeomorphology of Mixed Rock Deposition in KL16 Oilfield

KL16 (Kenli 16) oilfield is located in Bohai Sea, close to Laizhou Bay depression, with favorable reservoir forming conditions. The lower member of Shahejie Formation (lower sub member of the third member of Shahejie formation) has shallow burial, complex structural sedimentary evolution, diverse reservoir lithology types, and unclear reservoir distribution laws, which restrict the exploration and development process. Comprehensive use of core, seismic, logging and analytical laboratory data, through the combination of structural recovery and stratigraphic recovery, the micro paleogeomorphology of the lower member of Shahejie Formation in the sedimentary period is finely restored, and the sedimentary system and sedimentary model in the study area are defined. The study shows that during the sedimentary period of the lower member of Shahejie formation, four geomorphic units were developed in the study area: uplift, slope, platform and depression;Under the control of paleogeomorphology, three different sedimentary environments are developed: Braided River Delta is developed in the west, shore shallow lake mixed beach bar is developed in the middle, and fan delta is developed in the south. Based on the analysis of regional geology and sedimentary characteristics, the principal component coupling technology based on the constraint of sedimentary facies belt is optimized for reservoir distribution prediction, and the application effect is good.

Groundwater monitoring of an open-pit limestone quarry:Water-rock interaction and mixing estimation within the rock layers by geochemical and statistical analyses

Water-rock interaction and groundwater mixing are important phenomena in understanding hydrogeological systems and the stability of rock slopes especially those consisting largely of moderately watersoluble minerals like calcite. In this study, the hydrogeological and geochemical evolutions of groundwater in a limestone quarry composed of three strata: limestone layer(covering), interbedded layer under the covering layer, and slaty greenstone layer(basement) were investigated. Water-rock interaction in the open-pit limestone quarry was evaluated using PHREEQC, while hierarchical cluster analysis(HCA)and principal component analysis(PCA) were used to classify and identify water sources responsible for possible groundwater mixing within rock layers. In addition, Geochemist's Workbench was applied to estimate the mixing fractions to clarify sensitive zones that may affect rock slope stability. The results showed that the changes in Ca2+and HCO3àconcentrations of several groundwater samples along the interbedded layer could be attributed to mixing groundwater from the limestone layer and that from slaty greenstone layer. Based on the HCA and PCA results, groundwaters were classified into several types depending on their origin:(1) groundwater from the limestone layer(LO),(2) mixed groundwater flowing along the interbedded layer(e.g., groundwater samples L-7, L-11, S-3 and S-4), and(3) groundwater originating from the slaty greenstone layer(SO). The mixing fractions of 41% LO: 59% SO, 64% LO: 36% SO, 43%LO: 57% SOand 25% LO: 75% SOon the normal days corresponded to groundwaters L-7, L-11, S-3 and S-4,respectively, while the mixing fractions of groundwaters L-7 and L-11(61% LO: 39% SOand 93% LO: 7% SO,respectively) on rainy days became the majority of groundwater originating from the limestone layer.These indicate that groundwater along the interbedded layer significantly affected the stability of rock slopes by enlarging multi-breaking zones in the layer through calcite dissolution and inducing high water pressure, tension cracks and potential sliding plane along this layer particularly during intense rainfall episodes.

Modelling and mechanical characteristics of PDC cutter-rock interaction by combining mixed fragmentation modes with dynamic rock strength

Polycrystalline diamond compact(PDC)bit is one of the most widely used drill bits for improving the rate of penetration in deep oil and gas well and geothermal well.However,the dynamic rock fragmentation mechanics characteristics of PDC bits are still unclearly.A coupled fragmentation mechanics model of PDC cutter-rock interaction is established by combining the mixed fragmentation modes with dynamic strength.The coupling influence laws of cutter angle,cutting depth,dynamic strength ratio,breaking modes on the horizontal force coefficient(HFC),vertical force coefficient(VFC)and specific energy are analyzed.The model of this paper can optimize cutter inclination angle,cutting depth and minimum specific energy.With the increase of the cutter inclination angle,the dynamic VFC changes into two modes.The definition of the dynamic modes depends on the dynamic strength ratio.As the cutting angle increases,the cutting force increases.The cutting force increases nonlinearly with increasing cutting depth.The specific energy of rock fragmentation increases nonlinearly with increasing cutting depth.With the increase of dynamic strength,the specific energy of rock fragmentation increases nonlinearly.When the input-energy increases,the rate of penetration response is divided into three stages.The results have important guiding significance for the PDC bit design and drilling parameters optimization to increase the rate of penetration and the efficiency of exploration and development.

New method to identify optimal discontinuity set number of rock tunnel excavation face orientation based on Fisher mixed evaluation

Discontinuity is critical for strength,deformability,and permeability of rock mass.Set information is one of the essential discontinuity characteristics and is usually accessed by orientation grouping.Traditional methods of identifying optimal discontinuity set numbers are usually achieved by clustering validity indexes,which mainly relies on the aggregation and dispersion of clusters and leads to the inaccuracy and instability of evaluation.This paper proposes a new method of Fisher mixed evaluation(FME)to identify optimal group numbers of rock mass discontinuity orientation.In FME,orientation distribution is regarded as the superposition of Fisher mixed distributions.Optimal grouping results are identified by considering the fitting accuracy of Fisher mixed distributions,the probability monopoly and central location significance of independent Fisher centers.A Halley-Expectation-Maximization(EM)algorithm is derived to achieve an automatic fitting of Fisher mixed distribution.Three real rock discontinuity models combined with three orientation clustering algorithms are adopted for discontinuity grouping.Four clustering validity indexes are used to automatically identify optimal group numbers for comparison.The results show that FME is more accurate and robust than the other clustering validity indexes in optimal discontinuity group number identification for different rock models and orientation clustering algorithms.

Tunnelling through weak and fragile rocks of Himalayas

A considerable amount of tunnelling has been going on in India for various projects such as hydroelectric power, irrigation, roads and railways. Most of these projects are located in Himalayas, far away from the urban areas. Tunnelling through weak and jointed rock masses such as the one in the Himalayas is a challenging task for the planners, designers, engineers and geologists because of high overburden, thickly vegetated surface, weak, poor and fragile rocks and highly varying geology with the presence of numerous small and big shear zones, faults, etc. Due to these reasons, various tunnelling problems have been faced in the past and are still being encountered. Failures and the problems may be regarded as challenges and opportunities for generating new knowledge base and thereby increasing self-reliance in tunnelling. The experiences of Himalayan tunnelling through weak and fragile rocks covering varying and mixed geology, understanding on tunnelling in squeezing ground conditions and applicability of TBM in Himalayas are presented. It has also been highlighted that the probe holes planning, drilling and monitoring shall be followed seriously to reduce the geological surprises.

温度影响下罗布泊盐岩路基填料变形特性研究

为探明温度影响下盐岩路基填料变形特性,保障盐岩路基稳定性,促进盐岩在路基工程中资源化应用,全面分析了卤水及盐岩相变特征,基于正交试验方法探究了单次降温多因素交互作用下盐岩填料的变形规律,系统研究了多次冻融循环后盐岩填料盐胀累积规律,并基于试验段现场监测综合评价了盐湖区盐岩路基变形特征。结果表明:不同浓度卤水降温曲线均未出现明显过冷阶段,其降温曲线平衡及波动维持时间极为短暂,同时卤水相变温度随浓度增加而升高。盐岩填料的降温曲线存在显著的过冷及温度跳跃阶段,其相变温度随拌和卤水浓度增加而下降。单次降温作用下盐岩填料变形量介于-0.09~0.18 mm,各因素对盐岩填料变形的影响顺序为:上覆荷载>含卤水率>最大粒径>压实度。冻融循环作用下拌合卤水浓度越低,盐岩填料盐胀量越大;上覆荷载对盐岩填料盐胀抑制作用较强。实体工程现场监测表明随着监测时间增长盐岩路基变形呈现正弦波式周期性变化,且变形沿深度方向呈减小趋势,同时盐岩路基变形与温度具有较强的线性相关性。

CO_(2)快速吞吐提高页岩油采收率现场试验

页岩油注CO_(2)吞吐提高采收率技术处于探索阶段,目前面临着CO_(2)与页岩储层及流体相互作用机制不明确、数值模拟技术不成熟、缺乏规模注采及低成本回收工艺等技术难题。为探索页岩油注CO_(2)提高采收率主控机理,以苏北盆地溱潼凹陷古近系阜宁组二段页岩油为对象开展了超临界CO_(2)水岩反应实验,分析了高温高压条件下页岩矿物溶蚀作用及其对孔隙度和渗透率的影响,并通过注CO_(2)恒质膨胀实验、最小混相压力测试评价了地层超压条件下注CO_(2)后原油高压物性变化特征,并在此基础上开展考虑多因素数值模拟研究优化了设计注入参数,最终通过矿场试验验证了技术可行性。研究结果表明:(1) CO_(2)水岩反应以碳酸质矿物溶蚀占主导,长英质矿物部分溶解,生成中大孔隙;(2)在地层原油中注入适量的CO_(2),显著萃取了原油中间烃组分,原油黏度从5.151 mPa·s下降到1.250 mPa·s,且CO_(2)首先萃取轻烃组分,随生产时间增加萃取组分逐渐变为重烃;(3)基于人工压裂与天然缝网混合介质组分数模模型,优化设计单井吞吐注气量1.7×10~4 t,注气速度500~600 t/d,焖井时间50 d;(4)低压侧加热的页岩油CO_(2)吞吐地面工艺,可依据CO_(2)注入地面工艺多参数数据模型,实现精准控温,避免注入管线冻堵及井下油管和套管材料低温脆断问题;(5)产出气CO_(2)浓度高于80%时,采用气相回收直注工艺,实现产出气回收成本降至104元/t。结论认为,CO_(2)快速吞吐有效提高了页岩油采收率,形成的机理认识和技术系列可为页岩油注CO_(2)吞吐开发提供参考和借鉴。

智能放煤理论与技术研究进展

综放开采技术是厚及特厚煤层开采的有效方法,已成为我国在世界煤炭开采行业的标志性技术。综述了“四要素”放煤理论、顶煤采出率与含矸率关系、基于块度分布的采出率预测模型、煤流瞬时含矸率-累计含矸率关系等智能放煤理论研究进展。分析了智能放煤技术难点,指出含矸率是影响顶煤采出率和煤质的关键因素,放煤过程中含矸率的快速、准确计算是智能放煤技术突破的重点和关键。将智能放煤技术分为非图像识别智能放煤技术和图像识别智能放煤技术2类,对不同技术的研究进展、优缺点及使用条件进行了详细分析。非图像识别智能放煤技术包括记忆放煤技术、声音振动信号识别技术、γ射线探测技术、探地雷达技术、微波照射+红外探测技术、激光扫描放煤量监测技术等,图像识别智能放煤技术包括井下照度环境精准控制、放煤图像去尘算法、含矸率计算精度保障策略、煤岩红外图像识别等。

不同降雨类型下混合花岗岩路堑边坡稳定性分析

降雨是影响边坡稳定性的重要因素之一,降雨入渗导致边坡的孔隙水压力增大,基质吸力减小,地下水水位抬升以及岩土体抗剪强度降低,皆对边坡稳定性产生不利影响。为研究不同降雨类型(均匀型、间歇型)和不同岩土体渗透系数条件下混合花岗岩路堑边坡渗流特性以及稳定性的变化规律,基于饱和-非饱和理论和强度折减有限元理论,运用Plaxis2D数值模拟软件,分析了10d内不同降雨类型和不同岩土体渗透系数组合条件下标准混合花岗岩路堑边坡的渗流特性以及稳定性的变化特征,并结合云南某混合花岗岩路堑边坡工程实例分析其降雨历时30d的边坡稳定性。结果表明:对于渗透系数较小的岩土体,降雨对边坡稳定性的影响有限;对于渗透系数较大的岩土体,降雨强度越大,边坡稳定性系数越低,且在均匀型降雨工况下边坡稳定性最低;岩土体渗透系数越大,且降雨强度越大,边坡受降雨影响的滞后性表现越不明显;降雨类型对边坡滑移面深度有一定的影响,均匀型强降雨对浅层土体强度的影响较大,易引起浅层滑坡。该研究成果可以为同类混合花岗岩路堑边坡稳定性规律的研究提供参考。

东昆仑西段岩碧山构造混杂带构造变形特征及就位机制研究

岩碧山构造混杂岩带,位于南昆仑地块北侧,东与畅流沟—向阳泉蛇绿混杂岩相连,东南汇入木孜塔格—布青山蛇绿构造混杂岩带,近北西西向发育以逆冲及走滑性质构造系为主体,叠加了晚期逆冲推覆构造的混杂岩带(邵东等,2017)(图1)。根据岩碧山构造混杂岩带的物质特征,将其划分为早古生代岛弧型、变质基底、洋壳杂岩3类岩块,长英质糜棱岩、构造碎裂岩2类基质和晚古生代洋盆演化相关的洋壳杂岩组成。

寒武系第二统浅水混合沉积发育特征及影响因素——以陕南朱家坝剖面仙女洞组为例

【目的】混积岩同时具有指示水体化学条件和生物活动的碳酸盐组分以及指示物源区性质和风化过程的碎屑组分,因而在古环境和古气候研究方面具有独特价值。【方法】寒武纪早期上扬子克拉通北部汉南—米仓山古陆周缘混合沉积非常发育,以陕西南郑朱家坝剖面仙女洞组为例,对研究区混积岩特征开展了系统的岩相学和沉积学研究。【结果与结论】混合沉积形成于海退背景下由中缓坡向内缓坡转变的过渡环境,且混积程度具有规律性,即在多个向上变浅序列的中部最为发育,在每个序列底部和顶部分别为碎屑组分主导和碳酸盐组分主导(或清水碳酸盐沉积)。中缓坡环境下以碎屑组分沉积为主,碳酸盐组分除小型原地生物礁外,主要来自浅水环境搬运的细粒沉积物;内缓坡潮下带相对低能环境仍以碎屑组分沉积为主,但原地生物礁以及礁角砾和内碎屑搬运沉积常见;内缓坡潮下高能带以鲕粒滩和生物礁等原地碳酸盐沉积为主,混入的陆源组分主要为砂级石英和岩屑颗粒;潟湖环境以白云石化颗粒和陆源细粒物质的混合为特征。研究区寒武纪早期混积体系的发育与当时浅水环境较高的碳酸盐产率以及沿岸流、波浪、风暴等搬运作用有关。本实例可为了解深时混合沉积成因提供一个思路,也可为上扬子地区寒武系混积岩油气勘探提供参考。

陆相断陷咸化湖盆细粒沉积岩特征及沉积环境——以泌阳凹陷核桃园组H3Ⅲ亚段为例

泌阳凹陷作为国内典型的陆相断陷咸化湖盆,在古近系核桃园组三段广泛发育细粒沉积岩。文中利用长井段连续取心资料以及薄片观察、二维XRF扫描、XRD分析、扫描电镜以及地球化学测试等手段,以矿物组分、沉积构造和粒度作为主要依据,把泌阳凹陷H3Ⅲ亚段细粒沉积岩划分为9种岩相类型,其中纹层状混合质页岩、纹层状长英质页岩是发育类型最多的细粒沉积岩;通过Mg/Ca、Al含量、Ti含量、(Fe+Al)/(Ca+Mg)、P/Ti、Sr/Ba和V/(V+Ni)等地球化学指标的垂向变化及岩相组合来分析沉积环境的演化特征。泌阳凹陷H3Ⅲ亚段沉积环境是半深湖—深湖环境,水体盐度为半咸水—咸水,陆源输入总体较强,气候变化相对较大,从下到上经历了干旱、干湿交替、湿润以及干旱的气候变化。岩相的垂向变化受气候、陆源输入、水深、水体盐度的影响,气候、陆源输入、水深决定了长英质矿物和黏土矿物的含量,而碳酸盐矿物的含量主要受到水体盐度和气候的影响。

喀斯特区土石工程堆积体坡面植被恢复评价

[目的]对喀斯特区土石工程堆积体坡面植被恢复进行评价,以期为喀斯特区工程堆积体生态修复提供基础理论支撑,并为生态文明建设提供参考依据。[方法]选取喀斯特区不同恢复年限(3,5,7 a)及不同植被类型(草地及草灌混交)的公路线性土石工程堆积体为研究对象,运用主成分分析法,选取石砾含量、土壤物理参数、土壤化学指标、水力学参数及植物群落指标构建评价指标体系,分析了土石工程堆积体坡面植被恢复特征与各生态影响因子之间的互作关系。[结果](1)喀斯特区土石工程堆积体坡面植被恢复过程是一个不断对资源和空间重新分配的过程,随着恢复时间的增加,坡面植被物种丰富度逐渐降低,群落的优势种越来越明显。(2)土壤有机质、自然含水率和饱和导水率是影响土石工程堆积坡面植被恢复初期的主要因子,而植被恢复又有助于改善其坡面土壤结构状况及养分含量,其坡面植被恢复的前期重点是如何改善坡面土壤水力学特性。(3)喀斯特区土石工程堆积体坡面先锋植被群落构建阶段的植被恢复模式可采取草灌混交,后逐步考虑增加乔木,同时适当搭配一定的深根植物。[结论]改善坡面土壤水力学特性有助于喀斯特区土石工程堆积体坡面初期植被恢复,可采取先草灌混交、后逐步搭配深根乔木的植被恢复模式。