石油实验地质

2014, 36(4): .

Abstract(362) PDF-CN(541)

Abstract:

Characteristics of Xinchang Movement in Sichuan Basin and its geological significance

Yang Keming

2014, 36(4): 391-397. doi: 10.11781/sysydz201404391

Abstract(1011) PDF-CN(749)

Abstract:
As the main episode of the Indosinian Movement in the Sichuan Basin, the Xinchang Movement at the end of the Middle Triassic is a revolutionary movement. It marked the end of marine Craton basin development as well as the beginning of Mesozoic-Cenozoic continental basin development in the Sichuan Basin. The Xinchang Movement formed the biggest placantieline of EW trend near Xinchang area. It also produced the basic structural framework called "one uplift and two depressions" in Mesozoic and Cenozoic in the middle segment of the western Sichuan Basin. The movement caused the overall uplift of the Sichuan Basin and the denudation in large scale of the Middle Triassic. Due to the supergene karstfication in the early stage and the deep-buried dis-solution in the late stage, the development of high-quality reservoir at the top of the Middle Triassic was favorable. This set of reservoir with superior forming conditions has a great exploration potential in oncoming future.

Fracture distribution characteristics of 4th member of Xujiahe Formation in Xiaoquan-Xinchang area, western Sichuan

Zhang Keyin

2014, 36(4): 398-404. doi: 10.11781/sysydz201404398

Abstract(677) PDF-CN(539)

Abstract:
Electro-imaging logging was carried out in 19 key wells to study the natural fractures in the 4th member of the Xujiahe Formation in the western Sichuan Basin. There are 4 sets of fractures as followed: the NE-SW trended fractures from the late Indosinian to the early Yanshanian, the SN trended fractures during the middle and late Yanshanian, the NW-SE trended fractures during the late Himalayan, and the ESE-WNW to ENE-WSW trended fractures during the 4th phase of Himalayan. Low-angle and high-angle diagonal fractures account for a large proportion, while horizontal fractures less and vertical fractures seldom develop. The fractures in the southern and northern flanks have bigger linear densities than those in the hinge, where the linear densities of fractures increase as closing to fault system, showing obvious heterogeneity. Medium sandstones, fine sandstones, conglomerates and coarse sandstones are favorable carriers for fractures. In contrast, fractures are underdeveloped in shales. In shales, pelitic siltstones and siltstones, the linear density of fractures decreases obviously as formation thickness increases. As to silty shales and coarse sandstones, there is no apparent congruent relationship.

Diagenesis and porosity evolution of sandstones in Xujiahe Formation, Yuanba area

Chen Gang, Lin Liangbiao, Wang Wei, Chen Hongde, Guo Tonglou

2014, 36(4): 405-410. doi: 10.11781/sysydz201404405

Abstract(918) PDF-CN(748)

Abstract:
The sandstones in the Triassic Xujiahe Formation in Yuanba area are typical low-porosity and low-permeability reservoirs. The diagenesis and porosity evolution of sandstones as well as their influences on reservoir physical properties were studied by means of ordinary and casting thin section microscopic identification, SEM and X-ray diffraction. The main diagenetic effects included compaction/pressolution, cementation, replacement, corrosion and cracking, among which the compaction/pressolution, siliceous and carbonate cementation effects greatly reduced native sandstone porosities and destructed sandstone reservoirs, while the chlorite rim cementation, corrosion and fracturing effects protected and improved reservoirs. At present, the sandstones in the Xujiahe Formation in Yuanba area have entered the middle diagenesis stage A, and partially in the middle diagenesis stage B.Most of the reservoir's primary porosities have been destroyed after severe diagenetic evolution, and the main pore types are secondary pores and associated cracks.

Distribution of carbonate fractured and vuggy reservoirs of Maokou Formation in Luzhou Paleo-uplift during Dongwu Movement, Sichuan Basin

Jiang Ziran, Lu Zhengyuan, Lü Zonggang, Yang Jian

2014, 36(4): 411-415. doi: 10.11781/sysydz201404411

Abstract(762) PDF-CN(805)

Abstract:
The Dongwu Movement which took place at the end of the middle Permian was an important crust movement in South China during Permian. The Luzhou Paleo-uplift was formed during the movement, which led to the uplift and erosion of the Maokou Formation and the formation of paleokarst reservoirs. Based on borehole data, a paleo-geological map of the Luzhou Paleo-uplift before the late Permian was described, and the paleo-geomorphology after erosion as well as the paleo-structure at the beginning of uplift were reconstructed. It was concluded that the Maokou Formation was seriously eroded in the center of the Luzhou Paleo-uplift. The Luzhou Paleo-uplift was in NNE direction with gentle limb in the northeast and steep limb in the southwest. The core of the paleo-uplift was featured by erosion plain. The Maokou Formation was seriously eroded and the paleokarst reservoirs were partially preserved on the gentle limb in the northeast and the adjacent core part of the uplift. The Maokou Formation was seriously caved and the paleokarst reservoirs were saved on the steep limb in the south-west and the adjacent core part of the uplift, where the most favorable areas of fractured and vuggy reservoirs in the Maokou Formation were located.

Reservoir characteristics and karst model of Ordovician Yingshan Formation in Yubei area, Tarim Basin

Qiao Guilin, Qian Yixiong, Cao Zicheng, Yue Yong, Zhang Yongdong, Yang Zhongliang

2014, 36(4): 416-421. doi: 10.11781/sysydz201404416

Abstract(719) PDF-CN(837)

Abstract:
By means of core observation, statistics of pore, hole and fraction, logging, and diagenesis, researches are carried out, indicating that the reservoir space types and property of the weathering crust of the Ying-shan Formation are different among different structures in the Yubei area. The superposition of multi-period karst took place in the weathering crust of the north-east trending structure in the Yubei area, and the reservoir spaces such as cave, hole and fracture developed, showing good reservoir property. In the Pingtai area and the Yudong fault depression, only the middle Caledonian stage Ⅰ karsts generated with poorer reservoir property, mainly of fractures and weak solution pores. Because of dolomitization, bedding solution pore and fracture reservoirs deve-loped in karst insider of the lower member of the Yingshan Formation, and pores and holes occurred alone, showing poor connectivity and no/half filling (oil or calcite). The evolution models of the Yingshan Formation karst reservoirs were established. And the tectonic movement of the middle-late Caledonian and early Hercynian controlled ancient landform and influenced the karst reservoir development in the Yabei area.

Sedimentary reservoir characteristics of sandstone team Ⅱ of Suweiyi Formation in Kudong-Luntai area, Tarim Basin

Shi Yuanyuan, Hong Caijun, Fang Xiaolu, Zhou Fangfang

2014, 36(4): 422-428. doi: 10.11781/sysydz201404422

Abstract(747) PDF-CN(979)

Abstract:
Based on drilling, logging, seismic and testing data, combined with sandstone comparison and seismic attribution technique, it was studied in this paper the sedimentary facies and reservoir features of the updip pinch-out sandstones in the sandstone team Ⅱ of the Suweiyi Formation in Kudong-Luntai area. The target formation, mainly of beach-bar facies, is consisted of brown-grey medium-or fine-grained lithic arkose, and is featured by wave-cross bedding, wave-generated ripple and bioturbation. The reservoir space comprises intergranular porosity, emposieu and fractures. In general, the reservoir is of low/ultra-low porosity and low permeability, high displacement pressure, small pore throat radius, general sorting, mainly fine skewness and partially coarse skewness.The pore structures are generally poor, but the microfractures improve reservoir storage capability. Several updip pinch-out lithologic traps have been found in the study area, showing good exploration potentials in the Suweiyi Formation.

Bogda nappe structure and its relations to hydrocarbon in Xinjiang

Sun Ziming, Shen Jie

2014, 36(4): 429-434. doi: 10.11781/sysydz201404429

Abstract(825) PDF-CN(996)

Abstract:
Located between the Turpan-Hami Basin in the south and the Junggar Basin in the north in the northern Xinjiang, China, the Bogda Mountain extends in the east-west direction, and can be divided into the east and the west segments from Qitai according to geomorphology. The Bogda nappe structure refers to the western segment of the Bogda Mountain, and more attention has been attracted due to its close relationship with oil and gas and other minerals, yet its composition and texture, formation mechanism and evolutionary history are not very clear. The comprehensive analyses of field outcrops, seismic sections and magnetotelluric data show that the Bogda nappe structure mainly consists of the EW-trending Chaiwopu Basin and the Bogda anticlinorium, with the Fukang fault as the frontal boundary while the western and eastern boundaries are defined by the Urumqi-Miquan and Dabancheng-Laoqitai adjustment faults, respectively. The main detachment lies in the middle crust and the root fault is the northern boundary fault of the Middle Tianshan orogenic belt. The Bogda nappe structure is divided by faults into several sub-units with remarkably different features from south to north. Structural pattern changes from basement-involved structure in the south to cover detachment structure in the north. The formation of the Bogda nappe structure is controlled by the deep subduction of the Junggar Basin into the Bogda Mountain. Three evolution stages are identified, as known: rudiment from the Late Jurassic to the Early Cretaceous, large-scale nappe to the north from Cretaceous to Paleogene, and again large-scale nappe to the north which resulted in the strong uplifting of the Bogda Mountain ever since Neogene. Located in the front of the nappe structure and with better settings than the Chaiwopu Basin, the Fukang Sag is a favorable area for middle to large size oil pool exploration.

Bioherm developmental mode in deepwater area of Qiongdongnan Basin

Xi Minhong, Zhou Xinghai, Wang Lin, Yu Xuebing

2014, 36(4): 435-441. doi: 10.11781/sysydz201404435

Abstract(1115) PDF-CN(933)

Abstract:
The analyses of paleostructure, paleogeographic and sea level changes in the deepwater area of the Qiongdongnan Basin show that Miocene is favorable for bioherm development. The characteristics of sequence stratigraphic structure indicate that both slope platform margin and fault-controlled platform margin generate in the south of the deepwater area, giving birth to bioherm with obviously different evolution features. As to the fault-controlled platform margin, the Mei2 period is the main beach-forming period, and the Mei1 period is the main bioherm-forming period. As to the slope platform margin, both beach and bioherm develop during the Mei2 period, and the bioherm development scale is smaller; while in the Mei1 period, only beach develops.

Characteristics and distribution prediction of Cretaceous volcanic reservoirs in Saihantala Sag, Erlian Basin

Li Hao, Gao Xianzhi, Yang Dexiang, Zhu Chao, Wei Qingliang, Zhang Li

2014, 36(4): 442-449. doi: 10.11781/sysydz201404442

Abstract(1127) PDF-CN(722)

Abstract:
With core, thin slice and other analysis methods, this paper analyzed the characteristics of Cretaceous volcanic reservoirs in the Saihantala Sag of the Erlian Basin from lithology, lithofacies, pore type, reservoir heterogeneity, etc. After establishing the relationship between geology and seismic data, this paper predicted some favorable reservoirs of the study region through seismic inversion and seismic attribute analysis methods such as frequency-divided inversion, correlation length analysis and so on. The results showed that volcanic rocks mainly developed in Member 3 of A'ershan Formation of the Lower Cretaceous in the Saihantala Sag, with andesite as the main lithology. Reservoir space types included pores, apricot kernel inner pores, dissolved pores, shrinkage cracks and structural fractures; pore-fissure associations included pore type, fissure-pore type, fissure and vuggy type, fissure type; eruption facies were widely distributed while explosion and volcanic sedimentary facies distributed limitedly; the upper subfacies of eruption facies had excellent reservoir and oil-bearing property; favorable reservoirs distributed along the Zhabu Fault and the upper part of the Member 3 of the A'ershan Formation of the Lower Cretaceous of Sai-60 well block showed great potential; hydrocarbon accumulation model belonged to the model that faults transported hydrocarbon and reservoirs located outside source rocks.

Ultra-deep petroleum accumulation systems in Fergana Basin

Xu Hong, Yang Yufeng

2014, 36(4): 450-458. doi: 10.11781/sysydz201404450

Abstract(949) PDF-CN(663)

Abstract:
In the central graben zone of the Fergana Basin, overpressures were widespread during Cenozoic, which might be related to tectonic compression environment, disequilibrium compaction caused by quick sedimentation and continuous hydrocarbon generation. The ultra-high pressure environment had important effects on deep oil and gas generation, migration and accumulation. The main reservoirs were buried over 5 000 m deep in Neogene, and mainly gave birth to liquid hydrocarbons. The high-porosity and high-permeability sandstone reservoirs in deep formations came from fluvial sandstones under ultra-high pressure, and were featured by low coring recovery rate and high sand production. The low-porosity and high-permeability reservoirs were related to hydraulic fractures caused by high pressure. In the carbonate reservoirs in Paleogene, H₂S was in high content, mainly generating from thermochemical sulfate reduction (TSR), which obviously improved the physical property of gypsum carbonate reservoirs. The formation pressure coefficient was slightly lower than that of Neogene, which could be explained by heavy hydrocarbon gas loss and reservoir space increase. The main petroleum systems in the central graben zone can be divided into the upper E-E₃N system and the lower JK-E_1-2 system. High-production reservoirs of the upper E-E₃N petroleum system are controlled by channel sandstones and overpressure, while those of the lower JK-E_1-2 petroleum system are mainly affected by the gypsum-containing carbonate reservoirs of lagoon facies. The two systems are totally different in pressure and fluid properties, hence are suitable for slicing production.

Hydrocarbon-forming organisms and dynamic evaluation of hydrocarbon generation capacity in excellent source rocks

Qin Jianzhong, Shen Baojian, Tao Guoliang, Tenger, Yang Yunfeng, Zheng Lunju, Fu Xiaodong

2014, 36(4): 465-472. doi: 10.11781/sysydz201404465

Abstract(1169) PDF-CN(914)

Abstract:
Based on the conventional organic geochemical analyses of excellent marine source rocks, simulation experiment and ultra-microscopic organic petrology were applied to study the hydrocarbon generation capacity of different hydrocarbon-forming organisms in excellent source rocks. The bio-precursors of excellent marine source rocks, kerogen type of which belongs to Ⅱ, is mainly composed of benthos (or benthic algae), fungi and bacteria. The hydrocarbon generation potential of these source rocks is equivalent to type Ⅱ kerogen, among which benthic algae is equivalent to type Ⅱ₁ kerogen while fungi and bacteria are equivalent to type Ⅱ₂ kerogen. The planktonic algae ranks second in hydrocarbon contribution,equivalent to type Ⅰ kerogen. The hydrocarbon generation capacity of planktonic algae and benthic algae varies during different mature stages. And in the high-mature and over-mature stage, their hydrocarbon generation capacity and contribution to oil-cracked hydrocarbon are also different. As to the high-mature source rocks in the Lower Paleozoic, a dynamic evaluation is demanded in view of the oil and gas generating capacities of different hydrocarbon-forming organisms or kerogens during each mature stage. The dynamic evaluation of hydrocarbon generation capacity of different hydrocarbon-forming organisms is important for the explorations of both conventional and unconventional oil and gas resources.

Low-pressure accumulation of hydrocarbon recorded by fluid inclusions in T165 reservoir, Tuozhuang area, Dongying Sag

Zhou Zhenzhu, Chen Yong, Zhou Yaoqi

2014, 36(4): 473-478. doi: 10.11781/sysydz201404473

Abstract(818) PDF-CN(737)

Abstract:
Some fractures filled with calcites were found in the deep reservoirs in Tuozhuang area of the Dong-ying Sag. Large numbers of oil-bearing inclusions were contained in the calcite veins. The calcite veins contain two different morphologic crystals, which are fine xenomorphic crystal and medium-crystalline automorphic crystal, and the features of fluid inclusions in the two kinds of crystals are different. Based on optical observation, microthermometry and PVT simulation, this paper revealed the P-T trapping conditions of fluid inclusions, and also analyzed the characteristics of hydrocarbon accumulation. a) The fluid inclusions only recorded one period of accumulation, mainly during Nm. b) In the early accumulation, the pressure coefficient was less than 1, presenting the characteristic of low-pressure migration and injection. The seismic pumping caused by fault activities was the dominant dynamic force of hydrocarbon injection. In addition, it is not reliable to distinguish different accumulation periods by the petrographic characteristics of authigenetic minerals.

Palaeolake environment and organic matter enrichment mechanism of Paleogene Shahejie Formation in Langgu Sag

Diao Fan, Jin Fengming, Hao Fang, Sun Yehua, Zou Huayao, Wang Yuanjie, Zhang Jinfeng, Cao Yijun

2014, 36(4): 479-486. doi: 10.11781/sysydz201404479

Abstract(732) PDF-CN(594)

Abstract:
According to the analyses of element geochemistry, organic geochemistry and isotope geochemistry of mudstone samples from the 4th member (Es⁴) and the lower subsection of the 3rd member (Es³) of the Shahejie Formation in the Langgu Sag, combined with the characteristics of lake evolution and climate change, it was discussed in this paper the changes of salinity, redox condition and productivity as well as the enrichment mechanisms of organic matter. During the formation stage (Es⁴), the lake was deposited in an inactive tectonic activity with arid climate, brackish water, stable water column stratification, water bottom anoxia and lower enrichment of organic matter. When the lake developed to the peak stage (the lower subsection of Es³), the basin subsided strongly with humid climate, fresh water and weak reducing environment in the bottom water. The productivity of surface water was high triggered by a great quantity of nutrients inflowed by direct runoff. The enrichment of organic matter in lacustrine sedimentation was controlled by the productivity and redox conditions during different lake evolution stages. In Es⁴, the enrichment of organic matter was mainly controlled by the anoxic environment in the bottom water, while in the lower subsection of Es³, it was closely related to the high productivity of surface water.

Chemical characteristics of Jurassic formation water and its relationship with hydrocarbon migration and accumulation in middle part of Western Sichuan Depression

Ye Sujuan, Li Rong, Zhang Shihua

2014, 36(4): 487-494. doi: 10.11781/sysydz201404487

Abstract(1003) PDF-CN(866)

Abstract:
Studies on the chemistry of the Jurassic formation water indicate that the formation water is dominantly characterized by CaCl₂ type with relatively low salinity and Na₂SO₄ type water is common in the Upper Jurassic Penglaizhen Formation. In general, the Jurassic formation water is in a closed system, demonstrating its favorableness for hydrocarbon accumulation and preservation. There is a distinct difference in the chemistry of formation water vertically and horizontally. Water composition varies with depth and three vertical variation patterns might be observed, showing the diluting effect caused by the cross-formation flow through faults. Regionally, formation water chemistry is mainly controlled by elevation and faults. In regions of high elevation and fault zones, formation water dilution can occur by meteoric invasion and diagenetic dehydration reactions of lacustrine facies clay minerals in the 5th section of the Xujiahe Formation within the main hydrocarbon source rocks. The Jurassic secondary gas pools in the Western Sichuan Depression correspond generally to the regions with TDS lower than 30 g/L and bicarbonate concentration higher than 300 mg/L, which is different from most oil and gas fields in China. The low-salinity water released from the transformation of smectite to illite and the hydrocarbon and carbon dioxide generated by kerogen-cracking reaction and sulfate-reducing reaction can flow upward through permeable fault zones and therefore cause the coincidence between the distributions of hydrocarbon and formation water with low TDS and high bicarbonate concentration. In regions without faults, it is unlikely to form hydrocarbon accumulation and the formation waters are often characterized by high TDS and low bicarbonate concentration due to poor vertical connectivity.

An approach to hydrocarbon-bearing probability and resource characterization of third-order trap

Yan Xiangbing, Li Jun, Yang Shuang

2014, 36(4): 495-499. doi: 10.11781/sysydz201404495

Abstract(790) PDF-CN(588)

Abstract:
The wildcats aim primarily at the third-order traps in new areas or the new exploration domains, the new series of strata, and the new types of reservoir in old areas. The third-order trap is referred to two or more than two fourth-order traps which are located at the same hydrocarbon zone, have the same trap type and have the similar geological condition for the hydrocarbon accumulation. The hydrocarbon probability and the resource value of the third-order trap are the key factors to decide whether the drilling is performed or not. In the prospect screening and decision analysis, the hydrocarbon-bearing probability of a third-order trap should use the probability product of the trap, charge, reservoirs and seal of the first-drilled fourth-order trap, not the arithmetic mean of the hydrocarbon-bearing probability of all the fourth-order traps. The resource of third-order trap shall be characterized by meeting the prerequisite that the first-drilled fourth-order trap is successful and it is not the arithmetic sum of each fourth-order trap or the third-order trap resource which is under the condition that at least one of fourth-order trap is successful. The size of the third-order trap resource is related to the resources of each fourth-order trap, the hydrocarbon probability, the geological similarity among the fourth-order traps and the selection of the first-drilled fourth-order trap.

Application status and development trend of petroleum exploration risk analysis

Li Jun, Cai Lixue

2014, 36(4): 500-505. doi: 10.11781/sysydz201404500

Abstract(781) PDF-CN(753)

Abstract:
Through the systematic introduction of the application status of petroleum exploration risk analysis within China and aboard, this paper analyzed the major problems in the current exploration and summarized that there would be five trends in the future technology development of the exploration risk analysis. The first one is that the exploration risk analysis will pay more attention to the application of data and information. The second one is that the risk analysis technology will integrate with the commercial or economic reserve evaluation closely. The third one is that the risk analysis will run through the whole process of exploration evaluation and decision. The forth one is that Mathematical Geology and the development of Computer Science will accelerate the quantitative development of the exploration risk analysis. The fifth one is that the multi-disciplinary and comprehensive study will mature with the development of the theory of Petroleum Geology.

2014 Vol. 36, No. 4

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