Onshore Niger Delta Research Articles

Petrophysical Evaluation and Depositional Environments of Reservoir Sands in an Oil Producing Field, Onshore Niger Delta, Nigeria

Optimal hydrocarbon recovery depends strongly on predicting the reservoir quality and reservoir drive mechanism, and this could be achieved by petrophysical analysis. This research evaluated the petrophysical properties of reservoir sands in an Oil producing Field, onshore Niger delta, Nigeria using petrophysical techniques. Results from the Petrophysical evaluation, showed that the average porosity values of the reservoirs ranged between 0.15 and 0.24 while average water saturation for the three reservoirs ranged from 19% to 44%. Reservoir D_3000 has the largest accumulation of about 952 MMSTB while reservoir D_1000 gave the least accumulation of about 727MMSTB. The environment of deposition was interpreted using gamma-ray log motif. Reservoir D_1000 shows a blocky gamma ray motif that suggests deposition from a steady energy, which can likely be a channel deposits. Reservoir D_2000 sands showed an obvious funnel shape gamma ray log motif by it coarsening upward attribute, which can likely be interpreted as a shore face environment. Reservoir D_3000 is the deepest and the thickest of the three reservoir sands, the gamma ray log motif displayed a blocky shape which can likely be interpreted as bar deposits and channel sands. This study reveals that Channel Sands, Bars and Shore face are good sites for exploration and production of hydrocarbon.

Reservoir Characterization using Petrophysical Evaluation of W-Field, Onshore Niger Delta

Reservoir characterization of W-field, onshore Niger Delta was carried out using petrophysical evaluation of well logs. Three reservoir sand intervals (A, B, C) were identified and correlated across four wells (W1, W2, W3, W4) in W-field using the gamma ray, while the fluid identification of each reservoir was achieved using the resistivity log. The reservoir C interval was selected and utilized for petrophysical interpretation was penetrated at depths 11741-11945ft, 11933-12173ft, 11658-11847ft and 11926-12095ft across all wells respectively.The average values of gross thickness, volume of shale, effective porosity, total porosity, permeability, water saturation and hydrocarbon saturation of the delineated reservoir sand are 200.5ft for gross thickness, 18% for shale volume, 21% for effective porosity, 26% for total porosity, 1071.74mD for permeability, and 28% for water saturation and 77% for hydrocarbon saturation. Petrophysical evaluation revealed that porosity and permeability are very good to excellent in the field. The reservoir is classed as clean sands based on the high net to gross ratio (>70%) and the low shale volumes (<30%). Consequently, the low value of shale volume, low value water saturation, high value of hydrocarbon saturation and the good porosity and permeability properties of the reservoir of interest suggest economical and commercial quality and viability of the wells within this field.

Facies Analysis and Paleoenvironmental Reconstruction of Well X, Onshore Niger Delta, Nigeria

Biofacies and lithofacies analysis of one hundred and ninety-two (192) ditch cutting rock samples from well x, onshore Niger Delta was carried out for the purpose of the paleoenvironmental reconstruction of the rock succession. The objectives were to identify the lithofacies units and species of foraminifera and to use both quantitave and qualitative foraminiferal assemblage to recognise the benthonic foraminiferal biofacies and integrate both results for delineation of paleobathymetric and paleoenvironmental settings of sediments penetrated by well x interval studied. The rock samples were prepared through wet-sieve analysis with 63µm mesh sieve size, and subsequently through dry-sieve analysis with 250µm and 500µm mesh sieve sizes. The prepared rock samples were analyzed to generate data for sedimentological grain-size analysis and foraminifera biofacies assemblages. The grain-size analysis provided lithofacies associations, sand/shale ratio and sorting/gradational profile for the studied intervals of well-x while the micropaleontological analysis identified a total of ninety-three (93) well preserved foraminiferal species from which three (3) biofacies associations were delineated. The biofacies include: Ammonia beccarii, Ammonia beccarii/Bolivina scalprata miocenica, and Haplophragmoides compressa/ Valvulina flexilis biofacies indicating Shallow Inner Neritic, Inner- Middle Neritic, and Outer Neritic – Upper Bathyal paleoenvironment respectively. The result of the sand/shale ratio and lithofacies associations indicated penetration into the Agbada Formation of the Niger delta and deposition within shallow to deep marine paleoenvironmental settings, predominantly as channels, intercalated with overbank and distal bar/bay deposits. Synthesis of the biofacies and lithofacies indicated stratigraphic development between coastal deltaic and upper bathyal paleowater depths.

Seismic Attributes for Enhanced Structural and Stratigraphic Interpretation in Onshore Fuba field, Niger Delta, Nigeria

Seismic attributes for enhanced structural and stratigraphic interpretation of Fuba Field, Onshore Niger Delta, Nigeria using Well-log and 3D Seismic data are here presented. Well-to-Seismic ties, faults and horizon mapping, time-surface generation, depth conversion and seismic attributes generation were carried out using Petrel software. The structural interpretation of seismic data reveal highly synthetic and antithetic faults which are in line with faults trends identified in the Niger Delta. Of the 29 interpreted faults, only synthetic and antithetic faults are regional, running from the top to bottom across the field. These faults play significant roles in trap formation at the upper, middle and lower sections of the field. Two distinct horizons were mapped. Fault and horizon interpretation reveal closures which are collapsed crestal structures bounded by these two major faults. The depth structure maps reveal anticlinal faults. Reservoirs are found at a shallower depth from 6500 to 7500ft and at a deeper depth ranging from 11500 to 13000ft. The synthetic and antithetic faults act as good traps for the hydrocarbon accumulation in the study area. The variance and chaos values range from 0.0 to 1.0. The dip magnitude and azimuth values range from 0 to 90 degrees and 0 to 360 degrees. The variance edge, chaos, dip magnitude and azimuth analysis were used to delineate the prominent and subtle faults in the area. The results of spectral decomposition at a frequency of 12-35Hz indicates areas of low frequency and high amplitude associated with known hydrocarbon zones, the presence of channels, lobes and small scale faults in the field. The result of the seismic attribute analysis has shown that the Fuba field has good hydrocarbon prospects.

Identification of Faulting and Structural Styles in the Onshore Fuba field, Niger Delta, Nigeria

Identification of the faulting and structural styles of Fuba Field, Onshore Niger Delta, Nigeria using Well-logs and 3D Seismic data are here presented. Well-to-Seismic ties, faults and horizon mapping, time-surface generation and depth conversion were carried out using Petrel software. The structural interpretation of seismic data reveal highly synthetic and antithetic faults which are in line with faults trends identified in the Niger Delta. Of the 29 interpreted faults, only synthetic and antithetic faults are regional, running from the top to bottom across the field. These faults play significant roles in trap formation at the upper, middle and lower sections of the field. Two distinct horizons were mapped. Fault and horizon interpretation reveal closures which are collapsed crestal structures bounded by these two major faults. The depth structure maps reveal anticlinal faults. Reservoirs are found at a shallower depth from 6500 to 7500ft and at a deeper depth ranging from 11500 to 13000ft. The synthetic and antithetic faults act as good traps for the hydrocarbon accumulation in the study area. The variance values ranges from 0.0 to 1.0. The Variance edge analysis was used to delineate the prominent and subtle faults in the

Evaluation of Hydrocarbon Reservoir in the “SIMA” Field of Niger Delta Nigeria from Interpretation of 3D Seismic and Petrophysical Log Data

3D seismic and petrophysical log data interpretation of reservoir sands in “SIMA” Field, onshore Niger Delta has been undertaken in this study to ascertain the reservoir characteristics in terms of favourable structural and petrophysical parameters suitable for hydrocarbon accumulation and entrapment in the field. Horizon and fault interpretation were carried out for subsurface structural delineation. In all, seven faults (five normal and two listric faults) were mapped in the seismic section. These faults were major structure building faults corresponding to the growth and antithetic faults in the area within the well control. The antithetic fault trending northwest-southeast and the normal fault trending northeast-southwest on the structural high in the section act as good trapping mechanisms for hydrocarbon accumulations in the reservoir. From the manual and auto-tracking methods applied, several horizons were identified and mapped. The section is characterized by high amplitude with moderate-to-good continuity reflections appearing parallel to sub-parallel, mostly disturbed by some truncations which are more fault related than lithologic heterogeneity. The southwestern part is, however, characterized by low-to-high or variable amplitude reflections with poor-to-low continuity. Normal faults linked to roll-over anticlines were identified. Some fault truncations were observed due to lithologic heterogeneity. The combination of these faults acts as good traps for hydrocarbon accumulations in the reservoir. Reservoir favourable petrophysical qualities, having average NTG, porosity, permeability and water saturation of 5 m, 0.20423, 1128.219 kD and 0.458 respectively.

Hydrocarbon Prospectivity and Risk Assessment of “Bob” Field Central Swamp Depobelt, Onshore Niger Delta Basin, Nigeria

Hydrocarbon Prospectivity and Risk Assessment of “Bob” Field Central Swamp Depobelt, Onshore Niger Delta Basin, Nigeria

Evaluation of Fault Compartmentalization of "XAS" Reservoir, Onshore Niger Delta

Evaluation of Fault Compartmentalization of "XAS" Reservoir, Onshore Niger Delta

Petrophysical appraisal and 3-D structural interpretation of reservoirs in an Onshore Niger Delta Field, Southeastern Nigeria

Petrophysical appraisal and 3-D structural interpretation of reservoirs in an Onshore Niger Delta Field, Southeastern Nigeria

Depositional sequences and petrophysical evaluation to predict potential prospects of clastic reservoirs of “Olu” field, onshore Niger Delta

Depositional sequences and petrophysical evaluation to predict potential prospects of clastic reservoirs of “Olu” field, onshore Niger Delta

Reservoir evaluation of sand beds in sapele field, onshore niger delta

The Sand beds of the Sapele field have been evaluated to ascertain the viability of the field for hydrocarbon development using integration of the structural play and petrophysical indices. Pay sands were delineated using the quick look approach. A seismic horizon of interest was picked using a well control measure. The structural play reveal three major faults responsible for hydrocarbon migration and entrapment mechanisms which contributed to a three-way closure in the area. Litho-stratigraphic correlation revealed repetitive gamma-ray signatures across the wells, an indication of active fault zone, and this defines the complexity of the Sapele field. The gamma-ray signatures infer a clastic marine settings when compare with standard log motifs. Petrophysical results reveal very good pore volumes of over 20% with 0ver 15% effective and an excellent degree to transmit fluid (over 1000mD). The high hydrocarbon saturation of over 70% infer good producibility of the field. The results has extensively showed the viability of the Sapele field for good field development.

Hydrocarbon play assessment of the sapele field, for moveable hydrocarbon indices, onshore niger delta.

A field's hydrocarbon evaluation takes into account the productivity of the hydrocarbon reservoir bearing unit. It basically includes a thorough examination of the geological interpretation of petrophysical parameter indices deduced from well logs. This study uses MHI and proven integrated methodologies including well logs analysis, petrophysical computing, to evaluate the Sapele-field with the objective of establishing its fluid types and hydrocarbon saturations. Three formations across eight wells in the field were delineated using the quick look analysis approach at low gamma ray intervals corresponding to high resistivity kicks. Correlation of the wells was conducted to specifically check the continuity in stratigraphy of the formations across the wells. Petrophysical parameters evaluation were conducted to qualitatively access the formations across the eight wells. Porosity, permeability, water saturation, Net pay thickness, water saturation and MHI were calculated as first and second degrees petrophysical parameters. Results revealed a characteristic thin beddings in the formation across the eight wells, with the same range of net pay thickness. MHI results (0.24-0.61) revealed the formations hydrocarbons are moveable during invasion and this is in agreement with the formations tendencies to accommodate and transmit hydrocarbon (0.14-0.24 porosities and over 250mD) with good hydrocarbon saturations of over 55%. This study has shown that the Sapele field is viable with good hydrocarbon mobility tendency during invasion.

Sequence Stratigraphic Evaluation of Sediments Domicile in Day Field Located in the Onshore Central Swamp Depobelt of the Niger Delta, Nigeria

This study employs the tool of sequence stratigraphy to evaluate Day Field, in the Onshore Niger Delta of Nigeria for hydrocarbon predictions using six (6) well logs displayed at standard scales to enhance log trends for lithologic and stratal package delineation. The identified key stratigraphic bounding surfaces were tied to well-defined palynological (P) zone and foraminiferal (F) zones with the aid of the biostratigraphic data and calibrated using the Niger Delta Chronostratigraphic chart. Five (5) MFSs (34.0, 33.0, 31.3, 28.1, and 26.2 Ma) and six (6) SBs (35.4, 33.3, 32.4, 29.3, 27.3, and 24.9 Ma) were delineated. The stratigraphic surfaces were matched with the palynological (P480– P580) and foraminiferal zones (P20/N1–P22/N3) encountered. The results indicate that the study area is of Late Eocene to Late Oligocene age (26.2–35.9 Ma). The key stratigraphic surfaces also reflect a series of relative sea-level falls (regressive episodes) and sea-level rises (transgressive episodes) that are regionally extensive and correlated across the wells. Five sequences (SEQ1–SEQ5) were recognized, SEQ1 and SEQ5 comprising three system tracts (LST, TST, and HST) revealing four third-order depositional sequences (classified as type 1 sequence), while SEQ2-SEQ4 comprises two system tracts (TST and HST). Two depositional environments were interpreted from the log trends; the Fluvial (shoreface) and Tidal environments. The hydrocarbon exploration prospects identified are the sand units of the LST and HST combining with the shale units of the TST offering good reservoir and seal/source rocks respectively.

Petrophysical evaluation for development of a marginal oil field in the onshore Niger Delta, Nigeria

Petrophysical evaluation was conducted on an onshore marginal field in Niger Delta with the aim of evaluating the rock and fluid properties to boost hydrocarbon production in the field. Five well logs suite from five wells and core log data for two wells were utilized for this study. Petrophysical properties evaluated included; porosity, net to gross, formation factor, irreducible water saturation, permeability, water saturation, hydrocarbon saturation and pay thickness. The well logs suite contained the following logs: Gamma ray log for lithology identification; Resistivity log for fluid type discrimination and determination of water saturation; Density log for porosity determination; and Neutron log in combination with density log for hydrocarbon types. A total of seven reservoir sands (, Sand A, B, C, D, E, F and G) were identified and correlated across all five wells on the basis of gamma ray and resistivity log motifs. The reservoir gross thicknesses ranged from 62.55 to 228.50 ft, shale volume from 7.0 to 24.60%, net to gross from 0.76 to 0.93%, effective porosity from 20.78 to 26.22%, water saturation from 35.80 to 62.30% and permeability ranged from 545.94 to 2821.97 mD. This shows that the reservoirs are of good quality for hydrocarbon productionacross the field.

Seismic Interpretation and Petrophysical Analysis for Evaluation of Ataga Field, Onshore Niger Delta, Nigeria

The majority of geophysical survey in hydrocarbon exploration and production sector is driven by the ability to describe reservoirs. This research is aimed at describing the interpretation and petrophysical analysis of the reservoirs in Ataga field Niger Delta using a combination of seismic and well-log data. The Ataga Field in the Niger Delta was subjected to 3-D seismic interpretation and petrophysical study to perform comprehensive structural interpretation, prospect evaluation, and volumetric calculation. Two reservoir windows “1” and “2” were identified and correlated from four wells ATA 10, ATA 11, ATA 5 and ATA 7. Detailed evaluation was done on well ATA 11 since it is the only well that has sufficient data for both qualitative and quantitative interpretation. Structural interpretation for inline 5731 revealed fifteen faults on the seismic vertical section through ATA 11, most of which are antithetic faults while the rest are synthetic faults. Top and base of each reservoir window was delineated from the well. Result of the petrophysical assessment of reservoir A, B and C for ATA 11 revealed that the porosity values range from (24 -29) % which are indicative of very good to excellent porosity value according to Rider (1996). While the permeability values range from (1887-2582) mD were obtained from the three reservioir A, B and C of ATA 11 which depict very good to excellent reservoir units. Since, .all of the wells were discovered to have hydrocarbon-bearing reservoir formations (sandstones), the integration of structural interpretation and well logs have successfully revealed that the reservoirs are mostly oil-bearing zones.

Petrophysical characterization and 3D seismic interpretation of reservoirs in the Baris Field, onshore Niger Delta Basin, Nigeria

In order to evaluate the petrophysical properties, characterize the structural framework and determine the hydrocarbon in place of potential reservoirs in the Baris Field, onshore Niger Delta Basin, Nigeria, 3D seismic and well log data from the field were collected and interpreted using Geographix and Petrel software. Two reservoir zones B2 and B5 were identified having porosity ranging from 21% to 22%, permeability from 235 to 523 mD and water saturation from 16% to 28%. Petrophysical parameters show that the two zones are good reservoirs and highly petroliferous. Seismic interpretation revealed the presence of six listric faults, two major faults (F1 and F2 trending in the northwest–southeast direction) and four minor faults (F3, F4, F5 and F6). Faults 3, 4 and 5 trend in the same direction as the major faults, while fault 6 trends in the northeast–southwest direction. Two major horizons were identified, and they correspond to the two reservoir tops (B2_top and B5_top). Roll-over anticlinal structures between the two major listric faults were identified. The depositional environment of the Reservoirs B2 and B5 have been deciphered to be of a barrier bar or crevasse play and the trapping mechanism in the Baris Field is a four-way structural closure. STOOIP and GIIP for the two zones have been estimated with the zone B5 more prolific with a STOOIP and GIIP of 7.98MMSTB and 12.77MMMSCF respectively.

Sequence Stratigraphic Interpretation of XY-Field Onshore Niger Delta Basin Nigeria

Wireline logs and biostratigraphic data were integrated to attempt the sequence stratigraphy of “XY field” onshore Niger Delta Basin which revealed three depositional sequences. Four sequence boundaries and three maximum flooding surfaces dated (17.7, 16.7, 15.5, and 13.1Ma) and (17.4, 15.9, 15.0 Ma) respectively were identified in both Wells. The delineated sequences comprised Lowstand Systems Tracts (LST), Transgressive Systems Tracts (TST) and Highstand Systems Tracts (HST), which reflect depositional systems deposited during different phases of base level changes. The sands of LST and HST show good reservoir qualities while the shales of the TSTs could form potential reservoir seals. Integration of lithofacies and biofacies data suggests that the depositional environments ranges from transitional to Outer Neritic environment.

Prospect identification and reservoir characterization using seismic and petrophysical data in ‘Famito’ field, onshore Niger Delta, Nigeria

Prospect identification and reservoir characterization using seismic and petrophysical data in ‘Famito’ field, onshore Niger Delta, Nigeria

Petrophysical analysis of well data for clastic reservoir evaluation and determination of the invaded zone effect: A case study of a field in the onshore Niger Delta, South-South, Nigeria

Two reservoirs domiciled in a well have been analysed in this study in order to obtain the quantitative reservoir properties. These quantitative reservoir properties are essential not only for well development and optimization but also for accurate decision-making prior to reservoir exploitation and production. A suite of composite logs comprising the caliper log, gamma-ray (GR) log, density log, resistivity logs and sonic transit time logs obtained from a field in the onshore Niger Delta was used for the petrophysical analysis. From our quantitative results, Reservoir 1 has the potential to produce oil and gas with a total hydrocarbon saturation of 81%. However, due to the invaded zone effect on the reservoir potential, the total hydrocarbon fluid has been partitioned into moveable hydrocarbon of 65% saturation and immoveable hydrocarbon of 16% saturation. This resulted from the mud filtrate invasion of the radially shallow zone which displaced the original fluid while the undisplaced hydrocarbon fluid remained in the pore spaces of the reservoir. The porosity of the reservoir sand is 33% and its effective porosity is 32.5%. The high effective/interconnected porosity and clean nature of the sand which is due to the extremely small volume of shale present in the sand (just 1.0%) clearly shows that the reservoir is highly porous, permeable and producible.The net pay of the reservoir (represented by the thickness TH in Mesh 1) could not be quantitatively determined due to lack of depth information on the logs. The second reservoir (Reservoir 2) has a total hydrocarbon saturation of 94.8% and water saturation of just 5.2%. The total hydrocarbon saturation is partitioned into 82.8% moveable hydrocarbon saturation and 12% immoveable hydrocarbon saturation which resulted from the invaded zone effect. The porosity of the reservoir was determined at 33% and its effective porosity at 32.5%. Again, the high effective/interconnected porosity and clean nature of the sand arising from the extremely small volume of shale present in the sand (0.4%) is a clear indication that the second reservoir is also highly porous, permeable and producible. The net pay of Reservoir 2 (represented by the thickness TH in Mesh 2) is higher compared to Reservoir 1 but could not be evaluated due to absence of depth values on the logs. In the final analysis, the overall results show that the reservoirs are commercially favourable and have the potential to pay back.

PETROPHYSICAL STUDY OF ‘GLORY FIELD’ RESERVOIR IN SOUTHERN PART OF NIGER DELTA, NIGERIA USING WELL LOG DATA

This purpose of this study is to evaluate the petrophysical properties of hydrocarbon bearing reservoirs in ‘Glory Field’ onshore Niger Delta using well log data from five wells. Petrophysical properties evaluated are shale volume, thickness, porosity, net to gross, formation factor, irreducible water saturation, permeability, water saturation, hydrocarbon saturation and pay thickness. The well logs suite contained the following logs: gamma ray, resistivity, density and neutron logs. A total of three reservoir sands (Sand A, Sand B, and C) were identified and correlated across all five wells using Schlumberger Petrel Software. From the result, on average density, Vp/Vs ratio, AI, shale volume, net to gross ratio, net thickness, effective porosity, permeability, water saturation and hydrocarbon saturation values are 2.15g/cm3, 2.28, 5406.67gcm3ms-1, 26%, 74%, 66.99ft, 25%, 2331.14mD, 48% and 52% respectively for sand A reservoir, while 2.17 g/cm3, 2.05, 6117.38 gcm3ms-1,14%, 86%, 185.04 ft, 26%, 2359.88mD, 56% and 46% respectively for sand B reservoir, and 2.18g/cm3, 2.01, 6275.95gcm3ms-1, 14%, 86%, 197.52ft, 25%, 2121.27mD, 53% and 47% respectively for sand C reservoir. The results of this research revealed very good effective porosity (>20%), excellent reservoir permeability (>1500mD) and pay zone thicknesses exceeding 70ft which are sufficient for hydrocarbon production and field development.