bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Modelling of a Mature Field in The Niger Delta Basin: The Benefits of Integrating Production Data for Uncertainty Management
Authors: Adenaiye Olaniyi , Jude-Ofia Ifeyinwa , Adekoya Oluwaseyi , Kirchner Andreas , Nwonodi Chike , Campero Manuel , Anosike Ebere 
Published: July 2014

Abstract
This paper highlights the importance and benefits of integrating both static and dynamic data, in defining the range of structural uncertainties in a mature field in the Niger Delta Basin. Appropriate management of static and dynamic subsurface uncertainties enhances the prediction of the subsurface and improves the quality of key development decisions. Typically, structural uncertainty ranges are mostly associated with seismic and geologic data (e.g., seismic loop pick, fault positioning/geometry and velocity model for time-to-depth conversion etc.), while dynamic data (e.g., production data) are rarely considered.
To model the mature ‘A-sands’ in Craig field, a subsurface uncertainty matrix was generated consisting of all identified uncertainties as well as their ranges. Low, base and high case structural and static models were built in Petrel for the ‘A-sands’ and then transferred to a dynamic simulator for history matching and to assess impact of these uncertainties on ultimate recovery. Experimental Design (ED) technique was used during dynamic modelling to integrate all the uncertainty parameters with the aim of selecting the best history-match realizations that will be used for forecasting.
Initial results obtained from ED indicated acceptable history matches for the base case model, while the quality of matches for low and high case models were poor / unacceptable, suggesting a need to review the uncertainty ranges. This was further supported by a narrow range of recoveries obtained from DCA (decline curve analyses) for the producing conduits in the reservoirs. Also considering the maturity of the field (over 70 wells drilled, with Np over 30% of the oil in-place), it was pertinent to revisit the ranges
Based on these informations, the uncertainty ranges were reviewed, with focus on those that have the largest impact on history match results. This paper focuses on the review carried out on the structural uncertainty - which has the largest impact on history match results - leading to smaller ranges of structural uncertainties. The reduced depth uncertainty values resulted in static models and volumetric estimates that supported historic production data for the reservoirs, producing much improved history matches.
Use of Centrifuge to Determine Connate Water and Capillary Pressure from Unconsolidated Cores
Authors: Ubani Ebenezer Chikwendu , Oriji Boniface Aleruchi 
Published: July 2014

Abstract
The centrifuge has been found to be a useful tool for determining, capillary pressure and connote water saturation from unconsolidated cores. The method has also demonstrated the virtue of simplicity, reproducibility, speed and good correlation with other methods. Hence, this study is in response to the need of providing practical experimental evidence to justify the use of this method in preference to other methods (Porous plate and Mercury injection Methods). The samples for this study are cores taken from different fields located onshore and offshore of the Niger Delta. Their porosity ranges from 17-35% and permeability from 100-3500 md. These unconsolidated and friable sandstones cores are susceptible to deformation grain re-arrangement and grain losses, while vuggy cores are susceptible to surface drainage. The severity of these occurrences were minimized by drilling the samples with liquid nitrogen, mounting the samples with tin sleeve and protecting both ends with a pairs of screens of 100 and 135 U.s mesh size. The capillary pressure and corresponding saturation data obtained from the experiment are displayed in the tables. Also capillary pressure curves were obtained to show the relationship between the capillary pressure and saturation for each of the sample tested. From the capillary pressure curves, the end point saturation of the primary drainage process of the sample show low irreducible water saturation (Swi) and high permeability. The centrifuge method is however limited because numerical differentiation and integration of functions defined by the measured data are needed; and the assumption of 100% wetting - phase saturation (i.e. Pc = 0) at the sample bottom may not be valid beyond a certain rotational speed. The measured data may need interpolation to avoid oscillation in the Solution. This interpolation however only represents "Smoothing" of the experimental curve which is always done for experimental data. Application of the centrifuge procedure to unconsolidated sand stones provide results, which are in good agreement with those obtained from other techniques.
Experimental Determination of Relative Permeability from Unconsolidated Core Samples of The Niger Delta
Authors: Ubani C. E , Ikiensikimama S. S , Onyekonwu M. O 
Published: July 2014

Abstract
A procedure have been developed and tested for measurement and evaluation of water-oil relative permeability characteristics from unconsolidated core samples; in an unsteady state displacement experiment. In this work a simple core flooding experiment was designed, with emphases on the rate of injection, critical velocity, brine-rock compatibility, pressure response of the core sample and net over burden. This procedure proposed here besides being fast and cheap, presents the advantages of permitting the displacement to be conducted at pre-determined rates more typical to that of the reservoirs.
This research work is in response to: (1) the need of practical experimental evidence to justify the use of unsteady state method in preference to other methods. (2) The need to obtain relative permeability data from unconsolidated formation of the Niger Delta, which could be used to correlate other un-cored formation in the region.
The samples for this analysis were taken from seven (7) different locations representing the depositional belt of Niger Delta. Their porosity and permeability ranges from 18-34% and 100-20,000md respectively. These unconsolidated and friable sand stones are susceptible to deformations, grain re-arrangement, grain losses and surface drainage. The severity of these occurrences were minimized by drilling the plugs with liquid nitrogen, mounting the plugs with tin sleeve and protecting both ends of the plugs with a pair of screen of 100 and 135 us mesh size.
Also, it was possible to avoid potential problem of EOR'S such as fines mobilization, precipitation, scaling, clay swelling and compatibility of other chemical flooding agents.
This method involves performing low rate displacement of brine with oil and oil with brine and measurement of liquid permeability at irreducible – water and residual – oil end point saturation.
Except for the added provision of stopping, restarting and reversing the flood after end point have been reached, the pressure drop across the core is measured externally, between the inlet and out let of the system.
The measurement and analytical interpretation of the experimental variable, using a combination of the modified Darcy equation and our developed semi-empirical model make for quick calculation of relative permeability from the unconsolidated core samples.
Remote Pipeline Pressure Monitoring Using Low Power Wireless Transmission
Authors: Idachaba Francis Enejo , Okuns Godwin , Wokoma Esther 
Published: July 2014

Abstract
Manual data acquisition of pressure readings in order to build a static pipeline hydraulic profile for a pipeline network, increases the security exposure of personnel, logistics cost with the attendant delay in determining and reporting pipeline pressure used in Hydrocarbon accounting, making it prone to errors, inaccurate and unrepresentative of the actual situations on the network. This paper presents results of a wireless pipeline real time (RT) pressure monitoring system using low power wireless transmitters installed at selected pressure points on the pipeline networks located in remote areas of SPDC operations. The system utilizes secure wireless transmission and special encryption systems designed to protect the data transmission from interference and degradation. The system achieved a data transmission over a 10km range from a pipeline pressure point to the gateway, with a battery life of over 6 months. Longer battery life durations can be achieved by the deployment of exception based reporting. The system provides a means of monitoring the pipeline pressure and thus enables the development of a dynamic pipeline pressure profile for the monitored pipelines. The data from the system can also be used with special algorithms to monitor the pipeline for leaks. The system versatility has also been tested as means of collating vital well data to a data concentrator enroute an enterprise intranet
Fracture Gradient Estimation in the Niger Delta – A Practical and Statistical Approach
Authors: Reginald-Ugwuadu Onyinye G , Alabi Tunde I , Eze Joy O , Ebisike Richard C 
Published: July 2014

Abstract
The safety of lives, assets and environment continue to remain the key challenges facing the oil and gas industry in its drilling and completions operations. One important factor in ensuring that wells are drilled and completed to desired depth is the formation strength or pressure containment of the shoe after a cement job to help ensure zonal isolation around the casing shoe as well as pressure containment at the shoe while drilling the next hole section.
The knowledge of formation strength estimate is essential to enhance proper planning of these wells and drilling to desired total depth, and forestalls, or at the least minimises the likelihood of not drilling to optimum depth or incomplete evaluation of the prospect.
Additionally, other key well construction aspects such as determining optimum mud weight required for borehole stability especially in deviated wells; optimum casing setting depth selection where the pore pressure profile below the shoe is known are highly dependent on accurate knowledge of the formation strength estimate.
Historically, there have been several methods to predict fracture gradient, most and/or a combination of the methods have been adopted by many operating companies. Several operating companies have drilled so many wells in certain fields such that formation integrity test data (Leak-Off test and Limit tests) exist for the several formations that have been traversed by these wells. The industry has great reliance on the use of offset correlating wells data in well planning and designs.
In this study, several Leak-Off (LOT) test data from different wells across fields in the Niger Delta were used to determine a correlation between increase in formation strength and depth. A practical statistical method is used to derive equations for fracture gradient estimation in Onshore and Swamp Niger Delta using existing wells leak off test database. Limited data for the shallow offshore were also used to derive an equation which has proven to work. These set of equations can be used to estimate fracture gradient expected in the formations across these and nearby fields. The formation leak-off gradient has been assumed to be an approximate representation of the formation strength or formation breakdown gradient. Since the latter is always greater, the use of the former for well design purposes provides an additional factor of safety.
Optimizing Sand Control Design Using Sand Screen Retention Testing
Authors: Agunloye Ehimhen , Utunedi Erome 
Published: July 2014

Abstract
Sand retention tests have been widely accepted as one of the methods of sizing screens for Stand Alone Screens (SAS) in open hole completions. The results of such tests are, however, highly dependent on the experimental conditions and prone to artefacts; small and apparently innocuous changes to the test conditions can cause wide variations in results1. Furthermore it may require several tests performed with different screen and test sands to adequately select the appropriate screen size that would prevent plugging and sand production. When done correctly sand retention tests have proven to be an optimum method for SAS sizing.
Several mathematical models have also been developed for screen sizing using series of laboratory data but the applicability of these models to other reservoirs, different from the test reservoir, is questionable.
This paper discusses screen selection for a highly non-uniform unconsolidated reservoir in a field in the Gulf of Guinea based on sand screen retention test using screen sizes pre-selected on Coberly's criterion. Coberly's criterion is extensively used in the industry for screen only design. It is however still subject to debate most especially with respect to sand control failure due to plugged screens, or catastrophic failures due to screen erosion.
The optimization work goes further to compare the results of the screen retention test in the laboratory against published numerical models, by applying these models to the field in question. From the results, a detailed experimental workflow for sand control design and screen selection for unconsolidated reservoirs has been developed for the Region; this also includes the sand screen retention testing applicability and requirements for a successful design.
Application of Neural Networks in Developing an Empirical Oil Recovery Factor Equation for Water Drive Niger Delta Reservoirs
Authors: Okpere Adrian , Njoku Chukwueke 
Published: July 2014

Abstract
The importance of estimation of reservoir recovery factors to a high level of accuracy cannot be overstated in field appraisal or development. Estimation of recovery factor depends on a combination of static and dynamic parameters which in themselves come with a lot of uncertainties and in most cases there is insufficient or poor quality data to enable effective and accurate estimation of a recovery factor. Empirically derived recovery factor equations have been developed for cases were there is limited data to be able to get an estimate of recovery factor.
Empirical Oil Recovery Regression Equations were initially developed by the American Petroleum Institute (API) on sandstone reservoirs in the United States and adapted by Arps, popularly called Arps equation. Since then numerous other equations have been developed but there has been lack of a robust equation developed specifically for the Niger Delta environment, although Arps equation has been tested on Niger Delta Reservoirs and work done shows it can be used in the environment although with some caution.
This paper shows a new approach to developing an Empirical Oil Recovery Factor Equation for water drive reservoirs in the Niger Delta using reservoir characterization and Artificial Neural Networks (ANN). The ANN is a mathematical model inspired by biological neural networks. In this approach reservoir recovery factors from mature water drive reservoirs in the Niger Delta Region were characterized based on facies type and properties into groups to draw inferences on similar reservoir types tied to different recovery factor ranges. The data from selected group set was randomly divided into three parts, of which 60% was used for training, 20% for validation, and 20% for testing. The final ANN model for particular groups was tested for robustness against the original empirical correlation developed by API.
Modelling Seismic Velocities & Pressure Cells for Pre-Drill Pore Pressure Prediction and Application in Development Wells in Nigerian Deepwater Turbidites
Authors: Wodu Ebimobowei K , Sarker Ritu , Itua Osazua J. 
Published: July 2014

Abstract
The use of quantitative techniques in the evaluation of pore and fracture pressures across entire well path plays an important role in successful well delivery. The ability to correctly predict geo-pressures before drilling and manage them during drilling is a critical success factor to safe drilling of wells and cost reduction especially in deepwater environments.
Compressional velocities have been used to provide indirect estimate of pressures prior to drilling; the method is well established Rodney Littleton et al, (74487). Vertical effective stress-Compressional velocity models in offset wells when fitted with empirical models can be applied to calibrated seismic velocities in prospect well locations to predict pore pressures. The accuracy of this method however depends on factors not limited to geology, compaction trend, seismic anisotropy, consistent velocity picking/gridding, input to gathers, over pressure prediction, etc. To raise the confidence level in the seismic based prediction, a simple yet pragmatic methodology has being used to demonstrate how combining velocity based pressures with pressure cell modeling can yield formation pressures across entire well paths with much higher degree of certainty.
This work therefore discusses a study done on a deep water Nigeria field; where Seismic velocities have been used to predict pore pressures. The outcome was combined with pressure cell based methodology (standard method for pore pressure prediction in sands) to reduce the inherent uncertainties in sand pore pressure predictions. The results shared in this paper have already been used in effective design of several deep water wells in offshore Nigeria.
Divergent and Convergent Thinking Approach: A More Integrated Method to Pressure Transient Analysis and Interpretation
Authors: Oguntoye Patrick , Okporiri Cyril , Akinyede Esther , Afoama Ebuka , Ikwan Ukauku 
Published: July 2014

Abstract
The significance of pressure transient analysis has grown over the years, as it has become a key source of subsurface information needed both for surveillance and effective reservoir management. However, it could be quite challenging especially in complex analysis and having an interpretation representative of the reservoir system could be daunting amidst widely varying uncertainties, data quality, limited geological and engineering data. It is therefore quite imperative that the analysis and interpretation approach be robust enough in order to give information that is representative of the reservoir in consideration.
While the objectives for acquiring well test data in the first place varies over the life of a field, the interpretation methodology remains practically the same and it is the focus of this paper to give a more practical approach to PTA interpretation for a field at its developmental stage and help resolve one of the problems associated with PTA interpretation which is having a well defined, logical and consistent interpretation approach across different interpreters.
This paper presents the application of a divergent thinking approach in well test analysis using multi scenario modeling and then following logical steps using all available geological and engineering data to converge to the most likely interpretation. The application of this approach is discussed using three different fields in the Niger Delta region of Nigeria as case studies which have been carefully selected from a field with little less than 2 years of consistent production (relatively new) to fields with an average production of about 25 years to reflect different level of understanding of the reservoir system based on available data. Analysis was carried out on well test data acquired from these fields using SAPHIR software by KAPPA. The results obtained show that regardless of what model were chosen, a relatively good model match can be obtained for the available data and except all available geological and engineering data are applied in an integrated manner, a non-representative model can be chosen for the said reservoir further leading to more uncertainties.
Globalization of Black Oil PVT Correlations
Authors: Kanu Austin Ukwu , Ikiensikimama Sunday Sunday 
Published: July 2014

Abstract
It is a general consensus that the very many varying black oil PVT correlations currently in use in the petroleum industry have failed to adequately predict the behavioural course of different black oil system from diverse regions. So, this study seeks to globalize existing black oil PVT correaltions by removing the local constraints imposed on them and as well improve their predictive capabilities for all oil compositions, reservoir temperature and pressure. The basic concept is to find a mutiplier and a shift parameters that would adjust a specifed PVT correlation to match measured PVT labortory data. It is concluded that the combined effect of the multiplier and shift parameters can compel all the existing correlations to trace a common path which represents the correct description of any oil system irrespective of location or region to accurately match measured PVT data.
Seasonal Trends in Nonstructural Carbohydrates in Cool‐ and Warm‐season Grasses
Authors: Jensen Kevin B. , Harrison Phil , Chatterton N. Jerry , Bushman B. Shaun , Creech J. Earl 
Published: July 2014

ABSTRACTWhile increases in nonstructural carbohydrate (NSC) content of forages are generally considered advantageous, there are times during the growing season when grasses with increased NSC levels may not be the desired forage, particularly for horses (Equus caballus). Hence, there is a need to better understand carbohydrate trends across the growing season. This study evaluated 15 grass species from May to August (growth phase‐1) and from September to November (growth phase‐2) in northern Utah during 2004 and 2005 for sugars, fructans, water‐soluble carbohydrates (WSC), starch, and total nonstructural carbohydrates (TNC). Sampling date and species had a significant effect on carbohydrate concentrations in cool‐season grasses, with a lesser effect on warm‐season grasses. Warm‐season grasses had uniformly lesser sugar, fructan, WSC, and TNC concentrations than cool‐season grasses; however, they had dry‐matter yields (DMY) greater than cool‐season grasses in August. If high TNC forage is desired, then, of the grasses examined, perennial ryegrass and timothy would be the species of choice for irrigated pastures. However, if forage lower in TNC is desired, then meadow bromegrass, which had the least overall sugar, fructan, WSC, starch, and TNC concentrations, would be best. On dryland pastures, Sandberg bluegrass (Poa secunda J. Presl.) and tall wheatgrass (Thinopyrum ponticum (Podp.) Z.‐W. Liu and R.‐C. Wang) had the least overall forage carbohydrates, while crested wheatgrass (Agropyron cristatum (L.) Gaertn.) maintained its carbohydrate concentrations better on 3 August. Fructan concentrations contributed 54, 47, and 42% of the total WSC concentrations in perennial ryegrass, crested wheatgrass, and Kentucky bluegrass, respectively, compared to 26 and 29% in tall wheatgrass and creeping meadow foxtail, respectively. Water‐soluble carbohydrates accounted for between 86 and 91% of the total TNC concentration in the cool‐season grasses compared to 75 to 80% in the warm‐season grasses.