bluuebunny/crossref_metadata_2025 huggingface dataset:
Project Priority Ranking Process
Authors: Gatta S. R.
Published: December 2007

Each year the Company plans capital and maintenance programs to enhance and safely maintain the production system while satisfying all statutory regulations including employees' welfare. In fulfilling its role as the corporate level planning body of the Company, the Planning Group considers a wealth of policy issues that may influence the selection of projects. The list of proposed projects invariably exceeds financial targets. Allocating Company's finite resources is crucial to its long-term success. An annual task therefore is to reduce the number of projects to be within the total budget, while recognizing the various strategic, tactical and HSE objectives represented by these projects.

The most successful companies are those that have a formal project screening process in place: they allocate resources efficiently, and commit to stopping on-going (carry-over) projects that do not meet continuation criteria (e.g. the project objectives have undergone revision). The focus of review, however, is on new Proposals. The prioritization process is a systematic and consistent method for determining preferred order for allocating limited corporate resources to fund capital projects.

A description of the ranking system applied is furnished. It may initially appear complicated because there is typically more than one dimension for measuring the impact of each project and more than one decision maker. This paper considers a real life application of the proposed project ranking methodology, adopting Delphi approach (that is instrumental in minimizing the bias) for the assignment of scores. These scores represent the alignment of each project with one or more Corporate Objectives, risk-consequence and probability of occurrence based on the descriptions under each rating category. The final ranking is derived from the initial ranking following management review that considers all possible factors, including project description, project scope, definition of alternatives, estimates of project cost & schedule, and project readiness.

The process lends itself for enhancement, revision and further improvements.
Nondestructive Testing Technologies for the Oil Industry
Authors: Basrawi Marwan , Keck Danny
Published: December 2007

Nondestructive Testing (NDT) is proving itself in the oil industry. Oil companies that are seriously investing in it are realizing millions of dollars per year in cost saving and/or cost avoidance. The most important investment in NDT is in the human resources. NDT is not only about equipment, but also even more about the professionals operating the equipment and interpreting the results. Proper training and certification is paramount in this aspect. Each newly developed NDT technique leads to another more effective one that may be adapted for purpose and finally implemented effectively. Effective implementation is achieved only through proper up-to-date training and certification for even the most conventional NDT techniques. Otherwise, high potential NDT technologies are procured to be doomed for failure through misapplication and then eventual surplus without the realization of any cost saving, quality and safety benefits.

After introducing the proven significance of NDT and its effective implementation, this paper presents some critical NDT technologies for the oil industry, from the most conventional to the more advanced, and their proper and appropriate application and resulting benefits.
Experience with Tripod Beta Methodology Applied to Serious Environmental Incident Investigation
Authors: Otutu F. , Agba S. A
Published: December 2007

The aim of a facility design and mode of operation is to ensure that there is no unintentional loss of containment4. However, despite best endeavours, loss of containment may, and sometimes does, occur and we need to understand the root causes, consequences and implications of such events.

Throughout the history of EP business, the pattern of Environmental incidents investigation had been the same: The discovery that corrosion, explosion or sabotage was the immediate cause of a spill always put an end to the investigation as if there is no need to look further-no need to see that such incidents are the effects of other causes, causes yet to be addressed. These yet-to-be-adressed causes is what this paper tends to address using the Tripod methodology (root cause analysis). Tripod is well known and widely used as a safety incident analysis tool. The objective of this paper is to demonstrate that its use can be extended to analyse Environmental Incidents as well.

Tripod analysis results will lead you to take both short term immediate corrective actions, as well as finding the underlying root causes (latent failures) hidden in the way we do our work that will cause similar problems in the future. By identifying actions to correct these underlying issues, we can continuously improve our overall business.
Asphaltene Remedial Technology Using Advanced Deasphalted Oil
Authors: Alkafeef Saad F. , Al-Medhadi Fahad , Al-Shammari Ali D.
Published: December 2007

It is well recognised among the scientific community that resin molecules play a crucial role in the stability of colloidal asphaltene particles in petroleum oils. The de-stabilization of asphaltene/resin interaction under the influence of any change in the thermodynamic parameters can cause asphaltene to precipitate. This may significantly add to petroleum field problems such as in-situ permeability reduction, as well as by contributing to serious plugging problems in the production facilities. The latter is the case in West Kuwait Marrat deep wells.

One of the remedial technologies that is used in the oil industry is to increase the concentration of the resins' chemical potential by developing synthetic resins to enhance the stability of asphaltene in the oil phase. This method sometimes can be ineffective due to the difficulty in predicting the resin chemical structure that is compatible with the asphaltene chemical structure. The objective of this paper is to introduce a method that is capable of increasing the concentration of resins in their natural state, including increasing oil's aromatic power solvency. The latter is an excellent solvent for well cleaning.

The stability of asphaltene was investigated using three different types of de-asphalted oils (DAO) derived from West Kuwait Marrat oil. The first DAO had only the asphaltene fraction removed; the second had the fractions of C5 to C9 removed, and asphaltene; the third had C5 to C15 fractions and asphaltene removed. The oil fractions were removed by a distillation process and asphaltene precipitated by n-pentane.

The results have shown that the resin concentration in Marrat oil was increased in volume by removing more oil fractions. It was observed that asphaltene stabilization is strongly influenced by the resin concentration. The influence of the aromatic power solvency has also been examined on asphaltene particles disaggregation, and it was found that disaggregation kinetic rates increase with increasing the aromatic concentration in DAO. No formation damage was observed by all DAO products during core flooding tests.
Successful Hydraulic Fracturing through Optimization Steps for High Rate Deep Gas Wells in Carbonate Reservoirs, Saudi Arabia
Authors: Al-Ghurairi F. A. , Solares J. Ricardo
Published: December 2007

Saudi Aramco is currently undertaking one of the largest gas development projects in the world comprising a large number of new deep wells, four world-class gas plants, and massive development of new infrastructure.

The Khuff reservoir is highly heterogeneous; thus, rendering traditional matrix stimulation treatments mostly ineffective as the development progresses to tight formation. This motivated Saudi Aramco to search for alternative cost-effective options to increase well productivity in order to meet project objectives. Hence, acid fracturing was selected as an option offering good success potential and the lowest implementation cost when compared to other evaluated alternatives.

This article describes the highly positive results achieved throughout an accelerated acid fracturing campaign, successfully implemented by Saudi Aramco, comprising more than 80 treated wells, which have yielded a two-to six-fold increase in gas rates. Details of an ongoing optimization process, combining technology and partnering with other Saudi Aramco organizations and Service Companies, accountable for the success achieved to date are also desirable.
The Damascus Study Centre
Authors: Otri Ahmad , Castelijns Joop
Published: December 2007

Even in the relatively mature oil fields of Al Furat Petroleum Company, there is large scope for further increased recovery, predominantly related to optimisation of the waterflood sweep-efficiency through infill drilling and to application of enhanced oil recovery techniques. In either case, in-depth integrated study work using the latest subsurface technologies is required to understand the complex reservoir geology, to identify and quantify bypassed oil pockets and to propose activities for further field development with a resulting recovery improvement. In 2001, the Damascus Study Centre was set up by AFPC to create the additional study capacity required. Important advantages of a local study centre, as opposed to outsourcing of study work, are in the areas of technology transfer, communication with the company's operational departments, building-up and retaining company-specific expertise and national staff development. However, there is a risk that a local study centre gets overly involved in urgent operational activities and gets distracted from the long-term study objectives. A delicate balance between the Study Centre's short-term and long-term objectives is established through a combination of organisational ringfencing and application of a fit-for-purpose study methodology. The Damascus Study Centre, which started its activities in June 2001, has already made a significant contribution to the company's performance in terms of production, ultimate recovery, technology implementation and development of young Syrian staff.
The Nimr Story: Reservoir Exploitation Using UBD Techniques
Authors: Ramalho J. , Medeiros R. , Francis P. A. , Davidson I. A.
Published: December 2007

In May 2002, Petroleum Development Oman (PDO) embarked on a ten well, underbalanced drilling (UBD) trial campaign in the Nimr field using crude oil as the drilling fluid and membrane generated nitrogen as the lift gas. UBD was proposed as a productivity improvement technique for the Nimr field following a low risk/high reward analysis. The Nimr field is a complex of six fields. UBD was implemented in the Nimr A field consisting of two reservoirs: the Amin and Al Khlata, which are generally high permeability (±1Darcy) sandstone reservoirs containing medium gravity (21° API) viscous (300-500 cP) crude.

Horizontal wells are generally completed with a wire-wrap screen (WWS) across the reservoir section, due to sand production history in some wells, and are produced via artificial lift methods, primarily beam pump. Even though the predominant factor affecting net oil rate performance was the rate and behavior of water cut development it was suspected that drilling-induced skin, combined with mechanical skin from the completion, was a contributing factor to recent poor results from the horizontal wells.

The paper will demonstrate the value of a multi-well campaign to avoid eliminating a good candidate reservoir due to inconclusive start-up results associated introducing a new technology. It will describe some of these early start-up challenges, the equipment modifications and changes to operating procedures that have resulted in the uptake of this game-changing technology in the Nimr field. Additionally, it will emphasize the potential value of well inflow and reservoir characterization data gathered during UBD operations. This data indicated significant opportunities to improve well performance and increase ultimate recovery resulting in a potential value far exceeding those originally envisaged prior to initiating the UBD trial.
A Direct Comparison Between Conventional and Underbalanced Drilling Techniques in the Saih Rawl Field, Oman
Authors: Culen M. S. , Harthi S. , Hashimi H.
Published: December 2007

The history of UBD in Petroleum Development Oman stretches back to sporadic projects in the mid 1990's, however it has not been until recently that tangible gains have been realized using the technique.

Although the benefits of UBD are widely accepted within North America, internationally the technology has not been fully exploited for a number of reasons, namely the justification of increased drilling costs against perceived ‘intangible’ benefits. Such a justification is particularly hard for asset managers and well planners to make in the absence of any concrete industry data regarding production increases.

PDO embarked on a focused campaign to trial UB and evaluate its applicability as an enabling technology. A ‘Zero Cost Implementation’ approach was used to introduce the campaign, and drilling began in June 2002. Wells targeted in the Saih Rawl Field are under pressured oil wells, drilled as 5 legged producer-injector pairs off of a 7" backbone. The wells are normally completed by means of an Electric Submersible Pump.

Engineering for the UB project in Saih Rawl focused on the Asset Team's mandate of eliminating reservoir damage. Consequently, equipment was chosen and a program developed utilizing the injection of field natural gas via a concentric casing string to establish UB conditions.

As the technology was newly re-introduced to PDO and its local contractors, a stepwise approach to drilling underbalanced was adopted for the first well, and ultimately demonstrated the benefits of UBD. The first two legs of the first well were drilled conventionally overbalanced and stimulated, while the third leg was drilled overbalanced, stimulated and tested with the UB separation equipment. The remaining two legs were drilled underbalanced and tested.

The post drilling flow tests proved to be invaluable for evaluating the applicability of UBD, as the results showed a distinct increase in production from adjacent legs approximately 200 m apart in the same reservoir. This paper focuses on the design issues and the results of drilling SR 153 underbalanced.
Reservoir Characterization during UBD: Methodology and Active Tests
Authors: Vefring Erlend H. , Nygaard Gerhard , Lorentzen Rolf Johan , Nævdal Geir , Fjelde Kjell Kåre
Published: December 2007

In this paper methodologies for reservoir characterization during underbalanced drilling is presented. In these methodologies we are using a transient wellflow model coupled to a transient reservoir model, and use estimation techniques to estimate reservoir properties. Our focus is to estimate the permeability and reservoir pressure along the well, using measured data usually available while drilling. The measured data are outlet rates, pump pressure and downhole pressure. The liquid injection and gas injection rates are used as input to the model. The methodologies are applied to synthetic cases.
Using Fuzzy Logic for UBD Candidate Selection
Authors: Garrouch Ali A. , Labbabidi Haitham M. S.
Published: December 2007

This paper describes the development of an expert system for deciding whether to drill underbalanced or overbalanced. The expert system screens rock parameters that favor the design of an effective underbalanced drilling program. Once it is concluded that a particular reservoir presents a good candidate for underbalanced drilling technology (UBD), a screening procedure is then followed to select the optimal UBD technique. The following list of underbalanced techniques is considered in our expert system: liquid drilling (flow drilling), dry air drilling, nitrogen drilling, mist drilling, nitrified mud, aerated mud, and stiff foam drilling. The system screening procedure is put in an interactive advisor system that accounts for subsurface and surface safety, minimum rock formation damage, and wellbore stability. The expert uses a set of known facts and heuristics to measure the reservoir susceptibility for damage caused by clay swelling, fines migration, lost circulation and wellbore collapse.

A knowledge base development tool (Resolver) that consists of various utilities for developing and maintaining the rules, and implementing inference mechanisms was used in developing the expert system for selecting a candidate UBD technique. The principal attractive feature of ReSolver is that it supports fuzzy logic among other confidence modes. Membership functions were defined to assist the expert system in making decisions when the decision variables fall in a "gray area". Membership functions were constructed for variables such as lost circulation, clay swelling, fines migration, hard drilling potentials, cost benefit, gas influx and water influx potentials, fire potential, and stuck pipe potential. When the final outcome consists of a set of drilling fluids rather than a single one, these drilling fluids options were even screened further by the expert system to assure that the UBD fluid density is adequate within the pressure window. If the expert system still recommends more than a single drilling fluid option, a confidence level is given with each option.

Drilling underbalanced offers several benefits compared to conventional drilling techniques. These include, increased penetration rate and bit life, reduced probability of sticking the drillstring downhole, minimized lost circulation, improved formation evaluation, increased well productivity, and the reduction of stimulation treatments. The extent to which it is possible to achieve any of these benefits is generally controlled by the properties of the target reservoir and the overlying formations, and in some instances even by the specific characteristics of the well being drilled. The need for a fuzzy expert system that guides the user to optimally drill a well underbalanced becomes evident when we consider the delicate balance between the numerous coupled factors affecting the success of this operation.
Bitterweed S. (Caballos) Field: A Case History in Changing Economics Using Underbalanced Drilling and Open Hole Completions
Authors: Jaramillo Mike
Published: December 2007

The ultimate goal in any business is to maximize profits. In the oil industry this is done by reducing costs and/or increasing production. Increasing production rates or increasing the recoverable reserves can achieve profits from production. In this study we look at how underbalanced drilling (UBD) and open hole completions changed the economics in the Bitterweed S. (Caballos) Field.

The Bitterweed S. (Caballos) Field was discovered in 1983, in Pecos County, Texas by Tenneco Oil Company. Currently, Riata Energy Incorporated, in order to improve the economics of its wells, is using underbalanced drilling and open hole completions, as well permit in the Caballos formations. This study will look at several wells drilled in the Caballos formation with conventional or underbalanced methods. Depending on the area the Caballos formation can be found from 4500’ to 7700’.

Underbalanced drilling is used to improve well productivity, drilling performance, and an understanding of the reservoir. Well productivity is improved by minimizing formation damage caused by drilling mud, cuttings, fluids, and cement entering the formation. These items can cause skin damage and increase the cost of the well by requiring costly stimulation operations. It is believed that by minimizing formation damage reserves can be increased.

Drilling performance is improved by lowering the bottom hole pressure, which increases the penetration rate and reduces drilling costs by reducing drilling days. Lowering the bottom hole pressure also enhances bit performance. Using underbalanced drilling methods minimizes lost circulation problems and differential sticking.

By passed gas zones can be found or studied by being able to monitor the flow continuously as the well is being drilled. Uncontaminated cuttings can be obtained using underbalanced methods and evaluated within minutes of drilling.

The Caballos formation is a commercial gas zone, which has been drilled conventionally and underbalanced. In this study, the well that was drilled underbalanced is producing approximately twice as much as the surrounding wells that were drilled conventionally at a rate of 3.33 MMCF/D as compared to a rate of 1.8 MMCF/D, respectively. IP's in the field have been 10 times higher for underbalanced wells but production is currently limited by pipeline capacity out of the field.
Marginal Field Development Using CT Completion
Authors: Bottazzi Franco
Published: December 2007

Coiled Tubing (CT) technique is mostly considered for drilling or well intervention operation rather than an effective completion tool. This paper aims to demonstrate, using examples carried out in Italy and in West Africa, that this technique is a surprisingly effective means for marginal field exploitation and mature fields rigenaration.
Coiled-Tubing-Conveyed Hydromechanical Pipe Cutting Enables Removable Packer Completions
Authors: McGurk Mark , Ponder Andrew , Smith Michael , Wilson Steve
Published: December 2007

Traditionally, completion engineers have faced a dilemma when deciding whether to run a large-bore, hydraulically set, permanent or retrievable packer completion. Thanks to advances in cutting technology, this decision is no longer an either/or proposition. The innovative alternative which has been enabled by through-tubing cutting technology is the removable packer completion.

Combining a through-tubing-conveyed hydromechanical cutter with a "cut-to-retrieve" packer had never previously been attempted. In addition to providing an innovative solution for difficult service environments, the new capabilities gained by combining these technologies has led to the development of a work-string-conveyed method of cutting and retrieving the packer, thus enlarging the scope of viable applications for the removable packer completion.

This paper will review the removable packer completion and the coiled-tubing-conveyed hydromechanical pipe cutting system and describe in detail how the technology was proven, both in the laboratory and at the rig, and how it is being used to design and complete wells in Alaska and Kazakhstan.
Inflatable CT Conveyed Selective Well Testing System for Logging Openhole and Horizontal Wellbores: Development and Use
Authors: Blount C. G. , Crabtree C. L. , Pierson C. R. , Rennie S. B. , Mackenzie G. R.
Published: December 2007

Quantitative production logging of openhole and horizontal wellbores presents a challenge for conventional logging tools and techniques. The complicating factors of horizontal logging are primarily related to low fluid velocities and stratified flow. Openhole horizontal completions further the challenge by increasing the opportunity for tool fouling and fill obstruction, creating abrasive running environments, and finally complicating interpretation with unknown hole geometries.

To address these challenges, a new diverter logging system based on inflatable packer technology has been developed. The tool is inflated at discrete locations in the horizontal section so that all flow at each stop is diverted through rock-excluding screens and past conventional memory logging tools in a carrier. Pressure drop through the tool is minimal, and the fixed internal diameter carrier allows for high resolution logging over a wide range of rates.

Developing a method to allow packer setting and resetting in wire/umbilical-free Coiled Tubing (CT), while constantly maintaining a production or injection path through the tool, called for innovative engineering. The tool has been run in nine wells to date. This paper will discuss the need, development, and field results of the new inflatable packer logging system.
The Development of a Corrosion-Resistant Coiled Tubing Product
Authors: Martin J. R. , Van Arnam W. D.
Published: December 2007

This paper will review distinctive corrosive wellbore environments that can be detrimental to the performance of (High Strength Low Alloy) carbon steel coiled tubing which is typically used for workover/intervention and completion applications. The paper will demonstrate how these corrosive environments form the technical push and potential market pull for the development of coiled tubing suitable for specific corrosive applications. The product development of a corrosion resistant coiled tubing will be reviewed, indicating initial design input, verification data depicting corrosion tests, mechanical properties; inclusive of strength, hardness, full body low cycle fatigue and surface property attributes. The product range depicting diametrical and wall thickness ranges will be reviewed.

The paper will include manufacturing issues such as forming, welding and inspection techniques. The paper will conclude with a review of the strings manufactured to date with application case histories.
The Low Cycle Fatigue and Plastic Strain Response of Coiled Tubing in a Sour Environment With and Without Corrosion Inhibitor Protection
Authors: Luft H. B.
Published: December 2007

The post-yield material performance of 70 and 80 ksi yield strength carbon steel and high-strength corrosion resistant alloy (CRA) coiled tubing (CT) has been investigated experimentally to evaluate its response to a sour environment following plastic bending straining induced during coiled tubing operations. Although this investigation was specifically targeted for under-balanced drilling of sour wells, the results obtained can also be interpreted with respect to CT work-over operations. The four different types of laboratory testing performed were low cycle corrosion fatigue (LCCF), NACE proof ring tests, double cantilever beam tests (DCB) and slow strain rate tests (SSRT). Full-body CT specimens were used for the SSRT and LCCF testing procedures and only SSRT test results are presented for a specific CRA material. The test environments consisted of aqueous H2S, H2S/CO2, varying pH and the standard solution specified by NACE for determining the relative propensity for HIC and SSC. Tests were also performed using the NACE solution treated with an H2S corrosion inhibitor.

This paper presents the key findings from the carbon steel CT testing, the preliminary data for the experimental CRA CT and the basis on which these materials were evaluated for under-balanced drilling applications. Both 70 ksi and 80 ksi carbon steel grades were found to be fit-for-purpose for sour wells in accordance with certain qualifications discussed. A preference for the lower strength, 70 ksi CT has been identified when CRA materials are not being considered. For carbon steel, the low cycle fatigue (LCF) life in a non-inhibited sour environment was reduced to between 15% to 20% of the life in air depending upon the pH level. With the application of an H2S corrosion inhibitor, the LCF can be increased significantly to about 2/3 of the life obtained in air. The results of this research are currently being implemented for a revised issue of Industry Recommended Practises for Critical Sour Under-balanced Drilling-Drill String (IRP 6.3).
Coiled Tubing Abrasion – An Experimental Study of Field Failures
Authors: Larsen Henrik Aslak , Reichert Bruce A.
Published: December 2007

Abrasion between the Coiled Tubing and the well completion has been a significant failure cause over the last three years. In excess of twenty-eight of these specific failures have been observed, cataloged and investigated. These failures resulted in a series of experimental studies using a modified form of the ASTM G75 abrasion test. This test is performed with a test fixture that repeatedly slides test blocks over stationary test laps with a controlled normal force and in the presence of an intermediary fluid. In the tests reported in this investigation the blocks were made from 90 ksi yield Coiled Tubing material, the laps were made from 13Cr and L-80 tubing material, four different fluids and two different normal forces were used. The results are presented as a normalized wear rate to clearly demonstrate the high-risk conditions for abrasion. The risk associated with these failures is very high as catastrophic failures have been observed at pressures significantly below pre-job test pressures.

Well bore fluid is the most critical parameter for abrasion. Abrasion failures have occurred in both liquid and gas environments, while the gas environment severely worsens the problem. The abrasion in dry wells is almost 250 times worse than in liquid filled wells.

Based upon the experimental results, a methodology is proposed to determine the relative risk of incurring abrasion damage during Coiled Tubing operations. The methodology looks at Coiled Tubing and well parameters and results in an overall risk assessment. A table of critical running feet is given based on the overall risk assessment and minimum Coiled Tubing wall thickness. When the critical running footage is reached measures such as pressure tests or wall thickness inspection should be taken
Repair of an Openhole Gravel Pack Using Coiled Tubing
Authors: Ovesen Monica , Riise Mai , Tanem Siv Arna , Nesvik Kjell Tore
Published: December 2007

This case study provides an overview of the Coiled Tubing (CT) operation performed for Statoil on the Heidrun field in 2002. The operation covered cleaning of a downhole sand control screen utilizing the Roto-Jet Technology, followed by installation of new sand screens inside the existing screens and performing a circulating gravel pack with coiled tubing.

The reason for this well operation was to repair a sudden and massive sand control breakdown. It was anticipated that this resulted from plugging of the gravel pack screens and/or a gravel pack packer failure. The well was producing 1500 Sm3/day with a water cut of 30 % prior to detecting the sand production. The objective of this intervention was to stop the sand production by installing 3-1/2" screens inside the damaged 5-1/2" screens, and perform a circulating gravel pack between the old and new screens.

The operation was conducted using a compensated CT tower allowing handling and running of jointed tubulars. A total of 6 runs with 2-3/8" coiled tubing was performed to clean out sand, remove fines/kill pill behind the existing screens, drift the well prior to installing a gravel pack packer, run new screens and perform the gravel pack operation, install a straddle across the gravel pack port and acidize. To be able to deploy screens into the well, it was temporarily killed with a specially designed kill pill.

After the CT operation, additional acid stimulation has been performed to remove remaining kill pill and increase the PI. The well is now producing 700 Sm3/day. The CT operation was performed in 21.2 days, while the platform was drilling simultaneously.
Record Depth Coiled-Tubing Sand Cleanout and Gauge Retrieval
Authors: Schuurman Rene M. , Ellzey Tim , Powell John W. , Reichert Bruce
Published: December 2007

Drilling deeper wells with high angles are becoming the norm in the Gulf of Mexico. As time passes these wells require some type of intervention. Coiled tubing intervention being an economic option creates new challenges by pushing existing coiled tubing technology to its limits. Deeper holes increases string weights requiring stronger coiled tubing pipe, injector heads and surface equipment. Friction must also be addressed with improved fluid designs for reducing circulating pressures without compromising good solids transport capabilities or temperature stability.

Success of these deep interventions greatly depends upon proper equipment; job design, planning and execution of the plan to improve the original objectives achieved.

Evaluation of the objectives, well details, location concerns, and logistics are keys to designing the right coiled tubing string, selecting proper (BHA) bottom hole assemblies, fluids and procedures in these deep wells.

This paper describes the design, planning and execution of a record-depth job with 1½" coiled tubing in a 25,200 ft deep high-pressure gas well in the Gulf of Mexico. The objective of the job was to clean sand from the well, retrieve down-hole pressure and temperature gauges, and prepare the well for the re-completion with the rig.

Several steps were taken to ensure a successful job: A 28,700 ft 110,000 psi minimum yield strength coiled tubing string was designed and manufactured. A special hydraulically optimized fluid with high solids carrying and suspension capacity and relative low circulating pressures was designed and tested. In depth pre job planning was conducted. All these factors played key roles in success of the job.
New Life for Old Wells – A Case Study of the Effects of Re-Stimulating Gas Wells Using Fracturing Through Coiled Tubing and Snubbing Techniques
Authors: Gutor Chad , Al-Saleem Ali , Rieger Bruce , Lemp Stephen
Published: December 2007

The use of a coiled tubing conduit for the hydraulic fracturing of shallow gas wells in southern Alberta, Canada has increased each year since its beginnings in 1997. The coiled tubing fracturing (CTF) technique has been utilized for both new and old wells as a means of fracture-stimulating multiple reservoir intervals.

This paper will detail a re-stimulation project completed during the summer and fall of 2002, in which the CTF and snubbing-conveyed fracturing (SF) processes were utilized to re-fracture a group of shallow gas wells that were originally completed in the 1970s. The objective is to examine the possible ways of enhancing production of older shallow gas wells by fracture stimulation utilizing tubing-conveyed processes.

Specifically, the paper will outline ways to consider and select wells that are candidates for re-entries, in addition to the essential work and evaluation that has to be done both prior to and following the re-entry, re-perforation, and stimulation techniques. This study will also provide a relative comparison between conventional fracturing techniques used previously and the CTF and SF processes used most recently. Also included are pre- and post-stimulation production data that give a clear indication of how effective the fracturing through tubing process is when used to re-stimulate these older wells.
Is Acid Placement Through Coiled Tubing Better than Bullheading?
Authors: Mitchell Wayne P. , Stemberger Dario , Martin A. N.
Published: December 2007

It has long been postulated that placing acid into a well through coiled tubing provides for better stimulation treatments than those achieved by simply bullheading. Common sense suggests that having the stimulation fluid enter the well via a dedicated conduit, adjacent to all points along the length of a treatment interval, will produce more uniform stimulation of that interval. However, the opposing argument is that, irrespective of the delivery method, all fluid follows the path of least resistance and will, therefore, flow into the areas of highest permeability, the ones generally least in need of stimulation. Diversion techniques, employed to improve treatment distribution, can often be applied to regular bullhead treatments as easily or even more easily than they can with coiled tubing. This is not necessarily so when pumping stimulation fluids through SSD’s or through the ESP itself.

Controlled tests to compare bullheaded and coiled tubing delivered treatments are difficult, as no two wells are identical. This paper evaluates 19 wells to provide statistical evidence of which delivery system does generally provide for the best end results. The paper suggests what the underlying reasons for the spread of results might be and suggests criteria as to when coil is, and is not, the best probable choice. It also discusses innovative methods to improve treatment distribution in wells, thereby maximizing stimulation efficiency.
Gravel Pack Cleaning: A New Solution
Authors: Brunskill Doug
Published: December 2007

A large number of fields worldwide have sand production problems and a common solution is a gravel pack (GP) completion. Over time this GP can become plugged with production fines as well as solids that may precipitate out of the produced fluids. As the GP plugs, it creates a larger restriction to flow and the production rate will decline. At some point the operator will decide the production rates are no longer acceptable and intervention is required. As a result, the GP completion will either be pulled from the well or be cleaned in-situ.

Previous in-situ cleaning processes involved treatment fluids bull headed into the well or placed by coiled tubing, to dissolve GP plugging damage.

This paper describes a new method for cleaning a GP in-situ. The process involves a rotating jetting head to create specific pressure pulsations combined with angled nozzles to create a "circulation current" within the GP. These circulation currents are localised and result in a temporary increase in GP permeability ensuring that treatment fluid will invade the GP only in the area immediately adjacent to the tool. This new process is significantly more efficient at unplugging the GP than previous methods and treatment fluids can more effectively reach areas of the completion such as the perforation tunnels and drill-in fluid filter cake damage. This process also includes managing the jet impact pressure to ensure that fragmentation damage of the GP proppant does not occur.

The paper will report results of laboratory tests using existing wash methods compared with the new technique and demonstrate the differences in; treatment fluid placement efficiency, fines removal efficiency and damage caused to the GP proppant.
Cleaning Wire-Wrapped Screen Liners: Large Scale Field Study Shows Coiled Tubing Jetting to be the most Effective Technique
Authors: Wijaya Zein , Portman Lance , Hardianto Hardianto
Published: December 2007

This paper describes a large-scale field study that demonstrates the relative merits of four different approaches to a single problem. That single problem is the clogging of wire wrap screens in gravel packed producing oil wells resulting in poor well performance. The four methods evaluated are: -Jetting with acid using coiled tubingBullheading foam diverted acidBullheading acid diverted with benzoic acid flakesSqueezing acid between opposing cup packers

A total of 168 well treatments are evaluated within this paper. The large number of wells permits meaningful comparitive data; the statistical spread of the data has also been evaluated.

The data clearly shows that by far the most effective way of placing acid across a wire wrap screen is to jet with coiled tubing. This method provides for better well response, smaller acid volumes, faster jobs and a better than average cost per foot figure.

A payback analysis has also been conducted.
An Innovative High Strength Drill Pipe Mechanical Cutting Solution Using Coiled Tubing
Authors: van Steveninck Erik , Manson Jim
Published: December 2007

This paper will examine an unusual intervention case history for a major UK North Sea operator, where a specialised coiled tubing (CT) conveyed mechanical cutter system was used to allow the recovery of stuck drill pipe.

Previous to the CT being mobilised to the offshore installation, a number of conventional drill pipe recovery techniques had been tried. However, all proved unsuccessful in freeing the stuck DP.

The decision was made to mobilise CT, dictated by both the need to free the High Strength S-135 DP and to confirm the degree of ID access for future intervention options. Ultimately a series of three mechanical cuts were made within the drill string. All cuts were at depths greater than 14,000 feet with 11.8 PPG OBM in the well. The particular challenges presented during this operation and the steps taken to provide a successful outcome will be explored.
Flow Patterns and Minimum Suspension Velocity for Efficient Cuttings Transport in Horizontal and Deviated Wells in Coiled-Tubing Drilling
Authors: Kelessidis V. C. , Mpandelis G. E.
Published: December 2007

Coiled Tubing Drilling, grown significantly in recent years, is normally associated with high angle to horizontal and extended reach wells. It is, however, in these applications that hole problems become more troublesome because of inefficient cuttings removal. Among the many parameters affecting efficient cuttings transport in Coiled Tubing Drilling are pump rates, well dimensions, fluid properties, solids sizes, solids loading and hole inclination. Several attempts have been made to determine the optimum operating range of these parameters but complete and satisfactory models have yet to be developed.

The purpose of this paper is to provide a critical review of the state of the art on efficient cuttings transport during Coiled Tubing Drilling, present the critical parameters involved, establish their range according to what is observed in practice and propose a different approach for predicting the minimum suspension velocity. Finally the laboratory system that has already been set up is presented. Its primary purpose is to allow the gathering of good quality data, missing from the literature, which could enhance our understanding of the flow of solid – liquid mixtures in annuli.
Improved Reliability of Coiled Tubing Equipment by Utilisation of an Assurance Management System
Authors: Cowan M. J. , Smith I. , Angell P.
Published: December 2007

Reliability and the minimization of equipment downtime is an aspect of coiled tubing operations that is desirable, but all too often planned performance is below expectations.

The web enabled system presented in this paper allows operations engineers to review individual verification and inspection processes, monitor individual equipment compliance and decide on levels of verification activity based on historical reporting and defined operating hazards.

The starting point of the process is the development of the criticality matrix by the specifying engineer. The matrix is reviewed to determine the criticality ranking from a safety and business perspective. Once all critical elements have been defined and the level of assurance required is agreed with the client the assurance engineer prepares clear performance standards for each item of equipment and a crew competency assurance matrix.

The equipment and personnel are then inspected to the level established in the performance standards. This can involve full dynamic testing of the equipment, review of certification and maintenance records, personnel competence and work experience.

Using defined inspection criteria, the critical elements are assessed. Deviations from the criteria are actioned and a subsequent report raised and ranked according to impact.

Data generated by BP projects show a significant long term improvement trend of increased equipment reliability contributing to a major boost in client confidence in coiled tubing conveyed operations. This has been positively attributed as a result of the adoption of a reliability assurance management system.
Economics of Nigerian Marginal Oil Fields
Authors: Ayodele Oluropo Rufus , Frimpong Samuel
Published: December 2007

In this paper, a new contractual agreement is proposed for the development of marginal oil fields in the Nigerian prolific hydrocarbon sedimentary basins. The proposed agreement is a modification of the existing agreements taking into consideration the special nature of marginal oil fields. Detailed economic analyses were carried out to assess the feasibility of the agreement. The economic analyses involved cash flow modeling, project profitability analysis, project sensitivity analysis and risk modeling using available and generally accepted economic, financial and technical data about the Nigeria operating environment. The final results from this study show that investing in the development of Nigerian marginal oil fields is a worthwhile option. The results show that the proposed agreement leads to favorable return on investment for all the parties involved. Project sensitivity analysis shows that if the combined cost of seismic survey and signature bonus is increased by more than 10%, the project becomes uneconomic. Also, if the price of oil falls below US$18.07, the project would have to be re-evaluated because the discounted pay back period (DPBP) would exceed the expected project life. Furthermore, risk analysis shows that as the NPV (net present value) increases, the risk level associated with such NPV also increases. Options available for financing marginal oil fields development are also presented.
Integrating Deterministic and Probabilistic Reserves
Authors: Gair Robert
Published: December 2007

Probabilistic reserves evaluation offers the opportunity to describe a reserves volume in terms of the specific statistical certainty associated with that volume, as opposed to relying on the definitions associated with deterministic reserve classifications. Where a reserves entity has volumes identified for two or more certainty levels, knowledge of the reserves distribution may be used to interpolate reserve volumes at other certainty levels. This interpolation forms the basis of statistical reserves aggregation. Assignment of confidence levels to the deterministic categories of Proved or Probable supports both deterministic and probabilistic reporting.

This paper examines the mechanisms which control the shape of the reserves distribution curve; demonstrates the applicability of normal distribution curves to reserves distributions; and outlines a procedure for statistical reserves aggregation which may coexist with deterministic aggregation.
Consistent Performance: Reducing the impacts of price uncertainty through portfolio management practices
Authors: Allan Paul D.
Published: December 2007

Most companies recognize the importance of delivering consistent performance results, yet the ability to fulfill this objective is sometimes undermined by product price uncertainties. Many companies effectively manage the impacts of price uncertainty through the use of financial hedging instruments, while others have avoided hedging due to lack of knowledge, lack of company infrastructure, or political pressures. This paper addresses the reduction of uncertainty that may be obtained through portfolio management practices as contrasted to that achieved through financial engineering or hedging. A case study and computer simulation will be used to describe a portfolio management methodology for reducing the impacts of pricing uncertainty on performance results. The results will then be compared to strategies ignoring the variability of price, as well as strategies employing the use of typical hedging instruments.

The ability to reduce pricing risks through portfolio management is dependent upon project diversity (scale, timing, capital and fiscal structure) as well as the stated objectives of the organization. The results from the case study indicate that given an adequate cross section of opportunities, significant reductions in performance variability due to product pricing may be achieved through portfolio optimization. These uncertainty reductions may then be further enhanced through price hedging, as necessary to bring the overall level of uncertainty within a range acceptable to company decision makers or the market.

This case study and the resulting comparisons will demonstrate the way in which risk reduction through portfolio management may be used in conjunction with financial hedging to dramatically improve a company's ability to deliver consistent results.