Tectonic Evolution of the Palaeo——Tethys in Changning——Menglian Belt and Adjacent Regions,Western Yunnan

The Changning - Menglian belt , located between the Baoshan - Gengma massif and the Simao - Lincang massif in Western Yunnan , preserves the complete record of a suture zone and the most continuous record of deep water sedimentation , representing the main branch of the Palaeo - Tethys polyisland ocean in the Hercynian - Indo-sinian stage .This belt could be further subdivided into three tectono - lithofacies zones . In the east zone , terrigenous elastics , argillaceous ,marl-argillaceous and silicate sedi-ments lie on the metamorphosed Early Palaeozoic base ment in concealed unconformity , representing deep water sediments on a passive continental margin . The central zone , although the basement rocks are absent from outcropping here , includes a contemporary complex of various sedimentary types , among them one type is of deep ocean sediments represented by radiolarian bedded chert , appearing from at least early Early Devonian to the Middle Triassic . Another type includes pure carbonates of the Early Carboniferous to the Late Permian , a type of shallow water carbonate platform on seamount or oceanic plateau within an ocean basin . In the west zone , the Permo - Carboniferous terrigenous elastics , argillaceous and silicate sediments appear again -representing the passive continental slope sedimentation in the east of the Baoshan - Gengma massif .As the Permo-Carboniferous rock types,sedimentary environments and palaeontological characters of the east and west zones are quite similar , we hold that these two zones were originally formed all on the eastern continental slope of the Baoshan - Gengma massif , and were separated due to eastward thrust later in the Indosinian orogeny . Intense thrust compacting also resulted in tectonic melange in the central zone , which is displayed by shallow water carbonates overlapping on or embedded in deep water volcanics . In the Lancangjiang belt , the Permo - Carboniferous are very complicated in sedimentary types which include island arc volcanics , deep water turbidites, silicolites and shallow water carbonates , representing the active continental margin in the west of the Simao massif. Whether there existed by Early Permi an, a Lincang magma tic arc still awaits further evidence . From the Late Permian,both the Changning-Meng-lian belt and the Lancangjiang belt experienced important sedimentary and volanic events which took place contemporaneously or penecontemporaneously but with different characters . Evidence for the Lincang magmatic arc began to be apparent , and the turbidite deep water basin in the Lancangjiang belt closed . Nevertheless , the Palaeo - Tethys oceanic basin , represented by the Changning - Menglian suture zone , existed until the Mid-dle Triassic . In the Late Triassic . massifs of Baoshan -Gengma ,Simao - Lincang ,collided and aggregated ,resulting in the disappearance of the Palaeo - Tethys ocean .

Possible link between long-term and short-term water injections and earthquakes in salt mine and shale gas site in Changning,south Sichuan Basin, China

Late at night on 17 June 2019,a magnitude 6.0 earthquake struck Shuanghe Town and its surrounding area in Changning County,Sichuan,China,becoming the largest earthquake recorded within the southern Sichuan Basin.A series of earthquakes with magnitudes up to 5.6 occurred during a short period after the mainshock,and we thus refer to these earthquakes as the Changning M6 earthquake sequence(or swarm).The mainshock was located very close to a salt mine,into which for^3 decades fresh water had been extensively injected through several wells at a depth of 2.7–3 km.It was also near(within^15 km)the epicenter of the 18 December 2018 M5.7 Xingwen earthquake,which is thought to have been induced by shale gas hydraulic fracturing(HF),prompting questions about the possible involvement of industrial activities in the M6 sequence.Following previous studies,this paper focuses on the relationship between injection and seismicity in the Shuanghe salt field and its adjacent Shangluo shale gas block.Except for a period of serious water loss after the start of cross-well injection in 2005–2006,the frequency of earthquakes shows a slightly increasing tendency.Overall,there is a good correlation between the event rate in the Shuanghe area and the loss of injected water.More than 400 M≥3 earthquakes,including 40 M≥4 and 5 M≥5 events,had been observed by the end of August 2019.Meanwhile,in the Shangluo area,seismicity has increased during drilling and HF operations(mostly in vertical wells)since about 2009,and dramatically since the end of 2014,coincident with the start of systematic HF in the area.The event rate shows a progressively increasing background with some fluctuations,paralleling the increase in HF operations.More than 700 M≥3 earthquakes,including 10 M≥4 and 3 M≥5 in spatially and temporally clustered seismic events,are correlated closely with active fracturing platforms.Well-resolved centroid moment tensor results for M≥4 earthquakes were shown to occur at very shallow depths around shale formations with active HF,in agreement with some of the clusters,which occurred within the coverage area of temporary or new permanent monitoring stations and thus have been precisely located.After the Xingwen M5.7 earthquake,seismic activity in the salt well area increased significantly.The Xingwen earthquake may have created a unidirectional rupture to the NNW,with an end point close to the NW-trending fault of the Shuanghe earthquake.Thus,a fault in the Changning anticline might have terminated the fault rupture of the Xingwen earthquake,possibly giving the Xingwen earthquake a role in promoting the Changning M6 event.

α-and β-diversity Change of Late Ordovician Hirnantia Fauna of Changning,Sichuan,Southwest China

A continuous Ordovician-Silurian boundary section from the upper Wufeng Formation through the Kuanyinchiao Formation to the lower Lungmachi Formation has been carefully measured and collected at Shuanghe of Changning, southern Sichuan Province. For the first time, the temporal changes of α- and β-diversities of the Hirnantia fauna have been discussed in great detail. The general trend of brachiopod diversity change, increasing upward, is consistent with the regional trend of the Yangtze Platform, which had been controlled by both intrinsic and extrinsic factors. However, the sudden drop of diversity for a short period in the upper Kuanyinchiao Formation might have been controlled by environmental factors rather than normal faunal turnover. Synecological analysis using numerical methods recognizes two brachiopod-dominated associations of the Hirnantia fauna, the Dalmanella-Kinnella Association and the Mirorthis Association, both living in an offshore, deeper water environment corresponding to BA3-upper BA4, particularly lower BA3.

Tectonic and geological setting of the earthquake hazards in the Changning shale gas development zone, Sichuan Basin, SW China

Hydraulic fracturing is a key technology in shale gas extraction,whether hydraulic fracturing induces earthquakes has become a hot topic in the public and the focus of scholars’research.The urgency of shale gas mining and the catastrophic nature of earthquakes highlight the urgent need to study this issue.The Changning anticline at the southern margin of the Sichuan Basin is a key area for shale gas exploitation.Taking this as an example,this paper applies the velocity model of the study area to reposition the M5.7 magnitude earthquake on December 16,2018 and the M5.3 magnitude earthquake on January 03,2019 and their aftershock sequence in this area.Using shale gas exploration drilling and reflection seismic data to carry out structural analysis,and recovering the tectonic geological setting of earthquake occurrence by restoring the formation process of the Changning anticline,to further explore the seismic mechanism.Our results show that the Changning anticline is a large basement fault-bend fold,and the displacement of the fault forming the anticline is 18 km,and the Changning anticline absorbs 33%of the fault slip.The Silurian Longmaxi Formation of the Changning anticline experienced larger-parallel shearing along underlying basement faults,forming a micro-fracture system.The footwall ramp of the basement fault is reactivated at present,earthquakes in this area mostly occur along the footwall ramp of the basement fault and above and below it.The anticlinal and synclinal hinge zones are also the earthquake concentration areas,but the earthquake magnitude decreases upwards along the kink-band,and small earthquakes below M2.0 occur in the Silurian Longmaxi Formation.So far,the earthquake in the Changning anticline mainly occurred in the southern limb of the anticline,which is a natural earthquake formed along the footwall ramp of the basement fault.The earthquakes in the Changning area are possible related to the geo-tectonic setting for the southeast outward compression of the Qinghai-Tibet Plateau at present,the moderate or large-scale earthquakes in the southwest Sichuan Basin are mainly due to the reactivation during late Quaternary of the earlier formed faults.It is suggested to carry out scientific monitoring of seismic activities in shale gas development zones.

Devonian to Triassic Successions of the Changning-Menglian Belt,Western Yunnan,China

Phanerozoic strata are distributed in several north-south trending zones in the central part of the Changning-Menglian Belt. Four types of Devonian to Triassic stratigraphic successions can be identified: (1) elastics with limestone lenses in the mid-section, changing up-section into alternations of fine elastics and cherts; (2) elastics with chert intercalations and limestone lenses, and topped by Permian basic volcanics; (3) elastics-basic volcanics-carbonates-clastics; and (4) limestones, dolomitic limestones-dark gray thin-bedded limestones, argillaceous limestones, mudstones and siliceous mudstones. Devonian to Triassic cherts occur in different horizons and different zones from east to west. These cherts are usually transitional to their neighboring elastics. There is no continuous Devonian to Middle Triassic chert sequence in the central zone of the Changning-Menglian Belt as Liu et al. (1991,1993) reported. Volcanics and the overlying carbonates described by some workers as 'seamount' sequences are more likely to have formed in a marine environment on continental crust. Succession (4) is newly recognized in the area from Menglai to Yong'an in Cangyuan County and further north to Padi of Gengma County. Basalts, cherts and elastics also appear in this area. Mid-Triassic (very probably Ladinian) radiolarians extracted from bedded cherts in the Ganzhejidi section indicate that they are in higher stratigraphic positions. The change from bedded cherts via siltstones to thick-bedded sandstones with thin-bedded fine intercalations in the Ganzhejidi section and (some other outcrops along the road from Cangyuan to Gengma) suggests a fundamental change of sedimentary environment caused by a rapid increase of a large quantity of detritus supply. These siliciclastic sediments are possibly syn-orogenic deposits.

Three-dimensional Geometry and Kinematics of the Changning Anticline in the Southern Sichuan Basin

In this study,we aim to clarify the structural characteristics and deformation process of the Changning anticline.We carefully interpret 38 two-dimensional(2D)seismic profiles in the study area and establish three-dimensional(3D)geometric and quantitative kinematic models of the Changning anticline.This study shows that the basement fault controls the formation of the Changning anticline.The fault slope of the main fault in the basement shows’steep in the upper and gentle in the lower’structural characteristics vertically,possessing obvious segmentary characteristics transversely and presents the overall characteristics of’steep in the east and gentle in the west’.Further analysis shows that the Changning anticline proceeds west and terminates at the boundary defined by current surface features but gradually disappears westward across the Mt.Huaying fault zone.Furthermore,we identified that deformation of the Changning anticline began during the early Yanshanian movement period.Under compressional stress from the southeast,the anticline slid forward along the basement fault until the end of the Yanshanian movement period,when the dominant WNW-ESE structure gradually emerged.Since the Himalayan movement period,a series of NE-trending structures have been formed in the anticline,owing to multi-directional compressive stress.

Research of the Activity of Earthquakes Induced by Water Injection of Salt Mining in Changning County,Sichuan Province

According to information from on-the-spot investigations, the tectonics of salt mining areas and digital seismic records, we studied the activity of earthquakes induced by water pumping in and out of the salt mines in Shuanghe town, Changning county, Sichuan Province. The study found that the rates of water injection and extraction in the Shuanghe salt mining region were evenly matched before April 2006 and earthquake activity was stable. On the other hand, shallow small and moderate earthquake numbers increased sharply after the water injection rate became much larger than the water extraction rate. Large injection over a long time may causes the permeation of water through pre-existing small fractures and micro-cracks in the Changning anticlinal and accelerate the rupture of micro tectonic formations in nearby regions, inducing small earthquake swarm activity. The Q value calculated by using digital earthquake records indicates a relatively inhomogeneous medium in this area. The results of the accurate location of small earthquakes show that sources are relatively shallow and are concentrated at a depth of 2km to 3km. Focal mechanism solutions reveal a normal dip-slip character of shallow earthquakes. All of these show certain characteristics of earthquake activity induced by water injection.

Geochemistry and Zircon LA-ICP-MS U-Pb Dating for the Ganlongtang-Longba Ophiolite,Changning-Menglian Suture Zone

The detailed geochemical research indicates that the tholeiitic basalts from Ganlongtang-Longba ophiolitic m（?）lange exhibit distinctive geochemical characteristics of high TiO2 and low K2O,and depletion of light rare earth elements.They should be originated from a depleted asthenosphere mantle, belonging to ancient oceanic crust ophiolitic volcanic rock association.Compared with the Longba tholeiitic basalt,the Ganlongtang tholeiitic basalt shows

滇西昌宁-孟连带二叠纪碎屑岩地层:存在问题和研究进展

滇西的昌宁-孟连带被认为是古特提斯在该地区的遗迹,对研究古特提斯的演化意义重大。然而,该带中不同来源的地层单元或层序片段之间的关系非常复杂,既有时代相同而岩性迥异的层段,也有时代不同而岩性相近的层段,在很大程度上影响了人们对古特提斯演化的深入了解。一些早期建立的岩组,受露头较差、构造复杂、大化石稀少等具体条件的限制,对其所含内容的定义比较粗略,包含了不同时代、不同环境形成的岩石层段。这种情况尤以当初划归二叠系的碎屑岩地层为甚。本文对1980年代1∶20万地质填图时建立的涉及二叠纪碎屑岩地层的岩组,即中北部耿马—沧源一带的南皮河组和南部澜沧—孟连一带的拉巴组,进行了解析,并结合笔者近年来所获得的化石、沉积岩石学、碎屑锆石年龄等材料和数据、以及大量的野外观察,梳理了两个岩组所包括的不同时代和岩性的岩片,重新厘定了南皮河组的内含,论述了拉巴组为何不宜再作为一个岩组使用,并建议对拉巴组所包含的在区域上可识别的岩片,可在进一步深入研究后再予以慎重命名。

常宁市古树资源调查与特征分析

古树是活的文物和自然的珍贵遗产,具有独特的文化价值、历史价值以及生态价值。以常宁市现存的古树资源为对象,结合实地调查数据,分别应用数据统计分析方法和ArcGIS,重点选取古树的种类特征、结构特征(胸径、树高、冠幅)、树龄与树木生长结构之间的相关性、树龄特征及其权属特征和空间分布特征6个方面进行分析。结果表明:常宁市现有古树共513株,隶属23科40属54种,其中优势种为樟树和枫香树;在结构特征方面,常宁市古树从总体上的树高、胸径和冠幅等分析均符合正态分布;古树树龄与胸径的相关性最大,且呈正相关性;在常宁市480株具有明确产权的古树中,集体产权的古树的数量最多,个人产权的古树数量为其次,国有产权的古树最少;常宁市的古树分布密集度存在明显的差异,总体上含2个高密度区和4个次密度区。常宁市的古树资源物种多样性丰富。

长宁和泸州地区构造变形差异性及其对页岩气保存的影响

长宁和泸州地区是四川盆地南部页岩气勘探的重点区块,分别位于盆—山结构的不同部位,其自元古代以来遭受多期构造改造作用,构造变形特征复杂。通过对研究区龙马溪组底界构造的精细地震解释和岩心裂缝统计分析,对比了长宁和泸州地区的构造变形特征和多尺度断层、裂缝发育特征的差异性,恢复了古生界以来的构造演化过程,为页岩气保存条件评价提供了依据。研究表明:长宁地区构造样式以断层传播褶皱为主,主要构造变形时期为燕山晚期,并在喜山期遭受大规模抬升剥蚀;泸州地区为典型隔档式褶皱,主要构造变形时期为燕山早期,构造形迹在喜山期受到一定改造。泸州地区变形强度总体低于长宁地区,其断层级次和裂缝发育程度较低,页岩气保存条件较好。上述结果丰富了页岩气保存条件的理论研究,为下一步四川盆地页岩气开发提供了帮助。

四川广元羊木-岩洞地区震旦纪-寒武纪界线地层序列及构造-沉积演化

绵阳-长宁拉张槽的形成机制及时间尚存在巨大争议,严重制约了灯影组油气勘探的部署。为更好地对拉张槽深水地层提供时代约束,深化拉张槽构造-沉积演化认识,基于露头描述、薄片观察、碳同位素测试,对广元地区4个露头剖面开展综合地层对比和沉积环境分析。岩石学及碳同位素特征表明,研究区实测4条野外露头剖面从下到上可划分为4个岩性段(Ⅰ~Ⅳ):岩性段Ⅰ为薄层泥质灰岩夹泥质白云岩条带,对应陡山沱组三段Shuram-Wonoka负偏段地层;岩性段Ⅱ以黑色页岩为代表,可对比陡山沱组四段;岩性段Ⅲ为块状白云岩-硅质岩序列,属于灯影组同期地层;岩性段Ⅳ以薄板状硅质岩为特征,相当于麦地坪组。其中,灯影组二段早期—麦地坪期,研究区从块状白云岩逐步过渡为薄板状硅质岩,见垮塌体及滑塌揉皱,指示台地转换为斜坡-盆地沉积环境。这种加深的沉积趋势与中上扬子台地相区变浅至暴露的过程完全相反,指示断裂活动影响下快速沉降的过程。

常宁市古树资源特征及空间分布

【目的】古树是森林资源的重要组成部分,见证了自然地理和人文历史的变迁,与一个地区的自然环境与文化涵养密切相关。为更有效地推进湖南省常宁市的古树资源保护工作,对常宁市的古树资源特征及其空间分布进行调查分析。【方法】以常宁市古树为研究对象,通过实地调研获取研究数据,结合常宁市古树名木信息最新纠偏数据,对常宁市古树名木资源的种类组成、结构特征、生境与生长状况特征以及空间分布格局进行分析。【结果】常宁市现有古树共489株,隶属于27科43属62种,主要以樟科、壳斗科、大戟科为优势科,以樟属、秋枫属、枫香树属为优势属,以樟树、枫香树、重阳木为优势种,常宁市古树名木资源丰富,且具有一定的研究价值。从古树年龄结构来看,常宁市三级古树占比最大,为386株(占总数的78.94%),二级古树和一级古树次之,分别为73株(占总数的14.93%)和30株(占总数的6.13%);古树的树龄总体偏小,其中最大的树龄为815 a。从径级结构来看,常宁市古树的平均胸径为95.86 cm,平均树高为16.92 m,平均冠幅为11.67m。从空间分布格局来看,常宁市古树中分布于平坡、缓坡和斜坡的分别有306、131和21株;生长在红壤、黄壤和紫色土的分别有103、310和76株;有378株分布于海拔0~200m,有65株分布于海拔201~400m,有30株分布于海拔401~600 m,有16株分布于海拔601~800 m;生长于城区、乡村街道和远郊野外的分别有8、133和348株。从常宁市各乡镇古树分布数量来看,西岭镇、塔山乡和庙前镇是拥有古树数量最多的乡镇。从生长状况来看,生长势为正常株的古树共有472株,衰弱株的古树共有14株,濒危株的古树共有3株。【结论】通过对常宁市古树资源进行深入分析,掌握了常宁市古树资源特征与空间分布格局,其分布特征与坡度、土壤、海拔、人口密度有关,为提高古树资源保护工作效率提供了条件和依据。

绵阳-长宁“侵蚀槽”发育特征及其对油气成藏的控制作用

四川盆地绵阳-长宁“侵蚀槽”对震旦系-寒武系特大型天然气藏的形成和分布具有重要控制作用。基于最新钻井和地震资料进一步明确了绵阳-长宁“侵蚀槽”具有“北深南浅、南北分段、向南北开口”的平面展布特征和类似于现代侵蚀地貌的剖面特征。绵阳-长宁“侵蚀槽”可分为灯二段和灯四段两期“槽盆”,充填了较为完整的下寒武统麦地坪组-筇竹寺组,麦地坪组~筇竹寺组三段表现为超覆充填沉积,筇竹寺组四段表现为广覆式填平补齐沉积。对比研究表明绵阳-长宁“侵蚀槽”明显控制了优质烃源岩、规模优质储层和气藏的分布,“侵蚀槽”内部和两侧具备“上生下储”和“旁生侧储”的成藏配置关系,阆中、资阳和知新场地区是下一步油气勘探重点区域。

川南长宁气田上罗区块宁201-YS108井区页岩气储量评价

四川盆地南部的长宁-威远地区页岩气资源丰富、储层较好,但此前针对上罗区块宁201-YS108井区页岩气储层系统的储量计算和评价较少。以长宁页岩气田上罗区块宁201-YS108井区为研究对象,研究其地层特征、构造特征、沉积相特征和储层特征。经储量参数确定及有效储层划分,并经体积法计算吸附气储量、容积法计算游离气储量,确定了宁201井区新增探明含气面积为91.17 km^(2),YS108井区新增探明含气面积为68.47 km^(2),两井区合计新增页岩气探明储量为1361.80×10^(8)m^(3)。最后,宁201-YS108井区页岩气储量的评价结果显示,宁201-YS108井区五峰组-龙马溪组一段页岩气藏脆性矿物含量高、镜质体含量高、有机碳含量高、渗透率特低、埋藏深度为中深层、可采储量为大型。该区域储量条件除渗透率和孔隙度较低外,矿物和有机碳含量、埋藏条件和可采储量总体较好,页岩气勘探开发潜力较大。

昌宁茶产业发展现状及对策

茶产业是云南省保山市昌宁县的支柱产业,振兴茶产业是实现人民增收的重要途径之一,也是昌宁县实现乡村全面振兴的基础和核心。本文通过SWOT分析法研究昌宁茶叶产业的发展情况,从新质生产力的视角提出提升管理水平、建立互联网营销体系、提升茶叶加工水平、茶叶与文旅融合发展、增加优质广告的投放等方面的建议,以期为昌宁茶产业稳步发展提供参考。

Geochemistry of Triassic Siliceous Rocks of the Muyinhe Formation in the Changning-Menglian Belt of Southwest China

The Changning-Menglian belt, distributed over southwestern Yunnan Province in Southwest China, contains oceanic rocks that are considered to be remnants of the Paleotethys. This study observed Triassic siliceous rocks of the Muyinhe Formation in the Changning-Menglian belt and analyzed their geochemistry. The samples have high concentrations of SiO2（81.65 wt.%–88.38 wt.%; average： 84.99 wt.%±2.14 wt.%）. Most of the samples were plotted in the non-hydrothermal field on the Al-Fe-Mn diagram. Most of the samples were plotted in the continental margin field on the Fe2O3/TiO2-Al2O3/（Al2O3＋Fe2O3） and（La/Ce）N-Al2O3/（Al2O3＋Fe2O3） diagrams. Moreover, the samples show a flat REE（rare earth element） pattern normalized to NASC（North America shale composite）. These geochemical results, in addition to the lack of rhythmical bedding of the siliceous rocks, strongly suggest that the siliceous rocks are unlikely to represent pelagic deposits. Although previous studies have suggested that the siliceous rocks are pelagic deposits, the present results indicate that the extent of the pelagic ocean basins in the Paleotethys during the Triassic is probably less than previously believed. These non-pelagic deposits may represent the closure stage of the Paleotethys.

增长联盟视角下的中心城区存量国有资产更新——以上海市长宁区为例

我国城市更新具有增长联盟的结构性特征,而存量国有资产更新中的增长联盟兼具典型性和独特性。上海长宁以愚园路和武夷路作为实践区域,为存量国有资产更新提供了不同模式的样本。愚园路案例中,以商铺型区属国有资产为主要载体,地方政府与民营企业形成了相互塑造的政企合作模式,合作关系一定程度上具有非正式特征;武夷路案例中,园区型国有资产在复杂权属关系下产生了各异的使用权获得路径,经历了曲折的联盟组建过程,促成了多层次多面向的政企联合体,在政府更强的统筹力度下体现出多元价值特征。在增长联盟的理论框架和上海长宁的实践基础上,从内部关系、构建过程和多重价值3个补充视角提出中心城区存量国有资产更新需关注的挑战和路径建议。

川南长宁地区奥陶系五峰组—志留系龙马溪组页岩气储层低电阻率响应特征及主控因素

以川南长宁地区NX22井五峰组—龙马溪组低电阻率页岩气储层为例,利用岩心矿物组分、扫描电镜、总有机碳(TOC)含量、含水饱和度测试及测井曲线等资料,确立了低电阻率页岩气储层岩石体积物理模型,采用随机法构建了三维数字岩心模型,进而利用有限元数值模拟方法模拟计算各矿物组分含量、含水饱和度及有机质石墨化的电阻率响应特征,并分析其主控因素。研究结果表明:(1)长宁地区五峰组—龙马溪组低电阻率页岩气储层岩石体积物理模型由骨架(石英、长石、方解石和白云石等)、黏土矿物、黄铁矿、未石墨化有机质以及石墨化有机质、孔隙6个部分组成。(2)三维数字岩心模型的长、宽、高分别为100×100×100像素,融入了上述物理模型中的6个部分,并采用不同的颜色对导电组分进行标识,可以显示不同方向上的切片,表征低电阻率页岩气储层的组分特性。(3)黏土矿物含量、黄铁矿含量、含水饱和度以及有机质石墨化程度等4个参数增大都会造成页岩气储层的电阻率下降,而有机质的高石墨化程度(25%)和高含水饱和度(88.0%)使页岩气储层的电阻率从正常电阻率(大于15Ω·m)降到低阻甚至超低阻(小于5Ω·m),是导致研究区页岩气储层超低阻响应的2个核心因素。

基于叠前岩石力学参数反演的三维地应力预测研究——以长宁区块页岩气为例

与常规油气藏相比,页岩气藏的物性条件极差,孔渗性超低,其实现大规模开采的关键在于水平井体积压裂改造技术的应用。近年来,大量页岩气开发实践证明,水平井压裂效果受地应力作用较为明显。研究表明:当水平井沿着最大水平主应力近垂直的方向钻进,且应力差异系数较小时,有利于形成网状压裂缝。笔者选择长宁页岩气区块,对基于地震方法的三维地应力预测技术在水平井开发中的应用进行研究。利用一系列地震方法,诸如地震构造解释得到的构造信息(地震解释层位与断层)、叠前统计学反演得到的地层信息(速度与密度)、地质力学信息(杨氏模量与泊松比),优选适当的模型方法,并刻度模型参数(比奥特系数、构造应力系数a和b、局部应变系数A和B等),对三维最大和最小水平主应力大小、应力差异系数及地应力方向进行预测;研究了长宁区块页岩气的区域应力机制以及对3口水平井的微地震监测结果进行分析,验证了本文三维地应力预测结果的可靠性。在水平井设计时应综合考虑地应力方向、非均质性和应力差异系数,以获得良好的压裂效果。