Based on the comprehensive analysis of core, thin section, logging and seismic data, this study carried out the identification and comparison of Permian Changxing Formation sequences, clarified the typical sedimentary...Based on the comprehensive analysis of core, thin section, logging and seismic data, this study carried out the identification and comparison of Permian Changxing Formation sequences, clarified the typical sedimentary architectures of intra-platform shoal, investigated the vertical and horizontal development and distribution of intra-platform shoal in each sequence, and thus established the sedimentary evolution model of shoal body. The study results are reflected in four aspects.First, there are two complete third-order sequences(SQ1 and SQ2) in Changxing Formation in central Sichuan Basin. SQ1 is generally thick in the north and thin in the south, and SQ2 shows a thickness differentiation trend of “two thicknesses and three thinnesses”. Second, the Changxing Formation in central Sichuan Basin mainly develops intra-platform shoal, inter-shoal sea and intra-platform depression subfacies. In the vertical direction, the intra-platform shoal mainly presents two typical sedimentary sequences: stable superposed and high-frequency interbedded. Third, the stable superimposed sedimentary sequence is developed in the shoal belt at the edge of intra-platform depression, which is composed of two shoal-forming periods and located in the highstand systems tracts(HSTs) of SQ1 and SQ2. The high-frequency interbedded sedimentary sequence is developed in the southern shoal belt of intra-platform depression, which is composed of four shoal-forming periods and mainly located in the HST of SQ2. Fourth, during the SQ1 deposition, the intra-platform shoal was mainly developed at the edge of the intra-platform depression on the north side of the study area, and the inter-shoal sea subfacies was mainly developed on the south side. During the SQ2 deposition, the intra-platform shoal was widely developed in the area, forming two nearly parallel intra-platform shoal belts. The study results provide direction and ideas for exploration of Changxing Formation intra-platform shoal reservoirs in central Sichuan Basin.展开更多
In a very gentle platform-margin paleogeographic environment, platform-margin reef flat facies carbonate reservoir rocks were developed in the Changxing Formation of Yuanba field. Later weak structural evolution and d...In a very gentle platform-margin paleogeographic environment, platform-margin reef flat facies carbonate reservoir rocks were developed in the Changxing Formation of Yuanba field. Later weak structural evolution and diagenetic evolution caused the Changxing Formation to form lithologic traps, with good reservoirs such as dissolved bioclastic dolostone and dissolved pore dolostone. The Changxing Formation gas reservoir is a pseudo-layered porous lithologic gas reservoir under pressure depletion drive, with high H2S and moderate CO2 contents. This paper predictes that the conducting system for the Changxing Formation gas reservoir is possibly composed of the pores and microfractures in the Changxing Formation reservoir, the top erosional surface of the Changxing Formation, as well as the micropores and microfractures in the underlying formations. The Changxing Formation reservoir has experienced 3 hydrocarbon charging stages. This paper suggests that diffusion is the major formation mechanism for this gas reservoir. In the Middle and Late Yanshanian, the Yuanba area entered the major gas charging stage. The gas migrated mainly through diffusion and with the assistance of seepage flow in small faults and microfractures from the source rocks and the other oil-bearing strata to the Changxing Formation carbonate reservoir rocks, forming lithologic gas pools. In the Himalayan Epoch, the lithologic traps were uplifted as a whole without strong modification or overlapping, and were favorable for gas preservation.展开更多
In order to discuss the relationship between dolomite reservoirs and diagenetic systems of the Changxing Formation, we studied carbon, oxygen and strontium stable isotopes, iron, manganese and strontium trace elements...In order to discuss the relationship between dolomite reservoirs and diagenetic systems of the Changxing Formation, we studied carbon, oxygen and strontium stable isotopes, iron, manganese and strontium trace elements and the Mg/Ca (mol%) ratio, dolomite order degree, and determined that burial dolomitization is the key to controlling the distribution of high quality dolomite reservoir in the Changxing Formation in the eastern Sichuan Basin. The dolomite of the Changxing Formation is divided into four diagenetic systems: (1) penecontemporaneous stage syngenetic brine diagenetic system, (2) early diagenetic stage strata seal brine diagenetic system, (3) middle-late diagenetic stage mixed hot brine diagenetic system and (4) tectonic uplift stage mixed hydrothermal fluid diagenetic system. New understanding of the controlling factors and distribution of dolomite reservoir development is discussed. Reef shoal facies belts controlled regional reservoir distribution and the scale of development. Burial dolomitization of a strata seal brine diagenetic system is the foundation of reservoir development, mainly developing pore reservoir. Burial dolomitization of mixed hot brine diagenetic system expanded the reservoir distribution and improved the reservoir quality, mainly developing pore-vug reservoir. Fracturing and dissolution of a mixed hydrothermal fluid diagenetic system is the key to improving the reservoir quality, mainly developing pore-vug-crack complex reservoirs.展开更多
The recent discovery of deep and ultra-deep gas reservoirs in the Permian Changxing Formation reefs, northeastern Sichuan Basin is a significant development in marine carbonate oil & gas exploration in China. Reef do...The recent discovery of deep and ultra-deep gas reservoirs in the Permian Changxing Formation reefs, northeastern Sichuan Basin is a significant development in marine carbonate oil & gas exploration in China. Reef dolomites and their origins have been major research topics for sedimentologists and oil & gas geologists. The petrography, trace element and isotope geochemistry of the reef dolomites indicated that the dolomites are characterized by low Sr and Mn contents, relatively low Fe contents, very similar δ13C and 6180 values and very different 87Sr/86Sr ratios. Although the calculated results of the fluid mixing suggested that a mixture with 85%-95% meteoric water and 50/o- 15% seawater seemed to be the dolomitizing fluids of the reef dolomites, the low Mn contents, relatively low Fe contents, high δ13c values and high homogenization temperatures of the dolomites did not support that there were large proportions of meteoric water in the dolomitization process, and the 87Sr/86Sr ratios which were close to coeval seawater also did not support the possibility of the mixture of deep-burial circulated fluids from clastic rocks. High temperature deep-burial circulated seawater with low Mn and Fe contents, high Sr content and high δ13C values from the dissolution of widely distributed Triassic evaporites during the burial diagenetic processes (including dehydration of water-bearing evaporites) could have been the dolomitizing fluids of the reef dolomites.展开更多
Organic reef reservoirs in the platform margin of Kaijiang-Liangping trough in Damaoping area, Sichuan Basin are thin in single layer, fast in lateral variation, and have small P-impedance difference from the surround...Organic reef reservoirs in the platform margin of Kaijiang-Liangping trough in Damaoping area, Sichuan Basin are thin in single layer, fast in lateral variation, and have small P-impedance difference from the surrounding rock, it is difficult to identify and predict the reservoirs and fluid properties by conventional post-stack inversion. Through correlation analysis of core test data and logging P-S wave velocity, this work proposed a formula to calculate the shear wave velocity in different porosity ranges, and solved the issue that some wells in the study area have no S-wave data. AVO forward analysis reveals that formation porosity is the main factor affecting the variation of AVO type, the change of water saturation cannot affect the AVO type, but it has an effect on the change range of AVO. Through cross-plotting analysis of elastic parameters, it is found that fluid factor is a parameter sensitive to gas-bearing property of organic reef reservoir in the study area. By comparing results of post-stack impedance inversion, post-stack high frequency attenuation property, pre-stack simultaneous inversion and AVO anomaly analysis of angle gathers, it is found that the gas-bearing prediction of organic reef reservoirs by using fluid factor derived from simultaneous pre-stack inversion had the highest coincidence rate with actual drilling data. At last, according to the characteristics of fluid factor distribution, the favorable gas-bearing area of the organic reef reservoir in Changxing Formation was predicted, and the organic reef trap at the top of Changxing Formation in Block A of Damaoping area was sorted out as the next exploration target.展开更多
Bioclastic shoal reservoir in Changxing Formation of Jiannan area is characterized by small thickness and strong heterogeneity. The uncertainty of the reservoir distribution pattern has confined the effective developm...Bioclastic shoal reservoir in Changxing Formation of Jiannan area is characterized by small thickness and strong heterogeneity. The uncertainty of the reservoir distribution pattern has confined the effective development of this area, so the accurate bioclastic shoal reservoir prediction would be the key to achieve development breakthroughs. Based on drilling, well-log, seismic and core analysis data, this article conducted exquisite sequence stratigraphic classification and established isochronal regional stratigraphic framework of Changxing Formation in Jiannan area. The reservoir seismic corresponding features were determined by exquisite calibrating bioclastic shoal reservoir in Changxing Formation. Therefore, seismic processing methods, such as multiple attribute analysis and amplitude inversion, were applied to attain more reliable reservoir prediction results, which indicated the distribution of vertical reservoir in SSQ2, the IV sequence order and the distribution of horizontal reservoir around Well J43 and JZ1 in the platform margin of the study area.展开更多
In intracratnoic basins, the effect of strike-slip faults on sedimentary microfacies is generally underestimated due to their small scale. Based on the integration of core, well logs, and three-dimensional seismic dat...In intracratnoic basins, the effect of strike-slip faults on sedimentary microfacies is generally underestimated due to their small scale. Based on the integration of core, well logs, and three-dimensional seismic data, this study presents a comprehensive analysis of the Permian carbonate platform and strike-slip faults in the southwestern Kaijiang-Liangping trough of the Sichuan Basin. The relationship between strike-slip faults and Permian carbonate microfacies is investigated. The results reveals the existence of a NW-trending strike-slip fault zone along the platform margin, exhibiting clear segmentation. The western side of the study area exhibits a rimmed platform margin characterized by type I reefs, which corresponds to the presence of a large-scale strike-slip fault zone. In contrast, the eastern side is characterized by a norimmed and weak rimmed platform margin, accompanied by type II reefs, which align with smaller strike-slip fault zones. It was found that the strike-slip fault had some effects on the platform and reef-shoal complex of the Permain Changxing Formation. First, the platform was divided by strike-slip fault into three segments to show rimmed, week rimmed and norimmed platform. Second, reef-shoal complex devolped along the faulted high position in the strike-slip fault zone, and separated by faulted depression. Third, strike-slip faults can offset or migrated the reef-shoal complex and platform margin. Additionally, the thickness of the platform margin varies across strike-slip fault zone, which is related to the activity of strike-slip faults. The strike-slip faults affect the microfacies by controlling the pre-depositional paleotopography. This case suggests that the strike-slip faults play a crucial role in the diversity and distribution of carbonate microfacies in the intracratonic basin.展开更多
The Changxing (长兴) Formation has two sequences (sql and sq2) in the Panlongdong (盘龙洞) Section, Xuanhan (宣汉), northeastern Sichuan (四川). It belongs to the platform edge facies belt, rich in reefs and...The Changxing (长兴) Formation has two sequences (sql and sq2) in the Panlongdong (盘龙洞) Section, Xuanhan (宣汉), northeastern Sichuan (四川). It belongs to the platform edge facies belt, rich in reefs and banks, which were developed in the highstand system tract (HST) of sql and sq2, respectively. During third-order relative sea level dropping, the platform edge reef bank were mainly developed in the overall progradation parasequence sets. The platform edge reefs were developed in three phases, while platform edge banks in two phases. Outcrop observation and microscopic identification for platform egde reefs and banks in the section show that the three-phase-reefs are all composed of reef base and reef core, with string of tube sponge as the major reef-building organisms and fiber sponge, hydrazoan and bryozoans as the minor, while the reef-attached organisms mainly being fo- raminifera, brachiopod, echinoderm and ostracod. The first-phase-reef rock type is baffling reefs, the second phase baffling reefs and framework reefs assembles, the third phase framework reefs. Typically, the second phase reefs were developed with the maximum sedimentary scale and thickness, with the most abundant reef-building organisms and reef-attached organisms, showing best physical properties for reservoirs. The platform edge banks mainly consists of gravel debris and ooide grains, mostly dolomized. The dolomitizition in the second phase was relatively intense, favoring good reservoirs.展开更多
The Yuanba (元坝) area is considered another potential large-scale reef-bank gas field following the Puguang (普光) field. However, there are lots of difficulties on the spatial and temporal distribution of reef-b...The Yuanba (元坝) area is considered another potential large-scale reef-bank gas field following the Puguang (普光) field. However, there are lots of difficulties on the spatial and temporal distribution of reef-beach and the detailed prediction of the effective reservoir in the sequence stratigraphic framework. In this paper, based on the seismic data, well, log and core, we conduct a high-resolution sequence division and build an isochronal sequence stratigraphic framework for the Changxing (长兴) Formation by the methods of wavelet transformation, FMI, etc.. Then, the corresponding relationship among the lithologic facies, logging facies, seismic facies, seismic attribute facies and reservoir of Changxing Formation were established through well-seismic calibration and geological-geophysical modeling. Furthermore, detailed study on the spatial and temporal distribution of microfacies of the reef-beach was carried out by means of seismic attribute extraction. Meanwhile,combined with impedance inversion, the spatial distribution of porosity of reef-beach reservoir was predicted. The results show that the revolution of the reef-beach system contains three stages which are initial bioclastic bank establishment stage, reef development stage and exposure stage. Also, porosity inversion shows that the region with high value of porosity is located in the reef cap, fore reef and back reef.Seismic Sedimentology Study in the High-Resolution Sequence Framework展开更多
In Changxing (长兴) stage, Manyue (满月)-Honghua (红花) Section of Kaixian (开县), northeastern Sichuan (四川) Province was located in the platform-margin slope, which was the advantage area of reef-shoal de...In Changxing (长兴) stage, Manyue (满月)-Honghua (红花) Section of Kaixian (开县), northeastern Sichuan (四川) Province was located in the platform-margin slope, which was the advantage area of reef-shoal depositional system developing. The strata of Changxing Formation are continuously exposed on both Honghua Section and Manyue Section. Four and two depositional cycles ean be identified in Honghua Section and Manyue Section, respectively. They are all platform-margin reef-shoal deposits. Their lithologic associations have obvious sequence, which is as follows: micrite bioclast limestone, bafflestone, bindstone, framestone, and bioclast limestone, in order from below. The paleontological assemblages are controlled by water depth and genetic facies. Six paleontological as- semblages can be identified in Honghua Section and Manyue Section; they are coral-calcareous algaecalcareous sponge assemblage, calcareous sponge-calcareous algae assemblage, calcareous spongecalcareous algae-coral-bryozoan assemblage, calcareous sponge-calcareous algae-hydra assemblage, calcareous sponge-calcareous algae-hydra-bryozoan assemblage, and calcareous sponge-calcareous algae-hydra-bryozoan-coral assemblage. The study of lithologic associations and paleontological assemblages indicates that the water body shallowed upward in both the growth cycle of a single reef and the higher-grade depositional cycle. According to the water depth types of reef (bioherm) developing, three different reef-shoal depositional systems can be identified in study area: deep-water-type bioherm, transitional-type reef (bioherm), and more shallow-water-type reef.展开更多
The Upper Permian Changxing dolomite reservoirs serves as one of the most important gas and oil reservoirs in the NE Sichuan Basin. Determining the dolomitizing fluid's pathway is regarded as the key to solve the "d...The Upper Permian Changxing dolomite reservoirs serves as one of the most important gas and oil reservoirs in the NE Sichuan Basin. Determining the dolomitizing fluid's pathway is regarded as the key to solve the "dolomite problem" and further petroleum exploration. Outcrop samples from Upper Permian Changhsingian Panlongdong Section were studied using oxygen isotopic analysis, cathodoluminescence(CL) and major element analysis, in an attempt to determine the migration path way and properties of the dolomitizing fluid. Of the Changxing dolomite, the δ18O values ranged from-3.494‰ to-5.481‰, which decreased from the top layer to the bottom in the section; the MgO contents varied from 9.24% to 21.43%, CaO contents from 28.65% to 39.87%, the CaO/MgO ratio from 1.40 to 4.31 and the Mn O contents from 0.004% to 0.009 8%. The Mg O contents showed a downwardly decreasing trend in the section, while the Ca O/Mg O showed an opposite rule. All of the dolomites looked dull or dark when they were exposed to the electron beam of the cathodoluminescence device. None of the fine-to medium grained dolomite showed a banded structure. Given that dolomitizing fluid's salinity decreased during the dolomitization process in its pathway, we concluded that the dolomitizing fluid migrated downwardly in Changxing Formation after excluding the possibility of deep burial or meteoric-marine mixing-water influences. As the dolomitizing fluid's pathway has always been difficult to be determined in highly dolomitized Formation, this study showed an important application of oxygen isotope values in resolving this problem.展开更多
基金Supported by the PetroChina-Southwest Petroleum University Innovation Consortium Technology Cooperation Project (2020CX010000)。
文摘Based on the comprehensive analysis of core, thin section, logging and seismic data, this study carried out the identification and comparison of Permian Changxing Formation sequences, clarified the typical sedimentary architectures of intra-platform shoal, investigated the vertical and horizontal development and distribution of intra-platform shoal in each sequence, and thus established the sedimentary evolution model of shoal body. The study results are reflected in four aspects.First, there are two complete third-order sequences(SQ1 and SQ2) in Changxing Formation in central Sichuan Basin. SQ1 is generally thick in the north and thin in the south, and SQ2 shows a thickness differentiation trend of “two thicknesses and three thinnesses”. Second, the Changxing Formation in central Sichuan Basin mainly develops intra-platform shoal, inter-shoal sea and intra-platform depression subfacies. In the vertical direction, the intra-platform shoal mainly presents two typical sedimentary sequences: stable superposed and high-frequency interbedded. Third, the stable superimposed sedimentary sequence is developed in the shoal belt at the edge of intra-platform depression, which is composed of two shoal-forming periods and located in the highstand systems tracts(HSTs) of SQ1 and SQ2. The high-frequency interbedded sedimentary sequence is developed in the southern shoal belt of intra-platform depression, which is composed of four shoal-forming periods and mainly located in the HST of SQ2. Fourth, during the SQ1 deposition, the intra-platform shoal was mainly developed at the edge of the intra-platform depression on the north side of the study area, and the inter-shoal sea subfacies was mainly developed on the south side. During the SQ2 deposition, the intra-platform shoal was widely developed in the area, forming two nearly parallel intra-platform shoal belts. The study results provide direction and ideas for exploration of Changxing Formation intra-platform shoal reservoirs in central Sichuan Basin.
基金supported by the National Major Fundamental Research and Development project(No. 2005CB422100)the project of Southern Exploration Division Company,SINOPEC
文摘In a very gentle platform-margin paleogeographic environment, platform-margin reef flat facies carbonate reservoir rocks were developed in the Changxing Formation of Yuanba field. Later weak structural evolution and diagenetic evolution caused the Changxing Formation to form lithologic traps, with good reservoirs such as dissolved bioclastic dolostone and dissolved pore dolostone. The Changxing Formation gas reservoir is a pseudo-layered porous lithologic gas reservoir under pressure depletion drive, with high H2S and moderate CO2 contents. This paper predictes that the conducting system for the Changxing Formation gas reservoir is possibly composed of the pores and microfractures in the Changxing Formation reservoir, the top erosional surface of the Changxing Formation, as well as the micropores and microfractures in the underlying formations. The Changxing Formation reservoir has experienced 3 hydrocarbon charging stages. This paper suggests that diffusion is the major formation mechanism for this gas reservoir. In the Middle and Late Yanshanian, the Yuanba area entered the major gas charging stage. The gas migrated mainly through diffusion and with the assistance of seepage flow in small faults and microfractures from the source rocks and the other oil-bearing strata to the Changxing Formation carbonate reservoir rocks, forming lithologic gas pools. In the Himalayan Epoch, the lithologic traps were uplifted as a whole without strong modification or overlapping, and were favorable for gas preservation.
基金funded by PetroChina Southwest Oil and Gasfield Company Scientific and Technological Projects "The Research of Changxing Organic Reef Bioherm and Reservoir Development Characteristics at Kaijiang-Liangping East Trough" (Number XNYQT-XNS02-2007-TS-5777)
文摘In order to discuss the relationship between dolomite reservoirs and diagenetic systems of the Changxing Formation, we studied carbon, oxygen and strontium stable isotopes, iron, manganese and strontium trace elements and the Mg/Ca (mol%) ratio, dolomite order degree, and determined that burial dolomitization is the key to controlling the distribution of high quality dolomite reservoir in the Changxing Formation in the eastern Sichuan Basin. The dolomite of the Changxing Formation is divided into four diagenetic systems: (1) penecontemporaneous stage syngenetic brine diagenetic system, (2) early diagenetic stage strata seal brine diagenetic system, (3) middle-late diagenetic stage mixed hot brine diagenetic system and (4) tectonic uplift stage mixed hydrothermal fluid diagenetic system. New understanding of the controlling factors and distribution of dolomite reservoir development is discussed. Reef shoal facies belts controlled regional reservoir distribution and the scale of development. Burial dolomitization of a strata seal brine diagenetic system is the foundation of reservoir development, mainly developing pore reservoir. Burial dolomitization of mixed hot brine diagenetic system expanded the reservoir distribution and improved the reservoir quality, mainly developing pore-vug reservoir. Fracturing and dissolution of a mixed hydrothermal fluid diagenetic system is the key to improving the reservoir quality, mainly developing pore-vug-crack complex reservoirs.
基金supported by the National Natural Science Foundation (41172099,40839908)Research Fund for the Doctoral Program of Higher Education of China(20050616005)
文摘The recent discovery of deep and ultra-deep gas reservoirs in the Permian Changxing Formation reefs, northeastern Sichuan Basin is a significant development in marine carbonate oil & gas exploration in China. Reef dolomites and their origins have been major research topics for sedimentologists and oil & gas geologists. The petrography, trace element and isotope geochemistry of the reef dolomites indicated that the dolomites are characterized by low Sr and Mn contents, relatively low Fe contents, very similar δ13C and 6180 values and very different 87Sr/86Sr ratios. Although the calculated results of the fluid mixing suggested that a mixture with 85%-95% meteoric water and 50/o- 15% seawater seemed to be the dolomitizing fluids of the reef dolomites, the low Mn contents, relatively low Fe contents, high δ13c values and high homogenization temperatures of the dolomites did not support that there were large proportions of meteoric water in the dolomitization process, and the 87Sr/86Sr ratios which were close to coeval seawater also did not support the possibility of the mixture of deep-burial circulated fluids from clastic rocks. High temperature deep-burial circulated seawater with low Mn and Fe contents, high Sr content and high δ13C values from the dissolution of widely distributed Triassic evaporites during the burial diagenetic processes (including dehydration of water-bearing evaporites) could have been the dolomitizing fluids of the reef dolomites.
基金Supported by the National Natural Science Foundation of China(41430316)China National Science and Technology Major Project(2017ZX05008-004-008).
文摘Organic reef reservoirs in the platform margin of Kaijiang-Liangping trough in Damaoping area, Sichuan Basin are thin in single layer, fast in lateral variation, and have small P-impedance difference from the surrounding rock, it is difficult to identify and predict the reservoirs and fluid properties by conventional post-stack inversion. Through correlation analysis of core test data and logging P-S wave velocity, this work proposed a formula to calculate the shear wave velocity in different porosity ranges, and solved the issue that some wells in the study area have no S-wave data. AVO forward analysis reveals that formation porosity is the main factor affecting the variation of AVO type, the change of water saturation cannot affect the AVO type, but it has an effect on the change range of AVO. Through cross-plotting analysis of elastic parameters, it is found that fluid factor is a parameter sensitive to gas-bearing property of organic reef reservoir in the study area. By comparing results of post-stack impedance inversion, post-stack high frequency attenuation property, pre-stack simultaneous inversion and AVO anomaly analysis of angle gathers, it is found that the gas-bearing prediction of organic reef reservoirs by using fluid factor derived from simultaneous pre-stack inversion had the highest coincidence rate with actual drilling data. At last, according to the characteristics of fluid factor distribution, the favorable gas-bearing area of the organic reef reservoir in Changxing Formation was predicted, and the organic reef trap at the top of Changxing Formation in Block A of Damaoping area was sorted out as the next exploration target.
文摘Bioclastic shoal reservoir in Changxing Formation of Jiannan area is characterized by small thickness and strong heterogeneity. The uncertainty of the reservoir distribution pattern has confined the effective development of this area, so the accurate bioclastic shoal reservoir prediction would be the key to achieve development breakthroughs. Based on drilling, well-log, seismic and core analysis data, this article conducted exquisite sequence stratigraphic classification and established isochronal regional stratigraphic framework of Changxing Formation in Jiannan area. The reservoir seismic corresponding features were determined by exquisite calibrating bioclastic shoal reservoir in Changxing Formation. Therefore, seismic processing methods, such as multiple attribute analysis and amplitude inversion, were applied to attain more reliable reservoir prediction results, which indicated the distribution of vertical reservoir in SSQ2, the IV sequence order and the distribution of horizontal reservoir around Well J43 and JZ1 in the platform margin of the study area.
基金partly supported by the National Natural Science Foundation of China (Grant No. 4224100017)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance (Grant No.2020CX010300)。
文摘In intracratnoic basins, the effect of strike-slip faults on sedimentary microfacies is generally underestimated due to their small scale. Based on the integration of core, well logs, and three-dimensional seismic data, this study presents a comprehensive analysis of the Permian carbonate platform and strike-slip faults in the southwestern Kaijiang-Liangping trough of the Sichuan Basin. The relationship between strike-slip faults and Permian carbonate microfacies is investigated. The results reveals the existence of a NW-trending strike-slip fault zone along the platform margin, exhibiting clear segmentation. The western side of the study area exhibits a rimmed platform margin characterized by type I reefs, which corresponds to the presence of a large-scale strike-slip fault zone. In contrast, the eastern side is characterized by a norimmed and weak rimmed platform margin, accompanied by type II reefs, which align with smaller strike-slip fault zones. It was found that the strike-slip fault had some effects on the platform and reef-shoal complex of the Permain Changxing Formation. First, the platform was divided by strike-slip fault into three segments to show rimmed, week rimmed and norimmed platform. Second, reef-shoal complex devolped along the faulted high position in the strike-slip fault zone, and separated by faulted depression. Third, strike-slip faults can offset or migrated the reef-shoal complex and platform margin. Additionally, the thickness of the platform margin varies across strike-slip fault zone, which is related to the activity of strike-slip faults. The strike-slip faults affect the microfacies by controlling the pre-depositional paleotopography. This case suggests that the strike-slip faults play a crucial role in the diversity and distribution of carbonate microfacies in the intracratonic basin.
基金supported by the National Major Science and Technology Project of China (No. 2011ZX05007-002)
文摘The Changxing (长兴) Formation has two sequences (sql and sq2) in the Panlongdong (盘龙洞) Section, Xuanhan (宣汉), northeastern Sichuan (四川). It belongs to the platform edge facies belt, rich in reefs and banks, which were developed in the highstand system tract (HST) of sql and sq2, respectively. During third-order relative sea level dropping, the platform edge reef bank were mainly developed in the overall progradation parasequence sets. The platform edge reefs were developed in three phases, while platform edge banks in two phases. Outcrop observation and microscopic identification for platform egde reefs and banks in the section show that the three-phase-reefs are all composed of reef base and reef core, with string of tube sponge as the major reef-building organisms and fiber sponge, hydrazoan and bryozoans as the minor, while the reef-attached organisms mainly being fo- raminifera, brachiopod, echinoderm and ostracod. The first-phase-reef rock type is baffling reefs, the second phase baffling reefs and framework reefs assembles, the third phase framework reefs. Typically, the second phase reefs were developed with the maximum sedimentary scale and thickness, with the most abundant reef-building organisms and reef-attached organisms, showing best physical properties for reservoirs. The platform edge banks mainly consists of gravel debris and ooide grains, mostly dolomized. The dolomitizition in the second phase was relatively intense, favoring good reservoirs.
基金supported by the SINOPEC Group Project (No. 2009026324)
文摘The Yuanba (元坝) area is considered another potential large-scale reef-bank gas field following the Puguang (普光) field. However, there are lots of difficulties on the spatial and temporal distribution of reef-beach and the detailed prediction of the effective reservoir in the sequence stratigraphic framework. In this paper, based on the seismic data, well, log and core, we conduct a high-resolution sequence division and build an isochronal sequence stratigraphic framework for the Changxing (长兴) Formation by the methods of wavelet transformation, FMI, etc.. Then, the corresponding relationship among the lithologic facies, logging facies, seismic facies, seismic attribute facies and reservoir of Changxing Formation were established through well-seismic calibration and geological-geophysical modeling. Furthermore, detailed study on the spatial and temporal distribution of microfacies of the reef-beach was carried out by means of seismic attribute extraction. Meanwhile,combined with impedance inversion, the spatial distribution of porosity of reef-beach reservoir was predicted. The results show that the revolution of the reef-beach system contains three stages which are initial bioclastic bank establishment stage, reef development stage and exposure stage. Also, porosity inversion shows that the region with high value of porosity is located in the reef cap, fore reef and back reef.Seismic Sedimentology Study in the High-Resolution Sequence Framework
基金supported by the SINOPEC Forward Looking Projects of China (Nos. YPH08114 and 2009026324)
文摘In Changxing (长兴) stage, Manyue (满月)-Honghua (红花) Section of Kaixian (开县), northeastern Sichuan (四川) Province was located in the platform-margin slope, which was the advantage area of reef-shoal depositional system developing. The strata of Changxing Formation are continuously exposed on both Honghua Section and Manyue Section. Four and two depositional cycles ean be identified in Honghua Section and Manyue Section, respectively. They are all platform-margin reef-shoal deposits. Their lithologic associations have obvious sequence, which is as follows: micrite bioclast limestone, bafflestone, bindstone, framestone, and bioclast limestone, in order from below. The paleontological assemblages are controlled by water depth and genetic facies. Six paleontological as- semblages can be identified in Honghua Section and Manyue Section; they are coral-calcareous algaecalcareous sponge assemblage, calcareous sponge-calcareous algae assemblage, calcareous spongecalcareous algae-coral-bryozoan assemblage, calcareous sponge-calcareous algae-hydra assemblage, calcareous sponge-calcareous algae-hydra-bryozoan assemblage, and calcareous sponge-calcareous algae-hydra-bryozoan-coral assemblage. The study of lithologic associations and paleontological assemblages indicates that the water body shallowed upward in both the growth cycle of a single reef and the higher-grade depositional cycle. According to the water depth types of reef (bioherm) developing, three different reef-shoal depositional systems can be identified in study area: deep-water-type bioherm, transitional-type reef (bioherm), and more shallow-water-type reef.
基金supported by the National Natural Science Foundation of China (Nos.40472015, 40802001, and 41372121)the State Key Laboratory of Oil/Gas Reservoir Geology and Exploitation at CDUT (PL200801)
文摘The Upper Permian Changxing dolomite reservoirs serves as one of the most important gas and oil reservoirs in the NE Sichuan Basin. Determining the dolomitizing fluid's pathway is regarded as the key to solve the "dolomite problem" and further petroleum exploration. Outcrop samples from Upper Permian Changhsingian Panlongdong Section were studied using oxygen isotopic analysis, cathodoluminescence(CL) and major element analysis, in an attempt to determine the migration path way and properties of the dolomitizing fluid. Of the Changxing dolomite, the δ18O values ranged from-3.494‰ to-5.481‰, which decreased from the top layer to the bottom in the section; the MgO contents varied from 9.24% to 21.43%, CaO contents from 28.65% to 39.87%, the CaO/MgO ratio from 1.40 to 4.31 and the Mn O contents from 0.004% to 0.009 8%. The Mg O contents showed a downwardly decreasing trend in the section, while the Ca O/Mg O showed an opposite rule. All of the dolomites looked dull or dark when they were exposed to the electron beam of the cathodoluminescence device. None of the fine-to medium grained dolomite showed a banded structure. Given that dolomitizing fluid's salinity decreased during the dolomitization process in its pathway, we concluded that the dolomitizing fluid migrated downwardly in Changxing Formation after excluding the possibility of deep burial or meteoric-marine mixing-water influences. As the dolomitizing fluid's pathway has always been difficult to be determined in highly dolomitized Formation, this study showed an important application of oxygen isotope values in resolving this problem.