Xinjiang Petroleum Geology Founded in 1980, is sponsored by Xinjiang Petroleum Society, and jointly sponsored by Xinjiang Oilfield Company, Tarim Oilfield Company, Tuha Oilfield Company of PetroChina and Northwest Oilfield Company of Sinopec. The journal has extensive communications and exchanges with petroleum industry-related universities, colleges, research institutes, other journals and publishers in China. Xinjiang Petroleum Geology has many columns such as Oil and Gas Exploration, Reservoir Engineering, Application of Technology, Discussions...
01 April 2021, Volume 42 Issue 2 Previous Issue   
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OIL AND GAS EXPLORATION
Geological Reserves Assessment and Petroleum Exploration Targets in Shunbei Oil & Gas Field
QI Lixin, YUN Lu, CAO Zicheng, LI Haiying, HUANG Cheng
2021, 42 (2):  127-135.  doi: 10.7657/XJPG20210201
Abstract ( 81 )   HTML ( 14 )   PDF (7969KB) ( 70 )  

Shunbei oil & gas field is a typical fault-controlled one, in which the formation and evolution of the reservoirs are closely related to fault activities. The basic constitution and scale of the reservoirs are not affected by water-rock interaction, which are essentially different from dissolved fractured-vuggy reservoirs. The geological reserves assessment methods established for dissolved fractured-vuggy reservoirs are hardly applicable for assessing the geological reserves and making exploration decisions for the fault-controlled reservoirs. In view of the characteristics of the fault-controlled reservoirs, we extracted weak, diffracted and low-frequency signals of the horizontal layered and anisotropic medium, and improved the 3D image quality of the steep strike-slip fault zones, and finally developed a comprehensive analytical technology for assessing the strike-slip fault zones. On this basis, using innovative methods and technologies like 3D description and facies-controlled inversion, a series of technologies such as reservoir description, reserves assessment and resource optimization and evaluation were established for fault-controlled fractured-vuggy reservoirs. Since applying these methods to 18 first-order fault zones in Shunbei oil & gas field, 1.7 billion tons of OOIP(oil equivalent) has been proved, and a production capacity of 1 million tons of oil equivalent per year has been constructed. In addition, based on the overall petroleum geological conditions and evaluation of exploration zones, it’s found that hydrocarbon accumulate in the whole field, and the exploration zones outside the first-order fault zones also have abundant resources and great exploration potentials. These understandings point out the future directions and successive plays for oil and gas exploration, and lay a foundation for the middle-long term development of Shunbei oil & gas field.

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Hydrocarbon Accumulation of Ultra-Deep Ordovician Fault-Karst Reservoirs in Shunbei Area
YUN Lu
2021, 42 (2):  136-142.  doi: 10.7657/XJPG20210202
Abstract ( 45 )   HTML ( 3 )   PDF (1433KB) ( 44 )  

In the Shunbei area of Tarim basin, Ordovician carbonate fault-karst reservoirs are controlled by strike-slip faults. These faults are distributed in rows and belts, and typically characterized by “laterally superimposed segments, vertically layered deformation and superimposed transformation”. On the plane, there are three types of fault systems: NE-SW, NW-SE, and NNE-SSW; and the faults of the Middle-Lower Ordovician can be divided into four styles: superimposed pull-out, superimposed indentation, linear translation, and composite graben. The different evolution of the Middle-Lower Cambrian source rocks in the east and west of the Shunbei area controls the present resource accumulation shown by “western oil and eastern gas”, and the plane segments of the fault zones control the internal structures of the reservoirs. The Ordovician fault-karst reservoirs have good source rock, reservoir and cap rock conditions. The faults communicate with the source rocks downwards, and the development of the fault-controlled fractured-vuggy reservoirs control the enrichment of oil and gas reservoirs. All these are mainly affected by the activity intensity, segmenting style, and the angle with the present principal stress direction in the fault zones.

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Significance of Secondary Hydrocarbon Generation and Crude Oil Cracking in Paleo-Reservoirs to Hydrocarbon Accumulation:A Case Study of Cambrian Source Rocks in Bachu-Maigaiti Area of Tarim Basin
CAO Zicheng, XU Qinqi, YU Tengxiao, QIN Hua, GENG Feng, HAO Jianlong, DENG Shang
2021, 42 (2):  143-151.  doi: 10.7657/XJPG20210203
Abstract ( 39 )   HTML ( 4 )   PDF (741KB) ( 27 )  

In order to analyze the relationship between the thermal evolution history of Cambrian source rocks and hydrocarbon accumulation in the Bachu-Maigaiti area, the thermal evolution history and the denudation of unconformity from Hercynian movement to Himalayan movement were rebuilt by analyzing the track chronology of apatite fission. The results demonstrate that secondary hydrocarbon generation took place in the Cambrian source rocks in the Southwest depression during the late Himalayan movement, which was caused by rapid burial and temperature increase since the Paleogene. Influenced by continuously uplifting, most Cambrian source rocks in the Bachu uplift didn’t have the conditions for secondary hydrocarbon generation. The crude oil generated in the Cambrian source rocks from middle Caledonian movement to early Hercynian movement might accumulate and form paleo-reservoirs on a large scale in the Hetian paleo-uplift, and the paleo-reservoir was quickly buried deep and entered a high-temperature environment during early Himalayan movement, which provided favorable conditions for crude oil cracking. The natural gas from highly matured gas reservoirs discovered in the Bachu-Maigaiti area may come from the cracked gas produced by over-matured kerogen that was generated in Cambrian source rocks during secondary hydrocarbon generation and the cracked gas from the crude oil generated in the paleo-reservoirs after deeply burial and temperature increasing in the Hetian paleo-uplift. Therefore, in the Bachu-Maigaiti area, the Cambrian source rocks, which had a relatively low evolution degree during the late Hercynian movement and are currently in the secondary hydrocarbon generation stage, and the paleo-reservoirs, which were at relatively low geothermal temperature in the early stage but recently have high-temperature cracking conditions, are important sources for natural gas accumulation. And the matching among secondary hydrocarbon generation, crude oil cracking product and new traps is the key to late hydrocarbon accumulation in the Bachu-Maigaiti area.

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Vertical Layered Structure of Shunbei No.5 Strike-Slip Fault Zone and Its Significance on Hydrocarbon Accumulation
HAN Jun, KUANG Anpeng, NENG Yuan, HUANG Cheng, LI Qiqi, CHEN Ping, SHEN Zhuoyi
2021, 42 (2):  152-160.  doi: 10.7657/XJPG20210204
Abstract ( 44 )   HTML ( 4 )   PDF (13579KB) ( 82 )  

As the largest strike-slip fault zone in Shunbei area, Shunbei No. 5 structure is vertically layered and deformed, and has been proved to play an important role in controlling fault-karst reservoirs. The study carried out the interpretation of 3D seismic data of the Shunbei No.5 strike-slip fault zone, analyzed its structure, and established vertical layered structure models to clarify the controsl of the strike-slip fault zone on reservoir development and hydrocarbon migration and accumulation. The results show that: (1)The Shunbei No.5 strike-slip fault zone can be divided into four layers in the vertical direction, namely a Cambrian sub-gypsum fault system, a Cambrian gypsum-related fault system, an Ordovician carbonate fault system, and an Ordovician-Carboniferous clastic fault system; (2)The difference between stratum mixing competence is the basic condition of the layered deformation, and the staged activities of strike-slip faults caused by the changes of regional tectonic movement is the primary reason for the layered deformation; (3)The vertical layered structure of the strike-slip fault zone controls the hydrocarbon migration and accumulation: the sub-gypsum faults control the distribution of source rocks, the faults penetrating gypsum interval control hydrocarbon migration, the faults inside the Ordovician carbonate rock control the scale and connectivity of reservoirs, and the faults inside the Late Ordovician-Carboniferous clastic rock control hydrocarbon accumulation. According to the strength of the strike-slip fault movement, the strike-slip fault zone can be classified into three categories such as strong activity and dominant superimposition, strong activity and differential superimposition, and weak activity and weak superimposition.

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Characteristics and Quantitative Prediction of Fractures of Tight Reservoir in Chang 7 Member in Longdong Area
SU Xiaocen, GONG Lei, GAO Shuai, ZHOU Xinping, WANG Zhaosheng, LIU Bo
2021, 42 (2):  161-167.  doi: 10.7657/XJPG20210205
Abstract ( 44 )   HTML ( 2 )   PDF (3650KB) ( 34 )  

In the tight reservoirs of the Chang 7 member in the Upper Triassic Yanchang formation in the Longdong area of the Ordos basin, fracture development is the primary factor affecting oil and gas distribution and well productivity. According to outcrop profiles, cores, casting thin slices and imaging logging data, the distribution of the fractures in the Chang 7 reservoir were characterized quantitatively, the controlling factors on the fracture development were clarified, and finally combining with rock mechanics and numerical simulations, the fracture distribution was quantitatively predicted. The study results show that in the Chang 7 reservoir in the study area, (a) large-angle structural fractures are developed, which are effective and poorly filled with mineral cements; (b) the average linear density of macroscopic fractures is 0.31 fracture/m, the average areal density and average porosity of microscopic fractures are 0.25-0.50 μm/μm2 and 0.32%, respectively, such fractures can increase reservoir spaces, connect the intergranular and intragranular pores, and enhance pore connectivity; (c) 4 groups of fractures were found, striking northeast-southwest, northwest-southeast, near east-west and near north-south respectively, and of which the fractures in northeast-south direction are the most developed; (d) the fractures are mainly developed inside the rock layer with powerful deformability and terminate at the lithological interface or bedding surface, 5 cm to 20 cm high, and up to 110 cm at the most; and (e) the higher the content of brittle minerals in the rock, the finer the particles, the denser the rock, and the thinner the formation, the higher the degree of fracture development. The distribution law of the fractures in the Chang 7 member in the Longdong area quantitatively predicted through finite element numerical simulation is consistent with the results from the actual measurement.

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RESERVOIR ENGINEERING
A New Method for Evaluating the Productivity of Oil Wells in Fault-Karst Reservoirs in Shunbei Oil & Gas Field
HU Wenge
2021, 42 (2):  168-172.  doi: 10.7657/XJPG20210206
Abstract ( 35 )   HTML ( 3 )   PDF (481KB) ( 37 )  

There are two problems in the understanding of oil well productivity in the high-productivity pilot block of fault-karst reservoirs in Shunbei oil & gas field: First, the formation pressure fluctuates obviously after well testing, so the conventional method for well test interpretation is no longer applicable; second, the productivity index curve determined based on well test data is nonlinear, so the oil production index method is unsuitable for quantitatively evaluating the oil well productivity. In order to realize quantitative evaluation of the productivity of the oil wells in Shunbei oil & gas field, based on the correction to well test data for estimating the fluctuating productivity in the systematic well test stage, we proposed a new method for evaluating the productivity of the oil wells, which includes exponential productivity equation, comprehensive oil production index, and productivity division standard. Field application has proved the systematic well test data correction method and the productivity evaluation method are suitable for quantitatively evaluating the productivity of the oil wells in Shunbei oil & gas field, which provide a theoretical basis for the quantitative understanding of the productivity of the oil wells in Shunbei oil & gas field.

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Occurrence Law of Remaining Oil in Heavy Oil Reservoirs With Strong Edge and Bottom Water in Taiping Oilfield
WU Wei, ZHANG Bo
2021, 42 (2):  173-178.  doi: 10.7657/XJPG20210207
Abstract ( 28 )   HTML ( 3 )   PDF (1361KB) ( 24 )  

Reservoirs in the lower member of the Neogene Guantao formation in the Taiping oilfield have strong and active edge and bottom water, so that water invasion is severe, the reserves producing degree and the recovery percent of reserves are low and there is a large amount of remaining oil, which should be produced by adjusting the development pattern. According to the development pattern and the occurrence law of the remaining oil, infill horizontal wells were located to change the flow field, large water channels were plugged, and cold production and viscosity reduction technologies were applied to enhance the oil recovery. Finally, the oil production has been increased, and the development cost of the heavy oil has been reduced significantly. The supporting technology developed during producing the heavy oil reservoirs in the lower member of the Neogene Guantao formation in the Taiping oilfield can be a reference to developing similar heavy oil reservoirs with strong edge and bottom water.

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Establishment and Application of a New Analytical Fractional Flow Equation
GAO Wenjun, YIN Rui, GAO Neng, SHENG Han, GAO Zhijiang
2021, 42 (2):  179-187.  doi: 10.7657/XJPG20210208
Abstract ( 26 )   HTML ( 2 )   PDF (701KB) ( 23 )  

On the basis of determining the new generalized water flooding characteristic curves, by using reverse reasoning methods, the water flooding characteristic curves can be inverted into the laws of water cut variation, and then combined with the Welge equation, the analytical fractional flow equation when water drives oil can be derived. The new fractional flow equation is a transcendental equation, and under certain conditions, it can be simplified to the results of typical oil-water two-phase seepage experiment. If the new analytical fractional equation is combined with the Levinlet function, the relation of oil-water permeability ratio that characterizes the two-phase seepage characteristics can be obtained. The water-flooding experimental data from 4 different types of reservoirs were used to perform fitting, the results showed that the fitting degree of the new equation was high, and the fitting effects were satisfactory. Furthermore, the laws of water cut variation corresponding to the new equation can not only describe the relationship between convex-shaped recovery degree and water cut, but also can describe the correlation between S-shaped, concave-shaped recovery degree and water cut. Taking the reservoirs in Xishanyao formation of Baka oilfield as an example, the analytical fractional flow equation of actual water displacing oil was given by using production data.

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Influences of Microstructural Differences on Acid Corrosive Damage to Carbonate Rocks
LI Xinyong, WU Hengchuan, FANG Haoqing, LI Yongshou, MAO Haijun, HUANG Luyun
2021, 42 (2):  188-193.  doi: 10.7657/XJPG20210209
Abstract ( 23 )   HTML ( 1 )   PDF (2579KB) ( 19 )  

Experiments on acid-rock reaction rate, surface static corrosion and point-load mechanical strength were carried out to investigate the influences of mineral composition, microstructure and distribution of carbonate rock on acid-rock reaction rate, microstructure and mechanical strength. The results show that, at a constant mass fraction of HCL, the reaction rate between limestone and HCL is directly related to the carbonate content. The higher the carbonate content is, the faster the acid-rock reaction rate and the more intense the reaction will be. Since there are differences in the mineral compositions between the matrix in the fracture zone and the fillings in the fractures, the porosity of the matrix is quite different from that of the fractures, so that acid would erode the mineral compositions along the fractures, resulting in grooves. The damages to the matrix of limestone by acid can induce fractures and extend to natural fractures, and consequently local damage occurs. With the increase of the times of acid dropping, the mechanical damage coefficient of the matrix in limestone would be greater than that of the fracture zone, and the limestone matrix transforms from brittle to ductile.

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Theoretical Model of Pore Compressibility for Fault-Karst Reservoirs in Shunbei Oilfield
LI Dongmei, LI Huihui, ZHU Suyang, LI Chuanliang
2021, 42 (2):  194-200.  doi: 10.7657/XJPG20210210
Abstract ( 21 )   HTML ( 3 )   PDF (1063KB) ( 16 )  

Pore compressibility is an important parameter for calculating dynamic reserves and elastic energy of oil reservoirs. For fault-karst reservoirs with complex reservoir spaces, it is difficult to estimate the pore compressibility through core experiments. Taking Shunbei oilfield as a case, we derived a compressibility model of fractures from the perspectives of filled continuous media and filled discrete media, and finally established a pore compressibility model of the fault-karst reservoirs through porosity weighting. The research results show that the pore compressibility of fractured media is related to the surface porosity of the fracture, and the Young’s modulus and Poisson’s ratio of the fracture fillings. The larger the surface porosity and Poisson’s ratio, the greater the fracture’s pore compressibility. The pore compressibility of fault-karst reservoirs falls in between the compressibility of the karst caves and that of the fractures, and is closer to the compressibility of the karst caves. The pore compressibility of fault-karst reservoirs calculated with conventional methods underestimates the dynamic reserves of the reservoir.

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Characteristics and Damage Prevention of Fault-Karst Reservoirs in Shunbei Oilfield
FANG Junwei, DONG Xiaoqiang, LI Xiong, ZHANG Guo, WU Xiongjun
2021, 42 (2):  201-205.  doi: 10.7657/XJPG20210211
Abstract ( 21 )   HTML ( 2 )   PDF (528KB) ( 16 )  

The reservoirs in Shunbei oilfield are characterized by deep burial depth, developed fractures and strong heterogeneity. In order to ensure the safety of drilling, drilling operation at positive pressure difference is usually followed, however, the high-density drilling fluid used may damage the reservoir. After analyzing the lithology, reservoir space, surface wettability, sensitivity, rock mechanical characteristics and the drilling fluid system used in the reservoir interval, it’s found that the damage of the drilling fluid to the reservoir is mainly reflected in such aspects as a large amount of solid phase with low acid solubility invading the reservoir and blocking the fractures, large capillary force causing aqueous phase trapping and water lock in the gas layer, and the drilling fluid with poor temperature resistance causing settlement and excessively high positive pressure difference. In view of the tight matrix and strong heterogeneity of the reservoir in Shunbei Block 1, preventive measures to reduce reservoir damage are proposed, namely “physical plugging-filtrate surfactant control, and hydration inhibition-mechanical approximate balance”, to reduce fluid loss, decrease solid-phase invasion and depth, improve the plugging performance while drilling, and protect the reservoir.

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Meshless Method-Based Numerical Simulation of Microbial Flooding
CAO Lin, XIU Jianlong, HUANG Lixin, HUANG Feng, XU Yunfeng, ZHAO Hui, SHENG Guanglong
2021, 42 (2):  206-212.  doi: 10.7657/XJPG20210212
Abstract ( 27 )   HTML ( 3 )   PDF (646KB) ( 16 )  

With advantages such as low cost, easy operation and friendly to environment, microbial flooding has become an EOR technology attracting more attention. The mechanism of microbial flooding is relatively complicated. The commonly-used numerical calculation methods such as finite difference and finite element are ineffective and their accuracy is greatly affected by meshing. Based on the weighted least square method, a meshless method was used for numerical simulation of microbial flooding, and the results of the meshless method were compared with those of the traditional finite difference method. The results show that the meshless method can increase the calculating efficiency by 62% while ensuring the same accuracy. In addition, the analysis to the stability of the meshless method indicates that there exist some influences of key parameters, such as density and influence domain of the mesh points and weight function on the simulation result and its accuracy. In a square reservoir area with a side of 100 m long, if a 9×9 uniform points pattern is used, the influence domain is a circle defined on the radius which is 3 times the point spacing, and a GAUSS weight function formula is used, the maximum calculating efficiency can be achieved while ensuring the calculating accuracy by using the meshless method. The numerical simulation of microbial flooding using the meshless method is effective and flexible in analyzing the mechanism of microbial flooding.

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Constructing Optimum Injection-Production Well Pattern for Fault-Karst Reservoirs
LI Qing, LI Xiaobo, TAN Tao, SONG Zhengcong, ZHANG Jie, LIU Hongguang
2021, 42 (2):  213-217.  doi: 10.7657/XJPG20210213
Abstract ( 25 )   HTML ( 3 )   PDF (1823KB) ( 22 )  

In order to construct the optimum injection-production well pattern suitable for fracture-cavity and fault-karst carbonate reservoirs, increase the control and producing degree of reserves by waterflooding development, and improve waterflooding efficiency, a typical combined pattern of fractures and cavities was proposed, and a conceptual model was established according to the development and distribution of fracture-cavity reservoir, fracture connectivity and oil and water distribution in Tahe oilfield. Based on the conceptual model, a numerical model that can reflect the fault-karst reservoirs was established by using numerical simulation software. Considering the strong lateral and vertical heterogeneity of the reservoirs, the studies on optimizing the injection-production well pattern for fault-karst reservoirs were carried out, and a well pattern optimization plan was designed, namely “injection and production at different positions on the lateral profile, and injection and production at different depths on the vertical profile”. Finally, the optimal well pattern suitable for the fracture-cavity and fault-karst reservoirs was obtained. The result shows that on the lateral profile, for the belt-shaped fracture-cavity unit which is crushed to a certain width, the best oil production effect can be achieved in the central position if injecting water from both side wings at the same time; for the plate-shaped fracture-cavity unit crushed to a narrow width, a linear well pattern is more effective, and the development effect is better when injection wells are located in the middle of the fault zone than at both ends. Vertically, the model of deep injection and shallow production is more conducive to waterflooding development of the fault-karst reservoirs.

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Experiment on Nanoparticle Active Oil Water Plugging Agent in Tahe Gas Field
YANG Liping, GE Jijiang, SUN Xiangyu
2021, 42 (2):  218-223.  doi: 10.7657/XJPG20210214
Abstract ( 23 )   HTML ( 2 )   PDF (1558KB) ( 16 )  

The gel was used in Tahe gas field to plug water in the early production stage and a significant effect was obtained in vertical wells, but it could not meet long-term water control requirements for horizontal wells. Aiming at the water plugging characteristics in horizontal wells, a nanoparticle active-oil water plugging agent was developed, which was composed of nanoparticles, emulsifier imidazoline and diesel. The water plugging agent is easy to be injected, and can form a kind of water-in-oil emulsion due to micro shear force of the formation water. The viscosity of the water-in-oil emulsion will increase under the action of high temperature and nanoparticles. The Jamin effect of the emulsion prevents the formation water from entering highly permeable channels, thereby reducing the water production rate. In the low-permeability channels, the nanoparticles in the system change the wettability of the reservoir to release the water lock of the channels. The emulsion will be diluted by condensate oil, so it will not block the gas channels. Laboratory evaluations show that the system has good selective water control capabilities with strong erosion resistance and a maximum residual resistance coefficient of 27, which can reduce the water production rate and restore gas production in gas wells.

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Mechanism of Enhanced Gas Recovery in Shale Gas Reservoirs Based on Competitive Adsorption
SUN Ying, SUN Renyuan, LIU Xiaoqiang, LI Shuxia
2021, 42 (2):  224-231.  doi: 10.7657/XJPG20210215
Abstract ( 25 )   HTML ( 1 )   PDF (652KB) ( 22 )  

In order to study the mechanism of injecting CO2 to increase the recovery of shale gas reservoirs and determine reasonable injection parameters, the experimental results of the production of shale gas reservoir developed by natural pressure drop and by injecting CO2 at different pressure and rates were compared based on shale adsorption and desorption experiments, and the changes in CH4 production rate and recovery factor under the two methods were studied. The results show that under the same experimental conditions, as to adsorption capacity, CO2 is the strongest, followed by CH4, and then N2, while as to desorption capacity, N2 is the strongest, followed by CH4, and then CO2. Compared with the isothermal adsorption curves, the isothermal desorption curves of the three kinds of gas are hysteretic to a certain extent, and the hysteresis of CO2 is the most obvious. The recovery factor of shale reservoirs developed by natural pressure drop is low, while CO2 injection can effectively increase the production rate of CH4, greatly prolong stable production and increase cumulative gas production. Within certain ranges of injection pressure and injection rate, the CH4 recovery increases with the increase of CO2 injection pressure and injection rate, but the increment varies with core porosity and permeability.

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APPLICATION OF TECHNOLOGY
Quantitative Characterization of Fractured-Vuggy Carbonate Reservoirs
DENG Guangxiao, HU Wenge, WANG Zhen
2021, 42 (2):  232-237.  doi: 10.7657/XJPG20210216
Abstract ( 30 )   HTML ( 2 )   PDF (1910KB) ( 39 )  

The Ordovician carbonate reservoirs in the north of Tarim basin are fractured and vuggy. On seismic sections, the seismic responses of the fractured-vuggy reservoirs are mostly “bead-like” strong reflections and chaotic reflections. We designed different fracture-vug models, compared the seismic response characteristics with the heights and external shapes of the fractures and vugs in the fracture-vug models, and quantitatively characterized the fractures and vugs on various scales based on the results calculated from the seismic resolution theory formula. The results are that: the external shape of the fractures and vugs more than 50 m high can be quantitatively described, and their volumes can be calculated with high reliability; the volume, center points and roofs of fractures and vugs of 10-50 m high can be identified, semi-quantitative identification and accurate calculation of their volumes can be carried out with average reliability; and the fractures and vugs less than 10 m high can only be qualitatively predicted on their lateral and vertical distribution, and the reliability of volume calculation is low. After characterization and quantitative calculation using seismic attributes on various scales, the multiplicity of quantitative characterization of fractures and vugs is effectively reduced. The results provide basic data for target evaluation and well location optimization.

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Seismic Identification and Description of Ultra-Deep Fault-Controlled Reservoirs in Shunbei Area
LIU Jun, LI Wei, GONG Wei, HUANG Chao
2021, 42 (2):  238-245.  doi: 10.7657/XJPG20210217
Abstract ( 26 )   HTML ( 2 )   PDF (7106KB) ( 38 )  

Fault-controlled reservoirs in Shunbei area are deep in buried depth and complex in reservoir space. And their distribution is mainly controlled by deep and large strike-slip faults. So it is difficult to accurately describe their spatial position, volume and connectivity during exploration and development of the fault-karst reservoirs. According to the geological model of the strike-slip faults, and the types and seismic response characteristics of the fault-controlled reservoirs, we first establish seismic recognition patterns through forward modeling and well logging-seismic analysis for analyzing the sensitive seismic attributes of the reservoirs, and develop a series of technologies for predicting the outlines and interiors of the fault-controlled reservoirs. Then we characterize the outlines and interiors of the fault-controlled reservoirs based on the structural tensor, enhanced coherence, instantaneous energy and clutter attributes and phase-controlled wave impedance inversion. Finally, we provide the technology using seismic data to identify the ultra-deep fault-controlled reservoirs in Shunbei area.

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Seismic Imaging Technology for Deep Strike-Slip Faults in Carbonate Reservoirs
YANG Wei, ZHOU Gang, LI Haiying, MA Xuejun
2021, 42 (2):  246-252.  doi: 10.7657/XJPG20210218
Abstract ( 29 )   HTML ( 2 )   PDF (5409KB) ( 57 )  

Seismic wave reflected from the deeply buried Ordovician carbonate reservoirs in Shunbei area of Tarim basin is absorbed and attenuated seriously, and the energy of the seismic wave field diffracted from the deep strike-slip faults in the Ordovician-Cambrian formations is weak, making it difficult to get accurate seismic image. To improve the quality of seismic image, we analyzed the seismic responses characterized by low frequency and weak amplitude, then suppressed noises while protecting low-frequency signals and carried out wavelet consistency processing, and finally applied fault-controlled velocity modeling, tomographic velocity inversion and broadband inverse time migration imaging technologies to improve the seismic imaging quality of the deep strike-slip faults under the desert in the Shunbei area of Tarim basin. The result is helpful to reduce exploration risks and provides reliable data for trap implementation and well allocation.

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