bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intelligent Appraisal Program for a Multi-Prospect Development
Authors: Delfiner Pierre 
Published: October 2011

Abstract
While many companies are hunting for elephants, exploration results in deep offshore plays over the past years show the increasing trend away from giant field discoveries towards smaller fields in the 50-100 million bbl range, which tend to be geographically dispersed. These resources need to accumulate to a critical mass to justify an economically viable development. How likely is this to happen? Which objects must be included in the resource base? Which drilling program should be planned to reach an early decision? Given the huge costs involved, answers cannot rely on the subjective choice of a few deterministic scenarios.
A novel methodology is proposed to evaluate the potential for a hub in a deepwater multi-prospect development. The approach relies on a probabilistic model of the risks and uncertainties of the resource base, illustrated by a real case study including five discoveries and four prospects, 10-30 km apart. Each object must pass a minimum resource threshold to justify its connection to the hub. Then a global threshold is applied to the complete development.
The performance of a proposed appraisal program is quantified by statistical indicators obtained by simulating a large number of drilling outcomes which are stored in a scenario database. Three indicators capturing the three elements of Decision Analysis (states of nature, decisions, payoffs) prove useful. These are respectively: the distribution of the resource potential in the ground; the probability of a development decision based on the cumulative discovered exceeding the threshold; and the distribution of developed resources. The last two elements define the traditional economic decision tree.
Intelligence is introduced in the appraisal program by reassessing the situation after each well and evaluating the probability of meeting the threshold with the remaining wells. If it is low (10% or less) appraisal is stopped, or its scope reduced. Early quitting minimizes well count in the dry branch of the economic decision tree, which has a great impact on risked economics. Optimizing the drilling order may also reduce the number of wells needed to reach a decision. Thus an efficient appraisal program with firm and contingent wells can be defined.
The Sanding Mechanisms of Water Injectors and their Quantification in Terms of Sand Production: Example of the Buzzard Field (UKCS)
Authors: Santarelli F. J. , Sanfilippo F. , Embry J. M. , White M. , Turnbull J. 
Published: October 2011

Abstract
The sanding of water injectors is considered a serious issue, as it can trigger important injectivity reductions and may sometimes and may sometimes lead to the collapse of wells. Cross-flow during shut-in and the water hammer pressure wave generated by the well closure are recognized as the main contributing factors to sanding. However the paper will show that the precise mechanisms of sanding on water injectors have not been fully described yet.
The unexpected and early collapse of an injector on the Buzzard field - i.e. the largest current oil producer in the UK - required the evaluation of the sanding risk for the other 12 injection wells, as the loss of another one would have been critical in terms of field management. The complete records of all the wells, including their injection histories were therefore recovered and analysed.
The analysis revealed that four sanding mechanisms were at play:
Natural cross-flow between layers at pressure equilibrium, Forced cross-flow between layers not at pressure equilibrium, Swabbing from the water-hammer pressure-wave, Surface-flow between wells.
The occurrence of each mechanism for each well was checked and quantified through field data analysis, modeling and direct downhole measurements (injection logs and video). In particular, the amount of sand produced by each mechanism was quantified. The analysis showed that the forced cross-flow on the collapsed well had produced sand quantities orders of magnitude larger than what was experienced by the other wells and the risk of losing another well was therefore judged minimum. In addition measures were taken to limit the impact of all four mechanisms on the existing wells and a methodology was devised to avoid the conditions of the collapsed well on future wells.
The paper presents a complete methodology for quantifying the risk associated with the sanding of injectors. In addition the measures taken to limit the impact of the various sanding mechanisms can easily be implemented without significant costs to all wells injecting in weak reservoirs.
A Unique Plug for a Restricted Wellbore
Authors: Blevins Joy , Frazier Garrett 
Published: October 2011

Abstract
The completion of most cased-hole horizontal shale wells requires multi-stage stimulations, which calls for some form of plug isolation between the stages. The plugs are normally composite flow-thru plugs that are pumped downhole on electric wire to the required measured depth.
This case history describes a project where the industry's standard-sized composite plugs with a 3.85-3.92 in. outer diameter (OD) would not pass through the curved section of the horizontal wellbore with an internal diameter (ID) of 4.276 in. Small doglegs in the curved section of the wellbore presented geometrical and completion challenges. Three attempts to push the plugs through this section of the wellbore failed, resulting in the plugs getting stuck. The project faced a challenge: Could a plug be built in a timely manner that would pass through the curve restrictions, set in the production casing, withstand stimulation pressure, and still be drillable?
The project challenge was successfully answered. A new composite plug was designed that met all of the wellbore requirements and allowed a successful completion of the wellbore. The 3.25 in. OD flow-thru composite plug was set in a 4.276 in. inner diameter (ID) production casing. Altogether, six plugs were pumped down and set in the wellbore of the West Texas, University Land 39 #29-1H well. The plug met all of the required performance expectations during all stages of the completion.
This plug's application goes beyond the standard horizontal wellbore with multi-stage stimulation requirements. The uniqueness of this plug is its ability to be modified for a variety of applications where reduced internal diameters in production casing create completion challenges below the restriction.
The details of the wellbore deviations and the final plug design solution are included in this paper.
Mitigation of Torsional Stick-Slip Vibrations in Oil Well Drilling through PDC Bit Design: Putting Theories to the Test
Authors: Jain Jayesh R. , Ledgerwood L. W. , Hoffmann Olivier J. , Schwefe Thorsten , Fuselier Danielle M. 
Published: October 2011

Abstract
Stick-slip vibrations of drillstrings have been studied by researchers for several decades. The subject is gaining renewed interest as operating parameters for PDC bits have shifted to the stick-slip regime of higher bit weight and lower rotary speed for enhanced drilling performance. In Ledgerwood et al. (2010), stick-slip was identified as a primary cause of bit damage. The main objective of the current investigation is to answer the longstanding question: Do bit designs influence stick-slip behavior of the drilling system? Five prevailing industry perceptions reported in the literature are that anti-whirl bits, reduced exposure bits, and bits with bit-rock interaction number "β" &gt; 1 are less prone to stick-slip, while highly aggressive bits and worn bits are more prone to stick-slip. Although the phenomenological basis of these theories has been provided, validation in most cases is based on anecdotal evidence from the field. Data with diagnosis based on downhole measurements in a controlled environment are scarce. Consequently, conflicting opinions continue to exist about whether any of these theories work in reality.
To assess their validity, the five leading theories were reviewed and pairs of PDC bits were designed and manufactured. Each pair consisted of a bit with a standard design and a bit that embodied one of the theories. The bits were first tested in the laboratory to characterize their response. Full-scale wells were then drilled under controlled conditions using a research drill rig in Oklahoma. In these wells, only the operating parameters were varied while BHA, formation, and other variables were unchanged for a given bit pair. The downhole vibrations were measured with a new in-bit device and an industry-proven MWD vibration monitoring service.
The most important conclusion emerging from this study is that PDC bit design has a significant effect on stick-slip vibrations. While some of the theories held true, evidence from this study did not support others. The details of test results are provided and various aspects of bit design are discussed in an attempt to enhance the understanding of stick-slip mitigation.
Impacts of the Porosity-Permeability Transform Throughout the Reservoir Modeling Workflow
Authors: Roadifer R. D. , Scheihing M. H. 
Published: October 2011

Abstract
Reservoir simulation history matching typically involves a process whereby reservoir rock, fluid properties and well-bore conditions are modified in some systematic way to match observed production rates and pressures. The degree to which initial reservoir and well parameters need to be modified can often be attributed to the amount and quality of hard data available and the integration of that data into the geocellular model. All too often, however, reservoir engineers find that they must modify reservoir parameters significantly in order to obtain a history match.
Historically, porosity cut-offs have often been applied to fine-grid geocellular models during upscaling to obtain the reservoir simulation-scale model. Porosity cut-offs have typically been selected by inspection of the core-derived porosity-permeability (P&P) relationship(s) and selecting the porosity that falls below an a priori specified permeability cut-off. During subsequent history matching, a disconnection between upscaled geocellular model and history-matched permeabilities becomes apparent. Permeability modifiers of two or more often need be applied across the reservoir to match reservoir performance. Discrepancies between well-log-derived porosities and core-measured porosities due to the scale (averaging) effects of the logs have been long recognized and can be accounted for in various ways (Klein et al., 2006). However, the discrepancy in permeabilities between the initial upscaled geocellular and history-matched reservoir simulation models appears to be different. In 2007, Delfiner provided a very simple, yet elegant, explanation for this discrepancy and one potential solution to the problem.
Simple examples are utilized to show how errors in the porosity-permeability transform can propagate throughout the model building and history matching process, resulting in a potentially significant underestimation of OOIP and recovery. In particular, the potential impacts of the porosity-permeability transform on net pay definition, liquid permeability, initial water saturation, relative permeability, fractional flow, production rate and ultimate recovery are discussed along with how the implementation of the suggested solution by Delfiner (2007), together with other approaches, can help mitigate these errors.
Can You Protect Your Motor Without Sacrificing Performance?
Authors: Guidroz Blair , Barton Steve , Hussain Mohammed 
Published: October 2011

Abstract
Achieving balance between performance and longevity of drilling motors is a constant struggle. Operating above recommended parameters delivers higher Rates of Penetration (ROP) but can be too aggressive, causing accelerated component wear and potentially, premature failure. Conservative operation decreases the component wear but can be detrimental to drilling performance. A novel approach to controlling motor performance allows operators to operate at specified limits while preventing load spikes that damage motors.
Stalling is a problem that affects bearing loading, occasionally leading to driveshaft torsional failure, but more commonly causing power section damage in the stator, reported as chunking. Chunking occurs when the elastomer in the stator has reached the fatigue limit and small pieces break free of the profile. The output performance of the power section decreases as the effective area of power section is reduced and it becomes less efficient. Reduction in output performance decreases ROP and operators will typically push motors harder to maintain ROP, further accelerating the time to failure.
An innovative internal device prevents premature failure by limiting the amount of differential pressure applied across the motor. Excess pressure is relieved by porting fluid through the center of the rotor, bypassing the power section inlet. Rotational speed decreases as flow into the power section is decreased. The pre-determined relief point is adjustable to optimize motor performance for specific applications. Preventing motor damage delivers longer drilling hours with reduced unplanned trips.
Field testing of the device has resulted in a significant reduction in motor component damage. ROP improved and was consistent through the drilling program with the controlled and steady operation of the device. Cost per foot decreased as longer intervals were drilled per motor. This device gives operators a new tool to optimize motor performance.
Optimization of Unconventional Gas Developments by Bayesian Logic and Genetic Algorithm
Authors: Willigers B. J. 
Published: October 2011

Abstract
Many unconventional gas developments provide only marginal economic returns. Realizing a commercial success with such projects depends on the identification of an efficient development program. Significant project value can be unlocked by, for example, optimizing the drilling program and the gas export infrastructure development. The optimization of an unconventional green-field gas development is subject to a multitude of objectives, constraints, and tradeoffs. Decision making is further complicated by multiple sources of uncertainty.
Tools like decision trees and Monte Carlo simulations can help assess exploration and early-stage development projects. However, these methods are impractical for large numbers of options and uncertainties, which are associated with many mid-stage development projects. Many decision situations are in fact complex optimization problems and practical techniques are required to enhance decision making policies.
The genetic algorithm is a powerful method to optimize complex non-linear systems for a given set of constraints. However, many real-life situations involve sequential decision making, which is likely to cause preferences to change when uncertainties are progressively resolved. The value of managerial flexibility associated with such projects cannot be quantified in a single execution of a genetic algorithm. However by a series of iterative calculations of a genetic algorithm that is conditioned with Bayesian logic the optimization procedure can be significantly improved.
Creating Portfolio Insight by a Pratical Multi-Method Optimisation Approach
Authors: Willigers B. J. , Weis F. , Majou F. 
Published: October 2011

Abstract
Effective portfolio management requires a comprehensive understanding of the tradeoffs between different portfolio choices. Given a set of constraints, portfolio optimisation techniques based on linear programming and genetic algorithms can be applied to identify an optimal portfolio. However, this optimal portfolio might not be the preferred portfolio. Decision makers have to understand the tradeoffs between generally conflicting objectives and constraints before one portfolio can be identified as the preferred option. Such assessment of the overall search space is not made using linear programming and genetic algorithms when used to identify a single best solution and many portfolio options will have been eliminated before an understanding of these alternatives has been developed.
Markowitz's mean-variance approach and the traditional "rank and cut" approach are typically used to establish a relationship between a portfolio's value and its variance or associated development cost. Although these methods enable decision makers to compare and contrast different options, the optimisation is limited to the portfolio value measure and a single other metric. This latter limitation is overcome by the more recently developed portfolio filtering approach. This method is practical and transparent and allows for a quick development of strategic portfolio alternatives while considering a large number of portfolio attributes. Its main drawback is that the analysed set of portfolios generally represents a subset of the total search space. Hence, as the number of feasible portfolio options increases, so does the chance that the optimal portfolio is not present in the population of sampled portfolios.
This paper presents a portfolio optimisation approach that combines linear programming, genetic algorithms and portfolio filtering. An analysis of a realistic upstream portfolio illustrates and validates the optimisation process by demonstrating how limitations of individual methods can be mitigated by combining them.
Smart Nanostructured Materials Deliver High Reliability Completion Tools for Gas Shale Fracturing
Authors: Xu Zhiyue , Agrawal Gaurav , Salinas Bobby J. 
Published: October 2011

Abstract
Hydraulic fracturing is considered necessary for economically efficient gas production in low natural permeability shale resources. Flow control devices such as setting balls or plugs are used for sleeve actuation or stimulation diversion during fracturing. After fracturing, these in-flowpath devices must be disposed of by methods such as drilling out or flowing back to open the flowpath for production.
Traditional low-strength ball or plug materials are prone to shape changes. Severe deformations present flowback issues and potentially require costly intervention. Additionally, it is believed that smaller balls—particularly from the well's toe section—do not always flow back to surface, leading to potential restrictions in the tubing. Operations value the concept of fully degradable ball material. Traditional degradable material, though, lacks the high material strength necessary for high-pressure fracturing and has unreliable degradation rates.
This paper will present a newly-developed nanostructured material technology called controlled electrolytic metallics (CEM), which makes high-strength and lightweight metallic composites possible. This new class of composites is completely corrodible in typical downhole environments at a predictable and controllable rate. CEM balls have passed multiple impact tests at speeds exceeding 100 mph. In 3% potassium chloride (KCl) at 200°F, these balls can completely corrode away in-situ in days. Material composition and associated processing can be changed to increase material strength by several times and the corrosion rate by several hundred times.
CEM balls performed as designed in Bakken shale field testing. Material can be designed to rapidly corrode in 5 to 15% hydrogen chloride (HCl), giving a foolproof technology with operational flexibility. The fundamentals of innovative material design and processes, along with lab test and field application data of this material will be presented. CEM-based completion tools eliminate drilling out, guarantee an open flow path for each fractured zone, and enhance well productivity. This truly interventionless technology is also being researched for high-pressure, high-temperature (HP/HT) applications.
Measurement and Modeling of Excess Oil Flow During Tertiary Gas Flood
Authors: Dehghanpour Hassan , DiCarlo David 
Published: October 2011

Abstract
Relative permeabilities for three-phase flow are commonly predicted from two-phase flow measurements using empirical models. These models are usually tested against available steady state data. However, the oil flow is unsteady state during various production stages such as gas injection after water flood. Accurate measurement of oil permeability (kro) during unsteady tertiary gas flood is necessary to study macroscopic oil displacement rate under micro scale events including double drainage, coalescence and reconnection, bulk flow and film drainage.
We conduct several unsteady state three-phase gravity drainage experiments with different initial conditions. We calculate kro by using the saturation data measured by a CT scanner. We find that the kro data measured during gas flooding to recover waterflood residual oil, are unexpectedly high and weakly depend on oil saturation. In contrast to steady state data, the measured kro data here are higher than the two-phase gas/oil limit. We explain how Stone I and saturation-weighted interpolation should be used to predict the permeability of mobilized oil during transient tertiary gasflood.
Catalytic Effects of Nano-Size Metal Ions in Breaking Asphaltene Molecules During Thermal Recovery of Heavy-Oil
Authors: Greff J. H. , Babadagli T. 
Published: October 2011

Abstract
Heavy-oil or bitumen recovery requires effective recovery of many different components of hydrocarbons for an efficient process. Production of asphaltenic components and minimizing their precipitation, which may affect the ultimate recovery and rate, is of particular interest. Conventional thermal and solvent techniques are limited in breaking asphaltene components and new types of catalysts are needed for efficient recovery of heavy-oil.
The presence of nano-size metal particles catalyzes the breaking of carbon-sulfur bonds within asphaltenes. This results in a reduction of asphaltene content, with an increase in saturates and aromatic content. The end effect of this process is a significant reduction in the viscosity of heavy oil and bitumen. Having a strong hydrogen donor present dramatically increases the amount of viscosity reduction, while not having any hydrogen donor present completely inhibits the reaction. The proper metals and corresponding concentrations need to be investigated before conducting displacement experiments in porous media.
In this paper, we investigated the effects of microwave radiation, using a standard 2.45 GHz emitter, on viscosity reduction. Different nano-sized metal particles (Fe, Fe(III) Oxide, and Cu) were used as catalysts in concentrations ranging 0.1% weight to 1% weight. Heavy oil samples were heated to and maintained at a temperature of 200°C using inductive microwave heating for a period of 5 hours. Viscosity and mass data were obtained before and after each experiment, with viscosity being measured at 55 °C, 75°C, and 95°C. Since the heavy oil samples which contained no added hydrogen donors experienced a significant vaporization of components, they must be participating in a reaction independent of the aquathermolysis reaction.