The Triassic Jialingjiang Formation and Leikoupo Formation are characterized by thick salt layers. Three tectono-stratigraphic sequences can be identified according to detachment layers of Lower-Middle Triassic salt b...The Triassic Jialingjiang Formation and Leikoupo Formation are characterized by thick salt layers. Three tectono-stratigraphic sequences can be identified according to detachment layers of Lower-Middle Triassic salt beds in the northern Sichuan Basin, i.e. the sub-salt sequence composed of Sinian to the Lower Triassic Feixianguan Formation, the salt sequence of the Lower Triassic Jialingjiang Formation and Mid-Triassic Leikoupou Formation, and the supra-salt sequence composed of continental clastics of the Upper-Triassic Xujiahe Formation, Jurassic and Cretaceous. A series of specific structural styles, such as intensively deformed belt of basement-involved imbricated thrust belt, basement-involved and salt-detached superimposed deformed belt, buried salt-related detached belt, duplex, piling triangle zone and pop-up, developed in the northern Sichuan Basin. The relatively thin salt beds, associated with the structural deformation of the northern Sichuan Basin, might act as a large decollement layer. The deformation mechanisms in the northern Sichuan Basin included regional compression and shortening, plastic flow and detachment, tectonic upwelling and erosion, gravitational sliding and spreading. The source rocks in the northern Sichuan Basin are strata underlying the salt layer, such as the Cambrian, Silurian and Permian. The structural deformation related to the Triassic salt controlled the styles of traps for hydrocarbon. The formation and development of hydrocarbon traps in the northern Sichuan Basin might have a bearing upon the Lower-Middle Triassic salt sequences which were favorable to the hydrocarbon accumulation and preservation. The salt layers in the Lower-Middle Triassic formed the main cap rocks and are favorable for the accumulation and preservation of hydrocarbon.展开更多
Conventional geochemical approaches were utilized in the quantitative prediction of the proportions of mixed-source crude oils derived from the Es3 and ES4 members of the Paleogene Shahejie Formation. The mixed-source...Conventional geochemical approaches were utilized in the quantitative prediction of the proportions of mixed-source crude oils derived from the Es3 and ES4 members of the Paleogene Shahejie Formation. The mixed-source oils are accumulated in the middle interval of the Es3 member （Es3 M） in the Niuzhuang Sag, which is one of the sags where subtle traps are primarily of lenticular basin-floor turbidite sands within mudstones mostly developed in the Dongying Depression, Bohai Bay Basin. The result showed that about 18-92% of the mixed-source oils were derived from the Es4 source rocks with an average of 55-60%）. Reservoirs associated with deep faults appear to have much more Es4 genetic affinity oils. A high proportion of the Es4-derived oils discovered in the Es3 M subtle lithological traps in the Niuzhuang Sag have long migration distances. This suggests that surrounding source rocks might not necessarily control the hydrocarbon supply for subtle traps. Subtle migration pathway may play an important role in the vertical oil migration. The traditional concept of hydrocarbons accumulation in these tenticular turbidite sandstone traps within a short migration distance from the surrounding source rocks is not supported by this study. The present result is also consistent with our previous findings that immature oils in the Bamianhe Oilfield in the south slope of the Niuzhuang Sag were actually mixed-source oils mostly sourced from the Es4 in the depocenter of the Niuzhuang Sag, and the petroleum potential of the ES4 member in the Dongying Depression should therefore be re-evaluated.展开更多
Field investigation and seismic section explanation showed that the Longmen Mountain Thrust Belt has obvious differential deformation： zonation, segmentation and stratification. Zonation means that, from NW to NE, th...Field investigation and seismic section explanation showed that the Longmen Mountain Thrust Belt has obvious differential deformation： zonation, segmentation and stratification. Zonation means that, from NW to NE, the Longmen Mountain Thrust Belt can be divided into the Songpan- Garz~ Tectonic Belt, ductile deformation belt, base involved thrust belt, frontal fold-thrust belt, and foreland depression. Segmentation means that it can be divided into five segments from north to south： the northern segment, the Anxian Transfer Zone, the center segment, the Guanxian Transfer Zone and the southern segment. Stratification means that the detachment layers partition the structural styles in profile. The detachment layers in the Longmen Mountain Thrust Belt can be classified into three categories： the deep-level detachment layers, including the crust-mantle system detachment layer, intracrustal detachment layer, and Presinian system basal detachment layer; the middle-level detachment layers, including Cambrian-Ordovician detachment layer, Silurian detachment layer, etc.; and shallow-level detachment layers, including Upper Triassic Xujiahe Formation detachment layer and the Jurassic detachment layers. The multi-level detachment layers have a very important effect on the shaping and evolution of Longmen Mountain Thrust Belt.展开更多
The Triassic in the Longmengshan foreland basin is rich in oil and gas resources. Its reservoirs feature low-porosity, low-permeability, small pore throat, high water saturation, and strong heterogeneity. The existenc...The Triassic in the Longmengshan foreland basin is rich in oil and gas resources. Its reservoirs feature low-porosity, low-permeability, small pore throat, high water saturation, and strong heterogeneity. The existence of abnormally high pressure and various reservoir-cap combinations developed at different times provide favorable conditions for trapping oil and gas. Taking the theory of petroleum systems as a guide, and beginning with research on tectonics, sedimentary history, distribution and evolution of source rocks, reservoir evolution, hydraulic force distribution, and hydrocarbon migration, analysis and study of static factors like source rocks, reservoirs and cap rocks, and dynamic factors such as hydrocarbon generation, migration, and accumulation revealed the characteristics of the Upper Triassic petroleum system in western Sichuan province. The deepbasin gas in the central hydrocarbon kitchen of the Upper Triassic, structural-lithological combination traps on the surrounding slopes, and the structural traps of the Indo-Chinese-Yangshan paleohighs, are potential plays. The relatively well- developed fault zones in the southern segment of the Longmengshan foothill belt are favorable Jurassic gas plays. Pengshan-Xinjin, Qiongxi, and Dayi are recent exploration targets for Jurassic oil/gas reservoirs.展开更多
The Yong＇an-Meitai area is the focus of the present exploration in the Fushan Depression, Beibuwan Basin, South China Sea. All oils from this area are geochemically characterized by higher Pr/Ph ratio, higher proport...The Yong＇an-Meitai area is the focus of the present exploration in the Fushan Depression, Beibuwan Basin, South China Sea. All oils from this area are geochemically characterized by higher Pr/Ph ratio, higher proportion of heavy molecular weight hydrocarbons, and higher proportion of C29 regular steranes, which indicate that the organic matter of source rocks might have been deposited in an oxidizing palaeoenvironment and be dominated by higher plant organic matter input. The oil from E3w2 （the second member of Weizhou Fro. of the Oligocene） has a much higher density, relatively higher Pr/nC17 and Ph/nC18 ratios, and a ＂UCM--unresolved complex mixture＂ on gas chromatograms, which indicate that it has been slightly biodegraded. CPI and other terpane and sterane isomer ratios suggest they are all mature oils. The timing of oil charging in E3w2 and E2I1 （the first member of the Liushagang Fro. of the Eocene） determined by the homogenization temperatures of fluid inclusions and thermal evolution history are from 9-3 Ma and 8-3 Ma, respectively. Thus, the interpretation of E3w2 as a secondary reservoir is unlikely. The timing of oil charging is later than that of hydrocarbon generating and expulsion of Liushagang Fin. source rocks and trap formation, which is favorable for oil accumulation in this area. All molecular parameters that are used for tracing oil filling direction decrease with shallower burial depth, which suggests vertical oil migration. The widely occurring faults that penetrate through the source rocks of the Liushagang Fro. may serve as a fine oil charging conduit.展开更多
The geological background of the Subei basin is that of small relief subsidence, low geothermal gradient, multi-sedimentary hiatuses, intense reconstruction of the basin, frequent magmatic activity, and a unique combi...The geological background of the Subei basin is that of small relief subsidence, low geothermal gradient, multi-sedimentary hiatuses, intense reconstruction of the basin, frequent magmatic activity, and a unique combination of source rock and reservoir. This geological background resulted in characteristics such as many small fault blocks, multiple oil-bearing formations, scattered oil distribution, mini- to small-sized reservoirs, and difficulties in exploration. Aimed at such characteristics, an effective exploration strategy was adopted, and the oil reserves, production and economic benefits of the Jiangsu oilfield were significantly increased. This exploration strategy included understanding the hydrocarbon generation mechanism of source rocks, progressive evaluation of oil resources, comprehensive research on the faulted systems, the distribution of oil reservoirs and their controlling factors. The techniques used included integration of acquisition, processing and interpretation with 3-D seismics as the core technology, trap description and evaluation, directional drilling and cluster drilling, integration of cuttings logging, gas chromatographic logging and geochemical logging, and integration of early reservoir description and progressive exploration and development. This strategy could be guidance for other complex fault blocks.展开更多
The caprock is one of the key factors for a reservoir, especially for a gas reservoir. Whether the caprocks can block off the gas is of significance for the accumulation and preservation of the gas reservoir. In this ...The caprock is one of the key factors for a reservoir, especially for a gas reservoir. Whether the caprocks can block off the gas is of significance for the accumulation and preservation of the gas reservoir. In this paper, we use the Amplitude versus offset （AVO） seismic technique to determine the lateral extension of the hydrocarbon concentration sealing caprocks. The essence of this technique is to detect the variations of the reservoir bed physical properties by monitoring the variations of the reflection coefficient of seismic waves upon the interfaces between different lithologies. Generally it is used to indicate hydrocarbon directly. For the hydrocarbon concentration sealing caprocks, the change of hydrocarbon concentration may cause the change of physical properties of the caprocks. Therefore it is possible to evaluate the hydrocarbon concentration sealing ability of the caprocks by AVO. This paper presents a case study using AVO to determine the lateral extension of the hydrocarbon concentration sealing caprocks. The result shows that this method is helpful for the exploration of the region.展开更多
The generalized Pareto distribution model is a kind of hydrocarbon pool size probability statistical method for resource assessment. By introducing the time variable, resource conversion rate and the geological variab...The generalized Pareto distribution model is a kind of hydrocarbon pool size probability statistical method for resource assessment. By introducing the time variable, resource conversion rate and the geological variable, resource density, such model can describe not only different types of basins, but also any exploration samples at different phases of exploration, up to the parent population. It is a dynamic distribution model with profound geological significance and wide applicability. Its basic principle and the process of resource assessment are described in this paper. The petroleum accumulation system is an appropriate assessment unit for such method. The hydrocarbon resource structure of the Huanghua Depression in Bohai Bay Basin was predicted by using this model. The prediction results accord with the knowledge of exploration in the Huanghua Depression, and point out the remaining resources potential and structure of different petroleum accumulation systems, which are of great significance for guiding future exploration in the Huanghua Depression.展开更多
Compared Kuqa foreland basin with Persian Gulf Basin in development of salt layers, salt tectonics, and the relation between salt tectonics and hydrocarbon, it is concluded that the salt diapirs are relative to hydroc...Compared Kuqa foreland basin with Persian Gulf Basin in development of salt layers, salt tectonics, and the relation between salt tectonics and hydrocarbon, it is concluded that the salt diapirs are relative to hydrocarbon. Searching salt diapirs and related traps in Kuqa foreland basin is important. The forming mechanism of salt tectonic in Kuqa foreland basin is different from that of Hormuz Series, but similar to that of Lower Fars Series/Gachsaran Formation. Inspired by the role of salt tectonics of Lower Fars Series/Gaehsaran Formation in hydrocarbon accumulation, the authors considered that the exploration below salt layer should be enforced, and the traps below salt layer in the southern part of the Kuqa foreland basin would be found where salt layer is thicker. On the contrary, the traps should be found both above and below the salt layer in front of the northern mountain where salt layer is thin. The Triassic and Jurassic source rocks are rich in this area with great exploration prospective.展开更多
A common way to trace fluid flow and hydrocarbon accumulation is by studying the geochemistry of formation water. This paper focuses on the spacial distribution of the geochemical features of the formation water in th...A common way to trace fluid flow and hydrocarbon accumulation is by studying the geochemistry of formation water. This paper focuses on the spacial distribution of the geochemical features of the formation water in the Shiwu Rifled Basin and its indication of the water-rock interaction processes. The hydrodynamic field controls the spacial distribution of formation water. Due to the penetration of meteoric water, the salinity is below 4,500mg/L at the basin margin and the severely faulted central ridge and increases basin ward to 7,000-10,000mg/L. The vertical change of formation water can be divided into 3 zones, which correspond respectively to the free replacement zone （〈1,250m）, the obstructed replacement zone （1,250m-1,650m） and the lagged zone （〉 1,650m） in hydrodynamics. In the free replacement zone, the formation water is NaHCO3-type with its salinity increased to 10,000mg/L. The formation water in the obstructed replacement zone is Na2SO4-type with its salinity decreased to 5,000mg/L-7,000mg/L because of the dehydration of mud rocks. The formation water in the lagged zone is CaC12-type, but its salinity decreases sharply at a depth of 1,650m and then increases vertically downward to 10,000mg/L. This phenomenon can be best explained by the osmosis effect rather than the dehydration of mud rocks. The relationships between Cl^--HCO3^- and Na^＋＋K^＋-Ca^2＋ show that the initial water-rock interaction is the dissolution of NaCl and calcium-beating carbonate, causing an increase of Na^＋-K^＋-Ca^2＋-Cl^- and salinity. The succeeding water-rock interaction is albitization, which leads to a decrease of Na^＋ and an increase of Ca2＋ simultaneously, and generates CaCl2-type fluid. The above analysis shows that the geochemical evolution of formation water is governed by the water-rock interactions, while its spacial distribution is controlled by the hydrological conditions. The water-rock interaction processes are supported by other geological observations, suggesting that formation water geochemistry is a viable method to trace the fluid-rock interaction processes and has broad applications in practice.展开更多
Conventional f-x prediction filtering methods are based on an autoregressive model. The error section is first computed as a source noise but is removed as additive noise to obtain the signal, which results in an assu...Conventional f-x prediction filtering methods are based on an autoregressive model. The error section is first computed as a source noise but is removed as additive noise to obtain the signal, which results in an assumption inconsistency before and after filtering. In this paper, an autoregressive, moving-average model is employed to avoid the model inconsistency. Based on the ARMA model, a noncasual prediction filter is computed and a self-deconvolved projection filter is used for estimating additive noise in order to suppress random noise. The 1-D ARMA model is also extended to the 2-D spatial domain, which is the basis for noncasual spatial prediction filtering for random noise attenuation on 3-D seismic data. Synthetic and field data processing indicate this method can suppress random noise more effectively and preserve the signal simultaneously and does much better than other conventional prediction filtering methods.展开更多
Three series of sandbox modeling experiments were performed to study the fault-increment pattern in extensional basins. Experimental results showed that the tectonic action mode of boundaries and the shape of major bo...Three series of sandbox modeling experiments were performed to study the fault-increment pattern in extensional basins. Experimental results showed that the tectonic action mode of boundaries and the shape of major boundary faults control the formation and evolution of faults in extensional basins. In the process of extensional deformation, the increase in the number and length of faults was episodic, and every ＇episode＇ experienced three periods, strain-accumulation period, quick fault-increment period and strain-adjustment period. The more complex the shape of the boundary fault, the higher the strain increment each ＇episode＇ experienced. Different extensional modes resulted in different fault-increment patterns. The horizontal detachment extensional mode has the ＇linear＇ style of fault-increment pattern, while the extensional mode controlled by a listric fault has the ＇stepwise＇ style of fault-increment pattern, and the extensional mode controlled by a ramp-flat boundary fault has the ＇stepwise-linear＇ style of fault-increment pattern. These fault-increment patterns given above could provide a theoretical method of fault interpretation and fracture prediction in extensional basins.展开更多
In China, most oil fields are continental sedimentation with strong heterogeneity, which on one side makes the reservoir prospecting and development more difficult, but on the other side provides more space for search...In China, most oil fields are continental sedimentation with strong heterogeneity, which on one side makes the reservoir prospecting and development more difficult, but on the other side provides more space for searching residual oil in matured fields. Time-lapse seismic reservoir monitoring technique is one of most important techniques to define residual oil distribution. According to the demand for and development of time-lapse seismic reservoir monitoring in China, purposeless repeated acquisition time-lapse seismic data processing was studied. The four key steps in purposeless repeated acquisition time-lapse seismic data processing, including amplitude-preserved processing with relative consistency, rebinning, match filtering and difference calculation, were analyzed by combining theory and real seismic data processing. Meanwhile, quality control during real time-lapse seismic processing was emphasized.展开更多
The geochemical characteristics of crude oils from Zao\|Ⅴ oil measures in the Shenjiapu oilfield are systematically described in terms of the fractional composition of crude oils, GC characteristics of saturated hydr...The geochemical characteristics of crude oils from Zao\|Ⅴ oil measures in the Shenjiapu oilfield are systematically described in terms of the fractional composition of crude oils, GC characteristics of saturated hydrocarbon fraction of crude oils and the characteristics of their biomarkers. The depositional environment, type and evolution of the biological source are also discussed. All pieces of evidence such as low saturated hydrocarbon fraction, high resin and asphalt, high isoprenoid alkane, weak odd\|carbon number predominance (CPI ranging from \{1.23\} to \{1.29\}, OEP ranging from \{1.14\} to \{1.16\}) and low sterane and terpane maturity parameters show these crude oils are immature oils. Low Pr/Ph ratios (\{0.66\}-\{0.88\}) and high gammacerance/C\-\{31\} hopane ratios (\{0.59\}-\{0.86\}) indicate the source rocks were formed in a slightly saline to brackish reducing lake depositional environment. Gas chromatographic characteristics of the saturated hydrocarbon fraction and the predominance of C\-\{30\} hopane in terpane series and C\-\{29\} sterane in sterane series indicate the biological source of the crude oils is composed mainly of bacterial and algal organic matter, and some algae are perhaps the main contributor of organic matter to the source rocks.展开更多
Ordovician fracture-cavity carbonate reservoir beds are the major type of producing formations in the Tahe oilfield, Tarim Basin. The seismic responses of these beds clearly changes depending on the different distance...Ordovician fracture-cavity carbonate reservoir beds are the major type of producing formations in the Tahe oilfield, Tarim Basin. The seismic responses of these beds clearly changes depending on the different distance of the fracture-cavity reservoir bed from the top of the section. The seismic reflection becomes weak or is absent when the fracture-cavity reservoir beds are less than 20 ms below the top Ordovician. The effect on top Ordovician reflection became weaker with deeper burial of fracture-cavity reservoir beds but the developed deep fracture-cavity reservoir beds caused stronger reflection in the interior of the Ordovician. This interior reflection can be divided into strong long-axis, irregular and bead string reflections, and was present 80 ms below the top Ordovician. Aimed at understanding reflection characteristics, the spectral decomposition technique, which uses frequency to ＂tune-in＂ bed thickness, was used to predict Ordovician fracture-cavity carbonate formations in the Tahe oilfield. Through finely adjusting the processing parameters of spectral decomposition, it was found that the slice at 30 Hz of the tuned data cube can best represent reservoir bed development. Two large N-S-trending strong reflection belts in the mid-western part of the study area along wells TK440- TK427-TK417B and in the eastern part along wells TK404-TK409 were observed distinctly on the 30 Hz slice and 4-D time-frequency data cube carving. A small N-S trending reflection belt in the southern part along wells T403-TK446B was also clearly identified. The predicted reservoir bed development area coincides with the fracture-cavities connection area confirmed by drilling pressure testing results. Deep karst cavities occur basically in three reservoir bed-development belts identified by the Ordovician interior strong reflection. Spectral decomposition proved to be a useful technique in identifying fracture-cavity reservoir beds.展开更多
Based on the pore cast and cathodolumines-cence thin sections, diagenesis process, source rock matura-tion history, structural evolution and reservoir qualitycharacteristics, the points of view that the porosities of ...Based on the pore cast and cathodolumines-cence thin sections, diagenesis process, source rock matura-tion history, structural evolution and reservoir qualitycharacteristics, the points of view that the porosities of Pa-leozoic clastic eureservoirs in the platform of the Tarim Ba-sin are mainly secondary, and the dissolution plays anunignorable role in the formation of eureservoirs, are putforward. In this paper, a series of criteria for the recognitionof the secondary porosities, the occurrence extent and classi-fication of secondary porosity are introduced, and threekinds of dissolution mechanism-the aluminosilicate dis-solution, the silicon dioxide dissolution and the carbonatedissolution-to generate the secondary porosity are comeup with. The formation, distribution, preservation and dis-appearance of eureservoirs are controlled by the paleo-structural framework and evolution, and hydrocarbon fillingand discharging. Paleostructural framework manipulate themigration path and direction of the acid fluid so as to deter-mine the position and extent of the dissolution. Paleostruc-ture highs and continuous paleouplifts are in favor of devel-oping the secondary porosity. The hydrocarbon filling madethe secondary porosities preserved and the hydrocarbondischarging let the secondary porosities filled by later calciteor quartz overgrowth cements. Paleostructure highs andcontinuous paleouplifts during the maturation period ofCambrian, Ordovician and Carboniferous source rocks(corresponding to S, P and K) are main areas for eureservoirs developing.展开更多
Through field geological survey, the authors found that abundant thrust faults developed in the Longmen （龙门） Mountain thrust belt. These faults can be divided into thrust faults and strike-slip faults according to...Through field geological survey, the authors found that abundant thrust faults developed in the Longmen （龙门） Mountain thrust belt. These faults can be divided into thrust faults and strike-slip faults according to their formation mechanisms and characteristics. Furthermore, these faults can be graded into primary fault, secondary fault, third-level fault, and fourth-level fault according to their scale and role in the tectonic evolution of Longmen Mountain thrust belt. Each thrustfault is such as composed of several secondary faults, Qingchuan （青川）-Maowen （茂汶） fault zone is composed of Qiaozhuang （乔庄） fault, Qingxi （青溪） fault, Maowen fault, Ganyanggou （赶羊沟） fault, etc.. The Longmen Mountain thrust belt experienced early Indosinian movement, Anxian （安县） movement, Yanshan （燕山） movement, and Himalayan movement, and the faults formed gradually from north to south.展开更多
Basic and intermediate-acidic igneous rocks were developed during the late Hercynian in North Tarim basin. The geochemistry characteristics of the rocks show that basic volcanic rock has K2O/Na2O = 0.18-0.61 〈 1 and ...Basic and intermediate-acidic igneous rocks were developed during the late Hercynian in North Tarim basin. The geochemistry characteristics of the rocks show that basic volcanic rock has K2O/Na2O = 0.18-0.61 〈 1 and falls into a category of basalt of sodium system. The rocks contain enriched large-ion lithophile elements （LILE） （K, Rb, Ba, Th） and high-field strength elements （HFSE） （Nb, Ta, Ti, Zr, P）, with the magmatic material from the upper mantle. The intermediate-acidic volcanicrocks have σ = 1.91-2.96 〈 3.3, K2O/Na2O = 1.25-1.59 〉 1, as well as the enriched LILE and depleted HFSE （Nb, Ta, Ti, P）, presenting the same trace element compositions and characteristics as in the granitic rocks of South Tianshan Mt.; they are either shoshonitic igneous rocks or high-K calc-alkaline igneous rocks, with a distinct crust-derived component feature. The comprehensive analyses on the characteristics of the trace elements, the graphic tectonic discrimination, and the distribution features of the two types of igneous rocks show that they were formed under different tectonic settings and geodynamic environments： the basalt was formed in the active rifting period when the active mantle upwelling caused the thinning of lithosphere; the intermediateacidic volcanic-intrusive rock was formed in the island arc area of the active continental margin in North Tarim; the formation is associated with the plate subduction during the course of South Tianshan Ocean closure--the subduction of Middle Tianshan Mountain toward the Tarim plate. The basic and intermediate-acidic igneous rocks reveal a tectonic regime of extension-extrusion transition, which is significant in determining the key tectonic revolution period of North Tarim basin.展开更多
基金the National Natural Science Foundation of China(Grant No.40672143,40472107 and 40172076)the National Major Fundamental Research and Development Project(Grant No.2005CB422107 and G1999043305)+1 种基金Development Foundation of Key Laboratory for Hydrocarbon Accumulation of the Education Ministry(Grant No.2003-01)Project of Southern Exploration and Development Division Company,SINOPEC(2003-04).
文摘The Triassic Jialingjiang Formation and Leikoupo Formation are characterized by thick salt layers. Three tectono-stratigraphic sequences can be identified according to detachment layers of Lower-Middle Triassic salt beds in the northern Sichuan Basin, i.e. the sub-salt sequence composed of Sinian to the Lower Triassic Feixianguan Formation, the salt sequence of the Lower Triassic Jialingjiang Formation and Mid-Triassic Leikoupou Formation, and the supra-salt sequence composed of continental clastics of the Upper-Triassic Xujiahe Formation, Jurassic and Cretaceous. A series of specific structural styles, such as intensively deformed belt of basement-involved imbricated thrust belt, basement-involved and salt-detached superimposed deformed belt, buried salt-related detached belt, duplex, piling triangle zone and pop-up, developed in the northern Sichuan Basin. The relatively thin salt beds, associated with the structural deformation of the northern Sichuan Basin, might act as a large decollement layer. The deformation mechanisms in the northern Sichuan Basin included regional compression and shortening, plastic flow and detachment, tectonic upwelling and erosion, gravitational sliding and spreading. The source rocks in the northern Sichuan Basin are strata underlying the salt layer, such as the Cambrian, Silurian and Permian. The structural deformation related to the Triassic salt controlled the styles of traps for hydrocarbon. The formation and development of hydrocarbon traps in the northern Sichuan Basin might have a bearing upon the Lower-Middle Triassic salt sequences which were favorable to the hydrocarbon accumulation and preservation. The salt layers in the Lower-Middle Triassic formed the main cap rocks and are favorable for the accumulation and preservation of hydrocarbon.
基金the National Natural Science Foundation of China (Grant No.#40772077/D0206)a complimentary research project from the Key Laboratory for Hydrocarbon Accumulation Mechanism of the Ministry of Education (China University of Petroleum) (2001-2).
文摘Conventional geochemical approaches were utilized in the quantitative prediction of the proportions of mixed-source crude oils derived from the Es3 and ES4 members of the Paleogene Shahejie Formation. The mixed-source oils are accumulated in the middle interval of the Es3 member （Es3 M） in the Niuzhuang Sag, which is one of the sags where subtle traps are primarily of lenticular basin-floor turbidite sands within mudstones mostly developed in the Dongying Depression, Bohai Bay Basin. The result showed that about 18-92% of the mixed-source oils were derived from the Es4 source rocks with an average of 55-60%）. Reservoirs associated with deep faults appear to have much more Es4 genetic affinity oils. A high proportion of the Es4-derived oils discovered in the Es3 M subtle lithological traps in the Niuzhuang Sag have long migration distances. This suggests that surrounding source rocks might not necessarily control the hydrocarbon supply for subtle traps. Subtle migration pathway may play an important role in the vertical oil migration. The traditional concept of hydrocarbons accumulation in these tenticular turbidite sandstone traps within a short migration distance from the surrounding source rocks is not supported by this study. The present result is also consistent with our previous findings that immature oils in the Bamianhe Oilfield in the south slope of the Niuzhuang Sag were actually mixed-source oils mostly sourced from the Es4 in the depocenter of the Niuzhuang Sag, and the petroleum potential of the ES4 member in the Dongying Depression should therefore be re-evaluated.
基金support from:National Natural Science Foundation of China (Grant no.40672143,40472107,40172076)National Major Fundamental Research and Development Project (Grant no.2005CB422107,G1999043305)+1 种基金Development Foundation of Key Laboratory for Hydrocarbon Accumulation of Education Ministry (Grant no.2003-01)Project of Southern Exploration and Development Division Company,SINOPEC (2003-04).
文摘Field investigation and seismic section explanation showed that the Longmen Mountain Thrust Belt has obvious differential deformation： zonation, segmentation and stratification. Zonation means that, from NW to NE, the Longmen Mountain Thrust Belt can be divided into the Songpan- Garz~ Tectonic Belt, ductile deformation belt, base involved thrust belt, frontal fold-thrust belt, and foreland depression. Segmentation means that it can be divided into five segments from north to south： the northern segment, the Anxian Transfer Zone, the center segment, the Guanxian Transfer Zone and the southern segment. Stratification means that the detachment layers partition the structural styles in profile. The detachment layers in the Longmen Mountain Thrust Belt can be classified into three categories： the deep-level detachment layers, including the crust-mantle system detachment layer, intracrustal detachment layer, and Presinian system basal detachment layer; the middle-level detachment layers, including Cambrian-Ordovician detachment layer, Silurian detachment layer, etc.; and shallow-level detachment layers, including Upper Triassic Xujiahe Formation detachment layer and the Jurassic detachment layers. The multi-level detachment layers have a very important effect on the shaping and evolution of Longmen Mountain Thrust Belt.
文摘The Triassic in the Longmengshan foreland basin is rich in oil and gas resources. Its reservoirs feature low-porosity, low-permeability, small pore throat, high water saturation, and strong heterogeneity. The existence of abnormally high pressure and various reservoir-cap combinations developed at different times provide favorable conditions for trapping oil and gas. Taking the theory of petroleum systems as a guide, and beginning with research on tectonics, sedimentary history, distribution and evolution of source rocks, reservoir evolution, hydraulic force distribution, and hydrocarbon migration, analysis and study of static factors like source rocks, reservoirs and cap rocks, and dynamic factors such as hydrocarbon generation, migration, and accumulation revealed the characteristics of the Upper Triassic petroleum system in western Sichuan province. The deepbasin gas in the central hydrocarbon kitchen of the Upper Triassic, structural-lithological combination traps on the surrounding slopes, and the structural traps of the Indo-Chinese-Yangshan paleohighs, are potential plays. The relatively well- developed fault zones in the southern segment of the Longmengshan foothill belt are favorable Jurassic gas plays. Pengshan-Xinjin, Qiongxi, and Dayi are recent exploration targets for Jurassic oil/gas reservoirs.
基金This research was financially supported by the Natural Science Foundation of China(Grant No.40672093)CNPC Innovation Fund(07El001)the ESS-China Hydrocarborn Geoscience Collaboration Project under Natural Resources Canada's International 0pportunities Program.We extend our thanks to South 0il Exploration and Development Company of PetroChina for samples collection.
文摘The Yong＇an-Meitai area is the focus of the present exploration in the Fushan Depression, Beibuwan Basin, South China Sea. All oils from this area are geochemically characterized by higher Pr/Ph ratio, higher proportion of heavy molecular weight hydrocarbons, and higher proportion of C29 regular steranes, which indicate that the organic matter of source rocks might have been deposited in an oxidizing palaeoenvironment and be dominated by higher plant organic matter input. The oil from E3w2 （the second member of Weizhou Fro. of the Oligocene） has a much higher density, relatively higher Pr/nC17 and Ph/nC18 ratios, and a ＂UCM--unresolved complex mixture＂ on gas chromatograms, which indicate that it has been slightly biodegraded. CPI and other terpane and sterane isomer ratios suggest they are all mature oils. The timing of oil charging in E3w2 and E2I1 （the first member of the Liushagang Fro. of the Eocene） determined by the homogenization temperatures of fluid inclusions and thermal evolution history are from 9-3 Ma and 8-3 Ma, respectively. Thus, the interpretation of E3w2 as a secondary reservoir is unlikely. The timing of oil charging is later than that of hydrocarbon generating and expulsion of Liushagang Fin. source rocks and trap formation, which is favorable for oil accumulation in this area. All molecular parameters that are used for tracing oil filling direction decrease with shallower burial depth, which suggests vertical oil migration. The widely occurring faults that penetrate through the source rocks of the Liushagang Fro. may serve as a fine oil charging conduit.
文摘The geological background of the Subei basin is that of small relief subsidence, low geothermal gradient, multi-sedimentary hiatuses, intense reconstruction of the basin, frequent magmatic activity, and a unique combination of source rock and reservoir. This geological background resulted in characteristics such as many small fault blocks, multiple oil-bearing formations, scattered oil distribution, mini- to small-sized reservoirs, and difficulties in exploration. Aimed at such characteristics, an effective exploration strategy was adopted, and the oil reserves, production and economic benefits of the Jiangsu oilfield were significantly increased. This exploration strategy included understanding the hydrocarbon generation mechanism of source rocks, progressive evaluation of oil resources, comprehensive research on the faulted systems, the distribution of oil reservoirs and their controlling factors. The techniques used included integration of acquisition, processing and interpretation with 3-D seismics as the core technology, trap description and evaluation, directional drilling and cluster drilling, integration of cuttings logging, gas chromatographic logging and geochemical logging, and integration of early reservoir description and progressive exploration and development. This strategy could be guidance for other complex fault blocks.
文摘The caprock is one of the key factors for a reservoir, especially for a gas reservoir. Whether the caprocks can block off the gas is of significance for the accumulation and preservation of the gas reservoir. In this paper, we use the Amplitude versus offset （AVO） seismic technique to determine the lateral extension of the hydrocarbon concentration sealing caprocks. The essence of this technique is to detect the variations of the reservoir bed physical properties by monitoring the variations of the reflection coefficient of seismic waves upon the interfaces between different lithologies. Generally it is used to indicate hydrocarbon directly. For the hydrocarbon concentration sealing caprocks, the change of hydrocarbon concentration may cause the change of physical properties of the caprocks. Therefore it is possible to evaluate the hydrocarbon concentration sealing ability of the caprocks by AVO. This paper presents a case study using AVO to determine the lateral extension of the hydrocarbon concentration sealing caprocks. The result shows that this method is helpful for the exploration of the region.
文摘The generalized Pareto distribution model is a kind of hydrocarbon pool size probability statistical method for resource assessment. By introducing the time variable, resource conversion rate and the geological variable, resource density, such model can describe not only different types of basins, but also any exploration samples at different phases of exploration, up to the parent population. It is a dynamic distribution model with profound geological significance and wide applicability. Its basic principle and the process of resource assessment are described in this paper. The petroleum accumulation system is an appropriate assessment unit for such method. The hydrocarbon resource structure of the Huanghua Depression in Bohai Bay Basin was predicted by using this model. The prediction results accord with the knowledge of exploration in the Huanghua Depression, and point out the remaining resources potential and structure of different petroleum accumulation systems, which are of great significance for guiding future exploration in the Huanghua Depression.
文摘Compared Kuqa foreland basin with Persian Gulf Basin in development of salt layers, salt tectonics, and the relation between salt tectonics and hydrocarbon, it is concluded that the salt diapirs are relative to hydrocarbon. Searching salt diapirs and related traps in Kuqa foreland basin is important. The forming mechanism of salt tectonic in Kuqa foreland basin is different from that of Hormuz Series, but similar to that of Lower Fars Series/Gachsaran Formation. Inspired by the role of salt tectonics of Lower Fars Series/Gaehsaran Formation in hydrocarbon accumulation, the authors considered that the exploration below salt layer should be enforced, and the traps below salt layer in the southern part of the Kuqa foreland basin would be found where salt layer is thicker. On the contrary, the traps should be found both above and below the salt layer in front of the northern mountain where salt layer is thin. The Triassic and Jurassic source rocks are rich in this area with great exploration prospective.
文摘A common way to trace fluid flow and hydrocarbon accumulation is by studying the geochemistry of formation water. This paper focuses on the spacial distribution of the geochemical features of the formation water in the Shiwu Rifled Basin and its indication of the water-rock interaction processes. The hydrodynamic field controls the spacial distribution of formation water. Due to the penetration of meteoric water, the salinity is below 4,500mg/L at the basin margin and the severely faulted central ridge and increases basin ward to 7,000-10,000mg/L. The vertical change of formation water can be divided into 3 zones, which correspond respectively to the free replacement zone （〈1,250m）, the obstructed replacement zone （1,250m-1,650m） and the lagged zone （〉 1,650m） in hydrodynamics. In the free replacement zone, the formation water is NaHCO3-type with its salinity increased to 10,000mg/L. The formation water in the obstructed replacement zone is Na2SO4-type with its salinity decreased to 5,000mg/L-7,000mg/L because of the dehydration of mud rocks. The formation water in the lagged zone is CaC12-type, but its salinity decreases sharply at a depth of 1,650m and then increases vertically downward to 10,000mg/L. This phenomenon can be best explained by the osmosis effect rather than the dehydration of mud rocks. The relationships between Cl^--HCO3^- and Na^＋＋K^＋-Ca^2＋ show that the initial water-rock interaction is the dissolution of NaCl and calcium-beating carbonate, causing an increase of Na^＋-K^＋-Ca^2＋-Cl^- and salinity. The succeeding water-rock interaction is albitization, which leads to a decrease of Na^＋ and an increase of Ca2＋ simultaneously, and generates CaCl2-type fluid. The above analysis shows that the geochemical evolution of formation water is governed by the water-rock interactions, while its spacial distribution is controlled by the hydrological conditions. The water-rock interaction processes are supported by other geological observations, suggesting that formation water geochemistry is a viable method to trace the fluid-rock interaction processes and has broad applications in practice.
基金This research was financially supported by National Natural Science Foundation of China （Grant No. 40604016） and the National Hi-Tech Research and Development Program （863 Program） （Grants No. 2006AA09A102-09 and No. 2007AA06Z229）.
文摘Conventional f-x prediction filtering methods are based on an autoregressive model. The error section is first computed as a source noise but is removed as additive noise to obtain the signal, which results in an assumption inconsistency before and after filtering. In this paper, an autoregressive, moving-average model is employed to avoid the model inconsistency. Based on the ARMA model, a noncasual prediction filter is computed and a self-deconvolved projection filter is used for estimating additive noise in order to suppress random noise. The 1-D ARMA model is also extended to the 2-D spatial domain, which is the basis for noncasual spatial prediction filtering for random noise attenuation on 3-D seismic data. Synthetic and field data processing indicate this method can suppress random noise more effectively and preserve the signal simultaneously and does much better than other conventional prediction filtering methods.
文摘Three series of sandbox modeling experiments were performed to study the fault-increment pattern in extensional basins. Experimental results showed that the tectonic action mode of boundaries and the shape of major boundary faults control the formation and evolution of faults in extensional basins. In the process of extensional deformation, the increase in the number and length of faults was episodic, and every ＇episode＇ experienced three periods, strain-accumulation period, quick fault-increment period and strain-adjustment period. The more complex the shape of the boundary fault, the higher the strain increment each ＇episode＇ experienced. Different extensional modes resulted in different fault-increment patterns. The horizontal detachment extensional mode has the ＇linear＇ style of fault-increment pattern, while the extensional mode controlled by a listric fault has the ＇stepwise＇ style of fault-increment pattern, and the extensional mode controlled by a ramp-flat boundary fault has the ＇stepwise-linear＇ style of fault-increment pattern. These fault-increment patterns given above could provide a theoretical method of fault interpretation and fracture prediction in extensional basins.
文摘In China, most oil fields are continental sedimentation with strong heterogeneity, which on one side makes the reservoir prospecting and development more difficult, but on the other side provides more space for searching residual oil in matured fields. Time-lapse seismic reservoir monitoring technique is one of most important techniques to define residual oil distribution. According to the demand for and development of time-lapse seismic reservoir monitoring in China, purposeless repeated acquisition time-lapse seismic data processing was studied. The four key steps in purposeless repeated acquisition time-lapse seismic data processing, including amplitude-preserved processing with relative consistency, rebinning, match filtering and difference calculation, were analyzed by combining theory and real seismic data processing. Meanwhile, quality control during real time-lapse seismic processing was emphasized.
文摘The geochemical characteristics of crude oils from Zao\|Ⅴ oil measures in the Shenjiapu oilfield are systematically described in terms of the fractional composition of crude oils, GC characteristics of saturated hydrocarbon fraction of crude oils and the characteristics of their biomarkers. The depositional environment, type and evolution of the biological source are also discussed. All pieces of evidence such as low saturated hydrocarbon fraction, high resin and asphalt, high isoprenoid alkane, weak odd\|carbon number predominance (CPI ranging from \{1.23\} to \{1.29\}, OEP ranging from \{1.14\} to \{1.16\}) and low sterane and terpane maturity parameters show these crude oils are immature oils. Low Pr/Ph ratios (\{0.66\}-\{0.88\}) and high gammacerance/C\-\{31\} hopane ratios (\{0.59\}-\{0.86\}) indicate the source rocks were formed in a slightly saline to brackish reducing lake depositional environment. Gas chromatographic characteristics of the saturated hydrocarbon fraction and the predominance of C\-\{30\} hopane in terpane series and C\-\{29\} sterane in sterane series indicate the biological source of the crude oils is composed mainly of bacterial and algal organic matter, and some algae are perhaps the main contributor of organic matter to the source rocks.
文摘Ordovician fracture-cavity carbonate reservoir beds are the major type of producing formations in the Tahe oilfield, Tarim Basin. The seismic responses of these beds clearly changes depending on the different distance of the fracture-cavity reservoir bed from the top of the section. The seismic reflection becomes weak or is absent when the fracture-cavity reservoir beds are less than 20 ms below the top Ordovician. The effect on top Ordovician reflection became weaker with deeper burial of fracture-cavity reservoir beds but the developed deep fracture-cavity reservoir beds caused stronger reflection in the interior of the Ordovician. This interior reflection can be divided into strong long-axis, irregular and bead string reflections, and was present 80 ms below the top Ordovician. Aimed at understanding reflection characteristics, the spectral decomposition technique, which uses frequency to ＂tune-in＂ bed thickness, was used to predict Ordovician fracture-cavity carbonate formations in the Tahe oilfield. Through finely adjusting the processing parameters of spectral decomposition, it was found that the slice at 30 Hz of the tuned data cube can best represent reservoir bed development. Two large N-S-trending strong reflection belts in the mid-western part of the study area along wells TK440- TK427-TK417B and in the eastern part along wells TK404-TK409 were observed distinctly on the 30 Hz slice and 4-D time-frequency data cube carving. A small N-S trending reflection belt in the southern part along wells T403-TK446B was also clearly identified. The predicted reservoir bed development area coincides with the fracture-cavities connection area confirmed by drilling pressure testing results. Deep karst cavities occur basically in three reservoir bed-development belts identified by the Ordovician interior strong reflection. Spectral decomposition proved to be a useful technique in identifying fracture-cavity reservoir beds.
文摘Based on the pore cast and cathodolumines-cence thin sections, diagenesis process, source rock matura-tion history, structural evolution and reservoir qualitycharacteristics, the points of view that the porosities of Pa-leozoic clastic eureservoirs in the platform of the Tarim Ba-sin are mainly secondary, and the dissolution plays anunignorable role in the formation of eureservoirs, are putforward. In this paper, a series of criteria for the recognitionof the secondary porosities, the occurrence extent and classi-fication of secondary porosity are introduced, and threekinds of dissolution mechanism-the aluminosilicate dis-solution, the silicon dioxide dissolution and the carbonatedissolution-to generate the secondary porosity are comeup with. The formation, distribution, preservation and dis-appearance of eureservoirs are controlled by the paleo-structural framework and evolution, and hydrocarbon fillingand discharging. Paleostructural framework manipulate themigration path and direction of the acid fluid so as to deter-mine the position and extent of the dissolution. Paleostruc-ture highs and continuous paleouplifts are in favor of devel-oping the secondary porosity. The hydrocarbon filling madethe secondary porosities preserved and the hydrocarbondischarging let the secondary porosities filled by later calciteor quartz overgrowth cements. Paleostructure highs andcontinuous paleouplifts during the maturation period ofCambrian, Ordovician and Carboniferous source rocks(corresponding to S, P and K) are main areas for eureservoirs developing.
基金supported by the National Natural Science Foundation of China (Nos. 40672143, 40472107, 40172076)the National Basic Research Program of China (Nos. 2005CB422107, G1999043305)+1 种基金Development Foundation of Key Laboratory for Hydrocarbon Accumulation of the Ministry of Education of China (No. 2003-03)Project of the South-west Petroleum Natural Gas Subcompany of SINOPEC (No. GJ-51-0602)
文摘Through field geological survey, the authors found that abundant thrust faults developed in the Longmen （龙门） Mountain thrust belt. These faults can be divided into thrust faults and strike-slip faults according to their formation mechanisms and characteristics. Furthermore, these faults can be graded into primary fault, secondary fault, third-level fault, and fourth-level fault according to their scale and role in the tectonic evolution of Longmen Mountain thrust belt. Each thrustfault is such as composed of several secondary faults, Qingchuan （青川）-Maowen （茂汶） fault zone is composed of Qiaozhuang （乔庄） fault, Qingxi （青溪） fault, Maowen fault, Ganyanggou （赶羊沟） fault, etc.. The Longmen Mountain thrust belt experienced early Indosinian movement, Anxian （安县） movement, Yanshan （燕山） movement, and Himalayan movement, and the faults formed gradually from north to south.
基金supported by the National Natural Science Foundation of China (Nos. 40672143, 40472107, 40172076)the National Basic Research Program (Nos. 2005CB422107, G1999043305)Project of Northwest Oilfield Company, SINOPEC (KY-S-2006-014)
文摘Basic and intermediate-acidic igneous rocks were developed during the late Hercynian in North Tarim basin. The geochemistry characteristics of the rocks show that basic volcanic rock has K2O/Na2O = 0.18-0.61 〈 1 and falls into a category of basalt of sodium system. The rocks contain enriched large-ion lithophile elements （LILE） （K, Rb, Ba, Th） and high-field strength elements （HFSE） （Nb, Ta, Ti, Zr, P）, with the magmatic material from the upper mantle. The intermediate-acidic volcanicrocks have σ = 1.91-2.96 〈 3.3, K2O/Na2O = 1.25-1.59 〉 1, as well as the enriched LILE and depleted HFSE （Nb, Ta, Ti, P）, presenting the same trace element compositions and characteristics as in the granitic rocks of South Tianshan Mt.; they are either shoshonitic igneous rocks or high-K calc-alkaline igneous rocks, with a distinct crust-derived component feature. The comprehensive analyses on the characteristics of the trace elements, the graphic tectonic discrimination, and the distribution features of the two types of igneous rocks show that they were formed under different tectonic settings and geodynamic environments： the basalt was formed in the active rifting period when the active mantle upwelling caused the thinning of lithosphere; the intermediateacidic volcanic-intrusive rock was formed in the island arc area of the active continental margin in North Tarim; the formation is associated with the plate subduction during the course of South Tianshan Ocean closure--the subduction of Middle Tianshan Mountain toward the Tarim plate. The basic and intermediate-acidic igneous rocks reveal a tectonic regime of extension-extrusion transition, which is significant in determining the key tectonic revolution period of North Tarim basin.
