Control Factors of Solutional Voids in Feldspars and Favorable Zone Forecast of Chang 2 Oil Reservoir Group in the Midwest Ordos Basin

The development of pores in a clastic reservoir is one of the most important research subjects in oil-gas exploration and development, whereas the many reasons for the formation of secondary porosity have increased the degree of difficulty in such research. Thus the research aims are to discover the controlling factors of solutional voids in feldspars and to predict favorable regions for these voids. Macroscopic and systematic researches into the relationship between the kaolinite content in the feldspar solutional void developed area of the Chang 2 reservoir group of the Triassic Yanchang Formation in the Midwest Ordos Basin and the solutional void in feldspar have been made, and from this it can be determined that the kaolinite content has an indicative function to the distribution of the solutional void in feldspar. Solutional void in feldspar is relatively well developed at the area where kaolinite content is high. Although the factors affecting kaolinite content are complicated, yet that of the research area is mainly affected by the impact of the leaching atmospheric water acting on the palaeogeomorphology. Three favorable zone belts for the development of solutional voids in feldspars are forecasted on the basis of restoration of palaeogeomorphology.

Experimental study on thermal and mechanical properties of tailings-based cemented paste backfill with CaCl_(2)·6H_(2)O/expanded vermiculite shape stabilized phase change materials

CaCl_(2)·6H_(2)O/expanded vermiculite shape stabilized phase change materials(CEV)was prepared by atmospheric impregnation method.Using gold mine tailings as aggregate of cemented paste backfill(CPB)material,the CPB with CEV added was prepared,and the specific heat capacity,thermal conductivity,and uniaxial compressive strength(UCS)of CPB with different cement-tailing ratios and CEV addition ratios were tested,the influence of the above variables on the thermal and mechanical properties of CPB was analyzed.The results show that the maximum encapsulation capacity of expanded vermiculite for CaCl_(2)·6H_(2)O is about 60%,and the melting and solidification enthalpies of CEV can reach 98.87 J/g and 97.56 J/g,respectively.For the CPB without CEV,the specific heat capacity,thermal conductivity,and UCS decrease with the decrease of cement-tailing ratio.For the CPB with CEV added,with the increase of CEV addition ratio,the specific heat capacity increases significantly,and the sensible heat storage capacity and latent heat storage capacity can be increased by at least 10.74%and 218.97%respectively after adding 12%CEV.However,the addition of CEV leads to the increase of pores,and the thermal conductivity and UCS both decrease with the increase of CEV addition.When cement-tailing ratio is 1:8 and 6%,9%,and 12%of CEV are added,the 28-days UCS of CPB is less than 1 MPa.Considering the heat storage capacity and cost price of backfill,the recommended proportion scheme of CPB material presents cement-tailing ratio of 1:6 and 12%CEV,and the most recommended heat storage/release temperature cycle range of CPB with added CEV is from 20 to 40℃.This work can provide theoretical basis for the utilization of heat storage backfill in green mines.

Diageneses and Their Influences on Reservoir Properties of Chang 2 Oil Member in Renshan Region, Zhidan Oilfield, Ordos Basin

1 Introduction Yanchang Formation in Upper Triassic,Ordos basin contains the most abundant hydrocarbon resources in North China(Wang et al.,2014).The sandstones are the most important oil-bearing reservoirs in Yanchang

Characteristics of Chang 2~1 Low PermeabilitySandstone Reservoir in Shunning Oil Field

Characteristics of Chang 21 low permeability sandstone reservoir of Shunning oil field are analyzed and evaluated based on the data of well logging and experiment. The result shows that 1) the Chang 21 low permeability reservoir belongs to the classification of middle-to-fine sized feldspar sandstone, with its components being low in ma- turity, deposited in distributary rivers in the front of the delta; 2) the reservoir is obviously dominated by a low or a very low permeability with a linear variation tendency different from that of the ultra-low permeability reservoir; 3) the spa- tial variation in lithology and physical properties of the reservoir are controlled by the sedimentary facies zones, and 4) the physical property of the reservoir is significantly influenced by clastic constituents and their structure, and the con- stituent of cement materials and their content. The result also shows that the diagenesis action of the reservoir is quite strong in which dissolution greatly modified the reservoir In addition, the inter-granular dissolved pores are the mainly developed ones and the micro-structure is dominated by the combination of middle-to-large sized pores with fine-to-coarse throats. Finally, the radius of the throats is in good exponential correlation with permeability and the seepage capacity comes from those large sized throats.

A quantitative evaluation for well pattern adaptability in ultra-low permeability oil reservoirs:A case study of Triassic Chang 6 and Chang 8 reservoirs in Ordos Basin

Based on the previous studies and development practice in recent 10 years, a quantitative evaluation method for the adaptability of well patterns to ultra-low permeability reservoirs was established using cluster analysis and gray correlation method, and it includes 10 evaluation parameters in the four aspects of optimal evaluation parameters, determination of weights for evaluation parameters, development stage division, and determination of classification coefficients. This evaluation method was used to evaluate the well pattern adaptability of 13 main ultra-low permeability reservoirs in Triassic Chang 6 and Chang 8 of Ordos Basin. Three basic understandings were obtained: Firstly, the well pattern for ultra-low permeability type-I reservoirs has generally good adaptability, with proper well pattern forms and well pattern parameters. Secondly, square inverted nine-spot well pattern is suitable for reservoirs with no fractures; rhombic inverted nine-spot injection pattern is suitable for reservoirs with some fractures; and rectangular well pattern is suitable for reservoirs with rich fractures. Thirdly, for the ultra-low permeability type-Ⅱ and type-Ⅲ reservoirs, with the principles of well pattern form determination, the row spacing needs to be optimized further to improve the level of development of such reservoirs.

Characteristics of Sb6Te4/VO2 Multilayer Thin Films for Good Stability and Ultrafast Speed Applied in Phase Change Memory

The Sb6 Te4/VO2 multilayer thin films are prepared by magnetron sputtering and the potential application in phase change memory is investigated in detail. Compared with Sb6 Te4, Sb6 Te4/VO2 multilayer composite thin films have higher phase change temperature and crystallization resistance, indicating better thermal stability and less power consumption. Also, Sb6 Te4/VO2 has a broader energy band of 1.58 eV and better data retention （125℃ for 103/）. The crystallization is suppressed by the multilayer interfaces in Sbf Te4/VO2 thin film with a smaller rms surface roughness for Sbf Te4/VO2 than monolayer Sb4Te6. The picosecond laser technology is applied to study the phase change speed. A short crystallization time of 5.21 ns is realized for the Sb6Te4 （2nm）/VO2 （8nm） thin film. The Sb6 Te4/VO2 multilayer thin film is a potential and competitive phase change material for its good thermal stability and fast phase change speed.

Paraffin–CaCl_(2)·6H_(2)O dosage effects on the strength and heat transfer characteristics of cemented tailings backfill

The challenge of high temperatures in deep mining remains harmful to the health of workers and their production efficiency The addition of phase change materials (PCMs) to filling slurry and the use of the cold storage function of these materials to reduce downhole temperatures is an effective approach to alleviate the aforementioned problem.Paraffin–CaCl_(2)·6H_(2)O composite PCM was prepared in the laboratory.The composition,phase change latent heat,thermal conductivity,and cemented tailing backfill (CTB) compressive strength of the new material were studied.The heat transfer characteristics and endothermic effect of the PCM were simulated using Fluent software.The results showed the following:(1) The new paraffin–CaCl_(2)·6H_(2)O composite PCM improved the thermal conductivity of native paraffin while avoiding the water solubility of CaCl_(2)·6H_(2)O.(2) The calculation formula of the thermal conductivity of CaCl_(2)·6H_(2)O combined with paraffin was deduced,and the reasons were explained in principle.(3) The“enthalpy–mass scale model”was applied to calculate the phase change latent heat of nonreactive composite PCMs.(4)The addition of the paraffin–CaCl_(2)·6H_(2)O composite PCM reduced the CTB strength but increased its heat absorption capacity.This research can give a theoretical foundation for the use of heat storage backfill in green mines.

Evaluation of reservoir environment by chemical properties of reservoir water‒A case study of Chang 6 reservoir in Ansai oilfield,Ordos Basin,China

The Ordos Basin is the largest continental multi-energy mineral basin in China,which is rich in coal,oil and gas,and uranium resources.The exploitation of mineral resources is closely related to reservoir water.The chemical properties of reservoir water are very important for reservoir evaluation and are significant indicators of the sealing of reservoir oil and gas resources.Therefore,the caprock of the Chang 6 reservoir in the Yanchang Formation was evaluated.The authors tested and analyzed the chemical characteristics of water samples selected from 30 wells in the Chang 6 reservoir of Ansai Oilfield in the Ordos Basin.The results show that the Chang 6 reservoir water in Ansai Oilfield is dominated by calcium-chloride water type with a sodium chloride coefficient of generally less than 0.5.The chloride magnesium coefficients are between 33.7 and 925.5,most of which are greater than 200.The desulfurization coefficients range from 0.21 to 13.4,with an average of 2.227.The carbonate balance coefficients are mainly concentrated below 0.01,with an average of 0.008.The calcium and magnesium coefficients are between 0.08 and 0.003,with an average of 0.01.Combined with the characteristics of the four-corner layout of the reservoir water,the above results show that the graphics are basically consistent.The study indicates that the Chang 6 reservoir in Ansai Oilfield in the Ordos Basin is a favorable block for oil and gas storage with good sealing properties,great preservation conditions of oil and gas,and high pore connectivity.

Factors controlling the reservoir accumulation of Triassic Chang 6 Member in Jiyuan-Wuqi area,Ordos Basin,NW China

In the Triassic Yanchang Formation, Jiyuan-Wuqi area, Ordos Basin, the Chang 6 reservoir is contacted to the Chang 7 high-quality source rock, but the oil pools are unevenly distributed, and complex in oil and water distribution. Through cores observation and fracture statistics, combined with comprehensive analyses of physical property, mercury injection, logging and geochemical data, and comparisons of the sandbodies scales, reservoir physical properties, argillaceous laminae and fractures between source and reservoir in the eastern and western oil-bearing areas and in the central water producing area, it is found that the hydrocarbon accumulation patterns are different in the eastern, central and western areas, and the characteristics of hydrocarbon migration under the background of double-provenance were sorted out. The study results show that the crude oil in the eastern area has different Pr/Ph and sterane distribution from that in the western area. The oil and gas primarily migrated vertically. The high-quality source rocks and favorable source-reservoir-cap combinations lay the foundation for large-scale oil and gas accumulations. Vertically, the oil and gas enrichment is controlled by the scale of sandbody and the difference of physical properties, while on the plane, it is controlled by the connectivity of sandbodies, the argillaceous laminae between source rock and reservoir, the reservoir physical property and the fractures. The sandbodies of oil-rich zones in the eastern and western areas have large thickness, low shale content, good physical properties, weak heterogeneity, few argillaceous laminae and abundant fractures, all of which are favorable for the vertical migration and accumulation of oil and gas. In contrast, in the middle area with converging provenances, the reservoirs, composed of thin sandbodies, features rapid variation in lithology and physical properties, strong heterogeneity, poor continuity of sandbodies, abundant argillaceous laminae between source rock and reservoir, and few fractures, makes it difficult for the oil and gas to migrate vertically, and results in low oil enrichment degree ultimately. For the exploration of continental multiple-provenance tight reservoirs, not only the good-property source rocks and reservoirs, but more importantly the source-reservoir contact relationship and the effect of fractures on the hydrocarbon migration and accumulation should be considered.

鄂尔多斯盆地W102井区长6储层成岩作用研究

通过铸体薄片观察和电镜扫描等检验方法,对鄂尔多斯盆地劳山地区W102井区长6储层的储层特征及成岩作用作了研究。研究结果表明:W102井区长6储层的岩石类型主要为灰色细粒长石砂岩,储层为典型的低孔—超低孔、特低渗—超低渗储层。此外,主要成岩作用包括压实作用、胶结作用和溶蚀作用:成岩期间的压实作用为破坏性成岩作用,对储层物性的影响不具主导性;胶结作用复杂,对孔隙度的影响较大;溶蚀作用表现为建设性成岩作用,溶蚀率增大对储层孔隙度和渗透率的改善具有积极作用。

陕北志丹地区长_6—长_2油层组水退型三角洲沉积演化特征

根据测井、录井资料,运用沉积学方法综合研究了陕北志丹地区中生界延长组长6—长2油层组沉积及演化特征。结论认为:长6—长2沉积期志丹地区为大型三角洲与大型湖泊沉积体系进退发育之地,形成了区内良好的生储盖组合与广泛分布的众多含油层系。在近南北向剖面上,长6—长2沉积组合自下而上、由北向南显示出三角洲不断向湖超覆,形成向上变粗的水退型沉积序列;沉积相带自北向南不断向湖中心推移,三角洲前缘大面积展布并多期次叠合,形成区内的沉积主体。三角洲前缘亚相可以进一步分为水下分流平原亚相与前缘河口亚相两大部分,骨干砂体分别为分流河道砂与河口坝砂;长6沉积期区内前缘河口亚相极为发育,到长2沉积时水下分流平原亚相扩大发展,三角洲平原亚相开始进入区内。

塞392区长6油藏水平井开发效果分析

水平井是通过扩大油层泄油面积来提高油井产量、提高油田开发效益的一项开发新技术,但是储层的物性、裂缝发育情况、水平井的完钻井方式、改造方式及举升方式直接影响水平井的开发效果,通过分析塞392区长6油藏特性和影响水平井开发效果的因素,针对影响因素提出有针对性的治理对策,提高该区水平井开发效果,提高油田开发水平。

靖边油田青高油区长_2、长_6油层组沉积相研究

靖边青高(青阳岔-高家沟)油区位于靖边油田东南部,长2、长6油层为该区域的主力油层,以构造-岩性油藏为主,通过对该区域沉积相的研究,可以较好的预测砂体展布方向,为储层预测提供技术支撑,同时可以基于此开展对区域古环境的研究,对于研究古水动力及物源研究都有积极的意义。

鄂尔多斯盆地蟠龙地区长6储层四性关系研究

针对蟠龙地区长6储层四性关系的研究与认识不足,利用蟠龙地区的测井数据、录完井数据、岩心分析和化验资料等资料进行整理与分析,对研究区储层岩性、物性、电性与含油性特征及其相互间的关系进行了研究。研究结果表明,①蟠龙地区长6油层组以长石砂岩为主;②储层平均孔隙度为8%,平均渗透率为0.79×10-3μm 2,属于低孔特低渗至低孔超低渗储层;③录井中岩心以油迹含油级别为主;④结合岩心测试资料建立了储层参数测井解释模型,并最终确定有效储层物性下限为:渗透率0.15×10^(-3)μm^(2),孔隙度5.5%,电阻率20Ω·m,声波时差215μs/m。研究了储层四性基本特征及其关系,并得出了蟠龙地区储层物性和含油性的电性解释图版,为后续蟠龙地区油层解释以及探明储量参数的确定提供了依据。

致密砂岩孔隙演化及其对含油饱和度的影响——以鄂尔多斯盆地甘泉地区三叠系延长组长6—长8段储层为例

致密砂岩储层的微观非均质性强,含油饱和度变化大。为了探究致密砂岩储层成岩过程中孔喉大小分布的变化及其对含油饱和度的影响,以鄂尔多斯盆地甘泉地区三叠系延长组长6—长8段致密砂岩储层为例,利用铸体薄片、扫描电镜、高压压汞等测试手段,定量计算了成岩作用对孔隙度的影响。在此基础上,以孔喉参数的统计模型为约束条件,建立了主要成藏期孔喉大小分布模型,利用积分方法计算出了主要成藏期的可动流体饱和度。甘泉地区长6—长8段致密砂岩储层在早成岩期—中成岩期受到强烈的压实作用,平均压实减孔率为81.85%,胶结作用进一步使孔隙度平均降低11.00%左右,溶蚀作用虽然增加了孔隙空间,但增幅较小,平均为4.38%;主要成藏期开始(128 Ma)和结束(111 Ma)对应的平均古孔隙度分别为13.82%和8.68%,大于最小流动孔喉半径(0.1μm)的孔喉体积占比低,可动流体饱和度为35.05%~93.27%。主要成藏期孔喉半径及可动流体饱和度偏低是含油饱和度低的原因之一。受储层自生黏土矿物对岩石润湿性的影响,现今含油饱和度值并未急剧降低。成藏时期孔喉大小分布模型计算油层可动流体饱和度为研究类似地区油气储层孔喉大小演化及其与含油饱和度的关系提供了一种可行的分析方法。

子长油田子128井区长6储层非均质性及其影响因素

针对子长油田子128井区长6油层组储层孔隙结构复杂、稳产率不高等问题,综合分析地质资料、测井资料,利用压汞实验、铸体薄片、扫描电镜等方法,深入探讨研究区长6油层组储层非均质性及其影响因素。结果表明,长6油层组的层内和层间非均质性自上部地层至下部地层逐渐增强,而平面非均质性逐渐减弱。沉积微相和成岩作用对储层非均质性具有控制作用,单期分流河道宽度变化越大、多期河道叠加宽度越小,储层非均质性越强。成岩作用对储层非均质性的影响利弊兼具。

鄂尔多斯盆地南212井区长6_(2)致密砂岩储层特征及其影响因素

为了明晰鄂尔多斯盆地南212井区延长组长62致密砂岩储层特征及其影响因素,综合铸体薄片鉴定、扫描电镜观察、高压压汞、核磁共振、X-衍射等分析测试资料,对储层岩石学、物性、孔隙结构特征、成岩作用及储层物性的控制因素进行研究。研究表明:研究区长6_(2)储层主要为长石砂岩和少量岩屑长石砂岩,为低孔—特低孔、特低渗储层,孔隙类型以粒间孔、长石溶孔为主,孔隙组合类型主要为溶蚀孔-粒间孔型,孔隙结构分为大孔-细喉型、中孔-微细喉型以及小孔-微喉型3种类型,中孔-微细喉型最为发育;成岩作用主要为压实压溶作用、胶结作用和溶蚀作用;储层物性受沉积环境与成岩作用的共同影响,在分流河道储层物性好,储层单砂体厚度越大,物性越好;压实压溶作用和胶结作用均对储层物性起破坏性作用,溶蚀作用对储层具有建设性作用。

延长油田化子坪油区长6油层CO_2驱油与封存潜力分析

为进一步探索CO_2捕集、利用与封存技术(CCUS)在延长油田化子坪油区长6油层应用的可行性,通过细管和长岩心驱油实验,分析了CO_2在长6油层的驱油潜力,从孔喉特征、渗流特征和力学特征三个方面对长4+5盖层的密封性进行综合评价的基础上,利用相关模型对CO_2封存潜力进行了分析。CO_2驱油和盖层密封性评价实验结果表明:延长油田化子坪油区长6油层CO_2驱为非混相驱,其在水驱基础上可进一步提高驱油效率28.83%,其中微孔隙、小孔隙、中孔隙和大孔隙的驱油效率分别提高33.25%、27.09%、26.71%和23.86%;长4+5盖层主要表现出中-小孔细喉道,束缚水饱和度极高,气相相对渗透率极低,突破压力和抗压强度高的特征,对CO_2地质封存具备良好的密封性。CO_2封存潜力分析结果表明:延长油田化子坪油区长6油层的CO_2有效封存量可达7.43×10~6t。

元214长4+5、长6油藏酸化措施适应性评价

酸化解堵措施是元214长4+5、长6油藏主要稳产增产措施之一。元214长4+5、长6油藏为多层系叠合油藏,不同层位之间在孔隙度、渗透率等方面均有差异,造成酸化措施效果的差异性。根据不同层位酸化解堵措施实施的效果,评价措施适应性,为油藏下步措施选井提供参考。

Pore structure differences of the extra-low permeability sandstone reservoirs and the causes of low resistivity oil layers: A case study of Block Yanwumao in the middle of Ordos Basin, NW China

The influence of pore structure difference on rock electrical characteristics of reservoir and oil reservoir was analyzed taking Triassic Chang 6 reservoir in Block Yanwumao in the middle of Ordos Basin as an example. The relationship between the pore structure difference and the low resistivity oil layer was revealed and demonstrated through core observation, lab experiments, geological research, well log interpretation and trial production etc. The results show that there were two kinds of oil layers in Chang 6 oil layer set, normal oil layer and low resistivity oil layer in the region, corresponding to two types of pore structures, pore type mono-medium and micro-fracture-pore type double-medium; the development of micro-fracture changed greatly the micro-pore structure of the reservoir, and the pore structure difference had an important influence on the rock electrical characteristics of the extra-low permeability sandstone reservoir and oil reservoir; the normal oil layers had obvious characteristics of pore-type mono-medium, and were concentrated in Chang 61, Chang 6232 and Chang 62; the low resistivity oil layers had obvious characteristics of micro-fracture-pore type double-medium, which were mainly distributed in Chang 612 and Chang 63. The mud filtrate penetrated deep into the oil layers along the micro-cracks, leading to sharp reduction of resistivity, and thus low resistivity of the oil layer; the low resistivity oil layers had better storage capacity and higher productivity than the normal oil layers.