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2016 Vol. 38, No. 1

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2016, 38(1): .
Abstract(562) PDF-CN(1052)
Abstract:
Extensional detachment structures in the Lower Yangtze region
Ding Daogui, Luo Kaiping, Liu Guangxiang, Lü Junxiang
2016, 38(1): 1-8. doi: 10.11781/sysydz201601001
Abstract(1245) PDF-CN(1112)
Abstract:
From the Late Cretaceous to Paleogene, the Pacific Plate subducted from south to north. As a result, the East Asia Continent was sheared. Large-scale left-lateral strike-slip movements from south to north and extensional detachment movements which caused the thinning of the crust took place in the Lower Yangtze region (the area to the east of Tanlu Fault, including the northern Jiangsu and South Yellow Sea regions). Three NE-EW oriented rift basin zones developed, including:(1) the Nanling-Guangde and Jurong-Changzhou rift basins in Jiangsu and the southern Anhui; (2) the Dongtai and Funing depressions in the northern Jiangsu and the Qingdao Depression in the southern South Yellow Sea Basin; (3) the Yantai Depression in the northern South Yellow Sea Basin. These basin zones had half-graben structures which were faulted in the south and onlapping in the north. They arranged like dominos from south to north, and formed basin and range structures together with the EW oriented Nanjing-Nantong-Wunansha and Binhai-South Yellow Sea uplifts. These tectonic activities reformed the marine Paleogene basins in the Lower Yangtze region. Marine source rocks in the Paleogene might be deeply buried after uplifting and erosion, which made secondary hydrocarbon generation possible and controlled hydrocarbon generation and distribution in the Miocene.
Composition and effectiveness of marine hydrocarbon sources in the Lower Yangtze area
Luo Kaiping, Ye Deliao, Zhou Lingfang, Peng Jinning, Lu Yongde, Lü Junxiang
2016, 38(1): 9-14. doi: 10.11781/sysydz201601009
Abstract(800) PDF-CN(927)
Abstract:
Tectonic activity in the Late Indosinian-Yanshanian period was the most important event for marine hydrocarbon generation and accumulation in the Lower Yangtze area. The evolution of source rocks could be classified into early and late (secondary) stages of hydrocarbon generation. Accordingly, 3 hydrocarbon accumulations inmarine sequences in the Lower Yangtze area were formed in the Caledonian, Indosinian and Himalayan periods, respectively. There were obvious differences among hydrocarbon sources in the different accumulation periods. The late hydrocarbon accumulation in the Himalayan period was mainly sourced from the secondary generation of the Permian and Silurian source rocks and the thermal cracking of ancient oil pools. The thermal history of the source rocks indicates that the potential location for secondary hydrocarbon generation was limited to the area where Ro was < 1.3% at the end of the Middle Triassic. Oil and gas migration direction and possible accumulations were identified in the light of paleo-fluid potential for the top of the Lower Paleozoic sequence. Combined with the analysis of preservation conditions of the Silurian mudstone seals after the Yanshanian movement, the distribution of oil accumulations could be predicted. Therefore, the effective source rocks might be determined and the potential late accumulations that were formed in their nearby areas identified.
Uplift and cooling history of Qiangtang Basin and its significance
Ren Zhanli, Cui Junping, Liu Chiyang, Li Tiejun, Chen Gang, Chen Zhanjun, Qi Kai, Dou Shuang
2016, 38(1): 15-22. doi: 10.11781/sysydz201601015
Abstract(883) PDF-CN(929)
Abstract:
The low temperature thermochronology of the Qiangtang Basin was studied by the apatite fission track method based on tectonic and thermal evolution. The uplift and cooling ages recorded in the Qiangtang Basin could be divided into two phases:the first one mainly happened from the late Early Cretaceous to the Late Cretaceous (108.7 to 69.8 Ma) and the second one mainly from the Middle-Late Eocene to the Late Miocene (44.4 to 10.3 Ma). The first phase is an uplift and cooling record of the central uplift belt in the Qiangtang Basin, which was caused by the compression of the closing of the Bangong-Nujiang oceans. The second phase can be further divided into three times:44.4-30.8, 26.1-22.6, and 10.3 Ma, among which the Late Oligocene to Early Miocene (26.1-22.6 Ma) is the main uplift period. The second phase is an uplift and cooling record that was caused by the compression due to the collision of the Indian and Eurasian plates. The apatite fission track method was used to determine the uplift and cooling ages of the basin. The Qinghai-Tibet Plateau began to uplift at 44.4 Ma, and an overall strong uplift took place during 26.1-22.3 Ma. The plateau was formed after the strong uplift, and has continued to uplift since the Late Pliocene (10.3 Ma).
Sediment sources and slope belt controlling fan systems in the Dainan Formation in Gaoyou Sag, North Jiangsu Basin
Liu Yurui
2016, 38(1): 23-31. doi: 10.11781/sysydz201601023
Abstract(1167) PDF-CN(1055)
Abstract:
The Gaoyou Sag is a typical half graben of the Dainan Formation which is derived from the disintegration of an unified fault depression of the Taizhou and Funing formations in the North Jiangsu and South Yellow Sea basins. There are 3 genetic types of slope belt including fault slope, erosion slope and bending slope and 2 plane patterns comprising flange and concave edge slope belts which can be classified to 10 types. Sediment sources of the Dainan Formation consist of the rocks in the Taizhou and Funing formations and the basement of the North Jiangsu Basin. The former source contains a large set of mudstones and deeply influences the depositional system of the Dainan Formation. After careful consideration of the rock facies concept, a new type of facies named mud debris flow fan was discovered. Underwater alluvial fan, mud debris flow fan, debris flow fan, fan delta, delta and braided delta are the main facies types in the Dainan Formation. The type, distribution and evolution of sedimentary system in steep slope, gentle slope and depression area of LST, TST and HST in the Dainan Formation are addressed in detail. The relationship among sediment sources, slope belts, fan system and sand body and the main controlling factors of sand distribution are determined. Sand-rich fan systems usually develop along the flange edge slope belt, and mud-rich fans lie along the concave edge.
Reservoir characteristics and hydrocarbon accumulation in Chagan Sag, Yingen-Ejinaqi Basin
Niu Zicheng, Liu Guangdi, Cao Zhe, Wang Peng, Chang Junhe, Zhang Kaidi
2016, 38(1): 32-39. doi: 10.11781/sysydz201601032
Abstract(950) PDF-CN(1280)
Abstract:
The Chagan Sag is an important hydrocarbon exploration area in the Yingen-Ejinaqi Basin. Oil has been discovered in multiple formations including the Bayingebi, Suhongtu and Yingen formations in the Lower Cretaceous. Reservoirs were found mainly in the Wuliji and the central structural belts. Hydrocarbons generated from source kitchens migrated for a short-distance and accumulated in surrounding traps. Hydrocarbon generation, charging and accumulation time analysis showed that accumulation can be divided into three stages:the second member of Suhongtu Formation, the Yingen Formation and the Neogene. Different stages of hydrocarbon accumulation resulted in various physical properties, maturities and biomarkers of crude oils.
Hydrocarbon accumulation in rifted basin tectonic units:A case study of Huoduomoer tectonic zone in the Hailaer Basin
Cui Xin, Li Jianghai, Jiang Hongfu, Yang Shaoying, Li Weibo, Ma Liya
2016, 38(1): 40-47. doi: 10.11781/sysydz201601040
Abstract(1247) PDF-CN(1370)
Abstract:
The Hailaer Basin is a complicated rifted basin which has various hydrocarbon accumulation distribution patterns. We identified the faults and unconformities of the Huoduomoer tectonic zone, and predicted sandstone thickness by inversion based on seismic, logging and well core data. We found that faults, sandstones and unconformities are three dominant hydrocarbon accumulation factors in the research area by analyzing the relationship among them. They not only controlled hydrocarbon migration but also impacted the accumulation process. In the slope belt, sandstones and unconformities provided hydrocarbon migration routes, and reservoir lithology and structural-stratigraphic reservoirs were developed. In the uplift area, faults, unconformities and sandstones worked as hydrocarbon migration routes, and buried hill reservoirs and shallow structural-stratigraphic reservoirs were developed. In the shallow strike-slip fault belt, faults and sandstones allowed hydrocarbon migration, and structural-stratigraphic reservoirs were developed. There are mainly three categories of hydrocarbon accumulation:slope belt mode, strike-slip fault belt mode and buried hill mode. Hydrocarbon accumulation was controlled by faults and unconformities in the uplift area, and by sandstones and lithologic traps in the slope belt.
Forecast and distribution of brittle minerals in shales from the upper section of the third member of Hetaoyuan Formation in the deep sag area of the Biyang Depression
Huang Xin, Hu Shouzhi, Li Shuifu, Lü Qian
2016, 38(1): 48-55. doi: 10.11781/sysydz201601048
Abstract(1045) PDF-CN(1289)
Abstract:
In this paper, we briefly discuss two types of logging prediction methods, namely multi-parameter regression and multi-mineral model. We determined the mineral composition of shales from the upper section of the third member of Hetaoyuan Formation in the deep sag area of the Biyang Depression using these methods and compared this with measured data. The results showed that the major components are quartz and clay minerals, with an average of 24.2% and 23.4%, respectively. The contents of plagioclase, calcite, dolomite, potassium feldspar and pyrite reduce in a descending order. The content of pyrite is about 3.1% on average. Zeolite, gypsum and other minerals are visible only in a few samples. Measured data validation proved that the predictions by logging using these two models are accurate, especially the multi-mineral model, which has an accordance rate of 0.8. The mineral composition section in well BYHF1 and the brittle mineral content in shales from the upper section of the third member of Hetaoyuan Formation showed that the multi-mineral model can predict the distribution rules and trend of minerals better. It is significant for shale oil sweet spot prediction, reservoir mineral evaluation and shale oil development.
Typical filling models of a fractured-vuggy system in carbonate rocks under a moist environment
Cao Jianwen, Xia Riyuan, Zhang Qingyu, Liang Bin, Zou Shengzhang
2016, 38(1): 56-62. doi: 10.11781/sysydz201601056
Abstract(845) PDF-CN(876)
Abstract:
Carbonate reservoirs have strong heterogeneity, and were filled during multiple periods of karstification, which makes hydrocarbon exploration difficult. The Ordovician palaeo karsts in the northern Tarim Basin and the modern karsts in Guilin are examples of karst development in a moist environment, which have similar conditions and characteristics of karst development.According to the principles of "from the surface to the center" and uniformitaranism, combined with oil characteristics and previous research results, we established several typical filling modes of the fractured-vuggy system in carbonate rocks under a moist environment. According to hydrodynamic conditions and filling materials, they can be divided into exogenous underground river filling and endogenous filling models.According to filling structure classification, they can be divided into upper and lower structure filling model, circle structure filling model, and embedded mixed filling model.These models have various filling degree and types of filling material, and the corresponding karst reservoirs also have different physical properties.Generally speaking,the reservoir performance of the exogenous underground river filling modelis better than that of the endogenous filling model, and the reservoir performance of the upper and lower structure filling model is better than that of the circle structure filling model.
Lower limits of pore throat radius, porosity and permeability for tight oil accumulations in the Chang7 Member, Ordos Basin
Wu Kangjun, Liu Luofu, Xu Zhengjian, Dou Wenchao, Luo Anxiang, Fu Jinhua, Tan Xianfeng
2016, 38(1): 63-69. doi: 10.11781/sysydz201601063
Abstract(1204) PDF-CN(1250)
Abstract:
Tight sandstone reservoirs were found widespread in the seventh member of Yanchang Formation (Chang7) in the central Ordos Basin. The lower limit of reservoir porosity and permeability during the accumulation period was critical for hydrocarbon enrichment. We studied these physical properties and microscopic pore throat characteristics of tight sandstones with permeability <0.3×10-3μm2 and porosity < 12% by means of constant-rate mercury injection and Nano-CT scan. The average pore radius is 160μm, and the throat radius is < 0.55μm, average 0.33μm. We analyzed the pressure differential between source rocks and reservoirs, the physical properties of crude oils, and fluid characteristics. Oil and gas displacement simulations in tight gas reservoirs and minimum flow pore throat radius method showed that the Chang7 tight reservoirs in the study area had a minimum pore throat radius of 14 nm, porosity of 4.2%, and permeability of 0.02×10-3 μm2 during hydrocarbon enrichment period. To form large tight oil reservoirs with an oil saturation > 40%, the lower limits for pore throat radius, porosity and permeability should be 0.12μm, 7.3% and 0.07×10-3μm2, respectively.
Types of pre-salt carbonate gas reservoirs and hydrocarbon enrichment factors of Amu Darya right bank area in Turkmenistan
Nie Minglong, Tong Xiaoguang, Liu Qunming, Xu Shubao, Wu Lei, Chen Xiaoshuai, Zhuo Xizhun
2016, 38(1): 70-75. doi: 10.11781/sysydz201601070
Abstract(1410) PDF-CN(1076)
Abstract:
Hydrocarbon resources in the Middle-Upper Jurassic Callovian-Oxfordian carbonate rocks are abundant; however, research on the distribution law of hydrocarbon is relatively backward. Through the study of typical gas reservoirs, analysis of the type of hydrocarbon reservoirs and discussion of the major reasons for high hydrocarbon output, we determined that there are three main types of pre-salt gas reservoirs in carbonate rocks:structural, lithologic and structural-lithologic compound gas reservoirs. Additionally, there are five minor gas reservoirs:anticline, faulted anticline, thrust faulted anticline, reefs and structural-lithologic gas reservoirs. We also discovered that Hercynian basement paleo-uplift controlled the formation of large gas fields and Himalayan extruded tectonic movement formed thrust faulted hydrocarbon accumulation zones. The abundance of gas was controlled by sedimentary facies belts and good seal provided by salt-gypsum cover contributing to the formation of faulted anticline gas reservoirs. The coincidence of large anticline structures and high energy reef beach body was the major controlling factor for the enrichment of natural gas in the west Zarzhu terrace. The coincidence of thrust faulted anticlinal structural traps and large scale fissure type reservoirs is the main reason for the enrichment and high yield of natural gas in the east Bieshikent Depression and Jisaer folded uplift zone.
Oil sources and migration characteristics of Cretaceous reservoirs in the Central Iraq
Du Yang, Cui Yi, Zheng Dan, Wang Juan, Xin Jun, Wang Ziming, Wang Haifeng, Huang Tingting
2016, 38(1): 76-83. doi: 10.11781/sysydz201601076
Abstract(1229) PDF-CN(1185)
Abstract:
Crude oil geochemical data, 3D seismic interpretation, and inclusion analyses were used to examinesource rocks and migration characteristics of the Ahdeb Oil Field in central Iraq.The results indicate that oils in the Cretaceous reservoirs in the Ahdeb Oil Field all originated from reducing and strongly reducing conditions in relatively closed marine deposits. Biomarkers showed that the Cretaceous reservoirs mainly were sourced from the Upper Jurassic Chia Gara Formation. Oil mainly migrated vertically into the Upper Cretaceous Khasib Formation through the SW-NE oriented strike-slip open faults which were controlled by the Najiad fault system. Lateral migration also took place when oils intersected high-porosity and high-permeability reservoirs (Rumaila, Mishrif and Mauddud). The Chia Gara Formation began to expel oil at the end of the Cretaceous. There were two stages of oil migration. The first one took place from the late Cretaceous to Neogene. Traps were not formed yet, and the heavy oils from low maturity source rocks migrated vertically into the Khasib Formation and laterally to the basin fringe along high-porosity and high-permeability formations. The second migration stage was since the Neogene. Due to the Zagros orogeny, source rocks entered the high maturity stage by rapid subsidence, and expelleda mass of high maturity crude oils, which accumulated after trap formation.
Cretaceous petroleum origin in well PSBX1 in the southwestern Tarim Basin
Lü Haitao, Gu Yi, Ding Yong, Huang Jiwen
2016, 38(1): 84-90. doi: 10.11781/sysydz201601084
Abstract(1034) PDF-CN(941)
Abstract:
Well PSBX1 is located in the high part of anticlinal structure no. 1 on the Markit slope in the Tarim Basin, and has oil and gas in the Cretaceous. However, the hydrocarbon origin still remains under discussion. Light hydrocarbons from well PSBX1 indicated that the oils were mainly derived from type I source rocks. Saturated hydrocarbon features indicated that argillaceous materials were the dominant contributors to hydrocarbon generation, which was different from the Ordovician crude oils in the Tahe and Yubei areas. Two-dimensional chromatographic analyses showed that the Cretaceous crude oils from well PSBX1, the Ordovician crude oils from Yubei and Tahe areas, and the Devonian crude oils from Bachu area were sourced from marine mudstones. Carbon isotope characteristics of crude oils from well PSBX1 suggested poorer source quality compared with the Ordovician crude oils from Yubei area and the Carboniferous crude oils from Bachu area. Crude oils from well PSBX1 had higher maturity than those from Ordovician in the Yubei area. Analysis of the Cretaceous crude oils from well PSBX1 and four typical source rocks from adjacent areas in the southwestern Tarim Basin indicated that:(1) the Cretaceous crude oils from well PSBX1 mainly originated from the Cretaceous marine facies source rocks in the southwestern Tarim Basin; and (2) natural gas from the well was mainly sourced from Jurassic humic organic matter, which was similar to that in the Kekeya gas field. The study of the origin of Cretaceous petroleum in well PSBX1 would help oil and gas exploration in the Mesozoic and Cenozoic clastic rocks in the southwestern Tarim Basin.
Bio-precursors of Cretaceous black shales in the Qiangtang Basin, Tibet
Cheng Qiuquan, Yang Ruofei, Hu Guang, Fu Xiugen, Cao Jian
2016, 38(1): 91-98. doi: 10.11781/sysydz201601091
Abstract(1155) PDF-CN(876)
Abstract:
A new sequence of hydrocarbon source rock has been discovered recently in the Qiangtang Basin, Tibet, i.e., the Cretaceous black shales. We investigated the bio-precursors of the shales by an integrated method of organic petrology and geochemistry to improve the understanding of their resource potential. Results showed that the bio-precursors of the shales can be classified into four types in general based on their shapes, sizes, accumulation forms and fluorescence. They include marine benthic algae and zooplankton, bacteria, phytoplankton and terrestrial higher plants in decreasing order of abundance. Benthic algae are the dominant precursors. Similar to source rocks of the same type worldwide, these benthic algae dominant source rocks have high organic matter abundance (TOC>2.0%), reaching the level of good quality and belonging to organic matter type Ⅱ2, indicating that they were deposited in a marine environment. Combined with the regional thermal evolution of the shales, we deduced that the black shales have a good hydrocarbon resource potential and are likely to produce dominantly gas. They may comprise a good exploration target and merit further geological research.
Geochemical features of saddle dolomites in the Penglaiba Formation, Yubei area, Tarim Basin
Jiao Jian, Li Yingtao, Zhang Shaonan, Huang Qingyu, Ye Ning, Yuan Xiaoyu
2016, 38(1): 99-107. doi: 10.11781/sysydz201601099
Abstract(1101) PDF-CN(1609)
Abstract:
Dolomites of the Penglaiba Formation in Yubei area were divided into fine-crystalline matrix dolomites, coarse-crystalline matrix dolomites and saddle dolomite fillings according to the petrographic features. The saddle dolomite fillings have geochemical features similar to the coarse-crystalline matrix dolomites. They appear to be dolomite cements, and are not associated with limestone replacement. Diagenetic fluids for saddle dolomite fillings are inferred to be high-temperature and high-salinity formation brines. The average Sr content of fine-crystalline matrix dolomites is higher than that of coarse-crystalline matrix dolomites and saddle dolomite fillings, while the average Ba content of saddle dolomite fillings is much higher than that of matrix dolomites and coarse-crystalline matrix dolomites. The Mg/Ca ratios of fine-crystalline matrix dolomites, coarse-crystalline matrix dolomites and saddle dolomite fillings are similar. The REE distribution curves of saddle dolomite fillings and matrix dolomites are similar. The inclusion analyses of coarse-crystalline matrix dolomites and saddle dolomite fillings show overlapping fluid properties, which indicates that saddle dolomite fillings are inherited from matrix dolomites.
Physical simulation of the influence of lithological differences on fault zone structure
Shan Yixian, Lao Haigang, Wang Yongshi, Chen Jianping
2016, 38(1): 108-112. doi: 10.11781/sysydz201601108
Abstract(1172) PDF-CN(1368)
Abstract:
The controlling stratigraphic elements for fault zone structure were studied. Possible fault zone structures in sand and mudstone formations were simulated in view of sand and mudstone mechanical properties and contents. The Poisson's ratio and content of mudstone controlled fault zone structure and its internal unit size. The Poisson's ratio of sand did not directly determine fault zone structure, which might be explained by the brittle deformation of sand in the experiment. On the contrary, sand content was a key element for fault zone structure. When mudstone content was fixed, the Poisson's ratio of sand controlled the width of the fault zone. When the ratio of mud to sandstone Poisson's ratio was 1-1.33, dualistic structure developed in the fault zone. When the Poisson's ratios of sand and mudstones were less than 0.28 and 0.34, respectively, a unitary fault zone with loose structure formed. When the Poisson's ratios of sand and mudstones were more than 0.35 and 0.38, respectively, a closed unitary sliding surface developed.
Fault characteristics and their petroleum geology significance:A case study of well Shun-1 on the northern slope of the central Tarim Basin
Li Meng, Tang Liangjie, Li Zongjie, Zhen Sujing, Yang Suju, Tian Yajie
2016, 38(1): 113-121. doi: 10.11781/sysydz201601113
Abstract(1150) PDF-CN(1364)
Abstract:
The geometric characteristics, active stages and formation mechanism of strike-slip faults in well Shun-1 area on the northern slope of the central Tarim Basin were studied through 3D seismic interpretation and combined with fault throw and fault growth index analyses. The study area has clear layered characteristics. Deep structures are mainly of linear strike-slip faults; middle structures are primarily normal faults which group sinistralen echelon and form horst-graben structures, locally forming negative flower structures with a basement strike-slip fault. Small-scale normal faults are developed in shallow structures. Basement strike-slip faults have formed in the middle Caledonian and activated again associated with en echelon normal faults in Silurian during the early Hercynian. The thick Sangtamu Formation mudstone of the Upper Ordovician is identified as a detachment layer, which resulted the decollement between the basement strike-slip fault and its cover. This region has experienced magmatism and widespread extension in the late Hercynian. The rejuvenation of basement strike-slip faults resulted in the local strong compression in the latest Hercynian and fault-related folds in the Indosinian.In the latest Hercynian, basement strike-slip faulting was linked with en echelon normal faults, which could be favorable hydrocarbon migration paths. Strike-slip induced folds cut by en echelon normal faults, forming faulted anticlines, faulted nose and fault blocks, could be favorable traps for petroleum accumulation. The Ordovician palaeokarst that developed extensively near strike-slip fault zones, is an important future target for petroleum exploration.
Mechanism of sand-control and quantitative evaluation of reservoir effectiveness in the northern steep slope of Chengnan area in the Zhanhua Sag
Liu June, Xie Xinong, Meng Tao, Du Xuebin
2016, 38(1): 122-127. doi: 10.11781/sysydz201601122
Abstract(1004) PDF-CN(1253)
Abstract:
Fans are widespread in the Shahejie Formation in the northern steep slope of Chengnan area in the Zhanhua Sag. They are distributed in a complicated pattern. It is difficult to make stratigraphic correlation. Reservoir heterogeneity is strong. As a result, an effective method for the quantitative evaluation of reservoir is demanded. We studied the mechanism of sand-control, and determined the vertical and horizontal evolution rules of reservoirs by the quantitative calculation of slope angle. The distribution of paleo sources matches well with paleotopography. Higher boundary fault angle led to a wider fan root and narrower middle-fan. The distribution of the sand body can be summarized as the matching of the channel and fan, the matching of a large channel and large fan, sufficient supply, continuous development, and vertically backward fan. We found some effective reservoirs by using geophysical and geological statistics. Sand group no. 3 in the lower section of the third member of Shahejie Formation close to wells Binggu604 and Yi159 has a tight fan root, which impedes lateral hydrocarbon migration. Middle fan facies around wells Yi109 and Yi104-4 work as effective reservoirs for either oil or dry gas, and are favorable exploration targets. The area around well Yi107-1 is a fan edge, where few effective reservoirs developed.
Calculation of paleo-pressure in gas reservoirs using fluid inclusions
Shi Weijun, Xi Binbin
2016, 38(1): 128-134. doi: 10.11781/sysydz201601128
Abstract(1448) PDF-CN(1316)
Abstract:
Trapping pressure and trapping temperature of fluid inclusions are important information for the research of petroleum charge history which represents the paleo-pressure and paleo-temperature of gas-oil reservoirs. Gas-bearing (e.g., CH4) inclusions are common in gas reservoirs. The difficulty for the determination of trapping pressure and temperature of inclusions is to accurately measure the concentration of methane. We propose a feasible and credible way to calculate inclusion trapping pressures by using an iteration calculation model based on the hypothesis of constant total volume and composition of intact inclusions and correlation curves of inclusion pressure at room temperature and the Raman shift of methane gas. The method was applied to paleo-pressure of fluid inclusions trapped in the Baota Formation limestones in well Long32 in the southern Sichuan. Results indicated that the trapping pressure is in the range of 884.08-1249.32 bar, which is an overpressure circumstance at a pressure factor of 1.3-1.8.
Evolution of pores in shale during thermal maturation using Small Angle X-ray Scattering (SAXS)
Tian Hua, Zhang Shuichang, Liu Shaobo, Gao Yuan, Zhang Hong, Wang Maozhen, Hao Jiaqing, Zheng Yongping, Zhang Tao
2016, 38(1): 135-140. doi: 10.11781/sysydz201601135
Abstract(1020) PDF-CN(1421)
Abstract:
Nano pores in shale were measured quantitatively using a Small Angle X-ray Scattering (SAXS) method in this study. The volume fraction and distribution function of open and closed pores in the range of miro-pore and meso-pore were obtained in a quick measurement. To quantitatively analyze pore evolution in shale during thermal maturation, some artificial pyrolysis residues of different temperatures and some natural core samples were obtained for SAXS pore measurement. Results show that with the increase of thermal maturity, pore abundance becomes higher. From 300℃ to 600℃, pore width can increase by 35% without considering formation compaction. It is inferred that mature and over-mature shale can develop abundant organic pores, which are advantageous for shale gas storage.
Probabilistic method applied to the static evaluation of shale gas reserves
Zhang Ling, Li Jun, Lu Quanjie, Qiu Yun, Zhuang Li, Chen Ping
2016, 38(1): 141-146. doi: 10.11781/sysydz201601141
Abstract(973) PDF-CN(1369)
Abstract:
Shale gas is abundant in widespread continuous organic shale with low porosity and ultra-low permeability.Commercial production is possible after horizontal well fracturing. The above characteristics limit geological understanding, and result in a high uncertainty for reservoir parameters and reserve calculations.We propose a quantitative evaluation method to resolve the uncertainties through a static evaluation model and expectation curve analysis by using a probabilistic method. It offers a better solution for reserve parameters and reserve calculations, and provides a reference method for reserve evaluation, exploration planning and development, and shale gas production.
2016, 38(1): 147-147.
Abstract(281) PDF-CN(68)
Abstract:

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