bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Analysis of Stick-Slip Motion of Drillstring While Drilling
Authors: Omojuwa E. , Osisanya S. , Ahmed R. 
Published: July 2011

Abstract
Drilling dynamic dysfunction condition occurs when dynamic forces in the drillstring cause very high stresses and fatigue or physical damage to the string and thus reduced bit performance or caused wellbore damage. These forces may generate from vibrations, shocks, oscillations, and BHA dynamic buckling. Failure of drillstring components due to torsional stresses are caused by torsional vibrations. This work investigates the response of drillstring to torsional vibrations through analysis on an elemental stepped-shaft drillstring model in a vibration damping medium. The work directs its analysis on the stick-slip motion, which is the most common form of torsional vibrations of drillstring while drilling.
The interaction between the wellbore and the drill-bit is identified in this research as the source of excitation, that is, as the downhole vibratory source. Hence, the exciting torque is derived from the resolution of forces and reactions at wellbore-drill-bit contact. The response equations obtained from theories of mechanical vibrations and mathematical principles in this research are in two forms: the transient state and steady-state responses. This work is different from other similar works where only the steady-state response is presented. A computer program was developed and tested with suitable drilling data to solve the response equations. Extensive vibration analysis was carried out using the program to examine the responses of different forms of excitations. Beside this, the effectiveness of a torsional vibration absorber was discussed with regards to reduction of drillstring oscillations. The torque-rectification control (TRC) system was introduced and analyzed as regards its use for automatic vibration control during drilling. Simulation results from the computer program show the impacts of torsional vibration absorber and TRC system. In conclusion, recommendations are given based on practical solutions to the problems of drillstring vibrations and from the findings of this project.
Economic Analysis of GTP, GTL, CNG, NGH for Offshore Gas Development in Nigeria
Authors: Osokogwu U. , Ademujimi M. , Ajienka J. A 
Published: July 2011

ABSTRACT
Natural gas consumption is globally increasing as it is one of the most important energy resources today. Its consumption is accelerated because of the growing environmental concern. To respond to this world demand, the alternatives of gas usages and technologies should be investigated and compared in terms of economic feasibility. The economic viability of Gas-to-Liquid (GTL), Gas-to-Power (GTP), Compressed Natural Gas (CNG) and Natural Gas Hydrates (NGH) depend on the following factors namely; Capital expenditures (Capex), Operating expenditures (Opex), Prices (natural gas price), Net present value (NPV), profitability index, internal rate of return and Payback time. From the above mentioned factors, at 15% discount rate, CNG has NPV of $16.2 billion, IRR of 54%, profitability index of 7.2 and payback time of 1year and 3 months. GTP has a negative NPV (indicating loss), IRR of 54%, profitability index of 0.8 and payback period 3 years and six months. GTL has NPV of $6.5 billion, IRR of 50%, profitability index of 2.2 and payback period of lyear and 3 months. NGH has NPV of $7.0 billion, IRR of 42%, profitability index of 1.1, payback period of 2 years and 4 months. These results show that Compressed Natural gas is preferred to others because CNG has the highest net present value (NPV), highest profit to investment ratio, highest internal rate of return, lowest initial expenditure (CAPEX) and a shorter payback period. From the economic aspect of this work compressed natural gas is the most economical and viable.
Economics of Monetisation of Stranded Gases in Nigeria
Authors: Joseph A. , Umeogu O. , Ajienka J. A. , Ikeh L 
Published: July 2011

ABSTRACT
Nigeria is endowed with abundant natural gas reserves. Over the years, pipelines and LNG have been the two major means of gas transportation and hence, the main utilisation media in the world. However, in some areas in Nigeria, reserves are found in difficult locations and in quantities that make their exploitation through these conventional ways techno-economically unfeasible. The goal of this study is to investigate with the aid of several economic indicators, risk analysis and sensitivity analysis; the different ways in which natural gas can be employed economically as an energy resource for both power generation and road transport. The analysis covers both the natural gas use as a Power generator, fuel - Compressed (CNG) or Liquefied (LNG) - and as a feedstock to produce other fuels - synthetic (GTL) Naphtha and Diesel (F-T diesel), and Liquefied Petroleum Gas (LPG). After a thorough scrutiny of the various options, the GTL-incorporated Power Generation with 70% steam supply was found to be the most economical and environmentally friendly option for the energy generation. If properly harnessed, it could generate huge potential revenue for the government, resolve the epileptic power supply problem and create employment opportunities.
Effect of Water-Cut on Sandstone Strength and Its Implications in Sand Production Prediction
Authors: Joseph A. , Ilozue C. T , Osokogwu U , Ajienka J. A. 
Published: July 2011

ABSTRACT
Production of water is inevitable from reservoirs particularly in aged fields. Water is very useful for efficient reservoir management but could be a nuisance when it does not contribute to hydrocarbon production and cause diverse problems such as corrosion, sand production, etc, in a well. High water cut increases the potential of sand production risks. Several mechanisms of sanding, sand control models and measures exist in the industry to ensure safe operation of facilities. In this work, series of laboratory triaxial compressible strength tests on different core samples was performed to investigate and quantify the effect of water-cut on sandstone strength and sand production. The tri-axial compressive strength tests were performed under in-situ confining pressures. The samples were initially 100% saturated with brine at some time and other times the water-oil saturations were varied. The results showed that the effect of water-cut on sandstone strength and sand production is very significant for all sandstones tested. Also, strength reduction is more significant for 100% water saturated samples than samples with less water saturation for all samples. Hence, water saturation-induced rock strength reduction is the most significant factor governing sand production. Although, failure of rock is pre-requisite for sand production, the failure does not always lead to sand production
Effectiveness of Safe Welding Systems in Eliminating Shut-in on Offshore Oil and Gas Platforms
Authors: Hutchinson Todd , Oyeyinka Dotun 
Published: July 2011

Abstract
Installations used in oil and gas industry are usually large metal structures. These structures are affected by environmental factors, and are in need of constant maintenance and repair.
HAZTEC, which stands for Hazardous Atmospheric Zone Telemetry for Environmental Control, is an automated Monitoring and Control System that utilizes a custom automated program and a Safe Welding Enclosure. Together these elements create an isolated safe zone around the work area, allowing hot work to take place in hazardous-rated locations by monitoring and controlling all hot works.
Each HAZTEC Safe Welding Enclosure is custom-designed and built to fit each particular situation without disrupting or altering the area or existing equipment. The HAZTEC enclosure is built using fire-retardant wood, and each element of the HAZTEC enclosure is constructed according to OSHA and MMS standards. The flooring of the HAZTEC enclosure is further lined with a fire-resistant blanket, rated at a maximum of 3,500 degrees Fahrenheit, and a layer of light-gauge stainless steel that dissipates heat by dispersing slag and sparks. This process and material may also be used on walls or other areas of the enclosure where heavy overspray from welding or metal washing may occur.

Before any hot work begins, all openings of the HAZTEC enclosure are sealed, filtered, or closed to create a positive pressure over balance in the interior of the enclosure, protecting the inside atmosphere from exposure to the potential dangers of the outside atmosphere. A minimum positive pressure differentia water column is maintained and monitored inside the enclosure throughout the hot work procedure. A filtered-air discharge outlet allows smoke to vent while maintaining no less than the minimum requirement of the positive pressure over balance.
The overall benefits of using the HAZTEC enclosure include retained production, optimized scheduling, safety and shared tasks.
Efficient Reservoir and Production Management "LCEEM and CEEM Approach"
Authors: Biu Victor. T. , Buduka Stanley , Prince Wachuku 
Published: July 2011

Abstract
Once new fields are discovered, ensuring maximum recovery of probable reserve before abandonment is the focal point of sound reservoir and production management practice.
Efficient reservoir and production management practice involves the use of advanced technology such as commercial, local and in-house software, highly skilled human resources, real time analysis, adequate and consistent multi-disciplinary reservoir to well monitoring approach on subsurface and surface facility bottlenecks for optimal field development. Nevertheless limited availability of advanced technology does not potent failure for successful optimization of any reserve, especially in marginal field development; however full integration of available human resources and consistent monitoring remained the critical driving factor for reserve optimization. This paper presents a comprehensive analysis of CEEM and LCEEM which involve interdisciplinary and consistent daily well-reservoir and field monitoring practice with design PRMP that will help to maximize well-reservoir-field potential. The entire process whether LCEEM and CEEM is recycle, hence a monitoring check valve and flexible well – reservoir management plan is necessary.
The LCEEM and CEEM shows that creating a performance check box and several scenario chart remains a key monitoring tool for well-reservoir-field production optimization and reserve maximization.
Energy Resources in Africa: Curse or Blessing?
Authors: Odizuru-Abangwu I. N 
Published: July 2011

Abstract
The African continent is blessed with abundant natural resources and specifically, significant energy resources but Africa has the greatest energy challenge in the world. Why is that and what can be done about it? Is Africa under a "resource curse"? This article explores the concept of "resource curse" and its implication for the continent of Africa.
Africa currently has 127.7 thousand million barrels of proved oil reserves, representing 10% of the total world oil reserves. The continent is the 3rd largest oil producer in the world, representing 12% of world oil production in 2009 but only utilizing 3.7% of it. This typifies the current situation in the continent whereby they are large resource holders and producers, but very poor resource users. The direct relationship between energy utilization and economic development is further explained in this article, buttressing the strategic nature of the energy sector in the development of Africa.
Other unique opportunities are explored in this article including renewable energy resources such as solar and biomass which can potentially turn around the energy dynamics in Africa. It also explores the unique challenges facing energy utilization in Africa including poor infrastructure, environmental concerns as well as political and leadership challenges.
Evaluation of Horizontal Well Completion and Performance Efficiency Using a Visual Basic Software – H-WELLEFF
Authors: Olu-Akinyemi E. G. , Ajienka J. A. 
Published: July 2011

Abstract
Horizontal wells have been drilled for over two decades, because of their ability to exploit tight reservoirs, thin reservoirs, discontinuous reservoirs, naturally fractured reservoirs and the need to minimize water and gas coning/cusping. In general, horizontal wells lead to increased productivity due to a greater surface area contact with the reservoir. This research work used a visual basic software H-WELLEFF to calculate the various indicators used in the industry for evaluating horizontal well completion and performance efficiency. These indicators are Analytical PI's, actual PI from welltest data, WIQI and FE. The software breaks the skin down into mechanical skin and pseudo-completion skin and calculates the percentage damage (reduction in efficiency) due to each of these skin factors. Also Case studies were carried out to see how the various indicators respond to change in factors that contribute to the total skin.
H-WELLEFF presents a good tool for calculating horizontal well efficiency and also for observing the trend of productivity index and damage over time.
Facies-Based Saturation Modeling—Bonga Field
Authors: Kalu E. C. , Arogun O. O. , Pirmez C. P. 
Published: July 2011

Abstract
The initial Bonga field development was based on a "green field" integrated saturation model using Gulf of Mexico (GoM) data as analogue. In an earlier revision of the Field Development Plan, the relative permeability and capillary pressure models were based on steady-state and centrifuge special core analysis (SCAL) experiments from a few Bonga Main wells and also integrating GoM data. The saturation modeling was dependent on permeability classes (intended to be, but not explicitly representative of the facies). As production continued over the years, several attempts have been made at history-matching the observed performance history of the reservoirs that constitute the Bonga field. The results indicate that a review of some of the input parameters including the relative permeability and capillary pressure model are required to obtain a reasonable history match of the reservoir performance.
The predominant facies types in Bonga field include Channel Storey Axis (CSA), Channel Storey Margin (CSM) and Inter-channel Thin Beds (ICTB). A relationship was observed between the raw SCAL data and the different facies classes from detailed core description. Current production and recent drilling/logging information coupled with 4D seismic monitor indicate preferential sweep from some of the facies. This may have a significant impact on the ability to maximize recovery from the various facies in the reservoirs.
This study focuses on developing a facies-dependent saturation model that honors the current understanding of the waterflood performance of Bonga reservoirs. Good history-matched, robust and fit-for-purpose models were obtained using this methodology. This has led to better evaluation of the recovery efficiency and flood pattern of the field which has been used to support further field development options and optimize production from existing wells.
Field Case Deepwater Development Wells Clean-up and Testing
Authors: Onyeanuna Chinedu , Marpaung Fivman 
Published: July 2011

Abstract
This paper presents the experiences of well clean-up operations carried out in the development wells of Akpo deepwater field.
Akpo is located 135 km offshore Nigeria in 1400 m of water depth. The reservoirs consist of faulted, unconsolidated, turbiditic channel and lobe sands with complex architecture. The fluids in each reservoir are near-critical. The field is currently producing about 175,000 barrels of condensates per day.
Current sand control techniques are Frac-Pack (FP), Stand Alone Screen (SAS) and Expandable Screen (ES).
Early data acquisition during well clean-ups was essential in other to optimise the development strategy, ensure a production ramp-up in line with expectation and reduce remaining uncertainties which were mainly linked to sand communication within channel complexes, fluid behaviour, and faults behaviour (seal or conduit).
The paper covers the clean-up design, execution, operations monitoring, data acquisition, and fluid sampling, along with the challenges and constraints encountered in the process for the different wells.
It describes how the challenge of hydrates formation, exacerbated by the deepwater environment and peculiar nature of the reservoir fluid, was handled to ensure successful well clean-ups. It also gives an example on how the early data acquisition program impacted important field development decisions.
Field Development and Optimization Strategy of a Giant Gas Reservoir in the Gbaran-Ubie Node
Authors: Cordelia Ikpera , Esta Eleluwor 
Published: July 2011

Abstract
The XON field is one of the five fields in the Gbaran-Ubie node to supply gas to Nigeria Liquified Natural Gas and is a field case history to illustrate the techniques and benefits of field development optimization right from initial field optimization to well delivery.
The XON AB4000X reservoir is one of the largest Non Associated Gas reservoir in SPDC and is expected to provide more than half the gas required for Gbaran Central Processing Facility capacity of 1Bscf.
Gas reserves from the 2003 Field review went down from 1.6 Tcf to 1.25 Tcf post the drilling of XON 7 and forecast based on new volumes indicate that the planned total reservoir offtake of 500 MMScf/d (100 MMScf/d per 5 gas producer planned for the reservoir) will only be sustained for 3 years instead of 5+ years. Following this, it became necessary to accurately estimate the Gas Initially In Place(GIIP), Ultimate Recovery (UR) and also provide an optimum development plan for this reservoir based on the new available data.
An optimisation optimization team was put in place to build new static and dynamic models based on new available data to be used for:
Accurately estimate in place volumes and UR Optimise expected reserves the Reservoir Development Plan Support drilling campaign
The optimization optimization results have led to increase in expectation GIIP to 2.03 Tcf, represent a 22% increase over the 2003 Field Review and a 63% over the 2005 estimate. The CIIP increased to 106.0 MMstb, representing a 23% over the 2003 FR estimate. Total gas recovery has also increase to 1.26 Tcf which is about 20% from 2003 Field Review (FR). Production rates increased from 100 to 150 MMScf and compression scope of about 500 Bscf to further add value to the filed development.
Most of the wells were delivered as top quartile wells due to collaboration between the asset, project and well engineering teams.
Foam Cementing Design and Application: A Cure for Low Gradient-Associated Problems in Deepwater Operations in the Gulf of Guinea
Authors: Taiwo Oyetade , Ogbonna Joel 
Published: July 2011

Abstract
Cementing in the deepwater environment could pose some challenges because deepwater formations are buried with much reduced overburden. This gives a lower fracture gradient resistance than the same formation at the same sedimentary depth onshore. In situations like this, the relative density-to-compressive strength ratio of the cement slurry used for zonal isolation becomes critical; hence foamed cement helps to address these challenges. Slurries ranging in density from 4 to 15 lb/gal can be prepared with foamed cement. Foamed cement can be used at temperatures from 28 to 600ºF (82 to 1112ºC). In this project, Laboratory analysis of foamed and unfoamed cement at different slurry weights was determined and compressive strength results were evaluated. Test results indicated that the compressive strength for 12.0 ppg unfoamed cement after 24 hours was 254psi while the foamed slurry of 11.8 ppg gave compressive strength of 1050 psi after 24hours. It is imperative to note that conventional slurries at higher slurry weight that will give higher compressive strengths will fracture weak formations and not recommended. Foamed cement slurry offers a comparative advantage of enhanced mud removal, good ductility, fluid loss and gas migration control, insulation properties and excellent compressive strength development at low slurry density. However, the disadvantage of foamed cement is the need for specialized cementing equipment for both field application and laboratory testing, nevertheless, the associated benefits arising from application of foam cement in deep water weak formation environments makes it a slurry of choice in locations such as Gulf of Guinea.
Formation Pressure While Drilling (FPWD) Tool Application in Reservoir Management–Case Study on Tetra-Mega Field, NYC Nigeria
Authors: Duru Elizabeth C. , Liu Forrest , De Santo Ilaria , Odewoye Oluwatosin 
Published: July 2011

Abstract
The Tetra-Mega field development project, operated by NYC Company, has expanded since its onset a number of years ago. The daily plateau production of this field is expected to be high based on its huge proven reserves. To maximize the value of this hydrocarbon asset, employing the well construction process of drilling wells that can achieve maximum production potential is highly recommended. The use of technologies that enable optimal and precise wellbore positioning, increased well lengths, and enhanced understanding of reservoir characteristics is crucial to the successful development of the field. For this reason the Formation Pressure While Drilling (FPWD) tool has been consistently deployed in the Tetra-Mega field. The tool's capability of acquiring good quality formation pressures and fluid mobilities in a timely manner, while drilling complex well architectures in tough drilling environments, has established its position as a valuable tool for reservoir management applications.
A peculiar approach introduced here focuses on performing well-to-well reservoir evaluation studies, prior to the commencement of field development studies. Based on this approach, the value of the information provided by the FPWD tool to Tetra-Mega field development is the main focus of this paper. Since its introduction to the field a few years ago, the tool has been efficiently used to acquire good quality formation evaluation (FE) data in real-time. Well-to-well evaluation studies in this field involved the use of FE data to do a pressure profile of the field so as to identify its different reservoirs. Further analysis into individual sands investigated pressure continuity, reservoir compartmentalization, potential thief zones and fluid identification. This enabled a better understanding of the reservoir behavior, and thus optimized well placement and completion strategies. NYC was able to make immediate plans and take actions to address specific problems and opportunities in the reservoir development of this field. Additionally, acquiring formation evaluation data during the drilling phase of the well is valuable to NYC in saving substantial rig time and cost.