bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling of Cement Thickening Time at High Temperatures With Different Retarder Concentrations
Authors: Umeokafor C. V. , Joel O. F. 
Published: February 2011

Abstract
Primary cementing is the process of placing cement between the casing and borehole in a well. The main objectives of primary cementing are to seal the annulus and to obtain zonal isolation. For zonal isolation to be achieved, all drill cuttings and drilling fluid must be removed from the annulus and replaced by cement slurry. Cement slurry must then undergo hydration, changing from the liquid to the solid phase and developing properties to prevent flow of formation fluids and to support the casing. The cement sheath should also be able to withstand different operations such as stimulation, perforation, production, and intervention during the life of the well. Adequate thickening times are required for a good cement job.
Study was made with 36 thickening time test results carried out for a 5 inch high temperature liner cementing jobs done in the past at temperature range of 230°F to 284°F for different retarder concentrations. Thickening time plots for the retarded cement slurry was obtained for the temperature range investigated. Model which predicts thickening time at the specified retarder concentrations and temperatures was developed. The model equation at the different temperatures and retarder concentrations is given by: Y = 32.53882954 − 0.15380761X1 + 12.10530547X2 + 29.80930457X3.
Thickening times predicted showed good agreement with experimental values with less than 10% deviation. The model equation developed will help predict the thickening time at the various retarder concentrations and temperatures and thereby help in saving time and cost associated with the rigour in actual laboratory experimental recipe design and testing.
Density Measurement of Vegetable and Mineral Based Oil Used in Drilling Fluids
Authors: Hussein Adil Mohamed , Amin Remy Azrai 
Published: February 2011

Abstract
Normally, calculated frictional pressure losses do not match actual frictional losses recorded during drilling operation. Discrepancies between calculated and measured pressure losses are more severe in operations where synthetic based drilling fluids are used because synthetic based drilling fluids density and rheology varies with changes in down-hole conditions. In order to deal with this phenomenon, a comprehensive experimental study was performed to predict the densities of vegetable base oil (derivative of ester), mineral base oil (commercially used in the formulation of drilling fluids) and their blend at elevated pressure and temperature. In the experiments, the temperature ranged between 80F-300F degrees F and the pressure ranged between 50psi- 5000psi. The data showed that when the pressure increased at the constant temperature conditions, the volume of the based oil reduced. The data analysis also shows the importance of introducing the effect of pressure and temperature on the density of the based oil for the pressure loss calculation during drilling activities. The blend of vegetable based oil with mineral based oil showed more tolerance in High Pressure High Temperature (HPHT) down-hole conditions. In addition to that, part of the study focused on developing an empirical linear equation that related density change in pressure and temperature. Liner regression technique was used in this purpose. It was found that the empirical equation was accurate in estimating the experimental result. On the other hand, it was observed that the mineral based oil sample was more compressible and subject to higher thermal expansion than the vegetable based oil and their blend.
Gas Lift Optimization Under Facilities Constraints
Authors: Djikpesse H. A. , Couët B. , Wilkinson D. 
Published: February 2011

Abstract
Gas lift optimization is often used to enhance production of mature oilfields consisting of multiple reservoirs. For efficiency, several of those reservoirs often share the same surface processing facilities. In such context, we wish to find the optimal allocation of gas lift over an entire network of wells and pipelines, while accounting for the constraints imposed by the reservoir operating conditions.
In this study, we describe a novel, cost-effective approach to perform such optimizations involving non-smooth models and subject to expensive constraints that might be simulation-based and as costly to compute as the objective function. After classifying all constraints depending on their computational cost, points not satisfying simple linear constraints are feasibilized before evaluating expensive constraints. A sequential lexicographic ordering is applied in which the linear constraints take precedence over nonlinear constraints and inexpensive nonlinear constraints take precedence over expensive ones, which in turn take precedence over objective function values. Two oilfield-production optimization examples serve to demonstrate that the performance of the proposed method is much faster than the traditional ones.
Understanding the Influence of Rock Stresses on Wellbore Inclination in Salt Formations: A Well Planning Approach
Authors: Omojuwa E. , Okoye E. , Ousseni A. , Odunuga A. , Osisanya S. , Ahmed R. 
Published: February 2011

Abstract
With the growing trend of pre-salt discoveries, some salt formations cannot be simply bypassed to get to the reservoir. A considerable thickness of salt of up to 15,000-ft is usually encountered in the deepwater areas. Salt structures embedded within the hydrocarbon prone formations have contributed to the complexities of well trajectory design and operations. Salt domes are impermeable cap rocks for petroleum accumulation but the stress distribution and geo-mechanical dynamics within and around them limit the success of directional drilling. Creeping is the major behavior of salt formations.
This study presents a new stress analysis model for rock salt formations based on the octahedral shear stress theory and von Mises failure criterion. The model determines the second deviatoric stress invariant called octahedral shear stress. The stress model also includes the Maxwell's Creep Model in the formulation of the time-dependent response of salt formations to changes in octahedral stresses within salt structures due to the inherent visco-elasto-plastic properties of salt. Results obtained from the stress model show that the octahedral shear stress values in salt formations prior to drilling are dependent on the three principal stresses exerted by neighboring formations while the octahedral shear stress values in the salt formations during or after drilling are dependent on the minimum horizontal stress, wellbore pressure, wellbore radius, and the radial distance from a selected stress center. The stress model can be used to estimate the extents and distribution of the octahedral shear stresses within and around the salt structures prior to drilling and after drilling using the available stress data from geo-mechanical models. The position and inclination of the wellbore can be selected in a less-stressed zone within the salt formation. The case study for this study is the 3D-geomechanical model of a salt diapir from the Officer Basin, South Australia, subjected to long period of deformation. This paper concludes with the description of the suitable bottom-hole assembly (BHA) and drilling practices for successful drilling through salt structures.
Deep Water Oil Exploration and Development Using Satellite Technology
Authors: Kio M. T. , Agboola A. O. 
Published: February 2011

Abstract
Satellite imaging has come a long way since the first satellites used to cover the earth surface explorer VII, was launched into orbit. From simple detection of key earth features to the pin point, precise stratigraphic of earth points or massive surface features, satellite imagery provides better and improved imaging of the earth surface with the ability to get spatial resolutions of less than 1m from low earth orbit (LEO) and repeated ground swaths which generate clear images from space. The benefits of the remote oil prospecting abilities presented by satellites shows its viability in obtaining oil information from hitherto inaccessible areas located either within hostile regions or in deep sea areas. The unsuitability of using exclusively traditional techniques like sonar in certain coastal areas makes space based oil prospecting a growing alternative. With the ability to launch cheaper satellites becoming more of a reality, different types of LEO sensors (optical and radio) can effectively contribute to all day and all weather prospecting and coverage from space. The cost of space based oil prospecting lessens the overall cost of oil production in terms of time (operation), the number of equipment involved and the human resource which goes to reduce the cost of production per barrel. The flexibility inherent in using these LEO satellites for this purpose is also highlighted in the fact that the satellites play other earth mapping functions along side providing information for oil prospecting. SAR satellites and even high resolution optical satellites use oil sleek images to determine presence of oil deposits and formation configuration.
Enhancing the Injection Profile in Rahama Field - First Time in Egypt
Authors: Shaheen Tarek , Hamdy Ahmed , Dilling Lambert , El Khalik Tamer Abd 
Published: February 2011

Abstract
Water Injection is considered to be one of the most important ways to enhance oil recovery. Although all of the Injector wells in Rahma field in Egypt were stimulated before using hydraulic fracturing however, they were still suffering from severe decrease in the injection rates which are far below the target.
As a first time to be done for Qarun Petroleum Company (QPC), a full technical study has been done to the field in order to identify the main reason for the severe decrease in the injection profile which was formation damage and high increase in the skin value. Based on the study done, a technical treatment was designed and Matrix Stimulation Engineering was implemented to the well Rahma-12 as the first candidate for Matrix Stimulation.
The results were successful, the injection rate increased in the well Rahma −12 from 280 bwpd to 3000 bwpd and in the well Rahma-10 from 300 bwpd to 2800 bwpd. These successful results encouraged QPC to implement the Matrix Stimulation treatment in all the injector wells in the Rahma field which resulted in great enhancement to the injection profile in the field.
This paper discusses the full technical study done to the field and the chemical tests done in the lab in order to design the best treatment to the formation. It shares the experience gained during the execution phase and new best practices that were implemented first time which resulted in a great success. Finally it provides a useful data base for the field and the Matrix Stimulation Operations which were done first time in QPC fields.
The Preferred Natural Gas Conservation Option: Underground Storage of Natural Gas
Authors: Atoyebi Temitope Mariam 
Published: February 2011

Abstract
The need to conserve energy sources has gained awareness in the world. Natural gas which is a kind of energy source is oftentimes wasted either in the form of gas flaring or venting, These practices had generated great concerns in the world.
The aim of this proposal is to emphasize the need to conserve natural gas through storage. The different types of natural gas storage methods were compared in order to select the most viable option.
The Underground gas storage method (UGS) was selected as the preferred option and it was discussed.
Most importantly, a software was developed to perform economic analysis for the different storage methods and the determination of the UGS performance evaluation parameters.
Exploring Opportunities for Indigenous Participation in the Implementation of the Nigerian Gas Master Plan
Authors: Akinpelu L. O. , Omole O. A. , Falode O. A. 
Published: February 2011

Abstract
The involvement of Indigenous Entrepreneurs and Host Communities in the Implementation of the Gas Master Plan will have far reaching effects on the Nigerian Economy. The consequences of the neglect of this crucial element in the Oil side of the business are well known – enclave nature of the Industry with no multiplier effect on the rest of the economy, virtual control of a strategic sector that generates over 80% of total revenue in the hands of competing IOCs with a multiplicity of interests, little technology transfer and minimal Human Capacity Development. Wide spread alienation and agitation for Resource Control manifested over time and the Country is just now struggling to contain the damaging effects on the Oil & Gas Industry. These mistakes need not be repeated in the Emerging Gas business.
Three stakeholder Groups were identified in the consideration of opportunities for Indigenous participation: The Indigenous Entrepreneur, the Host Community Contractor and the Host Community Residents. The segmentation of the different Stakeholder Groups is deemed necessary in order to focus on the specific interests of each Group.
Criteria for Selecting a Candidate Well for Hydraulic Fracturing
Authors: Heydarabadi F. Roshanai , Moghadasi J. , Safian Gh. , Ashena R. 
Published: February 2011

Abstract
Hydraulic fracturing is the process of inducing a highly conductive path from the reservoir to the wellbore, thus increasing the productivity of the wells. The final success of hydraulic fracturing greatly depends on candidate well selection. Accordingly, selecting the proper candidate well is of crucial importance. This paper sets a series of criteria for assisting the process of candidate well selection for hydraulic fracturing. The IPR and correspondingly productivity index variations after hydraulic fracturing as case studies of several wells in one of Middle Eastern oil fields have been studied in this work in detail.
This paper can be used in the selection procedure of oil and gas wells for fracturing treatments. A detailed modelling of hydraulic fracturing candidate criteria selection would facilitate the task of identifying a proper candidate for this expensive job.
The most important parameters suggested are the in-situ stress profile of the well, the magnitude and direction of the in-situ stresses and the formation permeability. In this study, the pre-construction of the inflow performance models of the fractured and non-fractured well is considered as a tool in candidate well selection procedure. Well models presented here show the extent to which hydraulic fracturing improves the production performance of the well.
The previous works concerning candidate well selection for hydraulic fracturing do not put all the deciding parameters together in a clear order. This paper tries to summarize all criteria which must be evaluated during the candidate selection process based on experience and careful observation of the previous successful and failed jobs.
Mechanical Stability Analysis of Directional Wells: A Case Study in Ahwaz Oilfield
Authors: Zare M. R. , Shadizadeh S. R. , Habibnia B. 
Published: February 2011

Abstract
Ahwaz oilfield is one of the southern Iranian fields in the Middle East that are located in reverse fault stress regime. Wells A and B are two deviated wells with same drilling conditions that produce oil from Bangestan reservoir in Ahwaz oilfield. Numerous cases of borehole instability, stuck pipe, and borehole collapse have been reported while drilling well B. These problems cause highly increasing of drilling operation cost of well B. However, well A has been drilled without any serious problems. To investigate and avoid these problems and improving operating costs of drilling, a comprehensive mechanical stability analysis is essential. To do so, a computer program is developed to analyze the mechanical stability of these deviated wellbores. The mechanical stability analysis reveals that in the reverse fault stress regime, drilling in direction of maximum horizontal stress is the most stable direction. But drilling in direction of minimum horizontal stress, leads serious borehole instability and borehole collapse. Comparing the results with trajectory of two deviated wells, show that well A has been drilled in direction close to the maximum horizontal stress while well B has been drilled in direction of minimum horizontal stress. As result well A must be more stable than well B. Base on the results the best drilling direction in Ahwaz oilfield is parallel to maximum horizontal stress.
Mechanistic Modeling of Annular Two-Phase Flow While Underbalanced Drilling in Iran
Authors: Ashena Rahman , Moghadasi J. , Ashena Rahim , Roshanai F. , Sarmadivaleh M. , Safian G. 
Published: February 2011

Abstract
The difficulty of maintaining the wellbore pressure should be overcome by precisely predicting the wellbore pressure. The empirical models used widely by UBD simulators give a large error and may not be extendable to other UBD cases. For this reason, Mechanistic modeling has been applied to two phase flow with a number of assumed values for the existent coefficients varying from one UBD case to another. Therefore, in this paper, a new comprehensive mechanistic model is developed mathematically for Iranian Oil fields to match the characteristics of the corresponding UBD jobs in Iran by modifying the constant values of Lage et al, Perez Telez at al., Mousavi et al. and Ansari et al. mechanist models. It is compared with Ansari et al, the specifically developed mechanistic model for use in South of Iran.
Since the mechanistic models use mathematical relations with assumptions for the values of the constants rather than pure empirical study of two phase flow, the mechanistic models developed and validated with data outside Iran are not good enough to be used. In this paper different constant values have been tested and the ones which have led to the least average absolute error have been picked up to present a specific mechanistic model for South of Iran.
The empirical models which have been developed outside Iran cause erroneous results. The results illustrate that the new mechanistic model predicts BHCP with an error much less than Ansari et al. Mechanistic Model.
In this paper, it is shown that the development of mechanistic models to predict the flow behavior of two phase flow and transition patterns is a necessity to escape the incompatibility of correlations with the regional flow restrictions. Also, the Ansari et al model's lower performance has been diagnosed and tried to be removed. Very few mechanistic models have been developed to respond to the fluid flow parameter prediction requirements for use in UB drilled wells of Iran.
Prediction of Lost Circulation Using Virtual Intelligence in One of Iranian Oilfields
Authors: Moazzeni A. R. , Nabaei M. , Jegarluei S. Ghadami 
Published: February 2011

Abstract
Nowadays, huge human needs for energy forced petroleum and drilling companies to drill deeper into the earth which means spending more time on drilling and passing through numerous layers with different layer characteristics to hit the target. Since major part of a well cost depends on the duration of drilling phase, an organized drilling program seems vital to save the time and cost. Occurrence of different drilling problems like lost circulation and pipe sticking may deviate the drilling operation from the schedule. Mechanical pipe sticking is likely to occur after complete loss.
Lost circulation is one of the common drilling problems in the industry which expose heavy expenses to the oil companies. This problem commences from beginning of the drilling and continues till putting the casing in place. Mud loss can occur in low fluxes up to complete loss that finally can lead to well blowout or severe pipe stuck. Freeing the pipes may waste a week or even more time from the rig. Thus, having accurate information about returned fluid and recording mud loss rate can be great help to prevent drilling problems from taking place.
Drilling fluid loss is affected by different factor that make modelling of mud loss suffered from analytical point of view. Thus, employing artificial neural networks which its capability in simulation of complicated phenomena is proven looks very effective. In this research, using drilling daily report of some wells in Maroun oilfield (South-west of Iran), attempts are directed to predict lost circulation in different areas of this field. Network results in prediction of drilling fluid loss show good compatibility with real data were recorded in drilling daily reports.
Cement Packer: A Key to Accessing Marginal Reserves in Brown Fields
Authors: Olatunde F. , Adegboye P. S. , Idedevbo K. 
Published: February 2011

Abstract
Most brown fields are now experiencing rapid decline in oil rate; also, the cost of drilling has escalated over the years, thus posing a challenge to drilling opportunities in brown fields. Over the years new field discoveries have been on the decreasing trend and this has prompted operators to start looking for ways to access reserves that were originally considered marginal and hence bypassed during the early stages of field development. As these bypassed reserves were not considered significant, most of the wells were completed leaving the "sub economic" potential above the packer. Accessing them now would typically require pulling the tubing through a major rig workover (MRWO). This is very expensive and as such, MRWO operations are challenged by the economics of the reserves in place.
The thru-tubing cement packer is an innovative and cost effective technique of accessing behind pipe opportunities in existing wells. So while not a new technology, it is new to Chevron Nigeria. The reason why it has not been implemented sooner is likely because until recently, we have been fortunate enough to have plenty of (MRWO) opportunities with solid economics. The combination of extremely high rig rates coupled with a significant drop in the price of crude oil has resulted in a need to look for other, less costly means to access additional reserves.
The cement packer operation achieves zonal isolation through rigless workover cementing. The use of Slickline perforation as opposed to the conventional E line further drives down the rigless operation cost thus improving the economics of marginal reserves. This low cost method of developing reserves is key in ensuring that operators extract as much value as they can from their assets.
This paper reviews two case studies in the Southern Offshore Area operations of Chevron Nigeria where the cement packer technology was deployed successfully. The cost savings realized is presented and further application of this technology to other areas is also discussed.