Reservoir quality differences within the submarine fan under a steep continental slope setting: A case study of the X gas field, Rovuma Basin, East Africa

doi:10.3969/j.issn.2096-1693.2025.01.020

Abstract

Abstract:

The submarine fan is an important reservoir for oil and gas in deep water areas. The differences in reservoir quality have a significant impact on the differential accumulation and exploitation of oil and gas. Previous studies have conducted extensive research on the differences in reservoir quality of submarine fans. However, the characteristics and distribution patterns of reservoir quality differences within submarine fans under a steep continental slope background are still unclear. This paper takes the Oligocene submarine fan reservoir in the X gas field of the Rovuma Basin in East Africa as the research object. By integrating core, well logging and seismic data, an in-depth study has been carried out on the control of reservoir quality differences and distribution patterns of submarine fan sedimentary microfacies and lithofacies under the steep continental slope background. The results show that the changes in reservoir quality within the submarine fan are mainly controlled by rock texture, lithofacies (association) and sedimentary microfacies under the circumstance of weak diagenesis. Grain sorting and clay content mainly control the porosity and permeability of the reservoir, respectively, but the relationship between grain size and reservoir properties is very complex. In sand-rich lithofacies, fine sandstones have the highest porosity due to their good sorting, and massive gravel-bearing coarse sandstones have the highest permeability due to their low clay content. Under the steep continental slope background, the submarine fan sedimentary microfacies are arranged in the order of muddy channel-sandy channel-lobe main body-lobe edge along the source direction, resulting in the source-directional differences in reservoir quality in the order of “poor, good, and poor”. The proximal muddy channel consists of fine-grained and clay-rich lithofacies, with overall poor physical properties. In the middle position, the sandy channel and lobe main body change to massive gravel-bearing coarse sandstone lithofacies and medium-coarse sandstone lithofacies, with low clay content and improved to good physical properties. Among them, the reservoir quality of the sandy channel is better than that of the lobe main body. The internal high porosity and high permeability zones of the sandy channel are in the form of elongated lenses, while the relatively high porosity and high permeability areas of the lobe main body are in the shape of lobes. The distal lobe edge changes to fine-grained lithofacies (fine-medium sandstone, fine sandstone) with increased clay content and gradually deteriorated physical properties.

Key words: steep continental slope, submarine fan, Ruvuma Basin, reservoir quality differences, lithofacies

摘要：

海底扇作为深水区重要的油气储集场所，其储层质量差异对于油气差异聚集及开采具有重要的影响。前人对海底扇储层质量差异进行过较多的研究，但对于陡陆坡背景下的海底扇内部储层质量差异特征及分布样式尚不清楚。本文以东非鲁伍马盆地X气田渐新统海底扇储层为研究对象，综合应用岩心、测井及地震资料，对陡陆坡背景下的海底扇沉积微相与岩相对储层质量差异的控制作用及分布样式进行了深入的研究。结果表明，在弱成岩作用下，海底扇内储层质量的变化主要受岩石沉积组构、岩相(组合)和沉积微相的控制。颗粒分选和泥质含量分别控制储层的孔隙度和渗透率，颗粒大小与储层物性之间的关系很复杂。富砂型岩相中，细砂岩相因其分选性好而具有最高的孔隙度，而块状含砾粗砂岩相因其低泥质含量而具有最高渗透率。在陡陆坡背景下，顺源方向海底扇构型单元依次为泥质水道-砂质水道-朵叶主体-朵叶边缘，导致了储层质量“差-好-差”的顺源差异。近源端泥质水道为细粒及富泥型岩相，其物性整体较差；中部砂质水道与朵叶主体变为块状含砾粗砂岩相和中-粗砂岩相，泥质含量低，物性变好，其中，砂质水道储层质量优于朵叶主体，其内部高孔渗带呈长透镜状，朵叶体相对高孔渗区呈朵状；远端朵叶边缘变为细粒的岩相(中-细砂岩相、细砂岩相)，泥质含量变高，物性逐渐变差。

关键词: 陡陆坡, 海底扇, 鲁伍马盆地, 储层质量差异, 岩相

CLC Number:

XIONG Qicong, WU Shenghe, XU Zhenhua, CHEN Mei, WANG Min, YU Jitao, WANG Ruifeng. Reservoir quality differences within the submarine fan under a steep continental slope setting: A case study of the X gas field, Rovuma Basin, East Africa[J]. Petroleum Science Bulletin, 2025, 10(4): 633-646.

熊绮聪, 吴胜和, 徐振华, 陈梅, 王敏, 余季陶, 王瑞峰. 陡陆坡背景下的海底扇内部储层质量差异——以东非鲁伍马盆地X气田为例[J]. 石油科学通报, 2025, 10(4): 633-646.

/ / Recommend / Download Citations

URL: https://sykxtb.cup.edu.cn/EN/10.3969/j.issn.2096-1693.2025.01.020

https://sykxtb.cup.edu.cn/EN/Y2025/V10/I4/633

Figures/Tables 14

Fig. 1 Geological structure location (a) and steep slope morphology (b) of deepwater X gas field in Ruvuma Basin

Fig. 2 Seismic profile and sedimentary microfacies distribution map of the study area (modified according to reference^[13])

Fig. 3 Lithofacies type photograph of the study area

Fig. 4 Lithofacies type distribution of the study area

Fig. 5 Intersection diagram of porosity and permeability of submarine fan reservoir

Fig. 6 Pore and throat types of submarine fan reservoir in study area

Fig. 7 Distribution of pore permeability and argillaceous content in different lithofacies of study area

Fig. 8 Porosity and permeability relationship of different lithofacies

Fig. 9 Planar distribution of porosity and permeability within the submarine fan reservoir in the study area.

Fig. 10 Graphs showing influence of diagenesis on reservoir quality

Fig. 11 Microscopic characteristics and pore structure distribution of different lithofacies

Fig. 12 Relationship between sedimentary fabric and physical properties or permeability of seafloor fan-lobes reservoir in deep water X gas field

Table 1 Physical fabric characteristics and original porosity and permeability distribution of various lithofacies

岩相	分选系数		泥质含量		原始孔隙度/%		原始渗透率/D
岩相	范围	平均值	范围	平均值	范围	平均值	范围	平均值
含砾粗砂岩	2.36~2.65	2.50	0.7~5.0	2.27	27.5~28.2	27.8	23~32	27.4
中-粗砂岩	1.82~2.17	2.01	0.9~10.3	3.60	29.0~32.0	30.6	22~27	24.4
中-细砂岩	1.48~2.02	1.73	2.6~9.4	4.31	33.0~34.8	33.9	25~30	28.3
细砂岩	1.50~1.87	1.70	3.6~16.9	8.68	33.8~36.0	34.9	4~9	7.0

Fig. 13 Reservoir quality difference model of submarine fan in deep water X gas field, Rovuma Basin, East Africa

References 33

[1]	李大伟, 李德生, 陈长民, 等. 深海扇油气勘探综述[J]. 中国海上油气, 2007, 19(1): 18-24.
	[LI D W, LI D S, CHEN C M, et al. An overview of hydrocarbon exploration in deep submarine fans[J]. China Offshore Oil and Gas, 2007, 19(1): 18-24.]
[2]	CROSS N, CUNNINGHAM A, COOK R, et al. Three-dimensional seismic geomorphohgy of a deep-water slope-channel system: The Sequoia field, offshore west Nile Delta, Egypt[J]. AAPG Bulletin, 2009, 93: 1063-1086.
[3]	LIEN T, MIDTBØ R E, MARTINSEN O. Depositional facies and reservoir quality of deep-marine sandstones in the Norwegian Sea[J]. Norsk Geologisk Tidsskrift, 2006, 86: 71-92.
[4]	SURLYK F, KOLBYE JENSEN S, ENGKILDE M. Deep channels in the Cenomanian-Danian Chalk Group of the German North Sea sector: Evidence of strong constructional and erosional bottom currents and effect on reservoir quality distribution[J]. AAPG Bulletin, 2008, 92: 1565-1586.
[5]	梁建设, 孔令武, 邱春光, 等. 东非海岸盆地渐新世浊积体沉积特征及油气勘探意义[J]. 中国海上油气, 2021, 33(6): 25-33.
	[LIANG J S, KONG L W, QIU C G, et al. Sedimentary characteristics of Oligocene turbidite and its significance for hydrocarbon exploration in coastal basins of East Africa[J]. China Offshore Oil and Gas, 2021, 33(6): 25-33.]
[6]	BRUNT R L, MCCAFFREY W D. Heterogeneity of fill within an incised channel: The Oligocene Grès du Champsaur, SE France[J]. Marine and Petroleum Geology, 2007, 24(6): 529-539.
[7]	LI Q, JIANG Z, LIU K, et al. Factors controlling reservoir properties and hydrocarbon accumulation of lacustrine deep-water turbidites in the Huimin Depression, Bohai Bay Basin, East China[J]. Marine and Petroleum Geology, 2014, 57: 327-344.
[8]	ZHANG J, WU S, WANG X, et al. Reservoir quality variations within a sinuous deep water channel system in the Niger Delta Basin, offshore West Africa[J]. Marine and Petroleum Geology, 2015, 63: 166-188.
[9]	ROTIMI O J, AKO B D, ZHENLI W. Stratigraphy and reservoir quality of the turbidite deposits, western sag, Bohai bay, China P.R[J]. Journal of African Earth Sciences, 2014, 99: 517-528.
[10]	林煜, 吴胜和, 王星, 等. 尼日尔三角洲盆地深水油田A海底扇储层质量差异[J]. 石油与天然气地质, 2014, 35(4): 494-502.
	[LIN Y, WU S H, WANG X, et al. Reservoir quality differences of submarine fans in deep-water oilfield A in Niger Delta Basin, West Africa[J]. Oil & Gas Geology, 2014, 35(4): 494-502.]
[11]	王敏, 张佳佳, 王瑞峰, 等. 东非鲁伍马盆地深水海底扇储集层质量差异及主控因素[J]. 石油勘探与开发, 2022, 49(3): 491-501. doi: 10.11698/PED.20210819
	[WANG M, ZHANG J J, WANG R F, et al. Quality variations and controlling factors of deepwater submarine-fan reservoirs, Rovuma Basin, East Africa[J]. Petroleum Exploration And Development, 2022, 49(3): 491-501.]
[12]	HUANG Y, KANE I A, ZHAO Y. Effects of sedimentary processes and diagenesis on reservoir quality of submarine lobes of the Huangliu Formation in the Yinggehai Basin, China[J]. Marine and Petroleum Geology, 2020, 120: 104526.
[13]	CHEN M, WU S, WANG R, et al. Sedimentary architecture of submarine lobes affected by bottom currents: Insights from the Rovuma Basin offshore East Africa[J]. Basin Research, 2024, 36(1): e12829.
[14]	SHANMUGAM T. Process sedimentology and reservoir quality of deep-marine bottom-current reworked sands (sandy contourites): An example from the Gulf of Mexico[J]. AAPG Bulletin, 1993, 77(7): 1241-1259.
[15]	刘子玉, 吕明, 卢景美, 等. 东非鲁伍马盆地窄陆架背景下的深水沉积体系[J]. 海相油气地质, 2017, 22(4): 27-34.
	[LIU Z Y, LÜ M, LU J M, et al. Deepwater depositional system in the background of narrow shelf in the Ruvuma Basin, Eastern Africa[J]. Marine Origin Petroleum Geology, 2017, 22(4): 27-34.]
[16]	SALMAN G, ABDULA I. Development of the Mozambique and Ruvuma sedimentary basins, offshore Mozambique[J]. Sedimentary Geology - SEDIMENT GEOL, 1995, 96: 7-41.
[17]	陈宇航, 姚根顺, 吕福亮, 等. 东非鲁伍马盆地深水区构造-沉积演化过程及油气地质特征[J]. 海相油气地质, 2016, 21(2): 39-46.
	[CHEN Y H, YAO G S, LÜ F L, et al. Tectonic-sedimentary evolution and petroleum geology characteristics in deepwater area in Rovuma Basin, East Africa[J]. Marine Origin Petroleum Geology, 2016, 21(2): 39-46.]
[18]	曹全斌, 曹旭文, 鲁银涛, 等. 东非鲁伍马盆地深水沉积体系及油气勘探意义[J]. 海洋地质与第四纪地质, 2021, 41(2): 173-180.
	[CAO Q B, CAO X W, LU Y T, et al. Deep water depositional system in Rovuma Basin, East Africa and its bearing on hydrocarbon exploration[J]. Marine Geology & Quaternary Geology, 2021, 41(2): 173-180.]
[19]	孙辉, 范国章, 邵大力, 等. 深水局部限制型水道复合体沉积特征及其对储层性质的影响——以东非鲁武马盆地始新统为例[J]. 石油与天然气地质, 2021, 42(6): 1440-1450.
	[SUN H, FAN G Z, SHAO D L, et al. Depositional characteristics of locally restricted channel complex in deep water and its influence on reservoir properties:A case study of the Eocene series,Rovuma Basin[J]. Oil & Gas Geology, 2021, 42(6): 1440-1450.]
[20]	孙辉, 刘少治, 范国章, 等. 深水复合水道体系沉积特征及时空演化规律——以东非鲁武马盆地中中新统为例[J]. 海洋学报, 2019, 41(01): 87-97.
	[SUN H, LIU S Z, FAN G Z, et al. Depositional characteristics and temporal and spatial evolution of deep water channel complex systems: A case study of Middle Miocene in the Rovuma Basin, East Africa[J]. Haiyang Xuebao, 2019, 41(01): 87-97.]
[21]	MAHANJANE E S, FRANKE D. The Rovuma delta deep-water fold-and-thrust belt, offshore Mozambique[J]. Tectonophysics, 2014, 614: 91-99.
[22]	孙辉, 唐鹏程, 陈宇航, 等. 东非鲁武马盆地陆坡深水沉积特征及主控因素[J]. 海洋地质与第四纪地质, 2016, 36(3): 59-68.
	[SUN H, TANG P C, CHEN Y H, et al. Characteristics and controlling factors of deepwater deposits on the continental slope of the Rovuma Basin, East Africa[J]. Marine Geology & Quaternary Geology, 2016, 36(3): 59-68.]
[23]	FONNESU M, PALERMO D, GALBIATI M, et al. A new world-class deep-water play-type, deposited by the syndepositional interaction of turbidity flows and bottom currents: The giant Eocene coral field in northern Mozambique[J]. Marine and Petroleum Geology, 2020, 111: 179-201.
[24]	LUAN X, LU Y, FAN G, et al. Deep-water sedimentation controlled by interaction between bottom current and gravity flow: A case study of Rovuma Basin, East Africa[J]. Journal of African Earth Sciences, 2021, 180: 104228.
[25]	CHEN M, WU S H, WANG R F, et al. Sedimentary architecture of submarine channel-lobe systems under different seafloor topography: Insights from the Rovuma Basin offshore East Africa[J]. Petroleum Science, 2024, 21(1): 125-142.
[26]	陈宇航, 姚根顺, 吕福亮, 等. 东非鲁伍马盆地渐新统深水水道-朵体沉积特征及控制因素[J]. 石油学报, 2017, 38(9): 1047-1058.
	[CHEN Y H, YAO G S, LÜ F L, et al. Sedimentary characteristics and controlling factors of Oligocene deep-water channel-lobe in Rovuma Basin of the East Africa[J]. Acta Petrolei Sinica, 2017, 38(9): 1047-1058.] doi: 10.7623/syxb201709006
[27]	郑占, 吴胜和, 许长福, 等. 克拉玛依油田六区克下组冲积扇岩相及储层质量差异[J]. 石油与天然气地质, 2010, 31(4): 463-471.
	[ZHENG Z, WU S H, XU C F, et al. Lithofacies and reservoirs of allluvial fan in the Lower Keramay Formation in the block-6 of Karamay oilfield, the Junggar Basin[J]. Oil & Gas Geology, 2010, 31(4): 463-471.]
[28]	HOUSEKNECHT D W. Assessing the relative importance of compaction processes and cementation to reduction of porosity in sandstones[J]. AAPG Bulletin, 1987, 71(6): 633-642.
[29]	吴胜和, 岳大力, 蒋欲强. 油矿地质学[M]. 北京: 石油工业出版社, 2021.
	[WU S H, YUE D L, JIANG Y Q. Oilfield geology[M]. Beijing: Petroleum Industry Press, 2021.]
[30]	SULLIVAN M, JENSEN G, GOULDING F, et al. Architectural analysis of deep-water outcrops: Implications for exploration and development of the Diana sub-basin, western gulf of Mexico[M]. SEPM Society For Sedimentary Geology, 2000.
[31]	SALLER A, WERNER K, SUGIAMAN F, et al. Characteristics of Pleistocene deep-water fan lobes and their application to an upper Miocene reservoir model, offshore East Kalimantan, Indonesia[J]. AAPG Bulletin, 2008, 92: 919-949.
[32]	SNEIDER R M. BARWIS J H, MCPHERSON J G, STUDLICK J R J. Reservoir description of sandstones.//BARWIS J H, MCPHERSON J G, STUDLICK J R J. Sandstone Petroleum Reservoirs[M]. New York, NY: Springer New York, 1990.
[33]	POSTMA G, NEMEC W, KLEINSPEHN K L. Large floating clasts in turbidites: A mechanism for their emplacement[J]. Sedimentary Geology, 1988, 58(1): 47-61.

Please choose a citation manager

Content to export