Papers by Rotimi Oluwatosin
Petrophysical Analysis and Sequence Stratigraphy Appraisal from Well logs of 'Bobo' field, South-Eastern, Niger Delta
This work highlights the importance of Petrophysics to hydrocarbon exploration and the relationsh... more This work highlights the importance of Petrophysics to hydrocarbon exploration and the relationship between petrophysical variables and the associated depositional environment as they are sought to be established from correlation of petrophysical properties with sequence stratigraphy. Petrophysical analysis began with lithology identification where it was established from well logs assessments that the study area is characterized by sandshale interbedding having brief serrated wiggles and multiple parasequences stacked within the main sequences. The reservoirs formations were interpreted for their fluid content using appropriate logs. In all, three hydrocarbon bearing sands were discovered, and porosity estimates in the reservoirs were very high varying between 0.19 and 0.39 suggesting good economic opportunities. Sequence stratigraphic interpretation was carried out to interpret the depositional environments around the area using well log motifs. The interpretation shows three main...
The Chemical Modification of Calophyllum Inophyllum Plant Oil for Potential Base Oil in Drilling Mud Operation
Day 1 Tue, August 11, 2020
Research on the use of plant oil or ester oil in drilling mud operation is on the increase. The i... more Research on the use of plant oil or ester oil in drilling mud operation is on the increase. The is due to the less toxic and low cost advantage over the commercial synthetic base oil. Despite the attractive physicochemical properties of vegetable oil samples, it deteriorates and becomes unstable under downhole temperature and aging conditions when used directly in mud formulation. Hence, plant oil needs improvement in order to be compared to the conventional base oil. Calophyllum inophyllum oil was extracted and reacted with methano in the presence of catalyst to form biodiesel. The physicochemical properties of the commercial synthetic base oil, extracted Calophyllum inophyllum oil, and biodiesel Calophyllum inophyllum oil were measured and compared to the EN14214 and the ASTM D6751 standards. The commercial synthetic oil, Calophyllum inophyllum oil, and biodiesel Calophyllum inophyllum oil had a flash point of 101 ± 0.1, 164 ± 0.1, and 146 ± 0.1 °C respectively; density of 108, 17...
Aspects of Stratigraphy and facies profile of clastic deposits in Doma field, Niger Delta
ABSTRACT
Petroleum and Coal
This study explores the use of well logs and seismic derived rock properties to predict hydrocarb... more This study explores the use of well logs and seismic derived rock properties to predict hydrocarbon potentials. Crossplot analysis of well log data and seismic attributes extracted and captured over some depth windows from the vicinity of the prolific hydrocarbon zone was the main methodology. This made it possible to develop relationships through cross-plotting of different log types and different seismic attributes. Emphasis was placed on petrophysics based properties from well logs while the stratigraphic, complex and signal based seismic attributes were computed and analysed. Combination of one or more attributes was attempted in deriving a correlative relationship typifying the reservoir property. The well log derived properties predicted the hydrocarbon potential of the reservoir better as it gave better correlation of above 70% on the crossplots made. While seismic properties crossplots had poor correlation except those of signal based and complex attributes that gave negative correlations.
International Journal of Basic & Applied Sciences
Complexly faulted subsurface configuration is capable of causing erroneous deductions in the abse... more Complexly faulted subsurface configuration is capable of causing erroneous deductions in the absence of a well packaged interpretation approach and workflow for an oilfield exploration programme, thus a well prepared analysis saddled on the use and integration of sufficient data is indispensable to the unravelling of complex field subsurface structure as the search for oil and gas progresses into deeper waters. Suite of signatures from wireline logs and seismic volume was employed to gain more insight into the complexities of the hydrocarbon hosting units within and outside the vicinity of well control in the X-field Niger Delta. Horizons and fault interpretation were carried out to produce subsurface structure maps. Amplitudes of the horizons mapped were extracted and were used to study the distribution of the hydrocarbon sand. Three hydrocarbon bearing reservoirs were delineated within the study interval, namely: ROJ A, ROJ C and ROJ D. Well to seismic tie revealed that these reservoirs tied direct hydrocarbon indicators (bright spots) on the vertical sections. The structure maps produced revealed a series of NW-SE and E-W trending growth faults and fault echelons, most of which dip to the south. Fault assisted closures were revealed at the southern part of the field, which correspond to the crest of roll over structures and possibly served as the trapping mechanism for the reservoirs. The reflection amplitude of the studied horizons shows a fine network of anomalies that can be correlated to the prediction of the lateral distribution of the hydrocarbon sand. The conclusion of the study was that the western part of horizon ROJ A is a highly prospective area as bright spots were observed in the region. Also in the adjacent southern direction of this horizon, hydrocarbon accumulations have been confirmed from wells. These gas sands are possibly trapped in anticlinal closures located in the same area. On the other hand, the results from the study of horizon ROJ C suggest development opportunities in the southern area. High amplitude gas sands are seen to spread to the south and stratigraphy was assumed to play a major role in hydrocarbon migration. The study over horizon ROJ D reveal likely geologic features like regional sand pinch outs and channels in the southern part of the field. Spectral decomposition interpretation was suggested to be used further in improving the delineation of the thin reservoir sand bodies and for better outlining of their geometries but was not available on the workstation used. The study has shown the feasibility of integrating structural interpretation and instantaneous amplitude in prospect identification and reservoir prediction.
Journal of African Earth Sciences, 2014
Stratigraphic and subtle reservoirs such as pinchouts, sand lenses and unconformities have been d... more Stratigraphic and subtle reservoirs such as pinchouts, sand lenses and unconformities have been discovered in Bohai basin. These reservoirs occur in sub-basins and sag structures called depressions. A prolific depression is the Liaohe depression that has been filled with rapidly changing mixed alluvial fan deposit of the Cenozoic age. Attempts made at recovering residual hydrocarbon from the subtle reservoir have necessitated the re-evaluation of available data to characterize and model the prolific Shahejie Formation turbidite deposit occurring as pinchouts and sand lenses for hydrocarbon assessment, reservoir quality and possible recovery through enhanced methods. Methods employed covered well logs analysis, clustering analysis for electrofacies and fuzzy logic analysis to predict missing log sections. Stratigraphic and structural analysis was done on SEGY 3D seismic volume after seismic to well tie. Stochastic simulation was done on both discrete and continuous upscaled data. This made it possible to correctly locate and laterally track identified reservoir formation on seismic data. Petrophysical parameters such as porosity and permeability were modeled with result of clustering analysis. Result shows that electrofacies converged on 2 rock classes. The area is characterized by the presence of interbeded sand-shale blanket formations serving as reservoir and seal bodies. The reservoir quality of the formations as seen on the petrophysical analysis done is replicated in simulation volume results. Reservoir rocks have porosity between 0.1 and 0.25, permeability between 1 and 2mD and hydrocarbon saturation as high as 89%. Lithofacies are observed to be laterally inconsistent, sub-parallel to dipping and occurring as porous and permeable continuous beds or pinchouts hosting hydrocarbon. The stochastic stratigraphic model depicts rock units in associations that are synsedimentary. The prevalent configuration gotten from the model gave an insight into exploring and developing the field for enhanced oil recovery of the heavy hydrocarbon of this area.
Energy, Exploration & Exploitation, 2014
Reservoir characterization deals with the description of the reservoir in detail for rock and flu... more Reservoir characterization deals with the description of the reservoir in detail for rock and fluid properties within a zone of interest. The scope of this study is to model lateral continuity of lithofacies and characterize reservoir rock properties using geostatistical approach on multiple data sets obtained from a structural depression in the bight of Bohai basin, China. Analytical methods used include basic log analysis with normalization. Alternating deflections observed on spontaneous potential (SP) log and resistivity log served as the basis for delineating reservoir sand units and later tied to seismic data. Computation of variogram was done on the generated petrophysical logs prior to adopting suitable simulation algorithms for the data types. Sequential indicator simulation (SIS) was used for facies modeling while sequential gaussian simulation (SGS) was adopted for the continuous logs. The geomodel built with faults and stratigraphical attitude gave unique result for the depositional environment studied. Heterogeneity was observed within the zone both in the faulted and unfaulted area. Reservoir rock properties observed follows the interfingering pattern of rock units and is either truncated by structural discontinuities or naturally pinches out. Petrophysical property models successfully accounted for lithofacies distribution. Porosity volume computed against SP volume resulted in Net to gross volume while Impedance volume results gave credibility to the earlier defined locations of lithofacies (sand and shale) characterized by porosity and permeability. Use of multiple variables in modeling lithofacies and characterizing reservoir units for rock properties has been revisited with success using hydrocarbon exploration data. An integrated approach to subsurface lithological units and hydrocarbon potential assessment has been given priority using stochastic means of laterally populating rock column with properties. This method finds application in production assessment and predicting rock properties with scale disparity during hydrocarbon exploration.
sciencepub.net
A modern field system, Terrameter (Signal Averaging System) SAS 4000/1000, was used to accomplish... more A modern field system, Terrameter (Signal Averaging System) SAS 4000/1000, was used to accomplish the task of exploring groundwater in Kubanni River Basin. 23 image lines were measured at different strategic locations of the study area based on the fractured map of the area and previous information obtained from the area. Four straight line profiles with a spread of 200 m per section were traversed during the course of this survey with three of them generally trending along a North-South direction while the fourth, trends approximately along the East-West direction. The four profiles have a total coverage distance of about 4.2 km. The data used for this survey was acquired by measuring a series of constant traverse along the same line but with the electrode spacing being increased with each successive traverse. Since increasing separation leads to greater depth penetration, the measured apparent resistivities was used to construct a vertical contoured section displaying the variation of resistivity both laterally and vertically over the section. Interpretation of the data acquired using this equipment revealed the suitability of the Southern part of the study area for location of boreholes, as the resistivity values of rock obtained around this zone reflects aquiferous materials. More layers of rock units around Area BZ and Tudun Sarki were revealed than what was reported by previous workers. Also observed were slight variation in depth to bed rock around area BZ and the Nigerian College of Aviation Technology as compared with observations made by previous workers. However, the observation of the increasing undulating bedrock geometry with depth towards the southern part of the study area was consistent with that of the previous workers.
Petroleum and Coal
Structural pattern mapping and modeling for structural styles delineation and prospect identifica... more Structural pattern mapping and modeling for structural styles delineation and prospect identification in the complex Xinglongtai-Majuanzi structure, Liaohe depression, China is a concern in exploring for hydrocarbon. This is as a result of the occurrence of varied faulting pattern and sub-seismic faults. Analysis was on attributes computed from migrated 3D seismic data, with support from well logs from the area. Architectural assessment, structural delineation and prospect analysis was done on the portion of the massive sag structure proven to have originated in the Paleogene period. Combinations of structural and stratigraphic attributes were used in evaluating the nature of the fairly consolidated turbidite deposits of the hydrocarbon prolific Shahejie formation amidst numerous syndepositional faults. Results indicate that normal and reverse faults are quite common in the study area with dipping angle between 50 and 80 degrees. The deposits of interbeded sand shale sequences are characterized by non-uniformity in strata arrangement. The stratigraphy of the area is observed as dipping sub-parallel and chaotic clinoforms which terminates in a thick wedge structure in the distal portion. This pattern is bestowed by the interplay of both the underlying regional and overlying sub-regional strike slip faults. This has increased the heterogeneity of the petrophysical parameters observed for the facies models and thereby assisted in understanding structural trapping configuration for the play prospect of the area.
Improved Water Based Mud Using Solanum Tuberosum Formulated Biopolymer and Application of Artificial Neural Network in Predicting Mud Rheological Properties
SPE Nigeria Annual International Conference and Exhibition
Drilling fluids are the most important materials in drilling operations, therefore improving the ... more Drilling fluids are the most important materials in drilling operations, therefore improving the properties of these fluids are very essential in order to meet up with the increase in demands and required standards. In this experimental study, Solanum tuberosum formulated biopolymer was used to improve the water based mud rheological properties and artificial neural network predicted data for (PV) plastic viscosity, (AP) apparent viscosity and (YP) yield point. Artificial neural network (ANN) was used to train the rheological properties of the formulated mud and the network developed predicted the rheological properties of an untrained combination of bentonite and modified biopolymer. The main target is to regenerate or predict the rheological properties of the formulated mud; (AP) apparent viscosity, (YP) yield point and (PV) plastic viscosity generated originally from experimental procedures but this time using the ANN. The mean average error target was set to around 5-10%. As a m...
Knowledge of reservoir body lateral extent is important information for estimation of hydrocarbon... more Knowledge of reservoir body lateral extent is important information for estimation of hydrocarbon initially in place and the recoverable quantity. This study reports a stepwise approach to evaluate geometrical anisotropy of the rapidly changing alluvial fan Shahejie formation of Eocene age. This is towards understanding reservoir geometry of the deposit beneath the flank of Bohai bay, Northern China. Computation of Sand net to gross (Volume of shale), porosity and permeability was done on well logs as an initial analytical step, followed by computation of sample variograms, data transformation and property modeling. Computation of semivariance was based on first geometrical anisotropy for autocorrelation by finding major and minor directions of data consistency. Autocorrelation of data with distance of location made upscaled data useful for stochastic simulation. Minor data direction is almost perpendicular to the major direction with the bandwidth of not less than 4000. In the vertical direction, average bandwidth is 50. Porosity for the modeled zone is consistent with values between 17% and 35%. Permeability is consistent briefly away from well location but higher in shale units. These oil impregnated shale units are laterally consistent in the up-dip portion but were overtaken by the clastic units in the distal portion. This made draining of hydrocarbon better done in the down-dip portion of the area. An excellent comparative analysis was made of the litho-facies model, petrophysical properties, and inversion results obtained from the vintage seismic. This has yielded a good result in characterizing variation in rock properties of the subtle laterally inconsistent synsedimentary lithofacies of this area.
A successful seismicity alongside core analysis provides data for subsurface structural mapping, ... more A successful seismicity alongside core analysis provides data for subsurface structural mapping, definition of lithology, identification of the productive zones, description of their depths and thickness. Inadequate understanding of Pore pressure of a formation is regarded as one of the major problems drillers face in the exploration area. This may be amongst others, the pressure acting on the fluids in the pore spaces of the rock. Pore pressure can be normal, abnormal or subnormal. Shear waves is a secondary wave that travels normal to the direction of propagation. Shear waves are slow and thus, get to the surface after primary wave. It is with this intrinsic property that this project was initiated and researched. Data was obtained from a major operator in Niger Delta. Methods of this study are as follows: log description, interpretation and analysis and evaluation of pore pressure using the petro-physical parameters, model development using Domenico'sequation as foundation and the shear wave velocity estimation. The result from this study, shows the importance of well logs and shear wave velocity in the evaluation of pore pressure, it also indicates where pressure can be encountered during drilling activities.
This work made use of computed data from well logs, with migrated seismic data, to evaluate rock ... more This work made use of computed data from well logs, with migrated seismic data, to evaluate rock fabric, reservoir fluid, and lithology of an unconsolidated alluvial fan deposit. Acoustic and elastic parameters amongst other logs were computed and used to characterize the subsurface reservoir. This was done to ascertain the possibility and success of well logs derived rock physics parameters in characterizing reservoirs. With the use of soft computing methods and stochastic algorithms, the objectives of this study were achieved. Results were presented in maps and model volumes. Lambda, Mu, Rho, and SP logs were the main inputs in the characterization based on both their individual potential and an integrated convolved potential. Filtered zones identified on cross-plot were applied to simulated volumes of LambdaRho and MuRho, gave good account of its ability to discriminate rock and fluid distribution. RGB visualization tool applied to the models gave a volume that was used to condition litho-units simulation with commendable results.
(Keywords: Lambda, mu, acoustic impedance, elastic impedance, reservoir characterization, RGB, alluvial fan, density)
Changing down-hole conditions observed during hydrocarbon exploration can be divers. Some desired... more Changing down-hole conditions observed during hydrocarbon exploration can be divers. Some desired ones concern oil/gas shows while others may vary from borehole/drilling fluid association and pressure situations. Managing pressure variations and geopressure zones while drilling has been an issue of concern which has yield generic positive results over the years. However pre-pressure zones (i.e. zones above pressure zones), can display characteristics that are worthy of note in view of the underlying rock potential. Pore pressure and fracture pressure has been evaluated using Eaton’s equations amongst others on data for some reservoir of Agbada formation in the petroliferous Niger Delta. This is in view of knowing the potential of this pre-pressured zone with effective porosity and water saturation necessitated by production operations and well re-entry processes. These computations adopted various pressure models and have yielded good result presented as plots. It was observed that depth of rock units is the main indicator of rock shrinkage leading to increase in fracture due to increase in production and hydraulic fracturing. Adequate attention must be paid to the integrity (density) of the explored formation as they become sandwiched with under-compacted argillaceous sediments.
Keywords: drilling, pressure, pre-pressure, fracture, shrinkage, porosity, pore pressure.
Reservoir characterization deals with the description of the reservoir in detail for rock and flu... more Reservoir characterization deals with the description of the reservoir in detail for rock and fluid properties within a zone of interest. The scope of this study is to model lateral continuity of lithofacies and characterize reservoir rock properties using geostatistical approach on multiple data sets obtained from a structural depression in the bight of Bohai basin, China. Analytical methods used include basic log analysis with normalization. Alternating deflections observed on spontaneous potential (SP) log and resistivity log served as the basis for delineating reservoir sand units and later tied to seismic data. Computation of variogram was done on the generated petrophysical logs prior to adopting suitable simulation algorithms for the data types. Sequential indicator simulation (SIS) was used for facies modeling while sequential gaussian simulation (SGS) was adopted for the continuous logs. The geomodel built with faults and stratigraphical attitude gave unique result for the depositional environment studied. Heterogeneity was observed within the zone both in the faulted and unfaulted area. Reservoir rock properties observed follows the interfingering pattern of rock units and is either truncated by structural discontinuities or naturally pinches out. Petrophysical property models successfully accounted for lithofacies distribution. Porosity volume computed against SP volume resulted in Net to gross volume while Impedance volume results gave credibility to the earlier defined locations of lithofacies (sand and shale) characterized by porosity and permeability. Use of multiple variables in modeling lithofacies and characterizing reservoir units for rock properties has been revisited with success using hydrocarbon exploration data. An integrated approach to subsurface lithological units and hydrocarbon potential assessment has been given priority using stochastic means of laterally populating rock column with properties. This method finds application in production assessment and predicting rock properties with scale disparity during hydrocarbon exploration.
Structural pattern mapping and modeling for structural styles delineation and prospect identifica... more Structural pattern mapping and modeling for structural styles delineation and prospect identification in the complex Xinglongtai-Majuanzi structure, Liaohe depression, China is a concern in exploring for hydrocarbon. This is as a result of the occurrence of varied faulting pattern and sub-seismic faults. Analysis was on attributes computed from migrated 3D seismic data, with support from well logs from the area. Architectural assessment, structural delineation and prospect analysis was done on the portion of the massive sag structure proven to have originated in the Paleogene period. Combinations of structural and stratigraphic attributes were used in evaluating the nature of the fairly consolidated turbidite deposits of the hydrocarbon prolific Shahejie formation amidst numerous syndepositional faults. Results indicate that normal and reverse faults are quite common in the study area with dipping angle between 50 and 80 degrees. The deposits of interbeded sand shale sequences are characterized by non-uniformity in strata arrangement. The stratigraphy of the area is observed as dipping sub-parallel and chaotic clinoforms which terminates in a thick wedge structure in the distal portion. This pattern is bestowed by the interplay of both the underlying regional and overlying sub-regional strike slip faults. This has increased the heterogeneity of the petrophysical parameters observed for the facies models and thereby assisted in understanding structural trapping configuration for the play prospect of the area.
Sequence stratigraphy model developed for the Ningning field is based on the interpretation carri... more Sequence stratigraphy model developed for the Ningning field is based on the interpretation carried out on the different wells that penetrated the various subsurface lithologies. Basically three depositional sequences were delineated from the five wells studied. The Vail model used made out a third and forth order stratigraphic surfaces that all fall within the central swamp depobelt of the Basin. The five wells used show the presentation of the interpretation and the models. All the sequence tracts were appropriately represented starting from the Lowstand Transgressive and Highstand system tracts, except in well 005 where the Lowstand of the second sequence was missing. This is achieved by incorporating signature motifs from wireline logs coupled with biostratigraphy data and inferred paleobathymetry. This has revealed the field-wide reconstruction of a chronostratigraphically constrained biostratigraphy of subsurface lithological sequences with limited information.
This work highlights the importance of Petrophysics to hydrocarbon exploration and the relationsh... more This work highlights the importance of Petrophysics to hydrocarbon exploration and the relationship between petrophysical variables and the associated depositional environment as they are sought to be established from correlation of petrophysical properties with sequence stratigraphy. Petrophysical analysis began with lithology identification where it was established from well logs assessments that the study area is characterized by sandshale interbedding having brief serrated wiggles and multiple parasequences stacked within the main sequences. The reservoirs formations were interpreted for their fluid content using appropriate logs. In all, three hydrocarbon bearing sands were discovered, and porosity estimates in the reservoirs were very high varying between 0.19 and 0.39 suggesting good economic opportunities. Sequence stratigraphic interpretation was carried out to interpret the depositional environments around the area using well log motifs. The interpretation shows three main categories of depositional environments that are dominant in the area and these include: coastal deposits and pro-delta sands, shoreface sands and reworked sandstones, slope fan and the basin floor fan environment. It is predicted that the shoreface sands and reworked sands are the best region of hydrocarbon accumulation. The interpretation model is that the fluvial system flushes abundant clay to fine sand onto the delta front. These fine sediments in all probability are reworked by marine processes of moderate wave energy. This in the region has been predicted to be one of the contributing factors for the hydrocarbon accumulation observed in the area. __________________________________________________________________________________________
This study explores the use of well logs and seismic derived rock properties to predict hydrocarb... more This study explores the use of well logs and seismic derived rock properties to predict hydrocarbon potentials. Crossplot analysis of well log data and seismic attributes extracted and captured over some depth windows from the vicinity of the prolific hydrocarbon zone was the main methodology. This made it possible to develop relationships through cross-plotting of different log types and different seismic attributes. Emphasis was placed on petrophysics based properties from well logs while the stratigraphic, complex and signal based seismic attributes were computed and analysed. Combination of one or more attributes was attempted in deriving a correlative relationship typifying the reservoir property. The well log derived properties predicted the hydrocarbon potential of the reservoir better as it gave better correlation of above 70% on the crossplots made. While seismic properties crossplots had poor correlation except those of signal based and complex attributes that gave negative correlations.
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Papers by Rotimi Oluwatosin
(Keywords: Lambda, mu, acoustic impedance, elastic impedance, reservoir characterization, RGB, alluvial fan, density)
Keywords: drilling, pressure, pre-pressure, fracture, shrinkage, porosity, pore pressure.