Modeling formation pressures as an input by the engineers into drilling programs come in differen... more Modeling formation pressures as an input by the engineers into drilling programs come in different styles and reliability. Kicks, loss of circulation, blowouts and even loss of lives are some of the major tragedies associated with poor modeling. The use of 1D has proved to be a sufficient tool; however, it has fallen short of modeling inflation in formation pressure alongside other pressures. The integration of 1D and clay diagenesis to infer formation pressure is robust. Gamma ray logs were loaded into the log panel for correlation, normal compaction was generated from sonic log while overburden stress (OBS) was estimated from density log. Transit time from sonic was used in obtaining Vertical Effective Stress (VES) by applying an exponent and deducting VES from the OBS to obtain formation pressure (FP). Percentage of Illite/Smectite + Illite (ILLISM) transformation and Kaolinite +Dickite + Halloysite transformation to illite were obtained from clay minerals analysed by XRay Diffra...
Reducing Uncertainties in Mud-Gas Data Acquisition While Drilling-Offshore Depo-Belt, Niger Delta
SPE Nigeria Annual International Conference and Exhibition, 2018
Over the years, the acquisition of gas in mud is crucial to the exploration and production (E&... more Over the years, the acquisition of gas in mud is crucial to the exploration and production (E&P) industry for the evaluation of hydrocarbons presence in the geological formation, and for monitoring of drilling operations. The mudloging technique involves continuous gas extraction and analysis from a circulating drilling fluid for quantity and composition using surface gas trap, gas lines and gas analyzer. This paper presents major uncertainties that associated with gas acquisition during drilling, sources of the uncertainties, and the way forward to acquire highly accurate gas-in-mud data. During the process of acquiring gas-in-mud data, some uncertainties have been observed which can adversely impact real-time decision making as well as cascading effect on the geological models built with this data. In some of the recent wells drilled in offshore depo-belt of Niger delta the following uncertainties were observed; (1) Shift-in-the gas analysis window- Methane (C1) and heavy gas components (C4 and C5) were present in the absence of some light gas components (C2 and C3), (2) Misaligned gas data- gas values acquired misaligned with the resistivity readings of the reservoir being drilled, and (3) Gas in mud (volume and component) underestimation across the reservoirs; Lao-2 reservoir up to 35 units (0.7%) total gas, and gas composition- C1 to C3, and Mao-1 reservoir up to 27 units (0.54%) total gas, and gas composition- C1 to C2 were recoreded at well 43H drilled. This study showed that these uncertainties could result from a drop-in sample pressure or moisture in the gas line, real-time transmission of gas in mud data in bit depth instead of lagged depth and poor calibrations of gas analyzer. The issues then, are how to minimize these uncertainties to obtain accurate gas in mud that truly represent the reservoir being drilled. A systematic approach was deployed to minimize the abovementioned uncertainties. The methodology adopted significantly improved the data acquired in the new well drilled in the field. Highly accurate gas in mud data were obtained in the same reservoirs at the new well (44H) across Lao-2 reservoir: 190 units (3.8%) total gas, and gas composition- C1 to C4, and Mao-1 reservoir: 430 units (8,6%) total gas, and gas composition- C1 to C5. The new well is about 200m away from well 43H. The new well 44H was drilled under same drilling conditions as well 43H; same drilling fluid properties, rheology, mud weight, bottom hole assembly configuration and within the same fault block. Thus, we recommend; constant inspection of surface gas trap and gas agitator, periodic blow back of gas lines, multiple points gas calibrations, detailed gas analyzer calibrations for both total hydrocarbon analyzer and gas chromatograph prior to drilling operations, Maximum of five percent standard error margin, and periodic inspection of gas analyzer filament.
Impact of lithologic heterogeneity on acoustic velocities in the Bornu basin, Nigeria
Six exploratory wells were analyzed and interpreted with the aim of determining the effect of lit... more Six exploratory wells were analyzed and interpreted with the aim of determining the effect of lithologic heterogeneity on acoustic velocities using the petrophysical properties calculated from the logs. The wells include Murshe-1, Tuma-1, Ziye-1, Krumpta-1, Gubio SW-1 and Herwa-1. Gamma ray logs were used for the lithological delineation; the computation of porosity and compressional (acoustic) wave velocity was achieved utilizing sonic logs while the sediments bulk density was determined from density log. The analysis of compressional wave velocity with depth confirms a general trend of non-linear increase in velocity with depth across the wells, and there exists a marked lithological variation between 3000 m and 3200 m depth across the wells in the basin. Also, analyses of the results depict a non-linear increase in density with depth. The relationship between permeability and depth showed permeability increasing in high porosity areas. Permeability range value of 116 to 9238 MD a...
This study was carried out to investigate the subsurface structure in a landslide area in a commu... more This study was carried out to investigate the subsurface structure in a landslide area in a community in Ohafia Abia State, using geophysical data obtained from the subsurface formation of the area. A total of seven stations comprising of three vertical electrical sounding (VES) using Schlumberger electrode configuration and four electrical resistivity profiling (2D) using Wenner array configuration were occupied. Resistivity data were acquired using the Abem terrameter (AGI single R8). The data were smoothened and analyzed using Schlumberger computer automatic iterative software. In the same line seismic critically refracted data were acquired using 12-channel ABEM Terraloc MK III digital seismometer and processed with the Reflexw software into 2D velocity depth models. A two-layer model was delineated by the velocity profile with a range of 338 m/s and 4356 m/s for the entire depth of probe. Results of resistivity model show 6 constrained geo-electric layers covering a total depth...
Journal of the Nigerian Association of Mathematical Physics, 2019
Acoustical properties employ sonic wave velocities as spring board to mirror the sediments. The a... more Acoustical properties employ sonic wave velocities as spring board to mirror the sediments. The albatross associated with analyzing constituent sediment warrants that grain structures and mineral composition are well highlighted for meaningful results. The combination of whole rock mineralogy and well logs give a detailed road map to unraveling the rock physics trend of sediments through mechanical properties and petrophysics generation. The generations of velocity ratio (Vp/Vs), acoustic impedance (AI), Poisson ratio (PR) in this work were in no small means helpful. These accomplishments held without losing focus of the dominance of either smectite or kaolinite and even their combination by pore filling smectite of kaolinite in the case of clay volume in shale; quartz cementation by pore filling smectite in the case of sandstone to pure sandstone (zero clay volume) without down-playing the all important K-feldspar. In well 1, quartz has a range of 19-27% with some points showing hi...
Asian Journal of Research and Reviews in Physics, 2020
The focus of this study is to investigate the structures peculiar in Udi, Enugu State, Nigeria. T... more The focus of this study is to investigate the structures peculiar in Udi, Enugu State, Nigeria. This was achieved by delineating the regional from the residual, determining the lateral and sedimentary thicknesses of causative structures with their lateral boundaries and corresponding lineaments. Regional-residual separation was employed on the aerogravity dataset while Georeferencing and creation of new coordinate system was undertaken on the Landsat data. Causative sources with short and long wavelength trending in the NE-SW, NNE-SSW, E-W, WNW-ESE, N-S and NW-SE directions were found to exist within the study area as qualitative analysis was applied on the aerogravity and landsat data. The NE-SW and NW-SE trends are possible oil and gas rich belt within the area. Quantitatively, two depth source models D1 and D2 were identified. D1 depicting depth to deeply seated sources varies from 0.00071 to 0.0044 km with true thickness of 0.01 km. The shallow related sources expressed using D2...
Estimation of hydrocarbon volume is a critical issue for the economic aspect of the petroleum ind... more Estimation of hydrocarbon volume is a critical issue for the economic aspect of the petroleum industry. It is very key in production to estimate reserves and after considerable production, to determine the efficiency of recovery and also as a basis for advanced studies such as reservoir simulations. The petrophysical parameters and hydrocarbon volume within the Central swamp depobelt in the Niger Delta has been evaluated from seismic and well logs data. Two reservoirs, GA and GB were delineated from the logs. The lithologies are sand and shale sequences. The trapping system were interpreted from seismic sections as anticlinal and fault closures. Two horizons and several faults were mapped from the seismic sections. The faults mapped are mainly synthetic and antithetic, characteristic of the Niger Delta. The seismic to well tie shows a fairly good match. The average porosity and permeability estimated for reservoir GA are 20% and 1338 md respectively. Similarly, the estimated average porosity and permeability for reservoir GB are 21% and 1392 md respectively. The results show that the oil bearing zones in the reservoirs are porous and highly permeable. There was no gas present in either of the reservoirs. The estimated initial hydrocarbon in place for reservoirs GA and GB are 57.84 MMSTB and 48.43 MMSTB respectively. The results of the research shows that the field has a decent hydrocarbon potential and can be economically produced from.
Seismic refraction tomography was carried out in Ebem community, Ohafia, eastern Nigeria, which r... more Seismic refraction tomography was carried out in Ebem community, Ohafia, eastern Nigeria, which recently experienced erosional landslide. The aim was to determine the near surface characteristics in the area, offer possible geologic explanation to the frequent landslides which occur in the area and provide information on potential slide zones to mitigate future disasters. A total of three seismic refraction profiles were carried out using a 12-channel ABEM Terrace MK III digital seismograph with inter-channel spacing of 10 m. Shots were generated by means of a 6 kg sledge hammer and metal plates at 23.5 m before the first and after the last geophone group respectively, and at every geophone station, giving a total length of 157 m for each profile. Velocity structure from the study shows that the area is made up of three different layers on account of velocity distribution, which includes a top layer of unconsolidated, low velocity dry sands assumed to be weathering layer with velocity ranging from about 412 m/s to 1,300 m/s. This layer varies in thickness from about 9 m at the flanks to about 35 m at the center, creating a thick zone of low velocity at the center. This is underlain by a very thin, apparently more compacted sub-weathering layer containing a mixture of sands and clay in which velocity and thickness vary from about 1,300 m/s to 3,000 m/s, and 2,31 m to 3.01 m respectively. Compressional velocity in the area varies from about 412 m/s to about 4.090 m/s, and velocities in the bedrock generally exceed 3,000 m/s; the velocity generally increasing with depth from the surface. The results suggest that the frequent landslides in the area are likely the result of the thick, unconsolidated and permeable dry sands underneath the surface which presumably acts as a sinkhole for surface water runoffs orchestrated by the frequent rainfall which is common in the area. Areas with the highest thickness of weathering are the most vulnerable to sliding in the area.
At least in the last 10 years, considerable effort has been given to studying the dynamics of flu... more At least in the last 10 years, considerable effort has been given to studying the dynamics of fluid flow in porous media. The phenomena is widely applicable in many areas of science and engineering. In many cases, the effect of capillary pressure and discontinuities in the two-phase flow dynamics is not fully clear, especially in petroleum reservoirs. In this paper, we introduce a new method based on the Chebyshev wavelets collocation method and the so-called operational matrices of integration. The method was implemented specifically for an oil-water-phase flow in heterogeneous reservoir using different capillary pressure treatments. Convergence and accuracy of this method were established and used to simulate the partial differential equations governing the two-phase model. The method incorporates the various conditions of the complex governing equations as a single system. The system is subsequently reduced into a simple set of algebraic equations making the problem easier to solve. Numerical results showed that the method is able to account for the expected discontinuities occurring in the flow process. It was also found that these discontinuities or jumps in the two-phase flow are caused by the capillary pressure as expected physically.
The study evaluates the petrophysical properties of the reservoir sands of the Chad basin Nigeria... more The study evaluates the petrophysical properties of the reservoir sands of the Chad basin Nigeria in an attempt to evaluate its prospect for hydrocarbon accumulation. The sand units within the Fika, Gongila and Bima Formations from 12 exploratory Wells drilled in the area were delineated in order to estimate the rock properties such as porosity, permeability, water saturation, hydrocarbon saturation and net-to-gross (NGR) values. The interpretation of the computed values suggests that the sandstone units in the basin have the potential to accumulate and transmit hydrocarbons. The thicknesses of the sand units vary from 10 to 360 m, with an average porosity of 26.62% for all the Wells. The permeability of the rocks ranges from 75 to 5600 mD, suggesting good to excellent while the hydrocarbon saturation of the interstitial spaces are between 3.64 and 83.78 %. Although the overall average porosity and permeability are within limits required for hydrocarbon generation and accumulation, ...
Three hundred and thirty earthquakes data sets within a period of twenty-six years (1990 -2016) w... more Three hundred and thirty earthquakes data sets within a period of twenty-six years (1990 -2016) were obtained for the Mid-Atlantic Ridge and East African Rift. The data were analyzed using Seismic Analysis software (SEISAN 9.0) and Microsoft Excel, and the results showed that the earthquakes occur more at a focal depth of 10 km. The body wave magnitude for EAR ranged between 4.1 to 6.6 with a dominant magnitude range of 4.5 4.9 and 5.0 – 5.4 having 53 and 52 (32%) occurrences respectively. mb for MAR ranged from 4.1 to 6.4 and recorded a dominant magnitude range of 4.5 – 4.9 and 68 (41%) occurrences. Surface wave magnitudes for EAR and MAR ranged from 4 to 7.2 and 4.1 to 7 respectively while their dominant Ms range was 4.5 – 4.9 with 18 (28%) and 26 (34%) occurrences respectively. Moment magnitude for EAR and MAR ranged from 4.7 to 7.1 and 4.9 to 6.8 respectively while their dominant range was 5.0 – 5.4 with 29 (45%) and 37 (49%) occurrences respectively. Monthly time occurrence sho...
Seismic surveys are typically performed in uncontrolled environments. Moving vehicles, animals or... more Seismic surveys are typically performed in uncontrolled environments. Moving vehicles, animals or humans, including faulty recording instruments, pipelines and oil production well pumps can degrade the quality of the recorded seismic data with broadband coherent noise. The efficient attenuation of coherent noise in seismic data is therefore of high importance for high quality seismic images. Coherent noise suppression is particularly challenging in an ocean bottom cable seismic data since the level of noise recorded by the hydrophone and geophone sensors vary considerably. This becomes even more challenging when the hydrophone and vertical geophone data are to be summed for enhanced multiple attenuation without introduction of artefacts in the data. In this work, we present a procedure that effectively suppressed coherent noise in a 4-C seismic data from the Niger Delta, based on the application of a spatial filter in the frequency-offset domain, with additional shear leakage noise ...
Groundwater potential evaluation of Okigwe District of Imo State of Nigeria was carried out based... more Groundwater potential evaluation of Okigwe District of Imo State of Nigeria was carried out based on 120 vertical electrical soundings (VES) in the area. The Schlumberger electrode array was adopted with a maximum electrode spread of 900m. Twelve of the VES stations were sited near existing boreholes to enhance interpretation. The results revealed a multi- layered earth. The resistivity of the aquiferous zones ranged from 33.1Ωm obtained at Umuedi (VES 7) in the northern part to 32600Ωm obtained at Otoko (VES 93) in the southern part of the area. The highest aquifer thickness of 104.4m was recorded at Amonze (VES 95). The hydraulic conductivity values obtained from the VES results varied from 9.8854 to 115.9646 m/day. The transmisivity values ranged from 992.04 to 10263.65m3/day. The storativity values determined for the area ranged from 1.59x10-4 to 7.80x10-3 while the specific capacity is fairly uniform with magnitude of about 877. Groundwater potential evaluation of the district ...
Effort is made in this study to establish the hydrocarbon potential of the Bornu Basin by analyzi... more Effort is made in this study to establish the hydrocarbon potential of the Bornu Basin by analyzing the thermal maturation indices in 14 exploratory Wells in the area. The time-temperature index, virtrinite reflectance and maturation index were modeled to establish the thermal maturity condition of the basin, based on established geothermal gradient, subsurface temperature and burial history. The estimated TTI values derived from Lopatin’s method was compared with the measured Ro to validate the accuracy of the findings. The results show that sediments from late Santonian units in the basin have reached sufficient thermal maturity to generate hydrocarbons. The peak of the maturation at about 3920 m when TTI is 68.8 and Ro of 1.33, occurs at about 99.5 Ma. The onset of maturation is defined by TTI of 15 at sediment of 3920m occurs at 108 Ma.
Multichannel processes in signal processing tend to ‘smear’ anomalously high and low amplitudes i... more Multichannel processes in signal processing tend to ‘smear’ anomalously high and low amplitudes in the seismic data. Removal of traces with anomalous amplitudes in the earlier stages of seismic data processing is therefore expedient. In most cases, manual inspection of the gathers is carried out during trace editing, where any identified trace with anomalous amplitude is edited out from the record. Due to human error, a number of traces with anomalously high or low amplitudes are retained in the data, and this leads to a number of problems in subsequent processing, especially signal processing stages. Resolving these problems later in the processing incurs cost and leads to loss of time. We present in this paper, a global statistical approach that successfully detected anomalous traces in a streamer dataset from the Niger Delta offshore. The technique is able to flag anomalously high and low amplitude traces globally prior to signal processing, and provides an easy and quick way of ...
Overpressure issues in prospecting for hydrocarbon arecritical, constituting an all-important inp... more Overpressure issues in prospecting for hydrocarbon arecritical, constituting an all-important input in drilling campaigns for economic and safety purposes. Estimation of overpressure using a combined approach is more reliable. Wireline log data and derived acoustic impedances (AI) of the seismic volume of this field were applied. The Eaton’s modified model that converted compressional velocities to Vertical Effective Stresses were used to obtain the subsurface pore pressure (PP). The AI of a Prestack Depth Migration seismic volume was generated as its amplitudeshows some tectonic issues. In well 1,2132.8ms and 2268.6ms correspond to depths of between 2600m and 2800m on the log panel with a pore pressure gradient of 0.67psi/ft. From about 2700ms (above 3400m), AI decreased. Well 2 experienced a major drop in (AI) above 2000ms (2400m) and below 2300ms (2800m or 9240ft). Within this bracket, pore pressure gradient ranged between 0.66-0.74psi/ft with a peak of 0.74psi/ft at 2503m. Above...
IOSR Journal of Applied Geology and Geophysics, 2016
This study attempts to optimize hydrocarbon production of an oil Field in Niger Delta through an ... more This study attempts to optimize hydrocarbon production of an oil Field in Niger Delta through an uncertainty free hydrocarbon reservoir modelling. Four well logs and seismic data of 5500 to 5900 inline and 1480 to 1720Xline range were used to build a structural model and reduce uncertainties from the delineated reservoirs. All the four wells have reservoirs of interest as delineated from well logs based on sand formation resistivity values and porosity information. From the logs interpretation hydrocarbon prolific sand of each well was correlated as reservoirs D and F. The depth and the lateral extent of the reservoirs were secured by tying the well 2 to inline of the seismic. Faults were interpreted along the fault trends using fault sticks. Out of many interpreted faults only F7, F8, F10 and F20 cut across the delineated reservoirs. The horizons of reservoirs D and F were also interpreted and the isochronal maps generated. Time to Depth conversion using the T-Z curve gave rise to the depth maps, upon which the reservoir tops were delineated. To generate the structural model, the faults which cut across the reservoir were modeled and pillar gridded to have 10000 cells with each one having a petrophysical property. This formed the skeleton of the reservoir which was layered on the depth map thereby building the structural model. Furthermore, different hydraulic zones (stratigraphic intervals) of the structural model were established. Zonation of the reservoirs enhanced the sensitivity of the petrophysical properties in every stratigraphic interval of the structural model. The structural style showed fault enclosed anticlinal structure while the grid cells from the skeleton of the structural model, depicts the top, middle, and the base of the reservoir.
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Papers by Cyril Nwankwo