bluuebunny/crossref_metadata_2025 huggingface dataset:
Seismic Activity in the Central Adriatic Offshore of Italy: A Review of the 1987 ML 5 Porto San Giorgio Earthquake
Authors: Battimelli Elvira , Adinolfi Guido Maria , Amoroso Ortensia , Capuano Paolo
Published: July 2019

On 3 July 1987, a seismic sequence, with a mainshock of ML 5, took place in the offshore Adriatic, close to the coast of Porto San Giorgio (PSG), Italy. We present an accurate relocation of the PSG seismic sequence using a nonlinear probabilistic approach (Lomax et al., 2000). The trade‐off between the hypocentral location and the velocity model was exhaustively explored using six different velocity models available for the area provided by previous studies. Through numerous tests performed by relocating the mainshock, we selected the two best velocity models providing two different depths (2.0 and 18.0 km). To resolve this intrinsic ambiguity, we developed a technique that uses the macroseismic intensity field data based on a grid search of the magnitude–depth space. The results show that the mainshock has a depth of 5.7 km and a magnitude (ML) equal to 5; moreover, the relocated seismic sequence (∼30 events) developed in the upper portion of the crust (at a depth less than 15 km), thus activating thrust faults, which is typical of the main geological features that characterize the outer Apennines thrust belt and the Adriatic foreland folds. Because the Adriatic Sea hosts several hydrocarbon (mainly gas) production fields located near active faults, with some of them in the area of this study, analyzing the instrumental seismicity is necessary to better understand the seismicity generated by these seismogenic faults and improve the assessment of the area’s seismic hazards.
Entre o esquecemento e a memoria. Educación, mitos e realidades
Authors: Cid Galante Rosa María
Published: July 2019

Recensión do libro: AA.VV. (2108), Entre el olvido y la memoria. Educación, mitos y realidades.
Az élelmiszerpazarlás és a fogyasztói tudatosság kapcsolata
Authors: Szűcs Róbert Sándor
Published: July 2019

Összefoglalásként megállapítható, hogy napjainkban egyre inkább kiemelt figyelem övezi az élelmiszerek hatékony felhasználására való törekvést. Ez a törekvés mára nem csupán makro szinten valósul meg, hanem egyre inkább megjelenik a háztartások gondolatkörében is. A pazarlás nem csupán a tőlünk kedvezőbb gazdasági mutatószámokkal rendelkező országok problémája, hanem bizony „mi” is vagyunk azok az „ők”, akik pazarolják az élelmiszert. Egy olyan országban, mint hazánk, ahol az EU átlagához viszonyított jövedelemszint alacsony, kiemelt figyelmet kell, hogy jelentsen az élelmiszerek hatékony felhasználása. Ennek megvalósulásáért, ellentétben nagyon sok minden mással, maga a háztartás, az egyén tehet a legtöbbet. A kutatás rámutatott arra, hogy az élelmiszer pazarlás összefügg a fogyasztó bevallott jövedelmi szintjével. Az átlagostól alacsonyabb bevallott jövedelemszinttel rendelkezők esetében azt tapasztalhattuk, hogy a pazarlás becsült mértéke a több termék esetében is csökkent az átlagoshoz képest. Az átlagostól magasabb bevallott jövedelemszinttel rendelkezők esetén a becsült pazarlás mértéke emelkedik több termékkategóriában is.  A jövedelemszint emelkedésével a tudatos felhasználás csökkent, a pazarlás mértéke emelkedő tendenciát mutatott. A kérdés természetesen nem ennyire egyszerű, hiszen a gazdasági keretfeltételek, a játékszabályok megvalósítása komoly nemzetgazdasági vagy ezen is túlmutató, szupranacionális kérdés lehet. A tudatosság szintjére eredményeim alapján a család jövedelme komoly hatást fejt ki, a jövedelmi szint emelkedésével a tudatossági fegyelem csökken. Ez az eredmény összefügg a szakirodalom makrogazdasági adataival.
JEL-kódok: I30, M31, Q18
TERMINATION OF WAHDATUL WUJUD IN ISLAMIC CIVILIZATION IN ACEH: CRITICAL ANALYSIS OF ITHAF AD-DHAKI, THE WORKS OF IBRAHIM KURANI
Authors: Nasution Ismail Fahmi Arrauf
Published: July 2019

Wahdatul Wujud or Unity of Being is a sufi doctrine that is in accordance with the well-known, inclusive and permissive views of the people of Nusantara. The teaching has proven to be an important part in realizing the peaceful and harmonious civilization of the Islamic archipelago. Unfortunately when orthodox theology doctrines which nuanced exclusive and radical dominated the Muslim intellectual discourse of archipelago, the doctrine of Wahdatul Wujud become excluded and even terminated from the stage of Islamic intellectualism of archipelago. This paper wants to evaluate critically the work of Ibrahim Kurani, Ithaf ad-Dhaki bi Shahr at-Tuhfah al-Mursalah ila an-Nabi which was written intentionally to explain the papers of Muhammad Fadhullah al-Burhanpuri entitled at-Tuhfah al-Mursalah ila an-Nabi Which discusses the teachings of Wahdatul Wujud that had been spread in the archipelago. This Ibrahim Kurani’s works is necessasry to be evaluated though it is generally accepted as the synthesis of Wahdatul Wujud according to orthodox theology, but  factually it has a very significant role in reducing this doctrine so that Wahdatul Wujud becomes a foreign doctrine in the archipelago. In this study the authors found some epistemological and academic error committed by Ibrahim Kurani to the doctrine of Wahdatul Wujud in his book. The author expects Wahdatul Wujud could be revived in scientific and academic discourse as a solution to counter the teachings of exclusive and radical Islam in order to realize a peaceful and democratic Islam as had happened in the history of Islamic civilization in archipelago.
The Waqf as The Social Institution and The Realization of Islam Nusantara: The Study in West Sumatera
Authors: Medaline Onny
Published: July 2019

As a religion which concerned with the social, cultural, psychological and spiritual of the community, Islamic laws had the ability to answer the new problems, especially in all muamalah fields. The Islamic of Nusantara was the comprehension, experience, and implementation of Islam in mualamat of fiqih segment as the dialectical result among the syariat, cultural and  reality throughout the archipelago. The reality reflected on in waqf that became a dynamical ijtihadiyyat  laws along with the benefit which fulfilled the certain space, time and situation. The waqf as the social institution was the realization of the Islamic laws transformation to become a law formation which consisted of the funding system of tasawuf (ilahiyah) study and Islam absolute which grew as the social framework that had the ability to answer all the community needs in some of life fields which affected by the dynamic of space and time. In the context of social institution, the waqf was the  norm system which arranged all the human actions in order to fulfill the basic needs in community life, and it was  a part of  community norms which formed the social, religion institutions and the other institutions which protected by the state.
Evaluating the Effects of High Viscosity Liquid on Two Phase Flow Slug Translational Velocity using Gamma Radiation Methods
Authors: Baba Yahaya D. , Aliyu Aliyu M. , Okeke Nonso E. , Girei Adamu S. , Yeung Hoi
Published: July 2019

Slug translational velocity, described as the velocity of slug units, is the summation of the maximum mixture velocity in the slug body and the drift velocity. Accurate estimation of this parameter is important for energy-efficient design of oil and gas pipelines. A survey of the literature revealed that existing prediction models of this parameter were developed based on observation from low viscosity liquids (of 1 Pa.s or less). However, its behaviour in pipes transporting higher viscosity oils is significantly different. In this research work, new data for slug translational velocity in high-viscosity oil-gas flows are reported. Scaled experiments were carried out using a mixture of air and Mineral oil of viscosity ranging from 0.7 to 6.0 Pa.s in a 17-m long horizontal pipe of 0.0762 m ID. Temperature dependence of the oil's viscosity is given as μ=−0.0043T3+0.0389T2−1.4174T+18.141. The slug translational velocity was measured by means two pairs of two fast-sampling Gamma Densitometers with a sampling frequency of 250 Hz. For the range of experimental flow conditions investigated, increase in liquid oil viscosity was observed to strongly influence slug translational velocity. A new predictive correlation incorporating the effect of viscosity on slug translational velocity was derived using the current dataset and incorporating those obtained in literature with oil viscosity ranging from 0.189–6.0 Pa.s for horizontal flow. A comparison by statistical analysis and validation and of the new closure relationship showed a remarkably improved performance over existing correlations.
Horizontal Well Standoff Performance and Exploitation of Thin Oil Rim
Authors: Obidike Peter , Onyekonwu Mike , Ubani C. E.
Published: July 2019

In this paper one of the areas of conflicts observed with the performance of horizontal wells standoff with respect to development of thin oil rim reservoirs is examined.

In a technical paper as part of the critical review of literature on the exploitation of thin oil rim reservoirs with large gas cap and aquifer, this author had highlighted the problem. As part of sensitives in horizontal well standoff, Cosmos and Fatoke (2004) tested three positions; one-third, centre and two-third positions from the GOC in a Niger Delta field. They concluded that the landing closest to the GOC (one-third position) yielded lowest Oil compared to the centre and two-third positions. Surprisingly the work done by Sai Garimella et al (2011) in a 60ft Ghariff & Al Khlata shallow marine low permeability sandstone reservoirs in a field in Oman showed a different result with the one-third position indicating an optimum recovery from a horizontal well. Interestingly both authors positions on the performance had support from other authors.

This study used a 3D reservoir model, investigated different horizontal well standoff performances and applied permeability reduction to simulate different reservoir quality. The objective was to see if the reservoir quality was a factor in the different horizontal well standoff performance seen from different regions of the world while noting their different depositional environments. Results from the investigation is presented in this paper and shows a different trend from both authors mentioned above.
Decline Line Analysis DLA: A Method for Forecasting Cumulative Production for Solution-Gas Drive Reservoirs Based on Fetkovich Type Curve Approach
Authors: Sumaila Omaga
Published: July 2019

A conventional method for DCA for a solution-gas drive reservoir is the Arp's Approach. Another approach, an improved approach, is the Fetkovich Type Curve Approach which involves the combination of rate equation and material balance equation for finite systems to obtain rate-time equations for solution-gas drive reservoir using backpressure exponent(n) in place of Arp's decline exponent(b). This improved approach, however, has a number of limitations. First, it is difficult to judge which type curve production data match. It has a lower resolution. Also, the developed cumulative-rate model for the material balance equation form: PR2is linear with Np, tends to give inaccurate result.

This paper, first, presents a cumulative-rate model using a mathematical approach. Then, the Fetkovich rate-time relationships for both the material balance equation forms: PR2is linear with Np, PR is linear with Np, are transferred into linear relationships(in a log-log plot) by finding the derivative of the natural logarithm of the dimensionless rate(qDd) with respect to the dimensionless time(tDd). Consequently, the type lines are generated and upon about fifty (50) trials, conditions required for optimum workability are presented.

The developed cumulative-rate model was validated with field data from a reservoir in the Niger Delta. The correlation between forecasted cumulative production and actual production data is 0.99988. Thus, indicating high positive correlation. Also, the linearized models were validated with production data from Arbuckle Lime, Kansas. The correlation too, is as high as 0.99988. Thereafter, a user-friendly Microsoft Excel spreadsheet application for computing cumulative production given rate is created using Excel VBA.
Comparative Analysis of Commercial Natural Gas Pipeline Economics under the Extant and Calculated Tariff Systems
Authors: Adejumo Adedapo , Iledare Omowumi , Echendu Joseph
Published: July 2019

This paper presents a comparative analysis of economics of a commercial gas pipeline using the extant fixed tariff and a calculated tariff based on the Rate of Return Regulation framework. While the extant tariff is fixed at 0.8$/Mscf irrespective of throughput and location, the calculated tariff adjusts tariff levels to cost profiles and aligns it with the operators cost of capital. The arbitrarily fixed gas pipeline tariff has resulted in poor response by international investors to an otherwise lucrative sector of the gas industry while increasing the burden of a pipeline development on government in the face of limited resources. Using the proposed 48" x 127-Kilometer Obiafu-Obrikom-Oben Pipeline (OB3) as a case study, the discounted cashflow and stochastic analysis methodology are adopted to estimate economic indicators. Results show that the payback period is very attractive at less than 6.5 years for the calculated tariff while the payback period is in excess of 7.7 years for the extant tariff. NPV of the calculated tariff indicate a less likely than not chance of project failure while analysis with the extant tariff indicates a 23 percent likelihood of project failure. The paper provides additive information needed for would-be investors and the Nigerian government towards ensuring a workable framework to engender the envisaged infrastructure for gas pipeline.
Formulation of Water Based Drilling Fluid Using Local Mud Uwheru & Otor-Udu Clay
Authors: Odion Aihie John
Published: July 2019

Drilling fluid is one of the major substances used when drilling a well, as it serves numerous purposes such as lubrication and cooling of the drilling bit, cuttings removal to mention a few. And one of its major constituent is the bentonite, clay that serves as the dispersed phase. The cost of procuring the bentonite clay for the production of drilling fluid is expensive because of its importation into the country hereby increasing the overall cost of drilling a well.

This paper investigated the suitability of suspected clay from Uwheru and Otor-Udu village in Delta State, Nigeria for the production of water based drilling fluid. The mud was formulated using 21.0g of each clay local sample and 350ml of fresh water. Different concentrations of pH and viscosity chemical additives were used. Comparative analysis was made on the drilling mud sample formulated from clay obtained from the study areas namely (Uwheru and Otor-Udu) to determine their suitability for the formulation of drilling fluids and to determine if it meets the API standard. The properties tested for include the mud density, pH, sand content and rheological properties.

After laboratory work was conducted, the two formulated mud samples had same mud weight of 8.5ppg which was slightly below the API standard for bentonite clay of 8.65minimum and 9.60maximum. A pH control additive (NaOH) and Viscosifier additive (CMC) were added.

In conclusion, analysis was made on the experimental values of Uwheru which had values of 3cp for 2cp for the 600rpm and 300rpm rheological readings respectively, pH of 5, sand content of 0.1ml and density of 8.5ppg while that of Otor-Udu had values of 3cp and 2cp for the 600rpm and 300rpm rheological readings respectively, pH of 5, sand content of 0.05ml and density of 8.5ppg. From the analysis made between the local clay formulated drilling fluid samples and the standard API values for bentonite using graphs and charts, the local clay can be improvised for bentonite.
Effect of Environmental and Occupational Exposures to Heavy Metals: The Health Implications
Authors: Anyanwu Brilliance O. , Ezejiofor Anthonet N. , Nwaogazie Ify L. , Orisakwe Orish E.
Published: July 2019

The craze for technological development has given rise to environmental safety concerns. Various human activities such as artisanal mining, illegal refining, use of leaded petrol, illegal disposal and burning of toxic waste, absorption of production industries in inhabited areas have led to high contamination and pollution associated with heavy metals. The research was done to explore the effect of low dose exposure to heavy metal mixture using male albino rats as experimental animals. The experimental rats were separated into two equal groups; (i) control receiving only deionized water, (ii) combination of metals (PbCl2+ CdCl2 + HgCl2). Treatment was carried out through oral gavage. Induced low dose heavy metal mixture substantially decreased the follicle stimulating hormone, luteinizing hormone and testosterone levels and significantly increased the prolactin level. It also resulted to hepatotoxicity by significantly increasing the liver enzymes and bilirubin level, thereby reducing the total protein and albumin levels. The lipid profile was also investigated to check the risk associated with the cardiovascular system. The result showed a considerable increase (P<0.05) in triglycerides, total cholesterol, low density lipoprotein and very low density lipoprotein and a significant reduction in high density lipoprotein when compared with the control group. Furthermore, low dose heavy metal mixture induced histopathological changes to the liver. Collectively, our findings clearly highlight that environmental and occupational exposure to heavy metals resulted to hepatotoxicity, risk to the cardiovascular system and changes to the hormonal system.
Dynamic Modelling for Reservoir Connectivity Analysis in Mature Fields
Authors: Ajayi Olawale , Ikienskimama Sunday , Mogbolu Emmanuel
Published: July 2019

Reservoir connectivity remains a critical and growing area of research and application in the petroleum industry, as most discoveries go through development to maturity. This becomes highly imperative for reservoir management decisions in highly fractured compartments or stacked reservoirs with faults across them. In most field cases and especially for a highly faulted region like the Niger Delta, there are some uncertainties around connectivity primarily due to seismic data and resolutions as regards the technology available at acquisition. The primary aim of this work is to use dynamic modelling to ascertain connectivity in mature reservoirs. This work applied the standard workflow for Reservoir Connectivity Analysis (RCA) in evaluating four (4) stacked reservoirs in the RAINBOW field, onshore Niger-Delta using dynamic modelling of the MBAL multi-tank option. Various scenarios were analyzed with the integrated data – geology, production and reservoir pressure history, fluid and rock properties to select the most likely scenario. For this analysis, a new diagnostic plot was introduced for evaluating transmissibility, which improved the clarity in decision making. Using the prevalent economic parameters, a quick evaluation was done to understand the impacts of the reservoir management decisions on the viability of this approach. From the results, two of the four reservoirs are observed to be dynamically connected. The analysis shows that a new perforation extension opportunity is a quick return decision that can yield considerable returns, while new infill opportunities as the optimal decision. Also, the effects of transmissibility on the reservoirs affect the Net Present Values of the decisions. Therefore, this improved workflow approach can be recommended as a quick win when sufficient time and resources are not available for opportunity maturation. Further work is also required to integrate this understanding to build a simulation model for robust benchmarking.
Phase Behaviour of Local Alkaline and Surfactants During Flooding
Authors: Obuebite A. A. , Onyekonwu M. O. , Akaranta O. , Ubani C. E.
Published: July 2019

The addition of natural and synthetic surfactants during chemical flooding recovers oil originally trapped by capillary forces through the reduction of the interfacial (adhesive) tension between the aqueous and oleic phases. As the interfacial tension reduces, the trapped oil droplets are mobilized forming a continuous oil bank thereby reducing the amount of residual oil saturation. The objective of phase behaviour is to determine the optimum salinity and to select the best compatible chemical composition for a specific application that can effectively enhance oil recovery. This study seeks to assess chemical compatibilities between alkaline –surfactant systems in the presence of calcium and magnesium ions; analyse synergy between alkali-surfactant slugs and crude oil to enable us to design an optimal low-cost, environmental friendly alkaline and surfactant floods for enhanced oil recovery. This is based on an understanding of fluid-fluid interactions. We conducted phase behaviour tests on selected local surfactants (AlkaSurf X, Moringa), bio-ethanol, local alkali (potash) and simulated formation brine. Aqueous stability and salinity scan experiments were conducted to determine the compatibility of the Alkaline–Surfactant systems with brine. Solutions free of precipitation were used for the interfacial-tension and phase behaviour analysis. Salinity scan results were used to calculate the solubilisation ratio and optimal salinity. Results indicate that the local Alkaline-Surfactant systems are highly tolerant of divalent ions. Also, results from pipette test showed that AlkaSurf X and Moringa alone attained a Type II (-) microemulsion, however, the addition of potash and co-surfactant at a controlled pH and concentration exhibited optimal salinity and a Type III microemulsion. This study shows that certain local alkali and surfactant can enhance oil recovery, even under harsh conditions, thus eliminating the use of harmful chemicals and need for brine softening processes which adds to the overall cost.
Isolation and Screening of Hydrocarbon Utilizing Bacteria for Biosurfactant Production: Application for Enhanced Oil Recovery
Authors: Sylvester Okotie , Onyekonwu Mike , Okpokwasili Gideon
Published: July 2019

Tertiary oil recovery techniques comprise miscible flooding, chemical, thermal and microbial injection into oil reservoirs to enhanced recovery. Several studies have been performed on the use of surfactants and polymers injection for enhanced oil recovery. But this study is focused on isolation and characterization of hydrocarbon utilizing bacteria for biosurfactants and biopolymers production. The concept of microbial enhanced oil recovery consists the injection of nutrients to activate indigenous microbes in the reservoir or injection of external hydrocarbon degrading microbes plus nutrients during field applications to ensure the organisms produce the required metabolites. These microbes have the ability to produce gases to increase reservoir pressure and displacement of immobile oil, bio-surfactants to reduce interfacial tension, biopolymer for mobility control, Injectivity profile and viscosity modification, solvent, acid and biomass. In this study, soil samples were obtained from hydrocarbon-contaminated site in Gio, Tai Local Government Area, in Ogoniland, Rivers State, Nigeria. The samples were transferred into a polythene bag, placed in an ice pack, and transported immediately to the laboratory for physicochemical and microbiological analyses such as emulsification index, haemolytic activity and oil spreading technique. 37 isolates were tested for biosurfactant production and 3 of the isolates were selected for biosurfactant production with strong ability to degrade hydrocarbon. The selected microbes (Bacillus sp, Pseudomonas sp and Enterobacter sp) were identified by biochemical characterization and subjected to ranges of temperature, pH, nutrient sources, salinity, and inoculum concentration to determine their optimum reservoir performance conditions. The result shows the optimum parameter ranges for the three microbes: pH 7-8, temperature within 25 – 35°C, salinity within 0.5% - 5%, the result shows that as the inoculum size increases, the more the emulsification index, the best nitrogen source is peptone and the best carbon source for bacillus sp is glucose and glycerol for Pseudomonas sp and Enterobacter sp.
Solution to Limited Pressure BHP Data in Brown Fields; Material Balance Equation Approach
Authors: Agbodike Bright , Osokogwu Uche , Achumba Gabriel
Published: July 2019

Reservoir performance analysis and forecasting poses a challenge in brown fields with limited Bottom Hole Pressure (BHP) data. Most brown Oil Fields in Nigeria have the problem of limited BHP data. Most fields from 1960 to 1970 are having the problem because they were not properly managed from inception as per their data storage and recording systems. In Nigeria, many farm-out assets to the Marginal Operators from the International Oil Companies are having such challenges and managing such assets is daunting and time-consuming because of limited BHP data. Reservoir management is central to the effective exploitation of any hydrocarbon asset and is heightened for the development of brown fields. The problem of limited BHP data also makes reservoir pressure history matching difficult. This study proposes a workflow implemented on an Excel VBA program for a brown field in Niger Delta region of Nigeria with limited pressure (BHP) data. The program, which was validated, was used to history match the observed field production data, the limited reservoir BHP data, predict reservoir performance and production profile within the specified timeframe. The tool is built on Material Balance Equation which is a zero-dimensional-tank model created for the reservoir. Pressure Volume Temperature (PVT) properties with correlations, fractional flow models and Corey correlation for relative permeability estimates were incorporated in the algorithm. The matched model calculates the likely parameters of the reservoir and aquifer, then the production history calibrates the pressure model. The following approach is used in resolving the problem for the field case study. Production data aggregation; Calibration of PVT laboratory data; Calibration of reservoir pressure model; Development of fractional flow model for the system; Calibration of the reservoir's last production date.

This approach gives an accurate reservoir pressure history prediction, and also good production forecast in field with limited BHP data.
Experimental Investigation of the Macroscopic Displacement Efficiency of Locally Sourced Locust Bean Gum and Gum Arabic
Authors: Eiroboyi I. , Ikiensikimama S. S. , Oriji B. A. , Okoye I. P.
Published: July 2019

In enhancing oil recovery through polymer flooding, the application of polymers have been basically structured around the use of commercial polymers like xanthan gum, scleroglucan, Hydroxyl ethyl cellulose, Polyacrylamide, Hydrolysed Polyacrylamide and its derivatives. The use of some of these polymer has led to negative environmental issues and also increased treatment cost prior to discharge. The cost of some of the polymers is another reason, their applicability have not been appreciated so much in the oil and gas industry. The adoption of the principles of green chemistry in the synthesis of chemicals is a sure way of ensuring pollution prevention rather pollution control.

Analysis carried on these polymers showed good rheology especially at higher concentrations. The displacement efficiency of Locust bean gum (LBG) and Gum arabic were evaluated using 0.2wt% and 0.5wt% in hard brine to recover trapped oil after water flooding, the results reflected significant incremental recoveries from both the use of LBG and Gum Arabic which also correlated with rheological characterisation carried out under different saline conditions. This analysis was extended by carrying a comparative study with commercial Locust bean gum and Xanthan gum. The efficiency of locally sourced LBG and Gum Arabic revealed that they are both candidates for polymer flooding.
Development of Two-Phase Compressibility Factor Correlations Using a Stochastic and Robust Gradient-Based Optimization Algorithm.
Authors: Sheriff Adeyemi Temitayo
Published: July 2019

Accurate estimation of two-phase compressibility factor is of great importance in predicting the performance of a gas condensate reservoir using the material balance approach. Over the years, several correlations for estimating gas compressibility factor have been developed. Some of these correlations are; the Standing and Katz, Rayes etal, Dranchuk and Abou-Kassem, Brill and Beggs’ and Hall-Yarborough’s correlations. However, these correlations have not been so successful in predicting the compressibility factor of gas reservoir fluids in the two-phase region (below dew point pressure) and this explains why the industry still relies on the expensive and time-consuming constant volume depletion (CVD) approach. Therefore, this paper presents two different correlations for estimating two-phase compressibility factor using stochastic and robust gradient-based Newton-Raphson optimization algorithm. The first correlation presents the two-phase Z-factor as a function of pseudo-reduced pressure, pseudo-reduced temperature and the specific gravity. The second correlation on the other hand presents the two-phase Z-factor as a function of the single-phase Z-factor (obtained using Standing and Katz approach). Both correlations were developed using over 50 constant volume depletion (CVD) data of reservoir fluid samples obtained from gas condensate reservoirs around the world. Furthermore, in order to develop these correlations, two different models were proposed and the heptane-plus (C7+) and acid gas fractions were accounted for using the Sutton’s and Lee Kesler correlations respectively. Moreover, using the expected values of the pseudo-reduced pressure, pseudo-reduced temperature, specific gravity and single-phase Z-factor (all obtained using appropriate probability distributions) as the input variables, the optimum values of the models’ fitting parameters that minimize the sum of squares of the errors (SSE) were obtained using the stochastic and robust optimization algorithm(an algorithm obtained from Taylor series expansion of the error function and implemented on Octave programming language for the purpose of this study). Finally, having developed the correlations using 70% of the available data, the performances of these correlations were evaluated using 30% of the available data and the results obtained shows that these correlations outperform other pre-existing correlations.
Evaluating the Potential of Bio-Derived Flow Improver and Its Effect on Nigeria Waxy Crude
Authors: Fadairo Adesina , Ogunkunle Temitope , Oladepo Adebowale , Adesina Adedapo
Published: July 2019

A root cause of many oil industry production and flow problem is paraffin wax especially in cold and deep offshore fields which are at low temperatures. About 82 – 89% of the hydrocarbon produced in the world suffers when wax precipitates out and solidifies in the pore spaces and channels of flow, around the wellbore, in the production wells or tubing, perforations, pump strings, and rods, and the whole oil transport flow-lines systems. The flow capacity of waxy crude can be quantified and evaluated using the means of pour point measurement. However, the description of this property during the flow of waxy crude is insufficient because the waxy crude rheological properties depend on the viscosity history. Using gelation theory, viscosity – temperature data can be analyzed and used to characterize the temperature behavior of waxy crude as such crude has the tendency to gel at low temperature. This paper evaluates Nigerian Waxy Crude Oil using biodiesel based material as an additive. Laboratory measurements on rheology were carried out on the sample at low temperatures condition. The obtained data of shear rate and shear stress plotted. The dose of biodiesel derived additive in neat waxy crude oil was varied between 0.1 to 0.5 v/v at the operating low temperature. The experimental investigations furnish that there is significant decrease in rheological properties with the decrease in pour point and temperature upon the addition of biodiesel derived additive hence, significantly enhance the flow of waxy crude in a flow system.
Reservoir Architecture as a Driver for Effective Field Development Planning in an Un-Appraised Field; Kz field, Kazakhstan as a Case Study
Authors: Kakayor Omagbemi G.
Published: July 2019

Successful oil and gas field development in clastic reservoirs is usually dependent on the amount of subsurface data available to be evaluated during field maturation. The general rule is that more data reduces subsurface uncertainties. This invites expensive appraisal campaigns that invariably leads to delays in investment decisions and increased costs in development projects. The present study highlights how the understanding and definition of the architecture of the reservoir coupled with the use of analogue database as a methodology can be used to enhance hydrocarbon development in fields that are not fully appraised. The un-appraised Kz field is used as a case study.

Kz field, with an expectation In-Place oil of ca. 1150 MMstb is located SW of the Kashagan field in the Caspian Sea, Kazakhstan. The field consists of 11 stacked hydrocarbon-bearing reservoirs of varying thicknesses penetrated by a single exploration well. Due to the paucity of well penetration, subsurface uncertainty that impact on hydrocarbon volume and recovery is high. The methodology used was to combine the wells log and core data in addition to the use of sequence stratigraphic technique to derive sedimentological conceptual models. Analogue databases were then used to derive a geological meaningful range of dimensions for the geometry of the respective sand bodies. These ranges were then used an input for in-place volume ranges.

Evaluation results showed a volume range that could support a go-forward decision for further investment in the field. Based on these results, some preliminary field development decisions were taken prior to dynamic simulation. Decisions include; (i) Drill six wells (ii) Do Multi-zone Well Completions and (iii) use two drill centers to optimally develop the field (Phase-1). The key strength of this approach is that some key Field Development decisions can already be made before appraisal using basic sedimentological concepts and analogue database studies.
Considerations for Mitigating Early Water Breakthrough in Horizontal Wells in Heavy Oil Reservoirs in the Niger Delta - Ogini Field Case Study
Authors: Erivwo Ochuko , Ochai Josephine , Agbaroji Victor , Oke Oluwatobi
Published: July 2019

Horizontal wells are susceptible to early water breakthrough (EWBT) due to reservoir heterogeneity and "the heel-toe effect", caused by frictional pressure losses along the well that lead to a non-uniform production profile. Also, with heavy oil reservoirs, early water breakthrough can occur because of viscous fingering due to an unfavorable mobility ratio caused by a difference in the viscosity of heavy oil and water. This ratio leads to a high inflow of water into the wellbore.

EWBT is undesirable as it brings with it negative implications; from low oil productivity to corrosion in the wellbore and water disposal challenges. There are different industry solutions to managing early water breakthrough including reservoir based improved oil recovery (IOR) or enhanced oil recovery (EOR) methods such as thermal EOR (steam flooding, cyclic steam injection), chemical EOR (polymer or alkaline flooding) or miscible EOR (with methane or ethane to reduce capillary resistance). These methods are however complex and broad field-based applications with varying experiences in the outcomes of the field implementation. There are also mechanical well specific solutions for mitigating EWBT and in this paper, we present the considerations and plans for the application of Autonomous Inflow Control Devices (AICDs) for the mitigation of EWBT in the Niger Delta. AICDs are relatively new and are known for autonomous selective choking of fluid phases. They restrict the flow of less viscous phases like water while allowing more viscous phases like heavy oil to pass through, with minimum pressure drop.

The paper examines the different causes of EWBT in Ogini field and the different solution options available. It presents the cost/benefit analysis and modeling considerations resulting in the selection of AICDs for EWBT mitigation. The paper concludes with the technology implementation plan developed for its successful deployment in the upcoming drilling campaign.
Practical Deployment of Fluid Contact Tracking During History Matching for a More Reliable Reservoir Simulation Model: A Niger Delta Case study
Authors: Ogbuagu Frank , Silpngarmlers Lynn
Published: July 2019

The reliability of dynamic simulation models can spell the difference between value creation or erosion during the development of a hydrocarbon reservoir. There is a strong need to use every available data during reservoir characterization, earth modelling and history matching of the production and pressure history of the reservoir. Of greater importance is the need to blind test the history-matched simulation model, to ascertain its reliability, especially when the model is to be used for further development of the reservoir.

This paper details an offshore Niger Delta case study in which saturation logging results were used to blind test a history matched model, with an objective to further validate the model. The saturated oil reservoir was fully characterized using high resolution sequence stratigraphy and the earth model developed with available static data. History matching of the dynamic model was carried out using the parameter estimation approach, incorporating available dynamic data and tracking of contact movement observed in post-production wells. Following the history match, a saturation log was run in one of the producers in the reservoir, as a blind test for the quality of the history match.

Results of the log matched the contacts in the dynamic model within 1 ft, in the subject well, providing additional confidence in the quality of the model. As a result, matched model has been used for the maturation of 2 new drill opportunities with significant estimated recoveries.
The Rise of Business Process Outsourcing in Nigeria's Oil and Gas Industry and Implications for Industrial Relations
Authors: Igbatayo Samuel
Published: July 2019

Business Process Outsourcing can be aptly described as the process of forging a contractual relationship with external supplier for the provision of capacity that has been previously undertaken within an organization. In the global oil and gas industry, Business Process Outsourcing (BPO) has emerged in contemporary times as a potent tool in their operational mix. This is particularly hinged on the imperatives to find a delicate balance between rising global demand, diminishing reserves in some of the world's major oil fields, while managing distribution and operating costs. The collapse of crude oil prices from US$100.00 in May 2014 to about US$30.00 and even below in early 2016 has reinforced outsourcing. Empirical studies reveal that outsourcing of non-core activities may result in 25% cost saving associated with on-/near-site operations and as much as 50-75% for offshore operations compared to the cost of engaging in same activities in-house. Apart from cost-cutting, other benefits associated with BPO include a stronger focus on core competencies; improved regulatory conformity and compliance; as well as access to a larger talent pool and novel technologies. The oil and gas industry has emerged as the cornerstone of Nigeria's economy, accounting for about 70% of annual government revenue and more than 90% of the nation's foreign exchange reserves. Since the 1990s, outsourcing has assumed an increasing dimension in the nation's oil and gas industry. Empirical studies reveal, for example, that up until the early 1990s, employees in the oil industry comprised about 70% and 30% of permanent and temporary employees, respectively. The temporary employees were initially focused on non-core activities. However, in recent times core activities are increasingly contracted to service providers, reversing the structure of employment in the industry by 2010, with 40% of permanent employees, while 60% were permanent employees. The increasing replacement of permanent employees with temporary ones has fueled concern in the industry, led by labour unions, which have expressed concern about the sub-standard welfare of contract workers. This development has led the Federal government of Nigeria to issue guidelines on staff contracting and outsourcing in the Nigerian oil and gas industry.
Strategic Responses to Social Demands: Some Lessons for Marginal Oil Field Operators in Niger-Delta Region
Authors: Oruwari Humphrey Otombosoba , Dagogo Opiribo
Published: July 2019

Corporate social responsibility has become a business imperative as organization deliberately and strategically include public interest on corporate decision in an attempt to satisfy the demand of sustainable development. Balancing short term sight and long term perspective against triple bottom requirements in the face of rapidly changing social environment presents uncharted challenges and opportunities for businesses. For marginal oil field operators located in the Niger Delta, the region is characterized by poverty, underdevelopment and violent conflicts. The study investigated the strategies adopted by marginal oil field operators in the region to achieve competitive advantage and success. Combining several methodological framework through literature review and multiple firm level case study to examine the various strategies that marginal oil field operators in Niger Delta region adopts in their efforts to becoming social responsible corporate entity. Data gathering is through internet and review of existing literature. The study established that marginal field operators may apply different strategies in responses to social demands in their operating environment. It is observed that the dynamic response or interactive strategy have produced beneficial result by sustaining peace in their operating environment in the long run compared to reactive or adaptive strategy which might gain temporary benefits in the short run. The significance of the study is that it would benefit investors in marginal oil field development as it would provide an understanding of the challenges in the business environment and the different strategic responses needed to handle these challenges. The study recommends that investors in oil and gas business assess their operating environment carefully in order to develop strategies that would result in a cost effective way of managing business and bring about harmonious relationship between the host communities and the oil company.
Production Restoration Through Innovative Sourcing of Lift Gas - Jacket X Case Study
Authors: Ganiyu Adeyemi , Ochi Achinivu , Adebayo Olufemi , Oluwabiyi Awotiku , Chijioke Ibeh
Published: July 2019

Gas lift is one of the most common and economical methods of artificial lift deployed in mature oil fields in the Niger Delta. Availability of lift gas on the oil production jacket or platform is a critical enabler for gas lift initiation. Most mature fields do not have the luxury of gas lift supply on its jackets either because gas flowlines were not laid at inception or the gas flowlines are out-of-service due to integrity issues.

Jacket X had four active oil well streams producing on natural flow at inception. In early 2017, these wells stopped production one after the other due to low tubing head pressure (LTHP) because of increasing watercut and declining reservoir pressure. The wells were producing at a combined rate of over 1,000 barrels of oil per day (BOPD) prior to stopping production. Well diagnostic and preliminary Nodal Analysis revealed the need to place the wells on gas lift to improve the vertical lift performance. However, this could not be executed as jacket X was not on the field gas lift flowline network. Without conventional lift gas on Jacket X, it was imperative to source for the most economic means of getting gas on the jacket. This paper highlights the processes and methodology of sourcing lift gas through an existing idle wellbore.

During the bi-anual field review, the team of Operations personnel, Facilities Engineering and Asset Management reviewed and mapped out low cost strategy to restore production of the shut-in wells. Since most of these wells stopped production due to LTHP, improving vertical lift performance became the critical success factor. To address this issue economically, the asset team developed an ingenious method of sourcing the required lift gas on the same Jacket X through rigless well intervention on one of the existing idle wellbores. The innovative approach deployed involved identification of gas bearing reservoir in one of the idle wellbores, cement squeeze operations to provide zonal isolation, oriented perforation of identified gas reservoir, topside modification of existing wellhead configuration and eventual supply of lift gas to the casing of the shut-in wells.

Utilizing the lift gas, the wells were placed on gas lift with 1,100 barrels of oil and 3.5 MMScfd of gas restored to production. Significant cost savings were realized during the execution of this project through the application of rigless interventions which eliminated the requirement of laying new flowlines to deliver required lift gas to Jacket X.

Finally, this paper will share some of the challenges, lesson learned, and best practices adopted while executing this project.
Switching from Water Injection Scheme to Gas Injection Scheme for Improved Oil Recovery in a Niger Delta Oilfield
Authors: Akpabio Julius U. , Jackson Benson E. , Udie Celestine A.
Published: July 2019

The ‘JEB’ oilfield has been in operation since 1992 with 24 oil producing Wells, 8 water injection Wells and no gas injection. From inception, the field was producing at the rate of 27 MSTB/D. The gas produced was 34,333.7 SCF/D which was being flared but later supplied to the Nigeria Liquefied Natural Gas (NLNG) for export. The field had very weak aquifer support and therefore had been water-flooded from early days of its production. With high water cut, it was necessary to find ways of reducing water production and increasing oil production. The study involved field data gathering, history matching of the field data and prediction of future production. Production rates from the different production schemes were simulated for fourteen years. The cumulative oil production of gas injection, water alternating gas (WAG) injection and gas alternating water (GAW) injection schemes were 4.28 MMMSTB, 3.29 MMMSTB and 3.15 MMMSTB respectively representing an incremental recovery of 38%, 6%, and 1%. The cumulative water production of gas injection, WAG injection and GAW injection were 2.65 MMMSTB, 6.52 MMMSTB and 6.90 MMMSTB respectively, which represent 64%, 10% and 5% reduction in produced water. The economic analysis showed gas injection as the best alternative injection scheme for the field with internal rate of return (IRR) of 19.26 %, while the IRR of WAG and GAW injection schemes were 12.09 % and 11.22 % respectively. Also, at 15% discount rate, the gas injection scheme had the best result with a Profitability Index (PI) greater than 1, a positive Net Present Value (NPV) while all other injection schemes had negative NPV and PI was less than one. The possibility of changing a field from water injection to gas injection has been explored, hence, before embarking on any enhanced oil recovery scheme, other alternatives should be evaluated.