<p>Coastal Fars is the main gas-bearing region in Iran, where the reservoir units a... more <p>Coastal Fars is the main gas-bearing region in Iran, where the reservoir units are dedicated to the Paleozoic hydrocarbon system. Geochemical explorations in this region indicate that natural gas is commonly associated with elevated non-hydrocarbon components, especially hydrogen sulfide and carbon dioxide. Previously it was shown that the Thermochemical Sulfate Reduction (TSR) is the most probable mechanism, accounting for H<sub>2</sub>S occurrence in Permo-Triassic reservoirs in this region; however, its effect on the accumulated gas’s chemistry transformation has not been studied thoroughly. In this study, the molecular and isotopic composition of 12 gas samples in addition to the previously-published results of integrated analyses on rock and condensate, were utilized to trace potential alterations caused by the given phenomenon exhaustively. A slight increase in aromatic to saturate hydrocarbon components ratio with the extent of TSR and the presence of reported sulfur-rich pyrobitumen (Saberi, et al., 2014) indicate liquid hydrocarbon involvement in the primary stage of the sulfate reduction process. Further, the differential increase of δ<sup>13</sup>C of gas components, decrease of δ<sup>13</sup>C (methane) - δ<sup>13</sup>C (ethane) (from -4.3 to -13.1‰), and increase in carbon-dioxide concentration with the increase of hydrogen sulfide along with gas dryness (from 91 to 96%) show the dominancy of C<sub>2</sub>-C<sub>4</sub> hydrocarbon gas components in the second stage of TSR. Comparative low reservoir temperature (~90°C) does not correspond to the contribution of methane into the given phenomenon; however, a noticeable increase in δ<sup>13</sup>C (methane) (from -41.7 to -34.7‰) with the increase of hydrogen sulfide was seen. Thermochemical Sulfate Reduction impact on studied parameters is analogous to thermal maturation, but the process from heavy-hydrocarbon-dominated TSR to methane-dominated TSR presents different trends of δ<sup>13</sup>C (methane) - δ<sup>13</sup>C (ethane), ln(C<sub>1</sub>/C<sub>2</sub>) from those of maturation (Hao, et al., 2008). Simultaneous carbon-dioxide content increase and decrease in its isotopic composition with the extent of TSR indicate its presence relevancy to the given phenomenon; however, carbon isotope values of CO<sub>2</sub> (from -5.92 to -13.93‰) are too heavy to verify this idea. According to Dai et.al (Dai, et al., 1996) it can be concluded that carbonate's dissolution has contributed to carbon-dioxide gas. Hence, a series of TSR corresponding to condensate, wet gas, and dry gas stages, respectively, has led to higher aromatic/saturate ratios, heavier hydrocarbon components, lighter carbon dioxide molecules, and relative gas dryness in the studied fields.</p><p><strong> Bibliography</strong></p><ul><li>Dai, J. X., Song, Y., Dai, C. S. & Wang, D. R., 1996. Geochemistry and Accumulation of Carbon Dioxide Gases in China. <em>AAPG Bulletin, </em>80(10), pp. 1615-1626.</li> <li>Hao, F. et al., 2008. Evidence for multiple stages of oil cracking and thermochemical sulfate reduction in the Puguang gas field, Sichuan Basin, China. <em>AAPG Bulletin, </em>92(5), pp. 611-637.</li> <li>Saberi, M. H., Rabbani, A. & Ahmadabadi, K. A., 2014. The Age and Facies Characteristics of Persian Gulf Source Rocks. <em>Petroleum Science and Technology, </em>Volume 32, pp. 371-378.</li> </ul><p> </p>
ABSTRACT The purpose of this research was to study the effect of CO2 injection on the geochemistr... more ABSTRACT The purpose of this research was to study the effect of CO2 injection on the geochemistry of crude oil in order to determine the probability of using geochemical parameters for monitoring CO2 injection. In this process, four oil samples from different offshore oil fields were collected, synthetic steady state oil reservoir (porous media) were made by slim tube apparatus, then CO2 injection process was done in different pressures. Various geochemical analyses were also carried out on the injected oil before and after the injection. The results show that the bulky changes on oil sample by CO2 injection. CO2 injection is more likely to precipitate complex and large molecules such as asphaltenes-resins and also large normal alkanes. In this case, the percentage of aromatic molecules was increased during injection. In general view on chromatograms, the height and abundance of all saturated compound peaks after CO2 injection were significantly decreased. However, biomarker analysis shows that CO2 injection has a tendency to change source and maturity biomarker parameters.
ABSTRACT Few studies were done to investigate performance of the Fast steam-assisted gravity dama... more ABSTRACT Few studies were done to investigate performance of the Fast steam-assisted gravity damage (SAGD) recovery method especially in naturally fractured reservoirs (NFR). The authors studied some cyclic steam stimulated operational parameters effects on the Fast-SAGD performance in NFR. A synthetic 2D homogenous model was constructed by Computer Modelling Group's (CMG) and simulated using the STARS module. Comparison between SAGD and Fast-SAGD recovery methods in this model shows great increase in the oil production but small increase of thermal efficiency in the Fast-SAGD recovery method. Simulation outcomes represent 17% increment in ultimate recovery factor but small reduction in steam-oil ratio. Results show that increasing the number of offset cycles and injection period yield increment in the oil production. Increasing the offset injection rate causes growth in the oil production, but has an optimal value. By increasing the distance between the offset well and SAGD well pairs up to a certain value, oil production increases but decreases after that point. This is due to the ability of the fractures in making connection between the steam chambers in higher distances. When production bottom-hole pressure decreases, the heated oil in near well region is subjected to more pressure drop and causes more oil to be produced. More offset wells result in higher production but simultaneously lower recovery factors. Increasing and decreasing soak time as the last investigated parameter did not affect the trend of production anyway.
It is essential that precipitation of asphaltenes is recognized early in the planning stage of an... more It is essential that precipitation of asphaltenes is recognized early in the planning stage of any CO2 enhanced oil recovery (EOR) project so that appropriate testing can be performed to evaluate whether there will be a negative impact on reservoir performance. This article presents detailed evaluations of slim tube data that were obtained during CO2 injection using a medium-gravity Iranian
Three-dimensional numerical earth models play an increasingly central role in the engineering and... more Three-dimensional numerical earth models play an increasingly central role in the engineering and petroleum industry. They are routinely used to plan new wells calculate hydrocarbon reserves and when coupled to flow simulator, predict production profile. In the reservoir modeling subject there are different methods for 3D-static modeling of these methods in the present study the geostatistical method is used for 3D-static model of lower shuaiba in the West of Persian gulf. This paper focus on constructing static model for Lower Shuaiba formation is discussed and the 3D static model and property maps showing the oil reserves are presented. Oil in place estimate based on volumetric calculation is finally provided. The static model of Lower Shuaiba formation in the west of Persian Gulf revealed that the major oil deposits lie in the F3 area with some minor deposits in F1, F5 and F8 areas. The oil in place from F3 area amounts to 359.1 MMSTB and from F1, F5 and F8 area are estimated to be around 28.6, 29.9 and 27.9 MMSTB, respectively. Considering the cumulative oil production from Lower Shuaiba being 13.6 MMSTB, 431.9 MMSTB of oil is remaining to be exploited. With a recovery factor of 10% with natural depletion (being on optimistic side) the Lower Shuaiba oil reserve is estimated to be around 31 MMSTB.
Dalan (Upper Permian) and Kangan (Lower Triassic) Formation were deposited in an extensive carbon... more Dalan (Upper Permian) and Kangan (Lower Triassic) Formation were deposited in an extensive carbonate platform under an arid climate. These formations makes up the essential part of the Gas reservoirs in south of Iran and Persian Gulf. Detailed field and ...
SOURCE ROCK EVALUATION AND GEOCHEMICAL STUDIES OF CRUD OIL IN THE EASTERN PART OF PERSIAN GULF RA... more SOURCE ROCK EVALUATION AND GEOCHEMICAL STUDIES OF CRUD OIL IN THE EASTERN PART OF PERSIAN GULF RABBANI AR,BABAII MN ... Oil fields Investigated Include Resalat, Salman, Sirri and Nousrat In the eastern. part of Persian. Gulf. ...
ABSTRACT Due to the lack of information about the porosity exponent (m) from core experiments, th... more ABSTRACT Due to the lack of information about the porosity exponent (m) from core experiments, the impossibility of comparison between the results and the core data, and, finally, inattentiveness to fractured intervals, the correct determination of the porosity exponent value in the calculation of water saturation and also the core-log correlation have generally been neglected. In this article, an analysis of the Mishrif Unit was carried out in two wells in order to properly calculate the water saturation and determine the best producing intervals. Based on fractured zones detection and the results of petrophysical evaluation in the calculation of shale volume and true matrix properties for these zones, accurate values of the porosity (matched with core data) were used to determine the porosity exponent. Hence, one of the advantages of this study is applying the method introduced simply for the fractured parts of the reservoir unit, in order to obtain the correct value for water saturation. Detecting proper producing intervals in the Mishrif Unit was executed using integrated evaluation of petrophysical data, geological data, and core data using a new method of shaly carbonate formation interpretation based on petrophysical log results. In this method, a statistical parameter, P½, was used. The results from the application of the method show better interpretation and water saturation calculation using petrophysical logs of fractured shaly carbonate formations in combination with other available methods in the petroleum community.
<p>Coastal Fars is the main gas-bearing region in Iran, where the reservoir units a... more <p>Coastal Fars is the main gas-bearing region in Iran, where the reservoir units are dedicated to the Paleozoic hydrocarbon system. Geochemical explorations in this region indicate that natural gas is commonly associated with elevated non-hydrocarbon components, especially hydrogen sulfide and carbon dioxide. Previously it was shown that the Thermochemical Sulfate Reduction (TSR) is the most probable mechanism, accounting for H<sub>2</sub>S occurrence in Permo-Triassic reservoirs in this region; however, its effect on the accumulated gas’s chemistry transformation has not been studied thoroughly. In this study, the molecular and isotopic composition of 12 gas samples in addition to the previously-published results of integrated analyses on rock and condensate, were utilized to trace potential alterations caused by the given phenomenon exhaustively. A slight increase in aromatic to saturate hydrocarbon components ratio with the extent of TSR and the presence of reported sulfur-rich pyrobitumen (Saberi, et al., 2014) indicate liquid hydrocarbon involvement in the primary stage of the sulfate reduction process. Further, the differential increase of δ<sup>13</sup>C of gas components, decrease of δ<sup>13</sup>C (methane) - δ<sup>13</sup>C (ethane) (from -4.3 to -13.1‰), and increase in carbon-dioxide concentration with the increase of hydrogen sulfide along with gas dryness (from 91 to 96%) show the dominancy of C<sub>2</sub>-C<sub>4</sub> hydrocarbon gas components in the second stage of TSR. Comparative low reservoir temperature (~90°C) does not correspond to the contribution of methane into the given phenomenon; however, a noticeable increase in δ<sup>13</sup>C (methane) (from -41.7 to -34.7‰) with the increase of hydrogen sulfide was seen. Thermochemical Sulfate Reduction impact on studied parameters is analogous to thermal maturation, but the process from heavy-hydrocarbon-dominated TSR to methane-dominated TSR presents different trends of δ<sup>13</sup>C (methane) - δ<sup>13</sup>C (ethane), ln(C<sub>1</sub>/C<sub>2</sub>) from those of maturation (Hao, et al., 2008). Simultaneous carbon-dioxide content increase and decrease in its isotopic composition with the extent of TSR indicate its presence relevancy to the given phenomenon; however, carbon isotope values of CO<sub>2</sub> (from -5.92 to -13.93‰) are too heavy to verify this idea. According to Dai et.al (Dai, et al., 1996) it can be concluded that carbonate's dissolution has contributed to carbon-dioxide gas. Hence, a series of TSR corresponding to condensate, wet gas, and dry gas stages, respectively, has led to higher aromatic/saturate ratios, heavier hydrocarbon components, lighter carbon dioxide molecules, and relative gas dryness in the studied fields.</p><p><strong> Bibliography</strong></p><ul><li>Dai, J. X., Song, Y., Dai, C. S. & Wang, D. R., 1996. Geochemistry and Accumulation of Carbon Dioxide Gases in China. <em>AAPG Bulletin, </em>80(10), pp. 1615-1626.</li> <li>Hao, F. et al., 2008. Evidence for multiple stages of oil cracking and thermochemical sulfate reduction in the Puguang gas field, Sichuan Basin, China. <em>AAPG Bulletin, </em>92(5), pp. 611-637.</li> <li>Saberi, M. H., Rabbani, A. & Ahmadabadi, K. A., 2014. The Age and Facies Characteristics of Persian Gulf Source Rocks. <em>Petroleum Science and Technology, </em>Volume 32, pp. 371-378.</li> </ul><p> </p>
ABSTRACT The purpose of this research was to study the effect of CO2 injection on the geochemistr... more ABSTRACT The purpose of this research was to study the effect of CO2 injection on the geochemistry of crude oil in order to determine the probability of using geochemical parameters for monitoring CO2 injection. In this process, four oil samples from different offshore oil fields were collected, synthetic steady state oil reservoir (porous media) were made by slim tube apparatus, then CO2 injection process was done in different pressures. Various geochemical analyses were also carried out on the injected oil before and after the injection. The results show that the bulky changes on oil sample by CO2 injection. CO2 injection is more likely to precipitate complex and large molecules such as asphaltenes-resins and also large normal alkanes. In this case, the percentage of aromatic molecules was increased during injection. In general view on chromatograms, the height and abundance of all saturated compound peaks after CO2 injection were significantly decreased. However, biomarker analysis shows that CO2 injection has a tendency to change source and maturity biomarker parameters.
ABSTRACT Few studies were done to investigate performance of the Fast steam-assisted gravity dama... more ABSTRACT Few studies were done to investigate performance of the Fast steam-assisted gravity damage (SAGD) recovery method especially in naturally fractured reservoirs (NFR). The authors studied some cyclic steam stimulated operational parameters effects on the Fast-SAGD performance in NFR. A synthetic 2D homogenous model was constructed by Computer Modelling Group's (CMG) and simulated using the STARS module. Comparison between SAGD and Fast-SAGD recovery methods in this model shows great increase in the oil production but small increase of thermal efficiency in the Fast-SAGD recovery method. Simulation outcomes represent 17% increment in ultimate recovery factor but small reduction in steam-oil ratio. Results show that increasing the number of offset cycles and injection period yield increment in the oil production. Increasing the offset injection rate causes growth in the oil production, but has an optimal value. By increasing the distance between the offset well and SAGD well pairs up to a certain value, oil production increases but decreases after that point. This is due to the ability of the fractures in making connection between the steam chambers in higher distances. When production bottom-hole pressure decreases, the heated oil in near well region is subjected to more pressure drop and causes more oil to be produced. More offset wells result in higher production but simultaneously lower recovery factors. Increasing and decreasing soak time as the last investigated parameter did not affect the trend of production anyway.
It is essential that precipitation of asphaltenes is recognized early in the planning stage of an... more It is essential that precipitation of asphaltenes is recognized early in the planning stage of any CO2 enhanced oil recovery (EOR) project so that appropriate testing can be performed to evaluate whether there will be a negative impact on reservoir performance. This article presents detailed evaluations of slim tube data that were obtained during CO2 injection using a medium-gravity Iranian
Three-dimensional numerical earth models play an increasingly central role in the engineering and... more Three-dimensional numerical earth models play an increasingly central role in the engineering and petroleum industry. They are routinely used to plan new wells calculate hydrocarbon reserves and when coupled to flow simulator, predict production profile. In the reservoir modeling subject there are different methods for 3D-static modeling of these methods in the present study the geostatistical method is used for 3D-static model of lower shuaiba in the West of Persian gulf. This paper focus on constructing static model for Lower Shuaiba formation is discussed and the 3D static model and property maps showing the oil reserves are presented. Oil in place estimate based on volumetric calculation is finally provided. The static model of Lower Shuaiba formation in the west of Persian Gulf revealed that the major oil deposits lie in the F3 area with some minor deposits in F1, F5 and F8 areas. The oil in place from F3 area amounts to 359.1 MMSTB and from F1, F5 and F8 area are estimated to be around 28.6, 29.9 and 27.9 MMSTB, respectively. Considering the cumulative oil production from Lower Shuaiba being 13.6 MMSTB, 431.9 MMSTB of oil is remaining to be exploited. With a recovery factor of 10% with natural depletion (being on optimistic side) the Lower Shuaiba oil reserve is estimated to be around 31 MMSTB.
Dalan (Upper Permian) and Kangan (Lower Triassic) Formation were deposited in an extensive carbon... more Dalan (Upper Permian) and Kangan (Lower Triassic) Formation were deposited in an extensive carbonate platform under an arid climate. These formations makes up the essential part of the Gas reservoirs in south of Iran and Persian Gulf. Detailed field and ...
SOURCE ROCK EVALUATION AND GEOCHEMICAL STUDIES OF CRUD OIL IN THE EASTERN PART OF PERSIAN GULF RA... more SOURCE ROCK EVALUATION AND GEOCHEMICAL STUDIES OF CRUD OIL IN THE EASTERN PART OF PERSIAN GULF RABBANI AR,BABAII MN ... Oil fields Investigated Include Resalat, Salman, Sirri and Nousrat In the eastern. part of Persian. Gulf. ...
ABSTRACT Due to the lack of information about the porosity exponent (m) from core experiments, th... more ABSTRACT Due to the lack of information about the porosity exponent (m) from core experiments, the impossibility of comparison between the results and the core data, and, finally, inattentiveness to fractured intervals, the correct determination of the porosity exponent value in the calculation of water saturation and also the core-log correlation have generally been neglected. In this article, an analysis of the Mishrif Unit was carried out in two wells in order to properly calculate the water saturation and determine the best producing intervals. Based on fractured zones detection and the results of petrophysical evaluation in the calculation of shale volume and true matrix properties for these zones, accurate values of the porosity (matched with core data) were used to determine the porosity exponent. Hence, one of the advantages of this study is applying the method introduced simply for the fractured parts of the reservoir unit, in order to obtain the correct value for water saturation. Detecting proper producing intervals in the Mishrif Unit was executed using integrated evaluation of petrophysical data, geological data, and core data using a new method of shaly carbonate formation interpretation based on petrophysical log results. In this method, a statistical parameter, P½, was used. The results from the application of the method show better interpretation and water saturation calculation using petrophysical logs of fractured shaly carbonate formations in combination with other available methods in the petroleum community.
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