Hasil untuk "Petroleum refining. Petroleum products"

XU Hui, SONG Qian, PAN Binlin et al.

Conventional oil displacement polymers are partially hydrolyzed polyacrylamide （HPAM）. When the temperature is above 80 °C， the hydrolysis rate of acid amide accelerates， and the carboxylic acid produced after hydrolysis is prone to complex with calcium and magnesium ions to form precipitation， which significantly reduces the performance of HPAM. To improve the temperature and salt resistance of the polymer， The polymerization of acrylamide （AM） monomer with three anti-hydrolytic monomers N-vinylpyrrolidone （NVP）， dimethylacrylamide （DMAA）， and 2-acrylamide-2-methylpropanesulfonic acid （AMPS） is often carried out in binary， ternary or quaternary copolymerization， but the influence of each monomer on the properties of polymers has not been deeply studied. So， three kinds of hydrolysis resistant binary copolymers P（AM-AMPS）， P（AM-DMAA）， and P（AM-NVP） were synthesized by copolymerization of three kinds of monomers with AM respectively. The effects of the introduction of three monomers on polymer properties were investigated. The results show that the introduction of 20% NVP， DMAA， and AMPS on the HPAM main chain leads the viscosity-average molecular weight of the polymer to reduce from 3 050×104 to 720×104， 1 500×104 and 2 800×104， respectively. The average hydrodynamics diameters decrease by 39.5%， 27.7%， and increase by 12.4%， respectively. The effect of the introduction of AMPS on the molecular weight of HPAM was significantly smaller than that of NVP and DMAA. Due to the lack of complexation between the sulfonic acid anion in AMPS and calcium and magnesium ions， the strong intermolecular repulsion allows molecular chains to be more stretched in aqueous solutions， which significantly improves the viscosity， viscoelasticity， and thermal stability of the polymer. The results of laboratory and field experiments show that P（AM-AMPS） can significantly improve the oil displacement performance of the polymer under high temperature and high salt reservoir conditions， indicating a broad application prospect.

Junlin LIU, Yi WU, Zilei SHEN et al.

Aqueous zinc⁃ion batteries demonstrate broad application prospects due to their high safety,low cost,excellent electrochemical performance,and other characteristics.This review systematically summarizes structural regulation strategies for flexible electrolytes tailored for aqueous zinc⁃ion batteries.It focuses on the construction methods,ion conduction mechanisms,and mechanical reinforcement approaches of hydrogel and polymer electrolytes.In addition,it analyzes the key challenges related to electrochemical stability,interfacial compatibility, and environmental adaptability.This work aims to advance the development of flexible electrolytes for enhancing the electrochemical performance of aqueous zinc⁃ion batteries and provide theoretical guidance and research references for the design and functional realization of flexible electrolyte materials.

LIU Yuejiao, SUN Jianmeng, YANG Dong et al.

China's continental shale oil resources have huge potential and are an important strategic replacement resource for conventional oil and gas in China. This study focuses on the construction of the shale oil reservoir evaluation system of the Liushagang formation in the Weixi'nan sag. In view of the characteristics of the shale oil reservoir space types of the Liushagang formation in the Weixi'nan sag being diversified (matrix type, laminar type and interlayer type) and the significant heterogeneity of the reservoir, starting from the characteristics and comprehensive evaluation investigation of typical domestic shale oil. The similarities and differences between the shale oil in the Weixi'nan sag and typical domestic shale oil are compared. By exploring the tripartiality characteristics among the main evaluation parameters, the threshold boundaries of the evaluation parameters were reasonably determined, and a sweet spot comprehensive evaluation standard for different types of shale oil was constructed. Based on the constructed standards, the connection evaluation and comparison of five wells in the study area are conducted. The results showed that the type I comprehensive sweet spot section is mainly concentrated in the matrix type shale oil reservoir, and the validity of the comprehensive evaluation is verified based on the gas measurement and logging data. The research results will provide quantitative decision-making reference basis for the selection of shale oil development strata in Weixi'nan sag, and offer theoretical references for the improvement of the classification and grading evaluation standards of continental shale oil in China.

Jamil F. El-Masry, Elsa Maalouf, Azza H. Abbas et al.

Chemical enhanced oil recovery (CEOR) is well known for its success in recovering the trapped oil in reservoirs after waterflooding operations. In CEOR, synthetic chemicals are utilized to increase the capillary number or modify the mobility ratio of reservoirs; however, they are expensive and are associated with environmental concerns. Hence, the rise in environmental awareness paved the way for environmentally friendly and cheaper alternatives, such as green products, to replace synthetic chemicals. This paper comprehensively reviews recent studies on applying green products in CEOR. It also includes comparisons between the performance of several green products and their synthetic counterparts in CEOR. Moreover, limitations, cost, and environmental footprints are analyzed. Finally, the displacement efficiency of green chemicals and pertinent challenges in the field are highlighted. While the utilization of some natural materials in EOR still has an environmental impact, they constitute a safer option than synthetic chemicals. Furthermore, green materials are more affordable than synthetic chemicals that are commonly utilized, making them a financially viable option for EOR. An up-to-date overview is urgently needed due to the growth of natural chemical utilization in oil and gas applications. Promoting sustainable alternatives is essential to addressing the rise in global environmental concerns.

Xiongqi PANG, Chengzao JIA, Zhi XU et al.

Natural gas hydrate (NGH), as a widely recognized clean energy, has shown a significant resource potential. However, due to the lack of a unified evaluation methodology and the difficult determination of key parameters, the evaluation results of global NGH resource are greatly different. This paper establishes a quantitative relationship between NGH resource potential and conventional oil and gas resource and a NGH resource evaluation model based on the whole petroleum system (WPS) and through the analysis of dynamic field controlling hydrocarbon accumulation. The global NGH initially in place and recoverable resources are inverted through the Monte Carlo simulation, and verified by using the volume analogy method based on drilling results and the trend analysis method of previous evaluation results. The proposed evaluation model considers two genetic mechanisms of natural gas (biological degradation and thermal degradation), surface volume conversion factor difference between conventional natural gas and NGH, and the impacts of differences in favorable distribution area and thickness and in other aspects on the results of NGH resource evaluation. The study shows that the global NGH initially in place and recoverable resources are 99×1012 m3 and 30×1012 m3, with averages of 214×1012 m3 and 68×1012 m3, respectively, less than 5% of the total conventional oil and gas resources, and they can be used as a supplement for the future energy of the world. The proposed NGH resource evaluation model creates a new option of evaluation method and technology, and generates reliable data of NGH resource according to the reliability comprehensive analysis and test, providing a parameter basis for subsequent NGH exploration and development.

Mohammad Hossein Madadi, Masoumeh Kordi, Arezoo Abedi

Abstract The type and amount of distribution of evaporite minerals within reservoir rocks play important role in reservoir quality. This study focuses on thin section petrography, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, aqueous fluid inclusions microthermometry, and UV fluorescence microscopy of hydrocarbon fluid inclusions, to study the genesis of anhydrites within dolomite facies of the Oligocene-Miocene Asmari Formation, Zagros Basin. Petrographic studies of primary (dolomicrite) and secondary (dolosparite) dolomite-dominated facies of the Asmari Formation showed that the associated diagenetic anhydrites occurred in different morphological textures (forms) including poikilotopic, pervasive pore-filling, scattered pore-filling, fracture-filling, and vein cements, nodular and layered forms. Fluid inclusion studies of anhydrites revealed that the diagenetic anhydrites particularly within the dolomicrite facies were formed at an average temperature of 68.2 °C, and by mineralizing solutions with salinity of about 23.5 wt% NaCl. Indeed, in the dolomicrite facies, the anhydrites were associated with gypsum dewatering and/or direct anhydrite precipitation during eodiagenesis. In contrast, in the dolosparite facies, anhydrites were formed at an average temperature of 100.1 °C, and by mineralizing solutions with salinity of about 16.4 wt% NaCl. This latter condition was very likely related to the dolomitization processes including the creation of calcium-rich and magnesium-poor pore fluids with presence of sufficient sulfate ions during the mesodiagenesis. Occurrences of eugenic and mesogenic anhydrites within the dolomite facies were largely controlled the petrophysical parameters as well as the reservoir quality of the Asmari Formation.

SONG Peng, ZANG Jinpeng, XIAO Wenlian et al.

One of the main reasons for the complex mineral composition， significant differences in lithology， and obvious differences in the production capacity of different gas wells after hydraulic fracturing in the Chang 8 reservoir in the Ordos Basin lies in the differences in the morphologies of the fracture networks formed by fracturing the reservoir rocks， which depends on the brittleness of the reservoir rocks. By taking Wuji， Ansai， and Shun 98 blocks in the Ordos Basin as the research object， representative rock samples were selected to carry out rock mechanics experiments， X-ray diffraction whole-rock mineral analysis experiments， and rock pore throat structure analysis. The dynamic and static mechanical parameters， mineral composition and content， and pore throat structure of the dense sandstone were obtained， and the dynamic brittleness index， static brittleness index， and mineral brittleness index of the rock were further calculated. The results show that the dynamic modulus of elasticity of rocks in the Chang 8 dense sandstone reservoir in the study area is larger than the static modulus of elasticity； the dynamic Poisson’s ratio is larger than the static Poisson’s ratio， and the dynamic and static mechanical parameters in the same block have a certain linear relationship. The transformation model of the dynamic and static mechanical parameters was established， featuring static brittleness index > dynamic brittleness index > mineral brittleness index for the same rock samples. Based on the graphs of each mineral content and the static brittleness index， it is clear that the brittle minerals in tight sandstone reservoirs in Wuji-Ansai block of the Ordos Basin are mainly quartz and carbonatite； there are differences in brittleness indexes among the blocks， featuring static brittleness index in Shun 98 block > static brittleness index in Ansai block > static brittleness index in Wuji block. According to the experimental results， the brittleness index is affected by the composition of rock minerals and the rock porosity， pore connectivity， and non-homogeneity. Under the premise of the same mineral composition， a weaker rock non-homogeneity means better pore connectivity and larger pore diameter， as well as greater brittleness.

Milad Moradi, Ali Kadkhodaie, Hossain Rahimpour-Bonab et al.

The upper Dalan and Kangan or Permian-Triassic carbonate formations in the central the Persian Gulf are considered as world's giant gas reservoirs. The primary purpose of this research is to model and evaluate the relationship between hydraulic flow units (HFUs), electrofacies and microfacies with systems tracts of Permian-Triassic sequences. By integrating the results of core data, petrographic studies, and petrophysical logs of the studied formations, hydraulic flow units and electrofacies were identified. Based on the results of petrographic studies, twelve microfacies were identified in terms of textural and depositional characteristics. Based on depositional setting, sedimentary facies and INPEFA values obtained from gamma ray log and gamma deviation log (GDL) in the context of sequence stratigraphy, zonation of Dalan and Kangan reservoirs is carried out. The zonation boundaries correspond to the key stratal surfaces (sequence boundary and maximum flooding surface). Seven petrographic rock types (PRT) were identified for the upper Dalan-Kangan reservoirs based on sedimentary texture, diagenetic process and dominant pores. Using porosity and permeability data from the core analysis, five hydraulic flow units were identified based on the flow zone indicator (FZI) method. Using multi-resolution graph-based clustering (MRGC) four electrofacies were detected from petrophysical data (gamma, neutron, density and acoustic logs). Subsequently, the INPEFA, GDL and electrofacies were spatially modeled using the sequential indicator simulation (SIS) and sequential Gaussian simulation (SGS) geostatistical methods. Finally, a clear agreement was revealed between the reservoir zones and the stratigraphic sequence framework. It this regard, the microfacies belonging to the high-energy and grain-dominated settings (packstone, grainstone) of leeward shoal, shoal and seaward shoal belts have the best reservoir units due to the influence of dissolution and dolomitization. The best reservoir units in the Permian-Triassic deposits in the middle of the upper Dalan and lower Kangan are developed in UDS4, upper KS2 and middle KS1 units. On the other hand, mud-dominated facies (mudstone, wackestone) and anhydrite textures are mostly associated with the low-energy lagoonal environments, between tidal flat and Sabkha. Non-reservoir units have been formed in the upper Dalan/Kangan and in the transgressive systems tract of UDS3-a, KS2-a and the lower and upper part of KS1 transgressive-highstand systems tract.

Yikun LIU, Fengjiao WANG, Yumei WANG et al.

Aiming at the technology of hydraulic fracturing assisted oil displacement which combines hydraulic fracturing, seepage and oil displacement, an experimental system of energy storage and flowback in fracturing assisted oil displacement process has been developed and used to simulate the mechanism of percolation, energy storage, oil displacement and flowback of chemical agents in the whole process. The research shows that in hydraulic fracturing assisted oil displacement, the chemical agent could be directly pushed to the deeper area of the low and medium permeability reservoirs, avoiding the viscosity loss and adhesion retention of chemical agents near the pay zone; in addition, this technology could effectively enlarge the swept volume, improve the oil displacement efficiency, replenish formation energy, gather and exploit the scattered residual oil. For the reservoir with higher permeability, this measure takes effect fast, so to lower cost, and the high pressure hydraulic fracturing assisted oil displacement could be adopted directly. For the reservoir with lower permeability which is difficult to absorb water, hydraulic fracturing assisted oil displacement with surfactant should be adopted to reduce flow resistance of the reservoir and improve the water absorption capacity and development effect of the reservoir. The degree of formation energy deficit was the main factor affecting the effective swept range of chemical agents. Moreover, the larger the formation energy deficit was, the further the seepage distance of chemical agents was, accordingly, the larger the effective swept volume was, and the greater the increase of oil recovery was. Formation energy enhancement was the most important contribution to enhanced oil recovery (EOR), which was the key to EOR by the technology of hydraulic fracturing assisted oil displacement.

Yan Yan, Guan Zhichuan, Yan Weijun et al.

During the process of perforation,the failure of wellbore sealing integrity mainly includes the damage of cement sheath and the formation of micro-annulus at cementing interface.Based on LS-DYNA finite element calculation platform,the downhole perforation process was simulated by means of numerical calculations,the stress response and failure characteristics of casing and cement sheath during perforation were analyzed,and the penetration test on cylindrical target was performed.The results show that the calculation method of shaped charge jet penetration into wellbore could be used to quantitatively analyze the stress response of wellbore during perforation.When a wellbore is perforated,the tensile and shear failure of cement sheath is mainly concentrated within the cone angle of 60°; high-load perforating charge,low modulus cement sheath and high confining pressure increase the stress peak of cement sheath and increase the risk of cement sheath damage.The conclusions provide theoretical support for the optimization of perforations and the prediction of wellbore integrity before fracturing in oil and gas wells.

ZHAO Peirong

In recent years,Sinopec has used the unconventional natural gas idea to strengthen the Permian natural gas explorationin eastern Sichuan and obtained industrial gas flow in the first member of Maokou Formation of several wells in Jiaoshiba of Fulingand its adjacent area,revealing a good prospect for natural gas exploration.In this paper,the sequence stratigraphy,sedimentarycharacteristics,hydrocarbon generation conditions,micro pore structure characteristics and gas bearing property of Mao-1 Memberin Jiaoshiba area are systematically analyzed.The results show that:（1） Mao-1 member can be divided into two fourth-ordersedimentary cycles and eight small layers,which mainly develops four kinds of lithology such as Limestone,micritic limestone,nodular limestone and nodular micritic limestone.（2） The average TOC of the Mao-1 Member ranges from 0.75%to 0.87%,whichon the whole,belongs to carbonate source rock with medium organic matter abundance.The organic matter abundance of micriticlimestone and nodular micritic limestone is relatively low,while the organic matter abundance of limestone and nodular limestoneis relatively high.The type of organic matter is mainly type I and supplemented by typeⅡ.R_oranges from 1.71%to 2.18%,withan average of 1.97%.（3） The Mao-1 Member is an ultra-low porosity and permeability reservoir,and the local layers show thecharacteristics of fractured reservoir.The reservoir space is mainly composed of organic pores,diagenetic contraction fissures ofclay minerals,and grain margin fractures of mineral particles,followed by dissolution pores of carbonate minerals.Moreover,thepore size distribution is mainly mesoporous and macroporous.（4） The natural gas of Mao-1 member is mainly composed of methanewith low heavy hydrocarbon content,which is typical dry gas;δ¹³C₁ranged from-31.25‰to-31.12‰,δ¹³C₂is between-35.28‰and-31.23‰,δ¹³C₃is between-34.87‰and-34.66‰,which is a typical oil type gas.The carbon isotope of alkane series isreversed,showing a trend of changeδ¹³C₁>δ¹³C₂>δ¹³C_3.According to the characteristics,the natural gas from Mao-1 Member is themixture of kerogen cracking gas and liquid hydrocarbon cracking gas.（5） Mao-1 Member has the characteristics of self-generatedand self-reservoired,which is a set of special carbonate reservoir between shale reservoir and fractured reservoir.It is necessary tolearn from shale gas exploration experience,strengthen sweet spot interval evaluation and adaptive engineering technologyresearch,and promote the large scale production and benefit development of natural gas.

Wei YANG, Guoqi WEI, Wuren XIE et al.

Drilling, seismic and logging data were used to evaluate the hydrocarbon accumulation conditions of the mound-shoal complexes in the platform margin of the fourth member of Sinian Dengying Formation in the east side of the Mianzhu-Changning intracratonic rift in the Sichuan Basin. The four understandings are: (1) The platform margin belt of the Deng 4 Member can be divided into three sections, northern, middle and southern; the middle section is at the core of the Gaoshiti-Moxi paleouplift and the structural high now, while the southern and northern sections are at the slope of the paleouplift and the structural lows now; the three sections have similar development characteristics and reservoir features of platform margin mound-shoal complex. (2) In the margin of the east side of the rift, there are several faults nearly perpendicular to the platform margin belt, the faults divide the platform margin belt into rugged paleo-landform, and the high part developed platform margin mound-shoal complexes and the reservoirs are good in physical properties, while the low part developed inter-beach depression and no mound-shoal complexes, where the reservoirs are poor in physical properties. (3) The six groups of faults nearly perpendicular to the platform margin belt divide the platform margin belt into seven large mound-shoal complexes which have similar hydrocarbon accumulation conditions and accumulation evolution process and are rich in petroleum. (4) The inter shoal depressions between the mound-shoal complexes are characterized by tighter lithology, which can block the updip direction of the mounds and shoals at the lower part of the slope of the paleouplift and are favorable for the later preservation of mound-shoal gas reservoirs. This has been proved by Well Jiaotan 1 and Heshen 2 drilled successfully. The mound-shoal complexes on the platform margin of the structural slope area have a good exploration prospect.

Zhiwen DING, Rujun WANG, Fangfang CHEN et al.

Based on comprehensive analysis of tectonic and fault evolution, core, well logging, seismic, drilling, and production data, the reservoir space characteristic, distribution, origin of fault-karst carbonate reservoir in Yueman block of South Tahe area, Halahatang oilfield, Tarim Basin, were studied systematically. And the regular pattern of hydrocarbon accumulation and enrichment was analyzed systematically based on development practice of the reservoirs. The results show that fault-karst carbonate reservoirs are distributed in the form of “body by body” discontinuously, heterogeneously and irregularly, which are controlled by the development of faults. Three formation models of fault-karst carbonate reservoirs, namely, the models controlled by the main deep-large fault, the secondary fault and the secondary internal fault, are built. The hydrocarbon accumulation and enrichment of fault-karst carbonate reservoirs is controlled by the spatiotemporal matching relation between hydrocarbon generation period and fault activity, and the size and segmentation of fault. The study results can effectively guide the well deployment and help the efficient development of fault-karst carbonate reservoirs of South Tahe area, Halahatang oilfield. Key words: Tarim Basin, Halahatang oilfield, South Tahe area, Ordovician, fault-karst, carbonate reservoir, hydrocarbon accumulation, oil-gas enrichment

Jiang Zhaoping, Wang Tong, Li Haitao et al.

The integrated injection and production technology in offshore oil fields requires that the downhole safety valve has a temperature resistance of 350℃ and a working depth of not less than 1 330 m. However, no existing downhole safety valve can meet the requirements. To address the problem, the high temperature deep-water subsurface safety valve is developed. The prototype is produced and to conduct laboratory tests. Finite element stress analysis is carried out on the key component-the compression spring. The results show that the high temperature deep-water subsurface safety valve has simple but reliable structure, with small number of leakage points. All metal seal is adopted. And it can work well from normal temperature to 350℃. Its maximum working depth is up to 1 330 m with the pressure capacity of the valve plate and the whole tool up to 35 MPa. The study could provide references for the field application of high temperature deep-water subsurface safety valve. On-site use of the high temperature deep-water subsurface safety valve is recommended to promote the application as soon as possible.

Ali Kadkhodaie-Ilkhchi, Rahim Kadkhodaie-Ilkhchi

Carbonate reservoirs rock typing plays a pivotal role in the construction of reservoir static models and volumetric calculations. The procedure for rock type determination starts with the determination of depositional and diagenetic rock types through petrographic studies of the thin sections prepared from core plugs and cuttings. In the second step of rock typing study, electrofacies are determined based on the classification of well log responses using an appropriate clustering algorithm. The well logs used for electrofacies determination include porosity logs (NPHI, DT, and RHOB), lithodensity log (PEF), and gamma ray log. The third step deals with flow unit determination and pore size distribution analysis. To this end, flow zone indicator (FZI) is calculated from available core analysis data. Through the application of appropriate cutoffs to FZI values, reservoir rock types are classified for the studying interval. In the last step, representative capillary pressure and relative permeability curves are assigned to the reservoir rock types (RRT) based upon a detailed analysis of available laboratory data. Through the analysis of drill stem test (DST) and GDT (gas down to) and ODT (oil down to) data, necessary adjustments are made on the generated PC curves so that they are representative of reservoir conditions. Via the estimation of permeability by using a suitable method, RRT log is generated throughout the logged interval. Finally, by making a link between RRT’s and an appropriate set of seismic attributes, a cube of reservoir rock types is generated in time or depth domain. The current paper reviews different reservoir rock typing approaches from geology to seismic and dynamic and proposes an integrated rock typing workflow for worldwide carbonate reservoirs.

Shi Xuezhi, Zhou Xiaohu, Qiao Zhiguo

To address the completion contradiction of safety and economy of Yuanba gas field and reduce well construction costs, this paper introduces the performance evaluation and field application of domestic nickel-based alloy casing and tubing, electroplating tungsten alloy liner and titanium alloy tubing during material selection for Yuanba gas field.Studies results suggested that, by feasibility design and system test evaluation, the optimal combination of nickel-based alloy with different depths and large-scale application of domestic materials is a critical way for ultra-deep gas reservoir with high sulfur content to achieve safe and economic completions.The plated tungsten alloy tube is excellent in corrosion resistance, and could meet the requirements for no-barrier liner with the optimization of coating thickness and selection of clamp jaw for pipe tong.Titanium alloy tubing, with the mass of about 60% nickel-based alloy tubing, is excellent both in corrosion resistance and gas sealing performance.Its mechanical property and the entire pipe performance could meet the standards for the carbon steel tubing with same grade.Thus, the titanium alloy tubing could reduce costs while increasing completion safety coefficient, presenting the potential of alternative for conventional nickel-based alloy tubing.

Yaser Ahmadi, Mehdi Hassanbeygi, Riyaz Kharrat

In many reservoirs, after water flooding, a large volume of oil is still left behind. Hot water injection is the most basic type of thermal recovery which increase recovery by improved sweep efficiency and thermal expansion of crude.In the present work, the effects of injection rate and the temperature of the injected water were surveyed by using core flooding apparatus. Water flooding was performed at different rates (0.2, 0.3, and 0.4 cc/min) and temperatures (20 and 90 °C), and the reservoir temperature was about 63 °C. Oil recovery during hot water injection was more than water injection. Moreover, it was concluded that at injection rates of 0.2, 0.3, and 0.4 cc/min breakthrough time in hot water injection occurred 10 min later in comparison to water injection. The results showed that higher oil recovery and longer breakthrough time were obtained as a result of reducing injection rate. In the first 50 minutes, the oil recovery at injection rates of 0.2, 0.3 and 0.4 cc/min was 27.5, 34, and 46% respectively. It was found that at the beginning of injection, thermal and non-thermal injection recovery factors are approximately equal. Moreover, according to the results, recovery factor at the lowest rate in hot water (T=90 °C and q=0.2 cc/min) is the best condition to obtain the highest recovery.

Yang Du, Jin-liang Zhang, Shu-fen Zheng et al.

This paper studies the lithofacies, sedimentary facies, depositional models and reservoir architecture of the rudist-bearing Sar-3 zone of Cretaceous Sarvak in the Southwest of Iran by utilizing coring, thin section, XRD data of five coring wells and 3D seismic data. Research results include the following: According to lithofacies features and their association, the rudist-mound and tidal flat are the main microfacies in the Sar-3 depositional time. By investigating the regional tectonic setting and seismic interpretation, a depositional model was built for the Sar-3 zone, which highlights four key points: 1) The distribution of the rudist-buildup is controlled by the paleo-high. 2) The build-up outside of the wide colonize stage but reached the wave-base level in a short time by regression and formation uplift, and was destroyed by the high energy current, then forming the moundy allochthonous deposition after being dispersed and redeposited. 3) The tidal flat develops widely in the upper Sar-3, and the deposition thickness depends on the paleo-structure. The tidal channel develops in the valley and fringe of the Paleo-structure. 4) The exposure within the leaching effect by the meteoric water of the top of Sar-3 is the main controlling factor of the reservoir vertical architecture. The Sar-3 zone featured as the dualistic architecture consists of two regions: the lower is the rudist reef limestone reservoir and the upper is the tidal condense limestone interlayer. The thickness of each is controlled by the paleo-structure. The Paleo-high zone is the preferential development zone. Based on reservoir characteristics of the different zones, a targeted development strategy has been proposed. Keeping the trajectory in the middle of the oil-layer in the paleo-high, and in the paleo-low, make the trajectory crossing the oil-zone and then keep it in the lower.

Chao LIANG, Zaixing JIANG, Yiting YANG et al.

Based on observation of the outcrops and cores of the Late Ordovician to the Early Silurian Wufeng-Longmaxi shale, developed in the deep water shelf environment, in the southeast of the Sichuan Basin, the mineralogical features, lithofacies characteristics and reservoir space types were studied and the factors affecting reservoir capacity were analyzed by observation of eletron microscope and analysis of mineral content. The mineral composition is dominantly clastic quartz and clay minerals, with feldspar, calcite, dolomite, pyrite and so on. Five lithofacies, i.e. carbonaceous shale, siliceous shale, silty shale, calcareous shale and ordinary shale, were identified in the Wufeng–Longmaxi shale. Seven types of reservoir space, including structural tension fracture, structural shear fracture, interlayer lamellation fracture, pyrite pore, the inter-crystal micro-pore and micro-crack in clay mineral, the edge micro-crack around quartz grains and organic matter pore, were found in the Wufeng–Longmaxi shale. The development of reservoir space is strongly controlled by the mineral composition, lithofacies, organic carbon content, organic matter maturity and diagenesis. Key words: Sichuan Basin, Wufeng–Longmaxi Formation, shale lithofacies, reservoir space, shale gas