The ever-increasing demand for oil and gas has driven its exploration in rather extreme conditions. In Lamu offshore, which is hitherto underexplored, most of the wells already drilled turned out dry save for a few we...The ever-increasing demand for oil and gas has driven its exploration in rather extreme conditions. In Lamu offshore, which is hitherto underexplored, most of the wells already drilled turned out dry save for a few wells with hydrocarbon shows despite the promising reservoir properties and related geological structures. This, therefore, necessitated a source rock evaluation study in the area to ascertain the presence and potential of the source rock by integrating the geochemical data analysis and petroleum system modeling. The shallow Lamu offshore source rock quantity, quality, and maturity have been estimated through the determination of the total organic carbon (TOC) average values, Kerogen typing, and Rock-Eval pyrolysis measurements respectively. Geochemical data for Kubwa-1, Mbawa-1, Pomboo-1, and Simba-1 were evaluated for determining the source rock potential for hydrocarbon generation. Petroleum system modeling was applied in evaluating geological conditions necessary for a successful charge within a software that integrated geochemical and petrophysical characterization of the sedimentary formations in conjunction with boundary conditions that include basal heat flow, sediment-water interface temperature, and Paleo-water depth. The average TOC of 0.89 wt % in the study area suggests a fair organic richness which seems higher in the late cretaceous (0.98 wt %) than in the Paleocene (0.81 wt %). Vitrinite reflectance and T<sub>max</sub> values in the study area indicate the possible presence of both mature and immature source rocks. Type III Kerogen was the most dominant Kerogen type, and gas shows are the most frequent hydrocarbon encountered in the Lamu Basin with a few cases registering type II/III and type II. The charge properties (i.e. Temperature, transformation ratio, and Vitrinite reflectance) over geologic time at each of the wells have been estimated and their spatial variation mapped as seen from the burial history and depth curves overlaid with temperature, transformation ratio, and Vitrinite reflectance respectively. From the upper cretaceous maturity maps, the results seem to favor near coastal regions where average TOC is about 1.4 wt %, Vitrinite reflectance is more than 0.5%, transformation ratio is more than 10%, and temperatures range from 80°C to 160°C. The results postulate the absence of a definitive effective source rock with a likelihood of having cases of potential and possible source rocks. Moreover, greater uncertainty rests on the source rock’s presence and viability tending toward the deep offshore. Geochemical analysis and petroleum system modeling for hydrocarbon source rock evaluation improved the understanding of the occurrence of the possible and potential source rocks and processes necessary for hydrocarbon generation.展开更多
Previous studies have postulated the contribution of present-day low-total organic carbon (TOC) marine carbonate source rocks to oil accumulations in the Tabei Uplift, Tarim Basin, China. However, not all present-da...Previous studies have postulated the contribution of present-day low-total organic carbon (TOC) marine carbonate source rocks to oil accumulations in the Tabei Uplift, Tarim Basin, China. However, not all present-day low-TOC carbonates have generated and expelled hydrocarbons; therefore, to distinguish the source rocks that have already expelled sufficient hydrocarbons from those not expelled hydrocarbons, is crucial in source rock evaluation and resource assessment in the Tabei Uplift. Mass balance can be used to identify modern low-TOC carbonates resulting from hydrocarbon expulsion. However, the process is quite complicated, requiring many parameters and coefficients and thus also a massive data source. In this paper, we provide a quick and cost effective method for identifying carbonate source rock with present-day low TOC, using widely available Rock-Eval data. First, we identify present-day low-TOC carbonate source rocks in typical wells according to the mass balance approach. Second, we build an optimal model to evaluate source rocks from the analysis of the rocks' characteristics and their influencing factors, reported as positive or negative values of a dimensionless index of Rock-Eval data (IR). Positive IR corresponds to those samples which have expelled hydrocarbons. The optimal model optimizes complicated calculations and simulation processes; thus it could be widely applicable and competitive in the evaluation of present-day low TOC carbonates. By applying the model to the Rock-Eval dataset of the Tabei Uplift, we identify present-day iow-TOC carbonate source rocks and primarily evaluate the contribution equivalent of 11.87×10^9 t oil.展开更多
How to accurately recover the hydrocarbon loss is a crucial step in reservoir evaluation by Rock-Eval pyrolysis. However, it is very difficult to determine the recovering coefficients because there are numerous factor...How to accurately recover the hydrocarbon loss is a crucial step in reservoir evaluation by Rock-Eval pyrolysis. However, it is very difficult to determine the recovering coefficients because there are numerous factors causing the hydrocarbon loss. Aiming at this problem, a new method named critical point analysis is put forward in this paper. The first step of the method is to find the critical point by drawing the scatterplot of hydrocarbon contents versus the ratio of the light component of with the heavy component of;And the second step is to calculate the recovering coefficient by contrasting the pyrolysis parameters at the critical point of different sample types. This method is not only been explained reasonably theoretically,but also has got a good application effect in Huanghua depression.展开更多
Source-rock characteristics of Lower Triassic Montney Formation presented in this study shows the total organic carbon (TOC) richness, thermal maturity, hydrocarbon generation, geographical distribution of TOC and the...Source-rock characteristics of Lower Triassic Montney Formation presented in this study shows the total organic carbon (TOC) richness, thermal maturity, hydrocarbon generation, geographical distribution of TOC and thermal maturity (Tmax) in Fort St. John study area (T86N, R23W and T74N, R13W) and its environs in northeastern British Columbia, Western Canada Sedimentary Basin (WCSB). TOC richness in Montney Formation within the study area is grouped into three categories: low TOC ( 3.5 wt%), and high TOC (>3.5 wt% %). Thermal maturity of the Montney Formation source-rock indicates that >90% of the analyzed samples are thermally mature, and mainly within gas generating window (wet gas, condensate gas, and dry gas), and comprises mixed Type II/III (oil/gas prone kerogen), and Type IV kerogen (gas prone). Analyses of Rock-Eval parameters (TOC, S2, Tmax, HI, OI and PI) obtained from 81 samples in 11 wells that penetrated the Montney Formation in the subsurface of northeastern British Columbia were used to map source rock quality across the study area. Based on total organic carbon (TOC) content mapping, geographical distribution of thermal maturity (Tmax) data mapping, including evaluation and interpretation of Rock-Eval parameters in the study area, the Montney Formation kerogen is indicative of a pervasively matured petroleum system in the study area.展开更多
This article prognosticates the hydrocarbon generation potential of core samples from fields A, B, C and D in Niger delta, Nigeria. The objectives of this study are to characterize the quality of these core samples by...This article prognosticates the hydrocarbon generation potential of core samples from fields A, B, C and D in Niger delta, Nigeria. The objectives of this study are to characterize the quality of these core samples by organic geochemical analyses. A total of ten core samples collected from fields A, B, C and D in Niger delta were analyzed using total organic carbon(TOC) content analysis, rock-eval pyrolysis technique. The analytical results of the studied core samples reveal that they have generally high total organic carbon contents(TOC), suggesting that conditions in the Niger delta favour organic matter production and preservation. There is a variation in the kerogen types and this may be attributed to the relative stratigraphic positions of the core samples within the Niger delta. The rock-eval results indicate that the samples from fields C and D contain predominantly Type II kerogen with a capacity to generate oil and gas and hence have good generative potential. The samples from fields A and B contain mainly Type III kerogen and are gas-prone with moderate generative potential.展开更多
The contamination of cuttings and side wall core (SWC) samples in the Bambra 2 well by drilling mud additives and natural hydrocarbons may cause Rock Eval T max (℃) data to be suspect, and affect its uti...The contamination of cuttings and side wall core (SWC) samples in the Bambra 2 well by drilling mud additives and natural hydrocarbons may cause Rock Eval T max (℃) data to be suspect, and affect its utility in the assessment of thermal maturity. The Rock Eval results of 284 cuttings samples, 31 side wall core samples and conventional core samples from the Jurassic Cretaceous sedimentary sequences in the Bambra 2 well are presented in this paper. Significantly lower T max values from cuttings samples compared with T max values from conventional core samples and solvent extracted SWC samples, from the deeper and higher maturity interval, are thought to have been caused by contamination by diesel and other drilling mud additives. The cuttings samples in the Barrow Group of Cretaceous may be contaminated by natural hydrocarbons, resulting their T max values to be 2-10 ℃ lower than a regularly increased T max trend from core samples. This study indicates that more reliable Rock Eval T max data are obtained from the conventional core samples and solvent extracted SWC samples. This study also indicates that the T max values from some SWC samples were also affected by free hydrocarbons, due to the use of diesel as a mud additive as well.展开更多
A study on the potential and kinetics of hydrocarbon (HC) generation of30 source-roch samples from a certain depression has been made by means of ROCKEVAL technique. In the qyrolysis experiment, the source maerial typ...A study on the potential and kinetics of hydrocarbon (HC) generation of30 source-roch samples from a certain depression has been made by means of ROCKEVAL technique. In the qyrolysis experiment, the source maerial types, maturation andhydrocarbon-generating potential of source rocks from three Upper Jurassic horizons ofthat area have been evaluated in terms of such indicators as the type-index, hydrocarbongenerating potential and maximum pyrolysis temperature (Tmax). The results show thatthe pyrolysis HC yield of immature source rocks is much higher than that of mature rocksin case that the source material is of high quantity and organic matter is abundant, whichsuggests that it is important for evaluating the HC-generating potential to use immaturesamples for pyrolysis. In the pyrolytic simulation experiments on other two immaturesamples, it was found that the hydrocarbon yield is temperaure-dependent, and thereafterthe kinetical parameters for source rocks, such as reactional grade, appearant activationenergy and frequency facor were calculated.展开更多
The lower Cretaceous rock units of the Koppeh-Dagh Basin of northeastern Iran were investigated here in terms of biostratigraphy,depositional setting and geochemical analyses to find out if they,alike other parts of t...The lower Cretaceous rock units of the Koppeh-Dagh Basin of northeastern Iran were investigated here in terms of biostratigraphy,depositional setting and geochemical analyses to find out if they,alike other parts of the world,are rich in petroleum.For this purpose,a stratigraphic framework is established using calcareous nannofossil and palynological elements.A nannoplankton zonation based on which subzones of the zones CC7–CC8 of Sissingh(1977)and their equivalent NC6–NC8 of Roth(1978)was established indicating a Late Barremian–Albian age.Palynological assemblages led us to establish the local palynozone of Odontochitina operculata.A dominantly marginal basin to a transitional zone between shelf and basin under a dysoxic–anoxic condition with low to moderate sedimentation rates coincided with a gradual sea level rise was introduced as the environment of deposition for the strata via interpretation of the palynological parameters and quantitative palynology.The obtained data from Rock-Eval pyrolysis in compilation with palynofacies analysis reveals that the studied succession contains mainly gas-prone type III kerogen.The Spore Coloration Index(SCI)alongside with the Rock-Eval pyrolysis results(low values of HI and TOC)proves that these rock units locally produced natural gas during the time under consideration.展开更多
Pabdeh Formation is one of the most important source rocks in Zagros basin. In this study, thermal modeling and comparing of hydrocarbon potential evaluation of Pabdeh Formation in Mish Anticline and Gachsaran oil fie...Pabdeh Formation is one of the most important source rocks in Zagros basin. In this study, thermal modeling and comparing of hydrocarbon potential evaluation of Pabdeh Formation in Mish Anticline and Gachsaran oil field have been investigated. For this reason, Rock-Eval pyrolysis was carried out on 21 cuttings samples collected from 2 boreholes (Well No. 55 and 83) of Gachsaran oil field and outcrop of Mish anticline. Accordingly, the Kerogen types of Pabdeh Formation in Gachsaran oil field are II, but in Mish anticline are type II and III. The amount of inert organic carbon determined for the Pabdeh Formation in Mish anticline is about 4.879 wt%, while for Gachsaran oil field, it is estimated at 0.153 (Well. No. 55) and 1.156 (Well. No. 83) wt%. Absorption of hydrocarbon by rock matrix was also determined. The amount of absorption in Mish anticline is more than that of Gachsaran oil field. This is mostly due to the presence of argillaceous matrix in this area, but the clays have not been successful in absorbing organic matter;this is due to the result obtained from small amount of organic matter in the basin. The Rock-Eval data revealed that the sedimentary paleo-environment strongly affected the source potential of this formation as it changed from the continental and Deltaic in the Mish anticline to deeper marine in Gachsaran oil field. In addition, curves of Burial history were drawn for Gachsaran well No. 55, in order to assess the thermal maturity of the Pabdeh formation. The results of the methods indicated that Pabdeh formation in Gachsaran oil field had a good to very good hydrocarbon potential and had entered to oil window.展开更多
The authors present the effects of the total organic carbon( TOCinert) during pyrolysis and how it overall affects the estimates of the hydrocarbon index( HI) using the cross plot S2 vs. TOC graph. A total of 21 drill...The authors present the effects of the total organic carbon( TOCinert) during pyrolysis and how it overall affects the estimates of the hydrocarbon index( HI) using the cross plot S2 vs. TOC graph. A total of 21 drillcore samples consisting of the non-carbonaceous mudstones,carbonaceous mudstones,coaly mudstones and coals with S2> 0. 35 are selected and used. The average TOC for the sampled population is 10. 36 wt%.TOCinertmeasured from the S2 vs. TOC graph is 2. 97 wt% and the average pyrolysable TOCliveis 7. 39 wt%. The HI is 102 mg HC / g TOC and the pyrolysable HI is 175 mg HC / g TOC,indicating that the TOCinertor mi-neral matrix adsorbs some of the hydrocarbons liberated during pyrolysis resulting into the low HI values which affects the correct determination of the source rock potential. Other applications of the S2 vs. TOC cross plot have been used to determine the depositional system tracts. The high stand system tract is also determined through this method.展开更多
Ditch samples from AP-4, ER-51 and UK-2 offshore Niger Delta were subjected to biostratigraphic and organic geochemical analyses which entail foraminiferal, palynological, Spore Colour Index (SCI), Rock-Eval Pyrolysis...Ditch samples from AP-4, ER-51 and UK-2 offshore Niger Delta were subjected to biostratigraphic and organic geochemical analyses which entail foraminiferal, palynological, Spore Colour Index (SCI), Rock-Eval Pyrolysis and Fourier Transform Infrared Spectroscopy (FTIR) analyses. The results have established N19 and N17;N17, N16 and N15;and N9 and N8 biozones;and P600 and P700 palynological zones. The dominance of palynomaceral (PM) I and II suggests Type III kerogen. PM III and IV (Type II and IV) were recorded. SCI ranges from 3/4 to 5/6 suggesting an early to mature liquid hydrocarbon generation phase. Rock-Eval Pyrolysis shows that the Total Organic Carbon (TOC), Hydrogen Index (HI), Pyrolysis temperature (T<sub>max</sub>), and Vitrinite Reflectance (VR<sub>o</sub>) range from 2.48 wt% - 6.37 wt%, 78 - 258, 411°C - 431°C and 0.26% - 0.69% respectively suggesting high TOC of Type II/III kerogen. FTIR indices show Type I kerogen in all the wells. VRo results range from 0.4 - 0.5 indicating an immature source. High concentrations of aliphatic saturates in identified functional groups indicate a low biodegradation. The abundance and diversity of recovered assemblages and dominance of PM I and II suggest shallow depositional environments with an age range of late Miocene to early Pliocene. Palynomaceral, SCI, and Rock-Eval inference contradict FTIR kerogen type suggesting that IR spectroscopy might not be suitable for kerogen typing and origin. The geochemical and biostratigraphical inferences must be corroborated for a successful evaluation. However, the source rock in the study area has adequate organic matter with the prospect to generate both oil and gas at appropriate maturity.展开更多
文摘The ever-increasing demand for oil and gas has driven its exploration in rather extreme conditions. In Lamu offshore, which is hitherto underexplored, most of the wells already drilled turned out dry save for a few wells with hydrocarbon shows despite the promising reservoir properties and related geological structures. This, therefore, necessitated a source rock evaluation study in the area to ascertain the presence and potential of the source rock by integrating the geochemical data analysis and petroleum system modeling. The shallow Lamu offshore source rock quantity, quality, and maturity have been estimated through the determination of the total organic carbon (TOC) average values, Kerogen typing, and Rock-Eval pyrolysis measurements respectively. Geochemical data for Kubwa-1, Mbawa-1, Pomboo-1, and Simba-1 were evaluated for determining the source rock potential for hydrocarbon generation. Petroleum system modeling was applied in evaluating geological conditions necessary for a successful charge within a software that integrated geochemical and petrophysical characterization of the sedimentary formations in conjunction with boundary conditions that include basal heat flow, sediment-water interface temperature, and Paleo-water depth. The average TOC of 0.89 wt % in the study area suggests a fair organic richness which seems higher in the late cretaceous (0.98 wt %) than in the Paleocene (0.81 wt %). Vitrinite reflectance and T<sub>max</sub> values in the study area indicate the possible presence of both mature and immature source rocks. Type III Kerogen was the most dominant Kerogen type, and gas shows are the most frequent hydrocarbon encountered in the Lamu Basin with a few cases registering type II/III and type II. The charge properties (i.e. Temperature, transformation ratio, and Vitrinite reflectance) over geologic time at each of the wells have been estimated and their spatial variation mapped as seen from the burial history and depth curves overlaid with temperature, transformation ratio, and Vitrinite reflectance respectively. From the upper cretaceous maturity maps, the results seem to favor near coastal regions where average TOC is about 1.4 wt %, Vitrinite reflectance is more than 0.5%, transformation ratio is more than 10%, and temperatures range from 80°C to 160°C. The results postulate the absence of a definitive effective source rock with a likelihood of having cases of potential and possible source rocks. Moreover, greater uncertainty rests on the source rock’s presence and viability tending toward the deep offshore. Geochemical analysis and petroleum system modeling for hydrocarbon source rock evaluation improved the understanding of the occurrence of the possible and potential source rocks and processes necessary for hydrocarbon generation.
基金supported by the China Postdoctoral Science Foundation (grant No. 2017M611108)the National Science and Technology Major Project of China (grant No. 2016ZX05006006-001)the National Basic Research Program of China (grant Nos. 2011CB2011-02 and 2014CB239100)
文摘Previous studies have postulated the contribution of present-day low-total organic carbon (TOC) marine carbonate source rocks to oil accumulations in the Tabei Uplift, Tarim Basin, China. However, not all present-day low-TOC carbonates have generated and expelled hydrocarbons; therefore, to distinguish the source rocks that have already expelled sufficient hydrocarbons from those not expelled hydrocarbons, is crucial in source rock evaluation and resource assessment in the Tabei Uplift. Mass balance can be used to identify modern low-TOC carbonates resulting from hydrocarbon expulsion. However, the process is quite complicated, requiring many parameters and coefficients and thus also a massive data source. In this paper, we provide a quick and cost effective method for identifying carbonate source rock with present-day low TOC, using widely available Rock-Eval data. First, we identify present-day low-TOC carbonate source rocks in typical wells according to the mass balance approach. Second, we build an optimal model to evaluate source rocks from the analysis of the rocks' characteristics and their influencing factors, reported as positive or negative values of a dimensionless index of Rock-Eval data (IR). Positive IR corresponds to those samples which have expelled hydrocarbons. The optimal model optimizes complicated calculations and simulation processes; thus it could be widely applicable and competitive in the evaluation of present-day low TOC carbonates. By applying the model to the Rock-Eval dataset of the Tabei Uplift, we identify present-day iow-TOC carbonate source rocks and primarily evaluate the contribution equivalent of 11.87×10^9 t oil.
文摘How to accurately recover the hydrocarbon loss is a crucial step in reservoir evaluation by Rock-Eval pyrolysis. However, it is very difficult to determine the recovering coefficients because there are numerous factors causing the hydrocarbon loss. Aiming at this problem, a new method named critical point analysis is put forward in this paper. The first step of the method is to find the critical point by drawing the scatterplot of hydrocarbon contents versus the ratio of the light component of with the heavy component of;And the second step is to calculate the recovering coefficient by contrasting the pyrolysis parameters at the critical point of different sample types. This method is not only been explained reasonably theoretically,but also has got a good application effect in Huanghua depression.
文摘Source-rock characteristics of Lower Triassic Montney Formation presented in this study shows the total organic carbon (TOC) richness, thermal maturity, hydrocarbon generation, geographical distribution of TOC and thermal maturity (Tmax) in Fort St. John study area (T86N, R23W and T74N, R13W) and its environs in northeastern British Columbia, Western Canada Sedimentary Basin (WCSB). TOC richness in Montney Formation within the study area is grouped into three categories: low TOC ( 3.5 wt%), and high TOC (>3.5 wt% %). Thermal maturity of the Montney Formation source-rock indicates that >90% of the analyzed samples are thermally mature, and mainly within gas generating window (wet gas, condensate gas, and dry gas), and comprises mixed Type II/III (oil/gas prone kerogen), and Type IV kerogen (gas prone). Analyses of Rock-Eval parameters (TOC, S2, Tmax, HI, OI and PI) obtained from 81 samples in 11 wells that penetrated the Montney Formation in the subsurface of northeastern British Columbia were used to map source rock quality across the study area. Based on total organic carbon (TOC) content mapping, geographical distribution of thermal maturity (Tmax) data mapping, including evaluation and interpretation of Rock-Eval parameters in the study area, the Montney Formation kerogen is indicative of a pervasively matured petroleum system in the study area.
文摘This article prognosticates the hydrocarbon generation potential of core samples from fields A, B, C and D in Niger delta, Nigeria. The objectives of this study are to characterize the quality of these core samples by organic geochemical analyses. A total of ten core samples collected from fields A, B, C and D in Niger delta were analyzed using total organic carbon(TOC) content analysis, rock-eval pyrolysis technique. The analytical results of the studied core samples reveal that they have generally high total organic carbon contents(TOC), suggesting that conditions in the Niger delta favour organic matter production and preservation. There is a variation in the kerogen types and this may be attributed to the relative stratigraphic positions of the core samples within the Niger delta. The rock-eval results indicate that the samples from fields C and D contain predominantly Type II kerogen with a capacity to generate oil and gas and hence have good generative potential. The samples from fields A and B contain mainly Type III kerogen and are gas-prone with moderate generative potential.
文摘The contamination of cuttings and side wall core (SWC) samples in the Bambra 2 well by drilling mud additives and natural hydrocarbons may cause Rock Eval T max (℃) data to be suspect, and affect its utility in the assessment of thermal maturity. The Rock Eval results of 284 cuttings samples, 31 side wall core samples and conventional core samples from the Jurassic Cretaceous sedimentary sequences in the Bambra 2 well are presented in this paper. Significantly lower T max values from cuttings samples compared with T max values from conventional core samples and solvent extracted SWC samples, from the deeper and higher maturity interval, are thought to have been caused by contamination by diesel and other drilling mud additives. The cuttings samples in the Barrow Group of Cretaceous may be contaminated by natural hydrocarbons, resulting their T max values to be 2-10 ℃ lower than a regularly increased T max trend from core samples. This study indicates that more reliable Rock Eval T max data are obtained from the conventional core samples and solvent extracted SWC samples. This study also indicates that the T max values from some SWC samples were also affected by free hydrocarbons, due to the use of diesel as a mud additive as well.
文摘A study on the potential and kinetics of hydrocarbon (HC) generation of30 source-roch samples from a certain depression has been made by means of ROCKEVAL technique. In the qyrolysis experiment, the source maerial types, maturation andhydrocarbon-generating potential of source rocks from three Upper Jurassic horizons ofthat area have been evaluated in terms of such indicators as the type-index, hydrocarbongenerating potential and maximum pyrolysis temperature (Tmax). The results show thatthe pyrolysis HC yield of immature source rocks is much higher than that of mature rocksin case that the source material is of high quantity and organic matter is abundant, whichsuggests that it is important for evaluating the HC-generating potential to use immaturesamples for pyrolysis. In the pyrolytic simulation experiments on other two immaturesamples, it was found that the hydrocarbon yield is temperaure-dependent, and thereafterthe kinetical parameters for source rocks, such as reactional grade, appearant activationenergy and frequency facor were calculated.
基金the National Iranian Oil Company (NIOC) and the University of Tehran for their support
文摘The lower Cretaceous rock units of the Koppeh-Dagh Basin of northeastern Iran were investigated here in terms of biostratigraphy,depositional setting and geochemical analyses to find out if they,alike other parts of the world,are rich in petroleum.For this purpose,a stratigraphic framework is established using calcareous nannofossil and palynological elements.A nannoplankton zonation based on which subzones of the zones CC7–CC8 of Sissingh(1977)and their equivalent NC6–NC8 of Roth(1978)was established indicating a Late Barremian–Albian age.Palynological assemblages led us to establish the local palynozone of Odontochitina operculata.A dominantly marginal basin to a transitional zone between shelf and basin under a dysoxic–anoxic condition with low to moderate sedimentation rates coincided with a gradual sea level rise was introduced as the environment of deposition for the strata via interpretation of the palynological parameters and quantitative palynology.The obtained data from Rock-Eval pyrolysis in compilation with palynofacies analysis reveals that the studied succession contains mainly gas-prone type III kerogen.The Spore Coloration Index(SCI)alongside with the Rock-Eval pyrolysis results(low values of HI and TOC)proves that these rock units locally produced natural gas during the time under consideration.
文摘Pabdeh Formation is one of the most important source rocks in Zagros basin. In this study, thermal modeling and comparing of hydrocarbon potential evaluation of Pabdeh Formation in Mish Anticline and Gachsaran oil field have been investigated. For this reason, Rock-Eval pyrolysis was carried out on 21 cuttings samples collected from 2 boreholes (Well No. 55 and 83) of Gachsaran oil field and outcrop of Mish anticline. Accordingly, the Kerogen types of Pabdeh Formation in Gachsaran oil field are II, but in Mish anticline are type II and III. The amount of inert organic carbon determined for the Pabdeh Formation in Mish anticline is about 4.879 wt%, while for Gachsaran oil field, it is estimated at 0.153 (Well. No. 55) and 1.156 (Well. No. 83) wt%. Absorption of hydrocarbon by rock matrix was also determined. The amount of absorption in Mish anticline is more than that of Gachsaran oil field. This is mostly due to the presence of argillaceous matrix in this area, but the clays have not been successful in absorbing organic matter;this is due to the result obtained from small amount of organic matter in the basin. The Rock-Eval data revealed that the sedimentary paleo-environment strongly affected the source potential of this formation as it changed from the continental and Deltaic in the Mish anticline to deeper marine in Gachsaran oil field. In addition, curves of Burial history were drawn for Gachsaran well No. 55, in order to assess the thermal maturity of the Pabdeh formation. The results of the methods indicated that Pabdeh formation in Gachsaran oil field had a good to very good hydrocarbon potential and had entered to oil window.
文摘The authors present the effects of the total organic carbon( TOCinert) during pyrolysis and how it overall affects the estimates of the hydrocarbon index( HI) using the cross plot S2 vs. TOC graph. A total of 21 drillcore samples consisting of the non-carbonaceous mudstones,carbonaceous mudstones,coaly mudstones and coals with S2> 0. 35 are selected and used. The average TOC for the sampled population is 10. 36 wt%.TOCinertmeasured from the S2 vs. TOC graph is 2. 97 wt% and the average pyrolysable TOCliveis 7. 39 wt%. The HI is 102 mg HC / g TOC and the pyrolysable HI is 175 mg HC / g TOC,indicating that the TOCinertor mi-neral matrix adsorbs some of the hydrocarbons liberated during pyrolysis resulting into the low HI values which affects the correct determination of the source rock potential. Other applications of the S2 vs. TOC cross plot have been used to determine the depositional system tracts. The high stand system tract is also determined through this method.
文摘Ditch samples from AP-4, ER-51 and UK-2 offshore Niger Delta were subjected to biostratigraphic and organic geochemical analyses which entail foraminiferal, palynological, Spore Colour Index (SCI), Rock-Eval Pyrolysis and Fourier Transform Infrared Spectroscopy (FTIR) analyses. The results have established N19 and N17;N17, N16 and N15;and N9 and N8 biozones;and P600 and P700 palynological zones. The dominance of palynomaceral (PM) I and II suggests Type III kerogen. PM III and IV (Type II and IV) were recorded. SCI ranges from 3/4 to 5/6 suggesting an early to mature liquid hydrocarbon generation phase. Rock-Eval Pyrolysis shows that the Total Organic Carbon (TOC), Hydrogen Index (HI), Pyrolysis temperature (T<sub>max</sub>), and Vitrinite Reflectance (VR<sub>o</sub>) range from 2.48 wt% - 6.37 wt%, 78 - 258, 411°C - 431°C and 0.26% - 0.69% respectively suggesting high TOC of Type II/III kerogen. FTIR indices show Type I kerogen in all the wells. VRo results range from 0.4 - 0.5 indicating an immature source. High concentrations of aliphatic saturates in identified functional groups indicate a low biodegradation. The abundance and diversity of recovered assemblages and dominance of PM I and II suggest shallow depositional environments with an age range of late Miocene to early Pliocene. Palynomaceral, SCI, and Rock-Eval inference contradict FTIR kerogen type suggesting that IR spectroscopy might not be suitable for kerogen typing and origin. The geochemical and biostratigraphical inferences must be corroborated for a successful evaluation. However, the source rock in the study area has adequate organic matter with the prospect to generate both oil and gas at appropriate maturity.