RMZ – Materials and Geoenvironment, Vol. 58, No. 2, pp. 163–180, 2011 163 Sequence stratigraphic framework of K-field in part of Western Niger delta, Nigeria Sekvenčna stratigrafija naftnega polja K v zahodnem delu delte reke Niger, Nigerija M. e. nTon1,* & ToPe SHade oGUnGBeMi1 1University of Ibadan, Department of Geology, Ibadan, Nigeria *Corresponding author. E-mail: ntonme@yahoo.com Received: February 2, 2011 Accepted: July 8, 2011 Abstract: A sequence stratigraphic approach was applied to K-Field, within the western Niger Delta by integrating wireline logs of four wells; 001,003, 004 and 005; and high resolution biostratigraphic data of wells 001, 004 and well 005. The study is aimed at deducing key bounding surfaces, depositional sequences and their corresponding systems tracts as well as the palaeodepositional environment of the hydrocarbon bearing Agbada Formation in the study area. Two sequence boundaries at 8900 ft (2697 m) and 9050 ft (2742 m), and one maximum flooding surface at a depth of 7650 ft (2318 m) were recognized in well 5 and used to subdivide the stratigraphic suc- cession into depositional sequences and their corresponding systems tracts. Highstand and Transgressive systems tracts were recognized in each of the three depositional sequences. Marker shale, characterized by Chloguebelina 3 (16.0 Ma) was used to date the key bounding sur- faces with the aid of the Niger Delta chronostratigraphic chart as Ear- ly to Late Miocene. The Highstand systems tracts are characterized by shale-rich upward coarsening sands, having poor reservoir quality while the lowstand systems tracts are characterized by thick sandstone units, indicating good quality seals to reservoirs. From the SP logs motifs, the depositional environments inferred include tidal channel, shoreface and shelf environments which typify a marine depositional setting. Izvleček: Na podlagi karotažnih vrtin in detajlnih biostratigrafskih podatkov iz štirih vrtin (001, 003, 004 in 005) smo izdelali sekvenčno strati- Original scientific paper UNIVERSITY OF IBADAN LIBRARY 164 nTon, M. e., oGUnGBeMi, T. S. grafijo naftnega polja K v zahodnem delu delte reke Niger. Namen študije je bil določiti glavne mejne površine, depozicijske sekvence, sistemske trakte in okolje sedimentacije. Podatke smo analizirali s programsko opremo Petrel. V preučenih zaporedjih smo določili tri depozicijske sekvence, ki so ločene s sekvenčnimi mejami na globini 2697 m ter 2742 m. Za vsako izmed sekvenc smo določili transgresivne sistemske trakte (TST) in sistemske trakte visoke gladine morja (HST). Zgodnje- do poznomi- ocenska starost preučevanega zaporedja je bila določena na podlagi plasti kronostratigrafske lestvice delte Nigra in glinavcev s Chlogue- belino 3 (16.0 Ma). Sistemski trakti visoke gladine morja vsebujejo z glino bogate peske, ki so rezervoar slabše kvalitete. Transgresivni sis- temski trakti pa so sestavljeni iz debelih enot, ki so dobre zaporne pla- sti rezervoarja. Na podlagi SP-motivov iz vrtin smo določili naslednja sedimentacijska okolja: plimske kanale ter obalna in šelfna okolja. Key words: sequence stratigraphy, depositional environment, Niger Delta Ključne besede: sekvenčna stratigrafija, sedimentacijsko okolje, delta reke Niger Introduction basin as the main target. In order to sat- isfy the need for increasing production The Niger Delta is situated in the Gulf of the vast hydrocarbon resources, it of Guinea and extends throughout the was necessary to improve the existing Niger Delta province (KlEtt et al, geological knowledge of the region by 1997). The Niger Delta is a large arcu- application of a modern concept of se- ate type, situated on the west coast of quence stratigraphy. central Africa between latitudes 3o and 6o N and longitudes 5o and 8o E (REiJERS Sequence stratigraphy, which is the un- et al, 1997). It ranks among the world’s derlying concept for this work, is the most prolific petroleum producing Ter- study of the subdivision of sedimen- tiary deltas. This province contains one tary basin fills into genetic packages identified petroleum system known as bounded by unconformities and their the Tertiary Niger Delta (Akata-Ag- correlative conformities. The knowl- bada) petroleum system (EkweoZor & edge of sequence stratigraphy can pro- daUkorU, 1984: KUlke, 1995). vide a chronostratigraphic framework for the correlation and mapping of sed- Over 80 % of Nigeria’s revenue comes imentary facies and for stratigraphic from oil and gas, with the Niger Delta predictions. RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY Sequence stratigraphic framework of K-field in part of Western Niger delta, Nigeria 165 Present study therefore focuses on de- part of the Tertiary Niger Delta (Figure veloping sequence stratigraphic frame- 1). The K-Field, which contains four work for K-Field within the Niger wells used in this study, is within the Delta basin, based on the integration of Shell Petroleum Development Com- data from well logs and biostratigraph- pany of Nigeria concession (Figure 1). ic data sets. On the basis of sand-shale ratios, the subsurface Tertiary section of the Ni- Study area and regional geologic ger Delta is divided into three forma- setting tions (Figure 2), representing prograd- ing depositional facies. These forma- The study area is the K-Field, located tions are from oldest to youngest; Aka- in the onshore portion of the western ta, Agbada and Benin Formations. The Figure 1. Concession map of Niger Delta showing location of K-Field with base map of four wells shown. Map of Africa inset (Modified from ENI/ NAOC, 2002 Brochure on Nigeria RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY 166 nTon, M. e., oGUnGBeMi, T. S. Figure 2. Stratigraphic column showing the three Formations of the Niger Delta (DOUST & OMATSOLA, 1990) RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY Sequence stratigraphic framework of K-field in part of Western Niger delta, Nigeria 167 type sections of these formations are accumulated in delta-front, delta-tops- described in SHorT & STäUBle (1967) et, and fluvio-deltaic environments. In and summarized in a variety of papers the lower part of the Agbada Forma- (e. g. AvBoBvo, 1978; DoUST & oMa- tion, shale and sandstone beds were de- tola, 1990; KUlke, 1995). posited in equal proportions, however, the upper portion is mostly sand with The Akata Formation at the base of the only minor shale interbeds. The Benin delta, is of marine origin and is com- Formation is the youngest lithostrati- posed of thick shale sequences (poten- graphic succession in the Niger Delta tial source rock), turbidite sand (po- and comprised sandstone, grits, clay- tential reservoirs in deep water), and stone and streaks of lignite. It is about minor amounts of clay and silt. Begin- 2 000 m thick and ranges in age from ning in the Cretaceous in the proximal Oligocene in the proximal part of the part of the delta and Recent in the distal delta to Recent. The Benin Formation offshore, the Akata Formation formed consists of thick sections of continental within a deep water environment, when sediments with coastal plain and shal- terrestrial organic matter and clays low marine sandstones. The formation were transported to deep water areas water is fresh with high resistivity. characterized by low energy condi- tions and oxygen deficiency (STacHer, The structural development within the 1995). It is estimated that the formation Niger delta is controlled by differenti- is up to 7 000 m thick (DoUST & oMaT- al loading of the underlying prodelta Sola, 1990). The Akata Formation un- shales of the Akata Formation, which derlies the entire delta, and is typically consists of three basic elements; the overpressured. Turbidity currents likely northern (proximal) megastructure bo- deposited deep sea fan sands within the undary fault, a southern counter-regio- upper Akata Formation during the de- nal terminating fault and/or toe-thrust velopment of the delta (BUrke, 1972). belt and the intervening central rigid block between the two fault systems The Agbada Formation, which is the (EvaMy et al, 1978). Most known traps major petroleum-bearing unit, overlies in the Niger Delta are structural, al- the Akata Formation. The formation be- though stratigraphic traps are not un- gan in the Eocene in the proximal part common (Figure 3). The growth faults of the delta and presently deposited in which formed the structural traps de- the nearshore shelf domain. It consists veloped during synsedimentary defor- of paralic siliciclastics, over 3 700 m mation of the Agbada paralic sequence thick and represents the actual deltaic (EvaMy et al., 1978; STacHer, 1995). portion of the sequence. These clastics DoUST & oMaTSola (1990) described a RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY 168 nTon, M. e., oGUnGBeMi, T. S. variety of structural trapping elements, suggest probable hydrocarbon accumu- including those associated with simple lation at the downthrown side of the rollover structures; structures with mul- major growth fault. Schematic sketches tiple growth faults, structures with anti- showing the development of growth- thetic faults, and collapsed crest struc- fault-bounded depobelts during progra- tures. NTon & adeSina (2009) identi- dation of unstable Niger Delta clastics fied two major growth faults, three anti- have been presented in KnoX & oMaT- thetic and two synthetic faults, offshore Sola (1989). The formation of interest Niger Delta. They also noted structural is the Agbada Formation which con- closures as rollover anticlines displayed tains the hydrocarbon producing reser- on the time/depth structure maps which voirs in the study area. Figure 3. Examples of Niger Delta Oil Field Structure and associated trap types. (STACHER, 1995) RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY Sequence stratigraphic framework of K-field in part of Western Niger delta, Nigeria 169 Materials and Methods flooding surfaces and are recognized by an erosional surface between a low- A suite of well logs, in ASCII format , stand and a highstand system tract. were obtained from four wells namely; 001, 003, 004, and 005, drilled within Recognition of Maximum Flooding the K- Field in the western Niger Delta. Surfaces Biostratigraphy data, summarized with The Maximum Flooding Surface Pollen(P) and Foram(F) zones from caps the Transgressive System Tracts three wells notably; 001, 004, and 005 (TST). It represents the most landward plus deviation data were utilised in this transgression of the shoreline. The 3rd study. The above dataset were obtained order MFS identifiable in the Niger from the Shell Petroleum Development delta chronostratigraphic chart where Company of Nigeria Limited. The well mapped on the wells. It was identified logs, made of the gamma ray, self po- through the biostratigraphic data made tential and resistivity logs were anal- available and interpreted. When inte- ysed using the PETREL software (ver- grated with the biostratigraphic inter- sion 2003) at the workstation of the De- pretation, it is also represented on the partment of Geophysics, Federal Uni- well log as the point where the resisti- versity of Technology, Akure, Nigeria. vity logs which corresponds to the hig- hest value on the SP logs. A detailed analysis and interpretation of the suite of well logs was carried Recognition of Systems Tracts out, followed by biostratigraphic in- This was recognized by first locating terpretation of the data. The various the3rd order and 4th order maximum flo- analyses were integrated and interpre- oding sufaces within major condensed ted to deduce a sequence stratigraphic sections on the logs, followed by the framework of the Field of study. Detai- location of the highstand system trac- led analytical procedures are documen- ts, transgressive system tract and the ted in oGUnGBeMi (2009). lowstand system tract subdividing. The Lowstand System Tract comprises the Recognition of Sequence Boundaries basin floor fan, the slope fan and the The recognition of sequence boundari- prograding complex. The basin floor es (SB) in this study was based on the sands contain massive turbidite sands concept of van waGoner et al. (1990). with the upper boundary characterized The sequence boundaries were identi- by hemipelagic shale (Vail et al., 1992). fied by a sand-rich facies, within a co- The slope fan consists of crescent-sha- arsening upward sequence. These are ped channel bank units while the, pro- usually located between two maximum grading complex is a prograding unit RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY 170 nTon, M. e., oGUnGBeMi, T. S. with an aggradational offlap configura- ved search for hydrocarbon in the stu- tion. It rests directly on the underlying dy area as shown below. slope fan and basin floor complexes and is characteriesed by turbidities san- Lithology and Depositional Energy ds and shales. A maximum shale point This study revealed that low SP log generally marks the boundary between readings, ranging from 82.4 mv to the slope fan complex and the lowstand 173.7 mv, are good reservoir quality prograding complex. The Trangressive sandstones while SP log reading rang- System Tract is characterized by elec- ing between 44.3 mv and 82.4 mv, indi- trofacies that is made up of high gam- cates shale interval (Figure 4). This was ma ray values indicating the presence used in the identification of the sand– of deep sea marine shale. The portion shale ratio which aided in interpreting of the log with the lowest resistivity sandstone and shaly lithologies. These was selected as the maximum flooding sandy lithologies were painted yellow, surface when integrated with the bio- shaly lithologies were painted green and stratigraphic data. This is based on the self potential logs were painted red for concept of SanGree et al., (1990). easy identification (Figure 4). Most of the sandstone units within the field have The Highstand System Tract is bo- some shale intercalations as seen mostly unded below by a downlap surface on the upper part of the study interval. of maximum flooding and above by a The thickness for the small reservoirs sequence boundary. According to Vail ranges between 15 m and 20 m while et al., (1990), log correlations in the the very thick sandstone units range be- highstand commonly indicate interbed- tween 76 m and 305 m (Figure 4). ded sand and shale lithofacies while the reservoir continuity is fair. The depositional energy trend, which is useful for the identification of sedi- mentary facies (PoSaMenTier & vail, Results and discussion 1988), follows two sequences in this study. These are; those with finning up- Based on integration of the available ward and coarsening upward sequences data, the lithologic, depositional ener- (Figures 4 and 5). Those with fining up- gy, stratigraphic surfaces and sequence ward sequences are seen to have lesser stratigraphy of the field were analyzed thicknesses. This forms the lithologic and interpreted. These interpretations classification indicating the building up aided in the subdivision of stratigraphy of sandstone from coarse to fine grains, into system tracts that aided in better with the coarse grains pointing to hig- correlation of the wells for an impro- her energy of deposition while the finer RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY Sequence stratigraphic framework of K-field in part of Western Niger delta, Nigeria 171 Stratigraphic Cross Section of wells 005, 003, 001 and 004:Equally Spaced Logs Datum : SSTVD Vertical scale = 1 in per 50 ft 08/08/2008 Figure 4. Correlation panels and depositional energy trends based on wells 005, 003, 001 and 004 RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY 172 nTon, M. e., oGUnGBeMi, T. S. Stratigraphic Cross Section “Well005.003,001and 004:Equally spaced logs Datum : SSTVD Vertical Scale= 1 in per 50ft 08/08/2008 Figure 5. Log trends for depositional environment using Wells 005 and 003 RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY Sequence stratigraphic framework of K-field in part of Western Niger delta, Nigeria 173 grains indicate a lower energy of depo- clastic sediments at a constant sea level sition. The coarsening upward sequen- leading to an aggrading sediment depo- ces show a larger thickness of deposits, sition. The box car-shaped SP log indi- decreasing from sandstone at the top to cates the truncation of a rapid aggrada- shale at the base (Figure 5). tional deposition with terminal bounda- ries. They can be inferred to as distribu- SP logs analysis in the studied interval tary channel sands. According to Selley show three types of log motifs, which (1991), three general categories of envi- are; funnel-shaped, bell-shaped and box ronments can be inferred from such de- car-shaped (Figure 5). The funnel–sha- positions; these are tidal channel sand, ped motif is that which has been identi- fluvial channel sand delta distributaries fied as upward-coarsening sedimentary channel sands. It can be deduced from sequences (Figure 5). These sedimen- this study therefore that the box-car de- tary sequences would be inferred to be positional motif is significant of distri- a prograding complex deposited within butary channel sand deposited within a a lowstand system tract. They are in- shallow marine environment. terpreted as fluvial channel deposited within a continental to coastal enviro- Third order stratigraphic surfaces nment (Figure 5). These sequences have and sequences lesser thickness than others, ranging be- The sequence stratigraphic framework tween 39 ft to 41 ft (11.8 m to 12.4 m). for K Field is composed of three ma- jor third(3rd) order Sequence Boundar- In the bell-shaped motif, the SP logs of ies (SB) ranging from 15.9 Ma to 10.4 the study interval have a bell motif over- Ma and one major third (3rd) order se- lain and underlain by thick shales. They quence of Miocene age, correspond- are seen to have upwards fining sedi- ing to Pollen zones P680 to P780 and mentary sequences (Figure 5) with thic- Foram zones of F9300 to F9800 (Table knesses ranging from 500 ft to 970 ft 1). The maximum flooding surface was (152 m to 294 m).This occurs when ma- tied to the Niger Delta Chronostrati- rine sediments such as shales transgress graphic chart (Figure 6) over continental facies or fluvial sedi- ments. They could also be interpreted Maximum Flooding Surface (MFS) as tidal channel sands deposited under A major third order MFS was identi- high tidal influence over fluvial sands. fied, and subsequent four fourth order Maximum Flooding Surfaces (Figure The box car-shaped SP log is a convex 7). The MFS identified was based on (outward) view with a box description. the positions of highest abundance and The motif is formed due to a build up of diversity peaks, on the biofacies data. RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY 174 nTon, M. e., oGUnGBeMi, T. S. Figure 6. Niger Delta chronostratgraphic chart (HAQ et al, 1988) RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY Sequence stratigraphic framework of K-field in part of Western Niger delta, Nigeria 175 On the well logs, they were identified which correspond to the lowest value as the flooding surface with the highest on the SP log indicates the sequence resistivity values. This correctly ties boundaries mapped (Figure 7) with the MFS identified at a depth of 7 650 ft (2 318 m). 17.7 Ma SB This is the oldest sequence boundary Chloguebelina 3 MFS (16.0 Ma). identified in the K-Field. It is penetrat- This MFS penetrated in the studied ed by Wells 005 and 003 at depths of 9 Field has been tied to the Chloguebe- 050 ft (2 758 m) and 8 950 ft (2 722 m) lina-3 marker on the Niger Delta Chro- respectively. This surface was not rec- nostratigraphic chart (Figure 6). They ognized on well 001 due to the depth in were encountered by Wells 003 and which it was drilled to. This was iden- 005 at respective depths of 7 850ft (2 tified from the well logs with the aid of 379 m) and 7 650ft (2 318 m) based on the biostratigraphic data (Table 1) well log interpretation. It occurs with the P680 and F9300 biozones. The Deductions from biofacies interpreta- log patterns show an upward coasen- tions typically show that such horizons ing depositional energy succession and are devoid of Pollens, with no indica- downward finning sedimentation with tion of Foraminifera. The depositional a laterally extensive shaly lithology. environment deduced from the log sig- natures depicts a continental sediment Sequence Boundaries (SB) deposited in a shelf environment (Fig- The sequence boundaries were identi- ure 5) based on the concept of BUScH fied based on the interpretation of para- et al., (1974). sequence stacking patterns, log shapes and motifs. The third order sequence 10.38 Ma SB boundaries recognized are 15.9 Ma and This is the second sequence boundary 10.38 Ma (Figure 6). Resistivity logs penetrated in K-Field and it marks the Table 1. Biostratigraphic data table Well Depth (ft) Marker shales’s (Faunal bed) Dated Age(ma) P Zones F Zones Epochs 1 6180 Nonion 6 10.3 P780 F9800 Miocene 76.75 Chloguembelina 3 16.0 P680 F9300 Miocene 4 6400 Nonion 6 9.0 P820 F9800 Miocene 7550 Chloguembelina 3 16.0 P680 F9300 Miocene 3 9000 Rich Bolivina 25 17.7 P670 F9300 Miocene10010 Rich Bolivina 25 17.7 P670 9300 Miocene 5 6080 Nonion 6 10.3 P780 F9800 Miocene7701 Chloguembelina 3 16.0 P680 F9300 Miocene RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY 176 nTon, M. e., oGUnGBeMi, T. S. Stratigraphic Cross Section “Well005.003,001and 004:Equally spaced logs Datum : SSTVD Vertical Scale= 1 in per 50ft 18/08/2008 Figure 7. Sequence stratigraphic correlation and depositional environment setting of K-Field showing Wells 005 and 003 RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY Sequence stratigraphic framework of K-field in part of Western Niger delta, Nigeria 177 base of the Benin Formation. It was tems tract starts from the top of TST1 at penetrated by Wells 005 and 003 at depth 7 450 ft (2 257.6 m) to 6 950 ft (2 depths 7 000 ft (2 134 m) and 7 300 ft (2 106 m). This systems tract terminates at 225 m) respectively. This sequence has the 10.38 Ma Sequence Boundary. a blocky log shape which is depicted on the SP log (Figure 5) and indicates Well 005 a channel sand deposit (SERRa, 1985). The first sequence in this well started This is well correlated to the Niger Del- from the base of the well and ends at ta chronostratigraphic chart (Figure 6). 8 945 ft (2 710.6 m) (Figure 7). This is capped by high system tract. The second Description of the third order de- sequence in this well starts at the depth positonal sequences of wells of 8 985 ft (2 723 m) and the depositional Sequence stratigraphic model devel- episode commenced with the deposition oped for K-Field was based on the in- of Trangressive Systems Tracts. These terpretation carried out on Wells 003 lie unconformably on the lower bound- and 005 that penetrated different sub- ary, culminating in the Transgressive surface lithologies. Figures 4, 5 and 7 peak at the Maximum Flooding Surface show the representation of the interpre- with lowest shale resistivity and high tation of the wells. value on the SP log at a depth of 7 550 ft (2 294.8 m). This in turn initiated the Well 003 blocky sand of the the Highstand Sys- The sequence 1 of this well ends at 8 575 tems Tract, which extends from the top ft (2 598.5 m) (Figure 7) and is capped of the Maximum Flooding Surface and by the Highstand Systems Tract. Se- terminates at 6 950 ft (2 112.5 m) and (2 quence 2 of this well starts with a cre- 226.7 m), at a position which marks the sent shaped log pattern , which grades end of the second sequence boundary. into a prograding complex. The basal unit starts at a depth of 9 055 ft and Depositional environment ends at 7 000 ft. It is bounded below by The depositional environments were the shallow marine deposits (Figure 7) delineated based on SP log signatures. which marks the base of this Sequence Depositional environments delineated Boundary. The Transgressive system in this study include the tidal channel tract covers a total depth of about 1 055 complex and the shelf environment ft (320 m) as it exihibits an aggrada- (Figure 7). The blocky shaped pat- tional parasequence set terminated at tern is characteristic of the distributary the top by the major condensed section channel sediments deposited in a shal- embedded in the 16.0 Ma Maximum low marine environment (Figure 5). Flooding Surface.The Highstand sys- This corroborates the findings of SER- RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY 178 nTon, M. e., oGUnGBeMi, T. S. Ra, (1985) This signature is represented shapes/trends, pollen and foram zones by a kick to the left of the SP baseline. data which were utilized independen- Flooding surfaces, identified with ma- tly and later integrated with well logs rine shales, can be recognized below as to within a chronostratigraphic frame- a large right kick on the SP log (Figure work for the field. 7). This significant signature typifies the shelf environment. The inner shore- Two sequence boundaries at 8 900 ft face environment is marked generally (2 697 m) and 9 050 ft (2 742.4 m), by an upward decrease in shale content and one maximum flooding surface at from the proximal to the distal portion a depth of 7 650 ft (2 318.2 m) were of the field. This corroborates the find- recognized in well 5 and utilized to ings of WilliS & BenneTT, (1994). subdivide the stratigraphic succes- sion into depositional sequences and A typical model constructed for the their corresponding systems tracts. Field was done using Well 005 (Figure Highstand and Transgressive systems 7). It shows that the deposited sequen- tracts were recognized in each of the ce starts with a tidal channel enviro- three depositional sequences. Marker nment, with an interfingering of san- shale, characterized by Chloguebelina dy sediments which is capped by the 3 (16.0 Ma) was used to date the key Transgressive system tract with marine bounding surfaces with the aid of the shale marking the maximum flooding Niger Delta chronostratigraphic chart surface which also hosts the condensed as Early to Late Miocene. section. This sequence change into sho- reface environment having sand bodies The Highstand systems tracts are char- at the base. This typifies the concept acterized by shale-rich upward coarsen- described by EMery et al., (1996) Sub- ing sands, having poor reservoir quality, sequently, the next sequence recogni- while the transgressive systems tracts zed starts with a fluvial channel sand are characterized by thick sandy shale body, characterized by some extensive units, indicating good quality seals to marine shale deposits (Figure 7). reservoirs. Arising from the SP logs motifs, the depositional environments inferred include tidal channel, shore- SuMMary and conclusion face and shelf environments, typical of shallow marine depositional setting. The concept of sequence stratigraphy was applied to the K-field, within the This model will therefore serve as a gu- western Niger Delta, Nigeria. This was ide to the development of K-field and based on biofacies analysis, well log assist in further exploration activity. RMZ-M&G 2011, 58 UNIVERSITY OF IBADAN LIBRARY Sequence stratigraphic framework of K-field in part of Western Niger delta, Nigeria 179 Acknowledgments can Association of Petroleum Ge- ologists, p. 239–248. The authors are grateful to the manage- ekweoZor, c. M. & daUkorU, e. M. ment and staff of the Shell Petroleum (1984): Petroleum source bed Nigeria Limited, for the provision of evaluation of Tertiary Niger Del- data. We are grateful for the invaluable ta--reply: American Association assistance of the Department of Ap- of Petroleum Geologists Bulletin, plied Geophysics, Federal University v. 68, p. 390–394. of Technology, Akure, Nigeria, for the evaMy, B. d., HareMBoUre, j., kaMer- permission to use their Petrel Work sta- linG, P., knaaP, w. a., Molloy, F. a. & rowlandS, P. H. (1978): Hy- tion for the data analysis. I appreciate drocarbon habitat of Tertiary Ni- the encouragement of my colleagues, ger Delta: American Association Prof. A. A. Elueze and Dr. M. 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