Oolitic dolostone is a vital type of carbonate reservoirs. The quantitative calculation and prediction of the reservoir permeability and gas saturation provide an important foundation for the further development of the reservoir, which could determine productivity and select the optimum exploitation layers in the dolostone. The general permeability model links geology and reservoir properties via rock number λ, which varies regularly within a depositional cycle. By using λ, the permeabilities and their changing trend can be indicated within a high resolution depositional framework. The cementation index m, an important parameter in calculating gas saturation by Archie formula, varies with the pore type in the dolostone. The permeability profile resulted from the permeability model by using the primary water saturation, porosity from thin sections, cores, debris, and well logging data; and the gas\|saturation profile from the Archie formula combining with the values of m and formation\|water resistivities in the oolitic reservoir, both of them act as the basis for optimizing development program of the gas reservoir in the dolostone after it was discovered.
Changling fault depression is one of the gas rich areas in the Songliao basin, north\|eastern China. The probable reserve of natural gas is up to 2×108 m3. Geochemical analyses of the gas compositions in the inclusions and the carbon isotope and the study on regional geology and structural history reveal that the CO2 in this area is mantle derived origin and could not be from the degassification of volcanic rocks in Yingcheng formation.The accumulation period of CO2 is in later Cenozoic. There is no CO2 inclusions grown in reservoir rocks for two reasons. Firstly, the inclusions could not be enclosed by authigenic mineral for fast jnjection of CO2 which related with volcanic event. Secondly, the CO2 inclusion could not be formed without water in the pore space of reservoir, for the space had been full of hydrocarbon gases when CO2 injected.
DB1 gasfield is situated in the western part of Kelasu structural belt in Kuqa depression, the gas reserve in DB1 is more than 1 000×108 m3. The structural and geological conditions are very complicated, there are thick gravel areas and high mountains on the surface, evaporate salt bed developed underground. The structural styles are mainly fault\|propagation folds above the salt layers and fault\|bend folds under it. The research concludes that DB1 structure is complicated, in which the faults control hydrocarbon's accumulation and structural characteristics, not only influence the reservoir, but also connect to reservoir and source rock, and decide the condition of the reservoir preserved or destroyed. Above all, it is the key factor to study fault characteristics which could make us know DB1 gas field better.
Damintun Sag is a hydrocarbon rich Cenozoic sag developed on a pre Paleogene base, 0.32 billion tons petroleum were found till 2007. Paleogene is the main oil producing and target layers. According to the tectonic evolution and characteristics of strata and deposition in Damintun Sag, by using drilling cores, cutting logs, well logs and high resolution 3\|D seismic data, 2 second\|order sequences including 7 third order sequences were classified in the Paleogene System. By accurate velocity analysis and combination of well and seismic data, a synchronic stratigraphic sequence framework was established, and the main sequence controlling factors were discussed. Tectonic subsidence, supply of deposits, lake level fluctuation and climate were considered controlling the formation of sequences, and tectonic subsidence was the main factor. The high precision sequence classification and the foundation of the synchronic stratigraphic sequence framework are of great significance to the exploration and research of lithological reservoirs in Damintun Sag.
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The Triassic system of northwestern Jungger Basin is one of the most important producing formation in western China. Intense tectonic movements, complicated tectonic structure styles, fans, braided fluvial deposits, and braided deltas have complicated and diversified the development stages and superposition styles and it's very difficult to forecast the distribution of high grade reservoirs. Based on the analysis of the diagenetic types and features, this paper considers that compaction, cementation and denudation are the dominant diagenesis in the study area. By calculating compaction percentage, cementation percentage and denudation percentage, we classify diagenetic facies. Also the features of distribution are researched and used to guide the exploration by telling the favorable diagenetic facies distribution.
Pore fluid is an important tool to study hydrocarbon accumulation. Through the analysis of geochemical properties of crude oil in Shawan Formation of Dushanzi anticline, it is proven that the hydrocarbon came from lacustrine shale. According to the subsurface water, in the vertical, the connectivity of the upper sandstone is better than that of the lower sandstone, and in the horizon, the distribution of sandstone is controlled by the sedimentary microfacies. The oil in Dushanzi came from Lower\|Middle Jurassic, and then reached Shawan Formation through Dushanzi reverse fault. The distribution of source rock and the development degree of reservoir are the main factors to control hydrocarbon accumulation. Lithologic hydrocarbon reservoirs may be found in the lower members of Shawan Formation.
Based on the identification of cast slice, granularity analysis, mercury penetration curves and physical property statistics, microscopic features such as pore types and structure in the sandstone reservoirs of 2nd member of Shanxi Formation in Ordos basin are studied. The result shows that the gas reservoir spaces of the 2nd member of Shanxi Formation mainly include inter\|granular dissolution pores, survived original inter\|granular pores, debris intragranular dissolution pores, filling ingredient dissolution pores, kaolinite intercrystalline pores and a few of micro\|crevasses. The permeability is correlative with the porosity, but they both are related with the pore structure. Four kinds of reservoirs are identified by the mercury penetration parameters and physical properties of the reservoirs. Class Ⅰ has high permeability, mainly contains inter\|granular dissolution pores, which has good underpropping structure and good communication. Class Ⅱ is a kind of fair quality reservoir, containing inter\|granular dissolution pores, intragranular dissolution pores and kaolinite intercrystalline pores. Class Ⅲ is of lower permeability and contains survived original inter\|granular pores and kaolinite intercrystalline pores. Class Ⅳ only contains isolated micropores. It indicates that quartz\|sandstones with coarse granular texture and pebbled underpropping structure are of high permeability. Sandstone reservoir of pebbled underpropping structure is characterized by double\|peak ggrain distribution, which could accelerate the pore water flowing and conduce to dissolution of filling ingredients, improving the reservoir permeability.
With the data from core, geology, well\|logging and seism, this paper studies the middle upper sections of the third member of Paleogene Shahejie Formation in Ma'xi subsug, and the strata contrast frameworks of cyclic sequence is defined and established. the authors believe 4 types of sedimentary systems were developed in this area in upper\|middle sections of the Paleogene Shahejie formation. They are delta, lacustrine, turbidity current and beach bar sedimentary systems. Subfacies and vertical evolution of the depositional systems are discussed in detail.
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Many natural gas fields and oil\|bearing structures in the Ying\|Qiong basin have been discovered since 1960s. They are chiefly located in the shallow strata of mudsone diapir zones of the Yinggehai basin and in the Ya'nan sag of the Qiongdongnan basin, and have a total gas resource amount more than 0.1 billion cube meters. However, the total exploration degree in this area is very low and the advantageous exploration targets are ambiguous so that the status of petroleum exploration is very passive, without any obvious breakthrough. On the basis of previous petroleum geological laws, therefore, we analyze petroleum resource potential and advantageous exploration targets in different areas of the Ying\|Qiong basin according to their migration and accumulation characteristics. As a result, new exploration areas and possible\|breakthrough targets are pointed out. Furthermore, the middle\|deep beds of the Yinggehai basin and southern deep\|water slope of the Qiongdongnan basin are considered to be the best new exploration targets with excellent resource potential and may become a breakthrough. But now research about these areas is so weak that we should focus our best efforts on the petroleum exploration.
The middle to upper Miocene clastic sediments are the main objective intervals in the study area, and the depth of water is estimated about 2,000 meters. The study area is a typical deepwater sedimentary area, and mainly develops lobe and channel reservoirs. The lobe reservoir presents thick massive sandstone in the well and lobation on plane, but the channel reservoir shows thin interbeds of sandstone and mudstone in the well and meandering lineation on plane. The oil and gas discovered in recent years are mainly distributed in these two reservoirs around the study area, and the two reservoirs are the main oil- and gas-rich area and exploration interval. They are high porosity and permeability reservoirs, have better physical properties, and the physical properties of lobes is better than that of channels in the study area.
At present, the southwestern Shunan region has become a hot spot for exploration and a key area. According to measured and collected data of source rocks, parameters, such as organic carbon content, organic matter type, maturity of organic matter and the intensity to generate hydrocarbon have been evaluated. It shows that source rocks in the area are mainly developed in the Lower Cambrian Qiongzhusi Formation, the Lower Silurian Longmaxi Formation, the Permian Yangxin Series and Lower Triassic Jialingjiang Formation. Among them, clay\|stone is predominant. The organic carbon content is high in the source rock. The organic material type is good. The main kerogen type is Ⅰ—Ⅱ1. Maturity is high. Gas generation is predominant during the high mature and post mature phases. The hydrocarbon generation intensity shows that the condition of Lower Cambrian and Lower Silurian source rock is the best. And they are the main source layer systems in this area. The average hydrocarbon generation intensity is 63×108m 3/km 2 and 44.5×10 8m 3/km 2, respectively.
The Tertiary source rocks in the Northwest Qaidam basin are greatly heterogeneous because they are impure mudstone, so there are many disputes in the understanding and evaluation on the source rocks. In addition, the oil source is the controversial focus in this area. In view of these problems, this research firstly distinguishes the effective source rocks, and then synthetically evaluates on them, which is more reasonable than directly averaging the parameters. According to this research, the main strata of the source rocks are N1 2 and E2 3 in this area, and the most important oil forming zone is located in the area of Xiaoliangshan Nanyisha ouquanzi. On the basis of the oil source correlation result, the oil in the northwest Qaidam originate from indigenous source rocks of N1 2 or E2 3 instead of originating from Mangya depression. The oil is self generating and self preserving and vertically and horizontally migrates in short distance. Xiaoliangshan depression and its peripheral areas are the most important oil forming center and are the exploration orientation in the future.
Based on analyses of source rocks in the Tertiary system in the south area of the western Qaidam basin, the low limit value of TOC is fixed on 0.4%. On this basis, the upper part of Xiagancaigou Formation(E2 3) and the lower part of Xiagancaigou Formation(E1 3) in the Hongshi sag, Zhahaquan sag and Shizigou zone are considered as effective source rocks. By the biomarkers analyses of 24 effective source rocks, we examined the sediment characteristics of the saline lacustrine environment to investigate the Geochemical characteristics. The results show: the Tertiary source rocks in the area are characterized by even over odd preference of n\|Alkanes, Pr/Ph<0.6 and high abundance of gammaceranes and C35 homohopanes, but these characteristics are different in all sags or zones. Different values of Pr/Ph, C35 homohopane/C34 homohopane and gammacerane /C30 hopane reveal that the sediment environment of Tertiary source rocks in the Hongshi sag, Yuejing zone and Shizigou zone is a high saline lacustrine and strong reduction environment and that of Shizigou zone is relatively inferior, while that of Zhahaquan sag is a low\|saline lacustrine and low reduction environment. The two types of oils in the south area of the western Qaidam basin, further, two independent hydrocarbon systems may be indicated by the two patterns of Tertiary source rocks in the same area.
The quantitative evaluation of hydrocarbon\|generating potential of source rocks in the basin is the key problem which should be solved in the oil and gas exploration. Tiancao sag develops many sets of source rocks, but the main source rock is still unclear, and the report about the evaluation of source rock has not been seen. This research takes the dark color mudstone of the Tian 2 well as the dissection object, and takes advantage of many parameters such as organic matter abundance, the type and maturity of organic matter to describe quantitively or qualitatively the hydrocarbon\|generating potential characteristics of the dark color mudstone. Results indicate that the source rock's organic matter abundance of the lower segment in Lower Crataceous Bayingebi Formation is the highest and the thermal evolution is at the mature stage, the organic matter type isⅡ2—Ⅲ, so it should be the main hydrocarbon source rock of Tiancao sag; The organic matter abundance of Lower Crataceous Suhongtu Formation is higher, whose organic matter type isⅡ 2, while its hydrocarbon source rock maturity is not high, therefore, it is the secondary hydrocarbon source rock of Tiancao sag. Although the total organic carbon content of Carboniferous and Jurassic is high, the hydrocarbon generating potential is low and the organic matter type is only Ⅲ, nowadays R O>3.0%, so it is at the overmature stage and belongs to the depletive source rock.
The quantitative evaluation of hydrocarbon generating potential of source rocks in the basin is the key problem which should be solved in the oil and gas exploration. Tiancao sag develops many sets of source rocks, but the main source rock is still unclear, and the report about the evaluation of source rock has not been seen. This research takes the dark color mudstone of the Tian 2 well as the dissection object, and takes advantage of many parameters such as organic matter abundance, the type and maturity of organic matter to describe quantitively or qualitatively the hydrocarbon generating potential characteristics of the dark color mudstone. Results indicate that the source rock's organic matter abundance of the lower segment in Lower Crataceous Bayingebi Formation is the highest and the thermal evolution is at the mature stage, the organic matter type isⅡ2—Ⅲ, so it should be the main hydrocarbon source rock of Tiancao sag; The organic matter abundance of Lower Crataceous Suhongtu Formation is higher, whose organic matter type isⅡ2, while its hydrocarbon source rock maturity is not high, therefore, it is the secondary hydrocarbon source rock of Tiancao sag. Although the total organic carbon content of Carboniferous and Jurassic is high, the hydrocarbon generating potential is low and the organic matter type is only Ⅲ, nowadays R O>3.0%, so it is at the overmature stage and belongs to the depletive source rock.
The oil gas of JZ25 hydrocarbon reservoir is from the hydrocarbon sources of the third member of Shahejie formation, Liaoxi sag. We conclude that there are 2 stages of hydrocarbon charges after studying the organic inclusions in the sandstone of the third member of Shahejie formation. The first stage happened prior to a quartz overgrowth period, during which the organic inclusions were distributed in the micro\|fractures of quartz clastic grains. Liquid hydrocarbon inclusions are the main inclusions, with low GOI and maturation, contributing little to the hydrocarbon accumulation. The second stage happened after quartz overgrowth and JZ25 reservoir was formed mainly in this stage. At this stage the organic inclusions were distributed in the micro\|fractures along the cutting quartz clastic grains or the dissolution pores of feldspath grains, with low GOI and maturation. According to the homogenization temperature combined with burial and geotemperature history, JZ25 hydrocarbon reservoir is considered to be formed between 23~21Ma, which is the end of Palaeogene and the early stage of Neogene.
By means of thermal simulating experiment in the open system, this article focused on the hydrocarbon\|generating characteristics of Trias source rock from well Ha 2 in Tarim basin, it also combined with the alteration of maceral and maturation to discuss the characteristics of generating hydrocarbon. The result of experiment indicate that the accumulative yield is only 1.04 mL/g when the heating temperature is under 400℃( value of R O is below 0.8%), it only reach to 8.2% of the total gas yield. When the heating temperature reaches 600℃, the accumulative yield is 9.23 mL/g (about 72.7％of the total gas yield). The peak yield of hydrocarbon is between the heating temperature 500℃ and 600℃ (the value of R O is from 1.24% to 1.78％), the periodical yield in this evolution period is 6.23 mL/g (about 50% of the total gas yield). Although the humin component still could generate hydrocarbon when the heating temperature reaches 700℃, it has already been entered into the period of dry gas. The period of large quantity of generation has finished.
By means of thermal simulating experiment in the open system, this article focused on the hydrocarbon\|generating characteristics of Trias source rock from well Ha 2 in Tarim basin, it also combined with the alteration of maceral and maturation to discuss the characteristics of generating hydrocarbon. The result of experiment indicate that the accumulative yield is only 1.04 mL/g when the heating temperature is under 400℃( value of R O is below 0.8%), it only reach to 8.2% of the total gas yield. When the heating temperature reaches 600℃, the accumulative yield is 9.23 mL/g (about 72.7％of the total gas yield). The peak yield of hydrocarbon is between the heating temperature 500℃ and 600℃ (the value of R O is from 1.24% to 1.78％), the periodical yield in this evolution period is 6.23 mL/g (about 50% of the total gas yield). Although the humin component still could generate hydrocarbon when the heating temperature reaches 700℃, it has already been entered into the period of dry gas. The period of large quantity of generation has finished.
Kerogen was mixed with montmorillonite, illite, kaolinte, manganese sulfate, and the samples were put into gold\|tubes, welded. Then gold\|tubes in a stainless steel autoclave were pyrolyzed under 100MPa and 200MPa conditions. The quantification of pyrolyzate analysis was performed through Wasson\|ECE Agilent 6890 gas chromatography. The results show that catalytic clays have different effects in the process of pyrolysis and hydrocarbon generation. Kaolinte has a positive effect on hydrocarbon gaseous generation, however, montmorillonite, illite and manganese sulfate retard the generation of hydrocarbon. Pressure can enhance the catalytic activity of catalytic clays, the yields of hydrocarbon gaseous are increased with pressure. At the level of 200 MPa, it is most obviously for montmorillontie to improve the catalytic activity, but kaolite is little. The influence of pressure on clay\|catalytic hydrocarbon generation comes from the difference of clay mineral structure and its respons to pressure.
The Toutunhe sandstone reservoir in Niuquanhu area of Santanghu oilfield is mainly lithic sandstone, with an average porosity of 19.7% and average permeability of 77.9×10 -3 μm 2. The pore structure types are mainly intergranular pore, secondary are intergranular dissolved pore, feldspar dissolved pore, cuttings dissolved pore, and carbonate dissolved pore is seldom. With the help of casting thin slice, scanning electron microscope, conventional mecury penetration, and rate controlled mercury penetration, this paper indicates that the microscopic pore structure in the sandstone reservoir is complicated, and the anisotropism here is strong, the water flushing efficiency of the water\|flooding is low, it is resulted from the reservoir microscopic anisotropism.
Taking the north area of Banqiao oil field as example, studies are focused on the depositional characteristics, sand Taking the north area of Banqiao Oilfield as an example, this paper studies the depositional characteristics, sand distribution and formation heterogeneity of the gravity flow depositional reservoir. Combining with the injection to production pattern, it summarizes the residual oil distribution law and the future development potentials of this kind of reservoirs after water flooding. On the basis the distribution features of various potentials and their controlling factors, it also puts forward the effective development strategies focused on enhancing reservoir recovery. The forecasting and application results show that the development results are better than before and the reservoir ultimate recovery can be increased after the application of development technology policies.[JP]
Aiming at the problem of complex distribution of remaining oil and the poor effect of adjustment in the cut period, this paper studies rhythmic layering subdivision and sedimentary microfacies. All these are based on sedimentology and sequence stratigraphy. We find that the critical geologic factors in the remaining oil distribution are the properties of rhythmic layering and the interlayers. Based on the conclusion, we reconstruct the well pattern of rhythmic layering and achieve a good result.
Considering the phase behavior of multi phase liquids, this paper developed a dynamic inflow model for the gas well, and established a performance prediction model of condensate gas wells. In combination with the formation inflow model, wellbore outflow model, it has also drawn a system analysis curve. Through this curve, we can predict the gas well production performance more directly and comprehensively. Also we can accurately predict the production performance of gas well at different times, improving the analysis result of numerical simulation.
Natural gas hydrate is widely distributed in the permafrost and marine sediments all over the world. In order to exploit and utilize it, the mechanism of dissociation in porous media should be mastered. This article summarized the dissociation methods of the gas hydrate in porous media at present, such as thermal stimulation, depressurization, chemical injection and carbon dioxide replacement. The advantages and disadvantages of each have been discussed. It provides the research progress on the dissociation model of gas hydrate, and gives some suggestions on the development.
To study the impacts of the ice particle size on the self preservation of methane hydrate, the dissociation experiment of methane hydrates were carried out. It contains six different sizes of ice particles under two different temperatures, aiming at analyzing the impacts of the total release volume of methane and the dissociation rate on the self preservation time. The results show that the size of the ice particle had evident impacts on the dissociation of methane hydrates. The total release volume of methane and the dissociation rate were inversely proportional to the ice particle size, the smaller the ice particle size, the faster the dissociation rate. This feature was very remarkable at the beginning of the dissociation. And, the methane hydrate formed by the bigger size of ice particle had more effective self\|preservation.
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