盐胶结层的特性研究

近几年在兰新铁路的第二双线、库格线、哈罗线等新疆多条铁路线路的勘察中,发现在第四系土层中存在一种特殊的胶结类型——盐胶结。通过盐胶结类型的成因、力学特性和机理的分析研究,结果表明盐胶结的成因与盐渍土不同,其强度受含水量的影响较大,由于盐胶结层的存在,导致了岩土施工工程分级由Ⅲ级硬土提高为Ⅳ级软石,施工措施应相应变化。

南加蓬次盆L气田盐胶结储层特征分析与识别

西非深水盐下储层是近年来油气勘探的热点,L气田位于南加蓬次盆深水区,储层呈低渗特征,盐胶结作用是储层物性变差的主要原因。由于盐岩密度较低(2.1 g/cm^(3)),存在盐胶结现象,可造成密度曲线值降低,给孔隙度计算带来偏差。识别储层是否存在盐胶结是该类储层评价的关键,分析发现元素俘获测井可以有效指示盐胶结的存在;在无元素俘获测井时,利用常规测井与核磁测井建立盐胶结识别因子曲线也能定性识别盐胶结的存在。在盐胶结层段声波测井可较准确地计算孔隙度,为下一步测井解释评价奠定了基础。

西非加蓬盆地深水盐下局部盐胶结储层精细预测技术

西非加蓬盆地是一个典型的大西洋被动大陆边缘盆地,其深水盐下为一个高风险与高潜力并存的勘探新领域。近年来,在加蓬深水区M气田的勘探中,遇到了盐胶结型储层预测的新难题。在钻井数量少、地震资料品质有限以及缺乏成熟技术体系参考的条件下,通过对盐胶结成因机制进行深入研究,结合岩石物理分析、地震属性分析、盐胶结型砂岩储层岩石物理模型以及正、反演等关键地球物理技术手段,对盐胶结储层进行精细综合预测,探索形成了"基于地质成因机制指导下的盐胶结储层精细预测技术组合"。运用该技术有效预测了M气田的有利储层分布区,指导了M气田的勘探及评价。

粗颗粒盐渍土力学参数的现场直剪试验研究

通过对典型粗颗粒盐渍土场地角砾土进行现场直接剪切试验,研究了粗颗粒盐渍土的强度特性及参数取值。试验结果表明:粗颗粒盐渍土强度参数由黏聚力和内摩擦角组成,盐分的胶结对黏聚力的影响比较明显,颗粒的组成则对内摩擦角影响较大。同时,对于角砾类粗颗粒盐渍土,当存在盐胶结作用时,建议黏聚力值在45~80k Pa、内摩擦角在34~38°之间选取;当角砾类盐渍土结构松散时,建议黏聚力值在9~15k Pa、内摩擦角可在33~38°之间取值。该研究成果可直接为粗颗粒盐渍土地区的工程设计提供借鉴。

西非加蓬盆地深水盐下油气勘探技术创新与实践

西非加蓬盆地深水盐下是一个高风险与高潜力并存的勘探领域,油气勘探面临复杂盐下构造解释与圈闭落实、盐下湖相烃源岩预测以及盐胶结型储层预测等重大地质难题和技术挑战。在充分类比优选及组合应用地震资料的基础上,以基于盐变形机制的盐下构造解释模型为指导,形成了以盐下层位解释、多尺度盐下断裂解释技术和构造假象识别技术为核心的复杂盐下构造分析技术体系;从国内及海外资料相对丰富的成熟探区研究出发,探索并形成了地化相、有机相、沉积相与地震相"四相结合"的湖相烃源岩早期预测技术;提出了砂岩与盐岩通过断面对接导致卤水进入是盐下砂岩储层发育盐胶结作用的成因机理,并结合地球物理分析形成了盐胶结型储层综合预测技术。综合运用以上技术指导油气勘探,在加蓬深水盐下发现了L大型气田。

Distribution and genesis of secondary pores in Paleogene clastic reservoirs of Beidagang structural belt in the Huanghua depression

The distribution and genesis of secondary pores in Paleogene clastic reservoirs of Beidagang structural belt in the Huanghua depression have been systematically studied. We investigated sedimentary facies and carried out a comprehensive analy-sis of the vast amount of data from casting thin sections, scanning electron microscope and physical data. Then we analyzed the pore types, pore evolution, distribution and genesis of secondary pores in our study area and discussed the factors controlling the distribution of secondary pores. The results show that pores in the study area are largely composed of intergranular dissolution pores and constituent dissolved pores. Three secondary pore zones were developed in the study area at depths of 2800~3400 m, 3600~4200 m and 4500~4800 m. Secondary pores have been formed mainly because carbonate cement, feldspar, clastic debris and other plastic substances were dissolved by organic acid, released during the evolution of organic matter and acid water formed by CO2. The development and distribution of secondary pores are vertically controlled by the maturity time of source rocks and hori-zontally by the distribution of acid water. As well, this distribution was affected by the sedimentary facies belt and the development of fault zones.

Effect of the Alumosilicate Gels pH on Zeolite Phase Composition for the Co-crystallization of BEA/MOR Zeolites in Na2O-TEABr-Al2O3-SiO2-H2O System

This paper deals with the method of zeolites BEA （beta） and MOR （mordenite） synthesis and the co-crystallization method of zeolites BEA/MOR. Synthesized zeolites were studied based on the SEM （scanning electron microscopy）, XRD （x-ray diffraction） and chemical analysis. The porous structure of these zeolites was investigated by nitrogen low-temperature adsorption. It has been illustrated that regulation of the BEA/MOR co-crystalline zeolites phase composition is possible due to variations of the initial alumosilicate gels composition and hydrogen ions concentration. Zeolites containing the co-crystalline phases of BEA/MOR could to be attractive in the processes using the catalysts, which based on the pure phases BEA or MOR zeolites.

Pilot study on binding of bovine salivary proteins to grit silicates and plant phytoliths

Mostly fed with grass in fresh or conserved form, cattle and other livestock have to cope with silicate defence bodies from plants （phytoliths） and environmental silicates （grit）, which abrade tooth enamel and could additionally interact with various salivary proteins. To detect potential candidates for silicate-binding proteins, bovine whole saliva was incubated with grass-derived phytoliths and silicates. Interactions of salivary proteins with pulverized bovine dental enamel and dentine were additionally analysed. After intense washing, the powder fractions were loaded onto 1D-polyacrylamide gels, most prominent adhesive protein bands were cut out and proteins were identified by mass spectrometry within three independent replicates. All materials were mainly botmd by bovine odorant-binding protein, bovine salivary protein 30× 10^3 and carbonic anhydrase VI. The phytolith/silicate fraction showed additional stronger interaction with haemoglobin β and lactoperoxidase. Conceivably, the binding of these proteins to the surfaces may contribute to biological processes occurring on them.

中国戈壁地区地质勘察的几点体会

戈壁滩是中国西部地区特有的一种地貌形式，一般误以为地质问题简单．近年来随着西部大开发的实施，西部戈壁地区完成了大量的工程项目，暴露出不少地质问题．文章在宏观分析中国戈壁特征的基础上，根据多年来戈壁地区勘察及施工经验，提出了戈壁地区独特的地层结构问题，盐胶结土层的工程等级问题和盐渍土定性问题．最后针对发现的问题提出了在勘察及施工中的解决措施和建议，可为今后在同类地区进行工程项目提供指导．

Diagenetic fluid evolution and water-rock interaction model of carbonate cements in sandstone: An example from the reservoir sandstone of the Fourth Member of the Xujiahe Formation of the Xiaoquan-Fenggu area, Sichuan Province, China

Carbonate cement is the most abundant cement type in the Fourth Member of the Xujiahe Formation in the Xiaoquan-Fenggu area of the West Sichuan Depression. Here we use a systematic analysis of carbonate cement petrology, mineralogy, carbon and oxygen isotope ratios and enclosure homogenization temperatures to study the precipitation mechanism, pore fluid evolu- tion, and distribution of different types of carbonate cement in reservoir sand in the study area. Crystalline calcite has relatively heavy carbon and oxygen isotope ratios （δ13C = 2.14%o, 8180 = -5.77‰）, and was precipitated early. It was precipitated di- rectly from supersaturated alkaline fluid under normal temperature and pressure conditions. At the time of precipitation, the fluid oxygen isotope ratio was very light, mainly showing the characteristics of a mixed meteoric water-seawater fluid（ δ180 = -3‰）, which shows that the fluid during precipitation was influenced by both meteoric water and seawater. The calcite cement that fills in the secondary pores has relatively lighter carbon and oxygen isotope ratios （δ13C = -2.36%0, 8180 = -15.68‰）. This cement was precipitated late, mainly during the Middle and Late Jurassic. An important material source for this carbonate cement was the feldspar corrosion process that involved organic matter. The Ca2＋, Fe3＋ and Mg2＋ ions released by the clay mineral transformation process were also important source materials. Because of water-rock interactions during the buri- al process, the oxygen isotope ratio of the fluid significantly increased during precipitation, by about 3‰. The dolomite ce- ments in calcarenaceous sandstone that was precipitated during the Middle Jurassic have heavier carbon and oxygen isotope ratios, which are similar to those of carbonate debris in the sandstone （δ13C = 1.93%o, δ180 = -6.11‰）, demonstrating that the two are from the same source that had a heavier oxygen isotope ratio （δ180 of about 2.2‰）. The differences in fluid oxygen isotope ratios during cement precipitation reflect the influences of different water-rock interaction systems or different wa- ter-rock interaction strengths. This is the main reason why the sandstone containing many rigid particles （lithic quartz sand- stone） has a relatively negative carbon isotope ratio and why the precipitation fluid in calcarenaceous sandstone has a relatively heavier oxygen isotope ratio.

Characteristics of carbonate cementation in clastic rocks from the Chang 6 sandbody of Yanchang Formation, southern Ordos Basin

Densification of reservoir is an important factor that restricts oil and gas exploration from low porosity and extra-low permeability reservoirs. Carbonate cementation was heavily developed in Chang 6 sandbody, a facies of underwater distributary channel in delta front, of Upper Triassic Yanchang Formation in Fuxian area, southern Ordos Basin, and the cementation is one of the major factors that affect quality of reservoir. Based on the macro-microcosmic petrology and geochemistry features, the genesis of densification of carbonate-cemented reservoir was systematically discussed. The carbonate cementation can be classified into endogenous and exogenous, and the essential differences between them are that they were formed in different fluids and in different diagenesis periods. With the aid of identification of thin sections, analyses on electron probe, trace and rare-earth elements, carbon and oxygen isotope, we propose that the endogenous fluid for cementation came from the rock itself during early diagenetic stage. The minerals related to endogenous fluid had good shapes. The reservoir property was enhanced with porosity increasing by 3%-8% because of later dissolution by endogenous fluid. The exogenous fluid might be water combining with CO 2 , likely released from organic matter-rich mudstone. Calcite cement, in form of substrate cementation, was precipitated from the fluid and filled in the remaining pores of sandstones in late diagenetic stage as variations of physical and chemical conditions. The exogenous cement reduced rock porosity, damaged reservoir property, affected some oil enrichment, and seriously caused Chang 6 reservoir densification. Some of the dense layers that formed on top of sandbody could have served as diagenetic traps, and thus the exogenous cementation area could be favorable for oil exploration.

Effect and quantitative evaluation of CO_2 derived from organic matter in coal on the formation of tight sandstone reservoirs

Tight reservoirs are widely distributed, especially in coal measure strata. Identification of the densification mechanism of the tight sandstone reservoirs is critical in effectively exploring and exploiting tight gasoil resources. In this study, the gas for mation from type III organic matter in coal was kinetically modeled for the whole diagenetic stage, from the shallow buried biogas generation stage to the deep buried thermal gas generation stage. The results demonstrated that during hydrocarbon formation, quantities of nonhydrocarbon gases, such as CO2, were generated. The proportion of CO2 is about 50%70% of that of the C15, which far exceeds the CO2 content （05%） in the natural gas in the sedimentary basins. Geological case study analysis showed that a considerable part of the ＂lost＂ gaseous CO2 was converted into carbonate cement under favorable envi ronments. Under the ideal conditions, the volume of the carbonate cement transformed from total CO2 generated by 1 m3 coal （Junggar Basin Jurassic, TOC 67%） can amount to 0.32 m3. Obviously, this process plays a very important role in the for mation of tight sandstone reservoirs in the coal measures. Our results also show that the kinetic generation processes of Ci5 and CO2 are asynchronous. There are two main stages of CO2 generation, one at the weak diagenetic stage and the other at the overmature stage, which are different from largescale multistage hydrocarbon gas generation. Therefore, we can understand the mechanism of tight gas charging by determining the filling time for a tight gas reservoir and the key period of CO2 genera tion. Further analysis and correlation studies of a specific region are of great significance for determining the mechanism and modeling gas charging in tight reservoirs. It should be noted that the formation of tight sandstone reservoirs is the combined result of complex organicinorganic and waterrockhydrocarbon interactions. The details of spatial and temporal distributions of the carbonate cement derived from the organic C02, which combines with metal ions （Ca/Mg/Fe） in the formation water, should be further investigated.

Effects of temperature and sodium carboxylate additives on mineralization of calcium oxalate in silica gel systems

The effects of temperature and multifunctional sodium carboxylate additives on the phase composition and morphology of calcium oxalate (CaOxa) crystals grown in silica gel system were systematically investigated using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and Fourier-transform infrared spectra (FT-IR). The sodium carboxylates investigated include: monocarboxylate sodium acetate (NaAc), disodium tartrate (Na2tart), trisodium citrate (Na3cit), and the disodium salt of ethylenediaminetetraacetic acid (Na2edta). The temperature range was from 7°C to 67°C. The crystallization temperature affects the phase compositions, the growth rate, and the morphology of CaOxa. First, the logarithm of the percentage of calcium oxalate dihydrate (COD) formed at a certain temperature (T) is proportional to the reciprocal of temperature (1/T). Second, the weight of CaOxa crystals decreases as decreasing the temperature. At a given temperature, the ability of the sodium carboxylates to induce COD follows the order: Na2edta Na3cit Na2tart NaAc. Third, the multicarboxylates can decrease the surface area of calcium oxalate monohydrate (COM). It makes the edges and tips of COM crystals blunt and oval. All the three changes, an increase of the content of COD, a decrease of the weight of CaOxa crystals, and a decrease of the surface area of COM crystals, can inhibit the formation of CaOxa stones. These results support the clinical use of citrates and may be helpful in elucidating the mechanisms of the formation of CaOxa calculus. Keywords calcium oxalate - sodium carboxylate - gel - urinary calculi - crystallization - biomineralization