MINISTRY OF EDUCATION AND TRAINING HA NOI UNIVERSITY OF MINING AND GEOLOGY ____________________ TRAN CHAU GIANG CHARACTERIZATION OF THE CENOZOIC PETROLEUM SYSTEM IN THE NORTHEASTERN OFFSHORE SONG HONG BASIN Subject area: Engineering geology Code: 62.52.05.01 SUMMARY OF DOCTORAL THESIS WORK HANOI -2014 The thesis work has been completed at: Ha Noi University of Mining and Geology Principal Advisors: 1) Professor, Doctor of Science. Mai Thanh Tan 2) Dr. Le Tuan Viet Judge 1: Associate Professor, Doctor. Pham Huy Tien Judge 2: Dr. Nguyen Huy Quy Judge 3: Dr. Cu Minh Hoang The doctoral thesis work will be defend at the University Council of Scoring Thesis Meeting at the Hanoi University of Mining and Geology at …….hour, day ……., month……year …… You can find out the thesis in the libraries: National Library, Hanoi or Library of Ha noi University of Mining and Geology 1 INTRODUCTION The necessity Song Hong Basin is complex sedimentary basin, including several tectonic elements with different oil and gas potential. The VPI- IDENMITSU (2005-2007) project has confirmed non-marine dual petroleum system (lacustrine and fluvio-deltaic) in the Song Hong basin by advanced geochemical analysis. Due to no oil – source rock correlation, the characterization of petroleum system in the Northeastern offshore Song Hong basin has yet to be confirmed. In 2008, the oil discovery by 106-HR-1X has proven the hydrocarbon potential of the Pre- Cenozoic carbonate basement Play. Next well 106-HR-2X was drilled through the oil reservoir bearing in the Pre – Cenozoic carbonate basement and penetrated a thick shale. It is a questionable that this Pre- Cenozoic shale is a new source rock. Well 107-PL-1X drilled in 2013 in the rich organic source area, and has the same structural trend as 106-HR prospects. However the well was dry. Other latest exploration wells have discovered gas condensate with heavy H 2 S and CO 2 polluted in the reservoir fluid. These facts show many issues have to resolved such as the quality and distribution of source rocks, or which risk factor of geological parameters in the petroleum system have affected the results of exploration in the area of Northeastern (NE) offshore Song Hong basin. Therefore, the topic "Characterization of the Cenozoic petroleum system in the Northeastern offshore Song Hong Basin" was chosen with the objectives and research tasks are as follows: Objectives: 2 - To get better understand about the characterization and area distribution of petroleum source rocks of Cenozoic sediments in the NE offshore Song Hong Basin. - Contribute to improve the methodology for petroleum systems evaluation and risk analysis in exploration. Tasks: - Integrate geological data and geophysical data to clarify the regional geological setting. - Research to clarify the characterization and level of maturity and timing of HC generation and migration, identify the origin oil generated source rock in the NE offshore Song Hong Basin. - Determine the area distribution of source rocks and HC potential areas. Object and scope of the study: The scope of the study include the block 106 area, Northwestern of block 102 and North part of block 107 offshore Song Hong basin that separated to others area by Song Lo fault. The objective to study is Cenozoic petroleum system. Thesis protection: Thesis 1. Study results of the geochemical characterization identified a lacustrine petroleum system related to the Oligocene source rock exist in the NE offshore Song Hong Basin. The source rock contains moderate to good organic richness, kerogen type II and mixed type II/ III, locates in the grabens and half grabens within the study area. Based on all available geochemical data of the Miocene shale and Pre- Cenozoic shale that identifies these shales are not qualified to be a source rock. 3 Thesis 2. Based on the study of factors impact on risk of the petroleum system such the origin, maturity, the Oligocene sediment thickness and the distribution of potential prospects, restore the geological development through the ages that are enable to identify the Thuy Nguyen graben has lowest exploration risk. Next is the Kien An graben. The South Bach Long Vi Island area and NW edge of block 102 are the areas of high exploration risk. New findings of the thesis work: - Based on latest exploration data, results of thesis work has contributed accurately geochemical characteistics of the NE offshore Song Hong basin. The Pre- Cenozoic shale below the carbonate layer bearing oil has terrestrial lithoface, deposites under oxidizing condition environment, with poor organic contain that is not qualified to be a source rock. - The new structural maps were built have contribution to get better understand of Late Oligocene inversion event affect oil and gas potential of the area of Northeatern Offshore Song Hong basin. The scientific and practical contributions: * Scientific contribution: The results of research allowed identify the characterizations and the distribution of source rock to get better understand of petroleum system in NE of Song Hong basin, offshore Vietnam. * Practical contribution: Contribute to improve the effectiveness of HC potential assessment for the NE of Song Hong basin, and to serve the Oil companies in the exploration and exploitation activities. The layout of the thesis: The thesis consists of 04 chapters excluding the introduction and conclusions, recommendations, papers publication and reference 4 lists. The entire content of the thesis is presented in 135 pages, 24 tables and 89 figures. Chapter 1 SUMMARY GEOLOGICAL STRUCTURE IN THE NORTHEAST AREA OFFSHORE SONG HONG BASIN 1.1. Overview the geology of study area 1.1.1. Location Study location is part of Northeast Song Lo fault offshore Song Hong basin. Water depth from 30-40m. (fig.1.1) 1.1.2. Exploration history Fisrt exploration work began in 1978. In 1988, first PSC was signed for block 106, and a part of block 102, 103 and 107 between PVN and TOTAL. In 1992, IDEMITSU – PVN signed a PSC for block 102/91. Next the blocks 102 – 106 with total area of 10700 km 2 was signed between PVN and ATI Petroleum Inc in 2000. Recently, this PSC has relinquished area and maintained in area of 225 km 2 . The remaining area now is Fig. 1.1: Structural map of Top basement Song Hong basin and study area location (N.T.Dau. et al, 2012) block 102/10 and block 106/10 with PVEP operator. From 1990 to present, in the study area were acquired more than 15,000 km of 2D, 5 and over 3000 km 2 of 3D seismic, more than 10 exploration wells. Several studies are available as Geochemical model of Song Hong Basin (N.T Dau, L.V Hien, 1997), Outcroup study in Bach Long Vi island, Do Son, Kien An, Elephant Mountain, and Cat Ba Island (P.Q Trung, 1998), Investigate the amount of HC generated and migrated from source rock to trap in the Song Hong basin by SIGMA 2D and BSS softwares (N.T.B Ha, 2010), Final Report on the analysis and modeling Song Hong Basin (VPI - GEUS, 2001), Report on Characterization of petroleum systems in the Song Hong Basin by State of the art Geochemical Technology (VPI-IDENMITSU, 2007). 1.2. Regional setting 1.2.1 Lithostratigraphy Song Hong Basin stratigraphic units consist of: (i) Pre-Cenozoic basement; (ii) Phu Tien Formation (E 2 pt); (iii) Dinh Cao Formation (E 2 đc); (iv) Phong Chau Formation (N 1 1 pc); (v) Phu Cu Formation (N 1 2 pc); (vi)Tien Hung Formation (N 1 3 th); (vii) Vinh Bao Formation; (viii) Formation of Hai Duong - Kien Xuong (N 2 -Q) (Figure 1.2). 1.2.2 Tectono-structure There exist in the study area 02 fault systems. The NW-SE and NE-SW fault systems. Fig.1. 2: Stratigraphic column of the offshore Northeast S.Hong basin (After N.T.Dau et.al, 2012) 6 These fault systems created structural type of dipping down to the basin center and formed a series of grabens alternate half grabens. The identified structural zonnation (Figure 1.3): Hai Phong Shelf: The shelf located in the northeastern part of the study area, covers a large area of the block 106 and block 101. Thanh Nghe undifferentiated monocline: It is located Fig.1. 3: Fault systems and structural zonnation to the West of the Song Chay fault. Central trough: can be subdivided as a) Miocene Inversion Zone b) Dong Quan trough North-East differentiated monocline: mades up of grabens, half grabens, horsts, and basement uplifts. Detaily consists of: a) Kien An Graben b) Tien Lang - Chí Linh horst c) Thuy Nguyen half graben d) Trang Kenh Nose e) Western Bach Long Vi trough f) Yen Tu Horst g) Southern Bach Long Vi trough Tectonic evolution was constructed based on restoration cross sections. The study results show the similarities and differences over the period of development of the region on the two banks of Song Lo 7 Fault. In Paleocene-Eocene to the Early Oligocene and Pliocene – Quaternary period are similar but different in period from late Oligocene to late Miocene. 1.3. Data base The documents use in thesis work are more than 15000 km 2D seismic, gravity maps of the Bac Bo Gulf, Vietnam geological maps, well logs and obtained rock samples were analyzed for the Petrography, Geochemistry, and Biostratigraphy studies. Especially with 500 m of core samples from Enreca – 3 well in Bach Long Vi island to study sedimentary, litho-facies, and geochemistry of Oligocene sediment. Chapter 2 RESEARCH METHODS 2.1. Petroleum system and its role in oil and gas exploration Petroleum system concept appears too many different definitions. The term “system” includes source rock and reservoir rock, oil - source correlation are considered a key factor in determining system (Dow W.G, 1972). Synthesis of the concept put forward by many authors, petroleum system is understood as a natural system where exist generated petroleum source rocks with all the geological elements and geological processes related to the ability to accumulate oil and gas may occur. In 1988, L.B Magoon had established a system classification, which distinguishes the petroleum systems to sedimentary basins, Plays and Prospects. Depend on the level of research, petroleum system is evaluated as an overview to detail as scale of a country, sedimentary basin, a play and to each independent prospect. The basic methods of assessment can be summarized as follows: 8 + Analysis petroleum system was evaluated on the basis of the total volume of HC generated/rock volume by Exxon. + Analysis petroleum system was evaluated on the prediction of petroleum geology characteristic (Delphi method), mainly based on the experience of experts. + Analysis petroleum system was evaluated on Geochemical material balance based on the calculation of the amount of oil and gas generated from source rock, as well as oil and gas were migrated and can accumulate in the trap. + Analysis petroleum system was evaluated on extrapolation of production history. + Analysis petroleum system by Play fairway analysis (based on geological model and statistical data) allows determine the change of the geological factors related to the oil and gas accumulation in an considered region. Figure 2.1: Play concept [CCOP, 2000] In the thesis work, Play assessment is applied to solve remaining problems in petroleum system in the study area. 2.2. The geochemical methodology Complex sets of geochemical index in evaluating the capacity of HC generation of sediments used in the thesis are: + Combust a crushed sample of rock at 600ºC + Pyrolysis method Rock-Eval standards (RE) + Bitumen extraction method + Chromatography (GC) + Mass spectrometry analysis (GC-MS) [...]... Area of basement structures less than 10 10 km2 with their relief from 200400m 4.2.5 Timing of HC generation, migration and trap formation The system Northeast petroleum of the offshore Song Hong basin is summary 4.1 in table Table 4.1: Petroleum system chart of the Northeast offshore Song Hong basin 22 4.3 Risk assessment and potential zonnation The results of seismic interpretation and mapping represent... estimate the chance of success in term Fig.4.3: Potential zonnation of carbonate 23 of geology, and predicte basement Play in the NE Song Hong the entirely change or basin partly change of geological factors in the a petroleum system of Northeast offshore Song Hong basin Figure 4.3 presents the potential zonnations of the study area CONCLUSIONS AND RECOMMENDATIONS The study results allows to point out some... rock includes: i) P1a: Probability of existence of reservoir facies; ii) P1b: Probability of effectiveness of the reservoir P2: The probability of the presence of a trap includes: i) P2a the probability of presence of the mapped structure and ii) P2b the probability of effective seal mechanism for the mapped structure P3: The probability factor for the petroleum charge system includes: i) P3a the probability... observed in the small troughs in the NE Song Lo fault and the Southern part of Bach Long Vi Island The structural maps of Top Basement, Top U400, Top U300 and the isopach map of Oligocen in scale 1/200.000 were built The isopach maps of Lower Oligocene (U400-Bsmt) and Oligocene (U300-Bsmt) (Figures 4.1 and 4.2) represent the distribution area of Oligocene significant altenated in the offshore Northeast Song. .. parameter is defined rely on subjective knowledge, extrapolation from the analysis geological and statistical data Following the guidance of CCOP, for example, the tables 2.1 and 2.2 describe the probabilities of P1a and P1b parameters Chapter 3 CHARACTERIZATION OF SOURCE ROCK IN THE OFFSHORE NORTHEAST SONG HONG BASIN 3.1 Organic richness in source rock + Pre -Cenozoic sediments: very poor in organic matter... for timing factor of 24 HC migration and trap formation and is not convenient for petroleum system in the study area - Based on the study results of source rocks maturity, HC migration and other parameters of the petroleum system have allowed effectively application of probabilistic method in risk assement, and established map of potential zonnation for northeast offshore Song Hong Basin Results are enable... risk analysis in the study area The analysis is performed on the assessment of the involved geological processes and the facts of geological time Geological processes are firstly started with the formation of the reservoir rock, next is the formation of a closed trap in relation to the maturity of source rock, HC migration from source rocks to reservoir rocks, the accumulation of HC in the trap and... Northeast Song Hong basin Figure 4.1 shows at the end of Early Oligocene time, 02 closed lakes systems trending NE-SW and NWSE were developed in the study area The basement hosts within Ham Rong field area as boundary separate the lakes In the Northern part of block 107, which is belong to South Bach Long Vi trough also has a deep lake The lakes in Southeast edge of block 106 and North of block 107 tend... favorable condition for carbonate development of along the evaporation zone of lakes The exploration wells in the study area have penetrated thin limestone in the Oligocene Theoryly, the H2S and CO2 pollution in the oil reservoir in the Ham Rong fields were the product of thermal sulfate reduction process (of CaSO4) in carbonate rocks explained by Angler-Gofer Scheme formula: CaSO4 + CH4 = CaS + CO2 + 2H2O... accurately determine the absolute age and geological model of the study area 5) Futher research on stratigraphic traps to accurately HC potential of Northeast offshore Song Hong Basin 6) Re-process seismic data in combination with available data of blocks 102-106, MVHN02, blocks 103-107, and 100-101/ 4 in order to improve the effectiveness of risk assessment for the whole area 25 LIST OF SCIENTIFIC WORKS . results of exploration in the area of Northeastern (NE) offshore Song Hong basin. Therefore, the topic " ;Characterization of the Cenozoic petroleum system in the Northeastern offshore Song Hong. fluvio-deltaic) in the Song Hong basin by advanced geochemical analysis. Due to no oil – source rock correlation, the characterization of petroleum system in the Northeastern offshore Song Hong basin has. STRUCTURE IN THE NORTHEAST AREA OFFSHORE SONG HONG BASIN 1.1. Overview the geology of study area 1.1.1. Location Study location is part of Northeast Song Lo fault offshore Song Hong basin. Water