23 August 2014, Volume 41 Issue 4
    

  • Select all
    |
    油气勘探
  • Dong Yuexia; Yang Shang; Chen Lei; Wang Qi and Cao Zhonghong
    , 2014, 41(4): 385-392.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Based on the core description, conventional thin section, cast thin section and scanning electron microscope (SEM) analysis, combined with the general physical analysis, the physical properties of the braided river delta sandstone reservoirs and the types of reservoir space of Sha 1 Member, Paleogene Shahejie Formation, have been analyzed in the southern Nanpu Sag of the Bohai Bay Basin. The characteristics and controlling factors of the southern provenance of Sha 1 reservoirs are examined to reveal the causes for the formation of deep high-quality reservoirs (more than 4 000 m). Sha 1 reservoirs in the study area are the gravel rock, pebbled inequigranular sandstone, medium sand, and gritrock. The lithology is mainly lithic feldspar sandstone, the contents of rigid particles like quartz and metamorphic rock cuttings are higher, the content of matrix is very low, the structure is particle support. The average porosity is 12.8%. The average permeability is 154.9×10-3 μm2. The reservoir type is low porosity and high permeability. The reservoir space is mainly primary pores and secondary pores. Parent rock type, sedimentary environment and the abnormal high pressure in the Sha 1 Member are the dominant factors controlling the reservoir properties. It is inferred that high quality sandstone reservoirs with high natural productivity of oil and gas are widely developed in the strata more than 4 000 m deep in the Bohai Bay Basin, the conventional sandstone reservoir exploration is expected to expand to the deep.
  • Guo Yanru; Fu Jinhua; Wei Xinshan; Xu Wanglin; Sun Liuyi; Liu Junbang; Zhao Zhenyu; Zhang Yueqiao; Gao Jianrong and Zhang Yanling
    , 2014, 41(4): 393-403.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    According to sedimentary environment, sources, hydrocarbon accumulation characteristics and gas reservoir types of the Ordovician in the Ordos Basin, the Ordovician carbonate rocks in the basin have good gas accumulation conditions. A large number of geological and geochemical evidence shows a triple source supply. In addition to the Upper Carboniferous - Permian coal measures hydrocarbon source rocks as the main hydrocarbon source rocks, the Middle-Upper Ordovician marine hydrocarbon source rocks and Carboniferous Benxi marlstones have certain ability for hydrocarbon. Analysis of the known gas reservoir reveals that the gas in the gas fields of the central basin belongs to thermal cracking gas which is a mixed gas of coal-derived gas and crude oil cracking gas. Coal-derived gas comes from the coal measures hydrocarbon source rocks of the Carboniferous-Permian undoubtedly. Crude oil cracking gas mainly comes from the high temperature cracking gas in the Jurassic reservoir. Asphalts and hydrocarbon inclusions in the Ordovician reservoirs evidence that the oil of the Jurassic paleo-oil reservoir is mainly from the Middle-Upper Ordovician marine hydrocarbon source rocks. Gas accumulation has evolved from oil reservoir to gas reservoir: oil pool formed in the Jurassic and the oil cracked into gas in the Cretaceous. Controlled by tectonic sedimentary setting, four accumulation models of carbonate gas reservoir have been structured. Among them, weathering crust lithostratigraphic gas reservoir in the central part of the basin and composite lithology gas reservoir of structure - bedding karst type in the northwest platform marginal zone are the focus of the carbonate gas exploration.
  • Song Jinmin; Luo Ping; Yang Shisheng; Yang Di; Zhou Chuanmin; Li Pengwei and Zhai Xiufen
    , 2014, 41(4): 404-413.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The microbial carbonate reservoirs of the upper part of the Lower Cambrian Xiaoerbulake Formation have been researched based on outcrop section and thin section identification in the Aksu area, Tarim Basin. The microbialites are composed of peloid, lamination, thrombolite, stromatolite, dendrolite, oncolite and spongiostromata. There develop three types of microbial carbonate reservoirs: microbial reef, coated thrombolite and spongiostromata stromatolite dolomite. Two stages of microbial reefs are developed on paleokarst high in the Late Sinian: the first one with southward progradation is constructed by the Epiphyton, while the second one with northward transgression by cyanobacteria clots. The dendrolites, thrombolites and stromatolites in the reefs are potential for hydrocarbon reservoirs, with needle-like dissolved pores, thickness of 40 to 70 meters, lower porosity and lower permeability. Coated thrombolites are located on the paleo-depositional slope, characterized by the isolated dissolved pores, thickness of 30 meters, lower porosity and lower permeability. Spongiostromata stromatolite beds lie in the paleo-depositional depression, with layered fenestrules well developed, 18 meters thick, lower to medium porosity and lower permeability. The development of the microbial carbonate reservoirs are controlled by depositional paleo-topography, diagenesis and microbial structures.
  • Yao Huifang; Kang Zhiqin and Li Wei
    , 2014, 41(4): 414-420.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Tectonic deformation and pore structure characteristics of tectonically deformed coals (TDC) collected from the Hancheng area, Weibei block, eastern Ordos Basin were characterized through scanning electron microscope, micro-CT, mercury porosimetry and low-temperature nitrogen adsorption experiments. The isothermal adsorption experiment of lumpy TDC was also performed to investigate the gas storage behavior. The results show that the primary layer structure can be observed in cataclastic coals and granulated coals. These coals show sub-angular particles of 1-3 cm. For scaled coals and mylonitic coals, the primary structure and coal bedding have been destroyed, and the coal is sheared with directional arrangement of grains. The pore volume, pore surface area, micro-pore volume and pore connectivity increase with the increase in deformation extent. The CH4 adsorption capacity of coals shows an increasing trend from brittle deformation to ductile deformation. It is concluded that the coal structure, pore and fracture characteristics of TDC control the gas adsorption capacity of coals.
  • Chen Shijia; Gao Xingjun; Wang Li; Lu Jungang; Liu Chaowei; Tang Haiping; Zhang Huanxu; Huang Youlin and Ni Shuai
    , 2014, 41(4): 421-427.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    By comprehensively analyzing oil-bearing and non-oil-bearing tight sandstone reservoir properties, pore structure characteristics and contact between source rock and reservoir, reservoir fluorescent photographs of typical wells of Jurassic Lianggaoshan Formation in central Sichuan Basin, the research tries to find out factors controlling the oiliness of the Jurassic Lianggaoshan tight sandstone reservoir. The oiliness of the Jurassic Lianggaoshan tight sandstone reservoir in central Sichuan Basin is controlled by the following factors: (1) The migration pathway between the source rock and reservoir: when there exist sandstone and mudstone transition zones with high mud content and poor physical property between the source rock and reservoir, without fracture connection, it is difficult for oil and gas to migrate into the overlying reservoir; (2) The reservoir physical property: if the reservoir contacts directly with source rock and has good physical properties, oil and gas can migrate and accumulate directly in the reservoir. (3) Development degree of fractures: when the reservoir physical properties are poor, rich fractures can improve porosity and permeability of the reservoir, oil and gas can still migrate and accumulate in the reservoir; if the reservoir physical property is poor and no fractures developed, oil and gas are difficult to migrate and accumulate in the reservoir. Based on the sedimentary and reservoir characteristics of Jurassic Lianggaoshan Formation in central Sichuan Basin and the distribution of source rocks, Yingshan-Guang’an and Hechuan-Baimiao-Luodu two favorable exploration zones are selected.
  • Han Rubing; Liu Qiang; Jiang Tongwen; Xu Huaimin; Xu Zhaohui; Zhao Lei; Lei Cheng and Zhang Pengcheng
    , 2014, 41(4): 428-437.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The petrologic characteristics, well-logging, genetic models and distribution patterns of calcareous inter-layers in Carboniferous Donghe sandstone, Hade Oil Field were investigated systematically by using data such as outcrop, cores, thin sections, stable carbon and oxygen isotopic compositions, conventional logging curves, and dip logging curves. Calcareous inter-layers in the study area are made up of calcareous fine sandstone or calcareous siltstone of high compositional and textural maturity, in which calcareous components include calcite, ferro-calcite, dolomite, ferro-dolomite and anhydrate. Although the calcareous inter-layers are usually thin, they can be identified by combining conventional logging curves with dip logging curves. Three genetic models of calcareous inter-layers are identified, including shallow burial fresh water, evaporation and deep burial. According to the development of sedimentary facies, it is inferred that calcareous interlayers are well-developed in shore face and backshore sandstones, and likely to join together and show continuity between wells; based on features of high-resolution sequence stratigraphy, it is concluded calcareous inter-layers in Donghe sandstone have five types of occurrence: “upper calcareous–lower argillaceous” type, “upper argillaceous–lower calcareous” type, “calcareous-argillaceous– calcareous” type, purely calcareous type and “calcareous–argillaceous complex” type.
  • Zhao Xiaodong; Yang Shaochun; Xiang Kui; Chen Guoning; Zhu Chunyan and Wei Xiaoqing
    , 2014, 41(4): 438-444.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Based on fluid property and distribution, the reason for oil-water inversion at top and bottom of the shallow sandstone reservoir of the Neogene Shawan Formation in the Northern Chepaizi area, Junggar Basin was researched from the perspective of structure, lithology, carbonate cementation and oil thickening. The oil of Northern Chepaizi area is heavy crude oil, whose density and viscosity increase with the depth of oil layer. Carbonate cementation and oil thickening are the controlling factors of oil-water inversion at both top and bottom. When the top surface of oil layer in downthrown side is deeper than a definite depth, the density of crude oil, due to oil thickening, is closer to or higher than that of the formation water, and oil-water inversion at the bottom of reservoir occurs. In the structural high part, carbonate cementation deteriorates the reservoir physical property, the late migrated oil has no access to the high position reservoir, and oil-water inversion forms in the structural high part. In the middle to upper area, conventional heavy oil accumulates, because it’s lighter than the formation water, oil and water differentiation is complete.
  • 油气田开发
  • Ning Zhengfu; Wang Bo; Yang Feng; Zeng Yan; Chen Jin’e and Zhang Lian
    , 2014, 41(4): 445-452.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Gas flow in nano-pores which are abundant in the organic matter of shale can lead to micro-scale effect that can’t be described by flowing law of macro fluid. The Lattice Boltzmann Method was applied to simulate gas flow in the nano-channels of organic matter and to investigate the slippage effect, diffusion effect and adsorption/desorption effect. The simulation result shows that the compressibility effect of gas leads to the nonlinear pressure distribution along the channels, and the larger the pressure difference, the more serious the nonlinear distribution. To some extent, the enhancement of rarefaction effect weakens nonlinear degree caused by the compressibility effect. With the increase of Knudsen number and the pressure differential on the two ends, the slip velocity on the boundary increases, and the velocity vertical to the channel is not zero, increasing the exchange of kinetic energy between gas molecules in channels and molecules at boundary. Slippage effect and adsorption/desorption effect have a significant contribution to the gas mass flow in nano-channels of organic matter.
  • Wang Hui; Zhang Peijun; Cheng Youyou; Leng Youheng; Guo Chunqiu; Shi Haidong; Wei Zhanjun; Liu Lingli; Shi Liyong; Cheng Muwei and Xiang Hongying
    , 2014, 41(4): 453-456.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    In view of the long pressure stabilization time of low permeability gas reservoirs, the traditional backpressure test was modified based on the idea of isochronal test in order to evaluate gas well productivity accurately. Firstly, carry out continuous well startup using 3-4 incremental working systems at the same time interval without the bottom-hole flowing pressure reaching stability; then carry out a prolonged test using a reasonable working system which requires both the bottom-hole flowing pressure and the production reaching stability; finally shut in the well to allow the pressure recover to formation pressure. If the isochronal test productivity calculation method is borrowed for the modified backpressure test, the drawdown pressure will be overestimated, and calculated productivity will be underestimated. The process conversion-flowing pressure correction was used to convert the test process into an isochronal test process, and the bottom-hole flowing pressure correction equation was deduced based on pressure superposition principle to solve the productivity calculation problem with this method. The example indicates that the modified backpressure test method can not only shorten the test time significantly and avoid frequent well startup and shut-in, but also can ensure the accuracy of productivity calculation.
  • Li Longlong; Yao Jun; Li Yang; Wu Minglu; Zeng Qingdong and Lu Ranran
    , 2014, 41(4): 457-461.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Applying the potential theory and the superposition principle, the authors derived the linear productivity equations of staged multi-cluster fractured horizontal well considering finite and infinite conductivity fractures, respectively. The cluster yields and total yield were obtained by solving these equations numerically. A concrete example is used to analyze the productivity distribution of the fractured horizontal well and the influence of fracture parameters on it. When the fracture conductivities are infinite, the total productivity decreases significantly with the decrease of all fractures’ half-lengths; outer fractures near the endpoints of the horizontal wells contribute most to the total productivity, and fractures on the edges contribute more than the middle ones within the same stage. When the fracture conductivities are finite, the contribution of outer fractures near the endpoints of the horizontal wells to the total productivity decreases, and the contribution of middle fractures within each stage increases significantly, but the overall distribution characteristics are in accord with the former case. Fracture conductivities have a great influence on the productivity, but they are not linearly correlated. Three stages and two clusters per stage can ensure high productivity, and during fracturing design, one should try to increase fracture half-lengths and fracture conductivities, especially for outer fractures near the endpoints of the horizontal well, and there exists an optimal value for the fracture conductivities.
  • Jiang Bin; Qiu Ling; Li Xue; Yang Shenglai; Li Ke and Chen Han
    , 2014, 41(4): 462-465.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    To solve the problem that wax appearance temperature (WAT) acquired by conventional method is not suitable and effective to the subsurface live crude oil and dark oil, a way to measure the WAT of crude oil varying in properties is explored using the characteristics of ultrasonic transmission through media. In WAT measurement with ultrasonic, as the temperature of crude dropped, solid wax crystallized from the crude, the decline effect of crude oil to ultrasonic would be strengthened during the measurement by ultrasonic. The head wave frequency changed during the process; the frequency turning point was the wax precipitation point that could be obtained through segmental fitting of temperature and main frequency. This method was adopted to attain the WAT of the live oil at the reservoir condition and stock tank oil with high pour point and the results indicate that this method is reliable and not restricted by the color of oil. With the decrease of pressure, the WATs of live oil and dead oil both reduce, the WAT of live oil is 8 ℃ lower than that of dead oil under the same pressure. The WAT of live oil at the reservoir pressure measured by ultrasonic is about 3.7 ℃ lower than that of the stock tank oil measured by conventional method.
  • 石油工程
  • Liu He; Wang Feng; Zhang Jin; Meng Siwei and Duan Yongwei
    , 2014, 41(4): 466-472.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Stimulation principles, construction techniques, equipment requirements and technical features of liquid carbon dioxide fracturing were summarized, and the existing problems and development trend of this technology were discussed. Compared with the conventional hydraulic fracturing technology, it has several advantages including high flowback, small damage in reservoir, outstanding stimulation effect and so on. There are five main problems existing in this technology: friction of liquid carbon dioxide is very high; liquid carbon dioxide has an extremely low viscosity, poor proppant carrying ability and a large amount of fluid loss, thus behaves poorly in fracturing; the phase behavior of carbon dioxide is very complex in the process of fracturing, it is hard to realize accurate prediction and control for phase transition of carbon dioxide; fracturing equipments, especially blenders have obvious defects and should be improved further; computational methods for operation parameters in liquid carbon dioxide fracturing is still lacking. Supercritical carbon dioxide fracturing technology succeeds almost all the advantages of traditional liquid carbon dioxide fracturing technology, and has a better stimulation effect, smaller pump pressure and fewer requirements for blenders, thus is the trend in carbon dioxide fracturing.
  • Kang Yili; Xu Chengyuan; Tang Long; Li Song and Li Daqi
    , 2014, 41(4): 473-479.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    According to the mechanism analysis of drilling fluid loss in the formation with low pressure-bearing capacity, three basic theories, including stress cage, plugged zone, and strength ring for wellbore strengthening, were summarized and the corresponding models were established. The application conditions for the three theories and their requirements on the material properties were determined based on the models. Fracture propagation, filtration effect of drilling fluid and depleted formation pressure are the major factors that lead to low formation pressure-bearing capacity. The stress cage theory strengthens the wellbore by establishing the balance between wellbore pressure and formation stress. It is applied in the formation with low-development fracture. It demands that the material has enough compressive strength and reasonable size distribution to sustain certain fracture width and low fracture pressure. The plugged zone theory works by establishing the balance between wellbore pressure and formation pressure. It is suitable in pore an fractured formation and demands that the plugging material has the properties of high surface friction coefficient, resilient deformation, volume fraction and strength to create the synergy effect of rigid granule, fiber and resilient particle. The strength ring theory applies to fracture-vug formation and it requires that the material can cement the weak structural plane or form a high strength body to separate the pressure propagation from wellbore to formation. The effect and guiding significance of the three theories were further confirmed by field applications.
  • Tang Ligen; Wang Jieming; Bai Fengjuan and Shi Lei
    , 2014, 41(4): 480-484.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    In view of the gap between the gas storage inventory forecasted by the traditional material balance equation and the actual inventory, experiments of displacing gas by water and displacing water by gas were carried out, and the modified material balance equation considering pore volume loss due to water invasion and pay heterogeneity was deduced based on the percolation mechanism inferred from the experiments above, moreover the equation was verified by example analysis. The experimental results show that: the irreducible water saturation and residual gas saturation in underground gas storage (UGS) domain should be evaluated through water-gas seepage experiments because these parameters are different from the process of gas field development; the pore volume in the water flooded reservoir decreases after conversion for gas storage, and the pore volume loss increases rapidly when the reservoir permeability decreases. The net pay was divided into flooded zone, transitional zone and gas zone with the equations for pore volume loss cacaulating due to water flooded. Then one parameter describing reservoir heterogeneity was defined based on numerical simulation and eventually the traditional material balance equation was modified with the consideration of pore volume loss due to water invasion and reservoir heterogeneity. Example analysis result shows that the actual UGS inventory differs greatly from the inventory predicted by the traditional materal balance equation, but agrees with that calculated by the modified one.
  • Gao Ke; Li Meng; Dong Bo; Sun Youhong; Sun Yang and Liu Jing
    , 2014, 41(4): 485-489.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Bionic coupling polycrystalline diamond compact (PDC) was designed according to the biological coupling theory, its performance was evaluated by wear resistance experiment, and then the bionic coupling PDC bit was made and used in field drilling test. The design of the bionic coupling PDC was based on natural models (e.g. shell, mole cricket, human teeth, bamboo and tree annual ring) and started with materials of polycrystalline diamond and carbides, polycrystalline diamond-carbides interface and polycrystalline diamond non-smoothed surface. The wear resistance experiment results show that: the bionic coupling PDC performs higher drilling speed and better wear-resistance than the conventional PDC of the same size, the abrasion ratio is increased by 18.4% and the wheel wear rate is improved by 167%. In field drilling test, the bionic coupling PDC bit was designed according to stratum and depth and compared with the conventional PDC bit used in nearby wells. The mechanical drilling speed of the bionic coupling PDC bit is 2.5 times that of the conventional PDC bit, so the bionic coupling PDC bit can reduce drilling cycle and decrease drilling cost greatly.
  • Li Jiancheng; Yang Peng; Guan Jian; Sun Yande and Kuang Xubing
    , 2014, 41(4): 490-496.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    To meet the demand of ultra deep well drilling and shale gas well drilling, organic clay and a oil-based filtrate reducer were developed and a whole oil-based drilling fluid formula was optimized. The performance of organic clay, oil-based filtrate reducer and the whole oil-based drilling fluid were evaluated in laboratory, and the whole oil-based drilling fluid was applied in drilling process for further test of its performance. Long carbon chain quaternary ammonium salt was used as modifying agents when synthesizing organobentonites. Oil-based filtrate reducer was synthesized with monomers of lignite and amine class. The laboratory tests show that the organic clay can effectively increase the viscosity of oil-based drilling fluid and the oil-based filtrate reducer can reduce the fluid loss. Their performances were better than additives of the same kind at home and abroad. The organic clay and oil-based filtrate reducer had great compatibility with the other additives in oil-based drilling fluid. Based on the optimal additives addition amount tests, the whole oil-based drilling fluid formula was determined and the test results show that the performances of the whole oil-based drilling fluids with various densities were great. The laboratory tests show that the oil-based drilling fluid developed was high temperature resistant, even at 200 ℃, as density varies from 0.90 to 2.0 g/cm3, it still held good performance with only a little fluid loss, good inhibition, great anti-pollution, and good reservoir protection performance. Field application result shows that the performance of the oil-based drilling fluid is stable with great ability to maintain wellbore stability and lower density than the water-based drilling fluid; drilling bits can be used much longer and the average penetration rate is increased; the oil-based drilling fluid can satisfy the drilling requirements.
  • 综合研究
  • Lu Baoliang; Wang Pujun; Wu Jingfu; Li Wuzhi; Wang Wanyin and Lang Yuanqiang
    , 2014, 41(4): 497-503.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Based on 40 wells encountering the Mesozoic sedimentary rocks, 52 thousands kilometers of seismic profiles covering most parts of the South China Sea (SCS) and the latest collection of gravity and magnetic data, the distribution of the Mesozoic in the continental margin of South China Sea and the oil and gas exploration prospect are studied. The Mesozoic is distributed in three main areas in the SCS: (1) the area of eastern Pearl River Mouth Basin and Southwest Taiwan Basin, where the Mesozoic buried at 1-3 km deep and 2-8 km thick, is thickest in the Chaoshan Depression and east Dongsha Uplift, and there is a long axis gentle fold in the east of the Pearl River Mouth Basin; (2) Liyue-Palawan Basin area, where the Mesozoic, 2-4 km deep and 2-5 km thick, is thickest in the south depression of the Liyue Basin; (3) Zhongjiannan-Wan’an-western Nanwei Basin area, where the Mesozoic is 3-5 km deep and 2-3 km thick. According to the spatial location relationship between the Mesozoic distribution and deep faults, it is inferred that the Mesozoic distribution is controlled by the eastern Yangjiang-Yitong Shoal fault, Balabac fault and YueDong-Wan’an fault, and affected by the uneven base uplifting and block faulting caused by the Mesozoic Pacific plate subduction to the East Asian continent. The study on the distribution of residual Mesozoic strata, structural traps and source rocks concludes that there are two favorable areas for the Mesozoic hydrocarbon exploration, namely, Chaoshan Depression and Dongsha Uplift in the east of Pearl River Mouth Basin, and south depression in the Liyue Basin. However, the exploration prospect of the Zhongjiannan-Wan’an-western Nanwei Basin area needs further investigation.
  • 学术讨论
  • Tang Hao; Tan Xiucheng; Liu Hong; Zhou Yan; Li Ling; Ding Xiong; Tang Qingsong and Zou Juan
    , 2014, 41(4): 504-512.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Taking the B bed of the second submember of the second member of Triassic Jialingjiang Formation in Moxi gas field as an example, the basic characteristics and controlling factors of the “Khali” powder dolomite reservoir is analyzed systematically, and the genesis and forming mechanism of the powder crystal dolomite are examined. Logging and core analysis show that the reservoir has intercrystalline pores and intercrystalline dissolved pores as the main storage space, mainly lamellar throats, good configuration between pores and throats, and medium porosity and low permeability, representing typical porous-type reservoir. Dolomitization genesis analysis indicates that dolomitization occurred in the early diagenetic stage, with obvious spatial evolution pattern, the degree of dolomitization decreases gradually from top to bottom, and decreases with the increase of distance from the source of brine horizontally; over-dolomitization occurs in the study area, the petrophysical property of dolomite close to the source of brine is worse than the dolomite formed by seepage-reflux far from the source of brine, which suggests the “Khali” powder crystal dolomite is of seepage-reflux genesis. Reservoir genesis analysis shows that the intercrystal pores formed by seepage-reflux dolomitization acted as superior seepage channels for reservoir reformation later, and syndiagenetic karstification is the root cause of the formation of “Khali” powder crystal dolomite reservoir.