bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Improved Estimation of the Storage Capacity of Potential Geologic Carbon-Sequestration Sites
Authors: Lawal Kazeem A. 
Published: July 2011

Abstract
The ideas of open and closed-boundary systems are explored to investigate the technical limits of storage capacity of subsurface porous media, as required for the CO2-mitigation technology of carbon capture and storage (CCS). In particular; the effects of reservoir characteristics as well as the nature and mix of fluids that originally saturate the porous media are elucidated. An improved analytic method, premised on the concept of in-situ fluid displacement and replacement, of estimating the storage capacity of open systems is proposed and evaluated.
For closed systems, our analyses show that the general order of attractiveness (technical storage capacity) of potential sites is aquifer &lt; water-depleted oil &lt; undepleted oil &lt; gas-depleted oil &lt; depleted gas &lt; undepleted gas formations. However, owing to the complexity of microscopic and macroscopic events, similar simple conclusion can not be drawn on the relative attractiveness of various open-boundary sinks.
As a case study, we examine the applicability of CCS in Nigeria. From first-order estimates of the pore volumes and other reservoir-fluid properties in Nigeria, we quantify the limits and time-scale of "available" geologic sinks to accommodate current and future loads of anthropogenic CO2 emissions from the Nigerian fossil-fired power sources.
Due to the relatively poor storage capacity of the potential sites compared to the anticipated CO2 load from power plants, which is just one of the CO2 sources, sequestration into underground formations may not, on its own, be a sustainable technical solution for Nigeria. Additionally, for the open systems, which define the upper limits of storage capacity, the potential challenges of managing displaced formation brine (and other less valuable fluids) may be overwhelming. As a complement, we offer some potential outlets for CO2 generated from these captive and other sources. Finally, long-term carbon-mitigation strategies hinged on mixed solutions are enumerated.
An Integrated Approach to Identifying and Reducing Reservoir Uncertainties in a Turbidite Deep Water Environment
Authors: Akingbade D. , Umurhohwo J. , Effiom O. , Pirmez C. , Weaver S. 
Published: July 2011

Abstract
Deep water developments have become increasingly challenging due to the heterogeneity of the reservoirs where complex architectures associated with turbidite deposition often results in reservoir compartmentalization and complex drainage pathways. These in most instances, result in sub-optimal reservoir development and sweep efficiency. Over the years, identifying and reducing the uncertainties associated with field development as a result of these compartmentalization and other complexities have been a major challenge to geologists and engineers in subsurface studies. This has necessitated the integrated application of high resolution 3D and 4D seismic, well logs, cores, latest techniques and concepts to narrow down the range of uncertainties for optimum reservoir management.
To reduce the uncertainty in the depositional architecture of the Bonga field reservoirs, a holistic approach involving the loop scale seismic stratigraphy interpretation techniques, detailed static and dynamic modeling strategy was adopted to determine the reservoir properties. The understanding of sub-regional to reservoir scale seismic stratigraphy has been used in framing the geological constraints which forms the basis for building realistic static and dynamic models. Loop-scale seismic stratigraphy is used to extract the maximum information from the seismic data. The static reservoir models are generated by a hierarchical workflow where large scale structures such as the channel complexes are modeled first, then the internal geometries such as the channel storey sets and finally the reservoir properties are populated based on well logs, cores and reservoir analogues. These static reservoir models are taken into the dynamic simulator where the reservoir uncertainties are re-assessed based on matching the production history and 4D seismic. The dynamic reservoir modeling involves the use of Stochastic Uncertainty Management techniques incorporating the Design of Experiment with the objective of narrowing the range of uncertainties in the subsurface parameters.
Integrating the static and dynamic modeling of the reservoirs provides a major improvement in our understanding of the subsurface by eliminating scenarios that do not honor all of the data available. This study has resulted in subsurface models that represent an improved understanding of reservoir property distribution and connectivity. These models are being used for improved reservoir management strategies and effective field development planning.
Analytical Evaluation of Kukaku Field
Authors: Qiang Ma , Samson Ibukun , Kenneth Eke , Odogu David , Onyekonwu Mike 
Published: July 2011

Abstract
Analytical studies serve as the primary (first pass) models for evaluating field performance before proceeding to full field numerical models. The decision to proceed to a full field numerical model is usually determined by results of the analytical study and cost of the study relative to the estimated reserves in the field. This implies that for smaller fields, analytical studies may be the major reference for field development.
This paper presents the workflow and results of integrated analytical studies performed on Kukaku, an onshore field in Niger Delta belonging to the Nigerian Petroleum Development Company (NPDC), jointly operated by NPDC and SIPEC. The studies done include petrophysical analysis, welltest (DST) interpretation, NODAL™ analysis, choke performance studies, coning studies and material balance forecast. The paper focuses on key areas of integration in the workflow and best practices in the study.
Conclusion from the study is that integration is also a key concept in analytical field studies especially for smaller fields in which the reserves size precludes the use of expensive numerical models. In such cases, critical analysis of available data and best use of such data to generate rigorous and robust analytical models are key to the optimal development of such fields.
Application of 4D Seismic Response as a Screening Tool in Assisted History Matching
Authors: Bakare Olatunji , Umurhohwo Jonathan , John Ikomi , Okonkwo Arinze , Tope Fehintola , Benjamin Osaigbovo 
Published: July 2011

Abstract
It is best practice in reservoir engineering to have a probabilistic distribution of expectation ultimate recovery all within the scope of credible history match. A P90, P50 and P10 function can thus be derived from such distribution. In most cases the basecase deterministic model is almost always not too far from the probabilistic P50 case. To properly quantify the whole range of key uncertainties engineers are increasingly turning to Design of Experiment (DoE) and Assisted History-Matching (AHM). Understanding the fundamentals is key, implementing the DoE is even more imperative and relating it to the ‘behavioural’ antecedent seen in the reservoir will go a long way to obtaining credible history matches. This paper details how the workflow of DoE/AHM was used to quantify the impact of key uncertainties in obtaining a wide range of credible history match for reservoirs in the Bonga field. 4D seismic response was used to further screen the equally probable models arriving at fit for purpose models constrained to observed fluid movement. This approach focused on the use of saturation changes with direction and sizes of the flood fronts to select models that show little deviation from the 4D seismic response, and reject those that show a large deviation.
Application of Intervention Analysis to Oil and Gas Production Series in Niger Delta, Nigeria
Authors: Biu Oyinebifun. E. , Iwueze Iheanyi. S. 
Published: July 2011

Abstract
There seems to be a rush towards the ever increasing literature on the Niger Delta Area of Nigeria, where crisis has been the order of the day. Interestingly the existence of enormous oil and gas reserves in the region and the threat of disruption of its extraction by the militants have increased globally which has led to drastic reduction in Oil and Gas production in the region. It is of interest to study whether or not the reduction materialized and the measure of this reduction in order to maintain stability in the region. The effect of an intervention on Oil and Gas production series was studied using (i) the usual intervention analysis of Box and Tiao (1975) where AR(3) model with constant was built for the pre-intervention sample and an intervention model was identified for the intervention period for the data set. (ii) CUSUM charts were constructed to monitor changes in the process level after the intervention. The result from the CUSUM chart shows that the crisis in the region have reduced oil production for about 12 or 13 months and Gas production for 8 or 9 months. Thus, it seems reasonable to conclude that the militant attacks in Niger Delta region were instrumental in the reduction of Oil and Gas production.
Application of Microlog in Net to Gross Uncertainty Management
Authors: Agubaeze John , Arochukwu Elias , Kehinde Dare , Simon Roya 
Published: July 2011

Abstract
Net to Gross (N/G) is a key input parameter into the estimation of Hydrocarbon In-Place volume. Errors in N/G evaluation could result in huge impact (up to 40%) on estimated in-place volumes which would in-turn affect the economics of reservoir/field development.
Traditionally Gamma ray (GR) and/or SP logs are used for delineating reservoir sands from non-reservoirs. However, in some instances, these logs are not able to differentiate fully some reservoirs from non-reservoirs. In the case of GR, it is not able to resolve differences between shales and sands with high radioactive materials contents. Both GR and SP logs do not differentiate non reservoir cemented tight sand formations. This lack of contrast on the logs in such circumstances results in errors in the estimated net reservoir sands, leading to inaccuracies in the overall estimated reserves.
To account for the deficiencies of these traditional techniques, a combination of neutron porosity and formation density logs may be deployed. These tools are able to provide contrasting petrophysical properties that differentiate between impervious formations and reservoir sands, thereby providing robust technique for improved net sand estimation.
Incidentally, most old wells drilled in the 1950s up to mid 1980s do not have the neutron and the density logs. Yet for some early operators, a majority of the old wells were strategically positioned that the openhole data from them would be very crucial for estimation of reserves in the concerned fields. A cursory review of the log database reveals the abundance of Micrologs (Microlog Normal (MLN) and Micro Log Inverse (MLI)) in most of the early wells. Careful re-interpretation of these logs using appropriate techniques and principles have resulted in significant improvement in net-to-gross estimation in the absence of neutron and density logs.
This paper aims at re-establishing the resourcefulness of microlog data in error reduction on estimated net to gross with a case study in ELJODA Field, Niger Delta Nigeria.
Application of the Excess Pressure Technique to Investigate Connectivity of Deepwater Turbidite Reservoirs, Offshore Nigeria
Authors: Jenakumo T. D , Ranasinghe M. K 
Published: July 2011

Abstract
The importance of communication between well pairs in deep water turbidite reservoirs, where water injection is the main reservoir drive mechanism cannot be overemphasized. Well costs continue to be on the rise and well redundancy due to lack of communication between injector-producer pair is undesirable. Compartmentalization within reservoirs - vertical, lateral or both is a common phenomenon, and its detection is increasingly becoming significant in reservoir characterization. Whereas the use of linear pressure trends to infer vertical connectivity or otherwise is very well established, well-to-well data evaluation is critical for assessing lateral connectivity.
In this work, residual pressure (commonly known as excess pressure) plots have been employed to evaluate connectivity between vertically stacked reservoirs which are otherwise assumed to connected under static conditions. We have tried to incorporate all available data types, including well logs, PVT sample analysis and geochemical interpretations prior to drawing conclusions on the risk of compartmentalization for each case. We have evaluated formation pressures and gradients from wells and compared the results against the accuracy of the wireline formation tester (WFT) tool.
The first set of reservoirs evaluated is from an Appraisal field where development wells are being planned. The results will be compared to the pre-production wells from the an Analogue fieldwhich has been producing for over five years now. This work will then try to establish whether the excess pressure plots from the Analogue field could have predicted some of the production observations that are seen today. And if so, comment on what an excess pressure threshold may be for this region. Both the Appraisal and Analogue fields lie the same block.
For the Appraisal field, this study is useful as a means of assessing the risk of intra-reservoir compartmentalization and provide an opportunity to optimize future development plans.
Avoiding Misleading Performance Predictions for a Reservoir System with Limited Production Data by the Application of Experimental Design Technology
Authors: Cyril Ogbalor , Peacock Anthony 
Published: July 2011

Abstract
The general aim of reservoir modelling is to provide a tool capable of generating reliable ranges of performance predictions on which to make development and investment decisions in a way that manages the recognised uncertainties associated with the development. The standard approach is to generate a range of static and dynamic models and parameters that capture the uncertainties, based on available sub-surface and surface information, correlations or engineering judgement.
Experimental design (ED) techniques are being increasing adopted as a method to consistently combine the uncertainty parameters and to construct a range of reservoir models. The standard ED approach is to adopt global changes to the range of input parameters and seek combinations that best reproduce the historical data. Calibrating the reservoir models to available historical performance data is a vital step in providing confidence on the predicted results. However, in situations with limited performance data, great care is needed to understand the implications of model calibration so as to avoid misleading prediction results.
Capillary Pressure Curves from Nuclear Magnetic Resonance Log Data in a Deepwater Turbidite Nigeria Field - A Comparison to Saturation Models from SCAL Drainage Capillary Pressure Curves
Authors: Arogun Olubunmi , Nwosu Chike 
Published: July 2011

Abstract
The DW Turbidite field in Deepwater Nigeria has limited SCAL data on drainage capillary pressure curves used, traditionally, in building saturation-height functions for application in 3D static and dynamic models.
An alternative approach to derive capillary pressure curves from Nuclear Magnetic Resonance (NMR) T2 distributions, developed by Volokitin et al, has been tested in one of the key reservoirs in the DW Turbidite North field and compared to mercury injected capillary pressure (MICP) data from a full-bore core across the reservoir.
The alternative approach relies on an underlying assumption that a relationship exists between porebody radius (as represented by the NMR T2 distribution) and pore-throat radius (which drives capillary behavior). An algorithm has been applied that uses a T2 cutoff such that the sum of the bound and moveable fluid spectra amplitudes matches the water porosity to correct for the presence of hydrocarbons. The hypothesis is the resulting relationship (between the NMR T2 distribution and pore-throat distribution) embedded within a proportionality parameter, κ.
The hypothesis was tested on the three key facies (CSA - Channel Storey Axis, CSM - Channel Storey Margin & ICTB - Inter-Channel Thin Beds) identified in the reservoir. Field-specific proportionality parameters were determined from which NMR T2 capillary pressure curves have been derived.
Comparison between the derived capillary pressure curves and the SCAL (MICP) data provide confidence that this technique can be applied in the absence of SCAL data.
Challenges and Remedy for Cementing of HPHT Wells in Nigerian Operation
Authors: Yetunde Shado , Ogbonna Joel 
Published: July 2011

Abstract
As hydrocarbons are being depleted from some formations, the search is on for greater reserves in difficult regions. Some wells are now drilled in more hostile downhole conditions, which include high temperature and high pressure. A well is considered to be high pressure and high temperature (HPHT) if the pressure exceeds 15000psi (1020 bar) and the temperature exceeds 300°F (149°C). The challenges created by these, make drilling and cementing in these regions difficult. The study reveals that in order to meet up with the challenges of HPHT drilling and cementing operations, issues such as effect of temperature and pressure, large stresses, degradation of set cement at elevated temperature, small ECD windows, efficient fluid design and displacement among others must be addressed for successful job execution and excellent job delivery.
The objective of the study therefore is to highlight various challenges associated with HPHT wells, the Best Practices that have been adopted in several HPHT wells and the way forward. This will provide a learning point for operators, researchers and other Engineering professionals especially for the emerging HPHT operations in Nigeria and Gulf of Guinea.
CO2 EOR and Sequestration in a Depleted Gas-condensate Reservoir: UKNS Case Study
Authors: Mogbo Obuekwe 
Published: July 2011

Abstract
This paper comprises a portion of a development study to investigate the applicability of CO2 for enhanced oil recovery and sequestration in a field in the central UKNS. The study focused on compositional simulations to predict the Minimum Miscibility Pressures, describe prognosed miscibility mechanisms and estimate incremental hydrocarbon recovery from full field simulations.
Depleted gas condensate fields are important targets for CO2 sequestration/EOR. Once depleted below the dew point, retrograde condensate is deposited in the pore system. CO2 injection in the depleted gas condensate reservoirs may allow enhanced gas recovery by liquid re-vaporization and reservoir re-pressurization or pressure maintenance.1 It is also noted that an accurate EOS fluid characterization is essential for CO2 miscible displacement, which is a composition-sensitive process. 2 As such, compositional modelling is preferred.
For the phenomenological stage of the study, 1D slimtube compositional simulation models were used to estimate the Minimum miscibility pressure (MMP) of representative fluids in the Oil and depleted gas condensate legs. Different grid-block sizes were used to consider the effect of numerical dispersion on the MMP. Subsequently, ID finescale block compositional simulation models were used to study and verify the multi-contact miscibility mechanism existent in the depleted condensate legs.
The 3D full field model is highly compartmentalized with nine different panels having separate PVT characteristics. Each panel has a 12 component Peng-Robinson equation of state which is conditioned to its individual fluid. CO2 injection for repressurisation is simulated up to and beyond MMP, contact miscibility is attained and gas cycling is implemented for incremental oil recovery. After EOR, production ends and injection is continued for estimation of the maximum amount of CO2 to be sequestered. Furthermore, typical economic analysis for CO2 EOR project justification is done. The results enabled correct investment decision making by showing that CO2 EOR is technically but not economically justified for this field.
Developing Petroleum Engineering Young Technical Professionals in Shell Nigeria – The Well Site Petroleum Engineer Model
Authors: Ebitu Sophia 
Published: July 2011

Abstract
The introduction of the "Drilling in the 90s" concept resulted in the loss of the Well Site Petroleum Engineer (WSPE) position on rigs, which hitherto was the generally accepted development format for graduate recruits in the Petroleum Engineering function in major IOCs through the ‘70s and ‘80s. A two-year stint as a WSPE on drilling and workover rigs was usually followed by development opportunities in one of the PE disciplines with an opportunity to grow into a PE technical professional. A review of job competence profiles performed around the middle of last decade among young to mid level Petroleum Engineering professionals showed deficiencies in skill levels due to limited exposures to field operations at the Young Technical Professional (YTP) level following the discontinuation of the programme; new joiners into the PE disciplines remained office based in respective asset or discipline teams, going into the field for visits to learn or witness specific drilling and field operations which usually focused around discipline interests and generally lacked structure, depth and the required levels of exposure to field operations. In order to address this problem, the WSPE programme was reinstated to bridge skill gaps by field exposure, thereby producing more competent YTPs prepared for growth up the PE career ladder. This paper presents a review of the competency gaps observed with the suspension of the WSPE programme and describes the WSPE & Field Exposure model adopted by Shell Nigeria, which is considered a key element in developing competent PE's through a structured exposure to the practical aspects of oilfield operations in the first two years of their career.