bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Capillary Imbibition Recovery Considering the Simultaneous Effects of Gravity, Low IFT, and Boundary Conditions
Authors: Babadagli T. , Al-Bemani A. , Boukadi F.
Published: December 2007

Capillary imbibition is the dominating recovery mechanism in naturally fractured reservoirs if matrix is water wet and continuous supply of water through fractures exists. The mechanics of the process still needs clarification for complex conditions. Matrix boundary, i.e., the contact areas of fracture fluids with matrix blocks, is one of the causes of this complexity. Capillary imbibition rate and ultimate recovery are significantly affected by the partial contact of water with the matrix due to phase segregation in fracture by gravity or impervious layer covering some part of the matrix.

This study aims at analyzing the recovery behavior experimentally for different boundary conditions and proposes remedies to increase the ultimate recovery. Berea Sandstone samples saturated with two types of oil are exposed to counter-and co-current capillary imbibition at ambient temperature and pressure conditions. Matrix boundary conditions, i.e., the matrix-water contact areas, are changed by covering the sandstone sample surface using epoxy. The oil recovery in non-contacted area of the matrix is due to gravity segregation and also re-imbibition of water that is already imbibed by the matrix blocks. To remedy low oil recovery from the parts of the matrix where no contact with water exists, the same experiments are repeated using low IFT solutions. It is observed that the low IFT solution yields in higher oil recovery from the non-contacted part of the core sample. But, the recovery rate decreases when the low IFT solution is used instead of brine especially for the unfavorable boundary conditions.
Case Study: Coalbed Methane Automation System for River Gas Corporation
Authors: Robertson Steve K. , Pool Mike , Farrens Michael J. , Butts Tammie J.
Published: December 2007

Can an independent producer fulfill a vision to develop and produce a coalbed methane gas field that covers two hundred square miles in a remote desert plateau in the western United States? This paper will answer that question as well as provide answers to other pertinent questions, such as, "What tools would be available to the operator to efficiently and safely produce the wells?" And, "Would the tools allow for future expansion and/or allow new technologies to be incorporated into the system cost-effectively?"

This case study will show how River Gas Corporation was able to successfully meet their needs with an automation system that was jointly developed with an engineering/ manufacturing company. All phases of the project, from its inception in 1991 with a 13-well pilot project to a planned 600-well development will be discussed. Innovative solutions successfully answered the above questions and allowed the system to evolve to meet the continuing changes in expansion and production needs.
Coiled Tubing Ultrashort-Radius Horizontal Drilling in a Gas Storage Reservoir: A Case Study
Authors: Stiles E. Kevin , DeRoeun Mark W. , Terry I. Jason , Cornell Steven P. , DuPuy Sid J.
Published: December 2007

The subject paper is a review of the philosophy, planning, execution and results for the first successful Coiled Tubing Drilling ultra short radius horizontally drilled well into a gas storage reservoir. The paper will seek to describe the process and results for the just mentioned areas.

The philosophy behind CTD and the idea of using it as a tool to enhance gas storage deliverability and the associated costs are considered. This well achieved an 800% increase in gas deliverability after sidetracking, as compared to the original wellbore. The idea of rate of penetration enhancement is strongly conveyed to help the audience understand how this drives drilling parameters and hence, cost.

Planning for CTD operations is discussed and includes a geological discussion. The use of Coiled Tubing and the BHA used to perform this operation are discussed. One tool for several functions drives down cost by reducing process steps.

Execution of the project from mobilization to demobilization is briefly discussed as are lessons learned. Ideas are suggested for further improvement. Some of the issues identified to date will be much more refined prior to paper delivery. This is due to the idea that more work is on the immediate horizon

The first well (KW-34) was re-entered and sidetracked in September, 1998.
"DIP" Fire Fighting and Blowout Control System
Authors: Armanda Davorin , Kovacic Ante , Posavec Vjekoslav , Seletkovic Danko
Published: December 2007

The uncontrolled blowouts of oil, gas and geothermal waters are one of the major problems encountered in oil and gas exploration and production. The problem is even more complex if the flowing fluid contains aggressive components (hydrogen sulphide H2S, carbon dioxide CO2, mercaptane). It is almost the rule that fire follows the uncontrolled well blowouts, where the following problems are encountered:

Efficient fire fighting on uncontrolled blowout wells Fire fighting with existing devices (without additional investment) Fire fighting meeting ecological requirements (pollution should be reduced to the minimum). This is article is describing the fire fighting and blowout control system on oil and gas wells called "DIP ".
Improving the Working Environment and Drilling Economics through Better Understanding of Oil Based Drilling Fluid Chemistry
Authors: James R. , Navestad P. , Schei T. , Geddes T. , Nelson G. , Webster D.
Published: December 2007

The relationships between oil based drilling fluid composition and the associated vapours have been quantified. This information will provide drilling Operators with improved control in the working environments. The study documents the long and short term changes in base oil selection and fluid compositions. The study is based on the generation and assessment of data collected from the vapour emissions of oil based drilling fluids with varying compositions and at a range of temperatures.

Mineral oil based drilling fluid samples from the field have been investigated and compared to laboratory samples of similar basic composition. The impacts of other components in the drilling fluid formulations are also discussed.

The purpose of the study was to enable a better understanding of the potential working environment hazards when using mineral oil based drilling fluids. One result of this understanding is that new rig construction designs, and older rig upgrades can be more informatively performed. Consequently this will reduce the repetition of continual modification costs.
Cost Savings through an Integrated Approach to Drillstring Vibration Control
Authors: Kriesels P. C. , Keultjes W. J. G. , Dumont P. , Huneidi Issam , Owoeye O. O. , Hartmann R. A.
Published: December 2007

Drillstring vibrations occur frequently during drilling operations. They can result in drillstring failure, fishing and, in the worst case, side tracking. At the same time, the rate of penetration and the bit/downhole tool longevity are reduced. All these effects of drillstring vibrations lead to substantial additional well cost.

An integrated approach towards vibration control, addressing all the contributing factors, can have a positive impact on well costs. This is especially true for hard rock drilling, as frequently occurring in Middle East countries. Various types of vibration can be distinguished, each having their own specific adverse effects. The integrated approach, developed in Shell, consists of the following elements:

The application of a soft torque rotary system (electric and hydraulic rotary drives) for suppressing (torsional) stick slip vibration of BHA and bit. The use of vibration analysis software in the design of a BHA, to prevent buckling and to identify safe operating windows for rotary speed. The cost-effective deployment of vibration monitoring tools. The regular inspection of drillstring components.

Field cases of the deployment of this methodology reveal that twist-offs can be reduced by more than 80% and drilling performance in terms of ROP and bit life can be improved. Cost savings are realised through the reduction of well days and prevention of tool failures. A limitation of the method is that safe operating parameters are not available under all circumstances.
Theoretical Maximum Performance, ProStar Rig 2000
Authors: van der Leij E. , Zuidema F. , van Tuyl G. , de Jong P. , Anderson B.
Published: December 2007

The PT 2000 was built as a state-of-the-art land drilling rig designed to achieve safe and efficient operations through automation and the removal of personnel from the working envelope. After two years of mediocre performance, Theoretical Maximum Performance (TMP) was adopted as a method for improving rig operations by developing people in the workplace. Performance coaches were placed on the rig for a twelve-month period. They encouraged innovative thinking and greater commitment to the job. By invoking numerous tools around the Plan / Execute / Measure / Learn continuous improvement cycle, the crew of the PT 2000 achieved sub-stantial performance gains, specifically in rig move times, rig downtime, and BOP Testing. The rig's impressive safety record was not compromised. Using this approach, the PT 2000 drilled five wells in 1998 and saved 71 days from the budgeted time for these wells. Deutag Drilling sees this innovative approach as a valuable contribution to its business.
Successes in Production-Liner Cementing in Oil-Based Mud: A Case Study
Authors: Al Khayyat Bader , Morris Jesse A. , Salahudin Sharifudin , Ravi Kris , Faria Juvenal
Published: December 2007

The 8½-in. hole sections of two fields in Kuwait have historically presented drilling problems associated with swelling shales and differential sticking. This drilling problem was alleviated by changing from a water-based drilling mud (WBM) to an oil-based mud (OBM). The change from WBM to OBM significantly reduced drilling problems; however, zonal isolation in the sand and limestone sections suffered, causing poor cement-bond logs across the 7-in. production liners. This paper presents the case histories of several wells in which zonal isolation problems were overcome, and production liners were successfully cemented.

In an attempt to determine the nature of the cementing problems in these two fields, the authors thoroughly analyzed the wells and completion designs. They reviewed formation properties, hole condition, mud properties, slurry and spacer designs, openhole logs and cement bond logs (CBLs), and the placement techniques of the affected wells. This paper documents the conclusions of this study, as well as the products and processes that significantly improved the zonal isolation of the 8½-× 7-in. annulus. CBLs performed across the intervals of four wells drilled with OBMs and cemented with improved products and processes indicate significantly better bonding than previous logs. These wells are currently on production and are being observed for short-and long-term performance.
A New Well Design and Construction Process
Authors: Clay Tim , Hatch Andy
Published: December 2007

The upstream oil and gas industry is being increasingly challenged by market price volatility, higher exploitation costs and growing environmental concerns. Working in the mature UK North Sea province, ARCO British Limited has recognised that it needed a better business process to deliver consistent, top-performing well execution in both exploration and development projects. A multidisciplinary process redesign team identified that approximately 70% of the deficiencies in the previous ABL process lay in lack of project definition and planning rather than in poor execution.

A new process has been rolled out which uses both front-end loading techniques to identify the best economic execution plan and organisational learning to achieve repeatable high performance. Recent project successes indicate that a fit-for-purpose well design and construction process has been established.
Trial of an Expandable Sand Screen to Replace Internal Gravel Packing
Authors: van Buren Mark , van den Broek Léon , Whitelaw Calum
Published: December 2007

In January 1999, Petroleum Development Oman installed an Expandable Sand Screen in the Rahab field. The expandable sand screen was installed across a newly perforated production interval in an existing well. The low production potential precluded the economical installation of an Internal Gravel Pack across the new interval for mandatory sand exclusion. On the other hand, the limited production exposure provided an opportunity to trial a novel, potentially more economical, alternative to gravel packing. The opportunity was therefore taken to trial an expandable sand screen. This trial is the first application of an expandable sand screen in a producing well. The installation of the expandable sand screen proceeded smoothly. The sand exclusion performance to date has been exemplary. Production tests show an increase in gross and net production rate in line with expectations.
Successful Drilling of an Underbalanced, Dual-Lateral Horizontal Well in the Sajaa Field, Sharjah, UAE
Authors: Mathes R. A. , Jack L. J.
Published: December 2007

Amoco Sharjah Oil Company (ASOC) has drilled several dual-lateral horizontal wells in its Sajaa Field since 1996. Two of the wells did not reach their geologic and leg length objectives due to massive, incurable lost circulation and several of the wells were hampered by differential sticking. A recently completed well was drilled using underbalanced techniques in order to mitigate or eliminate these occurrences. Dry sales gas from the Sajaa Gas Plant re-injection system was used to achieve the underbalanced condition. A 7" tieback casing string with perforations in the bottom joint was installed prior to drilling the horizontal legs and the gas was injected down the 7" × 9 5/8" annulus. Conventional mud motors and MWD tools were used in the bottom hole assemblies with the addition of a back pressure valve and a " restrictor" sub. Clean water with periodic high viscosity pills was pumped down the drill string. Surface equipment included a rotating blow out preventer (RBOP), a choke manifold with two bladder type adjustable chokes, sample catchers and a four-phase separator. The project was completed ahead of schedule, under budget, and without an accident or serious incident. The two main benefits were achieved plus some additional ones such as increased penetration rates and more efficient sidetracking. This paper discusses the pre-planning and team building conducted prior to beginning underbalanced operations, the surface and down hole equipment involved, the general procedures followed, plus the operating parameters and results experienced.
How To Manage Drill-In Fluid Composition To Minimize Fluid Losses During Drilling Operations
Authors: Cobianco S. , Bartosek M. , Lezzi A. , Guarneri A.
Published: December 2007

Selection of the best Drill-in Fluid for drilling horizontal wells is based, essentially, on the characteristics of the filter cake formed near wellbore region. Minimizing filtrate loss into the formation by forming a thin filter cake with low porosity and permeability is the key to managing formation damage problems.

In this paper the effects of Drill-In Fluids components and their interactions in the formation of a filter cake, which provides an effective caking process with reduced filtrate loss, have been evaluated. A statistically designed experiments carried out with a dynamic filterpress apparatus were used to identify which variables had the most significant effects on the filtrate loss and cake permeability, so that the optimum fluid composition could be determined. These variables include the formation characteristics (permeability and pressure values) as well as the type and amounts of the fluid components.

Data obtained in this experimental design study were analyzed using the multiple linear regression method (MLR) which allowed us to model the filtrate loss and cake permeability. The analysis pointed out that the most important factor is the type and the amount of polymer concentration, particularly an increased concentration of scleroglucan improved the cake permeability and the filtrate loss. An interaction effect between the amount of scleroglucan and the more crosslinked starch was also identified. Besides the results indicated that the other variables did not have any significant effect within the range of experimentation. This fact can be considered as an advantage, as it allows flexibility for the choice of the other factors when deemed appropriate in order to cost reduction.
An Innovative, Environmental Friendly And Cost Effective Approach For Polymer Based Mud System In Upper Assam Oil Fields Of India
Authors: Dayawant S.
Published: December 2007

Depleted reservoir pressures, problematic BCS section, frequent stuck-up formation damage and environment conditions in Upper Assam today, need Polymer based mud to improve the efficiency and effectiveness of drilling operations, to minimize formation damage and ensure maximum production from depleted reservoirs.

Conventionally polymer based mud is used in 8.5 " section against problematic BCS section and deeper producing horizons BMS, Kopili etc. The mud used in earlier phases is disposed off / thrown to the waste pit. Throwing / disposing of mud is a great problem in Upper Assam because of environmental constraints.

An innovative approach has been developed which is not only environment friendly but cost effective too. Lime flocculated and Low lime mud system were used previously to drill down Girujan clay and against (Tipam, BCS, and BMS) respectively.

Under the new approach. Bentonite content is gradually reduced and substantiated with Guar-Gum and XC-Polymer. Lime (Ca++ ions) have been replaced by K+ ions and KC1 flocculated mud system is run in place of Lime flocculated upto Girujan clay. 3 - 5 % KC1 is introduced during drilling Tipam sands to maintain the porosity and permeability intact. The system is fully converted into KCl-Polymcr system against BCS, BMS, and below having 2 - 3 % Bentonite, 3-5 % KC1, 0.1 - 0.2 % XC polymer, 0.2 - 0.3 % PHPA and 0.5 - 1.0 % PAC. Many wells in Gelekey, lakwa and RDS have been drilled successfully with this approach. Thus the approach will fulfill the objective of using polymer based mud without harming the environment.

Polymer base mud in Upper Assam project of ERBC is used because of the following reasons:
Custom-Blending Foamed Cement for Multiple Challenges
Authors: Kimura Kazufusa , Takase Koji , Griffith James. E , Gibson Ronald A. , Porter Dean S. , Becker Thomas E.
Published: December 2007

In some Middle Eastern wells, the serious problem of shallow casing leaks results from an insufficient cement seal across a corrosive water formation containing hydrogen sulfide (H2S). Factors contributing to this poor seal include multiple weak adjacent zones and thin lenticular washouts, which complicate conventional cementing practices by preventing slurries from sealing off water-bearing formations and protecting the well casings. Historically, multistage cementing has only marginally improved zonal isolation in this region. High-quality foamed slurries [slurries with high volumetric concentrations of nitrogen (N2)] can enable coverage of the weak zone, but these slurries are too permeable to provide long-term casing protection.

A joint study conducted to address casing-leak problems in a Middle Eastern field has yielded custom cement blends that mitigate the combined detrimental effects of (1) water containing H2S, (2) mud or whole-cement losses to lost-circulation zones (zones with very low fracture gradients), and (3) muddisplacement deficiencies primarily caused by multiple washed out sections. Successful slurries that appear (based on laboratory results) to combat these problems are foamed with nitrogen and feature a combination of Portland and pozzolan cements plus hollow pozzolan spheres. This paper discusses large-scale tests and the blends designed for these tests. Researchers conducted these tests in an attempt to prove the effectiveness of certain cement blends and to help optimize those blends. The tests show that foamed, lightweight (8 to 10 lbm/gal) slurries containing hollow pozzolan spheres with pozzolan cement can enhance the sealing of harsh-water zones. This enhancement is achieved by the combined effects of two events: (1) improving displacement of drilling mud and cuttings by optimizing foam quality, and (2) cementing past lost-circulation zones. Details of blends, test setups, and test results are discussed.
New Developments in the Mechanized Running of Tubulars
Authors: Harris David , Peyon Albert
Published: December 2007

With the advent of a new generation of ‘Super’ Drilling Rigs, including fifth generation Semi Submersibles, special needs have arisen for casing, tubing and drill pipe make up and running. This paper will describe the following new equipment developed for these rigs.

Power Frame

To run on rails similar to the Hydraulic Roughneck capable of suspending any Power Tongs to run casing and tubing in the range 3 ½-in. to 20-in. and drill pipe up to 6 5/8-in.

Mechanized Casing and Tubing Tongs

These tongs come complete with Free Floating Hydraulic Backups and remote operation capabilities.

Soft PLC Control Systems

Using software to simulate traditional PLC Systems and Profibus Communication Links for the remote operation of the Power Tongs and Power Tong Frames.

A plan for fully automated sequence has been implemented in the system.

Mechanized Drill Pipe Tongs

For the running of special drill pipe and Drill Pipe Test Risers.

Circulating Heads

Specially designed for remote operation and for use with new design side door elevators.

Special issues will be addressed, such as the running of casing in triples, a procedure not previously used in the industry. Anticollision systems for the equipment will also be discussed.

The systems described are unique in that not only will there be make-up equipment at the well center but also at two ‘Outboard Stations’ with mouseholes. By this means, many functions such as prefabrication of stands of risers, drill pipe and bottom hole assembly stands can be carried out offline without interrupting or delaying drilling operations. These functions will also include the fabrication and racking back of triples of casing. Considerable timesaving is anticipated.

The minimizing of any human intervention in these operations on the rig floor is critical to these new mechanized designs. Improvements in safety and operational efficiency are the key reasons for the development of this equipment. "Process driven design" and "Fit for purpose" are the two governing principles permanently followed in this project.
Evaluating High-Angle Wells with Advanced Production-Logging Technology
Authors: Hupp Douglas , Schnorr DeWayne R.
Published: December 2007

High-angle wells with longer and longer departures are being drilled at an ever-increasing pace on the North Slope of Alaska and around the world. This type well is used to penetrate new oil reservoirs and increase oil recovery in older maturing oil fields. The older maturing oil fields are being waterflooded with gas reinjection to maintain reservoir pressure, which results in wells that produce oil with high water cuts and high gas-oil ratios. These complex downhole production profiles create a difficult production logging environment.

A totally new logging tool is being used to determine the production profile when a high-angle well is producing oil with high water cut and high gas-oil ratios. This compact tool directly measures water holdup and gas holdup distribution around the wellbore, along with velocity data and X-Y caliper all 18 in. above the bottom of the tool. Pressure, temperature, inclination, with gamma ray and casing collar locator, are also included in this compact tool. All measurements can be run with an electric line unit or in memory mode. The memory mode eliminates the need for electric line when logging horizontal wells or wells that have high surface flowing pressures.

Sigma/porosity and carbon-oxygen measurements can be combined with this short production logging tool, when run on electric line, so that the production profile and the reservoir behind the casing can be evaluated on a single trip into the well. The combination of the production profile and formation evaluation is then used to determine how to produce the well and manage the reservoir to maximize oil production and recovery.

Production profiles from four different wells demonstrate the value of these direct measurements and how they were used in planning the remedial work to increase oil production and reduce or eliminate unwanted gas and water production.
Oriented Perforating for Sand Prevention
Authors: Sulbaran A. L. , Carbonell R. S. , López-de-Cárdenas J. E.
Published: December 2007

In weak formations or in competent formations with potential for sanding problems from high in-situ stresses, screens and gravel packs often are not practical or economical. However, in such formations, the perforating program can significantly affect the production of sand. With knowledge of the in-situ stress distribution around the target well, the technique of optimal phased and oriented perforating (OPOP) was applied in the Eocene sands of the field in Lake Maracaibo, Venezuela, to minimize sand production. Results were excellent. In this paper, the OPOP technique is described and general guidelines are given for its use. Field cases are presented that compare results gained using this technique to the performance of other wells in the same field.
An Optimal Foam Quality for Diversion in Matrix-Acidizing Projects
Authors: Alvarez Jose M. , Rivas Hercilio , Navarro Geidy
Published: December 2007

The proper placement of acid is a crucial factor in a matrixacidizing project. Unfortunately, much of the acid flows through the less-damage zones, leaving the damage area untreated. Foams have been used to divert the acid to the damage areas. However, the complexity of foam behavior in a porous media has reduced the efficiency of the diversion. Behenna1 claimed that if foam is generated or injected into the less-permeable layer (damage area), or if insufficient foam is injected into the more-permeable layer, diversion is not obtained. More recently, Alvarez et al.2 concluded based in a proposed model, the fg* model, that foam injection in the low-quality regime (low foam quality, fg) is better for acid diversion. They claimed that in this regime, more foam is injected into the higher-permeability layer before switching from foam to acid.

In this study experimental results confirming the implications of the fg* model are shown. Additionally, the experimental results suggest the existence of an optimum foam quality value for improving the efficiency of an acid-diversion work. Experiments were carried out in a composite core (parallel cores) having a permeability ratio of 15. The cores were packed with sand having different particle diameter to obtain the permeability contrast. An anionic surfactant was used in these experiments. Foam quality was evaluated from 95 percent to less than 40 percent. All the experiments were performed at 600 psi outlet pressure and room temperature. The gas used was nitrogen.

The existence of an optimum foam quality for acid diversion implies that matrix-acidizing projects should be designed carefully. Experimental work, such as the one performed in this study, and the fg* model may help to choose in advance the foam quality condition for a particular matrix-acidizing project obtaining a more cost-effective job.
Flowback Analysis of Acid Stimulation of Seawater Injection Wells: Case Histories
Authors: Taylor K. C. , Nasr-El-Din H. A.
Published: December 2007

Techniques were developed to evaluate acid stimulation treatments based on chemical analysis of the return fluids. Four acid stimulation treatments of seawater injection wells in a large carbonate reservoir in Saudi Arabia were studied in detail. Acid was bullheaded because surface washouts in the openhole section of the well did not permit the use of coiled tubing.

Each field treatment consisted of three stages. First, a pretreatment stage, driven by reservoir pressure, flushed out the wellbore. In the second stage the well was pickled to remove acid-soluble corrosion products and particulates from the wellbore. The third stage was a matrix acid stimulation of the formation. During each well treatment, more than fifty samples were collected and up to 700 chemical analyses were made on these samples.

The results provided information about formation damage mechanisms, the effectiveness of iron control additives, the volume of washout zones, the optimum flowback time, the relative amounts of carbonate minerals dissolved by the acid, and the dilution of the spent acid.

Confirmation of well damage mechanisms was obtained by analysis of dissolved and suspended solids produced during each stage of the treatment.

The amount and type of corrosion products (FeS, Fe3O4) in the wellbore were calculated from chemical analyses of the acid returns.

Results made it possible to reduce iron control chemical concentrations in the injected acid. This produced significant cost savings.

Density measurements of matrix acid flowback samples clearly identified the optimum flowback time of these treatments. The commonly used method of pH measurement does not show when all of the spent acid has returned from the formation.

Significant variations in treatment results were seen in seawater injection wells in the same formation. Iron-containing scale in the wells varied from mostly rust (Fe3O4) to primarily iron sulfide. The type of particulates present in the different stages of the treatment also differed among the wells examined.
Evolution of a Damaged Zone Caused by Water-Based Polymeric Drill-In Fluid
Authors: Queiroz João , dos Santos Renato L.
Published: December 2007

Open hole completion is, nowadays, the most used completion technique in horizontal wells. Many times, for operational reasons, such completions can take many days, sometimes months, to be executed. This problem leads to a questioning about what happens to the invaded area during such exposition to the drilling fluid.

To answer such question, an experimental study of invaded area aging was performed. Such procedure consisted in real-time CT-scan measurement of the invaded area by the water based polymeric drill-in fluid filtrate. The formulation used is very common at the Campos Basin, Brazil.

The tested samples were submitted to in situ conditions (pressure and temperature), during all the experiment time, which took about one year.

It was verified that the invaded filtrate area for this drill-in formulation increased about 40% in the first 34 hours, maintaining this level during the rest of the experiment. Besides, analysis done with a Scanning Electronic Microscope (SEM) in one of the tested samples, showed that the solids and salts from the drilling fluid were only present in the filtrate invaded area.
Technical/Economical Evaluation of Artificial Lift Systems for Eight Offshore Reservoirs
Authors: Ramírez Marcos , Zdenkovic Nick , Medina Edgardo
Published: December 2007

This paper elaborates the most appropriate AL (Artificial Lift) system for eight off shore reservoirs. First the initial screening was performed to eliminate some AL methods without deeper quantitative analysis. The remaining methods were then compared in terms of specific power (watts/Bopd) requirements. Finally the economical analysis was carried out to compare the AL systems in terms of curves showing NPV (Net Present Value) versus time. These curves were found to be very sensitive to the parameters that are usually not known with great certainty. For that reason the risk analysis was carried out to evaluate the probability of achieving the results from economical analysis.
Fractured Reservoirs: an Integrated Approach
Authors: Massonnat Gérard J. , Bockel-Rebelle Marie-Odile
Published: December 2007

The understanding of the flow network organization, and the ability to predict in 3D the distribution of fracture drains are hey points to enhancing well productivity, hydrocarbon recovery and therefore field productivity.

Recent advances in fractured reservoir characterization and modeling have led to construct and very sophisticated software able to model local 3D fractured networks and run one phase flow simulations on explicit fracture models.

The problem is how to take advantage of these advances and build more realistic 3D full field models to run multiple phase flow simulations.

This paper proposes and integrated approach assigning reservoir of flow properties using results from pluriscale and multi-disciplinary steps.

Its application on a case study largely contributed to a better understanding of flow behavior within reservoir.
Underbalanced Drilling Analysis of Naturally Fractured Mexican Fields through 2D Multiphase Flow
Authors: Cruz D. Velázquez , Rodríguez-Hernández H. , Cortes-Monroy I. , Azpeitia-Hernández D. , Blanco-Galan J.
Published: December 2007

Two-dimension multi-phase fluid flow numerical simulations which include drilling fluid, injected gas, formation fluids and cuttings were carried out for different well geometry taking into account both inlets and outlets throughout boundary system. Simulations were made for fields whose formation and fracture pressure profiles are characteristic of the naturally fractured Mexican fields. During simulations different gas injection systems to get underbalanced conditions such as parasite tubing string, annular gas injection and drill-pipe gas injection were proved in order to establish their feasibility for application in the case of study. Pressure and velocity fields together with phase distribution along the well are analyzed in each case to determine their technical and operative applicability as well as to evaluate advantages or disadvantages of this technique respect to the present circumstances during drilling. From the results it is possible affirm that drill-pipe gas injection is the best option to get underbalanced conditions during drilling as is explain in the extent work. A comparative survey against other model results (R.R. Angel, Machado-Ikoku, Poettmann & Berman and Okpöribi) is realized in the final of this work from which it is possible to observe the improvements of this work in regarding those of obtained by mentioned models. According to observed results underbalanced drilling is a good-available solution to total lost circulation and formation damage problems faced presently during drilling-wells in the naturally fractured low-pressure Mexican fields. The main contributions of this work consist of its capability to design drilling performance and quantify lost circulation by means of numerical simulation of volume-average general mass and momentum conservation equations.
Improved Zonal Isolation Through the Use of Sealants Before Primary Cementing Operations
Authors: East Loyd E. , McIntyre Kenneth W. , Tucker James , Covington Rick , Duell Alan
Published: December 2007

Zonal isolation in injection, geothermal, and producing wells is critical both to reservoir evaluation efforts and to operations, but often, cementing between the casing and the wellbore is still the only method of zonal isolation performed in many wells. Although zonal isolation and well diagnostics techniques have improved, primary cementing techniques may be inadequate for some reservoir conditions, resulting in undesirable water flows, gas flows, or both. If zonal isolation is inadequate, then expensive, often complicated remedial cementing work will be needed for improved well and reservoir performance.

If conformance technology is applied during the drilling phase, it can improve the performance of primary cementing processes, making them safe and economical. Conformance treatments seal problem intervals before primary cementing, thereby alleviating potential well-control problems. These treatments also help ensure successful primary cementing operations and prevent isolation loss caused by the casing expanding and contracting during production-pressure cycles. The formation itself, rather that the cement sheath alone, becomes the zonal isolation mechanism.

During the drilling phase, zonal isolation requires the use of coiled tubing, a hydrajetting device, a depth-correlation device, and a sealant. The sealant should be water-thin during placement, and should become an elastic polymer only after it is set in place. This zonal isolation technique requires an understanding of (1) depth correlation to openhole logs, through the use of mud-pulse technology, and (2) hydrajetting techniques that remove mud filter cake while placing the sealant. This paper presents examples of this technique for a 7 ⅞-in. wellbore and a 13 ½-in. wellbore.
Foaming Cement as a Deterrent to Compaction Damage in Deepwater Production
Authors: White J. , Moore S. , Miller M. , Faul R.
Published: December 2007

This case-history paper presents the results of a foam cementing process used during construction on four primary casing strings. The process was initiated to help prevent compaction damage associated with deepwater production.

Europa is a four-well, deepwater, subsea development project drilled in 3,500 ft of water at Mississippi Canyon, southeast of New Orleans, LA, in the Gulf of Mexico. Several issues related to effective primary cementing during well construction are addressed in this paper. Special spacer designs were also used because of the synthetic oil-based mud (SBM) used on two of the casing strings, which included production liners.

The main focus of the paper is on the planning, preparation, and execution of the primary cementing on the critical production liner. Because of the highly unconsolidated formations above the producing zone, the reservoir will experience compaction caused by depletion. The critical issues for the production liner are proper casing design, effective cement placement, and mechanical properties needed to help resist the forces imposed on the wellbore and cement sheath. Minimizing the effects of these forces caused by transverse loading helps to prevent the casing from buckling. The unique properties of foamed cement make it best suited for this application.
Casing Centralization in Horizontal and Highly Inclined Wellbores
Authors: Blanco A. , Ciccola V. , Limongi E.
Published: December 2007

Success of primary cementation is highly improved by use of centralizers. They are fixed along the casing or liner to keep it away from borehole walls. To be effective use, the placement of centralizers with respect to spacing and location must be optimized through consideration and evaluation of all parameters and forces involved. At present, all models have been developed to evaluate the casing deflection based on lateral an axial loading. However, some approximations made in the estimation of axial load, leading to standoff values that can be very different from actually expected. The present study demonstrates that a more realistic determination of axial load is achieved by applying a new method, when considering, in a more realistic way, the effects due to fluid forces. In API model, the effect of fluid action is limited to the buoyancy forces on the casing. In this paper a model is presented, in which fluid effect is evaluated in a global way, integrating both buoyancy effect and horizontal force component acting on the casing. Also, corrections are made to estimate casing deflection caused by compression. The results obtained using the new model vary significantly from API-10D, especially in highly inclined and horizontal wellbores.
The Evolution and Application of Formate Brines in High-Temperature/High-Pressure Operations
Authors: Bungert D. , Maikranz S. , Sundermann R. , Downs J. , Benton W. , Dick M. A.
Published: December 2007

High-density formate brine-based drilling fluid systems have emerged as viable reservoir drilling and completion fluid options for deep high-temperature wells. Upon their commercialization in the early 1990's, these systems were shown to possess a unique combination of properties that could be exploited to engineer high-density fluids that would comprise minimal solids, maintain rheological stability at high temperatures, minimize reservoir damage and satisfy environmental requirements.

This paper describes the evolution of these systems and their recent application in the drilling of deep wells in Northern Germany and other areas. Not only did the formate-based systems exhibit faster penetration rates than the water-based fluids used previously; they also eliminated the solids sag problems experienced with water-based drilling fluids used in technically and economically demanding high-temperature environments. Furthermore, the formate brine-based systems were shown to improve well productivity.

Through an examination of 15 deep gas wells in Germany and other formate-based applications, the authors review the performance of formate brines as reservoir drilling, completion and workover fluids. Particular attention is given to drilling and eventual well performance, as compared to offset wells drilled and/or completed with alternative systems.
Development of an Open Hole Sidetracking System
Authors: Stokley C. O. "Doc" , Seale Rocky
Published: December 2007

Sidetracking in an open hole environment has been accomplished for many years using time drilling techniques, cement plugs, and permanent whipstocks. However, problems have been identified in certain applications that warrant alternative sidetracking methods or techniques. For example, in time drilling applications, harder formations can prevent the lateral hole from being initiated, and softer formations may allow ghost holes to develop. Each condition is time consuming and costly.

To address these problems, an open hole retrievable sidetracking system was developed and tested. Design considerations revolved around anchoring and retrieving in the open hole, while maintaining integrity through the drilling process. The iterative steps taken for this design project are covered in detail.
Well Control in Campos Basin - Brazil
Authors: Martins F. S. B. , Santos O. L. A. , de Paula I. L.
Published: December 2007

This article presents the actions taken in Campos Basin, offshore Brazil, in order to make drilling, completion and workover operations safer, especially in deep waters. Firstly, the paper describes the pioneer work called Safety Program for Dynamic Positioning Vessels (DPPS) in terms of well control that has been implementing in Brazil since 1993. This program consists of operational procedures, equipment requirements and practical recommendations for well control in deepwater locations. The paper also shows the current status of the program implementation and the benefits and good results associated with its application in Campos Basin.

Afterwards, the paper presents the structure and the most important aspects of the Blowout Contingency Plan for Campos Basin. The management structure to be established and the responsibilities and assignments of each person involved in a deepwater blowout and during its killing operations are listed. Also are presented the operational aspects related to the three phases of the blowout control operations: immediate actions, blowout containment procedures and blowout control.

Next, the paper presents the huge effort that has been developing in Campos Basin in order to train and certify in well control all personnel directly involved in drilling, completion and workover operations. The paper shows the criteria, statistics and control items of the well control certification system currently in use in Campos Basin. The kick detection and well shut-in drills to be implemented on the rig are also presented and discussed in the paper.

Finally, an analysis of the rig downtime due to BOP repair in the Campos Basin is presented.
Foam Propagation in the Absence and Presence of Oil
Authors: Vassenden F. , Holt T. , Moen A. , Ghaderi A.
Published: December 2007

Foam propagation in co-injection was studied in a 10 m long porous medium, equipped with pressure ports for every 1 m. The porous medium had been characterized by flooding experiments on the core scale. In the absence of oil, propagation on the 10 m scale could be understood by corescale, steady-state foam properties. In the presence of oil, however, the foam front propagated significantly slower than the injected fluid front. An extraction mechanism for oil combined with foam oil sensitivity can explain the delayed propagation. These effects were included in a foam simulator that reproduced the slow foam propagation.
Simulating Foam Processes at High and Low Foam Qualities
Authors: Cheng L. , Reme A. B. , Shan D. , Coombe D. A. , Rossen W. R.
Published: December 2007

Foams used for gas or acid diversion exhibit two flow regimes, depending on foam quality. Two foam simulators, one the most widely used commercial foam simulator and the other developed at our university, fit steady-state foam behavior in both regimes. A simple procedure is described for fitting simulator parameters to a set of steady-state coreflood data and examples are shown. Fitting model parameters to a single coreflood data can err by fitting this datum to the wrong flow regime.

Shear-thinning reported in the "low-quality regime" can increase foam injectivity in radial flow. Foams in low-quality regime fit the same correlation for overcoming gravity override previously derived for foam in the high-quality regime. The flow regime does greatly affect the effect of capillary crossflow on foam diversion between layers differing in permeability, however. Capillary crossflow harms diversion between adjacent layers, as found earlier, but the magnitude of the effect is much less for foam in the low-quality regime, and no single correlation matches all the results. Capillary crossflow can actually increase (by a small amount) diversion from adjacent layers differing somewhat in permeability to distant layers with much-different permeability.
An Improved Three Phase Flow Model Incorporating Compositional Variance
Authors: Fayers F. J. , Foakes A. P. , Lin C. Y. , Puckett D. A.
Published: December 2007

A consistent set of procedures for calculating 3 phase relative permeabilities (3PRPs) and the capillary pressures (3PCPs), referred to as the rescaled Interpolation Method (RIM), is described. The intention is to provide an approach for mixed-wet systems which is compatible with the likely availability of immiscible 2P measured data, which honours the basic physics of 3P displacement processes, and at the same time avoids undue complexity in the simulator and excessive overheads in computing efficiency. For 3PRPs the starting point rests on the use of the Baker saturation weighted interpolation method for the three phases, but modified for the oil phase through saturation rescaling to give compatibility with a general form for the residual saturation function Som(Sg, Sw). Comparisons with experimental data show the benefits of this approach as opposed to Stone's I. A practical procedure for including 3P hysteresis is described. This is then extended to allow for compositional changes in the oil and gas phases, including the limiting miscibility conditions. The model for 3PCPs is based on simple assumptions concerning the division of the pore space between water-wet and oil-wet pores and comparing this with the phase occupancies of pores in the corresponding 2PCP-measurements. The mixed-wet pore space division is found from the cross over saturation in the water/oil 2PCP.