bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbonate Matrix Acidizing Fluids at High Temperatures: Acetic Acid, Chelating Agents or Long-Chained Carboxylic Acids?
Authors: Huang Tianping , McElfresh Paul M. , Gabrysch Allen D.
Published: December 2007

Matrix acidizing of carbonate formations has been carried out for many years using HCl acid in various strengths. However, in some high temperature applications, HCl does not produce acceptable stimulation results due to lack of penetration or surface reactions. Organic acids, like formic acid and acetic acid, were introduced to offer a slower reacting a thus deeper stimulating acid. These "retarded" acids also had short- comings due to solubility limitations of acetate or formate salts. In recent years, several alternatives have been developed, including aminocarboxylic acids and long-chained carboxylic acids. These long-chained carboxylic acids offer low corrosion rates, good dissolving power at high temperature, high biodegradability,and easier and safer to handle.

Many experimental and theoretical studies in carbonate acidizing have confirmed the existence of an optimal acid injection rate at which major wormholes are formed, and the benefit from stimulation is maximized. This optimal rate depends on reservoir conditions, rock properties and chemical reaction rate of the acid being used. In our previous study, a theoretical model showed that under the same conditions, the optimal injection rate for weaker acids is lower than that for stronger acids. This paper presents a comparison of the efficiency of stimulation in carbonate acidizing of three different kinds of high temperature stimulation fluids. A chelating agent, EDTA, acetic acid, and a mixture of long-chained carboxylic acids were used to acidize carbonate cores at high temperatures. The effectiveness of the process and the optimal injection rate were studied by measuring the acid volume needed to propagate wormholes through 4-inch cores. The dendritic nature of the acid penetration was also determined by making castings of the wormhole structures after acidizing. The experimental results from this study showed that the optimal injection rate of long-chained carboxylic acids is lower than that for acetic acid and the EDTA. This increase in efficiency then determines that a deeper and more efficient stimulation per gallon of acid mixture used is obtained with the long-chained carboxylic acids.
Field Validation of a Carbonate Matrix Acidizing Model: A Case Study of Seawater Injection Wells in Saudi Arabia
Authors: Thomas R. L. , Nasr-El-Din H. A.
Published: December 2007

Although hydrochloric acid has been used for more than 60 years to matrix acidize carbonate reservoirs, the process is still as much art as science. Historically, design engineers have used a "rule-of-thumb" based on field experience to quantify the design parameters for a candidate well. However, each well is different and this "generic" approach for treatment design can result in under- or over-treating. This paper is directed at matrix acidizing of vertical water injection wells completed in a heterogeneous carbonate reservoir (Arab-D) in Saudi Arabia with focus on field validation of a commercial matrix acidizing design simulator. The "validation" process allows the production engineer to "calibrate" the simulator for his specific field, and use it with confidence to improve treatment designs.

In this field study three matrix-acidized injection wells were used for validation of the carbonate acidizing model. The wells were completed in 150 to 200 feet openhole intervals in a reservoir composed of a variety of limestone - dolomite mixtures. Treatments were performed using hydrochloric acid along with particulate diverter stages, which was bullheaded down casing. The post-treatment model validation process consisted of simulation of the actual treatment using various values of "acidizing efficiency" to yield an acceptable match with the final skin. Subsequently, a comparison of the simulated and actual surface treating pressure, and the prepost-treatment wellhead pressure during seawater injection was made. A detailed description of the validation process and the supporting well data are presented.

A good match of predicted surface pressure and actual wellhead pressure obtained from the treating report adds credibility to the simulator. Normally, the difference in actual and simulated pressure was less than 10%. Pressure data indicate that the benzoic acid/rock salt diverter systems were inefficient. The simulator indicates diverter inefficiency causes the high permeability zones to become "thief zones" resulting in non-uniform acid distribution. In all cases the pressure dropped 25 to 50% within ten minutes following injection of acid into the formation. An internal acidizing efficiency factor was increased to allow the predicted skin of the simulator to approximate the actual skin determined from a falloff test. It was discovered that the optimum efficiency factor was a function of the amount of dolomite in the reservoir. Guidelines for the determination of the efficiency factor based upon mineralogy are presented along with an explanation for this and other observations.
On the Rheological Mechanisms Governing Drill-in Fluid Invasion into Reservoir Rocks
Authors: Martins A. L. , Massarani G. , Waldmann A. T. A. , Costa F. G.
Published: December 2007

This article deals with the comprehension of the rheological mechanisms relevant to drill in fluid invasion through reservoir rocks, aiming the design of a solids free non-invasive fluid. The strategy to develop this concept was to flow different kinds of fluids (Newtonian and different polymeric solutions) through consolidated inert porous media. Experimental results indicate that Newtonian fluids, CMC solutions and low concentration XC and PHPA solutions were properly fit by Darcy law. On the other hand, the highly concentrated solution presented relevant deviations. Such deviations tended to increase with the increase of deformation rate (or differential pressure). This fact indicates that there is a need for applying viscoelastic constitutive models to account for the extra friction losses. An expression for resistive force estimation as function of the first normal stress difference correlated properly with the experimental results.
Improving Performance of Low Density Drill in Fluids with Hollow Glass Spheres
Authors: Chen Guoqiang , Burnett David
Published: December 2007

The increasing number of open hole horizontal well completions in low-pressure and depleted reservoirs requires the use of non-damaging low-density drill-in fluids (LDDIF) to avoid formation damage and realize optimum well productivity. To address this need we have formulated new LDDIFs with specific density lower than 1.0 sg (8.34 ppg) specifically to drill and complete low pressure and depleted reservoirs with minimum formation damage and maximum production. These materials exhibit typical drilling fluid characteristics, allowing the well to be safely drilled to required well depth, but also perform as completion fluids, lessening formation damage to a greater extent than fluids with greater density and higher wellbore pressures.

The new LDDIF incorporates low-density hollow glass spheres (HGS) to allow near-balanced drilling in low pressure and depleted reservoirs. The LDDIF uses potassium chloride (KCl) brine as the base fluid because of its low density and inhibition of clay hydration and employs low concentrations of the HGS so that fluid rheology is not altered.

We have conducted extensive laboratory testing to compare performance of the HGS LDDIF with that of conventional horizontal well DIFs. Experiments consisted of permeability regain tests on unconsolidated sands with sand control screens. Test variables included temperature, concentration of drill solids, cleanup technique and HGS concentration. Test results have shown that the new fluids are up to 50% easier to remove from the wellbore formation faces and provide higher productivity than higher density fluids. Such results indicate that higher well productivity from wells with less impairment would offset any added costs of HGS additives in the fluids.
Successful Application of Mud Cake Pop-Off Technique in Horizontal Well Bore Cleanup - Case Histories
Authors: Abiodun Afolabi , Nwabueze Vincent , Opusunju Austa , Sibigem Francis
Published: December 2007

Early return on investment, high productivity indexes, late water/gas breakthrough and tight reservoir oil recovery are among the benefits of horizontal well over vertical well. Many operators have perfected and standardized the drilling and completion procedures of horizontal wells, however, the results of the different drain hole cleanup approaches have been inconsistent (especially where oil or pseudo-oil base mud were used during drain hole drilling).

Conventionally, the removal of the damage caused by drilling mud filter cakes and filtrate is achieved with the aid of acid cleanup, Nitrogen lifting or brine wash. While the results of enzymes or acid cleanup in water based mud filter cakes removals are encouraging, the results in oil or pseudo-oil base filter cakes have been considerably inconsistent.

This paper details the Pop-Off approach to the removal of drilling fluid damage and filter cake in horizontal wells with high heterogeneous permeability profiles. The paper described how the application of filter cake flow initiation pressure combined with treated drill-in fluid base fluid and reservoir's fluid solvent and dispersion power have delivered superior and consistent value on investment. The results from the application of this method showed remarkably low drawdowns and high productivity indexes. Field data resulting from this method demonstrates a history of 100% technical and economical success with more than 150% improvement in recovery and projected productivity index. In addition, there has been consistent improvement in sustenance of well productivity with wells treated with Pop-Off method over wells treated with previously applied conventional methods of filter cake removal.
An Alternative Drill-in Fluid System for Low-Pressure Reservoirs
Authors: Quintero Lirio , Jones Tom A.
Published: December 2007

The majority of wells drilled with water-based fluid systems in pressure-depleted reservoirs are subjected to high overbalance pressures due to drilling fluid densities greater than the density of water. These overbalanced conditions are directly related to loss of circulation, stuck pipe and especially, formation damage due to solids and fluid invasion. Specialized technologies, such as under-balanced drilling with ultra-low density foams or aerated fluids, have been used to resolve most of the aforementioned problems1, 2 High application costs, however, have made these alternative systems almost prohibitive in many mature fields.

With appropriate surfactant and polymer selection and the implementation of unique bridging methods, drill-in fluids may be designed with highly thixotropic behavior, minimal filtration properties, excellent crude-oil compatibilities and high return permeability. This paper presents the development of a low-density water-based drill-in fluid stabilized by a specially selected polymer-surfactant complex and bridging materials designed specifically for low pressured sandstone and carbonate reservoirs.
Drilling, Producing and Treating Complex Wells. A Collection of New Technologies to Optimise the Overal Well Process
Authors: Charlez Ph. A.
Published: December 2007

This paper highlights the concept of complex well through various advanced or emerging technologies involved during the well life process. The current state of the art states that drilling technology is more mature than production and treatment technologies.

The well life process is divided into four phases: pre-project, conception, realisation and exploitation. Each phase is studied in terms of productivity on one side, cost on the other. New concepts such as limitation of well oversizing or anticipation of field maturity are regarded through actual examples. It is finally concluded that this technical revolution can only be a success if culture and human organisation evolve at the same rythm. Well being the most transverse object of the E&P chain, it represents a fantastic opportunity for all disciplines to work in close collaboration within integrated teams and not anymore through conventional isolated petroleum professions.
Representative Laboratory Testing Procedures for Selecting Drilling Fluids
Authors: Watson R. B. , Nelson A. C.
Published: December 2007

Due to an increased understanding of the effects of formation damage, it has become commonplace to test the damage potential of drilling fluids with reservoir core, prior to drilling. This preventive approach has shown to be more effective than neglecting pre-drilling laboratory testing. However, the current approaches are lacking in many areas.

Through research, as part of an E.U. funded project, well productivity 2002, a standard procedure for testing the formation damage of drilling fluids has been developed. The research provides a number of explanations as to why previous "round robin" studies display large variations in results between laboratories. False ranking of drilling fluids and formations were subsequently produced due to the varied procedures currently used. Explanations and solutions are specified in order to allow future testing to be repeatable in any laboratory and most importantly, representative of the wellbore situation.

The result of the research is a cost-effective procedure, which can be scaled to the reservoir after testing. Although the laboratory equipment used is not greatly different from that used in many laboratories, there are procedural changes. These changes allow accurate testing and ranking of formation damage potential. The results detail representative fluid application, basic fluid ranking procedures and a more advanced investigative procedure, which determines type and extent of damage expected from the formation and fluids. Additions to these procedures allow for the testing of solid and chemical completions, to provide a strong tool for well planning.

The research was part of Work Package 1 of the E.U. project "Well Productivity 2002" and the recommended methods are already being used in a number of reservoir studies. It is intended to present future work using these methods, in parallel with well data.
Beyond Acidizing and Fracturing
Authors: Tambini Mauro
Published: December 2007

The oil industry is still focusing on the optimization of hydrocarbon production with the minimum cost possible in complete HSE respect.

Nowadays a continuous flow of innovative ideas generates worldwide new technological frontiers. As a result, we witness remarkable applications of new well solutions and techniques. In this scenario we would like to give an overview of the possible answers to the technological needs and actions towards Stimulation Treatments and Formation Damage Removal.

The main issues to investigate are: if the mature and worldwide applied techniques of Acidizing and Fracturing are still adequate to the new well geometry scenarioif the "novel" technologies are well known and cost effectiveif innovative ideas on formation stimulation and damage removal are to be better investigated and implemented.
Mitigation of Naturally Occurring Oil Seeps and Methane at the Olinda Ranch Residential Development, Brea-Olinda Oil Field
Authors: St. Peters Kay
Published: December 2007

Mass grading of a hillside residential project within the Brea-Olinda oil field in southern California provided an opportunity to mitigate the naturally occurring oil and gas seeps at the site during the grading process. Multiple strategies, such as subsurface collection and venting systems, were used to reduce the potential for oil seeps to form in graded lots, and to prevent hazardous accumulations of methane gas in homes. Monitoring of the systems will be conducted by an environmental consultant in accordance with maintenance manuals prepared for the project.
Urban Development of Oil Fields in the LA Basin Area, 1983 to 2001
Authors: Gamache M. T. , Frost P. L.
Published: December 2007

Since 1983, construction-site projects in the Los Angeles Basin area have been reviewed under the Construction-Site Plan Review Program of the Department of Conservation’s Division of Oil, Gas, and Geothermal Resources. Under its auspices and before issuing building permits, local permitting agencies review and implement the division’s pre-construction, oil-well recommendations and requirements.

Oil-well proximity to proposed structures statistics derived from division data suggest there are three types of urbanized oil fields in the Los Angeles Basin area. This information may prove valuable to anyone involved in oilfield land development.
Rose Field: A McLure Shale, Monterey Formation Development Story
Authors: Ganong Barbara L. , Hansen Chris , Connolly Paul , Barree Bob
Published: December 2007

Following the development of successful McLure production in the North Shafter Field, the newly designated Rose Field was explored and developed. With an analogous model six miles to the south, well performance seemed predictable in the Rose Field. However, results suggested differences requiring explanation. The core data, tiltmeters and post-frac analysis indicated the limiting factor was reservoir quality, suggesting that project viability required significant cost pruning.

This case study discusses the revelations and processes implemented in discovering the new pool and its development as a horizontal, hydraulically-fractured McLure Shale play. Producing oil ranging from 22 to 26 degrees API through a low permeability, over-pressured zone presented its own share of engineering challenges from drilling to completion and through operation. In this first paper, the primary discussion revolves around identifying the analogous zone north of the North Shafter Field, in what has become the Rose Field and understanding the differences between the new field and its nearest analog, allowing for improved engineering practice.
Boon or Bane? A Survey of the First 10 Years of Modern Multilateral Wells
Authors: Oberkircher Jim , Smith Ray , Thackwray Ian
Published: December 2007

Since their introduction in 1993 the modern multilateral systems and their applications have developed rapidly. System capabilities and features have adapted to a myriad of operating conditions and demands placed upon them. But in many cases the development of equipment has outstripped the industry's ability or willingness to adapt it. There are two main reasons:

Reliability: Despite high technical and economic success rates in a wide range of applications the common perception of multilateral technology is that it is "risky". However industry-wide statistics show that Multilateral Technology (MLT) is not the high-risk technology it is often perceived to be.

Value: Even the Operators most experienced in multilateral technology struggle at times with identifying and quantifying the true value and return on investment of these wells. It is understandable there is some uncertainty when assessing the true economics of this type of well. One issue with this is the inability to perform effective modeling and prediction of well performance and lateral contribution. A second is the expense to provide equipment to actually monitor the production from additional laterals.

Tangible (or Intangible) Rewards vs. Perceived Risks. This paper will examine these arguments using industry data and information and by examining actual multilateral case histories from the first 10 years of multilateral developments. This paper will also take a look at the future of this technology and discuss what may happen in the next 10 years.
Application of Large Thermal Sector Models in a Field Performance Optimization Study of a Mature, Heavy Oil Field
Authors: Márquez L. , Hurtado J. , Wang J. , Iwere F. , Gomez E. , Hudgens P. , Ponce E. , Bashbush J. L. , Gurpinar O. , Aly A.
Published: December 2007

The results of a reservoir performance evaluation of a giant mature heavy oil field are presented here. This field began production in 1927. By 2002, cumulative production had surpassed half a billion barrels of low-gravity oil from Miocene sandstone formations produced under natural depletion, water and gas injection, and cyclic steam injection from more than 400 wells. As a result, several interdependent flow models including black-oil full-field, thermal single-well, and thermal large-sector models were built for field analysis and optimization. The long and complex production history, as well as the various recovery mechanisms, presented a number of challenges in constructing and calibrating the models to past historical performance.

The optimization work was done in the following three stages. First, a coarse-grid black-oil model was constructed to study the field performance prior to steam injection, following the successful geological modeling phase of this project (presented in Márquez et al., 20011). The second stage involved single-well and sector-model thermal simulation analysis. The thermal models were used to match the field historical pressure and production data over the natural depletion, water injection and cyclic steam injection periods. Third, we investigated the field performance under different development scenarios. Optimization results with the singlewell thermal models were incorporated into the sector models, which were used for processing runs to examine infill drilling; recompletion of active wells; waterflooding; huff ‘n’ puff steam injection; steam drive; and horizontal well drilling.

The project resulted in the identification of more than 100 infill or recompletion candidates, and an estimated three million barrels of oil (MMBO) of additional recovery during the first 2 years of this project. As a result there were significant performance improvements and more are anticipated through the implementation of the field development strategies recommended here. The modeling approach led to significant time savings and provided an effective reservoir management tool for future field development.
Methanol Losses to the Hydrocarbon Phases in Offshore Pipelines and its Effect on Economics
Authors: Bruinsma D. F. M. , Notz P. K. , Desens J. T. , Sloan E. D.
Published: December 2007

Methanol is the most commonly used hydrate inhibitor in offshore pipelines. The amount of methanol that is lost to the hydrocarbon phases and the implications that this has on the flow assurance strategy and the economics of offshore developments are presented. Methanol losses to the hydrocarbon phases are greatest in pipelines with small amounts of water. For cases of high methanol losses, nonvolatile or thermal inhibition methods may be more economical. The importance of accurate predictions of methanol losses is discussed along with the need for experimental data. An experimental technique for measuring methanol partitioning between aqueous and hydrocarbon phases is discussed. Comparisons between predictions and data are made for methanol partitioning between aqueous and hydrocarbon phases of live fluids.
Scarab/Saffon Subsea System: Design and Installation Aspects
Authors: Ellaithy Wael F , Gaber Mohamed , Gomaa Adel , Vermeulen Ed
Published: December 2007

The Scarab/Saffron field development is the first deepwater field in the Mediterranean. To present day standards the water depth at the field location is not extreme and the pipeline system can be installed by "conventional" methods. The total system comprises a large number of components, such as two large diameter export lines, a large PLEM, two manifolds, eight 10"in-field flow lines, umbilicals and their termination units, flying leads etc. However, the design and installation presented some other challenges to the project team and the Contractors. The system is installed in an area that is seismically active and has a number of highly unusual seabed features. Seismic aspects played an important role in the layout of the system and in the design of some of the foundations of the equipment. Up to now few fields have been designed in seismically active areas and novel techniques were used to the design of some of the components. The challenges are in the variations in water-depth, (0 to 650 meters), in pipeline diameter ( 4 inch to 36 inch) and the different types of umbilicals. No single marine vessel can perform all the installation activities for such a wide range of pipeline sizes and sub sea system components. Flat bottom derrick / lay barges, a semi-submersible installation vessel, a small diameter pipeline installation vessel and other marine construction installation vessels were employed to perform the installation activities of the Scarab / Saffron field development. The planning of the fabrication, delivery, testing, installation and commissioning in a relatively short time presented a major challenge to everybody working on the project. This paper presents details of the pipeline system and the considerations that led to the field layout. Methods of installation and vessels used are described as well as captured lessons learnt.
Geostatistical Prediction of Sand Distribution of Gas Reservoir in Jilin, China
Authors: Qiu Li-Wei , Yang AnPing , Long Sheng-Xiang , Kang Zhi-Jiang
Published: December 2007

This case study involves sand distribution prediction for the Gujiazhi and Houwujiahu gas fields in Jilin Province, China. Initial data analysis involved correcting and calibrating the well logs. Log data from 74 wells were available from the Gujiazhi field and the Houwujiahu field. This initial process also established 3-D porosity, permeability and clay volume models for each field. The Gujiazhi grid has a cell dimension of 100×100×2 meter, Houwujiahu grid 100×100×1 meter.

Geostatistical inversion was conducted for a 3-D seismic volume covering both fields. Synthetic resistivity logs were generated and converted to pseudo-impedance in time, the derived reflectivity was convolved with a wavelet, and the synthetic seismogram correlated with actual seismic traces. This process was allowed to iterate until a satisfactory correlation was reached. One VSP was used for the initial time-depth conversion, and the time-depth relationship for each well was subsequently time-adjusted until the synthetic seismograms matched the actual seismic, allowing a reasonable lateral velocity variation. A common wavelet was extracted for all the wells. With the optimized time-depth control and common wavelet, resistivity inversion was conducted for the 3-D seismic grid. A 3-D reservoir geology model was generated by co-kriging, using the well log data as hard data and the inverted seismic data as soft data.

The 3-D reservoir geology model from well logs showed high vertical resolution but poor lateral resolution, while the 3-D seismic-inverted model showed higher lateral resolution but poor vertical resolution. The co-kriging model showed favorable resolution both vertically and laterally. The resulting reservoir geology model provided insights into assessing the distribution of pay sands. Since in this area, resistivity is a good indicator of lithology, the study results demonstrate that geostatistical inversion of seismic data to resistivity is useful in predicting sand distribution, and for optimizing future drilling locations.
Two-Phase Helico Axial Turbines
Authors: Charron Yves , Acloque Elise , Stihlé Sylvain
Published: December 2007

Following the development of two phase helico axial pumps in the seventies a R&D program has recently been launched by IFP and DBGP for the development of two phase helico axial turbines. These turbines may be used in many process applications in replacement of let down valves for energy recovery but also to increase the cooling duty or the liquid production. They may also be used in systems including a two phase separator with single phase turbines or valves at its outlets in view of reducing the number of equipment, space and weight. These turbines, suitable for all gas fractions, may find applications in the hydrocarbon upstream field (HP/HT wells, fractured reservoirs, oil stabilisation, electricity production in remote areas) or in the hydrocarbon downstream field (refrigeration cycles, LNG, gas drying, solvent regeneration or hydrotreatment units). This wide potential field of applications requires helico axial turbines to be suitable for a broad range in flow rate, pressure, temperature and gas fraction. This has several consequences on the pump design, particularly, regarding the mass transfer occurring during the pressure let down and the volume change across a turbine or a hydraulic stage. A two phase helico axial turbine prototype will be tested, in single and two phase flows, during the second half of 2003 to confirm the expected hydraulic performance.
Fixed Depth of Investigation Log for LWD Resistivity Tool
Authors: Bittar M. S. , Hu G. , Xiao J.
Published: December 2007

For years, wireline array-induction resistivity data have been processed and displayed at fixed multiple depths of investigation on logs. Modern multi-frequency, multi-spacing logging-while-drilling (LWD) resistivity tools are capable of measuring resistivities at multiple radial depths of investigation. However, since wireline and LWD tools are governed by different tool physics, it is sometimes difficult to compare data obtained by these two devices. Therefore, it is desirable to deliver LWD resistivity data in a manner that is comparable to the presentation of wireline array-induction data.

This paper presents a new approach to process and display LWD data at fixed depths of investigation. This approach starts with a non-linear, iterative deconvolution to simultaneously correct for both relative dip and shoulder-bed effects. Using these corrected logs, the formation resistivity and invaded zone resistivity are determined by an inversion technique that assumes a step-invasion profile. This enables the method to better address the non-linearity of the LWD tool's response. After that, a least-squares curve-fitting technique is used to derive a function that models the relationship between the physical spacing of the transmitter-to-receiver pair and the depth of investigation. Using the same technique, a second function, which models the relationship between the transmitter-to-receiver spacing and the resistivity reading is derived. The first function is utilized to determine a set of fictional spacings that, if used, would result in the desired fixed depths of investigation. These fictional spacings are then used with the second function to calculate resistivity values at the desired depths of investigation, which are chosen to match some of those typically used for wireline array induction tools. The processed data thus obtained provide a meaningful way of comparing array induction and LWD resistivity data.
Field Application of Unconventional Foam Technology: Extension of Liquid CO2 Technology
Authors: Gupta D. V. S.
Published: December 2007

Liquid CO2-based systems have been pumped as fracturing fluids in North America since the early 1980s and liquid CO2/N2 system from 1994. The fluids have been used in more than 1000 wells in a variety of formations having permeability values from 0.1mD to 10 Darcies, depths in excess of 3000 m and bottom-hole temperataure (BHT) from 10 to 110 °C. The chemistry and physics of these fluids are intriguing and have been described before. Several attempts to increase the viscosity of liquid CO2 have been tried with little success. Here, a novel fluid is described that retains all the nondamaging aspects of liquid CO2 but with increased viscosity. This fluid is a foam of nitrogen in liquid CO2. It uses a CO2-soluble foamer that does not damage the formation and can be released into atmosphere without damaging the environment. The fluid does not include any other liquids, such as water, alcohol or hydrocarbons. The foam thus formed follows conventional foam physics (with respect to viscosity increase as a function of internal phase volume, etc.). Due to the limited amount of liquid CO2 used (around 20-25 volume% for a foam of internal quality of 75-80%), multiple jobs can be conducted on a single day making the system more cost-effective than the typical liquid CO2 fracturing system. A summary of the field use for shallow gas applications in Canada is described.
Acid Fracturing of a Gas Carbonate Reservoir: The Impact of Acid Type and Lithology on Fracture Half Length and Width
Authors: Bartko K. M. , Nasr-El-Din H. A. , Rahim Z. , Al-Muntasheri G. A.
Published: December 2007

The Khuff formation is ideally made-up for acid fracturing because of the heterogeneous nature of the formation, which tends to support the created fracture conductivity. Various acid types were used to fracture this tight dolomitized formation including: 28 wt% regular HCl, emulsified acid, and in-situ gelled acid. In addition, several wells were fractured using 15 wt% HCl/9wt% formic gelled acids. However, based on production results and the large database of acid fracture treatments (more than 70 wells); it appears that there is a correlation between the acid type used and the lithology of the formation. An earlier study,1 which briefly examined this phenomenon, indicated that the emulsified acid might be more suited to low permeable zones. These low permeable rocks are predominately made up of limestone.

Typically, changing the acid volumes, placement techniques, or pumping rates, has optimized acid fracture treatments by creating longer and wider fractures. However, we tend to ignore the effect of lithology in carbonate formations because we all believe that the rock interaction with the acid is not as sensitive as in sandstone formations. With this large database of acid fracture treatments, acid rock interactions were investigated to determine the relationship between lithology and acid type.

This work involves correlating the designed treatment to the open-hole logs, core petro-physical data, analysis of hundreds of samples collected following acid fracture treatments, and production results.
Impact of Transient Flow Conditions on Electric Submersible Pumps in Sinusoidal Well Profiles: A Case Study
Authors: Noonan S. G. , Kendrick M. A. , Matthews P. N. , Sebastiao N. , Ayling I. , Wilson B. L.
Published: December 2007

ChevronTexaco has 13 wells producing offshore Africa via electric submersible pumps (ESPs) that experienced problems primarily due to the transient nature of the multiphase inflow through the sinusoidal well profiles. A study completed in 2002 used a transient multiphase simulator to model the sinusoidal sections of each producer and calculate the conditions that the ESPs could see over the life of the well for various drawdown conditions and speeds. This paper will focus on how the results from the simulator were validated and used to reduce operational downtime and improve future ESP completion designs. This paper will also demonstrate how severe sinusoidal well profiles impact production operations.
New Approach for Modeling Progressive Cavity Pumps Performance
Authors: Gamboa Jose , Aurelio Olivet , Sorelys Espin
Published: December 2007

Progressive Cavity Pump (PCP) performance has been traditionally modeled as a composition of Couette flow and Poiseuille flow, represented by pump displacement and internal slip respectively. Pump displacement can be easily calculated from pump components geometry, but calculating internal slip is not a trivial problem. Previous studies have proposed to use Hagen-Poiseuille equation for modeling internal slip flow, assuming a constant interference value. In these studies slippage gap area is not clearly defined, so great results have not been reached.

This study introduces a new approach for modeling single lobe PCP performance. Slip flow is modeled as the result of two components, one of them due to the movement of the rotor and the other one due to the differential pressure between cavities, assuming that slippage gap area depends on the stator material. This assumption is based on the analysis of metallic, elastomer and PTFE stator PCP characteristic curves, obtained from experimental data of previous works.

The existence of a strong relationship between slippage gap area and differential pressure, related to mechanical properties of stator material, is demonstrated. Thus, internal deformation of stator is identified as the main parameter to be understood before predicting PCP performance. For a polymer stator PCP this relationship approximates to a quadratic form, while in a metallic stator PCP a constant gap area can be assumed.

Although the proposed model is not able to fit data for any PCP models, its results agree with the ideas proposed above and documented PCP performance theory. In order to obtain a definitive model, future investigation is needed to improve expressions for calculating friction factor inside the pump and also to define a procedure for obtaining gap area relationships for any type of stator material.
Management of Typhoon: A Subsea, Deepwater Development
Authors: Ring Jasper N. , Bourgeois Christine S. , Howard James , Melillo Allan J. , Neal Scott L. , Smith Steve
Published: December 2007

Typhoon, located in the Green Canyon area of the Gulf of Mexico, is a joint deepwater development between ChevronTexaco (operator) and BHP Billiton. First oil was realized in July 2001, just six years after acquiring the leases. The Typhoon development consists of a mini-tension leg platform (TLP) with 4 subsea wells in approximately 2100' of water. Recently, Boris, a joint project between BHP Billiton (operator), ChevronTexaco, and Noble Energy Partners, was discovered in an adjacent OCS block, and 2 subsea wells were tied back to the TLP. The field consists of several hydrocarbon bearing sands with 60% of the field's proven reserves located within a single reservoir.

Characteristics typical of many deepwater developments such as high flow rates, compartmentalization, reservoir compaction, and asphaltene precipitation are prevalent at Typhoon. As a result, asset management is complex and requires each well to be managed independently. The primary purpose of this paper is to describe how the asset and wells are managed and to heighten the awareness of associated complexities. This will be achieved by providing an overview that includes well and reservoir performances to date, reservoir management processes, and idiosyncrasies associated with operating a deepwater, subsea development in the Gulf of Mexico.
Extended Reach Stimulation with Coiled Tubing: A Case Study
Authors: Patrick Kori , Hornett Mark , Foose Joe
Published: December 2007

Extended reach horizontal wells in Western Canada and around the world are increasing in numbers as operators maximize well production. As the length of the horizontal increases, so does the challenge of open hole stimulation.

Burlington Resources, in association with BJ Services completed what is believed to be the deepest open hole horizontal re-entry with coiled tubing, in the world. This paper reviews stages of planning, design/modelling and operations required to successfully stimulate the Burlington Hinton well with coiled tubing.

The well was completed to a total depth of 21,670 ft with end of tubing at 18,308 ft. The 3,363 ft open hole section was drilled with a 5.875 inch bit. A 1.75 inch tapered coiled tubing string was designed to reach total depth (TD) unassisted by any extended reach bottom hole assembly. Several different factors, including completion and coil size, dogleg severity, buoyancy, friction, fluid type and others affect possible lateral extension into the open hole. Some of these factors can be identified and configured prior to running coiled tubing in hole. Others change during treatment. A computer model, Circa, was used to design the coiled tubing string size and to predict effects of many variables.

Once the process for entering the well was designed, three other methods were contemplated during the operational stage to assist the coiled tubing to bottom. Invert mud was left in the open hole in order to lubricate the coil and reduce frictional drag.A metal to metal friction reducer was on location as a contingency to reduce friction in the system.The coil could be displaced to nitrogen and "floated" in.

Only the first of the above procedures was required to reach TD. A detailed pumping schedule during run in hole was designed to keep the invert mud in hole until reaching TD. It was then removed prior to pumping acid. This paper references some of the fluid compatibility issues associated with pumping water, diesel, and acid when in contact with drilling mud. With appropriate planning, design/modelling and execution, this case study proves that a successful treatment program can be performed on extended reach horizontal wells.
Organisational and Technical Aspects of an Ultra-Reliable Mud-Logging Service Capable of Remote Operation and Control
Authors: Kårtveit S. , Sawaryn S. J. , Jones B. L. , Wahlen M. , Mosness T. L.
Published: December 2007

The development of Baker Hughes onshore operations centre, BEACON was described in the paper SPE78336. A critical component of the concept is the movement of certain services, including mud-logging, from the rig site to shore. Traditional mud-logging systems were designed assuming that the operators could intervene when required, for example to repair or calibrate the sensors. By moving people onshore, this assumption is no longer valid. Further, changes must be made to the work processes, including people competencies and training, to match the new working practices. Experience on BP's Valhall DP operations demonstrated that greater reliability would be required in all aspects of the mud logging service to achieve the reliability goals.

In January 2002, Baker Hughes INTEQ and BP were awarded a grant under the Norwegian Demo2000 program to develop a rig and operator independent ultra-reliable mud logging service capable of remote operation and control from the centre, located in Stavanger. The funding has enabled the issues related to the intimate mixture of people, process and technology to be addressed.

To help address the competency issues, a state-of-the-art mud logging training facility has been created. A new generation of high reliability sensors including an innovative gas trap and hydrogen generation device have been produced. Technicians will be able to maintain and calibrate these from the onshore centre. At the same time, new work processes have been developed to improve business efficiency and HSE. These are small, but critical steps to help shape drilling automation in the future.

The paper contains a description of the system's analysis, including a comparison with the NORSOK standards, which serve as a benchmark. The additional requirements imposed by the need for remote control are also presented.
Integrating Internet Technologies to Achieve Team Synergy and an Improved Operational Efficiency/Work Flow in an Asset Team
Authors: Inyang Ubongabasi I.
Published: December 2007

Complexities and varied areas of expertise in the management of an asset necessitated the adoption of team approach for effective reservoir management. Well-integrated asset team for the management of an asset comprises of petroleum engineers, geologists, facilities & safety engineers, operation personnel and various contracting companies. The group in synergy coordinates the various forms of field developments, operations, reservoir surveillance & data acquisition, well maintenance and workovers. An asset team is faced with an enormous challenge of ensuring that it achieves its goals and synergy between stakeholders, is faced with operational problems. The most critical is communication. This hinders operation and productivity, as all stakeholders are not up-to-date for prompt decisions, job status and rapidly changing well/field conditions. The drive for greater efficiency combined with the ever increasing complexity of today's assets requires an improvement in workflow method.

The latest achievements in Internet technologies call for re-engineering of teamwork methodology. Internet avails an opportunity to improve our work method to create an atmosphere of excellent communication and collaboration that can promote effective team strategies to leverage reduced cycle time, increase participation, share best practices and value creation. This paper intends to illustrate how IP (Internet Protocol) communication can be used to create collaboration, communication and enhance productivity tools. This will establish a central place where every team member and stakeholder across geographic location is kept up-to-date. IP communication utilizes the converged network of integrated voice, data and video to mimic a conference room meeting. The result is immediate access to information that is the key to success where decisions need to be made promptly. The organizational impact of these will be a significant benefit in the areas of improved communication, productivity, enhanced capital, strengthened teamwork across divisions and geographic boundaries, improved processes, efficiency & productivity, work flow along with employee satisfaction, sense of belonging and accomplishment.
Cyclic Noise in Open-hole and Cased-hole Logging Measurements: Its Impact and Remediation
Authors: Fitz Dale E. , Mills Andrew A.
Published: December 2007

Cyclic noise can complicate interpretation of open-hole log data, cased-hole log data, and pressure transient data, especially when its amplitude becomes large relative to the primary measurement of interest. Sources of cyclic noise include the following: winch magnetism that affects the spontaneous potential measurement; cyclic (spiral or threaded) bore holes that cause variable standoff on bulk density, neutron porosity, and pad-type resistivity measurements; drill ship and floating platform vertical movement from wave action that can affect the absolute velocity of flow meter tools, reciprocating tool movement from logging-while-tractoring that affects the absolute velocity of flow meter tools; and tidal effects on long time pressure transient tests.

Depth (time) domain filtering of log data affected by cyclic noise is not suitable in most cases because the filter length required to treat the problem causes severe reduction in the vertical resolution of the filtered log measurement. Frequency domain filtering using fast Fourier transforms has been used in the past to eliminate random noise using low pass filters and to determine the vertical resolution of logging measurements. Frequency domain filtering using fast Fourier transforms is readily amenable to treating cycle noise using notch filter(s) centered around the frequency (or frequencies) of the cycle noise. This approach has been used in the electronics industry for decades. Although these techniques are simple to implement, they seldom are used for logging data because stable filter application usually requires interactive filter design.

This paper will review the methodology of applying fast Fourier transforms, designing frequency-domain filters, and applying them. Examples applying this approach to several of the types of cyclic noise listed above will be presented. Issues associated with non-zero mean cyclic noise such as is the case for log measurements made in spiral bore holes and its impact will be addressed.