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Characteristics of Paleozoic clastic reservoirs and the relationship with hydrocarbon accumulation in the Tazhong area of the Tarim Basin, west China

Characteristics of Paleozoic clastic reservoirs and the relationship with hydrocarbon... 192 192 Pet.Sci.(2010)7:192-200 DOI 10.1007/s12182-010-0024-x Characteristics of Paleozoic clastic reservoirs and the relationship with hydrocarbon accumulation in the Tazhong area of the Tarim Basin, west China 1 2, 3 1 2, 3 Wang Zhaoming , Liu Luofu , Yang Haijun , Wang Weili , Zhang 1 1 Baoshou and Han Jianfa PetroChina Tarim Oilfi eld Company, Korla, Xinjiang 841000, China State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China Basin and Reservoir Research Center, China University of Petroleum, Beijing 102249, China © China University of Petroleum (Beijing) and Springer-Verlag Berlin Heidelberg 2010 Abstract: In order to predict favorable exploration areas of the Paleozoic, Carboniferous and Silurian clastic reservoirs in the Tazhong area of the Tarim Basin, west China, we studied the basic characteristics of Paleozoic clastic reservoirs in the Tazhong area based on a lot of data. Several issues about the hydrocarbon accumulation related to the reservoirs were also discussed. The results were concluded that: the high-value areas of the porosity and permeability of clastic reservoirs were located in the southeast of the Tazhong area; the content of cement (carbonate cement in particular) was the main factor controlling the porosity and permeability of clastic reservoirs; the hydrocarbon distributions of Carboniferous and Silurian clastic reservoirs were closely related to the porosity and permeability; the favorable hydrocarbon accumulation areas of the two sets of strata were located in the southeast of this area, especially in the updip pinch-out area. Key words: Clastic reservoir, Carboniferous, Silurian, Paleozoic, hydrocarbon accumulation, Tazhong area, Tarim Basin and permeability in different areas, discussed the main factors 1 Introduction controlling porosity and permeability of reservoirs, and In the Tazhong area of the Tarim Basin, the Paleozoic searched for the relationship between reservoir characteristics clastic rock is the major hydrocarbon-producing stratum, and hydrocarbon distribution, expecting to provide basic and plays a vital role in the hydrocarbon exploration and information for the next step of exploration and development. development of the basin (Liu et al, 1995; Jia et al, 2006; Sun et al, 2005; Liu et al, 2004). Up to now, many scholars 2 Basic characteristics of Paleozoic clastic have done detailed research on Paleozoic reservoirs in this reservoirs in the Tazhong area area (Shen et al, 2006; Li et al, 2000; Wang and Lü, 2004; Dai et al, 2001; Chen et al, 1999; Liu et al, 2008) and have The Paleozoic clastic reservoirs in the Tazhong area of the obtained fruitful results. A lot of work has been carried Tarim Basin are mainly distributed in the Carboniferous and out especially on the characteristics of a single reservoir Silurian strata which are currently the hydrocarbon-producing in the well blocks. However, research on the comparison strata and are also the next exploration targets in this area among different reservoirs and the changes of reservoir (Table 1). characteristics in the plane is relatively weak. In this study, 2.1 Carboniferous Donghe sandstone based on a large amount of data (such as rock-plug porosity and permeability of reservoirs in the single-wells, planar The Donghe sandstone (i.e., the oil group C ), widely III sedimentary facies, fracture distribution, thin section distributed in the Tazhong area (Zhong et al, 2004; Gu, 1996; analysis and reservoir characteristics), we investigated the Zhu et al, 2004; Wu et al, 2006), is generally buried at a characteristics of Carboniferous and Silurian reservoirs in the shallow depth of 3,500-3,700 m (Gu et al, 2006), and contains Tazhong area macroscopically, compared the characteristics lithic quartz sandstone, feldspar-lithic quartz sandstone and among different systems, analyzed the changes of porosity lithic sandstone, with a small amount of quartz sandstone. On the whole, the content of rock debris is high (Fig. 1). That of quartz is 65% in general, mostly over 70% with higher *Corresponding author. email: liulf@cup.edu.cn compositional maturity. Because of the various sedimentary Received September 2, 2009 Pet.Sci.(2010)7:192-200 193 193 194 Pet.Sci.(2010)7:192-200 0 3 10 50 100 >100 0 8 12 15 20 >20 -3 2 Porosity, % Permeability, ×10 μm (a) (b) Fig. 3 Frequency distribution of porosity (a) and permeability (b) of the Carboniferous Donghe sandstone in the Tazhong area, Tarim Basin Quartz 8.0 10 10 o TZ111 6.0 * TZ32 o TZ47 25 25 4.0 o o o + TZ58 Feldspar-lithic o*+ o + o TZ62 o o + o o oo quartz sandstone o * 2.0 ** + + 50 50 * ** * * + +* ** * * + *+ * 0.0 Residual Dissolved Dissolved Dissolved Mould Microporosity primary pores pores pores pores o o o o o o o o oo o o o o o o intergranular between around in grains oo o o o o o o o o o o o o pores grains grains Lithic Pore type sandstone Frequency distribution of porosity types of the Carboniferous Fig. 4 Donghe sandstone reservoir in the Tazhong area, Tarim Basin 75 50 Feldspar Debris st (a) The 1 upper submember -3 2 and the permeability is (0.01-300)×10 μm in general (Fig. Quartz 6(a)). However, the values of porosity and permeability are + TZ111 -3 2 mostly low, 0-9% and 0-2×10 μm respectively (Fig. 7), TZ112 10 10 TZ117 accounting for over 60% of the total number of samples, so Lithic quartz TZ122 the reservoir is poor. A relatively good linear relationship sandstone + TZ47 25 + 25 + * * between porosity and permeability also exists (Fig. 6). The * * + * + + TZ58 * + + + + + + + ** * Feldspar-lithic *** + * * + * st **+ * * *+ + + * * + + + + * * + + ** * * + + + + * * * TZ62 main pore types of the 1 upper submember are also primary * + + + + + * * quartz sandstone +* * * * + * * ** * * + + *+** * + + + * * ** *** * ** * * * * * * ** * ** * * *** * ** * ** * * * * * * ** * * * ** ** *** * * * ** * * ** TZ67 ** ** ** ** ** ** ** * * * * ** * ** * ** * * * intergranular pores and intergranular dissolved pores (Fig. 8). * ** ** 50 * 50 *** * ** TZ69 rd The 3 upper submember also consists mainly of lithic TZ77 * * ** sandstone and a small portion of lithic quartz sandstone. * * * ** st Compared with the 1 upper submember, it has a larger Lithic amount of feldspar-lithic quartz sandstone (Fig. 5(b)). rd sandstone Nevertheless, the sandstone maturity of the 3 upper submember is still relatively low and the quartz content is generally 25%-75%. The porosity and permeability are also poor and their values are basically the same as those of the 25 75 50 Feldspar Debris st 1 upper submember. They are also distributed mainly in rd (b) The 3 upper submember low-value areas, and there are relatively large differences rd among different regions. Overall, the 3 upper submember Fig. 5 Triangular diagram of the composition of the st is better than the 1 upper submember (Fig. 7). A relatively Silurian sandstone in the Tazhong area, Tarim Basin good linear relationship between porosity and permeability rd From the comparison of reservoir properties, it can be also exists (Fig. 6). The main type of porosity of the 3 concluded that the Carboniferous Donghe sandstone reservoir upper submember is primary intergranular, and intergranular is better than the Silurian reservoir. dissolved porosity is less (Fig. 8). Average surface porosity, % Frequency, % Frequency, % Pet.Sci.(2010)7:192-200 195 Break Break Break Break Break Break Slope Slope Slope Slope Slope Slope No.1 No.1 No.1 No.1 No.1 No.1 1. 0 The The The The The The 1 0 Zone Zone Zone Zone Zone Zone 8 8 1 12 2 1. 0 1.0 196 Pet.Sci.(2010)7:192-200 TZ49 TZ49 TZ45 TZ45 N N TZ63 TZ63 TZ85 TZ85 TZ47 TZ47 TZ66 TZ66 TZ21 TZ21 TZ40 TZ40 TZ68 TZ68 TZ67 TZ67 TZ10 TZ10 TZ54 TZ54 TZ20 TZ20 TZ13 TZ13 TZ11 TZ11 TZ82 TZ82 TZ14 TZ14 TZ12 TZ12 TZ83 TZ83 TZ50 TZ50 TZ46 TZ46 TZ37 TZ72 TZ37 TZ72 TZ84 TZ84 TZ17 TZ9 TZ17 TZ9 TZ2 TZ62 TZ2 TZ62 TZ15 TZ15 TZ403 TZ403 TZ4 TZ58 TZ4 TZ58 TZ408 TZ408 TZ22 TZ22 TZ16 TZ16 TZ79 TZ79 TZ401 TZ401 TZ43 TZ43 TZ24 TZ24 TZ6 TZ6 TZ103 TZ103 TZ26 TZ26 TZ7 TZ7 TZ53 TZ53 TZ104 TZ104 TZ 5 TZ5 TZ78 TZ78 TZ52 TZ52 TZ38 TZ38 TZ3 TZ3 TZ60 TZ60 Legend Legend TZ3 TZ3 Wedge-out Poros ity Well Wedge-out Permeability Well line is oline location line isoline location (a) Porosity (b) Permeability Fig. 9 Porosity (a) and permeability (b) distribution of the Carboniferous Donghe sandstone in the Tazhong area, Tarim Basin TZ452 TZ452 TZ49 TZ49 TZ451 TZ451 TZ45 TZ45 TZ63 TZ63 TZ85 TZ85 TZ47 TZ47 TZ35 TZ35 TZ66 TZ66 TZ21 TZ21 TZ67 TZ67 TZ10 TZ10 TZ54 TZ54 TZ20 TZ20 TZ112 TZ112 TZ201 TZ11 TZ13 TZ201 TZ13 TZ11 TZ111 TZ111 TZ18 TZ18 TZ82 TZ82 TZ14 TZ14 TZ122 TZ122 TZ12 TZ80 TZ12 TZ80 TZ46 TZ46 TZ50 TZ50 TZ37 TZ30 TZ37 TZ30 TZ19 TZ19 TZ44 TZ44 TZ15 TZ17 TZ15 TZ9 TZ17 TZ9 TZ61 TZ77 TZ61 TZ77 TZ58 TZ58 TZ69 TZ69 TZ22 TZ22 TZ4 TZ16 TZ4 TZ16 TZ401 TZ401 TZ43 TZ6 TZ43 TZ6 TZ103 TZ103 TZ261 TZ261 TZ101 TZ101 TZ52 TZ52 TZ60 Legend TZ60 Legend TZ3 TZ3 Wedge-out Permeability Well Wedge-out Porosity Well line isoline location line isoline location (a) Porosity (b) Permeability st Porosity (a) and permeability (b) distribution of the 1 upper submember of the Silurian Kepingtage Formation in the Tazhong area, Tarim Basin Fig. 10 TZ452 TZ452 TZ49 TZ49 TZ451 TZ451 TZ45 TZ45 N N TZ63 TZ63 TZ47 TZ47 TZ85 TZ85 TZ66 TZ66 TZ35 TZ35 TZ21 TZ21 TZ67 TZ67 TZ10 TZ10 TZ20 TZ20 TZ54 TZ54 TZ112 TZ112 TZ201 TZ201 TZ13 TZ11 TZ13 TZ11 TZ111 TZ18 TZ111 TZ18 TZ82 TZ82 TZ14 TZ14 TZ122 TZ122 TZ12 TZ12 TZ80 TZ30 TZ80 TZ30 TZ50 TZ50 TZ46 TZ46 TZ37 TZ37 TZ17 TZ19 TZ17 TZ19 TZ15 TZ15 TZ61 TZ61 TZ77 TZ77 TZ9 TZ9 TZ62 TZ62 TZ69 TZ69 TZ22 TZ22 TZ4 TZ16 TZ4 TZ16 TZ401 TZ401 TZ79 TZ79 TZ43 TZ43 TZ6 TZ6 TZ103 TZ103 TZ261 TZ261 TZ101 TZ101 TZ52 TZ52 TZ60 TZ60 Legend Legend TZ3 TZ3 Wedge-out Permeability Well Wedge-out Porosity Well line isoline location line isoline location (b) Permeability (a) Porosity rd Fig. 11 Porosity (a) and permeability (b) distribution of the 3 upper submember of the Silurian Kepingtage Formation in the Tazhong area, Tarim Basin 10 0 0 15 60 km 15 30 60 km 30 45 60 km 30 45 60 km 15 30 60 km 45 60 km 1 0 100 Pet.Sci.(2010)7:192-200 197 Calcite 4 The content of cement (especially 1% 5% 1% Ferrous calcite carbonate cement) is the main factor Dolomite 33% controlling the porosity and permeability of 23% Ankerite clastic reservoirs 12% 25% Silica The statistics of the interstitial material contents from Gypsum many wells in the east and west of the Tazhong area show Pyrite that the cement is the major interstitial material influencing the porosity and permeability of the Carboniferous Donghe Cement contents of the Carboniferous Donghe sandstone Fig. 13 reservoir in the Tazhong area, Tarim Basin sandstone reservoirs, especially the carbonate cement (Fig. 12). It can be seen from Fig. 12 that, the higher the interstitial material content, the lower the porosity, and vice versa. When an important reason why the former has better reservoir the cement content is less than 5%, the porosity is generally properties than the latter. The contents of interstitial material greater than 12%. When the cement content is greater than rd and cement of the 3 upper submember are less than those 5%, the porosity is generally less than 12%. The main type of st of the 1 upper submember, but the matrix contents of them cement is carbonate, accounting for 92% of the total content are similar (Fig. 17). So the differences between the two (Fig. 13), being mainly calcite, ferrous calcite, dolomite submembers are mainly caused by carbonate cement and and ankerite. Through the comparison between interstitial are not related with the matrix content. There is a negative material content and porosity and permeability values of correlation between the interstitial material content and the Donghe sandstone reservoirs from wells TZ40 and TZ75, it porosity and permeability. With the increase of interstitial was found that there was a good correlation, and the layer material content, the porosity and permeability of the with low interstitial material content especially low cement reservoir decreased in general. The negative correlation also content had high values of porosity and permeability (Fig. exists between the carbonate content and the porosity and 14). For example, the cement content of Donghe sandstone permeability, which indicates that the carbonate cementation reservoir below 3,716 m from well TZ75 decreased, while plays a leading role in the diagenetic cementation of the the porosity and permeability increased significantly. When Silurian reservoirs in the study area (Fig. 18). the cement content above 3,716 m increased, the reservoir Through the discussion above, we believe that the cement properties became poor. content (especially carbonate cement content) is the main factor controlling the porosity and permeability of clastic reservoirs in this area. The differences between the Silurian and Carboniferous clastic reservoirs are related with the compositional maturity. 5 The hydrocarbon distribution of Carboniferous and Silurian clastic reservoirs in the Tazhong area is closely related to the reservoir properties The reservoir is one of the most basic conditions to form hydrocarbon accumulations and the pores in the reservoir provide the space to store oil and gas. Therefore, the size and connectivity of the pores directly infl uence the accumulation and distribution of oil and gas (Wang, 2001; Cai, 2005; Yu et al, 2005; Wang et al, 2008; Liu et al, 1996). In order to search Matrix Cements Matrix Cements Matrix Cements Matrix Cements for the relationship between hydrocarbon distribution of Porosity > 12% Porosity < 12% Porosity > 12% Porosity < 12% Carboniferous and Silurian clastic reservoirs and the porosity and permeability, we plotted matching maps between the Western Eastern porosity and permeability and hydrocarbon distribution of the rd Fig. 12 Interstitial material contents of the Carboniferous Donghe 3 upper submember of the Silurian Kepingtage Formation sandstone reservoir in the Tazhong area, Tarim Basin and Carboniferous Donghe sandstone (Figs. 19 and 20). It can be found that the Carboniferous Donghe sandstone reservoirs Similar to the Carboniferous clastic reservoir, the main have been discovered in the area where the porosity of cement of the Silurian reservoir is also carbonate cement reservoir is high, which is more than 8%. For instance, most (Figs. 15 and 16). The contents of carbonate cement of the of the reservoirs in the TZ4-TZ1, TZ16 and TZ24 well blocks st rd 1 and 3 upper submembers are 95% and 89%, respectively, in the southeast and the TZ47, TZ40 and TZ10 well blocks in and the cements are mainly calcite, ferrous calcite, dolomite the northwest are located in the area with the porosity more rd and ankerite. The cement content of the 3 upper submember than 10% (Fig. 19), that is, the high-value areas of porosity st is less than that of the 1 upper submember, which is also control the hydrocarbon distribution. For clastic reservoirs, Interstitial material content, % 3720 3740 Donghe sandstone member 198 Pet.Sci.(2010)7:192-200 Content of Content of Content of Grain size Total surface Content of interstitial impurity max value carbonate DepthLithological Permeability porosity Horizon Quartz Feldspar Cuttings Porosity cement 0 0.6 material matrix cement m column min value 0 100 0 100 0 100 0 25 0. 001 1000 0 50 0 50 0 30 0 30 0 30 0 0.6 Relationship between interstitial material content and porosity and permeability of the Carboniferous Donghe Fig. 14 sandstone reservoir at well TZ75 in the Tazhong area, Tarim Basin Calcite 0% Ferrous calcite 3% 2% Dolomite 8% 4% Ankerite 4% Silica 79% Gypsum Pyrite st Fig. 15 Cement content of the Silurian 1 upper submember reservoir in the Tazhong area, Tarim Basin Calcite 3% 4% 4% Ferrous calcite Dolomite 25% 56% Ankerite Interstitial Interstitial Impurity Impurity Cement Cement Silica material material matrix matrix Gypsum 3% 5% rd st 3 upper subm em ber 1 upper subm em ber Pyrite rd Fig. 17 Interstitial material content of the Silurian reservoir in Cement content of the Silurian 3 upper submember reservoir in Fig. 16 the Tazhong area, Tarim Basin the Tazhong area, Tarim Basin rd such a correlation between hydrocarbon distribution and and they are mainly in the 3 upper submember (Fig. permeability also exists in these areas. 20). Similar to the distribution of Carboniferous Donghe At present, there are four Silurian reservoirs including sandstone reservoirs, the Silurian reservoirs are all located in rd TZ47, TZ11, TZ12-TZ50 and TZ16 in the Tazhong area, the high-value areas of porosity of the 3 upper submember Interstitial material content, % Break Break Slope Slope No.1 No. 1 Zone The The 1 . 0 Zone 1 0 1 0 0 1 0 1 0 1 0 1 0 Pet.Sci.(2010)7:192-200 199 100 100 10 10 15 15 1 1 0.1 0.1 5 5 0.01 0.01 5 10 15 0 5 10 15 02 4 68 10 12 0 5 10 15 Content of Content of Content of Content of interstitial material, % interstitial material, % carbonate cement, % carbonate cement, % Fig. 18 Relationship between reservoir properties and interstitial material or carbonate cement content of rd the Silurian 3 upper submember at well TZ111 in the Tazhong area, Tarim Basin with the porosity greater than 8% (Fig. 20). Because of the TZ49 TZ45 relationship between reservoir distribution and high-value TZ63 TZ85 areas of porosity, it can be considered that the distribution TZ47 47 TZ66 TZ21 TZ40 Z40 of clastic reservoirs in the study area is closely related to the TZ68 TZ67 TZ10 TZ10 properties of reservoirs. TZ54 T TZ20 TZ13 TZ11 TZ82 TZ14 TZ12 TZ83 TZ50 6 Prediction of favorable hydrocarbon TZ46 TZ72 TZ37 TZ84 TZ17 TZ9 TZ2 TZ62 TZ15 TZ15 TZ403 exploration targets of Paleozoic clastic TZ4 Z4 TZ58 T TZ5 TZ408 TZ408 TZ22 TZ1 TZ16 TZ79 TZ79 TZ4 TZ401 reservoirs in the Tazhong area TZ43 TZ TZ24 TZ6 6 TZ103 TZ1 TZ26 TZ7 TZ104 TZ104 TZ53 The high-value areas of the properties of Carboniferous TZ5 TZ78 TZ52 and Silurian clastic reservoirs are located in the southeast of TZ38 TZ3 TZ60 the Tazhong area. The main factor controlling the properties Legend TZ3 of clastic reservoirs is the cement content (especially the Wedge-out Porosity Well Oil reservoir Condensate line isoline location gas reservoir carbonate cement content). The hydrocarbon distribution of the Carboniferous and Silurian is closely related to the Matching map between porosity and distribution of the Carboniferous Fig. 19 reservoir properties and is generally in the high-value areas Donghe sandstone reservoirs in the Tazhong area, Tarim Basin of porosity and permeability. In other words, the basis for predicting favorable hydrocarbon exploration areas is the TZ452 TZ49 TZ451 porosity and permeability of reservoirs. Therefore, the TZ45 TZ63 hydrocarbon exploration of the two sets of strata should be TZ47 TZ85 TZ66 focused on the southeast of the Tazhong area, especially TZ35 TZ21 on the updip pinch-out area. However, due to the local TZ67 TZ10 TZ20 TZ54 TZ112 sedimentation or the post-depositional reconstruction, the TZ201 TZ13 TZ11TZ111 TZ18 TZ82 TZ14 TZ122 clastic reservoirs of the two sets of strata can also form high- TZ12 TZ80 TZ30 TZ50 TZ46 value areas of porosity and permeability in the middle of the TZ37 TZ17 TZ19 TZ15 TZ61 TZ77 TZ9 Tazhong area, which should also be considered as favorable TZ62 TZ69 TZ22 TZ4 TZ16 TZ401 exploration areas, such as the Donghe sandstone reservoir in TZ79 TZ43 TZ6 TZ103 TZ261 the TZ66-TZ54 well block near the No.1 slope break zone TZ101 in the northern part of the middle Tazhong area (the porosity TZ52 values are higher than 10%) and the TZ46-TZ37 well block Legend TZ60 in the southern part (the porosity values are higher than 12%). rd TZ3 For the 3 upper submember of the Silurian Kepingtage Wedge-out Porosity Well Oil reservoir line isoline location Formation, the TZ67-TZ54 well block near the No.1 slope break zone in the northern part of the middle Tazhong area, rd Fig. 20 Matching map between porosity and distribution of the 3 upper the TZ17-TZ37 well block in the southern part, and the submember reservoir of the Silurian Kepingtage Formation in the Tazhong TZ83-TZ44 well block in the southeastern part, with porosity area, Tarim Basin 10 0 1 0 0 1 0 0 Porosity, % -3 2 Permeability, ×10 μm Porosity, % -3 2 Permeability, ×10 μm 200 200 Pet.Sci.(2010)7:192-200 Petroleum University. 2001. 23(4): 1-5 (in Chinese) values more than 10%, should be regarded as favorable areas. Gu J Y. Sedimentary environment and reservoir characters of the In fact, the TZ66-TZ54 well block of the Carboniferous and Carboniferous Donghe sandstone in the Tarim Basin. Acta Geologica the TZ67-TZ54 well block of the Silurian are overlapped Sinica. 1996. 70(2): 153-161 (in Chinese) with each other, so are the TZ46-TZ37 and TZ17-TZ37 well Gu J Y, Zhang X Y and Guo B C. Characteristics of sedimentation and blocks. Therefore, we should strengthen the exploration in reservoir of the Donghe sandstone in Tarim Basin and their synthetic the two areas, expecting to find Carboniferous and Silurian analysis. Journal of Palaeogeography. 2006. 8(3): 285-294 (in reservoirs. However, the above prediction is based on the Chinese) reservoir characteristics. In order to obtain more objective Jia J H, Zhang B M, Zhu S H, et al. Stratigraphy, sedimentary understanding, research on hydrocarbon accumulation and characteristics and lithofacies palaeogeography of the Silurian in preservation conditions should also be carried out. Tarim Basin. Journal of Palaeogeography. 2006. 8(3): 339-351 (in Chinese) 7 Conclusions Li Y P, Li X S, Zhou Y, et al. Sedimentary characteristics and evolution history of middle-upper Ordovician in Tazhong area. Xinjiang 1) The Donghe sandstone mainly consists of lithic quartz Petroleum Geology. 2000. 21(3): 133-137 (in Chinese) sandstone, and the compositional maturity is high. Generally, Liu J D, Zhang S N, Tian J C, et al. Discussion on exploration direction -3 2 the porosity is 3%-20% and the permeability is 0.1×10 μm - and depositional system of Silurian-Devonian in Tarim Basin, -3 2 China. 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The cement content Gas Technology. 1995. 17(3): 8-12 (in Chinese) is the main factor controlling the reservoir properties. The Liu S P, Zhong G F, Liu X F, et al. Characteristics and evaluation of higher the interstitial material content, the lower the porosity, Silurian sandstone reservoir in Tazhong area, Tarim Basin. Journal of and vice versa. The Carboniferous Donghe sandstone Oil and Gas Technology. 1996. 18(4): 21-25 (in Chinese) She n A J, Wang Z M, Yang H J, et al. Genesis classification and reservoirs are better than the Silurian reservoirs on the whole. characteristics of Ordovician carbonate reservoirs and petroleum 2) The high-value areas of porosity and permeability of exploration potential in Tazhong region, Tarim Basin. Marine Origin clastic reservoirs are located in the southeast of the Tazhong Petroleum Geology. 2006. 11(4): 1-12 (in Chinese) area. This distribution characteristic is closely related to the Sun L D, Zhou X Y and Wang G L. Contributions of petroleum geology shallow water deposits in the southeastern part, relatively and main directions of oil-gas exploration in the Tarim Basin. high structural position and shallow burial depth. Because Chinese Journal of Geology (Scientia Geologica Sinica). 2005. the reservoir properties control hydrocarbon distribution, 40(2): 167-178 (in Chinese) exploration of the Carboniferous and Silurian clastic rocks in Wan g G C. Characteristics of clastic reservoirs in the Tarim Basin. the Tazhong area should be directed at the southeastern part. Petroleum Geology & Experiment. 2001. 23(1): 62-66 (in Chinese) 3) The discovered Paleozoic reservoirs in the Tazhong Wan g P, Liu L F, Li Y, et al. Reservoir characteristics of the 3rd upper area have a good matching relationship with the high-value sub-member of the Silurian Kepingtage Formation in Tazhong area and their relations to oil and gas distribution. Oil & Gas Geology. areas of porosity, and are located in the area with the porosity 2008. 29(2): 174-180 (in Chinese) more than 8%. The basis for predicting favorable hydrocarbon Wan g S M and Lü X X. Features and petroleum significance of exploration areas is the porosity and permeability of Ordovician carbonate reservoir in Tazhong area, Tarim Basin. reservoirs. Therefore, the hydrocarbon exploration of the Journal of Xi’an Shiyou University (Natural Science Edition). 2004. two sets of strata should be focused on the southeast of the 19(4): 72-76 (in Chinese) Tazhong area, especially on the updip pinch-out area. Wu C J, Dai Z Y and Liu S H. Study on the physical factors of Carboniferous Donghe sandstone reservoir in Tazhong area. Acknowledgements Contributions to Geology and Mineral Resources Research. 2006. 21(3): 199-202 (in Chinese) This work is supported by the Basic Research Program of Yu R L, Yan X B, Jin X H, et al. Research achievements and exploration China (973 Program, Grant No. 2006CB202308). direction in Tarim Basin. Oil & Gas Geology. 2005. 26(5): 598-604 (in Chinese) References Zho ng D K, Zhu X M, Zhou X Y, et al. Effect of structure on sandstone’s Cai X Y. Reservoiring conditions and exploration targets in Tarim Basin. porosity evolution: a case study from the Donghe sandstones in Oil & Gas Geology. 2005. 26(5): 590-597 (in Chinese) central Tarim. Chinese Journal of Geology (Scientia Geologica Che n J S, Wang Z Y, Dai Z Y, et al. Study of the middle and upper Sinica). 2004. 39(2): 214-222 (in Chinese) Ordovician rimmed carbonate platform system in the Tazhong area, Zhu X M, Zhang Q, Zhao C L, et al. Sedimentary facies and Tarim Basin. Journal of Palaeogeography. 1999. 1(2): 8-17 (in environmental changes of the Donghe sandstone in central Tarim. Chinese) Chinese Journal of Geology (Scientia Geologica Sinica). 2004. Dai Z Y, Zhou Y, Chen J S, et al. The characteristics and evaluation 39(1): 27-35 (in Chinese) of middle & upper Ordovician reef & shoal related carbonate reservoir in Tazhong North Slope, Tarim Basin. Journal of Southwest (Edited by Hao Jie) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Petroleum Science Springer Journals

Characteristics of Paleozoic clastic reservoirs and the relationship with hydrocarbon accumulation in the Tazhong area of the Tarim Basin, west China

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Springer Journals
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Copyright © 2010 by China University of Petroleum (Beijing) and Springer-Verlag Berlin Heidelberg
Subject
Earth Sciences; Mineral Resources; Industrial Chemistry/Chemical Engineering; Industrial and Production Engineering; Energy Economics
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1672-5107
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1995-8226
DOI
10.1007/s12182-010-0024-x
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Abstract

192 192 Pet.Sci.(2010)7:192-200 DOI 10.1007/s12182-010-0024-x Characteristics of Paleozoic clastic reservoirs and the relationship with hydrocarbon accumulation in the Tazhong area of the Tarim Basin, west China 1 2, 3 1 2, 3 Wang Zhaoming , Liu Luofu , Yang Haijun , Wang Weili , Zhang 1 1 Baoshou and Han Jianfa PetroChina Tarim Oilfi eld Company, Korla, Xinjiang 841000, China State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China Basin and Reservoir Research Center, China University of Petroleum, Beijing 102249, China © China University of Petroleum (Beijing) and Springer-Verlag Berlin Heidelberg 2010 Abstract: In order to predict favorable exploration areas of the Paleozoic, Carboniferous and Silurian clastic reservoirs in the Tazhong area of the Tarim Basin, west China, we studied the basic characteristics of Paleozoic clastic reservoirs in the Tazhong area based on a lot of data. Several issues about the hydrocarbon accumulation related to the reservoirs were also discussed. The results were concluded that: the high-value areas of the porosity and permeability of clastic reservoirs were located in the southeast of the Tazhong area; the content of cement (carbonate cement in particular) was the main factor controlling the porosity and permeability of clastic reservoirs; the hydrocarbon distributions of Carboniferous and Silurian clastic reservoirs were closely related to the porosity and permeability; the favorable hydrocarbon accumulation areas of the two sets of strata were located in the southeast of this area, especially in the updip pinch-out area. Key words: Clastic reservoir, Carboniferous, Silurian, Paleozoic, hydrocarbon accumulation, Tazhong area, Tarim Basin and permeability in different areas, discussed the main factors 1 Introduction controlling porosity and permeability of reservoirs, and In the Tazhong area of the Tarim Basin, the Paleozoic searched for the relationship between reservoir characteristics clastic rock is the major hydrocarbon-producing stratum, and hydrocarbon distribution, expecting to provide basic and plays a vital role in the hydrocarbon exploration and information for the next step of exploration and development. development of the basin (Liu et al, 1995; Jia et al, 2006; Sun et al, 2005; Liu et al, 2004). Up to now, many scholars 2 Basic characteristics of Paleozoic clastic have done detailed research on Paleozoic reservoirs in this reservoirs in the Tazhong area area (Shen et al, 2006; Li et al, 2000; Wang and Lü, 2004; Dai et al, 2001; Chen et al, 1999; Liu et al, 2008) and have The Paleozoic clastic reservoirs in the Tazhong area of the obtained fruitful results. A lot of work has been carried Tarim Basin are mainly distributed in the Carboniferous and out especially on the characteristics of a single reservoir Silurian strata which are currently the hydrocarbon-producing in the well blocks. However, research on the comparison strata and are also the next exploration targets in this area among different reservoirs and the changes of reservoir (Table 1). characteristics in the plane is relatively weak. In this study, 2.1 Carboniferous Donghe sandstone based on a large amount of data (such as rock-plug porosity and permeability of reservoirs in the single-wells, planar The Donghe sandstone (i.e., the oil group C ), widely III sedimentary facies, fracture distribution, thin section distributed in the Tazhong area (Zhong et al, 2004; Gu, 1996; analysis and reservoir characteristics), we investigated the Zhu et al, 2004; Wu et al, 2006), is generally buried at a characteristics of Carboniferous and Silurian reservoirs in the shallow depth of 3,500-3,700 m (Gu et al, 2006), and contains Tazhong area macroscopically, compared the characteristics lithic quartz sandstone, feldspar-lithic quartz sandstone and among different systems, analyzed the changes of porosity lithic sandstone, with a small amount of quartz sandstone. On the whole, the content of rock debris is high (Fig. 1). That of quartz is 65% in general, mostly over 70% with higher *Corresponding author. email: liulf@cup.edu.cn compositional maturity. Because of the various sedimentary Received September 2, 2009 Pet.Sci.(2010)7:192-200 193 193 194 Pet.Sci.(2010)7:192-200 0 3 10 50 100 >100 0 8 12 15 20 >20 -3 2 Porosity, % Permeability, ×10 μm (a) (b) Fig. 3 Frequency distribution of porosity (a) and permeability (b) of the Carboniferous Donghe sandstone in the Tazhong area, Tarim Basin Quartz 8.0 10 10 o TZ111 6.0 * TZ32 o TZ47 25 25 4.0 o o o + TZ58 Feldspar-lithic o*+ o + o TZ62 o o + o o oo quartz sandstone o * 2.0 ** + + 50 50 * ** * * + +* ** * * + *+ * 0.0 Residual Dissolved Dissolved Dissolved Mould Microporosity primary pores pores pores pores o o o o o o o o oo o o o o o o intergranular between around in grains oo o o o o o o o o o o o o pores grains grains Lithic Pore type sandstone Frequency distribution of porosity types of the Carboniferous Fig. 4 Donghe sandstone reservoir in the Tazhong area, Tarim Basin 75 50 Feldspar Debris st (a) The 1 upper submember -3 2 and the permeability is (0.01-300)×10 μm in general (Fig. Quartz 6(a)). However, the values of porosity and permeability are + TZ111 -3 2 mostly low, 0-9% and 0-2×10 μm respectively (Fig. 7), TZ112 10 10 TZ117 accounting for over 60% of the total number of samples, so Lithic quartz TZ122 the reservoir is poor. A relatively good linear relationship sandstone + TZ47 25 + 25 + * * between porosity and permeability also exists (Fig. 6). The * * + * + + TZ58 * + + + + + + + ** * Feldspar-lithic *** + * * + * st **+ * * *+ + + * * + + + + * * + + ** * * + + + + * * * TZ62 main pore types of the 1 upper submember are also primary * + + + + + * * quartz sandstone +* * * * + * * ** * * + + *+** * + + + * * ** *** * ** * * * * * * ** * ** * * *** * ** * ** * * * * * * ** * * * ** ** *** * * * ** * * ** TZ67 ** ** ** ** ** ** ** * * * * ** * ** * ** * * * intergranular pores and intergranular dissolved pores (Fig. 8). * ** ** 50 * 50 *** * ** TZ69 rd The 3 upper submember also consists mainly of lithic TZ77 * * ** sandstone and a small portion of lithic quartz sandstone. * * * ** st Compared with the 1 upper submember, it has a larger Lithic amount of feldspar-lithic quartz sandstone (Fig. 5(b)). rd sandstone Nevertheless, the sandstone maturity of the 3 upper submember is still relatively low and the quartz content is generally 25%-75%. The porosity and permeability are also poor and their values are basically the same as those of the 25 75 50 Feldspar Debris st 1 upper submember. They are also distributed mainly in rd (b) The 3 upper submember low-value areas, and there are relatively large differences rd among different regions. Overall, the 3 upper submember Fig. 5 Triangular diagram of the composition of the st is better than the 1 upper submember (Fig. 7). A relatively Silurian sandstone in the Tazhong area, Tarim Basin good linear relationship between porosity and permeability rd From the comparison of reservoir properties, it can be also exists (Fig. 6). The main type of porosity of the 3 concluded that the Carboniferous Donghe sandstone reservoir upper submember is primary intergranular, and intergranular is better than the Silurian reservoir. dissolved porosity is less (Fig. 8). Average surface porosity, % Frequency, % Frequency, % Pet.Sci.(2010)7:192-200 195 Break Break Break Break Break Break Slope Slope Slope Slope Slope Slope No.1 No.1 No.1 No.1 No.1 No.1 1. 0 The The The The The The 1 0 Zone Zone Zone Zone Zone Zone 8 8 1 12 2 1. 0 1.0 196 Pet.Sci.(2010)7:192-200 TZ49 TZ49 TZ45 TZ45 N N TZ63 TZ63 TZ85 TZ85 TZ47 TZ47 TZ66 TZ66 TZ21 TZ21 TZ40 TZ40 TZ68 TZ68 TZ67 TZ67 TZ10 TZ10 TZ54 TZ54 TZ20 TZ20 TZ13 TZ13 TZ11 TZ11 TZ82 TZ82 TZ14 TZ14 TZ12 TZ12 TZ83 TZ83 TZ50 TZ50 TZ46 TZ46 TZ37 TZ72 TZ37 TZ72 TZ84 TZ84 TZ17 TZ9 TZ17 TZ9 TZ2 TZ62 TZ2 TZ62 TZ15 TZ15 TZ403 TZ403 TZ4 TZ58 TZ4 TZ58 TZ408 TZ408 TZ22 TZ22 TZ16 TZ16 TZ79 TZ79 TZ401 TZ401 TZ43 TZ43 TZ24 TZ24 TZ6 TZ6 TZ103 TZ103 TZ26 TZ26 TZ7 TZ7 TZ53 TZ53 TZ104 TZ104 TZ 5 TZ5 TZ78 TZ78 TZ52 TZ52 TZ38 TZ38 TZ3 TZ3 TZ60 TZ60 Legend Legend TZ3 TZ3 Wedge-out Poros ity Well Wedge-out Permeability Well line is oline location line isoline location (a) Porosity (b) Permeability Fig. 9 Porosity (a) and permeability (b) distribution of the Carboniferous Donghe sandstone in the Tazhong area, Tarim Basin TZ452 TZ452 TZ49 TZ49 TZ451 TZ451 TZ45 TZ45 TZ63 TZ63 TZ85 TZ85 TZ47 TZ47 TZ35 TZ35 TZ66 TZ66 TZ21 TZ21 TZ67 TZ67 TZ10 TZ10 TZ54 TZ54 TZ20 TZ20 TZ112 TZ112 TZ201 TZ11 TZ13 TZ201 TZ13 TZ11 TZ111 TZ111 TZ18 TZ18 TZ82 TZ82 TZ14 TZ14 TZ122 TZ122 TZ12 TZ80 TZ12 TZ80 TZ46 TZ46 TZ50 TZ50 TZ37 TZ30 TZ37 TZ30 TZ19 TZ19 TZ44 TZ44 TZ15 TZ17 TZ15 TZ9 TZ17 TZ9 TZ61 TZ77 TZ61 TZ77 TZ58 TZ58 TZ69 TZ69 TZ22 TZ22 TZ4 TZ16 TZ4 TZ16 TZ401 TZ401 TZ43 TZ6 TZ43 TZ6 TZ103 TZ103 TZ261 TZ261 TZ101 TZ101 TZ52 TZ52 TZ60 Legend TZ60 Legend TZ3 TZ3 Wedge-out Permeability Well Wedge-out Porosity Well line isoline location line isoline location (a) Porosity (b) Permeability st Porosity (a) and permeability (b) distribution of the 1 upper submember of the Silurian Kepingtage Formation in the Tazhong area, Tarim Basin Fig. 10 TZ452 TZ452 TZ49 TZ49 TZ451 TZ451 TZ45 TZ45 N N TZ63 TZ63 TZ47 TZ47 TZ85 TZ85 TZ66 TZ66 TZ35 TZ35 TZ21 TZ21 TZ67 TZ67 TZ10 TZ10 TZ20 TZ20 TZ54 TZ54 TZ112 TZ112 TZ201 TZ201 TZ13 TZ11 TZ13 TZ11 TZ111 TZ18 TZ111 TZ18 TZ82 TZ82 TZ14 TZ14 TZ122 TZ122 TZ12 TZ12 TZ80 TZ30 TZ80 TZ30 TZ50 TZ50 TZ46 TZ46 TZ37 TZ37 TZ17 TZ19 TZ17 TZ19 TZ15 TZ15 TZ61 TZ61 TZ77 TZ77 TZ9 TZ9 TZ62 TZ62 TZ69 TZ69 TZ22 TZ22 TZ4 TZ16 TZ4 TZ16 TZ401 TZ401 TZ79 TZ79 TZ43 TZ43 TZ6 TZ6 TZ103 TZ103 TZ261 TZ261 TZ101 TZ101 TZ52 TZ52 TZ60 TZ60 Legend Legend TZ3 TZ3 Wedge-out Permeability Well Wedge-out Porosity Well line isoline location line isoline location (b) Permeability (a) Porosity rd Fig. 11 Porosity (a) and permeability (b) distribution of the 3 upper submember of the Silurian Kepingtage Formation in the Tazhong area, Tarim Basin 10 0 0 15 60 km 15 30 60 km 30 45 60 km 30 45 60 km 15 30 60 km 45 60 km 1 0 100 Pet.Sci.(2010)7:192-200 197 Calcite 4 The content of cement (especially 1% 5% 1% Ferrous calcite carbonate cement) is the main factor Dolomite 33% controlling the porosity and permeability of 23% Ankerite clastic reservoirs 12% 25% Silica The statistics of the interstitial material contents from Gypsum many wells in the east and west of the Tazhong area show Pyrite that the cement is the major interstitial material influencing the porosity and permeability of the Carboniferous Donghe Cement contents of the Carboniferous Donghe sandstone Fig. 13 reservoir in the Tazhong area, Tarim Basin sandstone reservoirs, especially the carbonate cement (Fig. 12). It can be seen from Fig. 12 that, the higher the interstitial material content, the lower the porosity, and vice versa. When an important reason why the former has better reservoir the cement content is less than 5%, the porosity is generally properties than the latter. The contents of interstitial material greater than 12%. When the cement content is greater than rd and cement of the 3 upper submember are less than those 5%, the porosity is generally less than 12%. The main type of st of the 1 upper submember, but the matrix contents of them cement is carbonate, accounting for 92% of the total content are similar (Fig. 17). So the differences between the two (Fig. 13), being mainly calcite, ferrous calcite, dolomite submembers are mainly caused by carbonate cement and and ankerite. Through the comparison between interstitial are not related with the matrix content. There is a negative material content and porosity and permeability values of correlation between the interstitial material content and the Donghe sandstone reservoirs from wells TZ40 and TZ75, it porosity and permeability. With the increase of interstitial was found that there was a good correlation, and the layer material content, the porosity and permeability of the with low interstitial material content especially low cement reservoir decreased in general. The negative correlation also content had high values of porosity and permeability (Fig. exists between the carbonate content and the porosity and 14). For example, the cement content of Donghe sandstone permeability, which indicates that the carbonate cementation reservoir below 3,716 m from well TZ75 decreased, while plays a leading role in the diagenetic cementation of the the porosity and permeability increased significantly. When Silurian reservoirs in the study area (Fig. 18). the cement content above 3,716 m increased, the reservoir Through the discussion above, we believe that the cement properties became poor. content (especially carbonate cement content) is the main factor controlling the porosity and permeability of clastic reservoirs in this area. The differences between the Silurian and Carboniferous clastic reservoirs are related with the compositional maturity. 5 The hydrocarbon distribution of Carboniferous and Silurian clastic reservoirs in the Tazhong area is closely related to the reservoir properties The reservoir is one of the most basic conditions to form hydrocarbon accumulations and the pores in the reservoir provide the space to store oil and gas. Therefore, the size and connectivity of the pores directly infl uence the accumulation and distribution of oil and gas (Wang, 2001; Cai, 2005; Yu et al, 2005; Wang et al, 2008; Liu et al, 1996). In order to search Matrix Cements Matrix Cements Matrix Cements Matrix Cements for the relationship between hydrocarbon distribution of Porosity > 12% Porosity < 12% Porosity > 12% Porosity < 12% Carboniferous and Silurian clastic reservoirs and the porosity and permeability, we plotted matching maps between the Western Eastern porosity and permeability and hydrocarbon distribution of the rd Fig. 12 Interstitial material contents of the Carboniferous Donghe 3 upper submember of the Silurian Kepingtage Formation sandstone reservoir in the Tazhong area, Tarim Basin and Carboniferous Donghe sandstone (Figs. 19 and 20). It can be found that the Carboniferous Donghe sandstone reservoirs Similar to the Carboniferous clastic reservoir, the main have been discovered in the area where the porosity of cement of the Silurian reservoir is also carbonate cement reservoir is high, which is more than 8%. For instance, most (Figs. 15 and 16). The contents of carbonate cement of the of the reservoirs in the TZ4-TZ1, TZ16 and TZ24 well blocks st rd 1 and 3 upper submembers are 95% and 89%, respectively, in the southeast and the TZ47, TZ40 and TZ10 well blocks in and the cements are mainly calcite, ferrous calcite, dolomite the northwest are located in the area with the porosity more rd and ankerite. The cement content of the 3 upper submember than 10% (Fig. 19), that is, the high-value areas of porosity st is less than that of the 1 upper submember, which is also control the hydrocarbon distribution. For clastic reservoirs, Interstitial material content, % 3720 3740 Donghe sandstone member 198 Pet.Sci.(2010)7:192-200 Content of Content of Content of Grain size Total surface Content of interstitial impurity max value carbonate DepthLithological Permeability porosity Horizon Quartz Feldspar Cuttings Porosity cement 0 0.6 material matrix cement m column min value 0 100 0 100 0 100 0 25 0. 001 1000 0 50 0 50 0 30 0 30 0 30 0 0.6 Relationship between interstitial material content and porosity and permeability of the Carboniferous Donghe Fig. 14 sandstone reservoir at well TZ75 in the Tazhong area, Tarim Basin Calcite 0% Ferrous calcite 3% 2% Dolomite 8% 4% Ankerite 4% Silica 79% Gypsum Pyrite st Fig. 15 Cement content of the Silurian 1 upper submember reservoir in the Tazhong area, Tarim Basin Calcite 3% 4% 4% Ferrous calcite Dolomite 25% 56% Ankerite Interstitial Interstitial Impurity Impurity Cement Cement Silica material material matrix matrix Gypsum 3% 5% rd st 3 upper subm em ber 1 upper subm em ber Pyrite rd Fig. 17 Interstitial material content of the Silurian reservoir in Cement content of the Silurian 3 upper submember reservoir in Fig. 16 the Tazhong area, Tarim Basin the Tazhong area, Tarim Basin rd such a correlation between hydrocarbon distribution and and they are mainly in the 3 upper submember (Fig. permeability also exists in these areas. 20). Similar to the distribution of Carboniferous Donghe At present, there are four Silurian reservoirs including sandstone reservoirs, the Silurian reservoirs are all located in rd TZ47, TZ11, TZ12-TZ50 and TZ16 in the Tazhong area, the high-value areas of porosity of the 3 upper submember Interstitial material content, % Break Break Slope Slope No.1 No. 1 Zone The The 1 . 0 Zone 1 0 1 0 0 1 0 1 0 1 0 1 0 Pet.Sci.(2010)7:192-200 199 100 100 10 10 15 15 1 1 0.1 0.1 5 5 0.01 0.01 5 10 15 0 5 10 15 02 4 68 10 12 0 5 10 15 Content of Content of Content of Content of interstitial material, % interstitial material, % carbonate cement, % carbonate cement, % Fig. 18 Relationship between reservoir properties and interstitial material or carbonate cement content of rd the Silurian 3 upper submember at well TZ111 in the Tazhong area, Tarim Basin with the porosity greater than 8% (Fig. 20). Because of the TZ49 TZ45 relationship between reservoir distribution and high-value TZ63 TZ85 areas of porosity, it can be considered that the distribution TZ47 47 TZ66 TZ21 TZ40 Z40 of clastic reservoirs in the study area is closely related to the TZ68 TZ67 TZ10 TZ10 properties of reservoirs. TZ54 T TZ20 TZ13 TZ11 TZ82 TZ14 TZ12 TZ83 TZ50 6 Prediction of favorable hydrocarbon TZ46 TZ72 TZ37 TZ84 TZ17 TZ9 TZ2 TZ62 TZ15 TZ15 TZ403 exploration targets of Paleozoic clastic TZ4 Z4 TZ58 T TZ5 TZ408 TZ408 TZ22 TZ1 TZ16 TZ79 TZ79 TZ4 TZ401 reservoirs in the Tazhong area TZ43 TZ TZ24 TZ6 6 TZ103 TZ1 TZ26 TZ7 TZ104 TZ104 TZ53 The high-value areas of the properties of Carboniferous TZ5 TZ78 TZ52 and Silurian clastic reservoirs are located in the southeast of TZ38 TZ3 TZ60 the Tazhong area. The main factor controlling the properties Legend TZ3 of clastic reservoirs is the cement content (especially the Wedge-out Porosity Well Oil reservoir Condensate line isoline location gas reservoir carbonate cement content). The hydrocarbon distribution of the Carboniferous and Silurian is closely related to the Matching map between porosity and distribution of the Carboniferous Fig. 19 reservoir properties and is generally in the high-value areas Donghe sandstone reservoirs in the Tazhong area, Tarim Basin of porosity and permeability. In other words, the basis for predicting favorable hydrocarbon exploration areas is the TZ452 TZ49 TZ451 porosity and permeability of reservoirs. Therefore, the TZ45 TZ63 hydrocarbon exploration of the two sets of strata should be TZ47 TZ85 TZ66 focused on the southeast of the Tazhong area, especially TZ35 TZ21 on the updip pinch-out area. However, due to the local TZ67 TZ10 TZ20 TZ54 TZ112 sedimentation or the post-depositional reconstruction, the TZ201 TZ13 TZ11TZ111 TZ18 TZ82 TZ14 TZ122 clastic reservoirs of the two sets of strata can also form high- TZ12 TZ80 TZ30 TZ50 TZ46 value areas of porosity and permeability in the middle of the TZ37 TZ17 TZ19 TZ15 TZ61 TZ77 TZ9 Tazhong area, which should also be considered as favorable TZ62 TZ69 TZ22 TZ4 TZ16 TZ401 exploration areas, such as the Donghe sandstone reservoir in TZ79 TZ43 TZ6 TZ103 TZ261 the TZ66-TZ54 well block near the No.1 slope break zone TZ101 in the northern part of the middle Tazhong area (the porosity TZ52 values are higher than 10%) and the TZ46-TZ37 well block Legend TZ60 in the southern part (the porosity values are higher than 12%). rd TZ3 For the 3 upper submember of the Silurian Kepingtage Wedge-out Porosity Well Oil reservoir line isoline location Formation, the TZ67-TZ54 well block near the No.1 slope break zone in the northern part of the middle Tazhong area, rd Fig. 20 Matching map between porosity and distribution of the 3 upper the TZ17-TZ37 well block in the southern part, and the submember reservoir of the Silurian Kepingtage Formation in the Tazhong TZ83-TZ44 well block in the southeastern part, with porosity area, Tarim Basin 10 0 1 0 0 1 0 0 Porosity, % -3 2 Permeability, ×10 μm Porosity, % -3 2 Permeability, ×10 μm 200 200 Pet.Sci.(2010)7:192-200 Petroleum University. 2001. 23(4): 1-5 (in Chinese) values more than 10%, should be regarded as favorable areas. Gu J Y. Sedimentary environment and reservoir characters of the In fact, the TZ66-TZ54 well block of the Carboniferous and Carboniferous Donghe sandstone in the Tarim Basin. Acta Geologica the TZ67-TZ54 well block of the Silurian are overlapped Sinica. 1996. 70(2): 153-161 (in Chinese) with each other, so are the TZ46-TZ37 and TZ17-TZ37 well Gu J Y, Zhang X Y and Guo B C. Characteristics of sedimentation and blocks. Therefore, we should strengthen the exploration in reservoir of the Donghe sandstone in Tarim Basin and their synthetic the two areas, expecting to find Carboniferous and Silurian analysis. Journal of Palaeogeography. 2006. 8(3): 285-294 (in reservoirs. However, the above prediction is based on the Chinese) reservoir characteristics. In order to obtain more objective Jia J H, Zhang B M, Zhu S H, et al. Stratigraphy, sedimentary understanding, research on hydrocarbon accumulation and characteristics and lithofacies palaeogeography of the Silurian in preservation conditions should also be carried out. Tarim Basin. Journal of Palaeogeography. 2006. 8(3): 339-351 (in Chinese) 7 Conclusions Li Y P, Li X S, Zhou Y, et al. Sedimentary characteristics and evolution history of middle-upper Ordovician in Tazhong area. Xinjiang 1) The Donghe sandstone mainly consists of lithic quartz Petroleum Geology. 2000. 21(3): 133-137 (in Chinese) sandstone, and the compositional maturity is high. Generally, Liu J D, Zhang S N, Tian J C, et al. Discussion on exploration direction -3 2 the porosity is 3%-20% and the permeability is 0.1×10 μm - and depositional system of Silurian-Devonian in Tarim Basin, -3 2 China. Journal of Chengdu University of Technology (Science & 500×10 μm , and there is a relatively good linear relationship Technology Edition). 2004. 31(6): 654-657 (in Chinese) between porosity and permeability. The main pore types Liu L F, Li Y, Wang P, et al. Reservoir types and favorable oil-gas are residual primary intergranular pores and intergranular st rd exploration zone prediction of the upper Ordovician Lianglitage dissolved pores. The 1 and 3 upper submembers consist Formation in Tazhong No.1 fault belt of Tarim Basin. Journal of mainly of lithic sandstone. The porosity and permeability Palaeogeography. 2008. 10(3): 221-230 (in Chinese) -3 2 values are mostly in the range of 0-9% and 0-2×10 μm , Liu S G, Zhai Y H and Guo J H. Pore texture and evaluation of respectively, and a relatively good linear relationship between Carboniferous clastic reservoirs in Tazhong area. Journal of Oil and porosity and permeability also exists. The cement content Gas Technology. 1995. 17(3): 8-12 (in Chinese) is the main factor controlling the reservoir properties. The Liu S P, Zhong G F, Liu X F, et al. Characteristics and evaluation of higher the interstitial material content, the lower the porosity, Silurian sandstone reservoir in Tazhong area, Tarim Basin. Journal of and vice versa. The Carboniferous Donghe sandstone Oil and Gas Technology. 1996. 18(4): 21-25 (in Chinese) She n A J, Wang Z M, Yang H J, et al. Genesis classification and reservoirs are better than the Silurian reservoirs on the whole. characteristics of Ordovician carbonate reservoirs and petroleum 2) The high-value areas of porosity and permeability of exploration potential in Tazhong region, Tarim Basin. Marine Origin clastic reservoirs are located in the southeast of the Tazhong Petroleum Geology. 2006. 11(4): 1-12 (in Chinese) area. This distribution characteristic is closely related to the Sun L D, Zhou X Y and Wang G L. Contributions of petroleum geology shallow water deposits in the southeastern part, relatively and main directions of oil-gas exploration in the Tarim Basin. high structural position and shallow burial depth. Because Chinese Journal of Geology (Scientia Geologica Sinica). 2005. the reservoir properties control hydrocarbon distribution, 40(2): 167-178 (in Chinese) exploration of the Carboniferous and Silurian clastic rocks in Wan g G C. Characteristics of clastic reservoirs in the Tarim Basin. the Tazhong area should be directed at the southeastern part. Petroleum Geology & Experiment. 2001. 23(1): 62-66 (in Chinese) 3) The discovered Paleozoic reservoirs in the Tazhong Wan g P, Liu L F, Li Y, et al. Reservoir characteristics of the 3rd upper area have a good matching relationship with the high-value sub-member of the Silurian Kepingtage Formation in Tazhong area and their relations to oil and gas distribution. Oil & Gas Geology. areas of porosity, and are located in the area with the porosity 2008. 29(2): 174-180 (in Chinese) more than 8%. The basis for predicting favorable hydrocarbon Wan g S M and Lü X X. Features and petroleum significance of exploration areas is the porosity and permeability of Ordovician carbonate reservoir in Tazhong area, Tarim Basin. reservoirs. Therefore, the hydrocarbon exploration of the Journal of Xi’an Shiyou University (Natural Science Edition). 2004. two sets of strata should be focused on the southeast of the 19(4): 72-76 (in Chinese) Tazhong area, especially on the updip pinch-out area. Wu C J, Dai Z Y and Liu S H. Study on the physical factors of Carboniferous Donghe sandstone reservoir in Tazhong area. Acknowledgements Contributions to Geology and Mineral Resources Research. 2006. 21(3): 199-202 (in Chinese) This work is supported by the Basic Research Program of Yu R L, Yan X B, Jin X H, et al. Research achievements and exploration China (973 Program, Grant No. 2006CB202308). direction in Tarim Basin. Oil & Gas Geology. 2005. 26(5): 598-604 (in Chinese) References Zho ng D K, Zhu X M, Zhou X Y, et al. Effect of structure on sandstone’s Cai X Y. Reservoiring conditions and exploration targets in Tarim Basin. porosity evolution: a case study from the Donghe sandstones in Oil & Gas Geology. 2005. 26(5): 590-597 (in Chinese) central Tarim. Chinese Journal of Geology (Scientia Geologica Che n J S, Wang Z Y, Dai Z Y, et al. Study of the middle and upper Sinica). 2004. 39(2): 214-222 (in Chinese) Ordovician rimmed carbonate platform system in the Tazhong area, Zhu X M, Zhang Q, Zhao C L, et al. Sedimentary facies and Tarim Basin. Journal of Palaeogeography. 1999. 1(2): 8-17 (in environmental changes of the Donghe sandstone in central Tarim. Chinese) Chinese Journal of Geology (Scientia Geologica Sinica). 2004. Dai Z Y, Zhou Y, Chen J S, et al. 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Published: Jun 3, 2010

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