bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cement Spacer Technology Eliminates Costly Remedial Jobs While Providing Excellent Bond Logs
Authors: Ilesanmi Oluwagbemiga , Gill Stephen , Hilal Bashar , Kulakofsky David 
Published: July 2014

Abstract
The significant and continuing loss of mud and/or cement slurry to a formation during drilling operations is one of the most troublesome problems affecting the oil industry. These problems impart a substantial negative impact on well economics.
Loss circulation problems have been identified as one of the most costly and time consuming problems faced in the oil and gas industry. It has been globally estimated that these problems causes drilling industries close to a billion dollars annually in rig time, materials, and other resources.
This paper will describe in detail the nature of the losses and application used to resolve the problem. The use of this unique cement spacer technology is a viable means of resolving most of these problems. This technology, can be applied to strengthen a wellbore, even with when a degree of losses are expected, as a preventive method where fractureing during cementing may occur due to predicted increases in hydrostatics, frictional factors, or both (ECD). In addition, it can also be used as a corrective method in cases where the wellbore is already experiencing losses.
Case histories will be presented describing how this novel spacer cured losses from seepage, moderate, severe and complete loss of returns. The applications include very low fracture gradients wells, where it was impossible to cement with dual slurry with lightweight slurries.
Additional benefits of the spacer is that it is 1) non-damaging, 2) minimizes filtrate invasion from the cement, 3) eliminates or at least drasticly reduces induced losses while cementing, and 4) it forms a permeability barrier membrane on the inside face of the wellbore (Figure 1) wall in-affect strengthening the wellbore allowing successful placement of the cement slurry which in-turn can provide long-term zonal isolation. Formation damage testing with this spacer shows near 100% return permeability.
The spacer rheological can be adjust from low values which minimize increases in ECD to higher YPs as required to enhance mud removal
Comparative Analysis of Geomecahnical Parameters Using Cores, Sonic and Gamma Ray Logs for Optimal Well Design
Authors: Dosunmu Adewale , Odagme B. S , Paul Fekete , Anyanwu Chimaroke , Ekeinde Evelyn , Odusegun Olufela C 
Published: July 2014

Abstract
Geomechanics data are usually dependent on log data and reservoir rocks often deforms due to depletion in the life of a field. These changes occur as a result of changes in the stress on such rocks which are imposed by drilling, production and injection activities and these changes can be unfavourable to the operators when drilling new wells in the same field. Thus, these changes have to be accurately predicted and mitigated (if undesirable). In this study, the accuracy of these vital geomechanical parameters obtained through sonic and gamma ray logs were compared and a correlation between both was established. Comparison was also made with respect to key indices including cost, safety, ease of acquisition etc. Only Unconfined Compressive Stress (UCS) as a geomechanical parameter was evaluated using several logging methods. The correlation coefficient range of 0.993 to 1 for various well logs analysed from the unconfined compressive stress obtained from the Sonic and Gamma ray logs. This would prove very useful especially for the marginal field operators in Nigeria and mature fields that do not have sonic logs as it would enable a more accurate derivation of geomechanical properties and the accruing benefits of a geomechanical analysis study. The nagging limitation of the Petrophysical log approach is the accuracy of the logs as spurious correlations were noticed from defective logs.
Investigating the Effects of Contaminants on the performance of Mineral Oil Based Versathin Dispersant
Authors: Kumapayi Olamide , Bello Kelani , Adekomaya Olufemi , Akintola Abidemi , Dala Joshua , Mohammed Ismail , Olafuyi Olalekan 
Published: July 2014

Abstract
Flocculation occurs when particles in the drilling fluid agglomerate due to particle to particle attraction thus leading to uneven distribution of weighting material within the fluid. Dispersants majorly are used to deffloculate fluids that have these tendencies, and their performance lies in the ability to minimize sagging and hence control drilling fluid rheology(Yusuf et al).
This work was undertaken to investigate the effect of clay and sea water (containing calcium and magnesium ions) contaminations on dispersant performance used in an oil based invert emulsion drilling fluid system. Barite (Ba2SO4) was used as the weighting agent; the based fluid used for the oil based invert emulsion mud was EDC-99, a specialized kind, different from the conventional diesel oil.The fluid were analysed before and after aging using, rheometer, filtration and emulsion stability tests.
The dispersant employed for the fluid system was Versathin ®. Versathin is an oligomeric fatty acid in mineral oil, an oil-based dispersant which tend to also perform excellently in the invert emulsion system. From the experimental results, a general decrease in fluid rheology was observed in the dispersant sample as compared with the blank sample. The emulsion stability of the fluid decreased as contaminants were added, fluid loss increased when contaminants were added to the dispersant samples. Contaminations also increased the plastic viscosity and yield point for the dispersant sample but all were still within the API range. Increase in LSYP in the presence of sea water and clay revealed that sag may be less noticeable when drilling reactive formations, confirming earlier studies on water based mud and the suitability of clay as rheology controllers. Cumulatively the result shows that Versathin oil based dispersant can control flow behaviour of fluids when employed in the oil based invert emulsion system.
Antimony Sulphide Stibnite and Potash as Local Substitute to Barite and Lignosulfonate as Drilling Mud Weighting Additives
Authors: Onu Ogbonnaya Victor , Ikponmwosa Ohenhen 
Published: July 2014

Abstract
A modified Antimony sulphide, locally called Tiro (stibnite) was employed as a drilling mud weighting material due to its relative weight and apparent health safety, as a substitute to expensive and imported Barite. Potash, commonly known as Kaun or Akaun in Nigeria, better called ‘Cooking Potash’ was also employed as a substitute to Lignosulfonate as a thinner in drilling mud.
The implication of using the Tiro and Potash were compared with that of conventional Barite and Lignosulfonate respectively in this project. Result obtained showed that Barite gave better weighting strength than tiro, it was also observed that the effect Barite on mud pH is lower than that of Tiro. Unfortunately, it was observed that the effect of barite on mud viscosity as weight of Barite increases has a severe effect on the viscosity of the mud. In that of Tiro, viscosity was maintained until some percentage weight of Tiro in the mud. For mud used in drilling dangerous zone, Tiro may be a better substitute to Barite due to Tiro's lower negative effect on viscosity if the safety of the well is of high consideration.
For the thinners, it was noticed that both Potash and Lignosulfonate have similar reducing influence on the mud weight, after which the Potash caused a radical reduction in mud density with increasing weight percentage of the additive. Both thinners had a reducing effect on the pH of mud at first after which the mud pH remained constant irrespective of additive increment. Mud pH is desirable between 8–10 for optimum hydration, since the percentage reduction of Potash is lower compared to Lignosulfonate, this puts Potash more relevant than Lignosulfonate. Also when there is need to quickly reduce the mud density due to the possibility of loss circulation as a result of over weight mud, especially when an abnormal low pressure zone is encountered during drilling operation, Potash would be a better alternative thinner as it causes rapid reduction in mud density.
Maximising Oil Production by Well Operating-Envelope Review to Arrest Production Decline in a Deepwater Field
Authors: Okosun Joshua , Ajayi Ayotunde , Olatunji idris , Lawal Kazeem , Ogunsina Oluseye 
Published: July 2014

Abstract
Well operating envelopes are defined to ensure optimal production performance, while maintaining completions integrity. Operating envelopes (OE's) however, have to be kept live to reflect the dynamic nature of well performance. This paper presents how the operating envelops of subsea production wells in a deepwater field are being monitored and utilised as enablers to realising production targets without compromising relevant constraints such as reservoir pressure, drawdown and well integrity.
A review of the current parameters employed to determine the required well operating envelope was carried out with a view to ascertain any window of opportunity for optimization. Downhole velocities, drawdown, produced sand/fines data were evaluated to help mitigate completion impairment and loss of installed sand control equipments.
An extensive post implementation analysis was also carried out to help revalidate the basis of well operating envelope. This provides a platform for remedial action, as any deviation from expectation is found out. This paper will provide an overview of how the operating envelope for Producer 1 was reviewed and implemented to maximize production from reservoir Z. The methodologies and workflow will be discussed extensively to demonstrate how the Field team has effectively arrested production decline in the Z reservoir by proactive review and update of its wells operating envelopes.
Distinguishing Strategies for Hydrocarbon Value Maximization in Africa's Energy Corridor: A Case Study of Zerkel Asset.
Authors: Maduawia Emmanuel , Matemilola Saka , Kaars-Sijpesteijn Casper , Enu Emmanuel 
Published: July 2014

Abstract
Although organizations spend lots of money to acquire assets for her legitimate and profitable use; observations have shown that some organizations hardly manage their assets efficiently and effectively; hence many firms have and if not, will in no distance time face significance asset management challenges.
Using Zerkel asset as a case study, this paper presents a description of how vision re-enactment via leadership, staff re-orientation and timely delivery of processes served as effective management strategies to rejuvenate hydrocarbon production within a short time frame.
High Prevalence of Modifiable Cardiovascular Risk Factors Among Male Off-shore Workers in Nigeria-A Preliminary Study
Authors: Chijioke Iroezindu Israel , Raymond Ruthvin , Michael Felfernig 
Published: July 2014

Abstract
Background: Internationally, Cardiovascular diseases (CVD) constitute a major cause of morbidity and mortality and it is estimated that by 2020 a majority of the global burden of CVD will be in developing countries. Offshore workers are often more prone to CVD due to unhealthy lifestyles however, the risk of CVD to this population is largely unknown in sub-Saharan Africa. Our study determined the prevalence of modifiable cardiovascular risk factors among off-shore workers in Nigeria.
Methodology A descriptive cross-sectional study was carried out amongst male off-shore workers in the Niger delta area of Nigeria from January to December 2012. Participants of the study were recruited consecutively during periodic medical fitness for work examinations where sociodemographic data, anthropometric measurements and blood pressure were obtained in a standardized manner.Venous blood samples were collected in the fasting state for glucose and lipid profile including total cholesterol, triglyceride, HDL and LDL, all of which were analaysed using dry chemistry technique (Reflotron® System, Roche Diagnostics, Germany).
Results This study looked at 375 male offshore workers with a mean age of 42.6 ± 7.1 years. Forty-one (10.9%) and 196 (52.3%) had a history of cigarette smoking and alcohol consumption respectively. The prevalence of modifiable cardiovascular risk factors screened for were: hypertension 139 (37.1%), diabetes mellitus 30 (8.0%), obesity 154 (41.1%), hypercholesterolaemia 80 (21.3%), lowHDL 30 (8.0%), highLDL 66 (17.6%), and hypertriglyceridaemia 53 (14.1%). Disorders that occurred more frequently in older patients were hypertension (p=0.002), diabetes (p=0.002), obesity (p=0.02) and hypercholesterolaemia (p=0.04). About 19 (63.3%) of subjects with diabetes mellitus and 52 (37.4%) with hypertension were unaware of the diagnosis prior to the on-site screening.
Conclusion The prevalence of modifiable cardiovaascular risk factors among off-shore workers in Nigeria is high. In order to prevent unwanted cardiovascular events in this group, a healthy lifestyle, frequent health screenings and other work place-based health promotion activities should be ensured.
Production Analysis for Solution Gas-Drive Reservoirs: General Variable Pressure/Variable Rate Case –Theory
Authors: Mohammed S. , Amarfio E. M. , Dankwa O. K. 
Published: July 2014

Abstract
Presently, analytical models for estimating reservoir parameters for solution gas-drive are restricted to either constant pressure or constant rate assumption. Thus, current models for solution gas-drive do not allow for rigorous analysis of simultaneous variations in pressure and rate. In addition, the traditional material balance time or pseudotime, which models variable pressure and/or variable rate case, is limited to single-phase flow.
This paper proposes a normalized multiphase pseudotime function that is capable of modeling general variable pressure and/or variable rate data for solution gas drive reservoirs during boundary-dominated flow. In particular, we present a multiphase flow equation that incorporates this pseudotime function. This flow equation is expressed in a form that traces the rate/time harmonic depletion curve. Thus, the proposed approach allows analysts to use a single depletion curve to model constant rate, constant pressure and variable pressure/variable rate cases for solution gas drive reservoir systems.
In addition, we propose a multiphase pseudocumulative function that is normalized by pseudopressure drop to permit the extension of flowing material balance method to solution gas drive. This is essential since analysis using flowing material balance method offers a better resolution than decline type curves. It also permits the computation of initial-oil-in-place.
The significant contribution of this paper is the generality of the proposed model that allows the rigorous handling of variable pressure and/or variable rate case for solution gas drive reservoir systems. Thus, the proposed approach, as opposed to existing models, is not limited to production constraints.
Only the appropriate equations and the methods of analyses and interpretation are presented in this paper. Illustrative examples are deferred to a subsequent writing.
OML-XYZ Production System Debottlenecking Using IPM
Authors: Ekeke Davis , Basu Subhayu 
Published: July 2014

Abstract
OML-XYZ is one of the largest producing and mature assets in Addax Petroleum Nigeria Limited and for a number of years, as drilling activity and the attendant well production potential have increased, has experienced bottlenecks in its production system (production potential recorded during testing of new wells was not fully released at FPSO after hook-ups to production line, even factoring in expected pipeline losses).
In some cases, after new producers were brought on stream, there was no noticeable increase in throughput at FPSO. Combining the complexity in the field architecture layout (evidenced by the number of well head platforms, well hook-up points, oil and gas-lift pipelines network & other surface facilities) and the lack of access to real-time pressure & production data, it was difficult to establish reason behind bottlenecks detected in the system.
A production system network model was constructed with the purpose of simulating functional relationships between fluid flow and pressure drop at critical nodes in the production system, such as well head, manifolds, pipelines and separators for different operating conditions.
This paper addresses the OML-XYZ production system and reviews the methodology of capturing flow behavior from reservoir to FPSO, utilizing an integrated production model (IPM). In identifying OML-XYZ production bottlenecks using the IPM, daily field data was reasonably matched and was subsequently used for short and medium term production forecasting, field monitoring, production optimization and facilities requirements. Results of production optimization studies showed that considerable production gains could be achieved through gas-lift optimization and targeted facilities upgrade.
Some examples of preliminary gains from this optimization are also presented.
Well Testing: A Geological Interpretation Tool
Authors: Animashaun M. B. , Nwakaji N. F 
Published: July 2014

Abstract
We acknowledge well testing as a reservoir engineers' tool and the importance of geological information in most aspects of interpreting well tests. Conversely, the well testing provides more reliable geological information and dynamically verifies the proposed geological model and sometimes updates the contents of geological description. This paper aims at reviewing the geological interpretation of the reservoir using well testing though it is subjective.
The first section of this paper is a review of essential geological data to get prior studies, static and dynamic modelling. The potential risks of a reservoir engineer working in isolation from the geoscientists are highlighted.
The second section evidences more detailed geological information about the reservoir such as reservoir continuity/compartmentalization, channels, facies, initial reservoir pressure, permeability and anisotropy (heterogeneity)
The third section emphasizes the importance of the geological description from well testing interpretation conforming to the static model.
Dynamic Modelling of Stacked Complex Reservoirs Using Experimental Design for Full Scale Smart Field Development in Niger Delta: Lessons Learned
Authors: Nwonodi Chike , Onwuchekwa Chukwuma , Campero Manuel , Eke Kenneth , Madu John , Adenaiye Niyi , Umoh Magdalene , Oluwaseyi Adekoya , Igogo Arit , Anosike Ebere 
Published: July 2014

Abstract
3D reservoir modelling of stacked reservoirs is often difficult, due to interplay of various uncertainties related to heterogeneity of the sand units modelled together within the stack. In the past, reservoir simulation had been used to model stacked reservoirs for commingled wells with varying predictive capacity. Typically, dynamic models use conventional approach in assessing uncertainties, involving discrete sensitivity of uncertain parameters and often lack robust subsurface uncertainty management. Additionally, handling dynamic cross flow issues by modelling of control valves in such cases presents production allocation challenges. Huge man-hours are needed for several run times, without achieving relatively good history-match and predictive capacity. As a result, only base-case history-matched model is developed; thus robust assessment of impact of sub-surface uncertainties on the predictions is usually inadequate.
This paper details a multidisciplinary approach adopted in integrated dynamic modelling of stacked reservoirs in a Niger Delta field using experimental design methodology. The phased development was aimed at full-scale reservoir development of multi-zone and commingled wells. Instead of single average for each sand unit, facies-dependent kvkh values were required to adequately capture reservoir heterogeneity for the complex depositional environment. Field-wide history-matches for 23 reservoir blocks and over 70 individual conduit matches were done to calibrate the simulation models. Model robustness was conducted through blind-testing and calibration with carbon-oxygen and openhole log data from newly drilled wells.
From the model predictions, recoveries for existing conduits from simulation models were benchmarked against Decline Curve Analyses and the results compared closely. Response Surface Models were used in selecting best history-matched realizations. 1P, 2P and 3P models were selected from the ultimate recovery probability distribution curves of these history-matched realizations. The modelling of interval control valves settings within the stacked models and use of smart well routines assisted evaluation of recoveries from planned commingled wells.
Managing Injectors Impairment in a Deepwater Field
Authors: Olatunji Idris , Ogunsina Oluseye , Okosun Joshua , Kazeem Lawal , Ajayi Ayotunde , Adenuga Ademola , Abiola Olayinka 
Published: July 2014

Abstract
In this deepwater soft rock field injected water is equivalent to oil as the reservoir management strategy is to maintain 100% voidage replacement and keep reservoir pressures above bubble point. The producers are high rate wells operating at 10-50kbpd range. This means the injectors are always expected to inject reliably at high rates.
However, over the life history of the field, waterflood performance has been one of the limiting constraints on achieving full potential of the field. Water injectors' impairment and failure has contributed immensely to this challenge of waterflood performance. A lot of efforts have gone into understanding the cause of these impairments and failures and the means to eliminate them. At the beginning of the field life, the impairment observed was mostly attributed to poor injection water quality. Water hammers resulting from trips were also identified as another cause of impairment.
The earlier wells were completed as Frac & Pack wells and there were attempts to understand how this completion types impact the impairment particularly as regards whether the proppants will be intact after significant amount of injection. In recent times, horizontal wells are being drilled and though the data from them is still limited, possible impairment models are being developed for them as well. The choice of the mode of injection – fractured or matrix – also seems to impact on the impairment mechanism of injectors.
Increase of the injection pump discharge pressure have been attempted to manage wells' rate and pressure interaction with each other through the subsea flowlines. The extent to which this can be carried out is limited by the pressure rating of topsides, the subsea equipment and the shale (cap rock) strength.
Consideration of all these factors has improved understanding of impairment mechanism which in combination with learning's from operational procedure that led to failure of injector wells has resulted in better management and improved the operating envelope for these wells. Reduced failure rates have been observed in longer well's life for newer wells than earlier ones. It has also led to development of mitigation measures like backflushes, refracs and acid stimulation when impairment is being observed.
There is still a large area of uncertainties or gaps in current understanding, although plans are being made for data gathering e.g. HUD checks, downhole gauges, injection profile logs and temperature warm- back logs to further to close the gaps in the existing impairment models for the water injectors.