Abstract:With the maturation of oil and gas exploration and development in Songliao basin, it is urgent to expand strategic replacement areas for oil and gas storage and production. In this task, deep oil and gas seem to be an important direction. Roof gas logging with continuous sampling in the whole well section of Well SK-2 obtained 6042 groups of light hydrocarbon composition data containing 103 monomers, and fully demonstrated vertical variation characteristics of light hydrocarbon components in the deep part of Well SK-2, which shows obvious segmentation. As a whole, it can be divided into 6 sections:section I (470-1000 m in well section), which has a small peak area, a small number of peak outfalls, and a low heavy hydrocarbon content, showing the characteristics of shallow and low-mature oil and gas; Section II (well section 1000-2800 m) has a large peak area, a large number of peaks and a high heavy hydrocarbon content. It is a mature type I source rock and a conventional oil and gas section dominated by oil generation; Section III (2800-3320 m in well section) has fewer and scattered peaks, low content of heavy hydrocarbon and no hydrocarbon source rocks, which are characteristic of reservoirs; Section IV (3320-5940 m in well section) is the upper unconventional gas section of Shahezi Formation, with a large peak area and a large number of peak outputs, high content of heavy hydrocarbon, being Type III source rocks with large thickness in the maturation-over-maturation stage, and sandstone interbeds can form various types of unconventional natural gas, suggesting an important section for future exploration; Section V (5940-6200 m in well section) is the lower part of Shahezi Formation and Huoshiling Formation, and the peak area and peak number of roof gas are scattered within the section which is considered to be in the stage of over-maturation; Section VI (6200-7108 m in well section) is volcanic rock and basement segment, and the peak area and number of peaks are generally low. However, the peak area of top gas in 7000-7100 m well segment shows that the light hydrocarbon parameters are different from those of section V, and it is inferred that there may be gas sources of type II-III organic matter in the deep part. These characteristics show that the vertical distribution of light hydrocarbon components reflects the different characteristics among Jurassic, Cretaceous and the basal formations in oil and gas formation, maturation, gas content and oil and gas sources. The results obtained by the authors reveal the potential of deep unconventional gas resource, and provide an important foundation for Songliao Basin's exploration shift from conventional oil and gas exploration and tight conglomerate gas exploration at the edge of fault depression to deep trough zone for the exploration and expansion of unconventional natural gas.

Abstract:Based on the new results of 1:50,000 geological survey of Banfanggou and Xiaoliugou sheets in Hami area, Xinjiang, this paper systematically reviewed the major tectonic events and evolutionary history during Paleozoic in the northern part of the East Tianshan Mountains. There existed three major tectonic events between Ordovician and Early Silurian, between Devonian and Early Carboniferous and in the Late Carboniferous, respectively, as shown by the newly discovered angular unconformity or disconformity. Combined with a series of new records of sedimentation, magmatism and deformation reflecting tectonic transformation, the links between these tectonic events and the evolution of the Central Asian Orogenic Belt (CAOB) are discussed. It is suggested that the orogenic event that occurred at the turning time from Ordovician to Silurian was the response to collision between the Junggar-Tuha terrane and the Altay terrane following the closure of the Armantai oceanic basin. The disconformity between Devonian and Lower Carboniferous shows an epeirogenic event, probably in response to the initial closure of the Kalamaili oceanic basin to the north. This disconformity and underlying Silurian-Devonian deposits in relatively stable tectonic environment also show that the Junggar-Tuha terrane between the Kalamaili oceanic basin and the North Tianshan oceanic basin was a relatively rigid and stable continental block in the Paleo-Asian Ocean system. The study area, as the northern passive continental margin of the Junggar-Tuha block, was less affected by the convergence of the Kalamaili oceanic basin. The orogenic event in the late Carboniferous was the reflection of peak orogenesis in response to the evolution of the peripheral foreland basin after the arccontinental collision that occurred along the Kalamaili suture zone during late Devonian-early Carboniferous period. This event established the basic NW-SE trending structural framework in the East Tianshan Mountains. The authors also redefined the Moqinwula fault as the southeastern extension of the Kalamaili suture zone, the tectonic-stratigraphic boundary between the North Tianshan Mountains (or Junggar-Tuha block) and the East Junggar terranes, and discussed the spatial differences of tectonic regime in the early Carboniferous. Based on the records of sedimentation and magma of the early Carboniferous, the authors hold that a peripheral foreland basin, which was related to the closure of the Kalamaili oceanic basin, was developed in the Moqinwula Mountain, whereas a rift basin was developed in the Bogda-Harrick Mountain, which was in response to the post-collision extension related to the closure of the North Tianshan Ocean.

Abstract:Detailed studies of the texture and composition of ophiolite mélanges belt can provide important information for the reconstruction of ancient plate tectonics and the evolution of ancient ocean basins. The Beishan orogenic belt contains multiple belts of ophiolite mélanges and records Paleozoic subduction and closure processes of the Paleo-Asian Oceans. However, the tectonic evolution of the North Beishan orogenic belt (NBOB) is still hotly debated. Hongshishan-Baiheshan ophiolite mélanges belt which consists of ophiolite and accretionary complex is located in the north of the Beishan orogenic belt. The ophiolite mélanges show that typical block-in-matrix fabric is characterized by intense deformation recorded by tight fold, rootless intrafolial folds, penetrative foliations and duplex thrust faults. The mélange is composed of various exotic or native blocks, including ultramafic rock (metamorphic peridotite, pyroxene peridotite, peel pyroxenite and serpentinite), gabbro (344Ma), basalt, plagiogranite (297Ma), chert, limestone and Ordovician volcanic rocks. The matrix consists of serpentinite, sandstone and a small quantity of epidotechlorite schist. The sedimentary blocks composed of limestone and turbidite suggest a characteristic of slump deposit. The ophiolite mélanges belt developed three distinct foliations which showed middle and deep tectonic stratigraphy in the first two phase and nonpenetrative foliation in the third phase. Spatially, the Baiheshan ophiolite mélanges belt composed of ophiolite and accretionary complex was thrust over turbidite of Lvtiaoshan Formation and shared similar compositions, deformations, spatial and temporal distributions to that in Hongshishan area. The Mingshui magmatic arc consisting of quartz diorite-granodiorite-monzonitic granite and Baishan Formation arc volcanic rocks is located in the north of the Baiheshan ophiolite mélanges belt. Baiheshan ophiolite mélanges belt and the Mingshui magmatic arc constitute a Carboniferous-Permian trench-arc system within the North Beishan orogenic belt (NBOB) during the Carboniferous-Permian southward subduction of the Hongshishan-Baiheshan Ocean.

Abstract:The Qilian Orogenic Belt (QLOB), located on the northern margin of the Tethyan tectonic domain, suffered from the development and evolution of the Early Paleozoic Proto-Tethyan Ocean (i.e., the North Qilian Ocean, NQO), and was the key orogenic belt for the uplift and expansion of the Tibetan Plateau on its northeastern margin. Based on regional geological survey and structure geological mapping and combined with previous geophysical data and newly completed super-broadband magnetotelluric (MT) sounding, this paper expounds the characteristics of the fault system in Northwest China and the QLOB. Through superbroadband MT data acquisition, processing, and inversion, and structural interpretation of shallow, medium and deep electrical structures along the MT profile across the QLOB, the distribution of Mesozoic and Cenozoic basins related to the fault system, and the deep crustal structure underneath the QLOB are analyzed. The deep electrical structure of the QLOB reveals a fossil bidirectional subduction of the NQO plate in the Proto-Tethyan tectonic domain. According to deep electrical structure, the original width of the subducted North Qilian Ocean plate was over 600 km. The southward subducted NQO plate probably reached the north margin of the Qaidam Block (the present Qaidam Basin) in the south, with a gentle subduction angle underneath the Central and South Qilian Block. Then, the melting-broken plate (or slab) might have migrated downward to the depth. In the north, the subducted NQO plate probably reached the southern margin of the Yin'e Basin of the present position, with a steep subduction angle. The dumpling melting-broken NQO plate was separated from the crustal retention plate in the north, through the northward extrusion of the upper mantle. The authors hold that the folding deformation of the subducted ocean plate was probably caused by the compressional tectonics in the Mesozoic and the Cenozoic, especially during the Late Cimmerian orogeny of Early Cretaceous and the India-Asian continental collision in Neogene. The shallow part of the electrical structure proves that the Yumushan thrustnappe structure was developed northward to the North Qilian Fault, with the Yumushan as a klippe in the north. The concealed Early Cretaceous basin underneath the klippe should be a good area for oil and gas prospecting. According to the normal faulting developed in the Early Cretaceous, the authors constrain the main stage thrusting of the North Qilian Fault in the Early Cretaceous, which might provide the evidence for the uplift and expansion of the northern margin of the Tibetan Plateau in the Early Cretaceous. Based on combined data from previous researches and this study, the authors put forward a conceptual tectonic evolution model for the Qilian Orogenic Belt.

Abstract:The formation and evolution of the orogenic belt and the peripheral basin were controlled by some genetic tectonic events. The "basin" and "range" are coupled to some extent both in structure and sedimentation. Sedimentary structures can always respond to related orogenic events, such as growth strata and convolute bedding. Growth strata are sedimentary records of the tectonic events, and the analysis of their deposit age can effectively constrain the timing of the tectonic events. The Central China Orogen is distributed in the east-west direction. The north side of the central segment is the Ordos block, and the south side is the Yangtze block. The Central China Orogen mainly resulted from the closure of the Pro-Paleo Tethys Ocean, the extinction of ProTethys Ocean happened in the Paleozoic and the Paleo-Tethys Ocean was closed in the Mesozoic. Notably, the latter modified the orogen resulting from the former and responded to the global Indosinian movement. The Indosinian movement not only facilitated the final assembly of supercontinent Pangea, but also was of great significance in the formation of the rudimentary sketch of China's mainland today. In the process of the Indosinian movement, the South China block and the North China block were collaged, and the Indosinian movement was initiated. The Ordos Basin and the Sichuan Basin recorded the orogenic events well in sedimentary strata. In this paper, the authors identified growth strata in the Upper Triassic on the south margin of the Ordos Basin. The starting time of the Indosinian movement in the Ordos Basin is about 233 Ma. A sets of growth strata were identified in the Upper Triassic on the north margin of the Sichuan Basin and the start time was about 216 Ma.

Abstract:Since early Cenozoic, the collision and ongoing continuous convergence of the Indian and Eurasian plates have resulted in the high elevation and thick crust of the Tibetan Plateau. Yumushan thrust belt is located at the north front of the Qilian Mountain, and is the newest joined part of the Tibetan Plateau. Its geometry and kinematics of the crustal deformation recorded the complex relationship between the tectonics, erosion and climate change of the newest evolution of the earth. The deep structure and uplift mechanism have been controversial for a long time. In this paper, the authors unraveled the crustal structure of the Yumushan thrust belt by the newest acquired deep seismic reflection profile. The Moho depth beneath the Yumushan belt is 45-48 km with a shallower trend to the north; the deep reflection structure and subsurface tomography velocity structure show the apparent transparent zone and high velocity zone beneath the Yumushan, which may represent the intrusion of a large amount of granitoids beneath the Yumushan related to the closure of the Qilian Ocean in early Paleozoic, and the uplift was driven by two back-back thrust faults. Combined with other geological and geophysical data, the authors propose a new growth pattern in the northmost Tibetan Plateau, which may shed some light on the northward growth as well as the basin-range coupling relation.

Abstract:During implementation of the Deep Continental Scientific Drilling Engineering Project Well SK-2 in Songliao Basin, the most integrated core data of Shahezi Formation was obtained. And 43 abnormal strata of deep shale gas were preliminarily identified, with a cumulative thickness of 102 meters, indicating that Shahezi Formation has good deep energy prospect. For further analysis of oil and gas resources potential of Shahezi Formation in Songliao basin, in this paper, on the basis of previous studies and in combination with well logging, core data of Well SK-2 and the newly acquired 2-d seismic data in the north-south direction crossing Well SK-2, the spatial distribution and sequence characteristics of Shahezi formation in the vicinity of Well SK-2 well were analyzed. At the same time, based on gas abnormal data acquired form logging during drilling, the authors studied logging and seismic responses of oil and gas perspective reservoirs in Shahezi Formation. It is shown that the Shahezi Formation adjacent to Well SK-2 has large thickness but small lateral extension, and hence the authors divided it into 4 stratigraphic sequences based on well logging as well as seismic and core data, i.e., SQ1, SQ2, SQ3 and SQ4. Among the 4 stratigraphic sequences, SQ4 has a better energy prospect. Its lithology is dominated by mudstone and has the characteristics of high porosity and low wave impedance on logging curves, with continuous strong amplitude on seismic section. Impedance inversion section shows the characteristics of large wave impedance alternated with many smaller wave impedances. Thus, the occurrence conditions of deep natural gas resources of Shahezi Formation in this area are revealed.

Abstract:The West Junggar area of the western Central Asian Orogenic Belt is one of the most typical regions related to transition from the ocean to the continent in the late Paleozoic. It is still controversial about the specific time of ocean-continent transition and the continental growth of the West Junggar area at present. This paper reports zircon U-Pb age and zircon Lu-Hf isotope analytical results from the Miaoergou batholith and the newly discovered columnar jointed rhyolites on the northwest side of the Miaoergou batholith, West Junggar area. The zircon U-Pb ages indicate that the Miaoergou granitoids were formed at 302.8~308.8 Ma and the columnar jointed rhyolites were formed at 303.6~294.5 Ma, which indicates that the specific time of ocean-mainland transformation of the West Junggar area is limited to the Late Carboniferous-Early Permian. The zircon Lu-Hf isotope analytical results show that the Miaoergou granitoids and rhyolites have some similar characteristics in ¹⁷⁶Hf/¹⁷⁷Hf ratios and ε_Hf(t) values. High ¹⁷⁶Hf/¹⁷⁷Hf ratios and ε_Hf(t) values, similar to features of depleted mantle in nature, suggest that they resulted from partial melting of juvenile crust. Integrating regional geological data and previous research, the authors have reached the conclusion that the basement of West Junggar area was composed of juvenile oceanic crust and island arc which grew from late Neoproterozoic to late Paleozoic, with no old crystalline basement.

Abstract:Pingshanhu basin, located in the north of Hexi Corridor, is bounded by the Longshou Mountain in the south, the Beida Mountain in the north, and Heli Mountain in the west. The deposition and evolution of Pingshanhu basin were controlled by overthrust fault in the Early Cretaceous. In this paper, the authors deepened the study of the Early Cretaceous Miaogou Group, mainly about the geometry of the basin, the tectonic stress field and detrital zircon. The authors made a detail discussion on the tectonic evolution of Pingshanhu Basin. In Pingshanhu Basin, Miaogou Group exhibits an upward-fining sedimentary sequence. The tectonic deformation is dominated by NE-SW trending compression and E-W trending extension. The latest zircon age is (129.3±1.8) Ma, which may represent the earlieset time of the upper rock formation and the formation age of graben. On the basis of the sedimentary facies of Early Cretaceous Miaogou Group, the tectonic style, tectonic stress field and zircon ages of clastic rocks, the authors hold that Pingshanhu Basin was a compressional basin in the early Early Cretaceous. The growth strata restricted the compressional structure ages. It was an extensional rifted basin in late Early Cretaceous. The conversion time was posterior to 129.3 Ma.

Abstract:The tectonic affinity of the Alxa block has long been in debate. It may be part of the North China Craton (NCC), or independent from the NCC during the Precambrian. The comparison of basements between the Alxa block and the NCC would be helpful to solving this dispute, but the Alxa basement is relatively poorly studied due to limited outcrops, with most of available data reported in eastern Alxa. Recently, a syenite that intruded into the Longshoushan Group has been sampled in Helishan area, western Alxa, and both of them are unconformably covered by Sinian strata. The Helishan syenite is characterized by extremely enriched K₂O (13.77%) and LREE[(La/Yb)_N=46.62], and shows distinct negative and positive anomalies of Nb-Ta and Pb-Zr-Hf, respectively, with EM-I type Sr-Nd isotope features (ε_Nd(t)=-5.05), implying partial melting of basaltic lower crust. Moreover, LA-ICP-MS zircon U-Pb data indicate that this syenite was formed during Paleoproterozoic (1872 ±12) Ma and display records of~2.7 Ga crustal growth and~2.5, 2.1 and 1.95 Ga magmatic activities. According to data from this study and previously published data, the Neoarchean-Pelaoproterozoic basements and tectono-thermal events of the Alxa block and the NCC are geochronologically consistent, indicating very close affinity between them.

Abstract:This paper reports zircon U-Pb data of major and trace elements for the granodiorites from the Aweng Co area in northern Lhasa block. Zircon LA-ICP-MS U-Pb dating of granodiorite yielded an age of 163.3 ±1.7 Ma, suggesting that the intruded rocks were formed in late Early Cretaceous period. Geochemical studies show that Aweng Co granodiorites have typical geochemical characteristics similar to the magnesian andesite/diorite (MA). They are characterized by high Mg^# values (45.42~54.29) and low TFeO^*/MgO ratios (1.58~2.26). They are enriched in LREE in the chondrite-normalized REE patterns, and are enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs). Geochemical features of the Aweng Co magnesian granodiorites are considered to have been generated by the southward subduction of Bangong Co-Nujiang River oceanic lithosphere, and can be genetically regarded as resulting from partial melting of dewatered and subducted oceanic crust melts, which had been metasomatized by mantle peridotite under the condition of oceanic crust subduction. These results provide direct petrologic evidence of the intruded rocks for the southward subduction of the Bangong Co-Nujiang River Ocean.

Abstract:Based on the characteristics of the seismic phase on the section including the horizon reflection characteristics and the inphase axis characteristics and combined with the geological evolution process analysis, the authors established the seismic identification characteristics of the Carboniferous-Permian strata in the northern Songliao Basin. The Carboniferous-Permian strata were identified on six deep reflection seismic profiles of Song I-Song VI based on seismic phase characteristics. The main phase characteristics are medium-strong reflection energy, existence of local high values and the continuous overall in-phase axis changing from south to north and from west to east. The time-depth conversion relationship of the study area was obtained by collecting the exploration data of the existing Carboniferous-Permian strata and the seismic wave propagation velocity. Based on the reflection time distribution of the Carboniferous-Permian phase tracing correlation in the study area, the authors calculated the travel time difference between the top and bottom interfaces of the Carboniferous-Permian strata on the deep reflection seismic time profile, and gave the thickness and distribution of the Carboniferous-Permian strata in the study area by time-depth conversion. The distribution of the whole area is not extremely uniform. There are mainly two areas with high thickness, namely, the eastern part of the central uplift zone and the western part of the fault depression zone. The whole strata can be divided into upper, middle and lower layers from shallow part to deep part, and the seismic phase characteristics are different from each other. The distribution of Carboniferous-Permian strata in the northern Songliao Basin provides a valuable basis for deep oil and gas exploration under the main oil layers in Northeast China.

Abstract:Songliao Basin is a Meso-Cenozoic continental sedimentary basin in Northeast China. Based on a detailed analysis of the Paleozoic stratigraphic characteristics, sedimentary environment and tectonic evolution in Northeast China, the authors conducted the interpretation of the comprehensive geophysical data across Well SK-2 to investigate the properties and geophysical characteristics of the basement in this paper. On the SN profile, the authors have found some phenomena:the Bouguer gravity anomaly in Well SK-2 is high in the middle and low on both sides; the magnetic anomaly shows a negative correlation with gravity anomaly; magnetotelluric properties are characterized by partial layers and high-low resistance crossover in the shallow part and partial regions in the deep part. On the EW profile, the gravity anomaly curve has the trend high in the west and low in the east; the magnetic anomaly curve is "bowl-shaped"; there exists a high resistance structure compared with features of the SN-trending profile. Combining geophysical characteristics with lithofacies palaeogeography, the authors have reached the following conclusions:1. From the Late Carboniferous to Late Permian in the Upper Paleozoic, there were many sedimentary environments such as shallow marine facies, continental facies, rivers and lakes. The corresponding lithologic combinations had different physical characteristics; 2. The geomagnetic characteristics of the gravity, magnetic method and magnetotelluric sounding's results reveal that the basement of the study area is mainly composed of mudstone, marble and intrusive rocks, and the burial depth of the roof of the basement is about 7 km. The base of the study area is formed by the Upper Paleozoic and intrusive rocks. 3. The location and orientation of the Binzhou fault zone, the Sunwu-Shuangliao fault zone, the Helen-Renmin fault zone and the deep fault system are identified. The fault structures are mainly dominated by SN and EW trending structures. They are important components of the Paleozoic structural skeleton and control the migration and storage of deep oil and gas.

Abstract:When the seismic wave propagates in the underground media, the seismic wave energy will show a certain degree of attenuation. The quality factor Q is an important parameter for measuring the absorption and attenuation properties of the underground rock, and is of great significance for describing the lithological characteristics and predicting the oil and gas distribution. In this paper, the Q value analysis technique based on S transformation ratio method for deep seismic reflection data was developed, and the more accurate Q value was obtained. Taking the Shahezi Formation in the Songliao Basin as the main target layer, the authors calculated the Q value of the post-stack deep seismic reflection profile across Well SK-2, and then generated the Q value profile to summarize Q value distribution characteristics of the Shahezi Formation. The Q value distribution characteristics, combined with the logging, stratification and gas anomaly data of Well SK-2, suggest that the Shahezi Formation is a gas reservoir, and this discovery provides a way for the next deep reservoir prediction. This conclusion provides an idea for the further deep reservoir prediction and can serve the deep geological survey project in Northeast China.

Abstract:The deep seismic reflection profiling is a pioneering technique for detecting the deep structure of the crust. It can obtain the reflection fabrics of the Moho and the upper mantle, and hence is an effective method for revealing the lithosphere structure. The Huahai Basin is located in the western part of the Hexi Corridor basin, which is the intersection area of different tectonic units. The stratigraphic development is relatively complete, but the degrees of excavation and development are quite different. Except for the large area continuous distribution of the Cretaceous strata, the strata of other epochs are incompletely exposed, and are often manifested as residual debris damaged by division of intrusive rocks. In order to determine the suitable acquisition parameters for deep seismic reflection in the Huahai Basin, the authors conducted a pilot experiment before the collection, in which the small, medium and large TNT explosives were fired, and wells with different depths were drilled to make comparison. The parameter comparison was preferred, and finally the optimized acquisition parameters were obtained. In the small TNT explosives experiment, the reflection information obtained by the 36 kg dose is not as rich as the information obtained by 48 kg and 60 kg dose, and the results of 48 kg and 60 kg doses are clearer in the clarity of the MOHO reflection, with the single well excitation better than the combined well excitation. In the experiment of medium and large TNT explosives, the contrast of different combination wells does not show much difference. As the dose increases, the excitation energy increases, and the interference wave energy such as surface wave and refracted wave also increases. The interference wave energy of the small TNT explosives is the weakest, but has the most abundant reflection information. The interference waves of he medium and large TNT explosives are more developed, but the middle-shallow reflection information can also be obtained through the noise-suppressed processing.

Abstract:The Continental Scientific Drilling Project in the Songliao Basin was aimed at solving a series of scientific problems involved in Cretaceous paleoclimate and paleoenvironmental research, the development of deep exploration techniques, and the earth's deep resource survey. As the main borehole of the scientific drilling project of Songliao Basin, SK-2 has collected continuous and in-situ geophysical log data. In this paper, geophysical log data were used to reveal the range of petrophysical parameters of rocks in Huoshiling Formation. Combined with laboratory core NMR test analysis, the authors studied the pore structure characteristics of different igneous reservoirs. The results show that the Huoshiling Formation mainly consists of andesite, tuff, complex conglomerate and tuff mudstone. The igneous facies are dominated by the explosive facies and the effusion facies. The andesite and complex conglomerate are characterized by high resistivity and low acoustic wave time difference. The characteristics of the tuff are low resistivity and high acoustic time difference, and the tuff mudstone has the lowest resistivity. The reservoir has the characteristics of low porosity and low permeability, but the tuff reservoir has developed small and medium pores and has relatively good physical properties, and hence it is a favorable reservoir. The research results provide strong support for further evaluation of deep oil and gas resources and stratigraphic structure in the Songliao Basin.

Abstract:In order to conduct long-term deep observation, fluid experiments and investigate volcanic events in Songliao basin, the authors carried out lithological evaluation of volcanic rocks in Yingcheng Formation by using abundant and complete geophysical logs from SK-2 east borehole. The log response analysis of volcanic rocks shows that the radioactivity and electric conductivity of tuffs are the strongest. Agglomeratic lavas have low density because of high porosity. The density of rhyolites is the highest and the electric conductivity is the weakest. Volcanic rocks of Yingcheng Formation along SK-2 east borehole consist of rhyolites, transitional tuffl lavas, agglomeratic lavas and a little tuffs by using cross plots and imaging models. A volcanic eruptive gap may exist, as evidenced by tuff with high GR, low RD and low DEN. Rhyolites are characterized by high alkali, high Si, low Fe and low clay mineral. T₂ analysis suggests that the rhyolites are favorable for carrying out long-term observations and fluid experiments. The results provide a reference of interpretation for subsequent volcanic rock in Huoshilin Formation and research of volcanic rocks in the whole basin.

Abstract:The completion depth of Well Songke 2 is 7108.88 m. At the time 38h after the well completion, the bottom hole temperature was 241℃. Three kinds of drilling fluids were investigated in laboratory according to the formation and temperature conditions, and they respectively are the potassium chloride-polysulfonate system which is resistant to temperature of 180℃, the polymer drilling fluid which is resistant to 230℃ and formate-polymer drilling fluid which is resistant to 250℃. The experimental data show that these drilling fluids have good high temperature stability and low HTHP filtration loss. Through detecting the quality of drilling fluid real time, the predicted problems could happen through over-temperature detection, which make indoor experiments to guide in-site maintenance in the project construction, ensure the stability performance at high temperature interval, and guarantee the coring operation smoothly. In addition, the drilling fluid of each system achieves a safe and smooth transition during the conversion, without any waste slurry, which greatly saves the cost. The logging and casing running before cementing could be successfully completed at one time, which further proves that the drilling fluid used has good high temperature stability.

Abstract:Well Songke-2 is the deepest continental scientific drilling carried out by Asian countries. The logging temperature of Well Songke-2 Songke-2 was 241℃ after drilling for 38 hours, which created the highest well temperature application record of drilling engineering in China. The parameters of Well Songke-2 are mainly tested in two ways:one is integrated logging before casing, whereas the other is downhole parameter measurement while drilling which does not affect normal drilling work. Timely grasping the information such as the temperature while drilling plays a key supporting role in the adjustment of high temperature mud performance and the application of power tools. The authors carried out a series of researches on the problem of high temperature in Well Songke-2, and developed a storage type measurement while drilling instrument. The instrument was improved and designed through multiple rounds of research and finally it has been successfully applied to Well Songke-2.

Abstract:Deep-well combined drill string technology has become one of the most important scheme to solve the super-long drill string used for ultra-deep drilling project, which is related to equipment capacity, material property, drilling conditions and string mechanics. In this paper, the application and development of combined drill string technology in geological drilling are summarized systematically, the design scheme and its limitation length are discussed in detail on the basis of strength theory. The results show that the drilling mission with the depth of 13000m could not be finished by simply using pure steel combined drill string with the final borehole diameter being 216mm. By using drill string consisting of V150 steel drill pipe & titanium alloy drill pipe and S135 steel drill pipe & aluminum alloy drill pipe, the limitation depth and the weight of each combined drill string are respectively 13484m, 18783m and 360.5, 324.3t; in this way both of them own application reliability and advantage. These results have reference significance to the design and selection of deep-well combined drill string used for ultra-deep drilling project.

Abstract:The western Junggar region, which is sandwiched between the nearly EW-trending Irtys fault and the Tianshan strikeslip fault system, has experienced long and complicated history of intracontinental tectonic deformation since the Late Paleozoic. The length, direction and spatial distribution of tectonic lineaments can not only reflect the strength and style of structural deformation but also indicate the mode of stress action. In this paper, the western Junggar region in northwest Xinjiang was selected as the research area. The spatial distribution and spectral information of fault structures in multi-source data such as ASTER and Landsat were displayed by color composite,principal component analysis(PCA), band ratio and Sobel filtering. The linear structures in the study area were extracted by combining Canny edge detection and visual interpretation. The principle and method of geostatistics were used to quantitatively analyze the extracted linear structures. The results show that the strike of the main faults determined by the optimum orientation of length in the study area is N50°-60°E, which represents the orientation of the distribution of the regional first-order structure, namely the Dalabut fault. The strike of the secondary faults determined by the optimum orientation of the number of linear structures is 80°-90° (in nearly EW direction), which represents the orientation of the regional third-order structures. The linear structures between the above two structures, namely moderate structures in number and length, represent the orientation of the regional secondary structure. The regional distribution of linear structures reveals the structural system composition and deformation characteristics of the western Junggar region under the action of the principal compressive stress in the NS direction. Therefore, the quantitative analysis of linear structures extracted from multi-source remote sensing image is of great significance for the determination of regional fault tectonic system.

Abstract:Widespread use of geothermal resources helps reduce the use of fossil fuels and the management of haze. There are rich geothermal resources on the northern foot of the Qinling Mountain, but the research work is slow and unevenly distributed. This paper outlines the natural geography of the northern foot of the Qinling Mountain, discusses the characteristics of regional geothermal carriers and structural units, describes the distribution at the depth of near-surface (20 m) and deep place (1500 m) as well as geothermal gradients and Geothermal flow value. According to the different characteristics, the geothermal fluid on the northern foot of the Qinling Mountain is divided into four sections, with a discussion given to the characteristics of each section. The authors analyzed geothermal resources on the northern foot of the Qinling Mountain:the main source of energy is the conduction of heat inside the earth, supplementary energy is thermal energy generated by the decay of radioactive elements in rocks in deep formations, and thermal energy is generated during the conversion of montmorillonite to illite and biodegradation of organic matter heat energy. The formation patterns of geothermal resources on the northern foot of the Qinling Mountain are divided into heat conduction type and thermal convection type:Heat conduction geothermal resources are widely distributed, and thermal convection geothermal resources are mainly distributed in areas where deep faults are directly connected with the surface and in the vicinity of the fault zone. The authors calculated the total heat stored in the geothermal unit using the volumetric method and the amount of geothermal resources that are difficult to be used at 4000 m as well as the amount of geothermal resources that can be utilized at 4000 m. The authors calculated the geothermal fluid resources of Wenshuigou in Baoji, Tangyu in Meixian, Tangyu in Lantian, Huaqing Pool and Dongda in Xi'an by using heat flow method. According to the law of geothermal resource occurrence in the study area, the authors divided the whole region into encouraged mining area of geothermal resources and maintained mining area, and pointed out the direction of geothermal resources utilization. The purpose of this paper is to promote the clean energy industry on the northern foot of Qinling Mountains in a timely manner and provide a theoretical basis for the scientific and long-term development of geothermal resources.

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