bluuebunny/crossref_metadata_2025 huggingface dataset:
3D Pore Space Characterization for Classification of Flow Properties of Reservoir Rocks
Authors: Otiede D. O , Wu K , Olafuyi O. A
Published: August 2012

A method of obtaining petrophysical and single- and multi-phase properties of reservoir rocks without the use of Special Core Analysis techniques is presented. The approached involved three-dimensional image reconstruction from 2-D images of reservoir rocks obtained by micro-computer tomography. Two rock samples were used for the study, namely, a Carbonate-28 rock sample and a Castlegate sandstone. The Carbonate-28 sample was studied at two different resolutions of 1.33 microns and 0.133 microns; while the Castlegate sandstone was investigated at a resolution of 5.6 microns. Network models were extracted from the pore architecture models (PAMs) obtained from the 3-D image reconstruction. The geometrical and topological properties of the extracted networks were then studied; this was followed by numerical flow simulation to derive the single- and multi-phase properties of the rocks studied. The geometrical and topological characteristics of the reconstructed pore architecture models were analysed with the aid of a pore analysis software tool (PAT). The main geometry and topological – characteristics studied included the pore size distribution, pore shape factor, and pore connectivity (in terms of coordination number and specific Euler number). Single- and multi-phase flow properties, namely: average porosity, absolute permeability, relative permeability, and capillary pressure, were measured for all three structures. Results obtained showed that pore size connectivity, and pore size distribution had the greatest impact on flow properties. Specifically, it was observed that the larger the interconnected pore sizes, the greater the absolute permeability; whereas observed permeability was low for interconnectedness involving smaller pores, even with high pore connectivity (that is, favorable specific Euler number). These results can be applied in reservoir characterization to generate flow properties for reservoir rocks; which can be utilized in reservoir simulation and reservoir engineering calculations.
Improved Analytical Model for Predicting Field Production Performance in Vertical Multiphase Flow in Pipes using MATLAB: A Case Study…Part II
Authors: Sukubo I. A. , Igboanugo A. C.
Published: August 2012

Several multiphase models exist for predicting pressure drops in vertical, inclined and horizontal wells. Most of these models made efforts to unravel the underlying physics of multiphase fluid flow for both mechanistic and analytical models with ranges of applicability. However, these developed models have their specific limitations or ranges of applicability in terms of pressures, rates, basic sediments and water (BSW), choke sizes, fluid ratios, etc thus there is no one model that is universally acclaimed best.

Data from fifteen (15) wells were obtained from a Nigeria field and multivariate linear regression was fitted into the data resulting in a good fit particularly for high production rates/wells. The method of least squares was adopted which involve setting up a set of normal equations, solving them by Gaussian elimination technique and fitting the data into the normal equations. The solution of the primary matrix was obtained through the use of MATLAB software which gave point estimates of the regression parameters leading to the development of multivariate linear regression model. The Bootstrapping method of statistical inference was also used to estimate the confidence interval of these regression parameters, while the Durbin-Watson test statistic was used to test model adequacy. The results of the model compared favourably with existing models within considered range of applicability.

This paper therefore aims to address the challenges of field based multiphase fluid flow model for operational ease using a set of over one thousand production data sets of about forty (40) years of production taken from a renowned field in the Niger Delta. More specifically, our investigations show that taking the infimum (i.e. lower bound) of the parametric bandwidths of the gas rate, average bean size and the model correction factor, b0 the model predictive capability is drastically improved for low to medium rates.
Best Practices in Seismic Data Processing- A Case Study From Ghana
Authors: Adigwe Helen-Nellie , Shoroye Adeyemi , Ajayi Jumoke , Vasconcelos Rui , Barnett Peter , Elbassiony Ahmed , Matsourak Vira , Masse Michel , Cavalin David , Hussein Waleed , Salah Magdy
Published: August 2012

Today's Exploration seismic data quality requirements for early detailed geophysical reservoir characterization, baseline time-lapse surveys and fluid characterization have been largely satisfied by the technological advances in seismic acquisition. This then followed-up by first pass conventional processing sequence, including inadequate QA/QC and project management renders obsolete the time and effort put into the planning and executing of the seismic survey in the first place, as the processing results will be no better than a conventional exploration shoot, where the main objective typically is coverage and structural definition. This paper deals with experiences from a recent 3D acquisition, first pass processing which was followed by a focussed reprocessing sequence. The latter performed by a multidisciplinary team comprising various levels of expertise from client and contractor. This paper will discuss how the more relevant advances in the application of concepts, models, techniques, workflows and decision processes related to the supervision of seismic data processing, with focus on initial detailed scope definition, contract management plan, team composition and communication protocol, detailed technical meetings and deliverables, QA/QC processes and sign-off, produced a better output in today's seismic processing project..
A Two-Dimensional Reservoir Simulator for Expansion-Drive Reservoirs
Authors: Omosebi A. O. , Igbokoyi A. O.
Published: August 2012

The application of reservoir simulation to mimic the behavior of reservoirs is widely accepted in the petroleum industry. The technique involves planning, constructing and operating a model whose behavior approximates the behavior of the actual (real) reservoir. Often, mathematical equations (i.e., a model) are developed and employed to understand the performance of the real (physical) reservoir. In this paper, a two-dimensional numerical reservoir simulator is developed for expansion-drive reservoirs. Cumulative production at bubble point is computed as a sum of expansion from each cell, based on average reservoir pressure and oil rate from the well. The average reservoir pressure is weighted based on stock tank oil that remains in the reservoir and each cell. Subsequently, plots were generated for average reservoir pressure versus time and cumulative production from each cell versus time. Also, wellbore pressure at mid-horizontal well was plotted against time on Cartesian and semi-log graphs. Furthermore, area plots were generated using color differentiation to illustrate how the reservoir pressure is depleting with time. Simulation studies performed using the developed simulator show a rapid pressure decline as would be expected for an expansion-drive reservoir due to the insignificant compressibilities that typify rocks and liquids. In addition, the reservoir volume estimated from the Cartesian and semi-log plots correctly matched the material balance estimate. Finally, the estimated recovery factor at bubble point (about 2% of the stock tank oil originally in place, STOIIP) agrees with published values in widely-circulated literatures - demonstrating the weakness of rock and liquid expansion as a primary drive mechanism.

The reservoir simulator developed in this work can be used by reservoir engineers to understand depletion in under-saturated oil reservoirs whose primary production is driven by rock and liquid expansion.
Using LWD Tools to Enhance Drilling Operations – A Case Study
Authors: Okoli Ugochukwu , Schrader Hartmut Hans , Foekema Nico
Published: August 2012

Drilling Exploratory and Appraisal wells can be challenging especially when faced with narrow mud weight / formation breakdown gradient windows and the potential for rapid pressure ramps. Operators engaged in the search for, and production of, hydrocarbon reserves in Tertiary basins are frequently confronted with complications associated with over pressured (abnormally high fluid pressure) formations. This is particularly the case in some of the Offshore Assets of Addax Petroleum. The problems associated with these formations are of direct concern to the combined activities of all phases of operations, which include geophysical, drilling, geological and petroleum engineering, thus the knowledge of the pressure distribution of a given area of operations would greatly reduce the magnitude of many of these complexities and in some cases, would completely eliminate them.

This paper presents how the use of the Baker Hughes INTEQ "TesTrak™" tool has been used to measure formation pressures while drilling (before switching off pumps to make connections). On one exploration well, it was observed the well flowed when the pumps were switched off to make a connection, thus indicating the Equivalent Circulating Density (ECD) was providing the overbalance over the formation pressure. It is also important to note that there has been a transition in optimizing the efficiency and functionality of this tool where the the Bottom Hole Assembly (BHAs) have been re-configured with the TesTrak™ being run "upside down" so that the formation pressure measuring probe would be closer to the bit and thus enable the earliest possible formation pressure information, minimizing the likelihood of a pumps off event. The process of automatic cycling of the pumps, which was required to toggle the tool back to drilling mode was minimized (only with full knowledge and agreement of all involved in drilling operations), after it was observed how dangerous it can be loosing the the over-balanced supplied by ECD. To maximize the advantage of having the logging tool read formation pressures real time, the TesTrak™ has been used to take formation pressures to verify prognosed pressure transition zones such that the mud weight can be adjusted to suit the actual pore pressure measured.

The TesTrak™ tool is presently also being used by Addax Petroleum for data gathering while drilling development wells eliminating the need to run wire-line or pipe conveyed logging in highly deviated and horizontal wells. This has saved rig time and drilling operations costs in addition to enhancing drilling efficiency. It has also improved well-site safety, helped optimize decision making and decreased the risk of differential sticking.
Use of Offset Mud Weight in Appraisal and Exploratory Well Planning - Practical Approach
Authors: Ugonoh Mohammed , Anifowose Hussein , Ajayi Olajumoke , Sijpesteijn Casper Kaars , Adedotun Wali , Obeta Chukwudi
Published: August 2012

The use of offset mud weight in combination with geologic information and drilling operations report can be very useful in estimating formation pressure in appraisal and exploratory well planning. It has been established that conventional shale pressure modeling is an effective tool for pore pressure prediction William Standifird et al 2005. The model can be updated as new data is acquired to reduce the uncertainty window and optimize drilling. This paper aims to generate shale based pore pressure profiles for the Sahara wells in northern depositional mega structure of the Niger delta using equivalent depth method and compare shale based gradient with predicted gradient from offset mud weight

The offset mud weight was expressed in pressure gradients allowing for computation of hydrostatic head of the mud and subsequently backing out the overbalance. This provided a fair estimate of the formation pressure. The estimated pressure was corrected for hydrocarbon buoyancy. The fracture gradient was derived from the leak off test of the offset well data. The lithostatic gradient is based on the regional gradient for the northern depo belt of Niger delta of Nigeria. In the shale based pore pressure estimate, the overburden gradient was modeled by superimposing the density log of the wells due to the paucity of density log. The Leak off Test of two offset wells was also utilised used to define the fracture gradient. Equivalent depth method was used in the computation of the pore pressure in the three wells

Comparison of the formation pressure profile generated using the offset mud weight from X, Y and Z wells and shale based pore pressure prediction using proprietary software indicated the two methods shows tolerable difference fit for purpose well planning.
Safety Supervision and Leadership
Authors: Samson Igwe Nkwachukwu , Nwaoha Chikezie
Published: August 2012

The supervisor is the one person who can take immediate direct action to make sure that his or her work area is safe and healthful for all employees. Russell DeReamer, author of Modern safety practices, considers the supervisor the only person who can control employees, machines and working conditions on a daily, full time basis. In his text, occupational safety and health management, Thomas Anton relates that the supervisor bears the greatest responsibility and accountability for implementing the safety and health program because it is he or she who works most directly with the employee. It is important that the supervisor understands and apply successful management and leadership principle to safety and health to make sure employee enjoy an injury and illness free work environment. Supervisors can demonstrate leadership by directly providing employees the resources, motivation, priorities and accountability, for ensuring their safety and health. Enlightened supervisors understand the value in creating and fostering a strong safety culture within their department. Integrating safety and health concerns into the everyday supervision allows for a proactive approach to accident prevention and demonstrates the importance of working safely
Application of Experimental Design Techniques to Unravel Sub-Surface Complexity in Gravity Assisted Water Injection Project in the Niger Delta
Authors: Onyeukwu C. A , Peacock A. , Osharode C. O. , Onwuchekwa C. , Adekoya O.
Published: August 2012

A pilot Gravity Assisted Water (Dumpflood) Injection scheme was executed in 1997 in X1 reservoir of a Niger Delta field ‘Alpha’. Post performance analysis showed that the injection has been successful in maintaining good pressure support and in supporting future recovery from the reservoir. However due to X1 reservoir uncertainities and variabilities in Water Dumpfllod injection rates, expected range of future recoveries could not be quantified.

This paper presents a case study of the application of Experimental Design (ED) to understand the historical performance and future predictions of a gravity-assisted water injection in ‘Alpha’ X1 reservoir. A range of static and dynamic models were constructed and experimental design methodology was used to map out the key uncertainties and to develop a range of history matched models which were used to assess the range of future hydrocarbon resource volumes likely to be produced from the reservoir under the existing development concept. In addition to the traditional sub-surface uncertainties, this project also assessed water injection rates as an additional uncertainty that significantly impacted the future recoverable from the reservoir.

Experimental design was used to create a range of history matched dynamic models of a dumpflood development that captures the key uncertainties in the reservoir. Ten history matched models were developed and carried to the prediction phase of the study. A voidage replacement development strategy was applied and all ten models were used to predict the reservoir performance over a range of water injection rates. The outcome of the analysis was used to update recoverable volume estimates and to develop a well and reservoir management strategy for the reservoir.
Evaluating the Impact of Depreciation Methods and Production Decline Patterns on Deepwater Economics: A Case Study of Nigeria
Authors: Onwuka Emmanuel I. , Iledare Omowumi O. , Echendu Joseph C.
Published: August 2012

Upstream petroleum industry remains one of the most prolific in terms of technology and risk capital transfer and rewards. Consequently, governments all over the world try to formulate fiscal regimes that could favourably attract investments to petroleum provinces in their jurisdiction. Fiscal systems that are progressive tend to find a common ground for both government and the contractor by optimizing efforts and benefits. Nigeria belongs to a region of low-risk hydrocarbon discovery relative to the world average. Therefore, the government designs fiscal regimes that would seemingly extract more economic rent from the development of its petroleum resources. This paper investigates the impact of some of the technical instruments in the Nigerian PSC on rewards from deepwater investments.

Discounted economic models are developed for two petroleum sharing contracts in Nigeria- the 2005 PSC and the interagency team (IAT) redraft of the 2008 Petroleum Industry Bill (PIB)-with due consideration to the three Arps’ production decline profiles. Different tangible CAPEX depreciation methods are imposed on the models and profitability indicators are estimated. Monte Carlo simulation analysis is applied to resolve the stochastic nature of some model input variables.

Simulation results show that maximum reward is observed when Unit of Production (UOP) depreciation method is applied in the redraft 2008 PIB; while straight line depreciation (SLD) gives better economic metrics for the 2005 PSC keeping all the terms of the contractual arrangements constant. These results could be applied in formulation of petroleum fiscal policies like the PIB by making cost depreciation a form of incentive. It is found that for a specific fiscal contract, cost depreciation method influences economic indices when used in project evaluation. Irrespective of the production decline, UOP depreciation gives earliest contractor-payout while the net present value is negatively impacted by accelerated extraction.
Multiple –Zones Flow Unit Modeling of Ilam and Sarvak Carbonate Formations of Iran through an Integrated Approach
Authors: Shahvar M. B , Kharrat R.
Published: August 2012

Ilam and Sarvak formations are two main Upper Cretaceous oil-bearing carbonate systems that are formed in an unconformity manner in Abadan plain, south-western Iran. Based on comprehensive geological and stratigraphic studies, eight reservoir zones are determined in these formations that four of them are major oil reservoirs, three of them are to some extent poor reservoirs with low amounts of porosity and permeability and the last one is a water zone. Due to the importance of flow unit modeling in appropriate reservoir characterization and simulation, this study has focused on constructing the petrophysical flow unit models for each reservoir interval of the understudy formations. Since rock typing is a challenging task in carbonate rocks and these formations suffer from heterogeneity, relying on the result of one rock typing method would not be wise, therefore it is tried to integrate the results of different flow units characterization techniques that their capability have been confirmed before. For this purpose, Winland R35 model, stratigraphic modified Lorenz plot model, flow zone index model and normalized cumulative rock quality index model are built for each zone. By accurate interpretation of the results, existed discrepancies between the models are removed and the numbers of flow units that are confirmed by all the methods are introduced for each interval that is useful for further field development plans. Difference of this study with respect to prior ones is in integrating the results of four major rock typing techniques because each method has some advantages and disadvantages and cannot be used individually for flow unit characterization especially in heterogeneous carbonate systems.
Vertical-Horizontal Permeability Relationships for Sandstone Reservoirs
Authors: Philip C. Iheanacho , Tiab Djebbar , Alpheus O. Igbokoyi
Published: August 2012

One of the important petrophysical parameter in reservoir description is the permeability distribution in a given reservoir. It is well known that most reservoir are heterogeneous in nature and homogeneous ones being the few exceptions. Therefore, most reservoirs exist with different degree of permeability anisotropy and reservoir heterogeneity.

This work investigates the relationship between vertical and horizontal permeability in sandstone reservoirs. Various petrophysical properties were estimated from core and log data obtained from a Niger-Delta sandstone reservoir. New and improved correlations between vertical permeability, horizontal permeability, effective porosity and shale fraction were developed for the zones that were analyzed.

These correlations show that there is a strong relationship between vertical permeability, horizontal permeability, effective porosity, and shale fraction for the different zones that were analyzed and that these correlations are affected by the number of flow units in each zone.
Improving the Efficiency of the Fischer-Tropsch Synthesis Using the CO2 Reduction Alternative
Authors: Habib Bello , Ogbonna Joel , Ikiensikimama Sunday Sunday
Published: August 2012

Gas-to-liquids technologyy (GTL) involves the chemical conversion of methane (usually in the form of natural gas) into easily transportable liquids like gasoline, diesel and heavy oils. GTL technology involves three basic steps: syngas production, Fischer-Tropsch (FT) synthesis and product upgrade. The FT synthesis (or Fischer-Tropsch process) is a set of chemical reactions which converts synthetic gas or "syngas" into liquid hydrocarbons.

This work show the benefits of a new GTL process (called the CO2 reduction process) over the conventional GTL process. ASPEN Hysys® Version 2004 (Build 13.1.2) Process Simulator was used to compare the product yield, power recovery and effluent water outlet of the conventional GTL and the CO2 reduction alternative.

The simulation shows that successful elimination of the O2 generator, the CO2 removal unit and the H2 conditioning unit in the CO2 reduction GTL plant decreases the total power consumption of the GTL plant by about 21%, lesser effluent water production and increases yield of the most desired FT fuel, diesel by 33.5%.
Economic Analysis of Subsea Oil and Gas Production Pipe-In-Pipe Technology for Offshore Gas Development in Nigeria
Authors: Osokogwu U , Joseph A , Ajienka J. A , Ogiri Rex. O.
Published: August 2012

Pipe-in-Pipe technology is a pipeline system consisting of two coaxial pipes. The inner pipe carries the fluid and is encased within a larger diameter outer pipe which seals the annulus between the two pipes. The annulus can be filled with a wide range of thermal insulating materials such as fiberglass, glasswool, microporous materials, aerogel, polyurethane foam, ceramics etc. This is seen as a solution to the effective management of the long problem of flow assurance in subsea fields. The pipe-in-pipe technology is thought to be extensively ideal for the transportation of well bore fluids from a subsea field, as it is capable of withstanding the difficult conditions of the ocean with its low overall heat transfer coefficient (OHTC) of less than 1 W/m2K, but this it does achieve at added cost. The aim of this paper is to economically analyze the pipe-in-pipe technology using a case study of Rosa field, an offshore field off the coast of Angola relative to offshore Gas Development in Nigeria. The following profitability indices; Net present value (NPV), internal rate of return (IRR), Profitability index and Payout or payback period were used to compare the cost of a pipe-in-pipe technology and that of a conventional pipeline system for an oil and gas field. For the pipe-in-pipe technology, a real NPV of $5.5 billion, IRR of 65.7%, PI of 3.22and payback period of 1.46 years and a money of the day NPV of $10 billion, IRR of 82.1%, PI of 5.0 and payback period of 1.19 years were achieved while for a conventional pipeline, a real NPV of $5.6 billion, IRR of 66.5%, PI of 3.28 and payback period of 1.49 years and money of the day NPV of $10.1 billion, IRR of 83%, PI of 5.1 and payback period of 1.16 years were achieved.
Transient Analysis in Partially Completed Wells
Authors: Otiede D. O , Onyekonwu M. O , Olafuyi O. A , Laka Z. L
Published: August 2012

Good understanding of the flow regimes is necessary for accurate interpretation of well test results. Partially completed or penetrating wells develop flow geometries which are different from the radial flow model on which conventional well test analysis is based and so the radial flow equation will not be adequate for analysing the transient behaviours resulting from such wells. A threefold, approach, namely, Model Preparation, Numerical Reservoir Simulation, and Well Test Analysis was used in this work to study the effects of partial penetration on the transient pressure response of partially penetrating wells. The effects of anisotropy, wellbore storage, position of partial completion and penetration were all considered. Spherical flow approximation was used for the description of wells with partial completion and partial penetration.

In the analysis, three flow regimes were found to appear on the transient pressure response. Pressure drop was greatest in wells with very low penetration ratio. The position of partial completion had no effect on pressure transient response.

Vertical permeability is very important in predicting gas or water coning or performance of horizontal wells. This is very useful in for completion engineering optimisation and as well provides a good rationale for drilling horizontal wells. Also Knowledge of the vertical anisotropy will aid reservoir development and the planning of future secondary recovery.
Economic Comparison of Liquefied Natural Gas Floating Production Storage and Offloading Plant (LNG FPSO) with the Proposed Brass LNG
Authors: Lazson Nchekwube Edwin , Ikiensikimama Sunday Sunday
Published: August 2012

With the ongoing gas revolution in Nigeria, it will be appropriate that our government invest wisely by going for the best economical venture. The objective of this study is to provide a perspective on portfolio diversification, investment and resource development. The economic analysis was carried out deterministically using economic indices like Net Present Value, Internal Rate of Return, Present Value Rate and others. Probabilistic model was also incorporated to assess the impact of the uncertainties in the input parameters using Monte Carlo Simulation through the use of Crystal ball software. The key uncertainties parameters were the same for both projects though their level of impacts differs. The deterministic model results obtained was Net Present Value of $2.3 billion at a discount value of 15% and Internal Rate of Return at 32.68% for LNG FPSO while Brass LNG has NPV of $607,640,260.85, at a discount value of 15% and internal Rate of Return at 16.28%. These clearly showed that LNG FPSO is profitable for offshore environment within the range of 25 nautical miles with water depth of 20 meters and above.
Vision 20:2020 Initiative and the Nigerian Oil and Gas Industry: An Empirical Analysis of the Environmental Dimension
Authors: Leo Morgan
Published: August 2012

Presently, crude oil generates about 90% of Nigeria's foreign exchange and 82 percent of the Government revenue. Together with natural gas, the industry contributes about 79 percent of commercially traded energy in the country. Meanwhile, Nigeria Vision 20:2020 Economic Transformation Blueprint being implemented by the present administration is envisioned to place the country among the Top 20 economies in the world, with minimum Gross Domestic Product (GDP) of USD900 billion and a per capita income of no less than USD4000 per annum by the year 2020. Judging from the critical role the oil and gas industry plays in the Nigerian economy, and the confidence derived from the projection from the International Energy Agency (IEA) that through 2030, fossil fuels will continue to satisfy the vast majority of the global energy demand, it is readily inferred that the bulk of the financial resources required to bankroll the development agenda will be mobilized from the oil and gas sub sector. Evidently, the successful implementation of the programme depends largely on the stability of the oil and gas industry, especially in the context of the natural environment. This paper gives an overview of the environmental dynamics necessary for sustainable exploitation of fossil energy sources in Nigeria. Leveraging tested case studies and best practices, it also diagnosis the linkages between environmental sustainability and national development programmes.
A New Model for Determining the Radius of Mud Loss During Drilling Operation in a Radial Fractured Network
Authors: Shahri M. Pordel , Zabihi S. H.
Published: August 2012

A new solution for determining the amount of mud loss during drilling operation in a fractured reservoir having a regular two- or three-dimensional radial fractured network with the novel inclusion of a convective transport of filtrate in the matrix is presented. Convective-dispersive filtrate transport along the network is modeled in which drilling mud can be filtered in existing matrix. The filter cake effect at the fracture-matrix interface in the network is simulated by means of an empirically decaying filter rate equation. The numerical solution is used in this study. The consistency of numerical solution is checked and the best situation is considered. The sensitivity analysis on all parameters in the model has been done and the effect of each parameters such as wellbore loss rate, reservoir thickness, fracture opening size, matrix porosity, matrix permeability and dispersivity, on the amount of filtration are inversitaged. By means of developed model, the amount of mud filtration can be plotted against position in different fractured network configurations for different wellbore conditions, reservoir properties and reservoir geometries at different times. The position in the fracture network at which the curve of concentration reaches zero can be considered to represent skin radius caused by drilling operation. This radius can be used for determining the acid volume which is needed for acidizing operation and accurate well-log interpretation.
Role of Innovation and Policy Development for a Sustainable Environment
Authors: Oyekunle A. A
Published: August 2012

The global demand for energy has been on the rise. Most of this demand has been satisfied through hydrocarbons. The exploration, exploitation and growing consumption of hydrocarbon have had great impact on the environment. At the rate energy demand is rising and the disappearance of cheap hydrocarbon, other sources of energy would have to come into the energy mix to meet this growing demand.

Despite ready availability of energy being desirable and a key to economic progress, energy development has to be done in a way that ensures our environment can continue to exist and support life. As energy development is putting stress on the environment and the need to sustain the environment is putting constraints on conventional energy development, policy development and technological innovation especially towards the development of renewable energy have come to play a big role.

This paper uses quantitative and qualitative approaches to show the roles of technological innovation and policy development in achieving a balance between the sustainability of the environment and meeting energy demands.
Effects of Partial Completion on Productivity Index
Authors: Dankwa O. K , Igbokoyi A. O
Published: August 2012

A new method for analyzing productivity index (PI) on vertical wells is presented. Well performance is often measured in terms of the well's productivity which is dependent on a number of factors such as the reservoir's configuration, the type of completion, petrophysical and fluid properties, formation damage, etc. The effect of partial completion is the main focus of this study since almost all vertical wells are partially completed due to the reasons of water coning or gas cap issue, etc.

Productivity of a well is usually evaluated on the long time performance behavior, thus the pseudo-steady state (late time) approach has been employed for the calculation of the productivity index. Closed system (no-flow boundary) and constant pressure boundary (mixed boundaries) cases are investigated.

Several key factors have been tested on productivity index such as pseudo skin, shape factors, penetration ratio, reservoir drainage area and etc. The effects of these factors have been analyzed on productivity index.

Shape factors of various well positions in bounded reservoirs were computed and compared with the results obtained by Dietz.
Natural Gas as an Alternative Fossil Fuel; The Prospect and The Market In 2020
Authors: Osokogwu U , Ajienka J. A
Published: August 2012

Natural gas within the mix of energy sources is likely to take the lead in the world's energy needs. The decisive trend in its utilization relative to other fossil fuels is as a result of; the growing energy demand from an expanding world economy, environmental pressure for the use of a fossil fuel free from environmental degradations, market development and improved technologies for its production, processing, transportation, storage and more importantly its abundance in nature. Presently, the world has a proven reserve of about 156 trillion cubic meters (5500 Trillion cubic feet) of natural gas. Out of this, approximately 31% is discovered in Russia, 36% in the Middle East and 8% in the Asia-Pacific region with overall consumption of about 2.5trillion cubic meters per year. The overall demand will continue to increase especially in Asia-Pacific region where most countries are pressing ahead with energy– intensive industrialization projects. Natural gas prospect is high with the market improving appreciatively since the advent of LNG and CNG technologies where over 4,660 refuelling stations with approximately 2.7million vehicles are running on CNG globally. More so, we envisage more growth in natural gas market in 2020 with the recent projects on GTL from countries like Qatar which is currently constructing her GTL plants up to 15 trains.
Modeling of Fracture Ballooning in Naturally Fractured Reservoirs: A Sensitivity Analysis
Authors: Mehrabi Mehran , Zeyghami Mohammad , Shahri Mojtaba Pordel
Published: August 2012

Fracture ballooning usually occurs in naturally fractured reservoirs and is often mistakenly regarded as an influx offormation fluid, which may result in misdiagnosed costly operations. Several models have been developed to treat this phenomenon and distinguish it from conventional losses or kicks. Among these borehole ballooning models and mechanisms, opening/closing of natural fractures is considered to have the main role in naturally fractured reservoirs.

In this study a mathematical model is developed for mud invasion through a disk-shaped and deformable fracture with two impermeable walls and a limited extension. A governing equation is derived based on the lubrication approximation theory (Reynolds's Equation) for radial flow in a single fracture. Considering an exponential deformation law to describe the pressure-aperture relationship, and a yield-power-law model to describe mud rheology, makes this model more general and much closer to the reality than the previous ones. Describing the fluid rheology with yield-power-law model turns the governing equation into a versatile model as it includes various types of drilling mud rheology.

The governing equation is solved numerically using finite difference method. Results show how different parameters can affect fracture ballooning and volume and rate of mud loss/gain. The effects of several parameters related to the mechanical properties of the fracture are analyzed. Shortcomings of the proposed model are outlined.
Estimating the Effect of Specific Gravity of Weighting Material on the Solids Concentration of Weighted Mud
Authors: Bahadori Alireza
Published: August 2012

An important function of drilling mud is the control of formation fluid pressure to prevent blowouts. The density of the mud must be raised at times to stabilize incompetent formations. Any substance that is denser than water and that does not adversely affect other properties of the mud can be added to raise the density to some extent. Obviously, the specific gravity of the weighting agent is of primary importance, especially in very heavy muds. The fractional volume occupied by the added solid is a major limiting factor in its use. In this work a simple-to-use correlation has been developed to predict the effect of the specific gravity of the weighting material and the density of mud on the solids concentration of weighted muds. Estimations are found to be in excellent agreement with the reliable data in the literature with average absolute deviation being less than 0.3%.
Hydrodynamics of Sand-oil-Gas Multiphase Flow in a Near Vertical Well
Authors: Adeyanju O. A. , Oyekunle L. O.
Published: August 2012

A calculation method for predicting Bottom Hole Pressure (BHP) based on easily obtainable wellhead parameter has been the preferred method in the petroleum industry. But, the predictive capability of the existing correlations is a thing of concern to the oil industry operators. This is due to the inability of the existing models and correlations to account for the presence of the sand particles in the flow stream; also the requirement for the well to be shut-in for BHP predictions is counter productive. These inadequacies were corrected in the proposed model. Results showed that the average pressure drop in the multiphase fluid flow using the proposed model is higher than the pressure drops determined using existing models and correlations. The effects of the fluid density, viscosity and velocity on the sand particles lifting were also investigated and results showed that the sand particle lifting was improved by higher fluid velocity and density and lower fluid viscosity. Validation of the proposed model with field data showed that the model predicts the field BHP data better than any of the existing models and correlations, based on the Average Absolute Deviation (AAD) value of 6.53 returned by the proposed model compared to AAD value of between 13.56 and 24.67 returned by the existing models and correlations.
Managing Paraffin Wax Deposition in Oil Wells – Related Problems in Nigerian Oil Fields
Authors: Oseghale C. Ijogbemeye , Akpabio E. J
Published: August 2012

The estimation and prediction of wax formation and the understanding of the physicochemical characteristics of the wax phase are of major importance in flow assurance. The characterization of the oil and wax can provide useful estimates of the parameters and behavior required for operational engineering process developments and/or physical modifications to the processing of crude oils, aiming at the reduction of costs of production and transportation. The strategy employed in this study was to use temperature and fluid characterization analysis of Nigerian crude to predict the potential for paraffin wax related problems in Nigerian oilfields. This approach defined the oilfields with probably high risk of wax deposition potential amongst Nigerian crude. The synopsis of this paper proved that some Nigerian oilfield presents a potentially serious problem.
Temperature Prediction Model for Flowing Distribution in Wellbores and Pipelines
Authors: Charles Y. O , Igbokoyi A. O
Published: August 2012

Down-hole temperature data are important information needed to understand flowing conditions. Since wellbore temperature profile is affected by inflow profiles, it is then possible to predict inflow of fluid into the wellbore.

While gas production usually causes a temperature decrease due to Joule Thomson effect water entry result in warming of the wellbore. Warmer water entry is as a result of inflow from a warmer aquifer zone due to water coning. Water entry by water coning can therefore easily be detected from temperature profile since it increases the wellbore temperature.

In this study, we successfully developed a temperature prediction model which calculates temperature profiles for fluid flowing in the wellbore and considers Joule Thomson coefficient as a function of mass flow rate of the fluid phases (oil, water, and gas). We modified the Alves et al temperature equation into three phase temperature equation and it was used to predict water and gas inflow into the wellbore. Correlations that can be applied to oil field ranges of temperature and pressure were used to determine fluid properties. The model was used to investigate the effect of gas and water entry that created change in temperature profile along the wellbore. The temperature equation can be applied to pipelines or production and injection wells under single phase, two phase, and three phase flow for horizontal, vertical, and inclined wells

Cases were considered to analyze the effect of water and gas entry into the wellbore. Fluid inflow was predicted from the temperature profile, the result shows that water entry increases wellbore temperature and gas entry decreases wellbore temperature.
Metal removal via particulate material in a lowland river system
Authors: Webster-Brown J. G. , Dee T. J. , Hegan A. F.
Published: August 2012

Twelve month surveys of acid-soluble and dissolved trace metal concentrations in the lower Waikato River (in 1998/9 and 2005/6) showed abnormally low particulate Fe, Mn, Cu, Pb and Zn concentrations and mass flux in autumn, when the suspended particulate material (SPM) had a relatively high diatom and organic carbon content, and low Fe and Al content. Dissolved Mn, Cu and Zn concentrations also decreased in autumn, while dissolved Fe and Pb concentrations were unaffected. While SPM settlement under the low river flow conditions present in autumn can explain the removal of particulate metals, it does not explain dissolved metal removal. SPM-metal interaction was therefore investigated using seasonal monitoring data, experimental adsorption studies, sequential extraction and geochemical modelling. Pb binding to SPM occurred predominantly via Fe-oxide surfaces, and could be reliably predicted using surface complexation adsorption modelling. Dissolved Mn concentrations were controlled by the solubility of Mn oxide, but enhanced removal during autumn could be attributed to uptake by diatoms. Zn and Cu were also adsorbed on Fe-oxide in the SPM, but removal from the water column in autumn appeared augmented by Zn adsorption onto Mn-oxide, and Cu adsorption onto the organic extracellular surfaces of the diatoms.
Characteristics of WWTP sludge after drying in greenhouse for agricultural purposes
Authors: Lima Márcia Regina Pereira , Zandonade Eliana , Sobrinho Pedro Alem
Published: August 2012

The sludge generated by sewage treatment which meets regulatory standards can be used in agriculture. With this understanding, the focus of this study is the evaluation of the agricultural characteristics and inorganic substances in excess activated sludge, which was subjected to drying in a greenhouse. The variables (factor) evaluated during the drying process were: type of sludge (digested or not digested), addition of lime to the sludge, and the physical layout and rotation of sludge in the greenhouse. The parameters monitored for this assessment were moisture, volatile solids and pH. The greenhouse cover and sides were made of translucent plastic to allow the penetration of solar radiation and prevent water from entering. A impermeable floor was used. The sludge was generated in sewage treatment plants located in the metropolitan region of Grande Vitória, Espírito Santo, Brazil. The solar drying of wastewater sludge in a greenhouse presented satisfactory results.
Effects of heat treatment on microbial communities of granular sludge for biological hydrogen production
Authors: Alibardi Luca , Favaro Lorenzo , Lavagnolo Maria Cristina , Basaglia Marina , Casella Sergio
Published: August 2012

Dark fermentation shares many features with anaerobic digestion with the exception that to maximize hydrogen production, methanogens and hydrogen-consuming bacteria should be inhibited. Heat treatment is widely applied as an inoculum pre-treatment due to its effectiveness in inhibiting methanogenic microflora but it may not exclusively select for hydrogen-producing bacteria. This work evaluated the effects of heat treatment on microbial viability and structure of anaerobic granular sludge. Heat treatment was carried out on granular sludge at 100 °C with four residence times (0.5, 1, 2 and 4 h). Hydrogen production of treated sludges was studied from glucose by means of batch test at different pH values. Results indicated that each heat treatment strongly influenced the granular sludge resulting in microbial communities having different hydrogen productions. The highest hydrogen yields (2.14 moles of hydrogen per mole of glucose) were obtained at pH 5.5 using the sludge treated for 4 h characterized by the lowest CFU concentration (2.3 × 103CFU/g sludge). This study demonstrated that heat treatment should be carefully defined according to the structure of the sludge microbial community, allowing the selection of highly efficient hydrogen-producing microbes.
Stabilization of source-separated urine by biological nitrification process: treatment performance and nitrite accumulation
Authors: Sun F. Y. , Dong W. Y. , Shao M. F. , Li J. , Peng L. Y.
Published: August 2012

A laboratory study on nitrification of high-strength source-separated urine was conducted by means of sequencing batch reactors (SBR) and membrane bioreactors (MBR). The highest influent ammonia concentration for SBR and MBR reached more than 2,400 and 1,000 mg N/L, while the maximum pH was about 9 and 8.9, respectively. The ammonia oxidizing efficiency in both SBRs and MBRs was around 50%, which was restrained mainly by the deficiency of alkalinity in bulks. Meanwhile, the nitrite accumulation did also dominate in these two systems, and the major factor to inhibit the nitrite oxidization was thought to be the high free ammonia and free nitrous acid content in bulks. Hence, an ammonia nitrite solution was achieved with concentration ratio of 1:1; after that ammonia oxidation was restrained owing to the deficiency of alkalinity in urine. The temperature and influent ammonia content have no great influence on the nitrification process in both kinds of bioreactors. The nitrification can be progressed under a solids retention time (SRT) longer than 30 d; however, termination of ammonia oxidization was observed as the SRT fell below 20 d. The nitrifier biomass showed an excellent settleability, such that the suspended solids (SS) in effluent was of a low average, about 60 mg/L. This study on the stabilization of human urine will be useful to understand the process of urine separation from source.