bluuebunny/crossref_metadata_2025 huggingface dataset:
Control loop performance assessment and improvement of an industrial hydrotreating unit and its economical benefits
Authors: Longhi L.G.S. , Reginato A.S. , Teixeira H.C.G. , Cortez C.A.C. , Lusa L.P. , Gonzalez S.S. , Fleck T.D.
Published: October 2012

This paper describes the CLPA (Control Loop Performance Assessment) and its improvement applied to an industrial hydrotreating unit (HDT) located at Alberto Pasqualini Refinery (REFAP S.A.). It is presented a review on regulatory control performance evaluation methods and the developed tool is described. The basic steps of the work methodology are also presented, with focus on the planned and implanted actions to improve the unit dynamical performance. Finishing the paper, the main results for a long-term industrial application are presented, including the unusual economic gains evaluation.
Briefing: Modelling drainage across London Underground: a case study
Authors: Snell Rob , Morgan David , Valente Mark
Published: October 2012

Historically, maintenance of the surface water track drainage system serving the London Underground (LU) was limited to discrete like-for-like repairs in response to deteriorating asset condition. The use of modelling software to gain an accurate understanding of the hydraulic performance of the system has been limited by incomplete and often inaccurate data, due to the fact that the railway was constructed in parts over many decades and contains numerous peculiarities. This paper uses the LU track drainage modelling project (encompassing the Central, Circle, District, Hammersmith and City and Metropolitan lines) as a case study to demonstrate how seemingly unmanageable quantities of disparate data can be brought together to produce hydraulic models that provide significant benefit in informing maintenance activities and asset renewal programmes.
Mapping behavioral landscapes for animal movement: a finite mixture modeling approach
Authors: Tracey Jeff A. , Zhu Jun , Boydston Erin , Lyren Lisa , Fisher Robert N. , Crooks Kevin R.
Published: October 2012

Because of its role in many ecological processes, movement of animals in response to landscape features is an important subject in ecology and conservation biology. In this paper, we develop models of animal movement in relation to objects or fields in a landscape. We took a finite mixture modeling approach in which the component densities are conceptually related to different choices for movement in response to a landscape feature, and the mixing proportions are related to the probability of selecting each response as a function of one or more covariates. We combined particle swarm optimization and an expectation‐maximization (EM) algorithm to obtain maximum‐likelihood estimates of the model parameters. We used this approach to analyze data for movement of three bobcats in relation to urban areas in southern California, USA. A behavioral interpretation of the models revealed similarities and differences in bobcat movement response to urbanization. All three bobcats avoided urbanization by moving either parallel to urban boundaries or toward less urban areas as the proportion of urban land cover in the surrounding area increased. However, one bobcat, a male with a dispersal‐like large‐scale movement pattern, avoided urbanization at lower densities and responded strictly by moving parallel to the urban edge. The other two bobcats, which were both residents and occupied similar geographic areas, avoided urban areas using a combination of movements parallel to the urban edge and movement toward areas of less urbanization. However, the resident female appeared to exhibit greater repulsion at lower levels of urbanization than the resident male, consistent with empirical observations of bobcats in southern California. Using the parameterized finite mixture models, we mapped behavioral states to geographic space, creating a representation of a behavioral landscape. This approach can provide guidance for conservation planning based on analysis of animal movement data using statistical models, thereby linking connectivity evaluations to empirical data.
Dynamic Assessment: A History of Fundamental Ideas
Authors: Haywood H. Carl
Published: October 2012

The development of dynamic assessment rests on the prior and successive appearance of a small number of fundamental ideas that are seen as essential and compelling. These include the concept of individual differences as a vital aspect of psychology and human development; the importance of assessing the very processes of systematic thinking, learning, and problem solving (rather than merely the products of these processes); the concepts of learning potential, educability, and the zone of proximal development; and the mediational nature of the intervention in dynamic assessment. These essential ideas are discussed in historical context as a cumulative enterprise. Prominent unsolved problems remain, including precise procedures for process assessment, bridging the gap between assessment of potential and subsequent classroom instruction, the relation of dynamic to static assessment, and the accompanying problems of reliability and validity.
“Adolescent” South Africa (18 Years Since Democratization): Challenges for Universities to Optimize Wellness as a Prerequisite for Cognitive Development and Learning in a Diverse Society
Authors: Botha Ludolph , Cilliers Charl
Published: October 2012

South Africa’s development since 1994 has been of interest to many people across the world as the diverse nature of our society, including the growing diversity of student populations at our universities, demands very special interventions and initiatives to help create a healthier society. Research at Stellenbosch University demonstrates a positive relationship between wellness (which includes its intellectual, social, emotional, physical, spiritual and occupational dimensions) and student success. The main focus of this article is on how a university can develop systemic-holistic strategies to enhance wellness. High levels of wellness in students contribute toward the formation of harmonious and healthy communities on campus, where diversity is regarded as an asset. Furthermore, these “well” students will one day enter the world of work as well-rounded professionals and global citizens who do not hesitate to continue contributing toward the creation of a better society. Academic (or cognitive) success is of vital importance; however, student success in our very diverse context requires a much wider spectrum of characteristics or graduate outcomes for them to flourish and contribute optimally.
Oil and Gas Reserves and Resources Reporting - The Market Rules
Authors: Scott Michael T.
Published: October 2012

Companies listed on the big six markets (Australia (ASX), Canada (TSX), USA (NYSE), UK (LSE Main Market and AIM), Singapore (SGX Main Market and Catalist) and Hong Kong (HKEx)) all have requirements of some form when it comes to reporting oil and gas reserves and resources. The requirements may be specified by the market rules, the market financial regulators, extra-territorial legislation, accounting standards or standards published by technical societies and are usually supported by Government Legislation. The requirements vary considerably and place very different technical and administration demands on oil and gas companies.

This paper provides an engineer's broad brush overview of the various requirements, provides a comparison to SPE PRMS, makes a qualitative comment on the strength and weakness of the exchange rules and ultimately provides some best practice considerations.

This paper can benefit all listed companies who need to know the rules they are required to comply with, can benefit all unlisted companies by giving them an insight into the types of reporting that investors may typically demand and can benefit petroleum professionals by enabling them to know what they must provide.
Improved Waterflooding and EOR for Lower Permeability Fields
Authors: Fletcher Alistair
Published: October 2012

Low permeability reservoirs contain a large volume of the world's oil resource. Often these fields are characterised by low waterflood injectivity, poor sweep and low productivity. A substantial number of these fields are initially, or during production become, fractured. Improved oil recovery and EOR for these fields is an attractive goal, although many conventional EOR applications present major challenges.

We present results on how wettability alteration, together with physical and chemical modifications of the waterflood, can improve oil recovery. From high precision adsorption experiments, together with wettability measurements on model systems, we present conclusions on the inter-relationship of adsorption behaviour and wettability of reservoirs.

Laboratory measurements are presented confirming how:

Wettability can be modified through changes in salinity, hardness and temperature. In waterflooding there is a direct, measurable relationship between wettability (contact angle) and adsorption at the solid / liquid and liquid / liquid interfaces. These inter-relationships can be expressed in basic thermodynamic concepts. Adsorption at solid / liquid interfaces can be directly related to the existence and nature of thin aqueous films in water wet and mixed wet reservoirs. Dynamic effects resulting from brines of different chemical and physical properties can be highly important in terms of displacement efficiency during waterflooding.

We demonstrate the significance of these results for waterflooding and EOR in lower permeability fields. Approaches such as wettability alteration, low salinity (including brine compositional modification) waterflooding, and variation of injection brine temperature all show potential. This is in contrast to more traditional chemical and immiscible gas injection, which are often technically difficult in these fields. We further conclude that these approaches can be beneficially applied fields with substantial fracturing and faulting.
Casing Thermal Stress and Wellhead Growth Behavior Analysis
Authors: Liang Q. Jim
Published: October 2012

In high-temperature wells or in high-temperature gas injection wells, casing thermal stress is an important issue that should be considered in well design. Stresses introduced by well temperature changes could be severe and critical, resulting in catastrophic well integrity failure and surface equipment damage if not properly identified.

The problem can be more severe when a high-temperature well is constructed in a cold environment; the temperature increase from the equipment's as-installed condition to operation conditions would be even higher. A deepwater well or arctic area well installed in winter needs special consideration for thermal stress.

A field example in this paper demonstrates a near miss catastrophic well integrity failure. The incident will be analyzed by using a multistring well thermal growth model to calculate casing thermal stress and wellhead growth.

Casing thermal growth and stress is sensitive to the length of free moving casing sections. In this paper casing thermal behavior and wellhead movement will be discussed by analyzing different casing string top of cement (TOC) depths. This paper demonstrates how to minimize thermal force and reduce wellhead thermal growth by optimizing the casing cement level. At given conditions, adjusting surface tension during casing installation can also help counterbalance thermal force. It is important to understand the thermal forces and behavior of all casing strings in a well during its operational life.
Using Dynamic Simulations to Predict and Optimize Cleanup Operation of Horizontal Gas Wells
Authors: Azmi Khairul , Christopher Ogbonna , Jadid Maharon , Yusuf Rahel
Published: October 2012

Cleanup operations of gas wells are conducted when the well is kicked off and tested the first time. During cleanup, the drilling and completion fluids come out of the well along with the produced gas and associated liquids. The phenomena is transient in nature and minimum gas rate and time required for cleanup are key questions to be answered before embarking on the cleanup and subsequent well test operation. The knowledge of minimum gas rate and time required for cleanup can assist the engineer in deciding the well test package and make best use of the available time.

In the current study, transient simulations of cleanup and MRT of three horizontal gas wells are conducted using a commercial multiphase transient simulator. Before the actual cleanup operations, simulations were conducted to estimate the cleanup time and to arrive at optimum beanup procedure to achieve best cleanup for a maximum gas rate constraint of 60 MMscf/D which is dictated by the size of well test package. After the cleanup and MRT operations were conducted, the operational data was used to tune the model. It was observed that the predicted temporal variations of gas rate and gauge temperature and pressure from the tuned model were in very good agreement with the measured values. The tuned model was then used to ascertain the degree of cleanup achieved from the actual cleanup and MRT operations and the model predictions showed that except the last 60 metres from the toe, the wells were completely cleaned of completion fluid. The poor cleanup in the last 60 metres was possibly because of 60 MMscf/D gas rate limit imposed by the size of well test package or resulting from poor contribution from the near-toe area.

The study brings forth the significance of dynamic simulations in predicting and history matching gas well clean up operations and how dynamic simulations can provide an insight into the pressure and flow transients during cleanup. The knowledge gained from dynamic simulations can assist the engineer in deciding the well test package for gas wells to be cleaned up and in quantifying the cleanup achieved from an already conducted cleanup operation.
De-Risking A Horizontal Well Through Application of New Deep Directional Resistivity Tool to Equate Seismic Data with Borehole Data
Authors: Jenkins Steve , Sims Andy , Oldham Eleanor , Silcock Simone , Seaton Matt , Spotkaeff Matthew , Viandante Mauro , Mirto Ettore , Nath Aditi , Blasdale Tim , Lepp Becky , Chow Stephanie
Published: October 2012

The Nautical Petroleum appraisal well 9/02b-5Z, located in the North Sea, was recently drilled using a new deep directional resistivity tool which enabled the simultaneous real-time mapping of the upper and lower boundaries of a 100+-ft reservoir, over the length of the 2,000-ft horizontal well. This device was of great benefit in both validating the accuracy of the seismic interpretation and tying the borehole acquisition data to the seismic data.

One of the greatest challenges in geosteering is that horizontal wells are planned using a seismic visualization of the reservoir but are drilled using a borehole visualization of the reservoir. There is a large disparity in the resolutions of these two systems. Often, only a vague structural outline can be trusted from the seismic data, necessitating the geosteering process, while even the deepest reading bed boundary mapping tool currently available can only visualize one boundary in anything other than a relatively thin reservoir for referencing back to the seismic data.

The new generation deep directional resistivity tool, currently in field test, has a greatly enhanced depth of investigation coupled with the ability to detect multiple boundaries in any direction, allowing for the marriage in real time of the seismic and the borehole data and leading to more effective and productive drilling of horizontal wells.

This paper will describe the Nautical Petroleum 9/02b-5Z case study and will detail how this data was used both in the post-well evaluation of the overall reservoir structure and in the real-time application of the data in significantly reducing the risk associated with the placement of the borehole.
High-Strength, Low-Density Cement Pumped On-the-Fly using Volumetric Mixing Achieves Cement to Surface in Heavy Loss Coal Seam Gas Field
Authors: Tan Brendon , Lang Matthew , Harshad Devin
Published: October 2012

One of the greatest challenges with respect to coal seam gas (CSG) wells in Queensland, Australia is the many loss zones encountered during drilling and cementing operations. Typical directional wells in the area are up to 2000 m measured depth (MD) and 1200 m true vertical depth (TVD). In some instances production enhancement by fracture stimulation is required and therefore high-strength cement is necessary while maintaining the lowest possible pressure on the formation and natural fractures.

A trial was setup on a directional well pad where various methods of returning cement to surface were attempted. All three wells had similar well design, expected losses, and drilling times. The first well was unsuccessful and no cement was returned back inside the previous surface casing shoe. With the addition of a reactive spacer and more excess volume, cement inside the previous casing shoe was achieved on the second well. Both wells used standard 12-lbm/gal slurries. The third and final well on the pad required a step-change in the cement job design to achieve cement to surface.

The most successful cementing job was achieved on the third well by redesigning the slurry to a lower density of 11 lbm/gal, without compromising set times, thixotropic properties, and high compressive strength. To improve equivalent circulating densities (ECD), the new slurry was designed with lower rheology. The slurry's low solids-to-water ratio (SWR) and large slurry volume, which precluded batch mixing, required the job to be mixed and pumped on-the-fly using an automated volumetric mixing system rather than using density mixing.

This paper discusses the job preparation and technical details involving how the 11-lbm/gal cement slurry achieved a successful production casing cement job with returns to surface. With similar successes demonstrated on subsequent wells, this case history set a new standard in the field.
Evaluate Field Development Option, Production Optimization Scenarios and Analysis of Surface Network Upgrading Phases of Abu-Attifel
Authors: Ali Algdamsi Hossein , Ali Misherghi Nasser , Ganib Hussein , Zeglam Adel , Jallul Hassan
Published: October 2012

Most of the mature field surface networks suffer from the back pressure applied on the wellheads. An extra pressure in front of the influent fluids should be overcome to handle the fluids to the final destination gathering point. This paper presents de-bottlenecking of Abu Attifel surface network and the solution proposed during production optimization phases. To capture the performance of Abu Attifel field wells, sixty wells single branch model were built using nodal analysis technique. All thes wells were connected together to present the total field network. The network model consists of two different pressure systems. Low pressure system, which are 7 wells connected directly to the second stage separator, the remaining 53 wells are connected to the first stage separator operating at higher pressure. The network model was calibrated and matched globally through tuning of pipeline roughness and compared with the pressure measuring points at the gathering manifolds. As a result, reasonable match was obtained with 2% difference between actual and model calculated flow rates. All gathering points and well headers were matched with the available pressure and flow rate measurements. This validated network provided a valuable tool to evaluate, optimize and enable enhancement of the oil production. It defined several solutions to increase oil production such as converting some wells to the lower pressure separator, and the visibility to install two multiphase booster pumps in the flow line.
Demonstrating Adequate Management of Risks: The Move from Quantitative to Qualitative Risk Assessments
Authors: Bower-White Graham
Published: October 2012

This paper will demonstrate that the use of quantitative risk analysis (QRA) has limitations and does not, in isolation, demonstrate adequate management of risks. The only way to demonstrate that risks are being appropriately managed is to identify all hazards; understand the level of risk; identify all prevention, control and mitigation barriers; and then demonstrate that those barriers are adequate and effective in managing that risk to a level that is as low as reasonably practicable.

This paper is applicable to all process industries and, in particular, those industries operating under the jurisdiction of NOPSEMA in Australia. Under the OPGGS Act we have a legal obligation to demonstrate that we are managing risk to levels that are demonstrably ALARP.

In summary this paper will show that QRA has its place in demonstrating adequate management of risks; however, it should not be used in isolation. Having a QRA conducted can sometimes provide a false sense of security that risk is being managed. The UKOOA Risk-based Decision Making Framework is a useful tool in demonstrating the small part that QRA plays in managing risk. The answer to managing risk effectively lies in demonstrating that adequate and effective controls are in place. Not only do we need to identify the controls that are required to manage risk effectively, we also need to demonstrate that those controls are actually in place, are performing as they should and that competent people have confirmed that this is the case.

In the process industry, post-Macondo & Montara, it is essential that operators move away from just demonstrating that they understand the level of risk that personnel and the environment are exposed to. We all need to move towards demonstrating that we have adequate and effective barriers and controls in place to manage that risk effectively.
Permeability Increase in Bowen Basin Coal as a Result of Matrix Shrinkage during Primary Depletion
Authors: Scott M. , Mazumder S. , Jiang Jessica
Published: October 2012

Matrix shrinkage in coal-seam gas reservoirs as a result of production, and the resultant impact on absolute permeability, is a current area of intense interest. A number of publications have documented the existence of this phenomenon. The exponential growth behaviour of coal seam permeability with reservoir pressure depletion has been observed previously at the Fairway wells in the San Juan basin. More recently, an exponential trend has also been confirmed for a group of 10 wells in a region northeast of Fairway. An increase in the absolute permeability of coal seam is a result of matrix shrinkage caused by gas desorption, which becomes a dominant factor on cleat permeability over the effective horizontal stress change during production. Bottom hole pressure recovery during shut-in periods can provide valuable data concerning the impact of coal seam gas production on reservoir permeability. Arrow Energy's historical production data, from the MGP field in the Bowen Basin, contains over 60 instances of data on pressure recovery during shut-in. These Time lapse Build-up periods have been analysed using the pseudo-pressure method (Kamal and Six, 1991) in an effort to gain an understanding of the extent and effect of this phenomenon within the company's existing assets. The method is based on a pseudo pressure function that uses the adsorption isotherm and the relative permeability relations of the reservoir. The infinite acting radial flow regime was identified and the gradient was recorded on a semi log plot of the pseudo pressure versus dimensionless time. Results from these tests show multi fold increase in absolute permeability as a function of the estimated reservoir pressure.
Agitation Tools Enables Significant Reduction in Mechanical Specific Energy
Authors: Azike-Akubue Vivien , Barton Steve , Gee Ryan , Burnett Timm
Published: October 2012

Mechanical Specific Energy (MSE) is a term used by the oilfield drilling industry to describe several formulae quantifying the energy input within a drilling system. MSE mainly describes the Mechanical (WOB and Torque), for a given unit (Length, area or mass), and the energy required to do the work (i.e. force, time, distance).

Although several different formulae have been developed in an attempt to quantify this value, the accepted industry standard is as below:

E s = W A X + 120 π N T A X R

Where:

Es = Specific Energy (psi) N = Rotary Speed (rpm)

W = Weight on Bit (Ibf) T = Drilling Torque (ft-lbf)

Ax = Borehole x-sectional area (inA2) R = Rate of Penetration (ft/hr)

When using surface parameters such as RPM and Weight, the drill string and BHA frictional losses are the primary source of energy loss in typical drilling systems. As such, introduction of solutions to reducing these frictional losses would have a significant impact on reducing the MSE of the system. This would lead to improved drilling efficiency, thus lower drilling time and reduced costs.

The effect of having an axial oscillation tool (AOT) in the drill string has been previously demonstrated to be effective, particularly in applications where sliding with steerable motors has been problematic. Axial oscillation in the drill string is generated through a series of pressure pulses coming from one part of the AOT. The pressure pulses act on the pump open area of a shock tool, generating the axial motion required to reduce friction, improve the weight transfer to the bit, reduce reactive (and thus overall) downhole torque. The hydraulic vibration also enhances the performance through reducing friction.

The AOT's influence on reducing friction in a constant axial oscillation helps reduce the total friction significantly. Friction reduction enables the entire suite of drilling parameters to be optimized through proper weight transfer, which in return, reduces the chance of buckling, reduced torque, increases ROP, and increase bit life; all are a source of energy improvement.
Electromagnetic Measurements While Drilling: a Telemetry Solution for Casing-While-Drilling.
Authors: Musa M Zarir , Bt Abdul Aziz Dian Semesta , Budi Setiawan Trigunadi , Hermawan Heru , Kardani Ilen , Askar Ali Mohd Azlan , Sidek Rosli
Published: October 2012

Casing-while-drilling (CWD) operations have become a well-known technology used to minimise drilling time and reduce AFE budget. PETRONAS has drilled several wells in Malaysia by using this technology, and it has proven to be a cost efficient strategy particularly in batch drilling process.

Past CWD operational experiences have demonstrated stark differences when compared to conventional drilling in terms of wellbore surveying and formation evaluation. Weak and noisy signals from mud pulse telemetry were primary issues that required a significant amount of rig time when acquiring measurement-while-drilling (MWD) and logging-while-drilling (LWD) data.

In fact, several significant challenges were encountered. First, the mud pulse signal which traverses from downhole (MWD) to the surface somehow dampened out. Although various types of mud pulse telemetry have been used, significant problems remain. In addition, the signal transmission worsened when seawater was used as the drilling fluid, resulting in nonproductive time due to provisioning ofchange out tools with different configurations for mitigation and trial-and-error purposes. Finally, overall drilling efficiency was reduced as a result of poor signal detection and capturing.

EM-MWD used in combination with gyro-while-drilling (GWD) was identified for implementation when drilling four wells using Tesco CWD technology in the Erb West field. The mud pulse and electromagnetic telemetry systems were executed asa pair to compare captured signal strengths in the same environment, i.e., directional CWD with seawater drilling fluid.

After drilling ceased, the generated results proved that EM-MWD is a viable technology that can be used to overcome signal attenuation issues in a CWD operation. It also minimise health, safety, and environment (HSE) risks as well as established a working model of EM-MWD-CWD. Most importantly, such application reduced rig time by 3.9 days which contributed to 26% of cost saving for the surface section drilling by having trouble free MWD signal detection and faster drilling operation.
Slugs-fracs reassessed well fracturing conditions for Kamennoe field in Western Siberia
Authors: Platunov Andrey , Nikolaev Maxim , Leskin Fedor , kaluder Zdenko , Davidenko Igor , Ganin Oleg
Published: October 2012

Slugs-fracs is one of new-to-field approaches which changed the conditions of wells for fracturing increasing the number of candidates in Kamennoe field Western Siberia. Placing fracturing jobs by slugs of proppant pumped in linear gel successfully implemented in stimulating pay zones in near water intervals with small stress contrast between zones and barriers. A few technical specifics had been used to contribute the success of this methodology such as earlier pumping with near matrix rate to allow more fluid filtration ahead of the main proppant stages before fracture is fully formed. Proppant setting according to Stokes law and dune effects theory were evaluated and considered for design strategy. The slugs-fracs allowed pumping regardless of the wellbore deviation and height of perforated intervals. Post-fracturing results from 120 wells were used for analysis. Significant decrease in initial water cut and sustainable oil production were reported. First slugs-fracs were introduced in the beginning of 2010 and in following 2 years more than 200 hundreds jobs have been pumped across the field. This allowed to drill spots of the field that were previously suspended as result of ineffective fracturing treatments mostly due to high risk of fracture breaking down the water zones.
A Novel Effective Triglyceride Microemulsion for Chemical Flooding
Authors: Jeirani Z. , Jan B. Mohamed , Ali B. Si , Noor I. Mohd , See C. H. , Saphanuchart W.
Published: October 2012

This paper presents determination of aqueous phase composition of a new triglyceride microemulsion in which the triglycerides constitute the whole oil-phase of the microemulsion. Palm oil was used as the oil phase of the microemulsion. Experimental results indicate that the optimum triglyceride microemulsion was achieved when equal mass of palm oil and the aqueous phase containing 3wt% sodium chloride, 1wt% alkyl polyglycosides, 3wt% glyceryl monooleate, and 93wt% deionized water were mixed. The formulated composition of the aqueous phase was able to form translucent Winsor Type I microemulsion with palm oil at ambient c nditions. The measured interfacial tension between the optimum microemulsion and the model oil, which is n-octane in this study, was 0.0002mN/m. The maximum tertiary oil recovery of 71.8% was achieved after the injection of the optimum microemulsion formulation to a sand pack. The significant increase in total oil recovery (87%) suggests the effectiveness of the triglyceride microemulsion formulation for enhanced oil recovery. Its capability in recovering additional oil (4.3% of the trapped oil after water flooding) compared to a typical polymer in tertiary oil recovery indicates the efficiency of the optimum triglyceride microemulsion formulation.
A Great Way to Make your Invert Emulsion Fluids Green!
Authors: Wagle Vikrant , Kulkarni Dhanashree , Maghrabi Shadaab
Published: October 2012

Invert emulsion fluids (IEF) typically consist of an aqueous brine internal phase emulsified into an oil external phase. Conventionally, an aqueous solution of calcium chloride is used as the internal phase to balance osmotic pressures while drilling through shales. The use of traditional chloride salts, however, can cause disposal issues and environmental concerns while drilling onshore wells. To address these concerns and to provide an eco-friendly green invert emulsion fluid with improved technical performance, two types of salt-free IEFs have been developed: clay-based and clay-free.

The salt-free IEFs comprise a biodegradable and non-toxic internal phase to mitigate the potential negative effects of a brine-based IEF. The internal phase of the new fluid achieves 70% biodegradation in 28 days in accordance with OECD (Organisation for Economic Co-operation and Development) method.

The 12.0-ppg and 16.0-ppg salt-free IEFs, both clay-based and clay-free, were stable at temperatures greater than 300°F. The salt-free clay free IEFs were formulated in the presence of a novel organic secondary emulsifier. These salt-free fluids exhibited comparable rheological and fluid loss properties and offered improved shale inhibition as compared to conventional IEFs. The salt-free IEFs showed good tolerance to contaminants and static ageing. Shale erosion and shale swelling performance of the 12.0-ppg and 16.0-ppg salt-free IEFs were comparable with the CaCl2 based conventional IEFs. This paper presents experimental data corroborating the technical and environment performance of salt-free IEFs.

Salt-free drilling fluids formulated with this biodegradable and non-toxic calcium chloride alternative provide a solution to environmental concerns. The novel salt-free clay free fluids also eliminate the use of organophilic clay, thereby resulting in an IEF with low solids content, better equivalent circulating density (ECD) control and faster rates of penetration (ROP).
Addressing the Challenges of Production Forecasting in the Remote Highlands of Papua New Guinea
Authors: Sullivan S. , Rowse J.
Published: October 2012

Operational conditions in the remote highlands of Papua New Guinea bring a multitude of challenges including complex geology, steep jungle terrain, extreme rainfall, a sensitive ecosystem, a variety of landowner cultures, ageing facilities, mature reservoirs, and fraught logistics. These factors conspire to increase the complexity of production forecasting well beyond just reservoir performance.

After missing production targets for a number of years, a significant improvement in forecasting was needed to fully capture the uncertainties, both identified and unforeseen. A probabilistic forecasting tool using Monte Carlo simulation has been developed which incorporates assessments of all major variables and takes account of historical performance and system changes.

Successful implementation has resulted in the generation of realistic targets which have been met within four per cent for three years. Further, a clearer understanding of potential threats and opportunities combined with their impact on production has been achieved. These results have delivered material benefits to business planning, decision making and company reputation. Data to be presented on the forecasting tool will describe the quantification of uncertainty for each major variable including reservoir and facility performance, incremental production opportunities, project schedules and major unplanned downtime.

This approach could be applicable to E&P companies operating in difficult conditions worldwide, where unreliable production targets have a major business impact. It is flexible enough for both short and long term forecasts, tracking and reporting, and adaptation to new or changed operating conditions.
Various Methods to Detemine Relative Permeability in Fractured Reservoirs
Authors: khosravi Vahid
Published: October 2012

The relative permeability curves do not share the same degree of acceptance and credibility. This is particularly serious because the estimation of reserves in natural processes and in EOR projects using immiscible fluids (water, gas, steam) heavily depends on relative permeabilities.

Most of the relative permeability in fractured reservoirs measurements are performed through the unsteady state method, by which the reported end points correspond to steady state flow conditions (homogeneous saturation and single phase flow), while the intermediate values are calculated during a transient stage in which sample saturation is not homogeneous. Because of this, the end point saturations should have greater validity than the remaining points in the curve, since the shape of the curves in heterogeneous systems depends - among other things - on the mobility ratio, while it is generally accepted that the end points - if properly extrapolated at the end of the test - are independent from it. It is generally believed that residual oil saturation, Sor, is obtained only after injecting "infinite" poral volumes of water.

In many cases, the production curve, the residual oil saturation and the permeability to water - at such saturation - notably depend on the flow rate used during displacement. Although laboratories take different steps to correct, or not, the measurements performed, they mostly fail to inform what flow rates were used in the lab or the range of application of the reported data. The relative permeability curves presented by the labs are usually continuous along the entire saturation range between Siw and Sor.

Based on the above considerations, it would seem reasonable to conclude that, in order to properly characterize the reservoir, the different displacement mechanisms and flow directions should be studied to analyze their effect on the production curves used to determine the system relative permeabilities.
Introduction of a Dual ESP with Bypass Tubing and Backup Gas Lift System in an Offshore Brownfield
Authors: Zaini Muhamad Zaki , Rivero Maria Elba , Sepulveda Willem , Salim Muzahidin M , Bela Sunanda Magna
Published: October 2012

This paper will outline and discuss the processes involved from planning to conceptual design, detailed design, equipment preparation and onsite execution that has contributed to the successful offshore installation of Malaysia's first dual ESP system. It will also highlight the challenges and issues encountered throughout the project. The well was originally completed in 1989 as a single producer with gas lift. It is closed in 2004 due to high solid production. A workover operation was carried out in end of May 2011 to revive the well. The current producing zone was plugged and abandoned and the shallower producing interval is opened up and completed. Instead of continuing with the status-quo, gas lift strategy the well is completed with a Dual ESP system with bypass tubing, making it the first ever dual ESP installation in Malaysia.

Gas lift has been predominantly used as the main artificial lift strategy in the region. It's relatively ‘cheap’ resources and simple application has been the main driver for oil operator to continue using it as their preferred option. However as the water cut increases and lift gas supply become limited there is a need to have a look on the so called ‘commodity’ artificial lift application. ESP has been seen as one of the most attractive alternatives. The field's first conventional ESP installation with a backup gas lift system in 3 wells was installed in late 2008. In 2010 another ESP with pod configuration was installed. Ever since then, Bokor Project Management team has started to explore on the advancement of ESP system in order to find the optimized design for Bokor Field. However there are several challenges to be addressed. Justification to use a dual ESP system rather than a conventional gas lift system or single ESP configurations that has been done previously in 4 other wells, especially in term of initial cost.The complex installation of a dual ESP system complete with bypass tubing and gas lift backup system which is not a common practice in the areaDesign considerations and challenges for a successful installation. A complete design of a dual ESP for well specific application.Installation challenges of Dual ESP system with bypass tubing and backup gas lift system utilizing a hydraulic workover unit which has limited handling capacity compared to a conventional rig.Surface requirement and limitations of the existing facility for ESP commissioning and startup.

Among others, the paper will discuss on the justification and technical solutions that have been proposed for the installation of the dual ESP system in Bokor field. Lesson learned from the project is also compiled in this paper for any future similar installation in the field
Acidizing Technology in Complex Volcanic Gas Reservoirs--Case Study
Authors: He Liu , Changyu Liu , Honglan Zou , Yang Gao
Published: October 2012

Nowadays, as the deep gas reservoirs in Daqing are explored, the complex volcanic reservoirs have been the major reservoirs in deep natural gas exploration and production. The reserves of volcanic gas reservoirs take up 88% of the total gas reserves. However, the deep complex gas reservoirs may cause heavy pollution during the drilling completion, and some of the barriers between target zones of the wells are very thin, leading to a poor stability. Additionally, because of the complex water/gas relations in the formation, such as appearance of bottom water and water and gas sharing the same formation in some wells, the fracturing operations will induce water channeling. All these facts may cause the failure of the fracturing operations.

Especially, when the fractured formation is close to the water/gas interface, the fractures will easily extend into the water layer. The existence of water in the gas wells directly leads to the reduction of production and recovery rate of the gas reservoirs, or even kills the gas reservoir in the worst cases. For these types of gas wells, acidization technology is a promising solution. It not only avoids the pollution near the wells of volcanic formation, but also chemically dissolves the fillings in the fractures and pores, improves formation seepage flow environment, increases fluid mobility, and finally optimizes the productivity. Acidization technology also has the advantages of low investment and quick payback.

This paper reports the volcanic reservoir acidization technology we developed. The lab test results show that this technology solves the problems of high erosion rate of the oil strings under high temperatures (125-160 degree of Celsius). The acidization technology is applied in three wells, and the productivity of those increases profoundly.
Production of Methane and Water from Coal Seams and the Associated Ground Surface Subsidence- a Numerical Model
Authors: Freij-Ayoub Reem
Published: October 2012

Production of methane from coal seems is achieved by pumping out large quantities of water leading to cleat pressure drawdown and hence methane desorption from the matrix, its diffusion through the micropores to the cleat system and out of the wellbore.

A coupled numerical model is developed within FLAC3D to simulate the production of methane and water from coal seams through depressurization and to investigate possibilities of land subsidence around the wellbore. The axisymmetric model simulates the drilling of a vertical wellbore through a formation containing 2 coal seams. The model couples Geomechanics and fluid flow. Langmuir desorption isotherms control the maximum volume of gas desorbed in the coal matrix at any specific pressure. The cleats are assumed to be initially full of water. Desorption of methane from the coal matrix and its diffusion into the cleat system is assumed to be instantaneous. The geomechanical behaviour of the formations follows a Mohr Coulomb yield criterion.

The model qualitatively predicts the quantities of produced methane and water from coal seams separated, overlain or underlain by lithologies of contrasting permeabilities. The presence of an aquitard between both seams ensures higher methane production and less water production. The highest methane production and least amounts of produced water were predicted for seams separated, overlain and underlain by aquitards. The model can predict the amount of ground surface subsidence in the region around the wellbore. Sunsidence up to 11 cm was predicted near the wellbore.
Thru-Tubing Isolation and Perforating in Large Casing Diameter
Authors: Syafruddin Muhammad , Fauzi Dedi , Ferdian Andru
Published: October 2012

Well-11 produced gas from the Kujung-2 and Kujung-3 (K-2 and K-3) carbonate formation of Ujung Pangkah Field. Even though it was producing from the biggest reservoir zone, the well had to be shut in due to watering out in two years. High molecular weight polymer was injected to shut off the water zone but with no success. The work over job aimed to isolate the watered out zone (K-2 and K-3) and to access K-1 formation which had never been produced. This rigless operation was carried out on an-manned production platform.

Thru-tubing isolation inside the 9-5/8-in. casing was the biggest operational hurdle of the project. The challenges addressed were; high expansion ratio of the inflatable plug; uncertainty of the casing's condition due to the sour gas environment; and a cement bailer operation to permanently isolate the formation. Perforating was successfully executed in the selected zone using deep-penetrating shaped charges. The results were satisfactory and the well produced three times more gas than expected.

This paper presents the strategies, challenges and the lessons learned for zonal isolation using a thru-tubing inflatable bridge plug combined with cement and the perforating of the K-1 formations to optimize the gas recovery factor.
Taking the Third Generation Multiphase Meter Subsea - Challenges and Design Choices
Authors: Berge Finn Erik , Tyssen Ingar
Published: October 2012

This paper presents an overview of the processes, design and technology choices behind taking the latest multiphase meter (with new measurement, visualization and tomographic techniques) subsea.

The paper will look at applications for the new meter and the benefits of designing a subsea version. With Asian operators' increased focus on EOR and flow assurance, harsher offshore environments and production over a wider range of process conditions, the new meter will have significant applications for accurately measuring flow rates under varied conditions.

The paper will describe the development process behind the new subsea meter. It will examine how a new flow computer was developed to enhance communications, the extended GVF range, and improved salinity measurements to allow more accurate measurements of flow in high water liquid ratio (WLR) and when GVF is high.

The paper will look at the design challenges in adapting what was previously a topside meter for HP/HT environments subsea and the challenges of developing a more compact version without technology compromises. This compactness is crucial, with many subsea manifolds in Asian fields already crowded with instrumentation.

The paper will provide an important technical contribution towards the goal of increasing flow assurance in Asia's offshore fields and will demonstrate how the new design concept and technology will be crucial for more complex condition monitoring and intelligent metering in the future.