292 Pet.Sci.(2013)10:292-302 DOI 10.1007/s12182-013-0278-1
Characteristics of the turbidite fan in the Wenchang Formation of the Enping Sag, Pearl River Mouth %DVLQ&KLQDDQGLWVK\GURFDUERQVLJQL¿FDQFH
Chen Guojun1, Li Chao1, 2 , Du Guichao2, Zhang Gongcheng3, Lü Chengfu1 and Wang Qi1 1 Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, /DQ]KRX*DQVX&KLQD 2 University of Chinese Academy of Sciences, Beijing 100049, China 3 Research Institute of China National Offshore Oil Corporation, Beijing 100027, China
© China University of Petroleum (Beijing) and Springer-Verlag Berlin Heidelberg 2013
Abstract: A turbidite fan in the Eocene upper Wenchang Formation in the Enping Sag, Pearl River 0RXWK%DVLQ 350% KDVEHHQVWXGLHGXVLQJVHLVPLFORJJLQJDQGERUHKROHGDWD7KHIDQLVFKDUDFWHUL]HG E\SDUDOOHOSURJUDGDWLRQRQWKHGLSVHLVPLFSUR¿OHDQGLVPRXQGVKDSHGRUOHQWLFXODUVKDSHGRQWKHVWULNH VHLVPLFSUR¿OH7KHVWXG\RIWKHFRUHDQGORJJLQJGDWDIURPZHOO(3ZKLFKLVORFDWHGLQWKHIURQW VLGHRIWKHWXUELGLWHIDQVKRZVWKDWWKLVIDQLVDVHWRIQRUPDOJUDGLQJVDQGEHGVLQWHUEHGGHGZLWKLQ WKLFNGDUNJUH\PXGVWRQHVRIVHPLGHHSWRGHHSODNHGHSRVLWVLQWKH:HQFKDQJ)RUPDWLRQ7KHIDQLV interpreted as a sand/mud-rich turbidite fan that has an area of over 140 km2 and a maximum thickness RIRYHUP&RPELQHGZLWKDVWXG\RIWKHUHJLRQDOJHRORJLFDOEDFNJURXQGDQGSUHYLRXVSURYHQDQFH analysis of the Eocene Wenchang Formation, the main potential provenances for the turbidite fan are FRQVLGHUHGWREHWKH3DQ\XORZXSOLIWDQGQRUWKHUQIDXOWWHUUDFH]RQH7KH(QSLQJ6DJLVFRQVLGHUHGWR EHDKDOIJUDEHQOLNHEDVLQZKRVHQRUWKVLGHLVIDXOWHGDQGZKRVHVRXWKVLGHLVRYHUODSSHG%DVHPHQW VXEVLGHQFHLQWKH(RFHQHZDVPDLQO\FRQWUROOHGE\ERXQGDU\IDXOWVZKLFKGLSUHODWLYHO\VWHHSO\RQWKH north side, causing the subsidence center of the Enping Sag in this stage to be close to the north boundary faults. Sustained faults developed in the Enping Sag during the Eocene caused an increase of the relative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enchang Formation has provided important information for sedimentary evolution in deep layers of the (QSLQJ6DJDQGSRLQWHGWRDQHZGLUHFWLRQIRUWKHK\GURFDUERQH[SORUDWLRQLQWKHVWXG\DUHD
Key words: Pearl River Mouth Basin, Enping Sag, Wenchang Formation, turbidite fan, hydrocarbon exploration
1 Introduction of the main focuses in global hydrocarbon exploration, but also a frontier in sedimentological studies in recent years (Zhu +\GURFDUERQH[SORUDWLRQLQGHHSZDWHUEDVLQVKDV et al, 2004; Chen et al, 2007; Wang et al, 2011). An estimated become an important and active field for the global oil and WRRLODQGJDV¿HOGVLQFOXGLQJSURGXFLQJ¿HOGV JDVLQGXVWU\VLQFHWXUELGLWHVDQGERGLHVZHUHIRXQGWREH DUHNQRZQIURPGHHSZDWHUWXUELGLWHVDQGUHODWHGV\VWHPV important oil and gas reservoirs in the 1950s (Wu, 1986; Pang 6WRZDQG0D\DOO 3HWWLQJLOO GRFXPHQWHG HWDO 'HHSZDWHUWXUELGLWHIDQVDUHQRWRQO\RQH 925 of these fields (excluding carbonate plays) from 54 EDVLQVRIZKLFK¿HOGVFRXOGEHFODVVL¿HGDVJLDQWV ! *Corresponding author. email: OLFKDRPDLOV#FRP PLOOLRQEDUUHOVRLOHTXLYDOHQW 7XUELGLWHUHVHUYRLUVDUHDOVR Received May 11, 2012 ZLGHO\GLVFXVVHGLQ&KLQD /DLDQG*X *DRDQG:X Pet.Sci.(2013)10:292-302 293
1985; Lei et al, 1999; Bai and Zhang, 2004; Liu et al, 2006). 7KH(QSLQJ6DJLVORFDWHGLQWKHZHVWRIWKH=KX, 'HHSZDWHUK\GURFDUERQH[SORUDWLRQIRUVXEPDULQHIDQVKDV 'HSUHVVLRQZKLFKLVVLWXDWHGRQWKHQRUWKHUQPDUJLQRIWKH achieved great success in the Pearl River Mouth Basin in the 3HDUO5LYHU0RXWK%DVLQ )LJ 7KLVVDJLVDKDOIJUDEHQ northern slope of the South China Sea in recent years, and a OLNHEDVLQZLWKDQDUHDRIDERXWNP2 (2,200 km2 for ODUJHVXEPDULQHIDQZDVGLVFRYHUHGLQWKH%DL\XQ6DJ7KH the Paleogene) and a depositional thickness of over 8,000 GHHSZDWHUIDQKDVEHHQSURYHGWREHSUROL¿FE\ZHOOVGULOOHG m (Huang, 1999; Fu et al, 2007; Chen et al, 2008). Affected on the LW3-1 structural trap (Pang et al, 2006; 2007; Wang by multiple tectonic movements, the geological evolution et al, 2011; 2012; Zhu et al, 2012). So, are there turbidite of the basin can be divided into four tectonic stages: 1) pre- fans developed in the Enping Sag? It is necessary to study ULIWLQJVWDJH ULIWLQJVWDJHEHWZHHQWKHODWH&UHWDFHRXV WKHNQRZQWXUELGLWHIDQDQGLWVIRUPDWLRQWLPHGLVWULEXWLQJ and the early Oligocene, 3) depression stage during the late features, the characteristics of associated sands developed Oligocene to the early Miocene, 4) block faulting stage from in this fan and the main controlling factors for its formation. the late Miocene to the present (Huang, 1999; Li, 1999; Zhuo ,WLVLPSRUWDQWWRILQGWKHDQVZHUVZKLFKZLOOVLJQLILFDQWO\ HWDO =KDQJ 7KH:HQFKDQJ)RUPDWLRQ contribute to understanding the sedimentary evolution and the deposited in the Eocene, is typical in the main rifting stage. directions for hydrocarbon exploration in the Enping Sag. 7KH3HDUO5LYHU0RXWK%DVLQKDVH[SHULHQFHGVHYHUDO 7KHWXUELGLWHIDQLQWKHXSSHUVWUDWDRIWKH(RFHQH phases of tectonic movements. Affected by the Shenhu Wenchang Formation has been studied on the basis of PRYHPHQWWKH1((:PDLQIDXOWVZHUHJHQHUDWHGDQG previous research on the regional tectonics and sedimentary DFWLYDWHGDQGWKH(QSLQJ6DJZDVLQLWLDOO\IRUPHGGXULQJ
EDFNJURXQGWKURXJKVHLVPLFGDWDLQWHUSUHWDWLRQZHOO the late Cretaceous (K3 WR3DOHRFHQH7KHPDLQIDXOWV VHLVPLFFDOLEUDWLRQZHOOGDWDFRPELQHGZLWKVHLVPLF ZHUHIXUWKHUDFWLYDWHGDVWKHILUVWHSLVRGHRIWKH=KXTLRQJ 1-2 UHÀHFWLRQFKDUDFWHULVWLFVVHLVPLFIDFLHVDQGGULOOLQJFXWWLQJV movement occurred during the early to middle Eocene (E2 ), DQDO\VLV7KHWHFWRQLFEDFNJURXQGSURYHQDQFHVHGLPHQWDU\ and the amplitude of the faults increased rapidly in this environment and the main factors controlling the formation of SHULRG&RUUHVSRQGLQJO\WKHZDWHUGHSWKLQWKH(QSLQJ6DJ WXUELGLWHIDQDQGLWVGHSRVLWLRQDOPRGHOZHUHVWXGLHG)LQDOO\ increased and fluvial-lacustrine facies of the Wenchang ZHLQWHJUDWHGVHLVPLFUHÀHFWLRQDWWULEXWHVVXFKDVIUHTXHQF\ )RUPDWLRQZDVGHSRVLWHGLQWKHEDVLQFHQWHU7KH(QSLQJ and amplitude, AVO analysis and formation pressure testing 6DJZDVXSOLIWHGDQGGHQXGHGDVWKHVHFRQGHSLVRGHRIWKH WRDQDO\]HWKHK\GURFDUERQSRWHQWLDORIWKHWXUELGLWHIDQDQG Zhuqiong movement occurred during the late Eocene to early 3 1 pointed out the directions for hydrocarbon exploration in the Oligocene (E2 -E3 ZLWKWKHVDJFRQWLQXRXVO\H[WHQGLQJDQG study and adjacent area. faults further developed in this period. Correspondingly, the ODNHDUHDRIWKH(QSLQJ6DJZDVELJJHUDQGLWVZDWHUGHSWK 2 Geological setting ZDVPXFKVKDOORZHUWKDQWKDWRIWKH:HQFKDQJ)RUPDWLRQ DQGDWWKLVWLPHWKHVDJGHSRVLWHGWKHÀXYLDOODFXVWULQHIDFLHV 2.1 Structural geology and tectonics of the Enping Formation. After that, the Enping Sag entered
112° 114° 116° 118°
North Fault Belt PY1-1
20° 20 50' 50 Zone Enping Sag 22° EP12-1
Fault B Zhu I Depression EP11-1 C A EP14-5
Chaoshan EP18-3 Northern Enping Uplift Belt Sag Depression A 20° 20° B 20° EP17-3-1 EP18-1 20 30' 30 Central C Zhu III Depression Panyu Low-uplift Zhu II DepressionSouth Uplift Belt EP23-1 0 60 120km 0 20 40km
18° 18° 112° 114° 116° 118° 113° 50' 113° 80'
Basin First-order Second-order Basin location boundary structural boundary structural boundary
A Turbidite Study area Line of cross section EP Well locations A sandbody
Fig. 1/HIW 7HFWRQLFGLYLVLRQRIWKH3HDUO5LYHU0RXWK%DVLQDQGORFDWLRQRIWKHVWXG\DUHD 5LJKW 7KHGLVWULEXWLRQRIWKHWXUELGLWHIDQLQWKH:HQFKDQJ)RUPDWLRQRIWKH(QSLQJ6DJ 294 Pet.Sci.(2013)10:292-302 the post-rifting stage roughly from the late Oligocene to the PLQZHOO(3UHYHDOHGPEODFNPXGVWRQHV )LJ SUHVHQW6HDZDWHUHQWHUHGWKH(QSLQJ6DJGXULQJWKHODWH 7KHXSSHUDQGORZHUZDVWKHORZIUHTXHQF\FRQWLQXRXV Oligocene Zhuhai sedimentary stage and progradation of KLJKDPSOLWXGHVHLVPLFIDFLHVDQGWKHPLGGOHZDVEODQN paleo-Pearl River Delta reached the study area, depositing ZLWKZHDNUHIOHFWLRQ7KHORZIUHTXHQF\FRQWLQXRXVKLJK the transitional and deltaic facies of the Zhuhai Formation in DPSOLWXGHGHSRVLWVLQWKH:HQFKDQJ¶VXSSHUDQGORZHU WKHOLWWRUDOEDFNJURXQG7KHRSHQVHDEDVLQZDVIRUPHGLQ VHJPHQWVDUHFRQVLGHUHGDVPXGVWRQHVLQWHUEHGGHGZLWKWKLQ WKHPLGGOH0LRFHQHDQGWKLFNPXGVWRQHZDVWKHGRPLQDQW VDQGVWRQHVZKLOHWKHPLGGOHLVSXUHVDQGVWRQH /L VHGLPHQWZKLFKLVJRRGFDSIRUPDWLRQ 0LDRHWDO 0LDRHWDO VXJJHVWHGWKDWWKHZHOO+KDGWKHVDPH In summary, the Enping Sag experienced rifting and characteristics as the Wenchang Formation sequence (Fig. 4). SRVWULIWLQJVWDJHVZKLFKDUHVHSDUDWHGE\DQXQFRQIRUPLW\ LQWHUIDFH 7 IRUPHGE\WKH1DQKDLPRYHPHQWLQWKH 2.3 Sedimentary facies of the Wenchang Formation ODWH2OLJRFHQH7KHGHSRVLWLRQDOHQYLURQPHQWRIWKHVDJ Miao et al (2010) pointed out that the top and bottom evolved from terrestrial facies to marine facies. In the rifting interfaces of the Wenchang Formation at the edge of the stage continental facies are deposited in the Wenchang and depression are unconformity surfaces, but the surfaces are Enping formations. During the post-rifting stage, the Zhuhai FRQIRUPDEOHLQWKHFHQWUDOGHSUHVVLRQ7KUHHIDFLHVRIWKH )RUPDWLRQZDVLQDWHUUHVWULDOPDULQHHQYLURQPHQWZKLOHWKH :HQFKDQJ)RUPDWLRQDUHUHFRJQL]HG7KHERWWRPIDFLHV Zhujiang, Hanjiang and Wanshan formations deposited in is alluvial fan – fan delta, the center is transitional littoral marine facies. DQGVKDOORZODNH±VHPLGHHSODNHDQGWKHWRSLVIDQGHOWD ±OLWWRUDODQGVKDOORZODNH$IIHFWHGE\SURYHQDQFHZDWHU 2.2 Stratigraphy of the Wenchang Formation and later erosion, different sags have different depositional 7KH(RFHQH(QSLQJ6DJLVDVWURQJO\VHSDUDWHGULIWLQJ HQYLURQPHQWV7KHVHPLGHHSODNHVHLVPLFIDFLHVDUH EDVLQZKLFKFRUUHVSRQGVLQSDUWWRWKHVHFRQGWHFWRQLFVWDJH FKDUDFWHUL]HGE\ORZIUHTXHQF\FRQWLQXRXVDQGKLJK of basin evolution (Wenchang Formation, typically deposited amplitude, and the lithology primarily consists of mudstone, LQWKHPDLQULIWLQJVWDJH 7KLVVDJH[SHULHQFHGVWURQJULIWLQJ LQWHUEHGGHGZLWKWKLQOD\HUVRIPXGG\VDQGVWRQHDQG and subsiding processes affected by the first episode of the VLOWVWRQH7KHORJJLQJFXUYHVVKRZKLJKDFRXVWLFYDOXHVDQG 1-2 Zhuqiong movement during early to middle Eocene (E2 ). KLJKJDPPDYDOXHVZLWK¿QJHUOLNHIHDWXUHV7KH:HQFKDQJ 7KH(RFHQH:HQFKDQJ)RUPDWLRQXQFRQIRUPDEO\FRQWDFWV Formation of the Enping Sag mainly develops semi-deep lake the underlying Shenhu Formation and records lacustrine DQGVKRUHíVKDOORZODFXVWULQHVRXUFHURFNV )XHWDO facies during the deepening of the lake in the basin center. 7KH:HQFKDQJ)RUPDWLRQLQVHLVPLFSURILOHV )LJ Semi-deep to deep lake deposits typically developed in the from the EP17 sub-sag presented sub-parallel, moderate- center of the Enping Sag, are mainly grayish black mudstones FRQWLQXRXVORZIUHTXHQF\DQGPRGHUDWHKLJKDPSOLWXGH LQWHUEHGGHGZLWK¿QHVDQGVWRQHVDQGLQWHUFDODWHGZLWKFRDOV reflection characteristics, indicating that the semi-deep 7KHPD[LPXPWKLFNQHVVRIWKH:HQFKDQJ)RUPDWLRQWKH ODNHIDFLHVPD\EHGHYHORSHG7KH(3VXEVDJSUHVHQWHG main source rocks of the sag, is generally about 3,000 m (Fig. FRQWLQXRXVORZIUHTXHQF\DQGPRGHUDWHKLJKDPSOLWXGH 2). reflection characteristics (Fig. 6), also indicating semi- 7KH:HQFKDQJ)RUPDWLRQVHGLPHQWVDUHFKDUDFWHUL]HG deep lake facies. Based on borehole, logging and seismic by coarse-fine-coarse grains in the vertical direction, for GDWDDQDO\VLVGHOWDLFDQGODFXVWULQHIDFLHVZHUHLGHQWL¿HGLQ example, drilling the Wenchang Formation at 4,570-4,864 the Wenchang Formation of the Enping Sag. Deltaic facies
Seismic reflection Strata Tectonic Main layer Lithology Source evolution Reservoir Seal tectonic profile rock stage event Period SeriesFormation Interface Age, Ma
Zhuhai Post- basin rifting 30 Nanhai T7 movement 32
Oligocene Enping The second
Lower Upper episode of T8 36 Zhuqiong 39 movement
Eocene Wenchang Early Tertiary The first Rifting basin episode of T9 54 Zhuqiong Palaeocene Shenhu movement Tg 65 Shenhu Pre-Tertiary movement
Fig. 2(DUO\7HUWLDU\VWUDWLJUDSKLFVHFWLRQRIWKH(QSLQJ6DJRIWKH3HDUO5LYHU0RXWK%DVLQ Pet.Sci.(2013)10:292-302 295
CAL, inch Sedimentary SP, mv CAL, inch 0 15 facies -400 -350 Depth Core profile 015Sub- Member Depth GR, API Core profile Lithology facies Sub- GR, API m '7ȝVP m DT, μs/m Facies 50 250 50 100 facies 50 250 50 100 4630 Brown mudstones deep
4600 and brown – sandy lake facies mudstones facies Semi-deep lake
Siltstones, Turbidite 4650 muddy deep lake facies siltstones 4640 Semi-deep lake facies– interbedded with fine-coarse 4700 sandstones Turbidite
Wenchang Formation Wenchang 4750 Dark grey mudstones, 4650 sandy mudstones with Lacustrine faices siltstones 4800 Semi-deep lake facies–deep facies deep lake facies 4850 4660 Semi-deep lake facies–
Fig. 3/LWKRORJLFFROXPQORJUHVSRQVHDQGOLWKRORJ\GHVFULSWLRQVRIWKH:HQFKDQJ)RUPDWLRQIURPZHOO(3RIWKH(QSLQJ 6DJ3HDUO5LYHU0RXWK%DVLQ5LJKW WKHVHFWLRQLOOXVWUDWLQJWKHW\SLFDOIDFLHVDQGYHUWLFDOUHODWLRQVKLSVEHWZHHQWKHWXUELGLWHIDQ and semi-deep and deep lake facies in the Wenchang Formation mainly developed on the north and south sides of the Enping PXGVWRQHVDQGLVGLVWULEXWHGDSSUR[LPDWHO\EHWZHHQZHOO Sag and lacustrine facies typically developed in the center of (3DQGZHOO(3IURP1:WR6(,WLVVOLJKWO\ the sag (Fig. 7). Basin modeling analysis indicates that the LUUHJXODUO\IDQVKDSHGRIZKLFKWKHDUHDLVDERXWNP2 area of the Wenchang Formation is about 1,500 km2LQZKLFK and the maximum thickness is approximately 340 m (Fig. 1). the semi-deep and deep lake facies accounts for 415 km2 (Li, 1999; Fu et al, 2007). Affected by the first episode of the Zhuqiong movement, the faulted lake basin further subsided GR, API Depth AC, ȝVP Short- Medium Long- Strata 0 250 m Lithology 100 60 cycle cycle cycle )DFLHV and the lake expanded, and in the basin center the semi-deep 3700
DQGGHHSODNHIDFLHVGHSRVLWHG )LJ 7KHVHPLGHHSDQG Shore- VKDOORZ lake deep lake facies is mainly a set of relatively thick dark grey, JUH\LVKEODFNPXGVWRQHVLQWHUEHGGHGZLWKVDQGVWRQHVDQG ILQHVDQGVWRQHV7KHGULOOLQJRIWKHZHOO(3UHDFKHG WKH:HQFKDQJ)RUPDWLRQDQGUHYHDOHG PVWUDWDRIZKLFK 3750 WKHWKLFNQHVVRIGDUNPXGVWRQHVLVP,QDGGLWLRQZHOO EP17-3-1 penetrated the front side of the turbidite fan (Fig. 6HPLGHHSODNHIDFLHV /RJJLQJGDWDIURPZHOO(3VKRZWKDWGHSRVLWVLQ
WKH:HQFKDQJ)RUPDWLRQDUHFKDUDFWHUL]HGE\KLJKJDPPD 3800 DQGDFRXVWLFYDOXHV7KHJDPPDFXUYHLVVWUDLJKWDQGLVFORVH WRWKHVKDOHOLQHZLWK¿QJHUOLNHIHDWXUHVLQGLFDWLQJWKDWWKH ODNHIDFLHV
Wenchang Formation belongs to semi-deep to deep lake 6KRUHVKDOORZ Wenchang Formation Wenchang deposits (Fig. 3). 3850 3 Occurrence of the turbidite fan
3.1 Seismic facies characteristics
2QVHLVPLFSURILOHVWKHWXUELGLWHVDQGERG\LVZHGJH 3900 'HOWDIDFLHV VKDSHGRQWKHGLSSUR¿OHDQGKXPPRFN\RUOHQWLFXODUVKDSHG RQWKHVWULNHSUR¿OH7KHVHLVPLFIDFLHVVKRZKLJKDPSOLWXGH PRGHUDWHIUHTXHQF\DQGJRRGFRQWLQXLW\7\SLFDOO\WKH VDQGERG\LVFKDUDFWHUL]HGE\OD\HUHGGHSRVLWLRQDQGREOLTXH 6DQGVWRQH 0XGVWRQH Volcanic rock 3RVLWLYHF\FOH ,QYHUVHF\FOH SURJUDGDWLRQDOUHÀHFWLRQFRQ¿JXUDWLRQDORQJWKHGLSGLUHFWLRQ Fig. 4 7KHVHTXHQFHDQGVHGLPHQWDU\IDFLHVDQDO\VLVRIZHOO+ )LJ 7KLVXQLWLVLQWHUEHGGHGZLWKLQDVHWRIGDUNJUH\ in the Wenchang Formation (Miao et al, 2010) 296 Pet.Sci.(2013)10:292-302
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Fig. 66HLVPLFUHÀHFWLRQFKDUDFWHULVWLFVRIWKH:HQFKDQJ)RUPDWLRQLQWKH(3VXEVDJ
3.2 Lithological characteristics morphology and microfacies of turbidite fans and their oil and gas exploration since 1950s (Wu, 1986; Redin, 1991; Reading 7KHZHOO(3SHQHWUDWHGWKHIURQWVLGHRIWKH and Richards, 1994), especially in submarine fans, and a WXUELGLWHIDQDQGUHYHDOHG PVDQGVWRQHVZKLFKZHUH ZLGHYDULHW\RIGHYHORSPHQWPRGHOVRIDQFLHQWDQGPRGHUQ LQWHUEHGGHGZLWKLQWKLFNPXGVWRQHV'HEULVVDPSOHVDQGWKLQ submarine fans have been proposed (Shanmugam, 2000; VHFWLRQVDQDO\VHVVKRZWKDWVDQGVWRQHVRIWKLVIDQDUHPLGGOH 7KHWXUELGLWHVQRWRQO\H[LVWLQWKHIRUPRIVXEPDULQH WRFRDUVHJUDLQHGSRRUO\VRUWHGSRRUO\URXQGHGDQGLQ¿OOHG fans, but also in valleys and channel fill, slumping, lobes, by argillic matrix in intergranular pores. Carbonate cements VKHHWOLNHVDQGVFRDWHGVDQGVZHGJHDQGFRQWLQHQWDOVORSH are present in debris samples and inclusions are rarely seen accumulation complexes (Wu, 1986; Walker, 1992; Viana LQTXDUW]JUDLQV'LDJHQHWLFREVHUYDWLRQVKRZVWKDWTXDUW] HWDO $OWKRXJKWKHRULJLQDOFRQFHSWRIWXUELGLWHVZDV RYHUJURZWKVDQGFOD\FRDWLQJVRFFXUZLGHO\)HOGVSDUV established from lakes, the level of research into lacustrine ZHUHVOLJKWO\VHULFLWL]HG )LJ 7KHWXUELGLWHIDQSULPDULO\ turbidites is far less than that of submarine turbidites (Wu, consists of muddy and calcareous sandstones. Huang (1999) 1986; Feng et al, 2010). VKRZHGWKDWZHOO(3SHQHWUDWHGWKHWXUELGLWHIDQDQG :HVWXGLHGWKHLQLWLDOL]DWLRQDQGJURZWKSURFHVVRIWKH UHYHDOHGPDLQO\EURZQJUD\DQGGDUNJUD\PXGVWRQHZKLFK lacustrine turbidite developed in the Wenchang Formation of ZDVLQWHUEHGGHGZLWKORZPDWXULW\VDQGVWRQH the Enping Sag from the aspects of provenance, topography, 3.3 Major controls on the turbidite fan sedimentation triggering factors and preservation. 3.3.1 Provenance analysis Great progress has been made in studying the distribution, 7KH(QSLQJ6DJLVDVWURQJO\VHSDUDWHGULIWLQJEDVLQ Pet.Sci.(2013)10:292-302 297
ZKLFKKRVWVWKH(RFHQH:HQFKDQJ)RUPDWLRQ )LJ)LJ in the south side. From geological background analysis of the formation and In the early stage of the formation of the Enping Sag, GLVWULEXWLRQRIWKHWXUELGLWHIDQLWVHHPVWKDWWKHUHDUHWZR WKHQRUWKXSOLIW]RQHZDVXSOLIWHGWRDUHODWLYHO\ORZH[WHQW SRWHQWLDOSURYHQDQFHVIRUWKHVHGLPHQWV WKHQRUWKXSOLIW]RQH SURYLGLQJDVPDOODPRXQWRIGHSRVLWV PDLQO\¿QHJUDLQHG IRU LQWKHQRUWKVLGHRIWKH(QSLQJ6DJDQGWKH3DQ\XORZXSOLIW the Enping Sag. Correspondingly, the Wenchang Formation
113° 40' 112° 60'
N PY1-1
North Fault Belt 20° 20° 50' Enping Sag 50'
EP12-1
EP11-1 20° 40' PY14-5
EP18-3
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0 10 20km EP23-1 Legend
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Fig. 7 Palaeogeographic map of the Wenchang Formation in the Enping Sag
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2000 T60
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Fig. 8 7\SLFDOVHLVPLFSUR¿OHVVKRZLQJWKHFKDUDFWHULVWLFVRIWKHWXUELGLWHVDQGERG\$$ƍSUR¿OH OHQWLFXODUVKDSHGRQWKH VWULNHGLUHFWLRQSUR¿OH %%ƍSUR¿OH SDUDOOHOSURJUDGDWLRQRQWKHGLSGLUHFWLRQSUR¿OH/RFDWLRQRISUR¿OHVKRZQLQ)LJ 298 Pet.Sci.(2013)10:292-302
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Fig. 9'HEULVVDPSOHVRIWKHWXUELGLWHIDQIURPZHOO(3 D PGHWULWDOJUDLQVZLWKSRRUVRUWLQJDQGURXQGLQJLQWHUJUDQXODUSRUHVDUHFHPHQWHGE\FDOFLWHDQGPXGLQWKHPDQQHURIEDVDOFHPHQWDWLRQ ;1LFROVî E PSRRUVRUWLQJWKHTXDUW]RYHUJURZWKVDQGLQWHUJUDQXODUSRUHVDUH¿OOHGE\FOD\PDWUL[VLQJOHSRODUî F WKHVDPH DV E ;1LFROVî G PGHWULWDOJUDLQVZLWKSRRUVRUWLQJDQGURXQGLQJDUHVWURQJO\FRPSDFWHGZLWKOLQHFRQWDFWVDQGFRQFDYHFRQYH[ FRQWDFWVIHOGVSDUVZHUHVOLJKWO\VHULFLWL]DWHGDQGLQWHUJUDQXODUSRUHVDUH¿OOHGE\FOD\PDWUL[QRLQFOXVLRQVLQTXDUW]JUDLQV;1LFROVî H PFKORULWHFRDWLQJVFRYHUWKHTXDUW]JUDLQVVLQJOHSRODUî I PIHOGVSDUVZHUHVOLJKWO\VHULFLWL]DWHG;1LFROVî
ZDVPDLQO\PXGVWRQHDQGKDGDORZGHSRVLWLRQUDWHLQWKLV because of fast subsidence of the north side, the north side VWDJH7KHQWKHKHLJKWGLIIHUHQFHLQFUHDVHGEHWZHHQWKH LVORZHUWKDQWKHVRXWKVLGHLQWKH(QSLQJ6DJLQWKLVVWDJH QRUWKXSOLIW]RQHDQGWKHGHSRVLWLRQDOFHQWHUDQGWKH(QSLQJ 7KHIDVWDFFXPXODWLRQRIIOXYLDOGHOWDLFVHGLPHQWVEHWZHHQ 6DJULIWHGIXUWKHUZKLFKFDXVHGDQLQFUHDVHRIHURVLRQLQWKH WKH3DQ\XORZXSOLIWDQGWKH(QSLQJ6DJSURPRWHGWKH QRUWKXSOLIW]RQH6RÀXYLDODQGGHOWDLFGHSRVLWV PDLQO\¿QH formation of slopes. With increasing clastic sedimentation, JUDLQHG ZKLFKSUHGRPLQDWHO\DFFXPXODWHGLQWKHQRUWKXSOLIW the sediments can slide in topographically unstable areas of ]RQHDUHWKHPDMRUVRXUFHIRUWKHGHSRVLWLRQRIWKH:HQFKDQJ WKHVORSHDQGEHWUDQVSRUWHGEDVLQZDUGE\JUDYLW\ÀRZDQG Formation. ¿QDOO\GHSRVLWLQWKHVHPLGHHSODNH±GHHSODNHHQYLURQPHQW %DVHGRQWKHDQDO\VLVRIVHLVPLFUHÀHFWLRQFKDUDFWHULVWLFV 3.3.3 Triggering conditions and distribution of the turbidite fan, this fan develops close 7XUELGLWHVUHVXOWIURPVXGGHQJUDYLW\ÀRZV7KHSURFHVV WRWKH3DQ\XORZXSOLIW VRXWKHUQVLGHRIWKH(QSLQJ6DJ FRPPRQO\RFFXUVZKHQVHGLPHQWVDFFXPXODWHRQWKHPDUJLQ DQGVKRZVZHGJHVKDSHGREOLTXHSURJUDGDWLRQUHIOHFWLRQ RIEDVLQDQGDUHWKLFNHQRXJK7KHVHGLPHQWVVOLGHGRZQWKH DQGWKLQVRXWIURPWKH3DQ\XORZXSOLIWWRWKHEDVLQFHQWHU VORSHRQFHWKHZHLJKWRIWKHVHGLPHQWVH[FHHGWKHLUVKHDU 6(1: )LJ%%ƍ $OOWKHVHREVHUYDWLRQVVXJJHVW VWUHQJWK,IWKHUHZHUHHDUWKTXDNHVWVXQDPLVZDYHVVWRUP WKDWWKH3DQ\XORZXSOLIWLVWKHPDLQVRXUFHRIWKHWXUELGLWH ÀRZVDQGIDXOWDFWLYLWLHVZKHQWKHVHGLPHQWVDUHDWWKHFULWLFDO fan in the Wenchang Formation. In addition, Huang (1999) VOLGLQJVWDJHWKHVHGLPHQWVZLOOEHHDVLO\WUDQVSRUWHGGRZQ studied the drilling data and seismic facies of the Wenchang WKHEDVLQVORSHDQGIRUPWXUELGLWHÀRZV )RUPDWLRQDQGFRQFOXGHGWKDWWKH3DQ\XORZXSOLIWLVWKH 7KHIRUPDWLRQRIWKHWXUELGLWHIDQLQWKH:HQFKDQJ primary supplying source for alluvial fan and braided river Formation mainly resulted from the second episode of the depositional system. =KXTLRQJPRYHPHQWZKLFKZDVRQHRIWKHPDLQWHFWRQLF 3.3.2 Morphology analysis PRYHPHQWVLQWKHHDUO\7HUWLDU\ZKLFKRFFXUUHGLQWKH In a variety of tectonic-stratigraphic settings, slope ODWH(RFHQHDQGHDUO\2OLJRFHQH 0D 7KLVWHFWRQLF topography has been demonstrated to playing a major role movement, lasted for about 3 Ma, caused substantial in sediment routing and deposition (Jackson et al, 2008). GHQXGDWLRQLQWKHVWXG\DUHDDVVRFLDWHGZLWKIDXOWLQJDQG Generally, the sediments at a higher rate of sediment supply PDJPDWLVP7KHEDVLQULIWLQJDIIHFWHGE\WKHVHFRQGHSLVRGH DQGGHSRVLWLRQPD\VOLGHEDVLQZDUGPRUHHDVLO\WKDQWKRVHDW RIWKH=KXTLRQJPRYHPHQWRSHQHGWKHFRQQHFWLRQEHWZHHQ DORZHUUDWHRIVHGLPHQWVXSSO\7\SLFDOO\WKHFRDUVHURUPRUH the south of Pearl River Mouth Basin and the sea. In addition, irregular the clastic grains, the more easily the sediments the lake of the Enping Sag expanded gradually in this stage ZRXOGVOLGHEDVLQZDUG (Wang et al, 2011). In the late depositional stage of the Affected by the Shenhu movement and the second episode Wenchang Formation, the basement subsidence of the Enping of the Zhuqiong movement, faults developed in Eocene are 6DJZDVPDLQO\FRQWUROOHGE\ERXQGDU\IDXOWVLQWKHQRUWK mainly boundary faults and minor small faults (Fig. 10). VLGHZKLFKGLSUHODWLYHO\VWHHSO\DQGWKHVXEVLGHQFHFHQWHULQ 7KHFRQWLQXRXVDFWLYLW\RIERXQGDU\IDXOWVFDXVHGIXUWKHU WKLVVWDJHZDVFORVHWRWKHQRUWKHUQERXQGDU\IDXOWV7\SLFDOO\ VXEVLGHQFHRIWKHVDJ,QWUDEDVLQVWUXFWXUHVKRZVWKDW WKHLQWUDEDVLQVWUXFWXUHVKRZVWKDWWKHQRUWKLVORZHUWKDQWKH Pet.Sci.(2013)10:292-302 299 south of the Enpin Sag in this stage. Affected by the second reservoir forecasting and oil-bearing property evaluations, episode of the Zhuqiong movement in the late Eocene, the ZKLFKH[WUDFWVRSWLPDOFRPSRVLWHDWWULEXWHVIURPDYDULHW\RI HDUO\IDQGHOWDVHGLPHQWVZKLFKDFFXPXODWHGRQWKH3DQ\X conventional seismic attributes to detect reservoir features. ORZXSOLIW]RQHZHUHWULJJHUHGE\WHFWRQLFIDFWRUVDQGPRYHG Appropriate use of seismic attribute analysis can greatly to the subsidence center of the Enping Sag, finally forming reduce the uncertainty of reservoir property prediction in the turbidite fan. WDUJHWDUHDVZLWKRXWGULOOLQJDQGFDQKHOSIRUHVWLPDWLQJ 3.3.4 Preservation conditions hydrocarbon properties or making reservoir management *HQHUDOO\WXUELGLWHVHGLPHQWVDUHSUHVHUYHGEHORZ decisions. WKHZDYHEDVHDQGUHZRUNHGE\FRPSOLFDWHGZDWHUIORZV 0HDQZKLOH$92DWWULEXWHDQDO\VLVKDVEHHQSURYHG DERYHWKHZDYHEDVH3UHYLRXVVWXGLHVLQGLFDWHWKDWWXUELGLWH to be effective in detecting the oil-bearing properties in IDQVW\SLFDOO\GHYHORSHGLQGHHSZDWHUODNHRUPDULQH sandstone reservoirs, and is applied in the prediction of oil- HQYLURQPHQWV6HGLPHQWDU\VWXGLHVLQWKLVVWXG\DUHDVKRZ EHDULQJ]RQHV7KHUHVXOWVKRZVWKDWDEXQGDQWK\GURFDUERQ WKDWWKHZDWHUGHSWKRIWKH(QSLQJ6DJLQ(RFHQHLVUHODWLYHO\ EULJKWVSRWVDQG$92DQRPDOLHVDUHUHÀHFWHGRQWKHVHLVPLF deep, and semi-deep and deep lake facies developed in the data of the turbidite fan (Fig. 11), revealing that this fan is a EDVLQFHQWHU7KHVHGLPHQWVSULPDULO\FRQVLVWRIPXGVWRQHDQG promising oil-bearing prospect. VLOW\PXGVWRQHZLWKDORZGHSRVLWLRQDOUDWH7KHGHHSZDWHU 7KHRLOEHDULQJSURSHUWLHVRIWKLVWXUELGLWHIDQZHUH¿UVWO\ environment helps greatly in forming and preserving the GHWHFWHGE\H[WUDFWLQJORZIUHTXHQF\DQGKLJKIUHTXHQF\ turbidite fan. RIWKHVHLVPLFZDYHVZKHQSURSDJDWLQJWKURXJKWKHRLO EHDULQJ]RQHLQWKLVIDQ7KHUHVXOWVVKRZWKDWWKHORZ 4 The perspective of petroleum exploration IUHTXHQF\HQHUJ\ +] RIWKHRLOEHDULQJ]RQHLQWKLV of the turbidite fan fan is enhanced, its frequency decreases and absorption FRHI¿FLHQWLQFUHDVHV )LJ :KLOHWKHHQHUJ\RIWKHKLJK 4.1 Analysis of oil-bearing properties IUHTXHQFLHV +] ZHDNHQVZKLFKLVDW\SLFDORLO Seismic attribute technology provides a useful tool in bearing characteristic.
1500 B B'
2000
2500
3000 TWT, ms TWT,
3500
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1500
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Top Enping Formation 2500 T70 TWT, ms TWT,
3000 The north uplift zone T80 Top Wenchang Formation The south uplift zone
3500 The second episode of Zhuqiong movement T100
4000 The first episode of Zhuqiong movement
Fig. 10 Schematic reconstructions of the Enping Sag during Eocene and early Oligocene, illustrating the development and HYROXWLRQRI(RFHQHVWUDWD7KHUHFRQVWUXFWLRQLVEDVHGRQWKHVHLVPLFVHFWLRQ%%ƍVKRZQLQ)LJ 300 Pet.Sci.(2013)10:292-302
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-80 1500 1500 1500 1500
-60
2000 2000 2000 2000 -40
-20 2500 2500 2500 2500
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TWT, ms TWT, 3000 3000 3000 3000 20
40 3500 3500 3500 3500
60
4000 4000 4000 4000 80
100 4500 4500 4500 4500
Fig. 11%ULJKWVSRWVDQG$92DQRPDOLHVLQWXUELGLWHLQZHOO(3 OLQH(&B(S
Well EP17-3-1 penetrated the front side of the turbidite 3DOHRQWRORJ\DQGJHRFKHPLFDOVWXGLHVVKRZWKDWWKLFN fan and provided useful information for its reservoir property mudstones in the Wenchang Formation are the main source evaluations. Abnormally high pressure are encountered at rocks in the Enping Sag (Jiang and Yang, 2000). On one PZKLFKLVWKHLQWHUYDOLQZKLFKWKHWXUELGLWHIDQ KDQGVRXUFHURFNFKDUDFWHUL]DWLRQVKRZVWKDWRUJDQLFPDWWHU GHYHORSHG7KHSUHVVXUHFRHI¿FLHQWLQFUHDVHVVKDUSO\DVKLJK LVDEXQGDQWLQWKLVVHWRIODFXVWULQHGHSRVLWVZLWKD72& as 1.5 in this interval (Fig. 13). content of over 2% and the chloroform bitumen A is over 0.1% (Huang, 1998). In short, the favorable hydrocarbon generating 4.2 Analysis of reservoir forming conditions potential of source rocks provides prospective conditions for ,QWKH(RFHQHWKH(QSLQJ6DJZDVDVWURQJO\VHSDUDWHG reservoir formation. ULIWEDVLQZKHUHWKHODFXVWULQHIDFLHVRIWKH:HQFKDQJ On the other hand, abnormally high pressure is one Formation deposited in a semi-deep to deep lake environment. of the main factors that commonly help improving the
3041 3121 3201 3281 3361 3441 3521 3601 3681 3761 3841 3921 4001 4081 4161 2800
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40 Low frequency energy of the oil-bearing zone increases 20
Low frequency energy 0
The frequency of the 30 gas-bearing zone decreases 25 , Hz
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100 Absorption 0
Fig. 12 Detection of oil-bearing properties of the turbidite fan in the Wenchang Formation Pet.Sci.(2013)10:292-302 301
Depth, m GR, API Depth, m Core profile DTȝVP 0 250 50 100 4000
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Fig. 136KDUSLQFUHDVHLQPHDVXUHGSUHVVXUHZLWKLQPRIZHOO(3LQWKH(QSLQJ6DJ
TXDOLW\RIGHHSUHVHUYRLUVLQEDVLQVZLWKFKDUDFWHULVWLFVRI 6HLVPLFDWWULEXWHFKDUDFWHUL]DWLRQVKRZVWKDWWKHHQHUJ\ high geothermal gradient and overpressure in deep layers. RIORZIUHTXHQF\LVHQKDQFHGDQGHQHUJ\RIKLJKIUHTXHQF\ $EQRUPDOO\KLJKSUHVVXUHZDVGHWHFWHGLQWKHVHFWLRQZKHUH LVZHDNHQHGZKHQVHLVPLFZDYHVSURSDJDWHWKURXJKWKHRLO the turbidite fan developed in the Wenchang Formation of EHDULQJ]RQHLQWKLVIDQ$92DQRPDOLHVDUHVKRZQLQWKH ZHOO(38QGHUDEQRUPDOO\KLJKSUHVVXUHFRQGLWLRQV seismic data and abnormally high pressures are encountered produced by hydrocarbon generation, migration and LQPRIZHOO(37KHHYLGHQFHUHYHDOVWKDW accumulation, the reservoir physical properties of the fan hydrocarbons, generated from the Wenchang Formation, had ZHUHHIIHFWLYHO\SUHVHUYHGDQGLPSURYHGWRVRPHH[WHQW PLJUDWHGDQGDFFXPXODWHGLQWRWKHWXUELGLWHIDQ7KLVIDQLV 7KLVIDQKDGDEXULDOGHSWKRIRYHUPZKHQWKH(QSLQJ expected to be prospective for hydrocarbon exploration. Sag entered the key hydrocarbon accumulation stage (Chen HWDO DQGWKHUHVHUYRLUSURSHUWLHVDUHFKDUDFWHUL]HG Acknowledgements E\JHQHUDOO\PLGGOHORZSRURVLW\DQGORZSHUPHDELOLW\7KH 7KLVVWXG\LV¿QDQFLDOO\VXSSRUWHGE\WKH&KLQD1DWLRQDO WXUELGLWHIDQGHYHORSHGW\SLFDOO\ZLWKLQODFXVWULQHIDFLHVRI 6FLHQFHDQG7HFKQRORJ\3URMHFW =; :H WKH:HQFKDQJ)RUPDWLRQZDVFORVHWRVRXUFHURFNVDQGKDG DUHJUDWHIXOWR;XH/LDQKXD=KXR;L]KXQ-LQ+XLMXDQDQG good seal conditions. All factors mentioned above point out a /L Fu N, Ding F, He S B, et al. Source rocks evaluation and reservoir 5HGLQ72LODQGJDVSURGXFWLRQIURPVXEPDULQHIDQVRIWKH/RV$QJHOHV characteristics analysis in Enping Sag, Pearl River Mouth Basin. %DVLQ,Q %LGGOH.7HG$FWLYH0DUJLQ%DVLQ$$3*0HPRLU China Offshore Oil and Gas. 2007. 19(5): 295-299 (in Chinese) 1991. 239-259 *DR<;DQG:X&<7KHVHGLPHQWDU\FKDUDFWHULVWLFVRIWKHODFXVWULQH Shanmugam G. 50 years of the turbidite paradigm (1950s-1990s): Deep- IDQVLQWKH'DZDQKHRLOEHGRI/LDRKH%DVLQ$FWD6HGLPHQWRORJLFD ZDWHUSURFHVVHVDQGIDFLHVPRGHOV²DFULWLFDOSHUVSHFWLYH0DULQH Sinica. 1985. 3(4): 83-94 (in Chinese) and Petroleum Geology. 2000. 17(2): 285-342 +XDQJ/)7KHDSSOLFDWLRQRIVHTXHQFHVWUDWLJUDSK\IRUDQDO\VLVLQ 6KDQPXJDP*7HQWXUELGLWHP\WKV(DUWK6FLHQFH5HYLHZV QRQPDULQHGHSUHVVLRQZLWKH[DPSOHRI(QSLQJ6DJ3HDUO5LYHU 4): 311-341 Mouth Basin. China Offshore Oil and Gas. 1999. 13(3): 159-168 (in 6WRZ'$9DQG0D\DOO0'HHSZDWHUVHGLPHQWDU\V\VWHPV 1HZ Chinese) models for the 21st century. Marine and Petroleum Geology. 2000. Huang Z J. Nonmarine source rock and petroleum formation of Pearl 17(2): 125-135 River Mouth Basin. China Offshore Oil and Gas. 1998. 12(4): 255- 9LDQD$)LJXHLUHGR$)DXJqUHV-&HWDO7KH6DR7RPpGHHS 261 (in Chinese) VHDWXUELGLWHV\VWHP VRXWKHUQ%UD]LO%DVLQ &HQR]RLFVHLVPLF Jac kson C A L, Barber G P and Martinsen O J. Submarine slope stratigraphy and sedimentary processes. AAPG Bulletin. 2003. 87(5): morphology as a control on the development of sand-rich turbidite 873-894 depositional systems: 3D seismic analysis of the Kyrre Fm (Upper :DONHU5*7XUELGLWHVDQGVXEPDULQHIDQV,Q :DONHU5*DQG-DPHV &UHWDFHRXV 0nO¡\6ORSHRIIVKRUH1RUZD\0DULQHDQG3HWUROHXP 13)DFLHV0RGHOV 5HVSRQVHWR6HD/HYHO&KDQJHV2WWDZD Geology. 2008. 25(8): 663-680 Geological Association of Canada. 1992. 239-263 Jia ng D X and Yang H Q. Original environment of Eogene petroleum :DQJ-+/LX/+&KHQ6+HWDO7HFWRQLFVHGLPHQWDU\UHVSRQVHV source rocks in the Pearl River Mouth Basin. Acta Sedimentologica to the second episode of the Zhu-Qiong movement in the Enping Sinica. 2000. 18(3): 469-474 (in Chinese) Depression, Pearl River Mouth Basin and its regional tectonic /DL:4DQG*X-<7XUELGLW\IDQLQWKHRLODQGJDVEHDULQJEDVLQ VLJQL¿FDQFH$FWD3HWUROHL6LQLFD LQ&KLQHVH in Bohai Bay. Acta Sedimentologica Sinica. 1984. 2(4): 47-57 (in :DQJ<):DQJ<0;X4HWDO7KHHDUO\PLGGOH0LRFHQHVXEPDULQH Chinese) fan system in the Pearl River Mouth Basin, South China Sea. /HL+<=RX:+:DQJ/-HWDO7KHWXUELGLWHIRXQGLQ&KD[L$UHD Petroleum Science. 2012. 9(1):1-9 and its importance for petroleum exploration. Acta Sedimentologica Wang Y M, Xu Q, Li D, et al. Late Miocene Red River submarine fan, Sinica. 1999. 17(1): 89-94 (in Chinese) QRUWKZHVWHUQ6RXWK&KLQD6HD&KLQHVH6FLHQFH%XOOHWLQ /L=:7KHDQDO\VLVRIK\GURFDUERQDFFXPXODWLRQFRQGLWLRQVLQ(QSLQJ 56(14): 1488-1494 Sag. China Offshore Oil and Gas. 1999. 13(3): 174-180 (in Chinese) :X&<5HVHDUFK3URJUHVVRI7XUELGLWH'HSRVLWVDQG)DQ'HOWDV Liu Z, Zhao Z Z, Zhao Y, et al. Predominant characteristics of formation Beijing: Petroleum Industry Press. 1986. 1-19 (in Chinese) and distribution for lithologic reservoirs in petroliferous basin. Acta =KDQJ*&7HFWRQLFHYROXWLRQRIGHHSZDWHUDUHDRIQRUWKHUQFRQWLQHQWDO Petrolei Sinica. 2006. 27(1): 17-23 (in Chinese) margin in South China Sea. Acta Petrolei Sinica. 2010. 31(4): 528- 0LDR6'=KDQJ*&/LDQJ-6HWDO6HLVPLFUHÀHFWLRQFKDUDFWHULVWLFV 533 (in Chinese) and sedimentary environment analysis of Wenchang Formation in Zhuo X Z, Wang Q, Chen G J, et al. Vertical porosity variation of clastic Northern Depression of Zhujiangkou Basin. Natural Gas Geoscience. reservoir rock in Enping Sag, Pearl River Mouth Basin. Natural Gas 2010. 21(5): 844-850 (in Chinese) Geoscience. 2007. 18(5): 643-647 (in Chinese) 3DQJ;&KHQ&03HQJ'-HWDO7KH3HDUO5LYHU'HHSZDWHU)DQ Zhuo X Z, Wang Q, Chen G J, et al. Analysis of diagenetic process System & Petroleum in South China Sea. Beijing: Science Press. DQGG\QDPLFUHVHUYRLUDVVHVVPHQWRQWKHORZHUSDUWRI(QSLQJ 2007. 6 (in Chinese) Formation, Enping Sag. Acta Sedimentologica Sinica. 2008. 26(2): 3DQJ;6KHQ-