2005 Vol. 23, No. 2
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Display Method:
2005, 23(2): 187-193.
Abstract:
Located in the area between orogenic belt and craton, intracontinental foreland basin in Western China was formed by the intracontinental fold-thrust movement resulted from the long-distance effect of plate collision. Without marine source rocks and marine molasses that are always developed along the passive continentalmargin, the intracontinental foreland basin is different from the typical foreland basin in foreign countries to some extent. With abundant hydrocarbon resources, the intracontinental foreland basin has attracted increasing attention of petroleum geologists in recent years. Main differences between intracontinental foreland basin and typ ical foreland basin have been analyzed and main sedimentary characteristics of the intracontinental foreland basin have been proposed. During the fold-faulting episode, the superposition of coarse-grained sediments could form apron-shaped sedimentary body. While during the inactive period of the fold-thrustmovement, the well-developed coal bed andmudstone could form source rocks of high quality. However, during the whole process, the migration of depression center and the excursion between dep ression center and deposition center are common. According to the superposition style of deposits, the intracontinental foreland basin has been subdivided into step-forward, superposition and step-backward types and sedimentary sequence model for each type has been established. Finally, the hydrocarbon generation, accumulation and preservation condition of each type of basin have been discussed, which will be helpful to the hydrocarbon exp loration according to their respective sequence model and to the improvement of exploration efficiency.
Located in the area between orogenic belt and craton, intracontinental foreland basin in Western China was formed by the intracontinental fold-thrust movement resulted from the long-distance effect of plate collision. Without marine source rocks and marine molasses that are always developed along the passive continentalmargin, the intracontinental foreland basin is different from the typical foreland basin in foreign countries to some extent. With abundant hydrocarbon resources, the intracontinental foreland basin has attracted increasing attention of petroleum geologists in recent years. Main differences between intracontinental foreland basin and typ ical foreland basin have been analyzed and main sedimentary characteristics of the intracontinental foreland basin have been proposed. During the fold-faulting episode, the superposition of coarse-grained sediments could form apron-shaped sedimentary body. While during the inactive period of the fold-thrustmovement, the well-developed coal bed andmudstone could form source rocks of high quality. However, during the whole process, the migration of depression center and the excursion between dep ression center and deposition center are common. According to the superposition style of deposits, the intracontinental foreland basin has been subdivided into step-forward, superposition and step-backward types and sedimentary sequence model for each type has been established. Finally, the hydrocarbon generation, accumulation and preservation condition of each type of basin have been discussed, which will be helpful to the hydrocarbon exp loration according to their respective sequence model and to the improvement of exploration efficiency.
2005, 23(2): 203-209.
Abstract:
The Late Pleistocene Huguangyan Formation in Weizhou island, Beihai city, Guangxi consists of volcanic clastic rocks. Volcanic rocks develop near Huguangyan Formation. Near the crater, a series of syn-depositional deformation structures are developped in the Huguangyan Formation, which includes seismic micro2fractures ( tensile-shear, tensile, conjugated and ladder fractures), micro-corrugated laminations, sinking rockfall structures and sand-muddy veins. These structures are believed resulting from earthquake related to volcanic activity of the Late Pleistocene.
The Late Pleistocene Huguangyan Formation in Weizhou island, Beihai city, Guangxi consists of volcanic clastic rocks. Volcanic rocks develop near Huguangyan Formation. Near the crater, a series of syn-depositional deformation structures are developped in the Huguangyan Formation, which includes seismic micro2fractures ( tensile-shear, tensile, conjugated and ladder fractures), micro-corrugated laminations, sinking rockfall structures and sand-muddy veins. These structures are believed resulting from earthquake related to volcanic activity of the Late Pleistocene.
2005, 23(2): 218-224.
Abstract:
A series of gentle slope delta are developed in Yanchang Formation in Jiyuan Area of Shaanxi-Gansu-Ningxia Basin. The delta front in this area can be divided into mesa delta front and slop ing delta front. The deposition models of delta along gentle slop are proposed based on the strength of the current in distributary channel and the depth of water in the lake. According to the research of underwater distributary channel, recombination bars and mouth bar, we can establish the assorted scheme and discriminating characteristics. For example, the distributary channels are composed of truncated underwater distributary channels and underwater superposition channels. The rivermouth bars are composed of the integrated mouth bars and recombination bars. The recombination bars consist of mouse bars at the bottom and underwater distributary channels at the top, and it can be subdivide into up side deformity recombination bars, integral recombination bars and downside recombination bars. This type of compartmentation scheme can be helpful to identify and distributing prognosticate of high quality reservoir, and it can also serve to subdivide the flow unit in oil exploitation.
A series of gentle slope delta are developed in Yanchang Formation in Jiyuan Area of Shaanxi-Gansu-Ningxia Basin. The delta front in this area can be divided into mesa delta front and slop ing delta front. The deposition models of delta along gentle slop are proposed based on the strength of the current in distributary channel and the depth of water in the lake. According to the research of underwater distributary channel, recombination bars and mouth bar, we can establish the assorted scheme and discriminating characteristics. For example, the distributary channels are composed of truncated underwater distributary channels and underwater superposition channels. The rivermouth bars are composed of the integrated mouth bars and recombination bars. The recombination bars consist of mouse bars at the bottom and underwater distributary channels at the top, and it can be subdivide into up side deformity recombination bars, integral recombination bars and downside recombination bars. This type of compartmentation scheme can be helpful to identify and distributing prognosticate of high quality reservoir, and it can also serve to subdivide the flow unit in oil exploitation.
2005, 23(2): 232-239.
Abstract:
The Triassic reservoir sandstone was from the basin-floor fan to the coastal bar and the delta, and can be divided into eight third-order sequences in the Chuxiong basin during late Triassic. This paper, using depositional sequence stratigraphy and high-resolution sequence stratigraphy, using extended Simpon math, extended Simpon 3 /8 math and Trapezoidalmath, has studied the reservoir architecture and spatial distribution through measured sections.The reservoir-body of upper Triassic, showing successive thin from lower to upper, was sandstone and conglomerate.The southern and northern fan-bodies of the Pujiacun formation ( T3 p) thatwas 7162 km3 had not become connection.Although the northern sandstone and conglomerate hasworse connection, shorter extension and more extensive heterogeneity, the southern channel sandstone bodies have been larger and better connection. The sandstone and conglomerate of the Ganhaizi formation ( T3 s), which was 4175 km3, was oval distribution, more barrier layers and extensive heterogeneity in the north, and was circling distribution, weaker maro-heterogeneity in the south. The circling sand-stone body of the Shezi Formation ( T3 s) was 5036 km3, in which the connection of the lake sandstone bodywasworse than that of the channel sandstone body and the latterwas been characterized by more homogeneous
The Triassic reservoir sandstone was from the basin-floor fan to the coastal bar and the delta, and can be divided into eight third-order sequences in the Chuxiong basin during late Triassic. This paper, using depositional sequence stratigraphy and high-resolution sequence stratigraphy, using extended Simpon math, extended Simpon 3 /8 math and Trapezoidalmath, has studied the reservoir architecture and spatial distribution through measured sections.The reservoir-body of upper Triassic, showing successive thin from lower to upper, was sandstone and conglomerate.The southern and northern fan-bodies of the Pujiacun formation ( T3 p) thatwas 7162 km3 had not become connection.Although the northern sandstone and conglomerate hasworse connection, shorter extension and more extensive heterogeneity, the southern channel sandstone bodies have been larger and better connection. The sandstone and conglomerate of the Ganhaizi formation ( T3 s), which was 4175 km3, was oval distribution, more barrier layers and extensive heterogeneity in the north, and was circling distribution, weaker maro-heterogeneity in the south. The circling sand-stone body of the Shezi Formation ( T3 s) was 5036 km3, in which the connection of the lake sandstone bodywasworse than that of the channel sandstone body and the latterwas been characterized by more homogeneous
2005, 23(2): 248-254.
Abstract:
The braided delta front are developed in Yanchang Formation in Xifeng area of Shan-Gan-Ning basin,which is mainly composed of the submerged distributry channels and mouth bars. It can be divided into submerged distributary channels section, submerged distributary channels together with mouth bars and mouth bars section.Based on the research of submerged distributary channels and mouth bars, the abundant sandbodies assemblage can reflect different sedimentary environments. For instance, submerged distributary channels section is composed of trunk sandbodies,campaniform sandbodies and campaniform-trunk sandbodies etc. The relationship between the characteristics and quality of the reservoirs and their physical p roperty and oil - bearing property is analyzed and the law of oil and gas distribution in the area is described, which provides reliable basis for the further exp loration and development of the area.
The braided delta front are developed in Yanchang Formation in Xifeng area of Shan-Gan-Ning basin,which is mainly composed of the submerged distributry channels and mouth bars. It can be divided into submerged distributary channels section, submerged distributary channels together with mouth bars and mouth bars section.Based on the research of submerged distributary channels and mouth bars, the abundant sandbodies assemblage can reflect different sedimentary environments. For instance, submerged distributary channels section is composed of trunk sandbodies,campaniform sandbodies and campaniform-trunk sandbodies etc. The relationship between the characteristics and quality of the reservoirs and their physical p roperty and oil - bearing property is analyzed and the law of oil and gas distribution in the area is described, which provides reliable basis for the further exp loration and development of the area.
2005, 23(2): 260-267.
Abstract:
The Linxia basin is situated in the northeastern part of the Qinghai-Tibet Plateau, and it is a flexural basin bounded by mountains. The weathering and erosion materials that come from Plateau can be deposited in the Basin in the first place, the sediments of the basin completely record the history of the climatic changes brought by the up lift of the Qinghai-Tibet Plateau. Therefore, the sediments of the Linxia basin can sensitively indicate the up lifting processes of the Qinghai-Tibet Plateau and the climatic changes in a short period of time. Analytic consequences of the grain-size composition and the magnetic suscep tibility of the Neogene Red Clay in Linxia basin show: Since 8.2 Ma, climatic changes undergo Asian aridification periodic evolution and east Asian wintermonsoon secular reinforcement processes. During 8.2～7.4Ma, east Asian winter monsoon begins to form in this area, early stage Asian aridification results in the formation of eolian dust source, Neogene Red Clay begins to deposit in the basin, especially, aridity or semiaridity grassland environment and /or grassland environment with less forest offer favorable background for the Red Clay deposits. The east Asian winter monsoon that is gradually strengthened begins to influence the Loess Plateau in the east part of the Liupan mountain ( 7.4 ～6.8Ma), then, mass accumulations of the Red Clay start to deposit in the loess plateau. Meanwhile, the climate of the basin transforms semiaridification into semihumidity. From 6.8 Ma to 6.0Ma, the climate and the tectonics are fairly stable.During 5.9 ～5.3Ma, climatic changes undergo a period of small scope changes between the winter and summer monsoon intensity in Linxia basin, it indicates a dry wet and dry cool climatic environment. Between5.3Ma and 4.8Ma, the east Asia winter monsoon system prevails, aridification is the strongest in the basin evolution history from 8.2Ma to 4.0 Ma, climatic characteristics is cool and dry. The summer monsoon begins to strengthen and the climate becomeswarm and humid (4.8～4.0Ma). After 4.0Ma B. P, the Qinghai-Tibet Plateau begins to strongly up lift again, which results in the deposits of massive gravel conglomeration named Jishi Formation in the Linxia Basin.
The Linxia basin is situated in the northeastern part of the Qinghai-Tibet Plateau, and it is a flexural basin bounded by mountains. The weathering and erosion materials that come from Plateau can be deposited in the Basin in the first place, the sediments of the basin completely record the history of the climatic changes brought by the up lift of the Qinghai-Tibet Plateau. Therefore, the sediments of the Linxia basin can sensitively indicate the up lifting processes of the Qinghai-Tibet Plateau and the climatic changes in a short period of time. Analytic consequences of the grain-size composition and the magnetic suscep tibility of the Neogene Red Clay in Linxia basin show: Since 8.2 Ma, climatic changes undergo Asian aridification periodic evolution and east Asian wintermonsoon secular reinforcement processes. During 8.2～7.4Ma, east Asian winter monsoon begins to form in this area, early stage Asian aridification results in the formation of eolian dust source, Neogene Red Clay begins to deposit in the basin, especially, aridity or semiaridity grassland environment and /or grassland environment with less forest offer favorable background for the Red Clay deposits. The east Asian winter monsoon that is gradually strengthened begins to influence the Loess Plateau in the east part of the Liupan mountain ( 7.4 ～6.8Ma), then, mass accumulations of the Red Clay start to deposit in the loess plateau. Meanwhile, the climate of the basin transforms semiaridification into semihumidity. From 6.8 Ma to 6.0Ma, the climate and the tectonics are fairly stable.During 5.9 ～5.3Ma, climatic changes undergo a period of small scope changes between the winter and summer monsoon intensity in Linxia basin, it indicates a dry wet and dry cool climatic environment. Between5.3Ma and 4.8Ma, the east Asia winter monsoon system prevails, aridification is the strongest in the basin evolution history from 8.2Ma to 4.0 Ma, climatic characteristics is cool and dry. The summer monsoon begins to strengthen and the climate becomeswarm and humid (4.8～4.0Ma). After 4.0Ma B. P, the Qinghai-Tibet Plateau begins to strongly up lift again, which results in the deposits of massive gravel conglomeration named Jishi Formation in the Linxia Basin.
2005, 23(2): 275-283.
Abstract:
On the basis of the grain size data from the samp les of two bore holes in the Zhangzhou City, Fujian Province, and the stream channel facies belt and estuarine facies belt, the Quaternary sedimentary environment and its evolution are discussed in details. The grain size parameters of 91 sediment samples obtained from MS 22000 Laser Grain Size Analyzer have been illustrated in frequency curves, cumulative frequency curves on probability scale, and modal curves. For the imp lication of the grain size distribution, the results show that the segments of the modal curves are obvious and have concordance with the segment of the cumulative frequency curves on probability scale, so that modal curves have an important significance in explanation of hydrodynamic sorting. The four evolutional stages during the Quaternary in the Zhangzhou basin are recognized as follows: 1) the alluvial facies and pluvial facies of the Longhai Formation during the middle Late Pleistocene; 2) the alluvial facies of the Dongshan Formation during the late Late Pleistocene; 3) the bay milieu or estuarine facies of lower part of the Changle Formation in the early and middle Holocene in age; 4) the alluvial facies and pluvial facies of upper part of the Changle Formation in the late Holocene in age.
On the basis of the grain size data from the samp les of two bore holes in the Zhangzhou City, Fujian Province, and the stream channel facies belt and estuarine facies belt, the Quaternary sedimentary environment and its evolution are discussed in details. The grain size parameters of 91 sediment samples obtained from MS 22000 Laser Grain Size Analyzer have been illustrated in frequency curves, cumulative frequency curves on probability scale, and modal curves. For the imp lication of the grain size distribution, the results show that the segments of the modal curves are obvious and have concordance with the segment of the cumulative frequency curves on probability scale, so that modal curves have an important significance in explanation of hydrodynamic sorting. The four evolutional stages during the Quaternary in the Zhangzhou basin are recognized as follows: 1) the alluvial facies and pluvial facies of the Longhai Formation during the middle Late Pleistocene; 2) the alluvial facies of the Dongshan Formation during the late Late Pleistocene; 3) the bay milieu or estuarine facies of lower part of the Changle Formation in the early and middle Holocene in age; 4) the alluvial facies and pluvial facies of upper part of the Changle Formation in the late Holocene in age.
2005, 23(2): 291-296.
Abstract:
It is suggested that the remarkable changes ofmagnetic suscep tibility in sediments can be used as the distinguishing indicator of the relative ages of sediments and the spherical magnetic metallic waste, which is related to modem industry in sediments, may be used as the marker of determining ages by analyzing the relations of veins, magnetic suscep tibility and ferromagnetic minerals in sediments from Zhongshan warship and Yangtze water level and ferro- magnetic minerals carried by atmospheric pollution, as well as historical documents, in this paper. The evident increasing magnetic suscep tibility in sediments is considered as the increase of ferromagnetic minerals being caused by environmental changes. It is in 1959 that the spherical magnetic metallic waste is first found in sediments, which is corresponding to that Wuhan Company of Iron and Steel put into the river. It was among 1938 and 1958 when the magnetic suscep tibility in sediments are relatively low and after 1959 when the magnetic suscep tibility in sediments was evidently increased. It is concise in principle, convenient in practice and inexpensive in cost to use the dating method of combining magnetic characteristics of sedimentswith historical documents. The method can be used in investigations of great scale sedimentary environment in the crowded population regions in inland and will not be affected by the changes of sedimentary environment
It is suggested that the remarkable changes ofmagnetic suscep tibility in sediments can be used as the distinguishing indicator of the relative ages of sediments and the spherical magnetic metallic waste, which is related to modem industry in sediments, may be used as the marker of determining ages by analyzing the relations of veins, magnetic suscep tibility and ferromagnetic minerals in sediments from Zhongshan warship and Yangtze water level and ferro- magnetic minerals carried by atmospheric pollution, as well as historical documents, in this paper. The evident increasing magnetic suscep tibility in sediments is considered as the increase of ferromagnetic minerals being caused by environmental changes. It is in 1959 that the spherical magnetic metallic waste is first found in sediments, which is corresponding to that Wuhan Company of Iron and Steel put into the river. It was among 1938 and 1958 when the magnetic suscep tibility in sediments are relatively low and after 1959 when the magnetic suscep tibility in sediments was evidently increased. It is concise in principle, convenient in practice and inexpensive in cost to use the dating method of combining magnetic characteristics of sedimentswith historical documents. The method can be used in investigations of great scale sedimentary environment in the crowded population regions in inland and will not be affected by the changes of sedimentary environment
2005, 23(2): 303-309.
Abstract:
Dongying delta's sand body and its associated turbidite fans are the main reservoirs of Shahejie Three Formation in Dongying Sag. Based on the high resolution sequence stratigraphical theory, this paper analyzed the variety of base level cycles and its control on the development and evolvement ofDongying delta. Its high frequency sequence stackingmode is divided into three types. This paper also studied the variety of short term base level cycles and its effect on the form and distribution of turbidite fans which are related to Dongying delta, and indicate that the slope-moving turbidity fan which consisted of the main reservoirswere formed during rising stage of the base level. The distribution of slop-moving turbidity fan ismainly controlled by the variety of base level cycles as well depositional faults and depositional palaeogeomorphology.Vertically, slop-moving turbidity fans are located on the location where the middle term base levels transformed from rising stage to falling stage. On the plane, the slop-moving fans are distributed in the downthrow of depositional faults and the palaeogeomorphological lowlands between these faults.
Dongying delta's sand body and its associated turbidite fans are the main reservoirs of Shahejie Three Formation in Dongying Sag. Based on the high resolution sequence stratigraphical theory, this paper analyzed the variety of base level cycles and its control on the development and evolvement ofDongying delta. Its high frequency sequence stackingmode is divided into three types. This paper also studied the variety of short term base level cycles and its effect on the form and distribution of turbidite fans which are related to Dongying delta, and indicate that the slope-moving turbidity fan which consisted of the main reservoirswere formed during rising stage of the base level. The distribution of slop-moving turbidity fan ismainly controlled by the variety of base level cycles as well depositional faults and depositional palaeogeomorphology.Vertically, slop-moving turbidity fans are located on the location where the middle term base levels transformed from rising stage to falling stage. On the plane, the slop-moving fans are distributed in the downthrow of depositional faults and the palaeogeomorphological lowlands between these faults.
2005, 23(2): 316-322.
Abstract:
Sequence stratigraphy provided a theory and significant tool for the global or regional stratigraphic isochronous correlation, it was also suitable for karst events analysis and regional correlation of caves related to sea level changes. The main top ic for this paper is to discover the fundamentals in the intersecting domain between paleokarst and sequence stratigraphy through the study of the relationship between the sea level change and the cave formation sequence followed by the principle of the water table changed with sea level and the cave formation was only developed in the period of standing sea level. By the study of Yate ( in U. S. A. ) and Tahe ( in Tarim basin) oil field, outcrop of EmeiMountain, as well as the integrated analysis of previous study, 3 general models about the relationship between the sea level change and the cave formation sequence are p rovided including that one is for the multip le karst island lenses corresponding to sedimentary cycleswithin the sequence-stratigraphic framework in which developed a normal succession of cave formation ( the upper the younger, the lower the older) ; and the other two are for paleokarst in the continent carbonate blocks, in which it could develop the normal or reversed cave formation sequence followed by sea level intermissive rising or dropp ing. With the direct or indirect evidences, such as the started outcropping time of carbonate blocks, paleokarst environments and other geological conditions, the characteristics of karst and the deposits in the horizontal caves, indicating that the great cave system in the residue of Ordovician of Tahe oil field were developed in a sea level intermissive rising half cycle of 2-order sequence. The isochronous relationship of depositional sequence and cave can be app lied in dating the paleokarst events, p redicating the possible dep th of caves; it has significant value in minerals exp loration and engineering geology.
Sequence stratigraphy provided a theory and significant tool for the global or regional stratigraphic isochronous correlation, it was also suitable for karst events analysis and regional correlation of caves related to sea level changes. The main top ic for this paper is to discover the fundamentals in the intersecting domain between paleokarst and sequence stratigraphy through the study of the relationship between the sea level change and the cave formation sequence followed by the principle of the water table changed with sea level and the cave formation was only developed in the period of standing sea level. By the study of Yate ( in U. S. A. ) and Tahe ( in Tarim basin) oil field, outcrop of EmeiMountain, as well as the integrated analysis of previous study, 3 general models about the relationship between the sea level change and the cave formation sequence are p rovided including that one is for the multip le karst island lenses corresponding to sedimentary cycleswithin the sequence-stratigraphic framework in which developed a normal succession of cave formation ( the upper the younger, the lower the older) ; and the other two are for paleokarst in the continent carbonate blocks, in which it could develop the normal or reversed cave formation sequence followed by sea level intermissive rising or dropp ing. With the direct or indirect evidences, such as the started outcropping time of carbonate blocks, paleokarst environments and other geological conditions, the characteristics of karst and the deposits in the horizontal caves, indicating that the great cave system in the residue of Ordovician of Tahe oil field were developed in a sea level intermissive rising half cycle of 2-order sequence. The isochronous relationship of depositional sequence and cave can be app lied in dating the paleokarst events, p redicating the possible dep th of caves; it has significant value in minerals exp loration and engineering geology.
2005, 23(2): 329-336.
Abstract:
With the increasing demand of oil and gas resource, oil and gas exp loration have to expand to the deep zone. To reinforce the cognition of oil-gas distribution laws and its controlling factors is the key to achieve further in the deep zone. This article is based on the exp loration achievements and geological cognition over the past years in the deep zone in Biyang sag, Anpeng oil field, and the laws of oil and gas distribution and the main controlling factors are analyzed in details. It shows that oil and gas distribution is inhomogeneous vertically. It has been found that the deep layer pool of Anpeng oil field mainly was updip wedge out trap. In Formation Hetaoyuan Ⅲ member Ⅴsand layer is the most enriched with oil and gas, Ⅵ is less, Ⅶ and Ⅷ is the lest. In the plane, oil and gas gathersmainly along the axial lobe of nose structure near Well Bi185-Well Bi252 region. Sedimentary facies, diagenesis and structure are the main controlling factors to influence the distribution of oil and gas in this region. The site that is located on the eminence of nose structure, and far-source the underwater distributary channel and estuary bar experiencing the late dagenetic period B is the most promising for accumulation of oil and gas. Vertically, late diagenetic period B sand layer is advantageous for oil and gas gathering, while late diagenetic subperiod A3 sand layer is disadvantageous for oil and gas gathering
With the increasing demand of oil and gas resource, oil and gas exp loration have to expand to the deep zone. To reinforce the cognition of oil-gas distribution laws and its controlling factors is the key to achieve further in the deep zone. This article is based on the exp loration achievements and geological cognition over the past years in the deep zone in Biyang sag, Anpeng oil field, and the laws of oil and gas distribution and the main controlling factors are analyzed in details. It shows that oil and gas distribution is inhomogeneous vertically. It has been found that the deep layer pool of Anpeng oil field mainly was updip wedge out trap. In Formation Hetaoyuan Ⅲ member Ⅴsand layer is the most enriched with oil and gas, Ⅵ is less, Ⅶ and Ⅷ is the lest. In the plane, oil and gas gathersmainly along the axial lobe of nose structure near Well Bi185-Well Bi252 region. Sedimentary facies, diagenesis and structure are the main controlling factors to influence the distribution of oil and gas in this region. The site that is located on the eminence of nose structure, and far-source the underwater distributary channel and estuary bar experiencing the late dagenetic period B is the most promising for accumulation of oil and gas. Vertically, late diagenetic period B sand layer is advantageous for oil and gas gathering, while late diagenetic subperiod A3 sand layer is disadvantageous for oil and gas gathering
2005, 23(2): 346-353.
Abstract:
There are clear hydrocarbon accumulation features for Xiaermen Oilfield in BiyangDep ression of Nanxiang Basin, which changed upward from pure reservoirs inMember He3 and He2 to reservoirs with gas cap in the upper part of Member He2, and up to pure gas reservoirs in Member He2 and Liaozhuang. Oil-source correlation shows that hydrocarbon in the upper part migrated and accumulated upward through long distance vertical migration from the lower mature gas-oil. Alongwith fast drawdown of boundary fracture during deposition of sand group Ⅵ in Member He3, Xiaermen anticline structure came into being antithetic drag anticline structure together with deposition, but lifting am-plitude is not clear. This area was subjected to strong comp ression caused by early Himalayasmovement ( at the deposition last term of LiaozhuangMember), this caused Xiaermen ancline structure into fracture develop ing many trap types connected with faults. Correspondingly, this oilfield is characterized ofmulti-term reservoir-forming and modified reservoir-forming: (1) reservoir-forming took p lace in the paleo-reservoir-forming period at the position last term of Member He1 ; (2) reservoir-forming took p lace in the period of destruction of paleo-reservoir and began the filling of mature oil-gas at the deposition last term of MemberL iaozhuang; (3) reservoir-forming took p lace at the end of struc- ture-rifting period in the late deposition, enough oil-gas filling before the Quaternary deposition. Hydrocarbon reservoir formingmodes are that hydrocarbon laterallymigrates through channels in single sand body and slowly fill and accumulate in the early term, and during mid and last term hydrocarbon fast migrate, fill and accumulate into reservoir because of sharp increase in potential energy caused by differential lifting motion, and vertical fracture modification at the end of Liangzhuang deposition period.
There are clear hydrocarbon accumulation features for Xiaermen Oilfield in BiyangDep ression of Nanxiang Basin, which changed upward from pure reservoirs inMember He3 and He2 to reservoirs with gas cap in the upper part of Member He2, and up to pure gas reservoirs in Member He2 and Liaozhuang. Oil-source correlation shows that hydrocarbon in the upper part migrated and accumulated upward through long distance vertical migration from the lower mature gas-oil. Alongwith fast drawdown of boundary fracture during deposition of sand group Ⅵ in Member He3, Xiaermen anticline structure came into being antithetic drag anticline structure together with deposition, but lifting am-plitude is not clear. This area was subjected to strong comp ression caused by early Himalayasmovement ( at the deposition last term of LiaozhuangMember), this caused Xiaermen ancline structure into fracture develop ing many trap types connected with faults. Correspondingly, this oilfield is characterized ofmulti-term reservoir-forming and modified reservoir-forming: (1) reservoir-forming took p lace in the paleo-reservoir-forming period at the position last term of Member He1 ; (2) reservoir-forming took p lace in the period of destruction of paleo-reservoir and began the filling of mature oil-gas at the deposition last term of MemberL iaozhuang; (3) reservoir-forming took p lace at the end of struc- ture-rifting period in the late deposition, enough oil-gas filling before the Quaternary deposition. Hydrocarbon reservoir formingmodes are that hydrocarbon laterallymigrates through channels in single sand body and slowly fill and accumulate in the early term, and during mid and last term hydrocarbon fast migrate, fill and accumulate into reservoir because of sharp increase in potential energy caused by differential lifting motion, and vertical fracture modification at the end of Liangzhuang deposition period.
2005, 23(2): 361-366.
Abstract:
The characteristic for the thermal evolution of aromatic maturity parameter, such as alkyl dibenzothio-phenes, dehydroxytocopherol and triaromatic-sterane series compounds have been discussed on the basis of GC-MS analysis for the crude oil in Huzhuangji-Qingzuji oil field in west slope of Dongpu depression. The distribution characteristics of aromatic chromatography, the ratio of β/γdehydroxytocopherol,4-/1-MDBT, 2,4- /1,4-DMDBT, C20 / (C20 +C26 ) TAS and the content of triaromatic-sterane series all suggest the crude oil distributed in second step structural derived from low maturity source rocks, whereas the crude oil distributed in Changyuan fault zone and the first step structural derived from maturity source rocks.
The characteristic for the thermal evolution of aromatic maturity parameter, such as alkyl dibenzothio-phenes, dehydroxytocopherol and triaromatic-sterane series compounds have been discussed on the basis of GC-MS analysis for the crude oil in Huzhuangji-Qingzuji oil field in west slope of Dongpu depression. The distribution characteristics of aromatic chromatography, the ratio of β/γdehydroxytocopherol,4-/1-MDBT, 2,4- /1,4-DMDBT, C20 / (C20 +C26 ) TAS and the content of triaromatic-sterane series all suggest the crude oil distributed in second step structural derived from low maturity source rocks, whereas the crude oil distributed in Changyuan fault zone and the first step structural derived from maturity source rocks.
2005, 23(2): 194-202.
Abstract:
The Jurassic is one of significant oil-bearing strata in Junggar basin with relatively well-reserved sequences, various sedimentary facies and diversiform depositional systems. Based on outcrop profiles, well data, logging data and seismic data, the Jurassic can be divided into seven sequences consisted of alluvial fan, stream, delta,fan delta, lacustrine and swamp facies which assemblaged in the tracts orderly. Research on p rovenance and lithofacies paleogeography indicates that there were eight sedimentary systems in the Jurassic in the Juggar basin, i. e., alluvial fan2braided stream-meandering stream-delta-lacustrine depositional system off KalamayMountains, delta fan-la-custrine depositional system in Wulungu, braided stream-meandering stream-delta-lacustrine depositional system off Delun Mountains, alluvial fan-braided stream-delta-lacustrine depositional system off Halaalate Mountains, alluvial fan-braided stream-delta-lacustrine depositional system in Cheguai, meandering stream-delta-lacustrine depositional system off Sikeshu Mountains, alluvial fan-braided stream-delta-lacustrine depositional system off Yilinhebier Mountains, meandering stream-delta-lacustrine depositional system offBogedaMountains. Among the eight depositional systems the depositional system off KalamayMountains was well developed in some sequences. These depositional systems controlled the favorable reservoir development of the Jurassic in Juggar Basin
The Jurassic is one of significant oil-bearing strata in Junggar basin with relatively well-reserved sequences, various sedimentary facies and diversiform depositional systems. Based on outcrop profiles, well data, logging data and seismic data, the Jurassic can be divided into seven sequences consisted of alluvial fan, stream, delta,fan delta, lacustrine and swamp facies which assemblaged in the tracts orderly. Research on p rovenance and lithofacies paleogeography indicates that there were eight sedimentary systems in the Jurassic in the Juggar basin, i. e., alluvial fan2braided stream-meandering stream-delta-lacustrine depositional system off KalamayMountains, delta fan-la-custrine depositional system in Wulungu, braided stream-meandering stream-delta-lacustrine depositional system off Delun Mountains, alluvial fan-braided stream-delta-lacustrine depositional system off Halaalate Mountains, alluvial fan-braided stream-delta-lacustrine depositional system in Cheguai, meandering stream-delta-lacustrine depositional system off Sikeshu Mountains, alluvial fan-braided stream-delta-lacustrine depositional system off Yilinhebier Mountains, meandering stream-delta-lacustrine depositional system offBogedaMountains. Among the eight depositional systems the depositional system off KalamayMountains was well developed in some sequences. These depositional systems controlled the favorable reservoir development of the Jurassic in Juggar Basin
2005, 23(2): 210-217.
Abstract:
A continuous sedimentary record throughout Oligocene to Miocene was discovered in the Tuotuohe Basin and is considered as the most integrated Oligo-Miocene record within the Tibetan Plateau, observed so far. The record includes the Oligocene Yaxicuo Group (31.3-23.8Ma) and the EarlyMioceneWudaoliang Group (31.3-23.8Ma)with a total thickness of 2393 m. The Yaxicuo Group consists mainly of violet and reddish brown, alternating sand-stone, siltstone, and mudstone. The Wudaoliang Group consists of lacustrine marl, intramicrite, and stromatolitic limestone. The Oligo-Miocene evolution of depositional environment of the Tuotuohe Basin underwent three periods:(1) earlyOligocene, mainly fluvial environmentwith mainly northward paleocurrrent and arid paleoclimate; (2) middle-late Oligocene, mainly lacustrine environment with mainly northeastward paleocurrent and warm and humid paleoclimate; (3) latest Oligocene to earlyMiocene, lacustrine environmentwith southward paleocurrent. During the third period, the lithology changed from alternating sandstone and mudstone of the upper Yaxicuo Group to mainly marl of theWudaoliang Group, suggesting the significant shift of sediment provenance, the stable trending of tectonic movement, and the aridity of paleoclimate condition. The Oligo-Miocene paleoclimate and tectonic evolution of the Tuotuohe Basin has disp layed its significance for understanding the early up lift of the Tibetan Plateau and the global climate change.
A continuous sedimentary record throughout Oligocene to Miocene was discovered in the Tuotuohe Basin and is considered as the most integrated Oligo-Miocene record within the Tibetan Plateau, observed so far. The record includes the Oligocene Yaxicuo Group (31.3-23.8Ma) and the EarlyMioceneWudaoliang Group (31.3-23.8Ma)with a total thickness of 2393 m. The Yaxicuo Group consists mainly of violet and reddish brown, alternating sand-stone, siltstone, and mudstone. The Wudaoliang Group consists of lacustrine marl, intramicrite, and stromatolitic limestone. The Oligo-Miocene evolution of depositional environment of the Tuotuohe Basin underwent three periods:(1) earlyOligocene, mainly fluvial environmentwith mainly northward paleocurrrent and arid paleoclimate; (2) middle-late Oligocene, mainly lacustrine environment with mainly northeastward paleocurrent and warm and humid paleoclimate; (3) latest Oligocene to earlyMiocene, lacustrine environmentwith southward paleocurrent. During the third period, the lithology changed from alternating sandstone and mudstone of the upper Yaxicuo Group to mainly marl of theWudaoliang Group, suggesting the significant shift of sediment provenance, the stable trending of tectonic movement, and the aridity of paleoclimate condition. The Oligo-Miocene paleoclimate and tectonic evolution of the Tuotuohe Basin has disp layed its significance for understanding the early up lift of the Tibetan Plateau and the global climate change.
2005, 23(2): 225-231.
Abstract:
The column of salt and gyp sum rock that are interbeded with black mudstone are developed in 3rd - 4thsub-member of Shaheje Formation of Lower Tertiary in Dongpu Dep ression. The black mud-stone was deposited in deep water, and the salt and gyp sum have been considered to be deposited in deepwater, too. In recently study, much mark of shallow water origin and evaporation are found, so the salt and gyp sum rock is considered of evaporation origin in Shallow water. That the black mudstone deposited in deep water interbedded with salt and gyp sum deposited in shallow water shows that during the sedimentation of 3th and 4th sub-member, the lake 1evel changes frequently.And it is because of the frequently change of lake 1evel, lowstand sandbodywas deposited in the sedimentation center in the direction of main sediments source, and the lowstand sandbody are the main reservoir of lithic oil pool
The column of salt and gyp sum rock that are interbeded with black mudstone are developed in 3rd - 4thsub-member of Shaheje Formation of Lower Tertiary in Dongpu Dep ression. The black mud-stone was deposited in deep water, and the salt and gyp sum have been considered to be deposited in deepwater, too. In recently study, much mark of shallow water origin and evaporation are found, so the salt and gyp sum rock is considered of evaporation origin in Shallow water. That the black mudstone deposited in deep water interbedded with salt and gyp sum deposited in shallow water shows that during the sedimentation of 3th and 4th sub-member, the lake 1evel changes frequently.And it is because of the frequently change of lake 1evel, lowstand sandbodywas deposited in the sedimentation center in the direction of main sediments source, and the lowstand sandbody are the main reservoir of lithic oil pool
2005, 23(2): 240-247.
Abstract:
This paper researched sedimentary styles and characteristics and discussed about Carboniferous sedimentary evolution of different stages, and, furthermore, analyzed characteristics and distribution of carboniferous clastic reservoir, and main controlling elements of geophysical attribution in order to carry out integrative estimation of reservoir in Bayanhot basin. Bayanhot basin has three depositional systems including lagoon-tidal flat, delta-fan delta and offshore shallow sea. Sedimentary evolution underwent three stages included in the evaporation sea bay of the earlier stage, shallow sea basin of the middle stage, extensive sea of the continentalmargin. Sand bar sub-facies of la- goon, front delta, sheet sandstone of offshore sea are the best sedimentary facies belts for the oil & gas accumulation
This paper researched sedimentary styles and characteristics and discussed about Carboniferous sedimentary evolution of different stages, and, furthermore, analyzed characteristics and distribution of carboniferous clastic reservoir, and main controlling elements of geophysical attribution in order to carry out integrative estimation of reservoir in Bayanhot basin. Bayanhot basin has three depositional systems including lagoon-tidal flat, delta-fan delta and offshore shallow sea. Sedimentary evolution underwent three stages included in the evaporation sea bay of the earlier stage, shallow sea basin of the middle stage, extensive sea of the continentalmargin. Sand bar sub-facies of la- goon, front delta, sheet sandstone of offshore sea are the best sedimentary facies belts for the oil & gas accumulation
2005, 23(2): 255-259.
Abstract:
The discovery of the large sedimentary-waves in deep water, caused the generations and the developments of internal-waves both home and abroad. The study shows that internal-waves can shape the sediments on seafloor and form orientating sedimentary structure. This kind of structure includes single-direction, double-directions and multi-directions. Maybe the returning structure is the special character of internal-waves. LaFond s' theory about the gener- ation of this kind of structure is widely accepted. The theory indicates that the velocity of bottom currents formed by internal-waves is reverse ratio to the distance between the density interface and the seabed. Return ing transport is the main trends of internal-waves because the trough ofwave is close to the seafloor. The research conc ludes that in ternal-waves are similar homology of surface-waves and the genera tion of the orientating sedimentary structure formed by internal-wave can be exp lained clearly by the general fluctuation theory successfully. The generationmechanism of orientating sed imentary structure is very important to the recognition of the internal- waves sediments
The discovery of the large sedimentary-waves in deep water, caused the generations and the developments of internal-waves both home and abroad. The study shows that internal-waves can shape the sediments on seafloor and form orientating sedimentary structure. This kind of structure includes single-direction, double-directions and multi-directions. Maybe the returning structure is the special character of internal-waves. LaFond s' theory about the gener- ation of this kind of structure is widely accepted. The theory indicates that the velocity of bottom currents formed by internal-waves is reverse ratio to the distance between the density interface and the seabed. Return ing transport is the main trends of internal-waves because the trough ofwave is close to the seafloor. The research conc ludes that in ternal-waves are similar homology of surface-waves and the genera tion of the orientating sedimentary structure formed by internal-wave can be exp lained clearly by the general fluctuation theory successfully. The generationmechanism of orientating sed imentary structure is very important to the recognition of the internal- waves sediments
2005, 23(2): 268-274.
Abstract:
The clay minerals and elements of the mud along the Min-Zhe Coast since 2 kaBP are analyzed. The provenance of the mud is from sediments of the Yangtze River according to the study of clayminerals. The same results are drawn based on cluster analysis and differentiation function ofmetal elements. It is about 83%～85% of the mud from sediments of the Yangtze River since 2 kaBP according to quantitative calculation, and sediments of the Yellow River did not reach the study area. It also shows that there is no apparent effect on the sedimentary environment and sediment provenance when the Yellow River changed its course and moved northward during the last 2 ka.
The clay minerals and elements of the mud along the Min-Zhe Coast since 2 kaBP are analyzed. The provenance of the mud is from sediments of the Yangtze River according to the study of clayminerals. The same results are drawn based on cluster analysis and differentiation function ofmetal elements. It is about 83%～85% of the mud from sediments of the Yangtze River since 2 kaBP according to quantitative calculation, and sediments of the Yellow River did not reach the study area. It also shows that there is no apparent effect on the sedimentary environment and sediment provenance when the Yellow River changed its course and moved northward during the last 2 ka.
2005, 23(2): 284-290.
Abstract:
The Quaternary outwash, characterized by the drip stone bounded by the gray and yellow shale and mud-stone, is discovered in theMang'ai depression of Qaidam basin. The drip stone is up to 4 cm ×12 cm with complicated compositions owing to the volcanic, metamorphic and sedimentary origin. The sporo-pollen analysis revealed that it is formed in Quaternary period, most probably Pleistocene epoch, coinciding with the Quaternary glacial epoch of West China although the detailed age is, as yet, uncertain. The strong evidence of outwash existed in theMang'ai dep ression is of great importance to the research on the evolution and paleoclimate, paleogeography of Qingzang plateau of Quaternary glacial epoch of China. Moreover, it reveals that a whole ice cover in the Quaternary does not cover the Qingzang plateau
The Quaternary outwash, characterized by the drip stone bounded by the gray and yellow shale and mud-stone, is discovered in theMang'ai depression of Qaidam basin. The drip stone is up to 4 cm ×12 cm with complicated compositions owing to the volcanic, metamorphic and sedimentary origin. The sporo-pollen analysis revealed that it is formed in Quaternary period, most probably Pleistocene epoch, coinciding with the Quaternary glacial epoch of West China although the detailed age is, as yet, uncertain. The strong evidence of outwash existed in theMang'ai dep ression is of great importance to the research on the evolution and paleoclimate, paleogeography of Qingzang plateau of Quaternary glacial epoch of China. Moreover, it reveals that a whole ice cover in the Quaternary does not cover the Qingzang plateau
2005, 23(2): 297-302.
Abstract:
There are three different concep tions about base-level that are base level of erosion, base level of deposition and stratigraphic datum, respectively. At present, the arguments still exist in the explanation and the app lication of base-level, especially bas-level seems amphibious in use. The exp lanation of the stratification base-level in the high-resolution sequence stratigraphy is analyzed in this paper, and, in particular, the portion focused on illustration about marine facies sedimentary environment is questioned. The author discussed the relation between accommodation space and stratigraphic datum. Accommodation space is the key conception in sequence stratigraphy and base-level is also important, so they are very significant to illustrate the mechanism of the formation of sequence. Base level of erosion, base level of deposition and stratigraphic datum are all potential energy levels, kinetic surfaces and are all variable, just differing from the criterion of analyses and the mechanism of formation. To illustrate the features of these three base-levels profoundly, more questions of quantitative research into base-level should be considered.
There are three different concep tions about base-level that are base level of erosion, base level of deposition and stratigraphic datum, respectively. At present, the arguments still exist in the explanation and the app lication of base-level, especially bas-level seems amphibious in use. The exp lanation of the stratification base-level in the high-resolution sequence stratigraphy is analyzed in this paper, and, in particular, the portion focused on illustration about marine facies sedimentary environment is questioned. The author discussed the relation between accommodation space and stratigraphic datum. Accommodation space is the key conception in sequence stratigraphy and base-level is also important, so they are very significant to illustrate the mechanism of the formation of sequence. Base level of erosion, base level of deposition and stratigraphic datum are all potential energy levels, kinetic surfaces and are all variable, just differing from the criterion of analyses and the mechanism of formation. To illustrate the features of these three base-levels profoundly, more questions of quantitative research into base-level should be considered.
2005, 23(2): 310-315.
Abstract:
There are many types of meter-scale cyclic-sequence developed in Ordovician of Tazhong area. They contain abundant information on structure, sea-level change and the accumulated action of sediment. On the basis of the previouswork, and combining region geological data and detailed observation as well as descrip tion of the rock column, the meter-scale cyclic-sequence in Ordovician of Tazhong area are subdivided into four types: ocean-semiocean L-M type、lower slope-deep water asymmetrical type, subtidal type and peritidal type. On the characters of facies serial and structure, the meter-scale cyclic-sequences have the character of reverse grain serial developed on the instantaneous submerge discontinuous surface, or have the character of reverse or correctitude grain serial developed on the instantaneous emerge discontinuous surface. They all behave serial and vertical congruence format in long cycle third-order sequence. The sedimentary velocity and forming cycle of the meter-scale cyclic-sequence developed in Ordovician of Tazhong area and the periodic changes ofMilankovitch cycles have evidence relativity. it is concluded that the development of the Ordovician meter-scale cyclic-sequence in Tazhong area is controlled by the high-frequency changes of sea-level, and the high-frequency changes of sea-level is controlled by the change of global climate and the melt and flow of the continental glacier, which controlled by the periodic changes of Milankovitch cycles
There are many types of meter-scale cyclic-sequence developed in Ordovician of Tazhong area. They contain abundant information on structure, sea-level change and the accumulated action of sediment. On the basis of the previouswork, and combining region geological data and detailed observation as well as descrip tion of the rock column, the meter-scale cyclic-sequence in Ordovician of Tazhong area are subdivided into four types: ocean-semiocean L-M type、lower slope-deep water asymmetrical type, subtidal type and peritidal type. On the characters of facies serial and structure, the meter-scale cyclic-sequences have the character of reverse grain serial developed on the instantaneous submerge discontinuous surface, or have the character of reverse or correctitude grain serial developed on the instantaneous emerge discontinuous surface. They all behave serial and vertical congruence format in long cycle third-order sequence. The sedimentary velocity and forming cycle of the meter-scale cyclic-sequence developed in Ordovician of Tazhong area and the periodic changes ofMilankovitch cycles have evidence relativity. it is concluded that the development of the Ordovician meter-scale cyclic-sequence in Tazhong area is controlled by the high-frequency changes of sea-level, and the high-frequency changes of sea-level is controlled by the change of global climate and the melt and flow of the continental glacier, which controlled by the periodic changes of Milankovitch cycles
2005, 23(2): 323-328.
Abstract:
Based on the kinetic model of hydrate crystallization from venting gas in gas vent system, the evolvement characteristics and the impacts on gas hydrate crystallization in the Bush Hill gas vent system in GC 185 of Gulf of Mexico were studied. The venting rates are fast ( gas flux q > 18.4 kg/m2-a) in the earlier stage of the gas vent system, mud volcano occurred on the seafloor, the vent gas has almost the same composition as the source gas, and the heaviest possible hydrates are crystallized near the surface. The venting rates are slow ( gas flux q < 0. 55 kg/m2-a)in the later stage, hydrate crystallization will not reach the sea floor, seep carbonate will be occurred on the seafloor.Between these extremes gas hydrate and seep community is developed on the seafloor of the gas vent system, and the vent and hydrate gas compositions, and the mass fraction of venting gas crystallized hydrate depend strongly on venting rate. Changes in vent and hydrate gas chemistry observed atmultip le submersible visits to the Bush Hill vent system suggest the variations of venting rates between different submersible visiting time and different locations over the last 10 years
Based on the kinetic model of hydrate crystallization from venting gas in gas vent system, the evolvement characteristics and the impacts on gas hydrate crystallization in the Bush Hill gas vent system in GC 185 of Gulf of Mexico were studied. The venting rates are fast ( gas flux q > 18.4 kg/m2-a) in the earlier stage of the gas vent system, mud volcano occurred on the seafloor, the vent gas has almost the same composition as the source gas, and the heaviest possible hydrates are crystallized near the surface. The venting rates are slow ( gas flux q < 0. 55 kg/m2-a)in the later stage, hydrate crystallization will not reach the sea floor, seep carbonate will be occurred on the seafloor.Between these extremes gas hydrate and seep community is developed on the seafloor of the gas vent system, and the vent and hydrate gas compositions, and the mass fraction of venting gas crystallized hydrate depend strongly on venting rate. Changes in vent and hydrate gas chemistry observed atmultip le submersible visits to the Bush Hill vent system suggest the variations of venting rates between different submersible visiting time and different locations over the last 10 years
2005, 23(2): 337-345.
Abstract:
Through the synthetically study on the homogenization temperature and occurrence in the authigenic minerals of fluid inclusions in the terrane between or above the coal beds in the Carboniferous-Permain in the Qinshui basin, Shanxi, three stages of expulsion of hydrocarbon from the coal bedswere known. Combiningwith the conclusion of basin evolution, it is deduced that the filling of hydrocarbon happened during J2, the early of K1 and K2 ～E1. In the early stage, coal beds produced coal-generating oil. The stages of expulsion of nature gas are corresponding with the phase of thermocatalysis and thermal cracking, respectively. So the coal-bed gas in the Qinshui basin is mostly composed of gas of thermocatalysis and thermal cracking. The extracted hydrocarbon residues of the coal and the sand-stones are app reciably different, because of difference of fractional distillation and the filling of different degrees of hydrocarbon in the coal beds and the sandstones.
Through the synthetically study on the homogenization temperature and occurrence in the authigenic minerals of fluid inclusions in the terrane between or above the coal beds in the Carboniferous-Permain in the Qinshui basin, Shanxi, three stages of expulsion of hydrocarbon from the coal bedswere known. Combiningwith the conclusion of basin evolution, it is deduced that the filling of hydrocarbon happened during J2, the early of K1 and K2 ～E1. In the early stage, coal beds produced coal-generating oil. The stages of expulsion of nature gas are corresponding with the phase of thermocatalysis and thermal cracking, respectively. So the coal-bed gas in the Qinshui basin is mostly composed of gas of thermocatalysis and thermal cracking. The extracted hydrocarbon residues of the coal and the sand-stones are app reciably different, because of difference of fractional distillation and the filling of different degrees of hydrocarbon in the coal beds and the sandstones.
2005, 23(2): 367-370.
Abstract:
Abnormal composition can, sometimes, be detected from the analytical results of geochemical samples.Based on those, the researcher could judge whether these samples have been contaminated or not by later pollution.Special experiments aimed at several key procedures responsible for polluting geochemical samples have been performed. The result shows that the geochemical samp les are very easy to be polluted during collection, package, transportation, pre-treatment and p reservation, etc. Owing to the similarity of some contaminations to real compositions of the analyzing samples, once polluted, it is very difficult to tell the difference between them and likely result in disturbance or even cover the real composition of those samples to mislead the research work and bring losses. Although some researchers are engaged in the specific study on this aspect, relative reports are seldom read, it seems still need more efforts to elucidate this process
Abnormal composition can, sometimes, be detected from the analytical results of geochemical samples.Based on those, the researcher could judge whether these samples have been contaminated or not by later pollution.Special experiments aimed at several key procedures responsible for polluting geochemical samples have been performed. The result shows that the geochemical samp les are very easy to be polluted during collection, package, transportation, pre-treatment and p reservation, etc. Owing to the similarity of some contaminations to real compositions of the analyzing samples, once polluted, it is very difficult to tell the difference between them and likely result in disturbance or even cover the real composition of those samples to mislead the research work and bring losses. Although some researchers are engaged in the specific study on this aspect, relative reports are seldom read, it seems still need more efforts to elucidate this process
