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Experimental simulation on oil–water–rock interaction in deep zones
Journal of Geochemical Exploration 89 (2006) 133 – 137 www.elsevier.com/locate/jgeoexp
Experimental simulation on oil–water–rock interaction in deep zones Xiu-mei Gong a,b,⁎, Jian-hui Zeng a,b , Zhi-jun Jin c , Li-xin Chen d a Basin & Reservoir Research Center, University of Petroleum, Beijing, 102249, China Key Laboratory of Hydrocarbon Accumulation Mechanism of Education Ministry, Beijing, 102249, China c Institute of oil Exploration & Development of SINOPEC, Beijing, 100083, China Institute of Petroleum Exploration & Development, Tarim Oil Field Branch Company (CNPC), Korla, Xinjiang, 841000, China b
d
Received 9 August 2005; accepted 11 November 2005 Available online 13 March 2006
Abstract One-dimensional experimental simulation is carried out to study the mechanism of oil migration and accumulation in deep zones, the changes in the fluid components caused by oil–water–rock interaction during the process of fluid migration and the effect of the changes on reservoirs under certain temperature and pressure. The result shows that under certain temperature and pressure, many changes, which include their chemical components and the inner structure of rocks etc., occurred during oil migration from the bottom upwards along the experimental apparatus with the increased charging amount of crude oil. Especially, the biomarkers and mass composition of all samples derived from experiment unveil the existence of geochromatographic effect during the oil migration. And the dissolution has acted on mineral composition of oily-sands during the oil–water–rock interaction, which strengthens gradually during hydrocarbon migration from the bottom up along the apparatus. © 2006 Elsevier B.V. All rights reserved. Keywords: Interaction; One-dimension experimental apparatus; Simulation experiment; Geochromatographic effect
1. Introduction Physical simulation experiments have been a very effective approach in studying the interaction between fluid-rock and hydrocarbon migration. Many scholars have also studied the interaction between water and rocks via physical experimental simulations (Wendebourg, 2000). Adding hydrocarbons to the system, Cai et al. (1996) was the first in China to try to explain the mechanisms in the interaction of oil–water–rock. It is clear that the addition of hydrocarbons made the inter-
⁎ Corresponding author. Basin & Reservoir Research Center, University of Petroleum, Beijing, 102249, China. Tel.: +86 136 9356 9813; fax: +86 10 8973 3423. E-mail address: [email protected] (X. Gong). 0375-6742/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.gexplo.2005.11.049
action more complicated (Zhang et al., 2000), especially because it controlled the diagenesis and evolution of reservoirs. However, up to now, very few researchers ever studied the interaction of oil–water–rock by using physical experimental simulation. The variation of conditions for forming hydrocarbon pools associated with increasing of burial depth increases the complications for geological researchers to understand the origin, migration and accumulation of hydrocarbons. Given the present extent of exploration and geological conditions in the eastern China, reservoirs with burial depth of over 3500 m are generally called “deep zones” (Qiao et al., 2002). In this study, the Bonan sub-sag, which is located in the eastern part of the Jiyang depression in eastern China (Fig. 1), has been sampled for research on interaction of oil–water–rock. With an exploration area of 350 km2 in deep zones, the potential oil resources of the
134
X. Gong et al. / Journal of Geochemical Exploration 89 (2006) 133–137
Fig. 1. (a) Location of the Bonan sub-sag in eastern China. (b) Simplified sketch tectonic map of the deep zone in the Bonan sub-sag, eastern China.
Bonan sub-sag are estimated to be 1.5 × 108 tons, which shows better potential oil resources in the deep zone of Bonan sub-sag. However, the oil–water–rock interaction affected by temperatures and pressures and hydrocarbon sources in deep formations, becomes more and more complicated. And as far as the hydrocarbon sources are concerned, the deep hydrocarbon reservoirs in the Bonan sub-sag have the feature of mixed hydrocarbon sources, i.e. Es3 and Es4 hydrocarbon sources (Yin, 2003). Based on the characteristics of the temperatures and pressures and formation water, it was shown that deep hydrocarbon reservoirs mostly distribute within the overpressure fluid dynamical system where the biggest pressure coefficient reaches 1.6. Continuous subsidence processes during the geological history develop a scale of secondary pores in deep reservoirs and form deep reservoirs with mediumporosity and low-permeability. Thus, it is necessary to study oil migration and accumulation within deep zones under certain temperature and pressure conditions during the process of fluid migration, together with the effect of the interaction between oil, water and rock on property of the crude oil as well as the physical properties of the reservoirs.
peratures and pressures, is composed of a fluid input/ output system, experimental noumenon, T/P controlling system, and data gathering and analyzing system
2. Experimental methods Based on the geological setting of the Bonan sub-sag, the experimental simulation was conducted. And the 1-D experimental apparatus, which can operate at high tem-
Fig. 2. Schematic diagram of 1-D experimental apparatus of highpressure and high-temperature.
X. Gong et al. / Journal of Geochemical Exploration 89 (2006) 133–137
(Fig. 2). In this apparatus, the interaction between oil, water and rock under high temperature and pressure (100 °C, 30 MPa and 120 °C, 45 MPa) is simulated. Oil samples were collected from the Es3 and Es4 formations in Well Yi170, respectively. The formation water samples, which have a salinity of 3–4 g/l, were collected from the Es4 formation in the Bonan sub-sag, and the rock samples came from the natural sandstone. Considering the actually geological setting of the Bonan sub-sag, two kinds of crude oil sources exist within the present deep hydrocarbon reservoirs. Therefore, the procedure of physical simulation experiment can be divided into three steps, i.e. first, inject 150 ml oil samples of the Es4 until a stable state is reached with a fluid pressure of 30 MPa and a temperature of 100 °C, then inject 200 ml oil samples of the Es3 with fluid pressure of 45 MPa and temperature of 120 °C, and finally conduct sampling and analysis.
135
Pr / nC17 and Ph / nC18 are both reduced relatively. And the mass composition of oily sand samples changes regularly, i.e. saturated hydrocarbons increases greatly from 44.06% to 62.22% along the experimental noumenon (from oily sand sample 3 to oily sand sample 1) (Fig. 2), and the contents of asphaltene and non-hydrocarbon is reduced. And then, the ratios of Pr / nC17 and Ph / nC18 are reduced gradually from the oily sand sample 3 to oily sand sample 1, while the ratios of C(21 + 22) / − + C(28 + 29), C21 / C22 increase gradually. Some researchers believe that the geochromatographic effect is due to the sorption that occurs not only between nitrogen compounds and minerals, but also between other compounds and minerals (Milles, 1990). Therefore, these changes may be related to with the geochromatographic effect, which occurs during the process of hydrocarbon migration. 3.2. Dissolution phenomena of oily sand samples
3. Results and analysis 3.1. Changes in chemical composition of the samples after reaction Compared with the crude oil samples, the contents of asphaltene and non-hydrocarbon in the samples after reaction is reduced, while the amount of saturated hydrocarbons increases greatly to 79.16%. Also, the ratios of
The results of scanning electron microscopy on the oily sand samples shows that a certain degree of dissolution has occurred compared with the natural sand during crude oils migrate along the apparatus. And the farther the oil migrates, the stronger the dissolution is. For instance, on the quartz surface did the light dissolution occur within the lower part of the apparatus according to the scanning electron photomicrographs of
Fig. 3. SiO2 alteration-scanning electron photomicrographs of sandstone texture. 1—Surface of quartz; 2—Grains occurred dissolution; 3—Pore spaces being dissolved with the strengthen of interaction of oil–water–rock.
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X. Gong et al. / Journal of Geochemical Exploration 89 (2006) 133–137
Fig. 4. Potash feldspar ores alteration-scanning electron photomicrographs of sandstone texture.
oily sand sample 3; the photomicrograph of oily sand sample 1 within the upper part of the apparatus, however, shows bigger pore spaces dissolved with the strengthen of interaction of oil–water–rock than that of oily sand sample 2 and sample 3 (Fig. 3). As far as the composition of the sandstones is concerned, however, the dissolutions are different. Compared to quartz, the dissolution that occurred within the albite and potash feldspar is much greater and even leads to the formation of dissolved pore spaces (Fig. 4). According to some previous studies, it is the organic acid which increases the dissolution of minerals (Zhang et al., 2000). This kind of organic acid may result from the interactions between oil and pore water, or results from the heating of crude oil (Kharaka et al., 1993), and it has the positive correlation with the amount of pore water (Zhang et al., 2000). As enough formation water samples collected from the Es4 formation in the Bonan sub-sag had been injected into the apparatus before adding crude oil samples, which will play an important role for supplying the organic acid for the apparatus. It was likely the organic acid that caused the occurrence of the dissolution within the grains and came into being pores among the grains. So, this kind of dissolutions within deep formations can produce effective secondary pores, which is helpful for improving the physical property of deep reservoirs.
Some specific changes are as follows: ① many changes took place in rock structure and its chemical components of its contained hydrocarbon. Both the biomarkers and family components of the samples derived from experiment show the existence of the geochromatographic effect during the oil migration along the apparatus. ② Dissolution, to some extent, has affected the mineral components of the oily-sands during the oil– water–rock interaction. And it strengthens gradually during hydrocarbon migration from the bottom to the top of the apparatus, which can provide effective space for hydrocarbons to migrate and accumulate within the deep zones. Acknowledgements The research was funded by both the AAPG Foundation 2002 Grants-in-Aid together with the National Science Foundation of China (No. 40472075). The authors would like to thank Mr. ZHU Yixiu, ZHU Lei and Ms. LI Sumei, the researchers of the China University of Petroleum, and Ms. Li Huili, who works in the Institute of Oil Exploration and Development of SINOPEC, for their constructive suggestions on the manuscript. Also, the authors would like to thank Mr. SUN Xiwen, the senior engineer of the Geological Science Institute of Shengli Oilfield, for help in collecting the field samples.
4. Discussion and conclusions References The results of the simulation show that, under certain temperature and pressure conditions, many changes in the chemical components and the inner structure of rocks, etc., occurred during oil migration from the bottom to the top of the experimental apparatus with the increased charging amount of crude oil, as well as the interactions with sandstone and formation water.
Cai, C.F., Mei, B.W., Ma, T., et al., 1996. Hydrocarbon–water–rock interactions in the diagenetically altered system near major unconformities in Tarim Basin. Chinese Science Bulletin 41 (19), 1631–1635. Kharaka, Y.K., Lungedard, P.D., Ambats, G., et al., 1993. Generation of a liphatic acid anions and carbon dioxide by hydrous pyrolysis of crude oils. Applied Geochemistry 8, 317–324.
X. Gong et al. / Journal of Geochemical Exploration 89 (2006) 133–137 Milles, J.A., 1990. Secondary migration routes in the Brent sandstones of the Viking Granben and East Shetland basin: evidence from oil residues and subsurface pressure data. AAPG Bulletin 74, 1718–1735. Qiao, H.S., Fang, C.L., Niu, J.Y., et al., 2002. Petroleum geology of the deep horizons in East China, Beijing. Petroleum Industry Press, Beijing, pp. 254–255. Wendebourg, J., 2000. Modeling multi-component petroleum fluid migration in sedimentary basins. Journal of Geochemical Exploration 69–70, 651–656.
137
Yin, C.H., 2003. Study on geochemistry of deep oil and gas pool in Jiyang depression. Preserved in Working Station of Post D. Zhang, Z.H., Hu, W.X., Zeng, J.H., et al., 2000. Study of fluid-rock interactions in Eogene formation in Dongying depression, Bohai Gulf Basin. Acta Sedimentologica Sinica 18 (4), 560–566.
Experimental simulation on oil–water–rock interaction in deep zones Xiu-mei Gong a,b,⁎, Jian-hui Zeng a,b , Zhi-jun Jin c , Li-xin Chen d a Basin & Reservoir Research Center, University of Petroleum, Beijing, 102249, China Key Laboratory of Hydrocarbon Accumulation Mechanism of Education Ministry, Beijing, 102249, China c Institute of oil Exploration & Development of SINOPEC, Beijing, 100083, China Institute of Petroleum Exploration & Development, Tarim Oil Field Branch Company (CNPC), Korla, Xinjiang, 841000, China b
d
Received 9 August 2005; accepted 11 November 2005 Available online 13 March 2006
Abstract One-dimensional experimental simulation is carried out to study the mechanism of oil migration and accumulation in deep zones, the changes in the fluid components caused by oil–water–rock interaction during the process of fluid migration and the effect of the changes on reservoirs under certain temperature and pressure. The result shows that under certain temperature and pressure, many changes, which include their chemical components and the inner structure of rocks etc., occurred during oil migration from the bottom upwards along the experimental apparatus with the increased charging amount of crude oil. Especially, the biomarkers and mass composition of all samples derived from experiment unveil the existence of geochromatographic effect during the oil migration. And the dissolution has acted on mineral composition of oily-sands during the oil–water–rock interaction, which strengthens gradually during hydrocarbon migration from the bottom up along the apparatus. © 2006 Elsevier B.V. All rights reserved. Keywords: Interaction; One-dimension experimental apparatus; Simulation experiment; Geochromatographic effect
1. Introduction Physical simulation experiments have been a very effective approach in studying the interaction between fluid-rock and hydrocarbon migration. Many scholars have also studied the interaction between water and rocks via physical experimental simulations (Wendebourg, 2000). Adding hydrocarbons to the system, Cai et al. (1996) was the first in China to try to explain the mechanisms in the interaction of oil–water–rock. It is clear that the addition of hydrocarbons made the inter-
⁎ Corresponding author. Basin & Reservoir Research Center, University of Petroleum, Beijing, 102249, China. Tel.: +86 136 9356 9813; fax: +86 10 8973 3423. E-mail address: [email protected] (X. Gong). 0375-6742/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.gexplo.2005.11.049
action more complicated (Zhang et al., 2000), especially because it controlled the diagenesis and evolution of reservoirs. However, up to now, very few researchers ever studied the interaction of oil–water–rock by using physical experimental simulation. The variation of conditions for forming hydrocarbon pools associated with increasing of burial depth increases the complications for geological researchers to understand the origin, migration and accumulation of hydrocarbons. Given the present extent of exploration and geological conditions in the eastern China, reservoirs with burial depth of over 3500 m are generally called “deep zones” (Qiao et al., 2002). In this study, the Bonan sub-sag, which is located in the eastern part of the Jiyang depression in eastern China (Fig. 1), has been sampled for research on interaction of oil–water–rock. With an exploration area of 350 km2 in deep zones, the potential oil resources of the
134
X. Gong et al. / Journal of Geochemical Exploration 89 (2006) 133–137
Fig. 1. (a) Location of the Bonan sub-sag in eastern China. (b) Simplified sketch tectonic map of the deep zone in the Bonan sub-sag, eastern China.
Bonan sub-sag are estimated to be 1.5 × 108 tons, which shows better potential oil resources in the deep zone of Bonan sub-sag. However, the oil–water–rock interaction affected by temperatures and pressures and hydrocarbon sources in deep formations, becomes more and more complicated. And as far as the hydrocarbon sources are concerned, the deep hydrocarbon reservoirs in the Bonan sub-sag have the feature of mixed hydrocarbon sources, i.e. Es3 and Es4 hydrocarbon sources (Yin, 2003). Based on the characteristics of the temperatures and pressures and formation water, it was shown that deep hydrocarbon reservoirs mostly distribute within the overpressure fluid dynamical system where the biggest pressure coefficient reaches 1.6. Continuous subsidence processes during the geological history develop a scale of secondary pores in deep reservoirs and form deep reservoirs with mediumporosity and low-permeability. Thus, it is necessary to study oil migration and accumulation within deep zones under certain temperature and pressure conditions during the process of fluid migration, together with the effect of the interaction between oil, water and rock on property of the crude oil as well as the physical properties of the reservoirs.
peratures and pressures, is composed of a fluid input/ output system, experimental noumenon, T/P controlling system, and data gathering and analyzing system
2. Experimental methods Based on the geological setting of the Bonan sub-sag, the experimental simulation was conducted. And the 1-D experimental apparatus, which can operate at high tem-
Fig. 2. Schematic diagram of 1-D experimental apparatus of highpressure and high-temperature.
X. Gong et al. / Journal of Geochemical Exploration 89 (2006) 133–137
(Fig. 2). In this apparatus, the interaction between oil, water and rock under high temperature and pressure (100 °C, 30 MPa and 120 °C, 45 MPa) is simulated. Oil samples were collected from the Es3 and Es4 formations in Well Yi170, respectively. The formation water samples, which have a salinity of 3–4 g/l, were collected from the Es4 formation in the Bonan sub-sag, and the rock samples came from the natural sandstone. Considering the actually geological setting of the Bonan sub-sag, two kinds of crude oil sources exist within the present deep hydrocarbon reservoirs. Therefore, the procedure of physical simulation experiment can be divided into three steps, i.e. first, inject 150 ml oil samples of the Es4 until a stable state is reached with a fluid pressure of 30 MPa and a temperature of 100 °C, then inject 200 ml oil samples of the Es3 with fluid pressure of 45 MPa and temperature of 120 °C, and finally conduct sampling and analysis.
135
Pr / nC17 and Ph / nC18 are both reduced relatively. And the mass composition of oily sand samples changes regularly, i.e. saturated hydrocarbons increases greatly from 44.06% to 62.22% along the experimental noumenon (from oily sand sample 3 to oily sand sample 1) (Fig. 2), and the contents of asphaltene and non-hydrocarbon is reduced. And then, the ratios of Pr / nC17 and Ph / nC18 are reduced gradually from the oily sand sample 3 to oily sand sample 1, while the ratios of C(21 + 22) / − + C(28 + 29), C21 / C22 increase gradually. Some researchers believe that the geochromatographic effect is due to the sorption that occurs not only between nitrogen compounds and minerals, but also between other compounds and minerals (Milles, 1990). Therefore, these changes may be related to with the geochromatographic effect, which occurs during the process of hydrocarbon migration. 3.2. Dissolution phenomena of oily sand samples
3. Results and analysis 3.1. Changes in chemical composition of the samples after reaction Compared with the crude oil samples, the contents of asphaltene and non-hydrocarbon in the samples after reaction is reduced, while the amount of saturated hydrocarbons increases greatly to 79.16%. Also, the ratios of
The results of scanning electron microscopy on the oily sand samples shows that a certain degree of dissolution has occurred compared with the natural sand during crude oils migrate along the apparatus. And the farther the oil migrates, the stronger the dissolution is. For instance, on the quartz surface did the light dissolution occur within the lower part of the apparatus according to the scanning electron photomicrographs of
Fig. 3. SiO2 alteration-scanning electron photomicrographs of sandstone texture. 1—Surface of quartz; 2—Grains occurred dissolution; 3—Pore spaces being dissolved with the strengthen of interaction of oil–water–rock.
136
X. Gong et al. / Journal of Geochemical Exploration 89 (2006) 133–137
Fig. 4. Potash feldspar ores alteration-scanning electron photomicrographs of sandstone texture.
oily sand sample 3; the photomicrograph of oily sand sample 1 within the upper part of the apparatus, however, shows bigger pore spaces dissolved with the strengthen of interaction of oil–water–rock than that of oily sand sample 2 and sample 3 (Fig. 3). As far as the composition of the sandstones is concerned, however, the dissolutions are different. Compared to quartz, the dissolution that occurred within the albite and potash feldspar is much greater and even leads to the formation of dissolved pore spaces (Fig. 4). According to some previous studies, it is the organic acid which increases the dissolution of minerals (Zhang et al., 2000). This kind of organic acid may result from the interactions between oil and pore water, or results from the heating of crude oil (Kharaka et al., 1993), and it has the positive correlation with the amount of pore water (Zhang et al., 2000). As enough formation water samples collected from the Es4 formation in the Bonan sub-sag had been injected into the apparatus before adding crude oil samples, which will play an important role for supplying the organic acid for the apparatus. It was likely the organic acid that caused the occurrence of the dissolution within the grains and came into being pores among the grains. So, this kind of dissolutions within deep formations can produce effective secondary pores, which is helpful for improving the physical property of deep reservoirs.
Some specific changes are as follows: ① many changes took place in rock structure and its chemical components of its contained hydrocarbon. Both the biomarkers and family components of the samples derived from experiment show the existence of the geochromatographic effect during the oil migration along the apparatus. ② Dissolution, to some extent, has affected the mineral components of the oily-sands during the oil– water–rock interaction. And it strengthens gradually during hydrocarbon migration from the bottom to the top of the apparatus, which can provide effective space for hydrocarbons to migrate and accumulate within the deep zones. Acknowledgements The research was funded by both the AAPG Foundation 2002 Grants-in-Aid together with the National Science Foundation of China (No. 40472075). The authors would like to thank Mr. ZHU Yixiu, ZHU Lei and Ms. LI Sumei, the researchers of the China University of Petroleum, and Ms. Li Huili, who works in the Institute of Oil Exploration and Development of SINOPEC, for their constructive suggestions on the manuscript. Also, the authors would like to thank Mr. SUN Xiwen, the senior engineer of the Geological Science Institute of Shengli Oilfield, for help in collecting the field samples.
4. Discussion and conclusions References The results of the simulation show that, under certain temperature and pressure conditions, many changes in the chemical components and the inner structure of rocks, etc., occurred during oil migration from the bottom to the top of the experimental apparatus with the increased charging amount of crude oil, as well as the interactions with sandstone and formation water.
Cai, C.F., Mei, B.W., Ma, T., et al., 1996. Hydrocarbon–water–rock interactions in the diagenetically altered system near major unconformities in Tarim Basin. Chinese Science Bulletin 41 (19), 1631–1635. Kharaka, Y.K., Lungedard, P.D., Ambats, G., et al., 1993. Generation of a liphatic acid anions and carbon dioxide by hydrous pyrolysis of crude oils. Applied Geochemistry 8, 317–324.
X. Gong et al. / Journal of Geochemical Exploration 89 (2006) 133–137 Milles, J.A., 1990. Secondary migration routes in the Brent sandstones of the Viking Granben and East Shetland basin: evidence from oil residues and subsurface pressure data. AAPG Bulletin 74, 1718–1735. Qiao, H.S., Fang, C.L., Niu, J.Y., et al., 2002. Petroleum geology of the deep horizons in East China, Beijing. Petroleum Industry Press, Beijing, pp. 254–255. Wendebourg, J., 2000. Modeling multi-component petroleum fluid migration in sedimentary basins. Journal of Geochemical Exploration 69–70, 651–656.
137
Yin, C.H., 2003. Study on geochemistry of deep oil and gas pool in Jiyang depression. Preserved in Working Station of Post D. Zhang, Z.H., Hu, W.X., Zeng, J.H., et al., 2000. Study of fluid-rock interactions in Eogene formation in Dongying depression, Bohai Gulf Basin. Acta Sedimentologica Sinica 18 (4), 560–566.