The pore-fracture system properties of coalbed methane reservoirs in the Panguan Syncline,Guizhou,China

The Panguan Syncline contains abundant coal resources, which may be a potential source of coalbed methane. In order to evaluate the coalbed methane production potential in this area, we investi- gated the pore-fracture system of coalbed methane reservoirs, and analyzed the gas sorption and seepage capacities by using various analytical methods, including scanning electron microscopy （SEM）, optical microscopy, mercury-injection test, low-temperature N2 isotherm adsorption/desorption analyses, low- field nuclear magnetic resonance and methane isothermal adsorption measurements. The results show that the samples of the coal reservoirs in the Panguan Syncline have moderate gas sorption capacity. However, the coals in the study area have favorable seepage capacities, and are conductive for the coalbed methane production. The physical properties of the coalbed methane reservoirs in the Panguan Syncline are gener- ally controlled by coal metamorphism： the low rank coal usually has low methane sorption capacity and its pore and microfractures are poorly developed; while the medium rank coal has better methane sorption capacity, and its seepage pores and microfractures are well developed, which are sufficient for the coalbed methane＇s gathering and exploration. Therefore, the medium rank coals in the Panguan Syncline are the most prospective targets for the coalbed methane exploration and production.

Interlayer interference mechanism of multi-seam drainage in a CBM well:An example from Zhucang syncline

Based on the characteristics of the strong volatility of physical property in vertical direction, high gas content, high resource abundance and large exploitation potentiality of coal reservoir in Bide-Santang basin of Zhina coal field, we study the generation mechanism of interlayer interference, propagation rules of reservoir pressure drop and influencing factors of gas productivity in CBM multi-seam drainage in the paper. On the basis of the actual production data of X-2 well of Zhucang syncline in Bide-Santang basin,by simulating the gas production process of a CBM well under the condition of multiple seam with COMET3 numerical simulation software, we analyze the influencing factors of gas productivity during the process of multi-seam drainage, and illuminate the interlayer interference mechanism of multiseam drainage. The results show that permeability, reservoir pressure gradient, critical desorption pressure and fluid supply capacity of stratum have great influence on gas productivity of multi-seam drainage while coal thickness has little influence on it. Permeability, reservoir pressure gradient and fluid supply capacity of stratum affect the propagation velocity of reservoir pressure drop and thereby affect the final gas productivity. Moreover, the influence of critical desorption pressure on gas productivity of multiseam drainage is reflected in the gas breakthrough time and effective desorption area.

Geological characteristics and co-exploration and co-production methods of Upper Permian Longtan coal measure gas in Yangmeishu Syncline, Western Guizhou Province, China

Coal measure gas(also known as coal-bearing unconventional gas)is the key field and development direction of unconventional natural gas in recent years.The exploration and evaluation of coal measure gas(coalbed methane,coal shale gas and coal measure tight sandstone gas)from single coalbed methane has greatly expanded the field and space of resource evaluation,which is of positive significance for realizing the comprehensive utilization of coal resources,maximizing the benefits and promoting the innovation of oil and gas geological theory and technological advances in exploration and development.For the first time,in Yangmeishu Syncline of Western Guizhou Province,the public welfare coalbed methane geological survey project of China Geological Survey has been carried out a systematic geological survey of coal measure gas for the Upper Permian Longtan Formation,identified the geological conditions of coal measure gas and found high quality resources.The total geological resource quantity of coalbed methane and coal shale gas is 51.423×109 m3 and the geological resource abundance is up to 566×106 m3/km2.In this area,the coal measures are characterized by many layers of minable coal seams,large total thickness,thin to the medium thickness of the single layer,good gas-bearing property of coal seams and coal measure mudstone and sandstone,good reservoir physical property and high-pressure coefficient.According to the principle of combination of high quality and similarity of key parameters of the coal reservoir,the most favorable intervals are No.5-2,No.7 and No.13-2 coal seam in Well YMC1.And the pilot tests are carried out on coal seams and roof silty mudstone,such as staged perforation,increasing hydraulic fracturing scale and"three gas"production.The high and stable industrial gas flow with a daily gas output of more than 4000 m3 has been obtained,which has realized the breakthrough in the geological survey of coal measure gas in Southwest China.Based on the above investigation results,the geological characteristics of coal measure gas in the multi-thin-coal-seam-developed area and the coexploration and co-production methods,such as the optimization method of favorable intervals,the highefficiency fracturing and reservoir reconstruction method of coal measures,and the"three gas"drainage and production system,are systematically summarized in this paper.It will provide a reference for efficient exploration and development of coal measure gas in similar geological conditions in China.

DEVELOPMENT OF MESO-AND MICRO-SCALE STRUCTURES IN THE CHAMBA-BHARMAUR SYNCLINE, WESTERN HIMALAYA, INDIA

The Chamba\|Bharmaur syncline located in between Zanskar range in the north and Dhauladhar\|Pirpanjal range in the south , in the Chamba district of Western Himachal Pradesh. The rocks constituting Chamba\|Bharmaur syncline belong to Precambrian to Lr. Triassic (Rattan, 1973) and represent the southern extension of the Tethyan facies of the Zanskar Tethys Himalayan sequence (Thakur, 1998). The geological and structural mapping in the Chamba\|Bharmaur syncline reveal that the area comprises of various litho\|units which show imprint of various phases of deformation. Three main phases of deformation DF\-1, DF\-2 and DF\-3 have affected the rocks of the Chamba\|Bharmaur syncline. The earliest recognisable deformational structures of the area are tight isoclinal folds appressed with long drawn out limbs and thickened hinges have experienced buckle shortening of 80%. They have been rendered intrafolial folds in many places; only a few of them show disharmony. The folds initiated in the multilayered sequences are generally controlled in their distribution and wave\|length by more competent members of the sequence.

The Last Pterosaurs: First Record from the Uppermost Maastrichtian of the Tremp Syncline (Northern Spain)

Pterosaur bones are for the first time reported from the Tremp Syncline （Spain） and the southern Pyrenees. They come from the Torrebilles-2 site （Isona, Lleida Province） in the upper Maastrichtian part of the Tremp Formation, which falls within the C29r magnetochron. Fragmentary long bones are referred to the Pterosauria based on their cortical thinness, micro-architecture, and histological features. They belong to very large to possibly giant individuals. The most complete specimen is possibly a partial right femur. The review of the Maastrichtian pterosaur record shows that only a few specimens can be referred to the C29r （which contains the K/Pg boundary）. The identification of fragmentary remains could improve our knowledge about the abundance and distribution of these flying sauropsids just before the end-Cretaceous mass extinction.

Benthic Foraminiferal and Calcareous Algae Assemblages in the Tirgan Formation (Urgonien Facies Type) in South Flank of Ghorogh Syncline (North of Chenaran), NE Iran

In this research, the Tirgan Formation in the south flank of Ghorogh Syncline (north of Chenaran), northeastern Iran with the thickness of 251 was studied. This section consists of limestone, marly limestone and shale with impressions of echinoderms toxasteridae family, many of foraminifera from orbitolinidae family and also lots of calcareous algae that create facies variation along with other non-skeletal allochems. Micropaleontological investigation has been carried out on 90 thin-sections. These criteria reveal that an equivalent of the Urgonian facies type (in France-Swiss area) and open marine, low depth sedimentary basin are extended in the Kopet-Dagh basin. In this article, we tried to introduce some of the important foraminiferal and calcareous algal assemblages of this area.

Petrography and geochemistry of Paleocene-Eocene limestones in the Ching-dar syncline,eastern Iran

The Ching-dar syncline is located to the west of the city of Birjand, in the east of han. The ca. 500 m thick studied section at the eastern flank of the syncline contains a sequence of almost continuous shallow- marine limestones that exhibit no major sedimentary breaks or evidence for volcanic activity. Skeletal grains consist of large benthic foraminifera and green algae whereas non-skeletal grains are mostly peloids and intraclasts. They were deposited on a shallow-marine carbonate ramp. The limestones have undergone extensive diagenetic processes with varying intensities, the most important of which are micritization, cementation, compaction （chemical and mechanical）, internal filling and stylolitization. Chemical analysis of the limestone samples revealed high calcium and low magnesium content. Major and minor element values were used to determine the original carbonate mineralogy of these lime- stones. Petrographic evidence and elemental values indicate that calcite was the original carbonate mineral in the limestones of the Ching-dar syncline. The elemental composition of the Ching-dar car- bonates also demonstrates that they have stabilized in a meteoric phreatic environment. Variation of Sr/ Ca vs. Mn values suggests that diagenetic alteration occurred in an open geochemical system.

Microbial degradation and its influence on components of coalbed gases in Enhong syncline, China

Coalbed gases (CBG) in Enhong syncline are characterized by high concentration of C2+ (C2-5 ), with the highest content of ethane over 30%. However, the concentrations of C2+ are not evenly distributed in the syncline. Based on the analysis of δ13C1 , δ13C2 , δ13C3 , δ13CO2 , δDCH4 of CBG and their origin diagrams in the normal and abnormal areas, this research shows that gases in both areas are thermogenic gases and the reason for the uneven distribution of C2+ is that the microbial degradation action on gases is stronger in the normal area than in the abnormal area. The secondary biologic gases in the normal area are mainly characterized by that the carbon isotopes become obviously lighter in methane and become heavier in ethane, whereas the molecular and isotopic compositions of CO2 change little. These features indicate that the secondary biologic gases are mainly generated by the microbial degradation of C2+ , not generated by the reduction of CO2 . The degradation process is selective to make the residual ethane being enriched in 13C and the generated methane rich in 12C.

CBM geology conditions study of Gemudi syncline,Western Guizhou Province

Through the analysis of the surrounding rock, coal seam burial depth, coal quality and hydrologic geological condition, the methane-bearing property characteristics of the coal reservoir in the Gemudi syncline were elucidated. Most of the wall rock of the coal reservoir is mudstone and silt, which is a favourable enclosing terrane. Burial depth of the main excavating coat seam is moderate. The groundwater activity is thin, and there are absolute groundwater systems between each coal seam, which make poor intercon- nections to accelerate CBM enrichment. In our research, the area coal reservoir meta- morphosis is high, CBM content is high, hole-cranny system development degree is high, and permeability of the great mass of the main coal seam exceeds 0.1×10^-3 μm2, The result demonstrates that the southeast of the Gemudi syncline has the best conditions for prospecting and exploiting CBM.

四川盆地南部向斜区二叠系岩溶孔隙型石灰岩储层成因与天然气勘探新领域

随着油气勘探程度不断提高,勘探方向逐渐从构造高部位往向斜区拓展。但是,传统认识认为向斜区岩性一般较致密,寻找向斜区优质储层成为其油气获得勘探突破的关键因素之一。为此,以四川盆地南部向斜区中二叠统茅口组石灰岩为例,基于钻井岩心、薄片、测井以及地球化学等资料综合分析,开展了向斜区孔隙型石灰岩储层特征及成因研究,并建立了储层发育模式,指出了天然气勘探新方向。研究结果表明:(1)四川盆地南部向斜区茅口组发育岩溶孔隙型碳酸盐岩储层,储层岩性主要为泥晶—亮晶生屑石灰岩和亮晶生屑石灰岩,储集空间主要为生物体腔孔、生物铸模孔及粒内溶孔等组构选择性溶蚀形成的孔隙;(2)研究区茅口组储层平均孔隙度为4.07%,平均渗透率为0.273 mD,孔隙度与渗透率有明显的正相关关系,为典型的孔隙型储层;(3)茅口组储层段的铝、钪、锆及总稀土元素含量较低,锰和铁含量也较低,碳同位素值位于中二叠世海水沉淀方解石碳同位素值分布范围内,氧同位素呈现出一定的负偏;(4)茅口组岩溶孔隙型储层的形成与沉积期微地貌及高频层序控制的准同生期岩溶有关,溶蚀流体主要为大气淡水。结论认为,岩溶孔隙型储层在盆地内普遍发育,且该类储层远离不整合面,受沉积古地貌、沉积相带控制的准同生期岩溶改造,因此,天然气勘探思路需要向“有利沉积相带规模控储”方向转变,向斜区将是盆地内未来天然气勘探的重要新领域。

基于无线随钻测量式超短半径水平井钻井技术

为了解决油田开发后期老井产量低、含水高的难题,通过采用小尺寸高弯曲度MWD随钻仪器配合高造斜率螺杆的方法,实现了在老井上部井段侧钻出超短半径水平井,攻关研究大曲率造斜和水平钻进的技术,通过设计研发小尺寸高弯曲度MWD随钻仪器、高造斜率螺杆等专用工具,并结合现场施工要求,创新基于无线随钻测量方式的超短半径水平井钻井技术。结果表明:该技术具有施工效率高、实时监测井下参数、轨迹控制精度高等优点,可以实现老井剩余油储层定向挖潜改造,扩大泄油面积,改善油井生产条件,提高采收率。

三峡库区万县复向斜构造特征及其与地质灾害分布关系

万县复向斜位于川东褶皱带与大巴山-大洪山构造带复合部位,前人侧重于基础地质及页燃气勘探相关领域的研究,对于万县向斜局部构造特征与地质灾害的内在关系的研究尚少.本文在野外地质调查研究的基础上,利用部分滑坡的勘察资料,采用构造地质与工程地质的分析方法,深入研究了万县向斜局部构造对该区域地质灾害的控制作用,将万县向斜内部分为:西部NE向构造叠加构造区域;中部故陵向斜轴迹NE向区域;东部故陵向斜轴迹近EW向区域(也是故陵向斜翘倾消亡部位).与局部构造相对应,将内部地质灾害同样划分为西部、中部和东部3个区域进行研究,得出如下结论:西部地质灾害发育规模小,主要集中于局部纵谷地段;中部地质灾害集中于长江北岸,岩层陡缓倾角转化带的存在对地质灾害的规模起到了控制作用;东部地质灾害集中于长江南岸,除岩层陡缓倾角转化带的存在对地质灾害的规模起到了主要控制作用以外,斜坡坡长和岩层产状中陡倾的特点对地质灾害的发生同样具有重要的控制作用.本次研究阐明了万县复向斜内部构造特征与该地区地质灾害的内在联系,对研究区域内地质灾害的预测预报提供了一定的参考和依据.

渝东武隆向斜构造特征及页岩气保存条件研究

基于高分辨率地震数据,结合野外照片、节理数据等资料,利用断层相关褶皱理论,系统解剖了武隆向斜的构造特征,恢复了其应力期次,并以武隆向斜内部胡家园断层为例探讨了SN向构造对研究区页岩气保存条件的影响。将武隆向斜划分为3个构造层:基底构造形变层控制了盖层主体形态;下构造形变层主要发育NE向逆冲断层;中构造形变层局部发育断弯褶皱形态。武隆向斜中、下两套构造形变层的主体形态受SN向的胡家园断层改造强烈,中燕山期,受NW向挤压应力作用,原始武隆向斜逐渐形成,晚燕山期受左行扭动作用的EW向挤压应力作用,形成SN向胡家园断层,将原始武隆向斜分为东、西两个区域,其中东部火炉向斜页岩气构造保存条件破坏强烈,西部武隆向斜构造改造较弱,构造封闭性强,有利于页岩气储存,是下一步勘探的主要有利目标。

致密砂岩气藏与页岩气藏展布模式

在阐述美国和中国致密砂岩气和页岩气资源潜力和年产量的基础上,系统梳理致密砂岩气藏与页岩气藏展布的研究沿革,分析页岩气藏、致密砂岩气藏展布特征及致密砂岩气成因类型。研究表明:(1)美国致密砂岩气在天然气总产量中占比由2008年的35%降至2023年的8%左右;美国页岩气2023年产量为8310×10^(8)m^(3),在天然气总产量中占比由2000—2008年的5%~17%升至2023年的70%以上。(2)中国致密砂岩气占天然气总产量比例由2010年的16%升至2023年的28%以上;2012年中国开始生产页岩气,2023年产量达250×10^(8)m^(3),约占天然气全国总产量的11%。(3)页岩气藏展布模式为连续型,根据页岩气藏是否有断层切割及断距与气层厚度的关系,连续型页岩气藏可分为连续式和断续式两种。(4)与以往大部分学者认为致密砂岩气藏展布模式为连续型的认识不同,致密砂岩气藏展布模式不是连续型;根据圈闭类型,致密砂岩气藏可分为岩性型、背斜型和向斜型3种。(5)中国3大克拉通盆地和埃及Obavied次盆的致密砂岩气为煤成气,美国阿巴拉契亚盆地和阿曼迦巴盐盆地的致密砂岩气为油型气。

深层常压页岩气富集机制研究——以涪陵页岩气田白马区块为例

目前,我国南方海相页岩气勘探开发主要聚焦在中深层超压背斜,而针对深层常压页岩气富集机制的研究较为薄弱。以白马向斜南斜坡Y162井为例,在系统评价五峰组-龙一1亚段页岩气赋存状态及储层孔隙结构的基础上,与焦石坝背斜JY11-4井中深层异常高压页岩气成藏特征对比,结果表明:1)白马向斜五峰组-龙一1亚段页岩气含量略高于焦石坝背斜,是典型以吸附气为主的深层常压气藏;2)白马向斜页岩孔隙度明显低于焦石坝背斜,且孔隙度与TOC呈正相关,单位TOC比表面积更高;3)地层抬升幅度小,远离大断裂带,受构造活动影响小,断裂欠发育,构造保存条件较好,来自白马向斜核部页岩气的顺层扩散对斜坡区页岩气藏进行气源补充,是斜坡区页岩气维持常压、最终形成以吸附气为主的深层常压向斜型页岩气富集的关键因素。

向斜构造区特厚煤层开采覆岩结构稳定性及突水压架机理

针对陕西省永陇矿区褶曲构造带突水压架事故频发问题,以陕西省郭家河煤矿为工程背景,采用现场调研、物理实验与理论分析的方法,确定了导致工作面突水压架的主要含水层,得出了向斜构造区煤层开采覆岩破断失稳特征,建立了考虑承压水作用的覆岩结构力学模型,推导了工作面突水压架的临界水压力,揭示了向斜构造区突水压架机理。研究表明:①1303、1304、1308等已开采工作面在向斜轴部区域均发生过突水压架事故,宜君组岩层是导致工作面突水事故的主要含水层,煤层之上102.5 m处厚度为28.53 m的中粒砂岩为隔水关键层。隔水关键层断裂后,其上部100.51 m载荷层同步破断,导水裂隙带导通宜君组含水层。②在向斜构造区俯采阶段,顶板覆岩具有多层亚关键层并形成多离层区。向斜轴部岩层破断角竖直发育,顶板破坏程度最高,压架风险最大。③顶板突水致使覆岩结构失稳是导致压架事故发生的关键。承压水对顶板岩层稳定性的影响主要表现为:增加了覆岩载荷传递的连续性,降低了组合亚关键层的承载能力;构成了组合亚关键层的附加载荷。④防止突水压架所需的支护阻力随承压水压力的增大而加速增加,工作面发生突水压架事故的临界承压水压力为0.98 MPa。控制导水裂隙带发育高度与降低宜君组承压水压力是保证工作面不发生压架事故的关键。

“泰山震”的震中在郯庐断裂带安丘地区的证据

“泰山震”发生于公元前1831年,是中国史料记载的最早的历史地震。据《竹书纪年》记载:夏帝发七年(公元前1831年),当名为“发”的皇帝正在登泰山时,发生了一次强地震。因这次地震使皇帝受到了惊吓,因此,被名之为“泰山震”而首次记载下来。显然,名为“发”的皇帝受地震恐吓的地理位置是泰山坡麓。由于在泰山及其附近,地震地质学家一直未找到“泰山震”的地震地质记录。因此,“泰山震”的震中和震级一直是个谜。重新观察已发现的地震地质遗迹,结合一系列的测试、实验与剖析,本研究为“泰山震”是震中处在郯庐断裂带内安丘地区的强烈的历史地震提供了证据。首先,在距泰山以东约200 km远的郯庐断裂带安丘—夏庄盆地内的全新世湖沼相软土层中,存有震陷向斜与同震微断层等宏观的地震事件遗迹,它们记录的震中烈度Ⅸ度、震级达M7.0;二是借助于^(14)C同位素年龄测定结果,结合计算相关土层的沉积时间,而获得了极为接近公元前1831年的发震时间(公元前1827年);三是依据华北地震烈度衰减模型,计算出该地震在泰山的衰减烈度为Ⅵ度。中国地震烈度表显示,Ⅵ度烈度完全使人站立不稳或惊逃户外,这符合当年登山皇帝受地震惊恐的史料记录。

重庆酉阳龙潭槽谷和毛坝向斜大气降水氢氧稳定同位素变化特征

为深入探究重庆市东南部武陵山龙潭槽谷和毛坝向斜两个相邻地形区大气降水中δ^(18)O、δD的特征及其影响因素,文章基于两个水文年(2 020.06-2 022.05)在重庆市酉阳县龙潭槽谷(海拔333 m)和毛坝向斜(海拔1 140 m)降水δ^(18)O和δD的采样数据,建立了两地的大气降水线,分析两地大气降水氢氧稳定同位素的变化特征及影响因素。结果表明:(1)龙潭槽谷和毛坝向斜大气降水线的斜率和截距均大于全球大气降水线。大气降水δ^(18)O和δD具有明显的季节变化,雨季(5-10月)偏负,旱季(11月至次年4月)偏正。两地大气降水δ^(18)O表现出显著的降水量效应,温度效应的影响较弱。(2)龙潭槽谷大气降水线的斜率和截距小于毛坝向斜,两地大气降水线的差异主要受控于水汽凝结时的温度和蒸发条件。(3)龙潭槽谷大气降水中的δ^(18)O和δD的平均值较毛坝向斜偏正。d-excess的结果表明,龙潭槽谷δ^(18)O和δD存在微弱的云下二次蒸发。同次降水过程中龙潭槽谷大气降水δ^(18)O总体上较毛坝向斜降水δ^(18)O偏正,这表明龙潭槽谷和毛坝向斜两地的大气降水δ^(18)O受高程效应影响。(4)年际变化上,龙潭槽谷和毛坝向斜两地大气降水δ^(18)O的变化主要受印度洋水汽输送比例的影响。2020年夏季,印度洋水汽到达研究区的比例为76%,降水δ^(18)O偏负;2021年夏季,印度洋水汽到达研究区的比例为52%,降水δ^(18)O偏正。研究结果对增进西南岩溶槽谷区水循环过程的认识和今后展开龙潭槽谷和毛坝向斜两地生态水文过程的研究具有重要的意义。

基于Web of Science的岩溶碳循环及碳汇效应研究动态分析

为了解岩溶碳循环及碳汇效应研究热点和发展方向,基于Web of Science核心合集引文索引数据库,对1997年1月1日-2023年6月30日间的573篇文献进行了文献计量学引文分析。利用Cite Space软件对关键词频率、国家(地区)和机构分布、作者影响、研究热点、共被引文献以及主题演变进行了分析。结果表明,以刘再华为核心的研究团队继承和发扬了袁道先提出的岩溶作用参与全球碳循环并具有碳汇效应的观点,并提出了偶联碳酸盐岩风化碳汇模型,极大推动了岩溶碳汇的研究。关键词聚类的时间线图和关键词时区图清楚地展现了该领域的发展动态,可认为岩溶碳循环及碳汇效应领域经历3个发展阶段:1)1997-2006年的起步阶段,粗略估算了全球碳酸盐岩风化回收大气CO_(2)的量为0.110~0.608 Gt C·a^(-1),占全球碳遗漏的15%~30%;2)2007-2014年的碳酸盐岩化学风化研究快速发展阶段,主要关注不同流域在外源酸、径流条件及植被覆盖对碳酸盐岩风化的影响;3)2015年之后以大气-生物-土壤-水-基岩为系统的岩溶关键带理论指导下的碳循环及碳汇效应研究新阶段,考虑了水生生物光合作用、气候变化及土地利用变化等条件下岩溶碳循环及碳汇效应。

鄂尔多斯盆地西缘北段构造地质大剖面解析及棋盘井向斜构造成因新解

西缘冲断带作为鄂尔多斯盆地的西部边界,地处众多不同性质构造单元的过渡区域,其地质特征十分复杂。近年来,西缘冲断带的油气勘探领域不断拓宽,多期次的构造运动影响了油气从生成、运聚到被破坏的整个过程,对这些构造运动产生的构造变形样式和过程的研究可以为进一步油气勘探奠定基础。本文选取鄂尔多斯盆地西缘北段一条最新处理的近东西向高精度二维地震测线,结合钻井以及露头资料对其进行精细解析和刻画,并运用2D-move软件对解析后的剖面进行反演与正演模拟。结果表明:1)鄂尔多斯盆地西缘北段棋盘井镇地区的向斜构造为基底复合构造楔向东楔入形成,向斜核部地层加厚与桌子山—横山堡断裂的活动有关;2)过鄂尔多斯盆地西缘北段的构造地质剖面现今长度120 km,经过反演平衡恢复后的剖面长度为137.68 km,累计构造缩短量17.86 km,整体构造缩短率约13%,其中燕山期的缩短量最大,缩短量12.72 km,缩短率为10%;3)根据地层接触关系及构造演化模拟可知棋盘井向斜的形成时间大致在燕山中期,银川地区在该时期为高部位隆起。