20 February 2017, Volume 44 Issue 1
    

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    PETROLEUM EXPLORATION
  • Breakthrough and significance of unconventional oil and gas to classical petroleum geological theory
    JIA Chengzao
    Petroleum Exploration and Development, 2017, 44(1): 1-11. https://doi.org/10.11698/PED.2017.01.01
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Great changes of the global energy industry have been caused by the rapid development of unconventional oil and gas. It is necessary to deeply consider the profound influence of the unconventional oil and gas revolution on the classical petroleum geological theory and to review geological conception of oil and gas accumulation elements and theoretic framework of petroleum system, giving the petroleum geology a new academic connotation. The author summarizes the significant progresses of global unconventional oil and gas exploration and development, and points out that the unconventional oil and gas revolution not only has a significant economic significance of oil and gas resource increment, but also brings great innovation to the theory of petroleum geology, thus having important scientific significances. This paper summarizes the core contents of four aspects of hydrocarbon generation, reservoir, distribution and development in classical petroleum geology, and comprehensively reviews the five important nodes in the developmental history of petroleum geology, which include anticline and trap theory, hydrocarbon generation from organic matter and petroleum system theory, continental petroleum geology, marine deepwater petroleum geology, continuous hydrocarbon accumulation and unconventional oil and gas geological theory. Unconventional oil and gas has made a great breakthrough to classical petroleum geology on the basic theoretical concepts such as trap, reservoir, caprock, resource distribution, and enrichment, thereby promoting the basic research on petroleum geology to transform into the whole process of hydrocarbon generation, whole type of reservoir, and whole genetic mechanism, deepening unconventional petroleum geology theory, promoting the development and reconstruction of petroleum geology system, representing great significances to the strategic development from conventional to unconventional oil and gas in China or even in the world.
  • Geological conditions for continental tight oil formation and the main controlling factors for the enrichment: A case of Chang 7 Member, Triassic Yanchang Formation, Ordos Basin, NW China
    YANG Hua, LIANG Xiaowei, NIU Xiaobing, FENG Shengbin, YOU Yuan
    Petroleum Exploration and Development, 2017, 44(1): 12-20. https://doi.org/10.11698/PED.2017.01.02
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    The Chang7 Member of the Triassic Yanchang Formation in the Ordos Basin is a typical continental tight oil province. The geological conditions and the main controlling factors for the formation of tight oil province in Chang 7 Member were studied based on extensive core analysis data, laboratory simulation tests and practical work of tight oil exploration and development in the basin. The tight oil in the Chang 7 Member is characterized by wide distribution, excellent source rock conditions, tight sandstone reservoirs, complicated pore-throat structure, poor physical properties, high oil saturation, high quality oil, and low pressure coefficient. During the depositional period of Chang7 Member, the bottom shape of the basin was steep at southwest and gentle at northeast, the tectonic movements were active, favorable for the deposition of source rock and reservoir; the widespread high quality source rock can provide sufficient oil supply for the large tight oil province; the large scale sand bodies provide good reservoir condition for the large tight oil province; the abundant structural fractures in the tight reservoir act as pathways for tight oil migration; and the stable deposition and tectonic evolution of the basin provide good preservation conditions for the tight oil province. The main controlling factors of Chang7 Member tight oil enrichment are as follows: (1) good configuration of source rock and reservoir and constant charging are the key to the formation of the tight oil province; (2) abundant micro-scale pores are the premise of tight oil enrichment; (3) strong and sustained charging guarantees the enrichment and high yield of oil in the tight reservoirs.
  • Types and distribution of the shale sedimentary facies of the Lower Cambrian in Upper Yangtze area, South China
    LIU Zhongbao, GAO Bo, ZHANG Yuying, DU Wei, FENG Dongjun, NIE Haikuan
    Petroleum Exploration and Development, 2017, 44(1): 21-31. https://doi.org/10.11698/PED.2017.01.03
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    Based on comprehensive analysis of outcrops, cores, rock thin sections, mineral X-ray diffraction and Argon ion-milling - scanning electron microscopy, nine lithofacies types and five facies marks in the Lower Cambrian Meishucun Formation and Qiongzhusi Formation in the Upper Yangtze are identified, a classification scheme of the shale sedimentary facies is proposed, and the deposition and evolution model of the shale in the Lower Cambrian is figured out. This research shows there are difference in sedimentation, types and distribution of the sedimentary facies in the Meishucun Formation and Qiongzhusi Formation. The main sedimentation modes in the Meishucun Stage were mechanical-chemical and biological sedimentation, the sedimentary facies (from west to east) were carbonate ramp, shelf, and slope and bathyal basin. The main sedimentation of the Qiongzhusi Stage was clastic mechanical, argillaceous flocculation and biological deposition, and the sedimentary facies were shore, shelf, and ramp and bathyal basin. There are two depositional centers of rich organic shale in the Upper Yangtze which are the prospective area for shale gas exploration. The first one is in the Ziyang-Changning area in nearly north-south strike, which is characterized by multiple thin layers. The other one is in the Western Hubei-Eastern Chongqing-Middle Guizhou and Yichang-Jianshi-Fangxian, which is characterized by the thick-layer shale. The shale gas exploration in these areas in the future should take pertinent strategies in line with their differences.
  • Significance of source rock heterogeneities: A case study of Mesoproterozoic Xiamaling Formation shale in North China
    WANG Xiaomei, ZHANG Shuichang, WANG Huajian, SU Jin, HE Kun, WANG Yu, WANG Xiaoqi
    Petroleum Exploration and Development, 2017, 44(1): 32-39. https://doi.org/10.11698/PED.2017.01.04
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    Taking Mesoproterozoic Xiamaling Formation, Northern China as an example, the heterogeneities of source rock in different scales and hydrocarbon microscopic occurrence are studied based on observation of outcrops and observation with microscopy, and geochemical analysis. The large scale heterogeneities of source rocks are considered to be controlled by the plate movement and paleo-latitude location, while the micro-scale might be controlled by climate changes driven by the astronomical orbit. The constant existence of heterogeneities includes the differences of organic matter, debris sources and porosities. The heterogeneities of source rock should be seriously treated during the evaluation of oil and gas resources, especially the unconventional oil and gas. This kind of heterogeneous source rocks provides excellent source-reservoir assemblage of oil and gas generation, expulsion and accumulation, and new reference indexes for the economic evaluation of unconventional oil and gas. Therefore, quantitative study of the heterogeneity of source rock is of great significance for investigating formation mechanism and resource estimation of unconventional oil and gas.
  • Origin and differential accumulation of hydrocarbons in Cambrian sub-salt dolomite reservoirs in Zhongshen Area, Tarim Basin, NW China
    ZHANG Jizhi, WANG Zhaoming, YANG Haijun, XU Zhiming, XIAO Zhongyao, LI Zhongxuan
    Petroleum Exploration and Development, 2017, 44(1): 40-47. https://doi.org/10.11698/PED.2017.01.05
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    The origin and differential accumulation of hydrocarbons in the Cambrian sub-salt dolomite reservoirs in Zhongshen Area were studied based on comprehensive geochemical analysis of core samples, crude oil samples and natural gas samples. Mass spectrometric detection shows the core samples and crude oil samples are characterized by high C28 sterane content, low diasterane content, high gammacerane content and abundant aryl-Isoprenoids, and the associated gas has a low nitrogen content of 0.24%-4.02%, so it is inferred that the oil and gas are derived from Cambrian - Lower Ordovician source rock. The natural gas in the Middle Cambrian has a methane carbon isotope value of -51.4‰ - -44.7‰ and dryness coefficient of 0.65-0.78, representing associated gas, and the natural gas in the Lower Cambrian has a methane carbon isotope value of -41.4‰ - -40.6‰, and dryness coefficient of 0.99, representing cracking gas. The deep formations in the Tarim Basin contain cracking gas with high H2S content produced by thermo-chemical sulfate reduction (TSR). Due to the poorer reservoir properties and undeveloped fracture network system, the Middle Cambrian reservoirs have low charging degree of this kind of gas, so low H2S content (0.003 8%-0.200 0%); in contrast, with good reservoir properties and developed fracture network system, the Lower Cambrian reservoirs have a higher charging degree of this kind of gas, and thus high H2S content of 3.25%-8.20%. In summary, the oil and gas of Cambrian sub-salt dolomite reservoirs in Zhongshen Area are derived from Cambrian - Lower Ordovician source rock, and the differential accumulation of gas is the joint effect of reservoir physical property and development degree of fracture network system.
  • Compaction and hydrocarbon accumulation of Triassic Yanchang Formation Chang 8 Member, Ordos Basin, NW China: Evidence from geochemistry and fluid inclusions
    FU Jinhua, DENG Xiuqin, WANG Qi, LI Jihong, QIU Junli, HAO Lewei, ZHAO Yande
    Petroleum Exploration and Development, 2017, 44(1): 48-57. https://doi.org/10.11698/PED.2017.01.06
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    Crushing, acid treatment and step wise separation and oil extraction were employed to obtain the different occurrence state hydrocarbons. All these fractions have been analyzed by Gas Chromatography-Mass Spectrometer (GC-MS). The fractions relationship and related oil charging process can be mirrored through the analysis of fractions weight content and geochemical characteristics, in combination with the research of inclusions homogenization temperature and fluorescence spectrum parameters. Experimental results reveal that there are four state hydrocarbons, i.e. free hydrocarbon, sealed hydrocarbon, hydrocarbon in carbonate cement, and hydrocarbon within inclusions caught by quartz grains and feldspar grains in the oil-rich sandstones of Chang8 Member, Triassic Yanchang Formation in the Ordos Basin. Among them, the overwhelming fraction is the free hydrocarbon, averaged 93.4%. Fluorescence spectrum parameters of λmax, QF535 and Q650/500 show that the crude oil maturity of the inclusions imprisoned in feldspar, quartz, and carbonate cement increase in turn, and the parameter values of the inclusions in feldspar and quartz are similar and much different from those of carbonate cement. The homogenization temperature values of the three type inclusions bear the similar feature. Through analysis of C29ββ/(αα+ββ) and C2920S/(20S+20R), together with methylphenanthrene ratio, it is revealed that thermal-evolutionary degree of the hydrocarbon within inclusions, hydrocarbon in carbonate cement, sealed hydrocarbon, free hydrocarbon reflects an upward trend, and the data of the last two type are similar. Integrated study of diagenetic sequence and thermal evolutionary degree suggest that the Chang 8 sandstones had been compacted before reservoir formation and the reservoirs have experienced three phase of charge events in which the third one played the most important role for reservoir formation.
  • Karst paleogeomorphology of the fourth Member of Sinian Dengying Formation in Gaoshiti-Moxi area, Sichuan Basin, SW China: Restoration and geological significance
    JIN Mindong, TAN Xiucheng, TONG Mingsheng, ZENG Wei, LIU Hong, ZHONG Bo, LIU Qingsong, LIAN Chengbo, ZHOU Xinghe, XU Hu, LUO Bing
    Petroleum Exploration and Development, 2017, 44(1): 58-68. https://doi.org/10.11698/PED.2017.01.07
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    Based on 3-D seismic data and drill-hole data in Moxi-Gaoshiti area, the impression seismic thickness from the top of Longwangmiao Formation, which is easier traced, to the bottom of Cambrian System was selected to characterize the karst paleogeomorphology of the fourth Member of Dengying Formation. The paleogeomorphology of the member can be further divided into three geomorphic units: karst platform, slope and superimposed slope, which had different paleohydrologic conditions, and thus different karstification intensity and reservoir quality. Among them, the superimposed slope with the strongest dissolution, has larger solution groove and cave systems, where the reservoirs with mainly honeycombed dissolved pores and cavities as storage space, are best in quality; the platform slope with weaker dissolution, has smaller solution groove and cave systems, where the reservoirs are poorer than those in the superimposed slope; the karst platform with the weakest dissolution, has piebald karst systems mainly, where the reservoirs with mainly pinhole to smaller dissolved pores and cavities as storage space, are poorer in quality on the whole, but there are some good quality reservoir bodies in local areas. The results show that, besides the highly explored scarp belt, the karst platform with low exploration degree can also be favorable exploration area of the fourth member of Dengying Formation.
  • Mechanisms of shale gas generation and accumulation in the Ordovician Wufeng-Longmaxi Formation, Sichuan Basin, SW China
    BORJIGIN Tenger, SHEN Baojian, YU Lingjie, YANG Yunfeng, ZHANG Wentao, TAO Cheng, XI Binbin, ZHANG Qingzhen, BAO Fang, QIN Jianzhong
    Petroleum Exploration and Development, 2017, 44(1): 69-78. https://doi.org/10.11698/PED.2017.01.08
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    The source rock quality, organic pore structure, occurrence state and sealing mechanisms of shale gas in the Ordovician Wufeng-Longmaxi Formation (O3w-S1l), Fuling region, Sichuan Basin were studied using ultra-microscopic organic maceral identification, FIB-SEM, high temperature/pressure isothermal adsorption and isotopic age dating of noble gas. The results show that: (1) O3w-S1l organic-rich shale was mainly formed in a sedimentary environment with high productivity in surface water and hypoxia in bottom water, it can be divided into two sections according to TOC, of which the lower section (TOC≥3%) is mainly composed of graptolite, phytoplankton, acritarch, bacteria and solid bitumen, among them, graptolite is the main contributor to TOC, but the shale gas is mainly derived from phytoplankton, acritarch and other hydrogen-rich organic matter, as well as the pyrolysis of liquid hydrocarbons produced by this kind of organic matter. (2) Organic pores, as principal reservoir space for shale gas, exist in hydrogen-rich organic matter and solid bitumen. The graptolites and plenty of other organic matter stacking distribution in lamina provide more reservoir space for shale gas, and effective pathways of connected pores for fluid flow. (3) Shale gas in Fuling region is in supercritical state and dominated by free gas; the match of formation time of closed shale gas system and gas-generation peak, as well as slight alteration degree of sealing conditions in the later stage, are key factors controlling the retention and accumulation of shale gas in the regions with high thermal maturity and complex structural areas; adsorption, capillary sealing and slow diffusion of shale are the main microscopic mechanisms for the retention and accumulation of shale gas. It thus can be seen that the generation and accumulation of marine shale gas with high thermal maturity in complex structure areas is controlled jointly by anoxic depositional environment, excellent hydrocarbon rock quality, superior reservoir space and favorable sealing conditions.
  • Karst reservoirs seismic prediction of Lower Permian Maokou Formation in central Sichuan Basin, SW China
    DAI Xiaofeng, ZHANG Ming, JIANG Qingchun, FENG Zhou
    Petroleum Exploration and Development, 2017, 44(1): 79-88. https://doi.org/10.11698/PED.2017.01.09
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    Based on the new well logging and seismic data of recent years in central Sichuan Basin, the comprehensive study of the karst reservoirs in the Lower Permian Maokou Formation was carried out using new geophysical technology. The quantitative rock physical modeling and analysis demonstrated that the velocity and density of the reservoir decrease with the increase of porosity, shale volume and gas saturation. Seismic forward modeling analysis based on rock physical modeling confirmed that the reflection characteristics of the karst reservoirs show ‘dim point’ at top of the Maokou Formation, which is weak amplitude and low frequency. Through seismic attributes and wave impedance inversion, four large areas of favorable karst reservoirs are predicted. Based on the comprehensive evaluation, it is thought that karst lithologic reservoirs in up-dip direction can be formed, and the west to Shehong and Yanting are the most favorable exploration areas in the central Sichuan Basin.
    • OIL AND GAS FIELD DEVELOPMENT
  • Water producing mechanisms of carbonate reservoirs gas wells: A case study of the Right Bank Field of Amu Darya, Turkmenistan
    CHENG Youyou, MU Longxin, ZHU Enyong, ZHANG Peijun, GUO Chunqiu, LENG Youheng, WEI Zhanjun, CHEN Pengyu, XING Yuzhong, CHENG Muwei, SHI Haidong, ZHANG Liangjie
    Petroleum Exploration and Development, 2017, 44(1): 89-96. https://doi.org/10.11698/PED.2017.01.10
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    The mechanisms of carbonate gas reservoirs were systematically studied with the Right Bank Field of Amu Darya Gas Field, Turkmenistan, as an example. Water produced from the reservoirs has three sources, condensate water, engineering fluids and formation water. The fluid physical property and water-gas ratio (WGR) method for the single component conditions and the chloridion conservation method for the multi-components conditions were established to identify the components contained in the production fluids. A water production diagnosing curve, which refers to the degree of reserve recovery as a function of the water-gas ratio in the log-log coordinate curve, was then established and the formation water producing wells were divided into three patterns, i.e. Type 1, Type 2, and Type 3. Through in-depth studies of the static and dynamic reservoir characteristics of each pattern, the following understandings were attained: The reservoirs of Type 1 are mainly porous, and the water producing mechanism is bottom water coning along matrix pores; the reservoirs of Type 2 are mainly fractured-porous, and the bottom water produces basically through the natural fracture system; the reservoirs of Type 3 are mainly fractured-cavity, and the bottom water produces basically through large-scale fractures and caves.
  • Permeability characterization and directional wells initial productivity prediction in the continental multilayer sandstone reservoirs: A case from Penglai 19-3 oil field, Bohai Bay Basin
    LIU Yancheng, LUO Xianbo, KANG Kai, LI Tingli, JIANG Shuhong, ZHANG Jun, ZHANG Zhang, LI Yunting
    Petroleum Exploration and Development, 2017, 44(1): 97-103. https://doi.org/10.11698/PED.2017.01.11
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    Based on study on the main factors affecting the initial productivity of directional wells in multilayer sandstone reservoirs of Penglai 19-3 oil field, a permeability interpretation model based on lithofacies constraint was established, and an initial productivity prediction formula for directional wells in offshore multilayer sandstone reservoirs was derived. Permeability and oil saturation are the main factors affecting initial productivity of directional wells in Penglai 19-3 oil field. Using core, scanning electron microscope, casting thin section, logging and production data, and a new permeability interpretation model considering the influence of macro sedimentary characteristics and microscopic pore structure was built. On the basis of permeability correction, resistivity increase ratio is introduced to characterize the effect of oil saturation, to modify the Vandervlis productivity formula of directional wells to get an initial productivity prediction equation suitable for continental multilayer sandstone reservoirs. The study results show that the permeability considering petrographic constraints and the production forecasting formula including resistivity increase ratio are more accurate.
  • Multiphase boundary of C16+ heavy n-alkanes and CO2 systems
    LIU Xiaolei, QIN Jishun, HAN Haishui, LI Shi, JI Zemin
    Petroleum Exploration and Development, 2017, 44(1): 104-109. https://doi.org/10.11698/PED.2017.01.12
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    N-eicosane, N-tetracosane, N-octacosane and N-dotriacontane, which are heavy n-alkanes, were selected to form binary systems with CO2. The bubble point pressures of each system were obtained through a series of constant component expansion (CCE) experiments. Variation laws and mechanisms of multiphase boundary of heavy n-alkanes-CO2 systems were studied. As CO2 fraction increased, the bubble point pressure of heavy n-alkanes-CO2 systems increased greatly, and the bubble point pressure increased linearly with temperature. When CO2 molar fraction is less than 50%, the bubble point pressure of the heavy n-alkanes-CO2 systems decreased slightly with the increase of carbon number, and the decrease of pressure amplitude decreased with the decrease of CO2 mole fraction. When CO2 molar fraction was 75%, the bubble point pressure of different heavy n-alkane systems increased slightly with the increase of carbon number. When CO2 molar fraction was less than 50%, with the increase of the carbon number, the influence of temperature variation on the bubble point pressure of systems decreased. When CO2 molar fraction was equal to 75%, with the increase of the carbon number, the influence of temperature variation on the bubble point pressure of heavy n-alkanes-CO2 systems did not change. On the analysis of micro scale, the reason for variation laws above is that the long chains and large intermolecular interval of heavy n-alkane has ability to accommodate CO2 molecules and its chain is prone to twist.
  • The formation and viscoelasticity of pore-throat scale emulsion in porous media
    ZHOU Yazhou, WANG Demin, WANG Zhipeng, CAO Rui
    Petroleum Exploration and Development, 2017, 44(1): 110-116. https://doi.org/10.11698/PED.2017.01.13
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    The emulsion process in reservoirs was simulated by core displacement experiment, and the formation mechanisms of emulsion were studied by visualization core displacement experiment. The particle size distribution of formed emulsion at different transport distances, emulsifier concentration or injection rates and the condition of forming stable emulsion of pore-throat scale were analyzed. By measuring the viscosity, the storage modulus and the elastic modulus of the formed emulsion, viscoelasticity of emulsion was studied. The study shows that the formation mechanisms are mainly the snaping action of residual oil and the shearing action of emulsifier solution. When the migration distance is greater than 1/3 times the injector-producer spacing, the emulsifier concentration is between 0.4% and 0.5% and the injection rate is between 0.3 mL/min and 0.4 mL/min, the pore-throat scale emulsion with favorably stability can be formed. The viscosity is between 48.6 mPa·s and 70.3 mPa·s when the shear rate is 7.34 s-1 and the emulsifier concentration is between 0.4% and 0.5%. The storage modulus and loss modulus of emulsion increase with the emulsifier concentration increasing, and the viscoelasticity of emulsion is enhanced.
    • PETROLEUM ENGINEERING
  • Numerical simulation of multi-stage fracturing and optimization of perforation in a horizontal well
    ZHAO Jinzhou, CHEN Xiyu, LI Yongming, FU Bin, XU Wenjun
    Petroleum Exploration and Development, 2017, 44(1): 117-124. https://doi.org/10.11698/PED.2017.01.14
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    Aiming at analyzing the issues of non-uniform growths of multiple hydraulic fractures caused by stress shadowing, a numerical model considering elasto-hydrodynamic, stress interference and flow distribution into different fractures was built. Based on the model, the effects of perforation friction, perforation cluster spacing, Young modulus of rock and fracturing fluid viscosity on the growth of multiple fractures were investigated. The simulation results show that the growths of hydraulic fractures are relatively uniform with adequate perforation friction; the reduction of perforation cluster spacing, increase of Young modulus or fluid viscosity will cause the reduction of some fracture width and uneven flow distribution into these fractures, thus aggravating non-uniform growth of multiple fractures. Since appropriate perforation friction is conducive to the uniform growth of fractures, a convenient quantitative optimization method to calculate the needed perforation friction for uniform growth was proposed. By estimating interfracture induced stress during fracturing, the perforation friction coefficient needed to maintain uniform growth of fractures inside a stage is calculated, and reasonable engineering parameters of perforation can be selected based on this. The perforation parameters of a horizontal well were calculated with the proposed method, and the simulation results and actual fracturing performance show that the optimized perforation parameters can effectively keep uniform growth of fractures.
  • A new physical simulation system of drilling mud invasion in formation module
    FAN Yiren, WU Junchen, WU Fei, ZHOU Cancan, LI Chaoliu
    Petroleum Exploration and Development, 2017, 44(1): 125-129. https://doi.org/10.11698/PED.2017.01.15
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    After several key technologies, including the saturation and pressurization of large sample, design of invasion room, sealing and pressure maintaining of the apparatus, and dynamic monitoring of the entire invasion process were solved, a multifunctional physical simulation system of drilling mud invasion in formation module has been designed and built. By using the system, the variation patterns of formation module resistivity, pressure and mud cake parameter during the invasion are summarized. The design idea, components, and functions of each component of the system are introduced in this paper; and a drilling mud invasion experiment in the sandstone formation module was done. The experiment results show that the radial resistivity of formation module decreases in turn during brine drilling mud invasion; at the beginning of invasion, the mud cake is gradually formed with the increase of its thickness and the decrease of its porosity and permeability, and the radial pressure gradient of formation module decreases rapidly; in the middle and late periods of invasion, the mud cake properties and the radial pressure gradient of formation module become stable. The designed system, with high simulation degree, high utilization ratio and good maneuverability, can be used to reveal the invasion mechanism of drilling mud in sandstone reservoirs, analyze invasion characteristics, and improve invasion correction method for logging response and other researches.
  • Application of capacitance resistance models to interwell connectivity of large-scale mature oil fields
    JAMALI Ali, ETTEHADTAVAKKOL Amin
    Petroleum Exploration and Development, 2017, 44(1): 130-136. https://doi.org/10.11698/PED.2017.01.16
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    In view of the problems existing in the application of Capacitance Resistance Models (CRMs) to large-scale mature oil fields, Capacitance Resistance Model for Producers (CRMP) was selected for analysis, a simplified procedure for applying CRMP to large-scale mature oil fields was proposed, and some examples analyzed. A simplified derivation for CRMP was presented with consideration of characteristics of large-scale mature oil fields. Several strategies were presented to optimize the solution method, in order to shorten the solution time and speed up convergence rate. These include the implementation of a global optimization algorithm, parameter scaling, analytical development of gradient vector and Hessian matrix of the CRMP objective function and so on. These improvements enable the application of CRMP to large-scale problems. Stepwise history matching was shown to be an effective technique to improve reliability of the analysis. Example analysis results show that, the connectivity got by the presented method agrees with the practical production, which proves the reliability of the presented method. The connectivity of an injector to the nearby producers can be analyzed based on the CRMP simulation results, and the analysis results can be used for related study, such as determining current water injectors suited for CO2 injection, or current CO2 injectors not suited for CO2 injection.
  • Solution mining technology of enlarging space for thick-sandwich salt cavern storage
    ZHENG Yali, ZHAO Yanjie, DING Guosheng, WU Zhide, LU Shouquan, LAI Xin, QIU Xiaosong, YANG Dong, HAN Bingjie, WANG Lingxin
    Petroleum Exploration and Development, 2017, 44(1): 137-143. https://doi.org/10.11698/PED.2017.01.17
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    Aiming at the current problem that thick sandwiches are commonly developed in domestic salt mines, this study investigated whether thick sandwiches would collapse to allow connection of salt deposits above and below, consequently increase leaching height and expand single cavern capacity by laboratory experiments, numerical simulation and field tests. The analysis of water-soluble mechanism and changing patterns of mechanical parameters of sandwich layers after water immersion shows that: after water immersion, sandwiches dissolve into honeycomb structure with cracks that easily flake, and the residues occupy small space; after water immersion, mechanical strength of sandwiches decrease greatly, susceptible for failure and collapse. Based on the calculation model for critical limited span, the collapse timing was predicted. In addition, laws of thick sandwiches collapse were obtained by numerical simulation, which indicate that the smaller the thickness, the larger the depth, the larger the limited span and storage height of the sandwiches, the more likely the sandwich will collapse. The design idea of “full immersion and secondary cavity construction” was proposed, and cavern leaching design for a 12 meter thick sandwich in a gas storage was made, and tests on two wells were conducted. The results prove that thick sandwiches could collapse, increasing leaching height and single cavity capacity, and the technology is technologically and economically feasible.
    • COMPREHENSIVE RESEARCH
  • Concept, technology and practice of “man-made reservoirs” development
    ZOU Caineng, DING Yunhong, LU Yongjun, LIU Xiangui, CHEN Jianjun, WANG Xin, YANG Zhengming, CAI Bo, YANG Zhi, HE Chunming, WANG Zhen, LUO Yutian
    Petroleum Exploration and Development, 2017, 44(1): 144-154. https://doi.org/10.11698/PED.2017.01.18
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    Oil and gas resources in low permeability and unconventional reservoirs are playing more and more important role in global energy supply, and are confronted with pressing problems in hard development, quick production decline, low recovery efficiency and high exploitation cost. Therefore, new development concept “man-made reservoirs” and a complete set of techniques and methods are proposed. With “sweet spots” as units, an integrated way of fracturing, injection and recovery is presented for the low permeability oil and gas resources to reconstruct the underground seepage field and petroleum output system and finally to realize enhancement of the recovery efficiency. Well-group development, fracturing and targeted fluid injection are applied to change the underground seepage field, supplement the formation energy, and form “man-made high permeability area” and “reconstructed seepage field”. By integration of information technology including big data, cloud computing, artificial intelligence etc., an integrated information management platform of “man-made reservoirs” including geology, development, production, management and decision has been set up, and large-scale, effective and sustainable development of this kind of resources are realized. Five series techniques are developed including 3D seismic geological evaluation for sweet spot area, well-group platform development, intellectual volume fracture, imbibition displacement and energy complement development, and intellectual management development based on cloud computing for “man-made reservoir”. In China, five blocks of shale gas and tight oil have been tested 235 times, and the effect of tight oil fracturing and output was 2 times better than that before, has achieved business development and showed bright perspectives.
    • ACADEMIC DISCUSSION
  • New knowledge of hydrocarbon generating theory of organic matter in Chinese marine carbonates
    LIU Wenhui, BORJIGIN Tenger, WANG Xiaofeng, LI Maowen, HU Guang, WANG Jie, LU Longfei, ZHAO Heng, CHEN Qianglu, LUO Houyong
    Petroleum Exploration and Development, 2017, 44(1): 155-164. https://doi.org/10.11698/PED.2017.01.19
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    The marine carbonates of the Tarim Basin are taken to study the relationship between source rock and oil and gas reservoirs and discuss the possibility and mechanisms of mature and low-TOC (less than 0.5%) marine carbonates being source rock. By studying the matching relationship between source rocks in Tarim Basin and hydrocarbon reservoirs in Tahe oilfield and analyzing the hydrocarbon-generating organism combination and its correlation with geochemical characteristics of oil and gas reservoirs, this study established a method to evaluate hydrocarbon generation substance of marine carbonate source rocks. It is concluded that the crude oil of the Tahe oilfield in the Tarim Basin is not derived from muddy source rocks, but has the obvious characteristics derived from carbonate source rocks. It revealed that the underestimated hydrocarbon-generating substance (organic acid salts) in the highly evolved marine carbonate rocks and high quality hydrocarbon-generating organism are the key to high-evolution carbonate rocks being as source rock. Organic acid salts have high hydrocarbon conversion rate and are mainly cracked into natural gas at high temperature. The development model of the source rocks of the Cambrian-Lower Ordovician carbonate source rocks in the Tarim Basin is dominated by the shelf model.
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