东非裂谷South Lokichar盆地石油地质特征与勘探潜力
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摘要
东非裂谷系是新生代陆内裂谷盆地群,分为西支和东支,以往被认为勘探风险较大。东支的South Lokichar盆地自2012年以来不断获得油气发现,促使学者对以往结论进行反思。通过对盆地的地震、钻井等地质资料综合研究,分析了其石油地质特征及成藏规律,并预测了盆地的勘探潜力与有利勘探方向。South Lokichar盆地作为小型断陷湖盆,具有西断东超的结构,自渐新世以来充填了河流—(扇)三角洲—湖泊沉积体系。钻井及露头资料揭示:盆地的下中新统Lokhone组和渐新统Loperot组烃源岩品质好,处于成熟—高成熟阶段;中新统的下Auwerwer段扇三角洲砂体储集物性较好,与上覆区域性泥岩盖层形成良好的储盖组合。盆地西部陡坡带主要发育构造圈闭,已发现的油田规模较大,储量占全盆地的99%;东部缓坡带保存条件较差,油气发现少。South Lokichar盆地西北部断块圈闭较发育,钻井证实具备与西部陡坡带相似的成藏条件,是有利的勘探区带。
The East African Rift System(EARS) is a Cenozoic intercontinental rift basin group consisting of two main rifts: the Western Branch and Eastern Branch. Exploration risk in EARS was considerable high in the past decades. However, since 2012, several oil discoveries have been found in South Lokichar Basin in the Eastern Branch. Scholars began to rethink the previous conclusions. Through integrated studies of seismic, well and other geological data from the South Lokichar Basin, its petroleum geological features and reservoir-forming mechanisms revealed, exploration potential evaluated and prospecting direction predicted. The Basin has a small-scale, mono-faulted structural characteristics, faulting in the west and overlapping in the east, and has been filled with a fluvial-(fan) delta-lacustrine depositional system since Oligocene. Based on the analysis of samples of wells and outcrops, it was determined that both the Miocene Lokhone shale and the Oligocene Loperot shale are high quality source rocks with mid-high maturity, the Miocene Lower Auwerwer fan delta sand is a good reservoir, and it forms a good combination with the overlying regional mudstone. In the western steep slope zone of the basin, structural traps were developed and large-scale oil fields formed with the reserve accounting for 99% of the whole basin. In the eastern gentle slope of the basin, however, poor containment condition led to only small-scale oil discoveries. In the northeastern area of the basin, fault-block traps are developed, which makes it a favorable exploration zone. Recent data from wells has confirmed that this area has similar petroleum accumulation conditions with the western steep slope zone.
The East African Rift System(EARS) is a Cenozoic intercontinental rift basin group consisting of two main rifts: the Western Branch and Eastern Branch. Exploration risk in EARS was considerable high in the past decades. However, since 2012, several oil discoveries have been found in South Lokichar Basin in the Eastern Branch. Scholars began to rethink the previous conclusions. Through integrated studies of seismic, well and other geological data from the South Lokichar Basin, its petroleum geological features and reservoir-forming mechanisms revealed, exploration potential evaluated and prospecting direction predicted. The Basin has a small-scale, mono-faulted structural characteristics, faulting in the west and overlapping in the east, and has been filled with a fluvial-(fan) delta-lacustrine depositional system since Oligocene. Based on the analysis of samples of wells and outcrops, it was determined that both the Miocene Lokhone shale and the Oligocene Loperot shale are high quality source rocks with mid-high maturity, the Miocene Lower Auwerwer fan delta sand is a good reservoir, and it forms a good combination with the overlying regional mudstone. In the western steep slope zone of the basin, structural traps were developed and large-scale oil fields formed with the reserve accounting for 99% of the whole basin. In the eastern gentle slope of the basin, however, poor containment condition led to only small-scale oil discoveries. In the northeastern area of the basin, fault-block traps are developed, which makes it a favorable exploration zone. Recent data from wells has confirmed that this area has similar petroleum accumulation conditions with the western steep slope zone.
引文
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[25] Rop B K,Patwardhan A M.Hydrocarbon of source rocks evaluation study of Lokichar Basin,northwestern Kenya[J].Journal of the Geological Society of India,2013,81(4):575-580.
[26] Rop B K.Hydrocarbon characteristics of source rocks in Loperot-1 well,NW Kenya[C]// Exploration & Production Geology.Nairobi,Kenya:AAPG,2011.
[27] 张燕,田作基,温志新,等.东非裂谷系东支油气成藏主控因素及勘探潜力[J].石油实验地质,2017,39(1):79-85.
[28] 赵伟,韩文明,胡滨,等.东非裂谷Albertine地堑石油地质条件和成藏规律[J].四川地质学报,2016,36(2):275-279.
[29] 蔡文杰,韩文明,许志刚,等.东非Lake Albert盆地构造调节带特征及其对油气成藏的控制作用[J].地质科技情报,2015,34(4):119-123.
[30] 周总瑛.我国东部断陷盆地石油排聚系数统计模型的建立[J].新疆石油地质,2009,30(1):9-12.
[31] 徐思煌,梁浩然,刘晓霞.生烃凹陷资源潜力快速评价新指标:烃源指数[J].地球科学与环境学报,2017,39(2):238-247.
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[34] Africa Oil Corp.Moving forward to development[EB/OL].[2018-11-12].http://www.africaoilcorp.com/ i/pdf/2017-09-05-CP.pdf.
[2] Morley C K,Nelson R A,Patton T L,et al.Transfer zones in the East Africa rift system and their relevance to hydrocarbon exploration in rifts[C].AAPG,1990,74(8):1234-1253.
[3] 胡滨,许志刚,韩文明,等.东非裂谷Rukwa盆地石油地质特征与勘探潜力[J].海洋地质前沿,2018,34(6):37-43.
[4] 胡滨,张世鑫,贾屾.东非裂谷Kerio Valley盆地石油地质特征与勘探潜力[J].石油化工应用,2018,37(6):110-113.
[5] 贾屾.肯尼亚北部裂谷盆地类型和演化及其对烃源岩的控制作用[J].海洋地质前沿,2017,33(2):19-25.
[6] 金宠,陈安清,楼章华,等.东非构造演化与油气成藏规律初探[J].吉林大学学报(地球科学版),2012,42(2):121-130.
[7] 张兴,童晓光.艾伯特裂谷盆地含油气远景评价——极低勘探程度盆地评价实例[J].石油勘探与开发,2001,28(2):102-106.
[8] 温志新,童晓光,张光亚,等.东非裂谷系盆地群石油地质特征及勘探潜力[J].中国石油勘探,2012,17(4):60-65.
[9] Tullow Oil plc.2017 full year-result [EB/OL].[2018-10-20].https://www.tullowoil.com/investors/results- reports-and-presentations.
[10] Aanyu K,Koehn D.Influence of pre-existing fabrics on fault kinematics and Rift Geometry of interacting segments:analogue models based on the Albertine Rift (Uganda),Western Branch-East African Rift System[J].Journal of African Earth Sciences,2011,59:18-184.
[11] Chorowicz J.The East African Rift System[J].Journal of African Earth Sciences,2005,43(1):379-410.
[12] 徐宁,张杰,史卜庆,等.红海盆地石油地质特征及其油气勘探潜力[J].地学前缘,2014,21(3):155-165.
[13] Bosworth W,Huchon P,Morley C K.The Red Sea and Gulf of Aden Basins[J].Journal of African Earth Sciences,2005,43:334-378.
[14] Macgregor D.History of the development of the East African Rift System:a series of interpreted maps through time[J].Journal of African Earth Sciences,2015,101:232-252.
[15] Africa Oil Corp.Moving forward to development[EB/OL].[2017].http://www.africaoilcorp.com/i/pdf/ Presentation-Oct-2017.pdf.
[16] Africa Oil Corp.A major emerging oil company in East Africa[EB/OL].[2018-10-13].http://www.africaoilcorp.com/i/pdf/Corporate_Presentation_January_2014.pdf.
[17] Morley C K.Evolution of large normal faults:evidence from seismic reflection data[C].AAPG Bulletin,2002,86(6):961-978.
[18] Neumaier M,Tiercelin J J,Nalpas T,et al.Basin analysis and petroleum systems modeling of the Lokichar Basin(Kenya)[C]//AAPG International Conference and Exhibition:The Spirit Between Continents:Energy Geosciences in a Changing World,Istambul,Turkey:AAPG,2014:1.
[19] Tiercelin J J,Potdevin J L,Morley C K,et al.Hydrocarbon potential of the Meso-Cenozoic Turkana Depression,northern Kenya:I Reservoirs:depositional environments,diagenetic characteristics,and source rock-reservoir relationships[J].Marine and Petroleum Geology,2004,21(1):41-62.
[20] Tiercelin J J,Thuo P,Potdevin J L,et al.Hydrocarbon prospectivity in Mesozoic and Early-Middle Cenozoic rift basins of central and northern Kenya,Eastern Africa[C]∥GAO Deng-liang.Tectonics and Sedimentation:Implications for Petroleum Systems.Tulsa:AAPG,2012:178-207.
[21] Morley C K,Karanja F M,Wescott W A,et al.Geology and geophysics of the Western Turkana Basins,Kenya[C]∥Morley C K.Geoscience of Rift Systems-Evolution of East Africa:AAPG Study 44.Tulsa:AAPG,1999:19-54.
[22] Talbot M R,Morley C K,Tiercelin J J,et al.Hydrocarbon potential of the Meso-Cenozoic Turkana Depression,northern Kenya:II Source rocks:quality,maturation,depositional environments and structural control[J].Marine and Petroleum Geology,2004,21(1):63-78.
[23] Tiercelin J J,Thuo P,Nalas T,et al.Hydrocarbon prospectivity in Mesozoic and Early Cenozoic rift basins in central and northern Kenya[C]//AAPG International Conference and Exhibition.Cape Town,South Africa:AAPG,2008:10.
[24] Africa Oil Corp.Moving forward to development[EB/OL].[2018-10-13].http://www.africaoilcorp.com/i/pdf/ Corporate-Presentation-Sept-2016.pdf.
[25] Rop B K,Patwardhan A M.Hydrocarbon of source rocks evaluation study of Lokichar Basin,northwestern Kenya[J].Journal of the Geological Society of India,2013,81(4):575-580.
[26] Rop B K.Hydrocarbon characteristics of source rocks in Loperot-1 well,NW Kenya[C]// Exploration & Production Geology.Nairobi,Kenya:AAPG,2011.
[27] 张燕,田作基,温志新,等.东非裂谷系东支油气成藏主控因素及勘探潜力[J].石油实验地质,2017,39(1):79-85.
[28] 赵伟,韩文明,胡滨,等.东非裂谷Albertine地堑石油地质条件和成藏规律[J].四川地质学报,2016,36(2):275-279.
[29] 蔡文杰,韩文明,许志刚,等.东非Lake Albert盆地构造调节带特征及其对油气成藏的控制作用[J].地质科技情报,2015,34(4):119-123.
[30] 周总瑛.我国东部断陷盆地石油排聚系数统计模型的建立[J].新疆石油地质,2009,30(1):9-12.
[31] 徐思煌,梁浩然,刘晓霞.生烃凹陷资源潜力快速评价新指标:烃源指数[J].地球科学与环境学报,2017,39(2):238-247.
[32] Tullow Oil plc.Erut-1 oil discovery in Kenya[EB/OL].[2018-10-18].https://www.tullowoil.com/Media/docs/ default-source/Media/Press-releaes/tullow-oil-plc---erut-1-well-result-(final).pdf?sfvrsn=0.
[33] Tullow Oil plc.Emekuya-1 oil discovery in Kenya[EB/OL].[2018-10-18].https://www.tullowoil.com/Media/ docs/default-source/Media/Press-releaes/tullow-oil-plc---emekuya-1-well-result.pdf?sfvrsn=2.
[34] Africa Oil Corp.Moving forward to development[EB/OL].[2018-11-12].http://www.africaoilcorp.com/ i/pdf/2017-09-05-CP.pdf.
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