PreviousNext No AccessInternational Geophysical Conference, Qingdao, China, 17-20 April 2017New understanding and effective seismic approaches on carbonate heterogeneityAuthors: Fangjian Xue*Jun TianHaijun YangChunshu LuoGengxin PengXue LeiChuan WuPin YangFangjian Xue*Schlumberger, Kuala LumpurSearch for more papers by this author, Jun TianPetroChina, KorlaSearch for more papers by this author, Haijun YangPetroChina, KorlaSearch for more papers by this author, Chunshu LuoPetroChina, KorlaSearch for more papers by this author, Gengxin PengPetroChina, KorlaSearch for more papers by this author, Xue LeiSchlumberger, BeijingSearch for more papers by this author, Chuan WuSchlumberger, BeijingSearch for more papers by this author, and Pin YangSchlumberger, BeijingSearch for more papers by this authorhttps://doi.org/10.1190/IGC2017-167 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract The heterogeneity is the most aspect in carbonate exploration and production. Especially, the large cavities (caves and vugs) has significant impact on reservoir performance but been much under-evaluated in reservoir characterization due to limited knowledge and data. The exploration and production on cavernous reservoir in Tarim Basin of west China has led to a new and insight understanding of carbonate heterogeneity. The seismic images on large caves are typical “pair of beads” high amplitude anomalies. Such features are observed worldwide in carbonate reservoir. Our further study reveals that the large cavities are of primary origination and more extensive in carbonate than observed in E&P data. Targeted seismic processing and high density seismic acquisition in Tarim Basin have revealed many subtle cave features unrecognized in conventional approaches. These results demonstrate how extensive and extreme the heterogeneity could be in carbonate rock and how effective the proper seismic approaches could be to enhance exploration and production performance in carbonate play. There are still large room to improve the results, which will lead to more significant progress in carbonate theory and application. Keywords: effective, carbonate, heterogeneous, reservoir characterizationPermalink: https://doi.org/10.1190/IGC2017-167FiguresReferencesRelatedDetailsCited by“Pair beads” seismic anomalies: The cave features important to but missed in carbonate studiesFangjian Xue15 August 2022 International Geophysical Conference, Qingdao, China, 17-20 April 2017ISSN (online):2159-6832Copyright: 2017 Pages: 1525 publication data© 2017 Published in electronic format with permission by the Society of Exploration Geophysicists and Chinese Geophysical SocietyPublisher:Society of Exploration Geophysicists HistoryPublished Online: 31 May 2017 CITATION INFORMATION Fangjian Xue*, Jun Tian, Haijun Yang, Chunshu Luo, Gengxin Peng, Xue Lei, Chuan Wu, and Pin Yang, (2017), "New understanding and effective seismic approaches on carbonate heterogeneity," SEG Global Meeting Abstracts : 657-660. https://doi.org/10.1190/IGC2017-167 Plain-Language Summary Keywordseffectivecarbonateheterogeneousreservoir characterizationPDF DownloadLoading ...

The evolution of the Kuqa fold-thrust belt is accompanied with the Cenozoic uplifting of South Tianshan Mountain range. The critical Coubomb wedge theory can be well applied to the structural evolution of the Kuqa fold-thrust belt where the decollement structures are well developed. Following the initial hypotheses of this theory, with the base of the taper wedge (not the sea level) as the reference level, we propose a geometric relationship between the evolution of fold-thrust belt and tectonic uplifting of orogen, and deduce a calculation formula between orogen tectonic uplifting amount (very different from the topographic uplifting) (partial derivative H), fold-thrust belt extending distance (partial derivative S) and crustal shortening amount (partial derivative L): partial derivative H = (partial derivative S - partial derivative L) *tan(alpha + partial derivative alpha) + [tan(alpha + partial derivative alpha) / tan alpha-1] (*) H-0. In this paper we select two representative seismic profiles across the Kuqa fold-thrust belt to reconstruct the structural evolution, and use the calculation formula to get the uplifting amount of the South Tianshan Mountain range in Kuqa region during two geological periods. The results showed: during the end of Miocene to the end of Pliocene, the uplifting amount of the South Tianshan Mountain range in the middle segment of Kuqa (partial derivative H-M1) is 4.1 km; during the end of Pliocene to the present, the uplifting amount of the South Tianshan Mountain range in the middle segment of Kuqa (partial derivative H-M2) is 4.7 km, and in the east segment of Kuqa (partial derivative H-E) is 5.0 km. (c) 2017 Elsevier Ltd. All rights reserved.

Kuqa Late Cenozoic fold-thrust belt in the southern flank of Tianshan Mountains comprises of several structural zones trending E-W. Regional decollement faults are developed in the Triassic dark mudstone, Jurassic coal-bed Paleogene Kumugeliemu gypsum-salt and Neogene Jidike gypsum-salt. The bottom main decollement fault of the fold-thrust belt rises step by step southward. Cover decollement-thrust (thin skinned structure) developed in the major part of the belt, and basement-involved thrusts (thick skinned structure) can only be seen in the root zone at the north margin of the belt. The deformation above the Cenozoic gypsum-salt is characterized with decollement fold and that under the Cenozoic gypsum-salt is characterized with thrust. Kuqa fold-thrust belt was resulted after the Cenozoic (South) Tianshan Mountain building under the far-field effect of the India-Asia collision. The main force resource of the folding and thrusting is the compressive structural force induced by the southward propagation of the (South) Tianshan orogenic wedge. The folding and thrusting began since ca. 23Ma, and then accelerated at ca. 10Ma, 5 similar to 2Ma and 1 similar to 0Ma. The evolution of Kuqa fold-thrust belt is in the way of forward propagation. While the front of the belt propagates southward, the hinter parts continue folding and thrusting.

The Bachu Rise in the western Tarim Basin is the fore-bulge of the Kunlun late Cenozoic intra-continental foreland basin system formed under the far-field effect of India-Asia collision. Cenozoic faults and faulting are abnormally developed in the Bachu Rise and its adjacent area. Taking the Niaoshan-Gudongshan area on the southern boundary of the Bachu Rise as the key study area, 5 Cenozoic faulting phases were identified in the Bachu Rise and its adjacent area after careful seismic interpretation. They are end Cretaceous beginning similar to Paleogene (ca. 65 Ma) decollement-thrusting, end Paleogene similar to beginning Neogene (ca. 23 Ma) decollement-thrusting, end Miocene beginning similar to Pliocene (ca <1.5 Ma) basement involved thrusting, rate Pliocene early Pleistocene (ca. 3-2 Ma) normal faulting, middle Pleistocene Holocene (ca. <1.5 Ma) decollement-thrusting and strike-slip faulting. The Middle Cambrian and Paleogene gypsum-salt layers serve as the two main decollement layers in the study area. Thrusting of ca. 65 Ma was under the far-field effect of the collision between Lhasa (part of the Cimmerian Continent) and Asia; and the other 4 Cenozoic faulting phases were all under the far-field effect of the India-Asia collision. The late Cenozoic faulting is characterized by pulse thrust. There is one tectonic pause between each two successive thrust pulses. The compressive tectonic stress is weaker and even evolved into a slight tensional tectonic stress and forms normal fault in the tectonic pauses. (C) 2016 Elsevier Ltd. All rights reserved.

Late Silurian-Carboniferous extensional structures have been discovered after careful interpretation of seismic reflection data in western Manjiaer Sag, Central Tarim Basin in central Asia. The extensional structures comprise numerous small normal faults in nearly N-S strike direction. Groups of normal faults in profile show features suggestive of negative flower structures and small horst-graben structures. Based on growth index calculation, these extensional structures formed in the Late Silurian period, continued activity in the Devonian and Carboniferous and then ceased at the end of Carboniferous. The peak-stage of normal fault activity occurred in Late Silurian. Late Silurian-Carboniferous normal faults also developed in the Tazhong and Tabei areas, which implies that Tarim Basin were under regional extensional tectonic setting during that periods. The extensional structure in southern Tarim resulted from the post-orogeny stress relaxation of the Kunlun Early Paleozoic orogenic belt, and those in northern Tarim resulted from the Paleozoic back-arc rifting which led to the opening of South Tianshan ocean. (C) 2014 Elsevier Ltd. All rights reserved.

The Kuqa fold–thrust belt (KFTB), a late Cenozoic fold–thrust belt on the southern flank of the Tian Shan Mountains, consists of several deformation zones trending nearly W–E. The main décollement fault of the KFTB gradually rises southwards. There are three regional main décollement faults in the Triassic dark mudstone, Paleogene gypsum salt (Kumugeliemu Formation), and Neogene gypsum salt (Jidike Formation), respectively, and possibly a fourth in the Jurassic coalbed. Laterally, thin-skinned structures are developed in the main segments of the KFTB, whereas thick-skinned structures are in the root zone. Vertically, the structural deformation above the Cenozoic gypsum-salt layers (Paleogene gypsum salt in the middle segment of the KFTB and Neogene gypsum salt in the eastern segment) is characterized by décollement folding, whereas that below is characterized by thrusting. The KFTB was resulted from the late Cenozoic intra-continental orogeny in the Tian Shan area under the far-field effect of the India–Asia collision. The deformation of KFTB began (folding and thrusting) ca. 23 Ma, when the far-field effect of the India–Asia collision reached the Tian Shan area. The deformation of KFTB accelerated ca. 10, 5–2, and 1–0 Ma. In general, the evolution of the KFTB is forward propagating, and the hinter parts of the KFTB continue to deform, while its front propagates southwards.

The Madong fold-thrust belt, which strikes NE-SW and thrusts southeastward, locates in the southern Tarim Basin. It is a part of the Kunlun Early Paleozoic foreland fold-thrust belt, and so is the Tangnan fold-thrust belt on the southeast of Madong. The Madong and Tangnan fold-thrust belts developed in Cambrian-Ordovician strata, and the Middle Cambrian gypsum-salt layer serves as the main decollement surface. The Middle Silurian and above strata unconformably overlie Madong while the upper Lower Silurian unconformably overlie Tangnan. On the basis of the facts that: (1) the Upper Ordovician is the youngest strata involved in the fold-thrust deformation, (2) the upper-Lower to Middle Silurian is the oldest strata unconformably overlying the foreland fold-thrust belt (including Madong and Tangnan), and growth strata exist in the upper part of the Upper Ordovician, we infer that the deformation time of the Kunlun Early Paleozoic foreland fold-thrust belt (including Madong and Tangnan) was during the Late Ordovician-Early Silurian. Tangnan is the residual of the major part of the foreland fold-thrust belt. Its northwestward thrust direction represents the main thrust direction of the foreland fold-thrust belt. Madong is the front belt of the foreland fold-thrust belt. It mainly thrusts southeastward and serves as the back-thrust belt of the Kunlun Early Paleozoic foreland fold-thrust belt. It is a triangle zone between Madong and Tangnan. The Madong fold-thrust belt is the best-preserved section of the Kunlun Early Paleozoic collisional orogenic belt, and thus is an important geological record of the Kunlun Early Paleozoic orogeny. (c) 2015 Elsevier Ltd. All rights reserved.

Summary Holes and cave systems in ultra-deep Ordovician karsted limestone have been studied in their context of paleogeography and fault and fracture zones using the structurally sharpened visualization and analysis of seismic data in continuous color. The seismic structural attribute provides a method for direct extraction of karst holes as geobodies. The structurally sharpened red-green-blue (SRGB) color texturing of horizons and their correlation with stratigraphy reveals geologic features that help interpretation of seismic data for paleogeography. The merger of karst hole heterogeneity geobodies with the SRGB color-textured horizons confirms that karst erosion occurred primarily in weak rocks along fracture and fault zones. Finally, the evolution of the karst cave system and its relation to erosive early Silurian channels could be confirmed. The water from these channels entered the karsted limestone through sinkholes and eroded fracture zones. This observation indicates that the karstification occurred in several phases during the late Ordovician and early Silurian. The method highlights that it is important to integrate the interpretation of structural features in a stratigraphic and paleogeographic context to achieve a conclusive geological interpretation of seismic data using attributes.

The eastern Qiulitagh fold and thrust belt (EQFTB) is part of the active Kuqa fold and thrust belts of the northern Tarim Basin. Seismic reflection profiles have been integrated with surface geologic and drill data to examine the deformation and structure style of the EQFTB, particularly the deformational history of the Dina 2 gas field. Seismic interpretations suggest that Dongqiu 8 is overall a duplex structure developed beneath a passive roof thrust, which generated from a tipline in the Miocene Jidike Formation, and the sole thrust was initiated from the same Jidike Formation evaporite zone that extends westward beneath the Kuqatawu anticline. Dongqiu 5 is a pop-up structure at the western part of the EQFTB, also developed beneath the Jidike Formation evaporite. Very gentle basement dip and steep dipping topographic slope in the EQFTB suggest that the Jidike Formation salt provides effective decoupling. The strong deformation in the EQFTB appears to have developed further south, in an area where evaporite may be lacking. Since the Pliocene, the EQFTB has moved farther south over the evaporite and reached the Yaken area. Restoring a balanced cross-section suggests that the minimum shortening across the EQFTB is more than 7800 m. Assuming that this shortening occurred during the 5.3 Ma timespan, the shortening rate is approximately 1.47 mm/year.

The timing of hydrocarbon charging relative to trap formation is a key factor for evaluating the exploration potential of the Qiulitagh fold and thrust belt (QFTB) on the north flank of the Tarim basin. Data obtained by this study indicate that structural traps were filled by hydrocarbons in two episodes. In this area, at least four major deformation events have been identified for the period of Late Cretaceous to Pliocene. The first event occurred in Late Cretaceous and led to the formation of paleo-uplift structures. The second event was characterized by thrust features and occurred in latest Oligocene. The third and fourth events were represented by compressional structures that were developed in Late Miocene and Late Pliocene, respectively. Based on oil and gas-source rock correlations and 1-D basin modeling, two episodes of hydrocarbon generation and migration are proposed to be responsible for oil and gas accumulations in the QFTB. The two episodes of hydrocarbon charging from a source kitchen north of the study area took place in Early Miocene and Pliocene, respectively. Since the QFTB was uplifted in Late Oligocene and Late Miocene, the hydrocarbon generated during all two periods could migrate toward this area to form oil and gas accumulations in suitable structures.

Thick-skinned contractional salt structures are widely developed in the western Kuqa depression, northern Tarim basin. To understand the mechanisms that govern the development of these structures, physical experiments are conducted and the results show that they are largely governed by the activities of basement faults and the forming of paleo-uplifts and basement slopes. The model materials in this study are dry sand, vaseline and plasticene (or hard foam), simulating the suprasalt, salt, and subsalt layers respectively. The experiments show that, due to the activities of basement faults and the forming of the paleo-uplifts, salt bodies usually accumulate and thicken significantly on the middle top of the paleo-uplifts which are constrained by the pre-exiting boundary faults. The development of large-scale thrust faults and salt nappes is favored by the basement slops with larger dips. The experiments also conclude that differential structural deformation could occur between the subsalt and suprasalt layers because of the presence of salt layers. Their geometries and the locations of structural highs are different, despite of the great similarities in the uplifted areas. The pierced salt diapir is not observed in the experiments, which indicates that the contractional shortening does not effectively accelerate the development of the salt diapir.

Affected by the South Tianshan orogenesis, the faulted structure patterns in the Wushi Sag are very complex. Aimed to find out the basic characteristics of the structures, this article studies many seismic profile sections, the regional geology, the structural patterns, and the formative stage of the structures. The Wushi Sag has three main fault patterns (face to face thrust, back to back thrust, sphenoid thrust), and many local fault structural patterns (fault-bend fold, fault-propagation fold, duplex structure, outburst structure, growth structure, etc.). There mainly develop four groups of reverse faults (NE, NEE, NW, EW) and one group of NNW trending strike-slip faults. According to the structural background, seismic profiles, and balanced cross sections, the main fault in the studied area experiences at least five evolving stages, which are, pre-Mesozoic, late Permian – early Tertiary, Jurassic, late Jurassic – early Cretaceous, and late Neogene. The structural styles have a close relationship with source rocks, hydrocarbon reservoirs, and the character and distribution of petroleum systems.

Comprehensive data from field observations, drilling wells and seismic profiles have demonstrated that the Paleogene Kumugeliemu Fm. and Neogene Jidike Fm. attain thick halite layers in the Kuqa depression of the northern Tarim basin, NW China. Driven by the buoyancy, gravity spreading, differential loading and compressional stresses, the salt bodies experienced viscous flowage, resulting in spatial distribution features for the circum-Baicheng sag and thickening in the Kelasu and Qiulitage structural belts with the maximum thickness of 4000m. The viscous flow of salt sequences influenced the structural distortion of the halite layers and overburden. Consequently, many salt-related structures, such as salt pillows, salt walls, salt nappes, fish-tails, salt welds (fault welds), salt stacks, pop-ups and salt-withdrawal sags, have developed well in the Kuqa depression. The salt-related structures had exerted important influence on the hydrocarbon migration and accumulations. The structural and subtle traps induced by the salt structures offered abundant favorable space for hydrocarbon accumulation, the faults acted as the favorable pathways for hydrocarbon migration and the thick halite layers served as good regional seals for hydrocarbon preservation. The forming models of hydrocarbon accumulation are different in the sub-salt, salt and supra-salt in the Kuqa depression. The integrated analysis shows that the favorable exploration objectives include the sub-salt anticlinal traps, footwall fault traps sealed by reverse faults, stratigraphic-lithologic traps, mid-salt structural-stratigraphic traps and supra-salt anticlinal traps.

Based on well and seismic data, some paleo-uplifts and salt structures have been identified in the Kuqa depression. The Quele, Dabei-Tubei, Kelasu, Yiqikelike and Tugerming paleo-uplifts are located in the Kelasu-Yiqikelike and Qiulitage structural belt, as well as salt pillows, salt nappes and salt walls. The development of salt structures has very close relationships to the paleo-uplifts because the paleo-uplifts exerted important influences on the spatial distribution of salt thickness. Usually, salt bodies thickened on the middle top of basement paleo-uplifts and then formed salt pillows and salt walls, yet salt-weld and salt-fish structures commonly developed in the regions adjacent to the limbs of the paleo-uplifts where the salt thickness obviously declined, resulting from the viscous flowage of salt. In the Kuqa depression, the basement paleo-uplifts and salt structures have governed the hydrocarbon accumulations in that the paleo-uplifts can improve the reservoirs, can be the favorable areas for hydrocarbon migration and thick halite layers also afford very good seals for hydrocarbon preservation. In addition, the structural distortion of paleo-uplifts and salt structures formed many structural and subtle traps, and the faults and unconformities can form good hydrocarbon pathway systems.

According to interpretation of seismic data in the western Kuqa Depression, we analyze the style of salt-related tectonics. We analyze the formation stage of salt-related tectonics through balanced section. The formation stage can be divided into two stages: the stage before the end of E1-2 deposition, and the end of the Himalayan movement. We make two manual wellsand to model their source rock's maturity history by BasinMod 1-D of the PRA company. Through analyzing the matching of the formation stage of salt-related tectonic traps and the stage of hydrocarbon generation, we consider that there can be good hydrocarbon reservoirs in Kelasu tectonic belt since the formation stage of the paleotectonics traps match the stage of hydrocarbon generation in the Kelasu tectonic belt and Baicheng sag. However, these hydrocarbon reservoirs were destroyed seriously at the end of the Himalayan and formed irreducible hydrocarbon reservoir and secondary hydrocarbon reservoir after they were regulated and destroyed by tectonic movement. The trap below thick salt layer can be gas reservoir near the Baicheng sag. The formation stage of paleotectonics traps in the Qiulitage tectonic belt match the stage of hydrocarbon generation in the Baicheng sag and the formed hydrocarbon reservoirs were conserved well. Above salt layers, there can form faulted anticline oil reservoir or anticline oil reservoir. There can form gas reservoir below thick salt layer.

The Neogene in the eastern Qiulitage tectonic belt of Kuche foreland basin developed thick salt layer. The explanation of seismic profiles showed that the strata above salt layer, salt layer and strata below salt layer had different structural style and deformation mechanism. The geological models of the strata above salt layer include the thrust fault and fault propagation fold, roof plate reversal thrust fault, thrust drapes and syncline above salt layer. The geological models of salt layer contain the salt pillow, fish tail and salt nappe. The geological models of the strata below salt layer have the fault bend fold, pop-up, type-I triangle belt and thrust fault. The structural type jointly formed by salt layer, strata above salt layer and strata below salt layer is the type Ⅱ triangle belt. Salt-related tectonics formed many types of traps. The deformation stage of these traps matched the stage of gas generation and generated many gas reservoirs in the structural traps below salt layer.

东秋里塔格构造带位于库车前陆盆地的南缘,新生代经历了强烈的构造挤压和构造沉降.平衡剖面分析、生长地层识别和重点井沉降史的数值模拟表明:古新-始新世库姆格列木群沉积期间构造活动微弱并沉降缓慢.渐新世苏维依组沉积期间,构造活动开始加强,沉降速度加快,并形成了一些小断距的逆断层.中新世构造活动进一步加强,沉降加速,沉积了厚层的吉迪克组膏盐层;康村组沉积时期,构造挤压使得膏盐层发生塑性流动,形成盐枕,康村组发育生长地层.随后的上新世库车组沉积期间,研究区先发生快速沉降,然后,随着南天山急剧隆升,冲断作用迅速向南扩展.约在早更新世,库车褶皱冲断带前锋到达东秋里塔格构造带,并最终定型,使得该区发生强烈的构造变形,形成大量的逆冲断裂构造带,膏盐层表现出明显的塑性流动,形成盐推覆构造.

The evaporite beds of the Paleogene Kumugeliemu Formation and Neogene Jidike Formation form regional detachment layers in the Kuqa foreland fold-thrust belt. In the front of the Kuqa foreland fold-thrust, the evaporite bed underwent plastic flow and various structural styles formed inside the detachment with plastic flow of evaporite beds. Based on the field observations, seismic and well data, the deformation structures recognized inside the evaporite bed in the Qiulitag structural belt include salt pillows, salt walls, salt nappes, fish-tail structure, salt welds (fault welds), salt neckening, lentoid thickening and salt stacks. The formation and evolution of various salt structures have a certain sequence. On the whole, the salt structures in the northern part of the Kuqa foreland fold-thrust belt formed earlier than those in the south, while the salt structures in the western Qiulitag structural belt also formed earlier and are of larger size, whereas in the eastern portion the salt structures developed later, with smaller size. The salt structures such as salt nappes, salt welds and salt pillows developed in the Qiulitag structural belt formed earlier than salt walls.

The Yingjisu Sag, situated in northeastern Tarim Basin, was a part of the Central Asia-NW China superlarge Basin in Jurassic, and a cratonic basin (intracontinental depression) formed in Early Jurassic. Based on the recent data of drilling wells in central-northeastern Tarim, a seismic profile across the sag, Q-F-L components and REE patterns of the sandstones, the Jurassic tectono-sedimentary setting of the sag was discussed. The north boundary of the sag might reach to the Kruktag area during that time, and the sedimentary debris come from a fossil orogen to the south, which was composed of the Jinningian granodiorite-diorite, as well as the Lower Paleozoic. To be influenced by the Yanshanian movement, the sag closed and the Jurassic was reformed by the faults in the southern and central parts of the sag. In Creataceous, the Yingjisu Sag deposited again as a part of the North Depression of Tarim Basin. In Cenozoic, the North Depression changed to be an intracontinental foreland basin with creation of the South Tianshan and Kruktag mountain chains, and thrusting of the Kongquehe fault made the Jurassic in the Yingjisu Sag reformed once again.

The differential salt tectonic deformation and segmentation in the Kuqa foreland fold-thrust belt have been observed by field observation, geographic information system(GIS) analysis, 3D visualization, salt-related structural styles, balanced cross section, and estimation of shortening strains and rates. The differential salt tectonic deformation is mainly represented by structural differentiation at different levels, and structural zonation and segmentation in transverse and longitudinal sections. The boundaries between the structural segments are mainly strike-slip faults or tear faults revealed by terminal facets, scratches, steps, misplaced hills and river valleys. The GIS analysis maybe indicates some characteristic details of structural segmentation. Several segments of buried residual salt pillows are revealed by 3D visualization. Distinct structural styles occur in different segments. The analysis of balanced cross section may estimate differential amounts and rates of shortening in different segments. The origin of differential salt tectonic deformation and segmentation may be, on one hand, controlled by the segmentation of the Tianshan mountains, and, on the other, are related to the differential sedimentation and distribution of the salt beds, pre-exist faults and basement uplifts as well as paleotectonic ramps.