石油实验地质

2017, 39(4): .

Abstract(299) PDF-CN(264)

Abstract:

Shale gas enrichment conditions in complex geological structure areas: A case study in the front margin of Daba Mountain

Kang Jianwei, Lin Xiaobing, Yu Qian, Tian Jingchun, Men Yupeng, Yan Jianfei, Lin Jiashan, Sun Yuanyuan

2017, 39(4): 437-443. doi: 10.11781/sysydz201704437

Abstract(979) PDF-CN(495)

Abstract:
A series of investigations on both outcrops and drilling cores from the front edge of Daba Mountain were carried out. Organic-rich mudstones collected from the Wufeng-Longmaxi formations in Fengjie-Kaixian-Baiquan-Manyue areas were sampled and analyzed. Information was obtained from thin sections and Scanning Electron Microscopy (SEM), and some relevant laboratory tests including organic geochemistry, X-ray diffraction, He-porosity and permeability and Specific Surface Area were made to summarize the basic geological conditions of Wufeng-Longmaxi formations in the study area. The results show that the organic-rich mudstones in the front edge of Daba Mountain were probably formed in a shallow to deep shelf during the Late Ordovician-Early Silurian. The thicknesses of these mudstones range 40-70 m, and the average total organic carbon (TOC) content is more than 2%. The kerogen mainly shows characteristics of type Ⅰ. The thermal maturity of mudstones ranges 0.82%-3.04%, indicating a high to over mature stage. Additionally, the features of low permeability and low porosity as well as several types of pore microstructures were observed in these mudstones. The analyses of typical wells indicate that the preservation of shale gas is a key element for hydrocarbon accumulation. The well-preserved box-shaped anticlines are most favorable for shale gas preservation.

Classification and formation mechanism of fault systems in the central and northern Tarim Basin

Lü Haitao, Zhang Shaonan, Ma Qingyou

2017, 39(4): 444-452. doi: 10.11781/sysydz201704444

Abstract(1707) PDF-CN(315)

Abstract:
This paper described the horizontal and vertical characteristics of fault systems in the central and northern Tarim Basin, and analyzed the structural model, formation mechanism and evolution history of the fault systems based on extensive 2D/3D seismic data. Four series of fault systems were preliminarily classified. (1) The "X"-type strike-slip fault system (Ⅰ₁) in the Tuoputai area is composed of nearly NNE, NNW trending "X"-style conjugate shear fractures and "1"-style vertical structures and positive flower structures in the Lower Paleozoic strata, and are composed of NNE trending en-echelon extension fractures and negative flower structures and graben-horst structures in the Mesozoic and Cenozoic strata. (2) The NW trending thrust fault system (Ⅰ₂) in the central Tarim area is composed of nearly NW trending basement-involved and cover-slipping thrust faults and "Y"-style structures. (3) The NE trending strike-slip fault system (Ⅰ₃) in the Shuntuo area is composed of nearly NE trending left-lateral strike-slip faults and "1"-style vertical structures and positive flower structures in the Ordovician and lower strata, and is composed of ENE trending en-echelon extensional fractures and negative flower structures and graben-horst structures in the Silurian-Devonian strata. (4) The "T"-type fault system (Ⅰ₄) in the Tahe subsalt area is composed of nearly EW trending thrust faults and nearly NS, NNE trending strike-slip faults in the Lower Paleozoic strata, and is composed of NNE,nearly SN trending en-echelon extensional fractures in the Mesozoic and Cenozoic strata. The study of fault system illustrated the superimposition and transformation between extensional strike-slip and transtensional strike-slip, and considered that it was mainly controlled by five stages of subduction and collision orogeny in the paleo oceanic basin on the basin margin. Combined with the dynamic evolution mechanism of the study area, the evolution stage of the central and northern Tarim Basin was divided into the strong compression-weak strike-slip period (the Middle-Late Ordovician), the strong compression-strong strike-slip period (the Late Silurian-Middle Devonian), the strong extension-weak strike-slip period (the Late Carboniferous-Early-Mid Permian), the strong compression-weak strike-slip period (the Late Permian-Triassic), the weak compression-weak strike-slip period (the Jurassic-Neogene).

Controls of intensively faulted zones on hydrocarbon migration and accumulation: An example of Fuyu oil layer in Xingbei area, Songliao Basin

Liu Junqiao, Zhang Tong, Lü Yanfang, Zhang Mengdi, Sun Tongwen, Jiang Guipu, Xue Pan

2017, 39(4): 453-460. doi: 10.11781/sysydz201704453

Abstract(1307) PDF-CN(331)

Abstract:
The types and genetic mechanism of intensively faulted zones in the Fuyu oil layer in the Songliao Basin were studied based on 3D seismic data and combined with the plane and profile characteristics of intensively faulted zones, so as to identify the controls of intensively faulted zones on hydrocarbon migration and accumulation. Reservoir dissecting technology was applied, and the distribution characteristics of intensively faulted zones, hydrocarbon and sand bodies were taken into consideration. Several conclusions were made as follows. (1) Intensively faulted zones are widely distributed in the Fuyu oil layer in Xingbei area, including the parallel graben belts caused by stretching and the hybrid intensively faulted zones caused by coupling. (2) Sheltered by transverse intensively faulted zones, the ramp zones to the south and east of the central anticline have no oil or gas enrichment. Hydrocarbon was enriched in the hanging wall of boundary reverse faults outside intensively faulted zones. The larger the scale of fault displacement, the higher the degree of oil enrichment. (3) The boundary faults of consequent intensively faulted zones can be hydrocarbon migration pathways along the fault strike. Tectonic inversion occurred in the central anticline zone, and the "uplifted graben" morphology formed in intensively faulted zones, where oil and gas accumulated.

Fluid activity in faults in the northwestern Junggar Basin and its influence on fault opening and sealing

Zhao Leqiang, Jia Fanjian, Cao Jian, Liu Hui, Bian Xuemei, Gao Jianxiong

2017, 39(4): 461-466. doi: 10.11781/sysydz201704461

Abstract(1331) PDF-CN(261)

Abstract:
The fluid flow process and its effect on fault opening and sealing in the northwestern Junggar Basin were studied based on field outcrop, drilling, logging and geochemical analyses. Four stages of fluid activities have occurred. During the early period of fault formation, the sliding fracture zone got the most concentrated force and was extensively crushed. The first phase of mantle-derived fluid entered the sliding fracture zone and continuously precipitated minerals, which made physical properties become worse. The second phase of mantle-derived fluid migrated in the parts where physical properties were relatively better in the sliding fractured zone. The cemented minerals and the mineral veins formed in the first phase closed the sliding fracture zone. The third phase of fluid from the basin mainly migrated in the fracture zone of the active wall where physical properties were relatively better, and a small part entered the induced fracture zone of the passive wall. In the fourth phase, atmospheric precipitation entered the induced fracture zones of the active wall and the passive wall where physical properties were relatively better. In the initial stage, dissolution was essential, while in the late stage cementation was stronger. When the fluid from the basin was active in the third phase, large-scale hydrocarbon was expelled from the basin. As a result, the fluid often contained large amounts of oil and gas. Hydrocarbon mainly migrated in the induced fracture zone of the active wall, and secondly in the induced fracture zone of the passive wall. The sliding fracture zone played the role of closure not transport.

Evolution of the temperature-pressure system and far-source hydrocarbon accumulation in Junggar Basin

Ma Xiaowei, Zhu Chuanzhen, Lin Yuxiang, Shu Yong

2017, 39(4): 467-476. doi: 10.11781/sysydz201704467

Abstract(1214) PDF-CN(211)

Abstract:
The controls of the formation and evolution of the temperature-pressure system on a far-source hydrocarbon accumulation in the Junggar Basin were studied systematically based on the analyses of temperature and pressure fields and guided by the theory of system thermodynamics. The uplifted area of the basin is featured by high temperature, high temperature gradient and high heat flow, while the depressed area is opposite. Overpressure developed in the depressed area and decreases in irregular rings to the edge of the basin. Strong overpressure developed in the south of the basin and the central depressed area, medium overpressure developed in the east of the basin, and weak overpre-ssure developed on the northwestern margin of the basin. Vertically there are three sets of relatively closed temperature-pressure systems in the basin: the Permian-Upper Triassic system, the Lower Jurassic system and the Cretaceous-Paleogene system. The sedimentation rate of the basin was relatively fast during the Hercynian period, and the energy accumulation of temperature and pressure took place from the Permian to the Late Triassic. Tectonic movements were intense in the Yanshanian period, and fracture activities cut through cap rocks frequently at the edge of the uplifts. The temperature-pressure field adjusted, leading to oil and gas migration and accumulation through cap rocks. It was the main period for the formation of far-source reservoirs. The basin was tilting, descending in the south and uplifting in the north, in the Himalayan period, and fault activity was weak. The temperature-pressure system was relatively stable and helped oil and gas preservation. The far source lithologic oil and gas reservoirs are mainly distributed in the low-energy field of temperature-pressure in the horizontal, such as the northwest of the basin, Mobei-Mosuowan area, Luliang uplift and the eastern uplift. These areas are favorable for exploration of far-source oil and gas reservoirs in the Junggar Basin.

Influencing factors of sandstone properties of the second member of Funing Formation in the Jinhu Sag, Subei Basin

Ma Yingjun

2017, 39(4): 477-483. doi: 10.11781/sysydz201704477

Abstract(1303) PDF-CN(254)

Abstract:
The lithologic characteristics of minerals, reservoir physical properties and pore structure of sandstones in the second member of Funing Formation in the Jinhu Sag of Subei Basin were studied based on petrographic thin sections, casting thin sections, porosity and permeability, and the influencing factors for reservoir physical properties were discussed. The sandstones in the second member of Funing Formation are generally fine grained. The average maturity of rock composition is similar among different regions, and range widely. The sandstones on the western slope of Jinhu Sag have better physical properties while those in the other areas are featured by low porosity and low to extra low permeability. Compaction and carbonate cementation are the main reasons leading to poor reservoir physical properties. Dissolution and hydrocarbon filling are important factors to restrain diagenesis and improve reservoir characteristics. The western slope has relatively better porosity and permeability and is a favorable target for hydrocarbon pools.

Forming mechanisms of reservoir “sweet spots” in tight sandstones of Chang8 Formation, Honghe oil field, Ordos Basin

Wang Fubin, Yin Wei, Chen Chunfang

2017, 39(4): 484-490. doi: 10.11781/sysydz201704484

Abstract(1134) PDF-CN(2042)

Abstract:
Reservoir "sweet spots" (that is, relatively high quality reservoirs) exist locally in the low-permeability, tight sandstone reservoirs of Chang8 Formation in the Honghe oil field, controlling hydrocarbon enrichment and production. This reservoir provides evidence and direction for prediction of tight sandstones to study their forming mechanisms. The impacts of sedimentation, diagenesis, fracturing and oil emplacement on reservoir quality of the tight sandstones during the whole reservoir evolution process from sedimentary construction to diagenetic reformation were systematically analyzed using rock sections, casting thin sections, cathode-luminescence, scanning electron microscopy, micro fluorescence observations and statistics, combined with the analyses of mineral composition, volume of cementation minerals and reservoir physical tests. The results indicate that sedimentation is the most important factor controlling tight sandstone reservoir properties by providing a material basis and controlling the original properties of tight sandstones. Diagenesis is another factor which controls the porosity evolution of tight sandstones, and construction diagenesis controls the formation of reservoir "sweet spots" in tight sandstones and the distribution of "sweet spots" in pore-type tight sandstone reservoirs. The superimposed reformation of structural fractures improves the reservoir properties of tight sandstones, especially the permeability, resulting in the distribution of "sweet spots" in fractured tight sandstone reservoirs. Oil emplacement inhibits cementation as one of the important mechanisms of "sweet spot" preservation in the tight sandstone reservoirs.

Reservoir characteristics and formation mechanism of the 4th member of the Leikoupo Formation in Longmen Mountain front

Wang Qiongxian, Song Xiaobo, Wang Dong, Long Ke

2017, 39(4): 491-497. doi: 10.11781/sysydz201704491

Abstract(1124) PDF-CN(265)

Abstract:
Over one hundred meters of tidal-flat facies dolomite with dissolution-pores developed in the Middle Triassic Leikoupo Formation in the Longmen Mountain front in the western Sichuan Basin. It can be further divided into the upper and lower reservoirs. The analyses of well cores, debris, thin sections and physical properties show that the properties of the lower reservoir, dominated by superposed dolomites, are better than those in the upper reservoir, dominated by limestones. The reservoir formation mechanism was studied using SEM and inclusion homogenization temperature analyses based on rock physical property statistics and reservoir space characteristics. Dolomitization, dissolution in the penecontemporaneous period and dissolution during the burial period formed this good reservoir. Widely distributed dolomites, which developed in a tidal-flat facies, established an important foundation for a steady distribution of reservoirs, dissolution in the penecontemporaneous period determined the formation and distribution of good reservoirs, and dissolution in burial period was favorable for the retention of pores and the increase in permeability, further improving reservoir quality.

Characteristics of zircon in the Huagang Formation of the ccentral inversion zone of Xihu Sag and its provenance indication

Qin Lanzhi, Liu Jinshui, Li Shuai, Zhao Hong, Chang Yinshan

2017, 39(4): 498-504. doi: 10.11781/sysydz201704498

Abstract(1057) PDF-CN(191)

Abstract:
The Huagang Formation of the central inversion structural belt in the Xihu Sag is one of the most significant exploration areas of the East China Sea Basin. But currently, the research of the provenance system of Huagang Formation is relatively weak, which severely limits the studies of sand-body distribution and reservoir characteristics. The provenance characteristics of sandstones in the Huagang Formation were studied based on the zircon U-Pb dating of core samples and combined with seismic reflection features. The results show that the large sand body of Huagang Formation is composed of sandstone of three ages, which are Precambrian (accounting for the largest proportion), Paleozoic and Mesozoic. The large sand body sourced from the Precambrian in the Hupijiao reef in the north, and extended to the south through the sag. Affected by the Haijiao reef in the west and the Diaoyu Islands folding zone in the east, the provenance from the north was dominant while those in the east and west were secondary.

Dynamic assessment of organic carbon content and hydrocarbon generation and expulsion efficiency in source rocks

Shen Baojian, Qin Jianzhong, Feng Dan, Tao Guoliang, Yang Yunfeng, Tenger, Pan Anyang

2017, 39(4): 505-510. doi: 10.11781/sysydz201704505

Abstract(1362) PDF-CN(309)

Abstract:
The relationship of the yields and efficiencies of oil generation and expulsion with total organic carbon content (TOC) was analyzed based on thermal simulations of typical natural marine source rocks and artificial source rocks. (1) The simulation results show a positive linear correlation between the yields of oil generation and expulsion and TOC, and a nonlinear correlation between the efficiencies of oil generation and expulsion and TOC. The correlation coefficients are related to kerogen type, lithology and thermal maturity. (2) Source rocks with high TOC contents (generally over 2.0%) always have higher yields and efficiencies of oil generation and expulsion throughout the simulation experiments, when compared to source rocks with middle (0.5%-2.0%) and low (less than 0.5%) TOC contents, which indicates that only source rocks with high TOC contents have the capacity to form large oil fields. Source rocks with low TOC content do not generate large hydrocarbon accumulations even if they are very thick. (3) In the process of geological evolution, the TOC content and the capability of hydrocarbon generation and expulsion for source rocks are changing continuously. Correspondingly, the evaluations of source rock and resources should be dynamic.

Source rock characteristics of the Carboniferous Karashayi Formation in the Tarim Basin

Li Jingchang, Wu Jiang, He Hong, Xu Jie, Guo Xin

2017, 39(4): 511-519. doi: 10.11781/sysydz201704511

Abstract(1102) PDF-CN(160)

Abstract:
The organic matter abundance, thickness, distribution range, organic matter type and maturity of clastic rocks in the Carboniferous Karashayi Formation were studied in order to further clarify the scale of hydrocarbon source rocks in the Carboniferous strata in the Tarim Basin. The period when sandstones and mudstones were deposited in the Karashayi Formation was the most important period for the generation of high quality hydrocarbon source rocks. The lagoon facies area close to the Mazatage structural belt with Macan1 well at the center is the best area for high quality source rocks, even better than the southwestern Tarim Basin. Source rocks in this area are about 60 m thick, generally low mature or mature. The organic carbon content is greater than 2%. However, in general, the distribution of high quality source rocks in the Karasayi Formation of the Tarim Basin is relatively limited.

Thermal evolution modeling of Mesoproterozoic source rocks in the Ordos Basin

Tian Gang, Song Lijun

2017, 39(4): 520-526. doi: 10.11781/sysydz201704520

Abstract(1081) PDF-CN(288)

Abstract:
The Mesoproterozoic is a potential stratum of gas accumulation and production of the Changqing oil field in the Ordos Basin. However, few recent studies have been made on the thermal evolution history of source rocks.Applying the PetroMod basin modeling software, the thermal evolution histories of the Proterozoic source rocks in each tectonic unit of the study area were simulated taking measured R_o values as calibration and based on the analyses of lithology, erosion thickness restoration and ancient heat flow. The differences of thermal evolution of source rocks in different tectonic units were discussed. Some favorable exploration areas were predicted combining with oil and gas system analyses. The results show that: (1)The hydrocarbon generation threshold of Mesoproterozoic aulacogens and peripheral source rocks is much earlier than others. The maturation stage of other aulacogens and peripheral source rocks is also earlier than others except for the mid-northern part of the western margin thrust belt, and it is in a stage of dry gas generation at present. The source rocks in the Changcheng System reached the hydrocarbon generation threshold at the end of the Late Permian and are generating dry gas now, except for those in the Yimeng uplift, which became mature late and are still generating wet gas. The source rocks in the Jixian System reached the hydrocarbon generation threshold from the end of the Late Permian to the beginning of the Middle Triassic, became mature as the basin depositional center migrated continuously to the west and influenced by intrusions in the northern Tianhuan syncline and western Weibei uplift, and finally entered the dry gas stage in the early Cretaceous. (2)The central area of the Weibei uplift, southern Tianhuan syncline, northwestern Yishan slope,and the central part of the Yimeng uplift in the Ordos Basin are favorable exploration areas.

Simulation of hydrocarbon generation of the Paleozoic coals in the Dongpu Sag, Bohai Bay Basin

Zhang Hongan, Zhang Shuang, Zhang Yunxian, Yao Suping

2017, 39(4): 527-534. doi: 10.11781/sysydz201704527

Abstract(1178) PDF-CN(157)

Abstract:
The hydrocarbon generation and expulsion characteristics under different temperatures and pressures and the hydrocarbon potential of coals were studied based on the thermal simulation with water in a half-open system of coals using the geological conditions of the Carboniferous-Permian coals in the Dongpu Sag, Bohai Bay Basin. The results indicate that: (1) The Carboniferous-Permian coals in the Dongpu Sag show a very high hydrocarbon generation potential. The yield of hydrocarbon generated can reach 254 mg/g, among which the gaseous products account for 220 mL/g, and the liquid part about 145.8 mg/g. (2) The yield of thermal cracking oil from coal shows a single peak, which appears at 325 ℃ (R_o=1.08%). Almost 40% of the liquid hydrocarbon was expelled from coal. (3) The hydrocarbon generation of coal followed an increasing tendency in several stages. The intervals 325-400 ℃ and 500-550 ℃ are the stages when gaseous hydrocarbon shows a rapid increase. The former increase should be a result of thermal cracking of liquid hydrocarbon, while the latter maybe caused by the condensation of aromatic hydrocarbon. (4) The Carboniferous-Permian coals in the Dongpu Sag yielded both oil and gas, with an oil generation potential appro-ximately equal to that of the Jurassic coals in the Turpan-Harmi Basin, and a gas generation potential matching the Carboniferous-Permian coals in the Ordos Basin.

Application of C₄-C₈ light hydrocarbons in geochemical studies: A case of condensates in Dawanqi oil field, Tarim Basin

Kong Ting, Zhang Min

2017, 39(4): 535-543. doi: 10.11781/sysydz201704535

Abstract(1035) PDF-CN(163)

Abstract:
The GC analysis of whole oil samples demonstrates that a suite of 81 crude oils from different production wells and reservoir horizons derived from the Dawanqi oil field contain a high abundance of light hydrocarbon, and partial oils were biodegraded to different degrees. C₄-C₈ light hydrocarbons were chosen for geochemical studies including oil maturity and secondary alteration. The maturity parameters of light hydrocarbons indicate that the calculated reflectance of oils was about 0.9%, suggesting condensates in the mature stage. For biodegraded oils, with biodegradation increasing, Mango's light hydrocarbon parameters K₁ values reduce and K₂values increase remarkably. Furthermore, MCH index also increases. Methylcyclopentanes are depleted faster than ethylcyclopentanes, implying that there is a trend of lower susceptibility to biodegradation with greater alkyl substitution. Combined with maturity and organic matter input, it is speculated that oils in the Dawanqi oil field are secondary condensates. The comparison of light hydrocarbon parameters indicates that condensates in the Dawanqi oil field are consistent with crude oils from the Dabei oil field and the southern area of Dawanqi oil field. Based on the geological background of the Dawanqi oil field in Tarim Basin and the condensate accumulation pattern, it indicates that crude oils from the Dabei oil field and the southern area moved to the Dawanqi oil field through deep faults and underwent evaporative fractionation.

Pore space restrictions on microbial activities in the Second White Specks shale of the Western Canada Sedimentary Basin

Yin Mengsha, Huang Haiping

2017, 39(4): 544-555. doi: 10.11781/sysydz201704544

Abstract(1144) PDF-CN(236)

Abstract:
A suit of thirteen shallow biogenic gas source rock samples taken from the Second White Specks Formation (2WS) in well A at South Alberta Gas Field (SAGF), Western Canada Sedimentary Basin (WCSB) were analyzed by a laser particle size analyzer, nitrogen adsorption and GC-MS to obtain grain size, surface area, pore size distribution, and hydrocarbon molecular compositions, in order to get an insight into the constraining effects of pore space on microbial activity within shallow buried source rocks. The samples are organic rich with high TOC values, shallowly buried and immature, which are suitable for microbial activity. Pore size distributions derived from nitrogen adsorption isotherms illustrate the dominance of mesopores (2-50 nm). Molecular geochemical parameter analysis indicates that the compositions of extractable organic matter are basically attributed to the variation of source input with no solid evidence of biodegradation. The analysis of pore size distribution shows that very limited portion of pores with diameter over 200 nm cannot sustain extensive microbial activity, which possibly accounts for the slight biodegradation of organic matter in shale. Biogenic source rocks capable of generating large amount of biogenic gas are supposed to have a large proportion of pores larger than 200 nm. Traditional schemes for potential biogenic gas source rock assessment may have neglected the decisive role of shale pore space in bacteria activity.

Quantitative characterization of microscopic pore heterogeneity in tight sandstones and its reservoir significance: A case study of the Shanxi Formation in X area, Ordos Basin

Lu Chengang, Zhang Suian, Mao Xiaoxiao, Zhao Difei

2017, 39(4): 556-561. doi: 10.11781/sysydz201704556

Abstract(1540) PDF-CN(342)

Abstract:
This paper presents a new method to extract the face rate of casting a thin section image of tight sandstones from the Shanxi Formation in the eastern Ordos Basin based on Matlab software programming. A heterogeneity coefficient U is proposed according to face rate, which quantitatively characterizes microscopic pore heterogeneity. The reser-voir significance of the heterogeneity coefficient U and the relationship between reservoir physical properties and microscopic pore heterogeneity were discussed. The results show that the micro-heterogeneity of the tight sandstone reservoirs in X area is very strong and the micro-pore distribution is very heterogeneous. A larger heterogeneity coefficient U and a stronger reservoir heterogeneity is associated with poorer reservoir physical properties, and vice versa.The microscopic heterogeneity of tight sandstone reservoirs influenced the microscopic development characteristics of pore space (reservoir space and permeability). The quantitative evaluation of the heterogeneity coefficient of tight sandstone reservoirs can guide the selection of high-quality strata for production.

Determination of reflectance of organic matter by digital image processing

Yang Yunfeng, Shen Baojian, Tenger, Xu Ershe

2017, 39(4): 562-566. doi: 10.11781/sysydz201704562

Abstract(1078) PDF-CN(293)

Abstract:
The reflectance of organic matter is a basic parameter for source rock assessment and thermal evolution history study in a basin. At present, the main technique for reflectance measurement is manual despite heavy operator influence on the results. This paper discussed the relationship between vitrinite reflectance and grey level determination by digital image processing, and tried to determine the vitrinite reflectance by grey level. Simultaneous measurements of vitrinite reflectance values and grey levels were implemented on standard materials and geological samples. The trends of vitrinite reflectance values and grey levels coincide with each other, which demonstrate that it is feasible to quantify the vitrinite reflectance using grey level. For high-over maturity, however, more research is needed.

Tectonic evolution and its physical simulation of Wuxia fault belt in the northwestern margin of Junggar Basin

Li Xiao, Lao Haigang, Hu Qiuyuan, Zhao Li

2017, 39(4): 567-572. doi: 10.11781/sysydz201704567

Abstract(1418) PDF-CN(195)

Abstract:
The tectonic characteristics of the Wuxia fault belt in the northwestern margin of the Junggar Basin were systemically studied based on a large number of 3D seismic data. The study area has experienced five tectonic evolution periods, including the collision of foreland basin, thrust-nappe structure of foreland basin, thrusting fold of interior depression, uplift and denudation of interior depression, and cover setting. The forward modeling of the tectonic evolution of some typical profiles ever since the Late Carboniferous fit well with actual geological conditions. The results showed that the Wuxia fault belt transformed from the thrust with piggy back in foreland basin to thrusting with overstep in the interior depression. Experimental results also indicated that the formation and development of Wuxia fault belt were mainly controlled by the NW-SE oriented compressive stress field, which was mainly affected by some key factors such as plate activities, orogenic belts, and frontier basin-controlling faults.

Probability distribution of reservoir parameters in the B oil field, Pearl River Mouth Basin

Tu Yi, Yang Jiao, Wang Xiuling, Wan Jun

2017, 39(4): 573-579. doi: 10.11781/sysydz201704573

Abstract(1056) PDF-CN(379)

Abstract:
A block of the Pearl River Mouth Basin has a large trap area, irregular structure and limited well data and thus to get accurate reserve size, potential and risk, the probability method is most effective for rapid reserve assessment. The Z5 reservoir in the B oil field was taken as an example. Considering steep wings, long middle transition zone and the low level of well control, an area/thickness/shape factor method was used to construct a physical model of bulk-volume rock. N modules were divided according to the distribution form of reservoir. The form of Z5 reservoir was precisely described according to each module, which could reduce the influence of irregular structural form on reserve. Logarithmic normal distribution was used to analyze effective thickness and porosity. Normal distribution was chosen for oil saturation. A single value distribution model was adopted to study oil-bearing area, volume coefficient and crude oil density. The probability distribution of various reserve parameters and a reserve probability distribution model were established. The results show that the P_mean reserves of the approximate method were close to those of the deterministic method, and the error between them was less than 4%. Combined with reserve sensitivity analysis results of the geological parameters, the study could guide the studies of reserve sensitivity, economics, risk and potential, and provide a theoretical basis for development plans and decisions.

A fine scale assessment of favorable exploration areas in the Carboniferous Kalashayi Formation in the Tahe oil field

Du Weiwei, Shi Yuanyuan, Hong Caijun

2017, 39(4): 580-586. doi: 10.11781/sysydz201704580

Abstract(1035) PDF-CN(130)

Abstract:
The Carboniferous Kalashayi Formation in the Tahe oil field shows a good potential for hydrocarbon exploration in clastic rocks. Deep burial depth, small sand body scale and complicated controlling factors for hydrocarbon accumulation have made it necessary for a fine scale assessment of the study area. The controlling factors for hydrocarbon accumulation in the Carboniferous Kalashayi Formation, such as oil and gas distribution, fault systems, sand bodies and underlying strata, were analyzed. The maps of reservoir distribution, oil and gas shows, fault location, sedimentary facies and strata layout were applied to make a comprehensive evaluation of the Kalashayi Formation. The study area was divided into three zones. In the most favorable area, we focus on lithologic traps such as underwater distributary channels, underwater flood fans distributed like flakes, and mouth bars. In the favorable area, we look for banded underwater distributary channels, mouth bars and sheet sandstones which were reformed by tides. In the potential area, we look for sand flats distributed like flakes.

Jiang Xingge

2017, 39(4): 587-587.

Abstract(446) PDF-CN(159)

Abstract:

2017 Vol. 39, No. 4

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