bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Method for Acid Stimulation without Increasing Water Production: Case Studies from Offshore Mexico
Authors: Reza G. H. , Soriano E. , Eoff L. , Dalrymple D.
Published: December 2007

Successful acid stimulation requires a method to distribute the acid between multiple hydrocarbon zones. Since almost all producing wells are inhomogeneous, containing sections of varying permeability, this can be a huge problem. In addition, the water saturation of the various zones plays an important role. Since acid is an aqueous fluid, it will tend to predominantly enter the zones with the highest water saturation. These water zones are also often the highest permeability zones, so acid stimulation will often result in large increases in water production. There are many negative aspects to increased water production, such as increased lifting and disposal costs, increased corrosion, etc. This paper describes the use of a new low viscosity system that inherently reduces formation permeability to water with little effect on hydrocarbon permeability, and also diverts acid from high permeability zones to lower permeability zones.

This new system has been used in offshore Mexico in the Chuc, Caan, and Pol fields among others over the past year. During this time, over 30 wells have been treated with the new system. Most standard acid treatments in this field result in increased hydrocarbon and water production. The new system has resulted in increased hydrocarbon production with no increase in water production, and in some cases a decrease in water production. Details from several of these jobs will be presented showing the diversion and production results.
Horizontal Well Drilling and Completion Schemes Consider Future Stimulation To Optimize Production
Authors: Surjaatmadja Jim B. , McDaniel Billy W. , Case Leonard R. , East Loyd E.
Published: December 2007

The importance of ensuring maximum production of a well throughout its lifetime is unquestionably very important for the operator. Well lifetime starts from the beginning (i.e. drilling and completion) and proceeds through production, production decline, and finally consideration of a stimulation treatment. In situations where all wells are vertical, this process has become well understood. A different situation exists however when horizontal completions are used because only 20 years of practice is behind us. Nevertheless, one thing is clear: whether the horizontal well is drilled in a low- or a high-permeability reservoir, there will always be a need for stimulation and re-stimulation. Unfortunately, too many horizontal wells were completed with no plans for stimulation, and often, these wells can not be stimulated effectively because of mechanical or reservoir limitations. Had these wells been constructed with stimulation in mind, extensive preplanning could have helped overcome such limitations beforehand.

This paper discusses many field and reservoir aspects such as formation geology and localized tectonics that may influence proper well placement for future applications of fracture stimulation. Emerging new completion tools and processes that enable fracture stimulation should be evaluated to allow wells in less promising areas of the reservoir to become economic contributors rather than net losses on the ledger. All such considerations should be incorporated in the general recovery plan for a field, as well as proposed completion schemes (especially perforating techniques) that might be used to produce the well when stimulation is not required, keeping in mind that stimulation is still a future option. Different completion schemes may have to be used for each well based on its position within the field. Field experience with supporting data will be presented and discussed in depth, as well as conventional and new stimulation options that would optimize specific applications.
Consideration for Future Stimulation Options is Vital in Deciding Horizontal Well Drilling and Completion Schemes for Production Optimization
Authors: Surjaatmadja J. B. , McDaniel B. W. , East L. E. , Pyecroft J.
Published: December 2007

Thorough planning of a well, or better yet, a field, to determine how each well can provide maximum production throughout its lifetime is unquestionably very important to the operator. For fields of vertical wells, this process is well understood. For horizontal completions, however, only 20 years of practice are behind us. For lower permeability reservoirs, the theory that using horizontal wellbores can eliminate fracture stimulation has proven to be false. Today, the assumption that moderate to higher permeability reservoirs will never be candidates for stimulation is also being challenged by a high number of non-economic wells. Too often, we find many of these horizontal completions need stimulation but are not candidates because of the mechanical limitations of the completion plan.

This paper discusses the many field and reservoir aspects, including formation geology and localized tectonics, that can influence proper well placement for future applications of fracture stimulation. The evaluation of emerging completion tools and processes that enable fracture stimulation should be nurtured to allow wells in less promising areas of the reservoir to become economic contributors and not net losses on the ledger. These wells must be incorporated into the general recovery plan for a field and taken into account in completion schemes (especially perforating techniques) to best produce the well when stimulation is not required, yet keeping stimulation as a future option. Different completion schemes may have to be used based on the position of the well within the field. Field experience with supporting data will be presented and discussed in depth, as well as conventional and new stimulation options that would optimize the specific applications.
Design and Implementation of Retention/Filtration Media To Improve Heavy Oil Production
Authors: Underdown David R. , Hopkins Sam
Published: December 2007

The factors that control the performance of sand control screens that use woven metal mesh as the filter media; i.e, commonly called "premium screens", are not generally well understood by the end user. The end user is provided a premium screen with a woven metal mesh with some weave type, and told the sand control screen is better than the other premium sand control screens on the market. The end user is told that the premium sand control screen uses such material as Dutch, Dutch Twill or a Reverse Dutch Twill woven metal mesh, and some cases the manufacturer will promote the benefit of multiple layers of woven metal mesh filter media in the sand control screen to control the sand. All this information is interesting, but the end user really does not understand the significance of the information.

This paper presents the results of a study to evaluate the effect of different woven metal mesh weaves on the performance; i.e., dirt holding capacity and plugging tendency, of media commonly used in sand control screens for deep water and heavy oil completions. The work also introduces a new approach to designing sand control screens that use woven metal mesh material. The performance criteria used in the evaluation of different designs for the filter media include control of solids, and the impact of particle size distribution of the formation on the plugging on the surface and in the filtration media. Laboratory testing demonstrates that use of a different type of construction of the retention/filtration media allows for greater performance than currently used media in sand control screens.

The significance of the approach discussed in the paper is the ability to design and engineer a sand control screen with a retention/filtration media for a given particle size distribution of the formation that allows for maximum oil production and minimum solids production. Critical to the success of this approach to designing sand control screens is the thorough evaluation/testing of multiple media types to create the "formation specific" design.
Evaluating Inter-/Intrazonal Isolation
Authors: Tiwari Anil Kumar , Rajasekaran Pitchai , Katare R. P.
Published: December 2007

There are two major challenges in achieving perfect and durable inter/intra zonal isolation; accurate planning of cementing operations according to well specific requirement and realistic evaluation of operational performance for attainment of the objective. Prevailing practice for evaluating cementing performance, in the industries is not authentic enough to justify remedial operations planned. It just based on readings of graph while other critical aspect such as phenomenal formational response, influence of other processes which are being performed / to be performed prior to or post cementing operations like hermetical testing of casing, various activation/stimulation processes which could affect the quality of evaluation/performance are overlooked.

The objective of study is to address all the relevant aspects while interpreting the logs and develop a methodology for making precise and realistic evaluation of logs for avoiding many futile operations which ultimately affects the productivity and life of the wells.

The procedure adopted for formulation is as under Compilation / analysis of log data field wise Compilation / analysis of production trend with reference to cementing performance.

Mathematical model exhibiting impact of stresses produced during pressure testing at various stages of cementing through well completion process and its influence over logs and cement bond integrity.

Influence of formational image on sonic log graph.

Organization of all logical and mathematical data to design and develop realistic-precise methodology.

This paper provides (i) an innovative approach to the prevailing practice (ii) helps to develop a methodology which may utilize all those data presently ignored (iii) to devise a precise diagnostic tool in the form of software to reduce human error, this is under conceptual stage.

This methodology may limit its application to the development field as exploratory wells may not have sufficient quantum of data for uploading in the software for analysis.
In-Fracture Explosive Hydraulic Fracturing Fluid and Its Rheological Study
Authors: Cui Mingyue , Shan Wenwen , Jin Liang , Ding Yansheng , Ding Yunhong , Chen Li , Liu Ping , Xu Zhihe
Published: December 2007

Low permeability reservoirs take a large portion of the newly discovered hydrocarbon reservoirs. Stimulating low and ultra low permeability reservoirs faces more technical challenges.

Unlike other stimulation techniques such as "well shooting", "nuclear explosion", and "high energy fracturing", the concept of in fracture explosion (IFE) is to create a fracture hydraulically, convey solid explosives deep into the fracture and place them in the fracture. Then ignite the explosives in the fracture to generate crushed zones or shear fractures near the main fracture while keeping the well bore intact. In such a way, the well productivity is increased. For complex tight gas reservoirs, especially those that tend to develop multi fractures and shear fractures by conventional hydraulic fracturing making the placement of proppant difficult, this technology has irreplaceable advantage.

Fracturing fluid for in fracture explosion has two functions -to carry solid explosives while create hydraulic fractures, and to propagate ignition. This study has found such a fluid system that can meet both general requirements for hydraulic fracturing fluid and the realization of lighting, transmit fire, ignition, and propagate explosion under simulated reservoir conditions.

The fluid system was tested successfully in a narrow fracture simulator. Expected explosion realized in this simulation. The simulated fracture has a length of 2300 mm with variable width of 0–50 mm. The process of squeezing, igniting, and explosion of 300g TNT equivalent was tested.

This fluid system has the following properties:

Rheology at reservoir temperature can be adjusted according specific requirement. Viscosity ranges from 10 to 50 mPa.s. Wall building leak off coefficient is 3.6×10−4 m/min0.5 and spurt loss is 0.25 ml/cm2. Combined with a regular fracturing fluid as a lead (pad), such properties allow the fluid to satisfy the requirements of generating deep fractures and transport/place explosives in the fractures.

This paper will provide details of the study and discuss the potential applications for tight gas reservoir stimulation.
Electrostatic Demulsification on Crude Oil: A State-of-the-Art Review
Authors: Noïk Christine , Chen Jiaqing , Dalmazzone Christine
Published: December 2007

Electrostatic coalescence is the most efficient water-in-crude-oil demulsifying technology having been adopted in upstream dehydration and downstream desalting operations. Significant improvements in the capacity and performance of existing crude oil dehydrators/desalters have been achieved through continuous improvement in the mechanism research, the electric field development, and the practice of pre-coalescing step.

The first part of this paper presents the current understanding about the electrocoalescence mechanism of water droplet in crude oil emulsions up to now. Besides analyzing various forces acting on the water droplet at a macro-scale, it also discusses the influence of turbulent flow conditions and electric field voltage/frequency.

The second part of this paper presents systematically some typical technologies in electrostatic demulsification process and online electrostatic pre-coalescers up to now. For the electrostatic dehydrator/desalter, the authors pay more attention to the composite plate electrode, PC-based Load Responsive Controller, improved feed-stream distribution and variable voltage/frequency electric field. The variable voltage/frequency technology is the tendency which makes it possible for the customer to adjust the voltage and frequency simultaneously according to the corresponding physical properties of the inlet crude oil stream, thus the dehydration efficiency will definitely be improved. The typical representatives of compact electrostatic pre-coalescer which have achieved successfully field trial results, such as CEC, IEC, VIEC, highlight the moderate turbulent flow in their corresponding proprietary technologies, rather than the power supply.

Finally, some technological tendencies related with electrostatic coalescence of water-in-oil emulsions have been presented, such as integration with centrifugation, combination with flotation, etc.. Considering that heavy oils are becoming increasingly attractive from the stand point of reserves and economic status including China, the authors introduce the challenge and some successful trials on the electrostatic dehydration of heavy oils. Some suggestions are put forward as concluding remarks.
Rotary Steerable Systems Result in Step Change in Drilling Performance – A Case Study
Authors: Malik Mirghani , Tewari Raj Deo , Naganathan Sivaraman
Published: December 2007

Exploration and development of Heavy oil fields with high water cut and sand production in Muglad basin in Nothern Africa started with vertical wells and as time progressed matured into drilling Horizontal wells.

Typically drilling challenges in this area include drilling very reactive shales, shallow kick off depths and high build rates, unconsolidated sand stones interbedded with shales which are sensitive to mud weight and are prone to lost circulation.

First few horizontal wells were drilled with conventional technology of positive displacement motor with silicate mud. Many of these wells faced hole cleaning issues leading to pack off, excessive back reaming and stuck pipe incidences. Uneven build rates via sliding in interbedded formation leading to high borehole tortuosity. It is significant to note that due to these difficulties one of the planned horizontal wells was side tracked three times after stuck pipe incidences and finally completed as a 30 degree deviated well with a total cost over run of 300% above AFE.

Since then Rotary steerable system has been deployed to drill these challenging wells with significant improvement in drilling performance, saving days and cost and eliminating stuck pipe incidences. This paper compares the performances of drilling with PDM Vs RSS in the same reservoir and presents the lessons learnt. A cost benefit analysis has also been performed and it clearly shows that RSS is both technically and economically a sound approach to drilling horizontal wells in Muglad basin.
History Matching with Combustion-Tube Tests for Light-Oil Air-Injection Project
Authors: Onishi T. , Okatsu K. , Teramoto T.
Published: December 2007

A series of experiments is essential in light oil air injection (LOAI) study. Accelerating Rate Calorimeter (ARC) test, Thermo Gravimetric Pressurized Differential Scanning Calorimeter (TG/PDSC) test and Combustion Tube (CT) test are generally conducted to evaluate a potential of air injection in fields. ARC test is used to determine the extent and continuity of reactions in the low and high temperature range. TG/PDSC test also helps to identify the temperature ranges over which oil reacts with the oxygen. The purposes of the CT test are (1) to assess the overall burning characteristics of oil, (2) to measure incremental oil production, air and fuel requirements and other parameters and (3) to measure produced gas compositions and oil and water production to provide benchmarks for monitoring future field operations. On this series of experimental work, using domestic oilfield sample, two CT tests were conducted, in low water saturation case and high water saturation case after waterflooding, to estimate the applicability of LOAI including on tertiary mode. Both tests showed stable combustion performance in terms of temperature, pressure response, produced gas compositions and incremental oil production.

On the other hand, numerical simulation is important to predict field production performance. The appropriate reaction kinetics on the combustion has to be used in the numerical simulation. History matching with CT tests were conducted to obtain the kinetics, and two kinds of reactions, "oxidation reaction" and "combustion reaction" were used in the study. In the former reaction, oxygen is consumed by the oil to form oxidation compounds. In the latter one, oxygen reacts with the compounds to form carbon dioxide and water. Reaction parameters were used as matching parameters. Results of history matching with both CT tests using same reaction kinetics were obtained.

This paper presents the results of the CT tests and the history matching studies with these tests and also some discussion of the air injection process.
An Integrated Approach to Risk and Hydraulic Simulations in a Well Control Planning Perspective
Authors: Arild Øystein , Kåre Fjelde Kjell , Løberg Tove
Published: December 2007

Being an environmentally sensitive area, wells drilled in the Barents Sea are subject to comprehensive well planning, particularly with respect to well control issues. On the Obelix field, which is a limestone prospect in the Barents Sea, an extensive quantitative risk-based well control study was undertaken in order to establish robust operational routines for facing major risks and uncertainties.

An advanced dynamic computer model was used to evaluate potential well control scenarios which could occur. Drilling into caves can lead to severe mud losses and introduce large influx volumes in the well. An important part of the study was therefore to include a discussion of possible scenarios, e.g. mud loss and influx detection critiera and evaluate procedures for mitigating severe losses. The advanced well control model was then used to evaluate the consequences of large influx volumes. Since the well was relatively shallow with a potential for large influx volumes, gas migration issues and consequences related to that was evaluated thoroughly. It was important to stress the need for rapid well control response in case of such events.

The model was also used to evaluate maximum casing shoe pressure for various kick volumes, and the typical dynamics to be seen when applying a given well control method for safely bringing up the kick. Special focus was on evaluating the dynamics of large influx volumes e.g. with respect to separator capacity.

The paper aims at presenting a way of working, where the initial work focus on obtaining an overall quantitative risk assessment with respect to well control. Critical factors are then identified in order to direct more detailed studies.

The paper also demonstrates that advanced models are necessary in order to support operational choices and procedures. The holistic approach which combines modelling and practical insight is regarded as a valuable improvement to better well control planning.
Using Laboratory Flow Experiments and Reactive Chemical Transport Modeling for Designing Waterflooding of the Agua Fría Reservoir, Poza Rica-Altamira Field, Mexico
Authors: Birkle P. , Pruess K. , Xu T. , Figueroa R. A. H. , López M. Díaz
Published: December 2007

Waterflooding for enhanced oil recovery requires that injected waters be chemically compatible with connate reservoir waters, in order to avoid mineral dissolution-and-precipitation cycles that could seriously degrade formation permeability and injectivity. Formation plugging is a concern especially in reservoirs with a large content of carbonates, such as calcite and dolomite, as such minerals typically react rapidly with an aqueous phase, and have strongly temperature-dependent solubility. Clay swelling can also pose problems. During a preliminary waterflooding pilot project, the Poza Rica-Altamira oil field, bordering the Gulf coast in the eastern part of Mexico, experienced injectivity loss after five months of reinjection of formation waters into well AF-847 in 1999. Acidizing with HCl restored injectivity. We report on laboratory experiments and reactive chemistry modeling studies that were undertaken in preparation for long-term waterflooding at Agua Fría. Using core plugs obtained from the field, laboratory flow experiments were conducted to examine sensitivity of mineral dissolution and precipitation effects to water composition. Native reservoir water, chemically altered waters, and distilled water were used, and temporal changes in core permeability, mineral abundances and aqueous concentrations of solutes were monitored. The experiments were simulated with the multi-phase, non-isothermal reactive transport code TOUGHREACT, and good to excellent agreement was obtained for changes in solute concentrations. TOUGHREACT was then used for reservoir-scale simulation of injecting ambient-temperature water (30°C, 86°F) into a reservoir with initial temperature of 80°C (176°F). Untreated native reservoir water was found to cause serious porosity and permeability reduction due to calcite precipitation, which is promoted by the retrograde solubility of this mineral. Using treated water that performed well in the laboratory flow experiments was found to be able to avoid excessive precipitation, and allowed injection to proceed.
Synergy Between Engineered Fibers and Lightweight Cement Slurries to Cement Depleted Formations
Authors: Zepeda Garduño Rafael , Martinez José Antonio , Maldonado Reinaldo
Published: December 2007

The production of hydrocarbons from pressure-depleted zones is becoming a common practice around the world and drives the constant development and improvement of cementing technology. This paper addresses the evolution of lightweight cement slurries to ensure zonal isolation and mechanical stability of casing in highly permeable and depleted formations.

To prevent lost circulation while cementing depleted formations, a new technique has been developed based on adding inert fibers to ultralightweight slurries. During the cementing operation, the fibers create a network across the loss zone, to enable the cement to bridge off these zones and regain circulation. Also, these fibers enhance the mechanical properties of the cement as the created net provides additional stability to resist tensile stresses.

This paper discusses the challenges and solutions of developing ultralightweight slurries (without foaming) that control rheology and cement properties by the interaction of fibers and cement particle size distribution.

The paper addresses the synergies that cement slurries and inert fibers, with specific gravity values between 1.0 sg and 0.88 sg, bring to cement production casings in the Cantarell field of Mexico. The pay zone of the Cantarell field is a highly fractured, highly permeable, vuggy, and depleted Cretaceous formation that is typically drilled under total loss of circulation. The ability to reduce and prevent losses of slurry by adding this engineered fiber helps to ensure that the cement slurry is placed according to design to provide good zonal isolation and to permit completion of the new well.
A Holistic Approach to Production Assurance
Authors: Gonzalez D. , Jamaluddin A.
Published: December 2007

Due to the large potential reserves, increased global demand for oil and high oil price, exploration & development in deepwater and more challenging areas around the world have become a key target for the majority of oil and gas Exploration and Production Companies. Development activities in the deepwater face significant challenges. Of particular concern are the effects of produced fluid hydrocarbon solids (i.e. asphaltene, wax, and hydrates) precipitation and their potential to disrupt production due to deposition in the near-wellbore regions and production tubulars. Besides hydrocarbon solids, other production hindrance elements include wellbore fluid loading, fluid slugging, inorganics, corrosion, erosion and emulsions. All these elements adversely affect production assurance in deepwater systems and are key risk factors in assessing deepwater developments. The production assurance risk factor can create game-changing impact on field development planning, especially, when dealing with marginal deposits having variable fluid characteristics.

In this paper, we will review and provide a synopsis of some of these production hindrance elements. Consequently, we will discuss how some of these elements can affect the field development planning by utilizing a field example.
Enhanced Oil Recovery by Utilization of Multilateral Wells on the Troll West Field
Authors: Berge F. , Ruyter E. , Grønås T. , Vasicek A.
Published: December 2007

Norsk Hydro has been installing multilateral wells for 10 years. By the end of March 2006, a total of 64 multilateral junctions were installed. The vast majority have been sealed TAML level 5 junctions constructed from floating vessels, primarily on the Troll West field. Hydro identified early multilateral wells as a key technology to enhance the oil recovery from the Troll West field. In 1995, a multilateral technology vendor was selected as supplier of multilateral systems. The close cooperation between Hydro and the multilateral technology vendor has been the key to the development of new multilateral systems and system variants to meet new requirements for the implementation of this emerging technology.

This paper will briefly describe the development of the FlexRite® system and the subsequent variants like FlexRite® Intelligent Completion Interface and ReFlexRite®. Field operations involving these systems will be discussed, and the use of multilateral wells on Troll West will be presented in some detail with respect to; statistics for junctions installed by March 2006, presentation of example wells and economic effects from the use of multilateral wells.
Integrating Geology and Velocity Data To Constrain Pressure Prediction in Foldbelts
Authors: Couzens-Schultz B. A. , Hedlund C. A. , Guzman C. E.
Published: December 2007

This paper focuses on the first drilled prospect in the Perdido fold belt, deepwater Gulf of Mexico. The original test well, AC600-001, did not reach its objective, but encountered shallow hard geopressures and the well was lost. That result was unexpected. The seismic velocity trend and data from previous deepwater wells suggested near hydrostatic pressures. To drill a second well, the problem of finding an optimal well location that avoided low drilling margins was addressed. The work involved re-picking of seismic velocity, trend analysis, and developing end-member rock models for pore pressure prediction using constraints from a mechanical seal failure analysis.

Areas of higher velocity, and hence lower predicted overpressure were identified in the same stratigraphic interval that the first well was lost. The second well was drilled successfully through one of these areas. The velocity results, combined with constraints from top seal failure were used to construct drilling margin maps. These indicated that beneath the stratigraphy where the first well was lost, drilling margin would increase. Once a path was found through the shallow hard pressures, the well would be drillable to objective. Results from the second well show that pressure prediction using seal failure arguments is a good first approach. The re-picked seismic velocity data at the well location was fast as compared to the checkshot data, but within error. The methodology is limited by assumptions on sand continuity from top seal failure locations and by velocity fidelity.

Hard overpressures and top seal failure are common aspects of deepwater fold belts. These prospects can be difficult to drill and can be under-filled. Deepwater foldbelts often have little well control to constrain predictions within them. The techniques presented here can be adapted to other foldbelts, and were used to evaluate and rank other Perdido prospects.
H2S Associated With Heavy Oils in Reservoirs Under Primary Production: Cases of Grimbeek and El Alba Fields in Gulf of San Jorge Basin, Argentina
Authors: Cavallaro A. N. , Cerroni M. , Alberdi M. I. , Ostera H.
Published: December 2007

Reservoir souring is a well-documented problem that appears normally when seawater is injected into sweet reservoirs during secondary recovery programs In these cases, microbiologic souring by the growth of sulphate-reducing bacteria (SRB) is the most accepted mechanism.

In some cases, H2S production is reported from the earliest stages of reservoir development. This phenomenon has been named "geologic souring"(2) because the H2S source is generated in the geological past and it is related to some element within the petroleum basin, but not-related to modern microbiological or geochemical processes.

Recently, H2S production has been recorded in El Alba-1 and Grimbeek-1 reservoirs (Manantiales Behr area, San Jorge Basin) where there are no previous reports of sources of H2S. Furthermore, water flooding has not been implemented before the H2S measurement campaing in the field. Thus, the H2S generation mechanism is the main target of this study.

Correlations of isotopic chemical analyses and isotopic measurements from gas, waters and oil samples were developed and integrated into the geological and enginnering information. After the interpretation stage, a monitoring plan and some mitigation options were suggested.

The H2S measurements, geological data and isotopic signatures do not allow locating the H2S source by thermo-chemical decomposition of sedimentary rocks (e.g. anhydrite), kerogen cracking or petroleum decomposition. Chemical data indicate that the sulphate, soluble in connate water, is the most plausible source of sulphur. Moreover microbiological activity is most likely the mechanism of biochemical reduction, even the reservoir show stressing conditions to bacterial development. According to the results, some biocides combined with H2S-scavenging are recommended to mitigate this production inconvient.
Internal Corrosion Direct Assessment for Multiphase Flow Pipeline Systems
Authors: Puente P. G. , Collado C.
Published: December 2007

Owners, operators, regulatory entities and non-governmental agencies focus their attention on pipeline Integrity Management Plans (IMP) to address the safety and reliability of hydrocarbon pipelines as they cross environmentally sensitive areas as well as densely populated areas. IMP includes a base line assessment prioritizing the inspection and remediation of expected sensitive areas. Direct Assessment (DA) along with internal inspection, hydro-test and other equivalent methods to ascertain the condition of the pipeline are used as IMP assessment methodologies.

The topic to be covered in this article is Internal Direct Assessment which includes Erosional Velocity (EV) in addition to Internal Corrosion Direct Assessment (ICDA). This article utilizes the analysis of an onshore gas pipeline in the Gulf of Mexico to identify possible areas susceptible to corrosion.

Multiphase flow analysis simulates the characteristics and specific fluid behavior to determine erosional velocity and internal corrosion in pipelines. A multiphase flow simulator will be used to obtain the specific flow characteristics to evaluate EV and ICDA for the above mentioned pipeline system. Internal corrosion is analyzed both as top of the line corrosion and corrosion at the bottom of the line. In addition multiphase flow simulation provides accurate information related to fluids velocity and residence time.

The internal corrosion rate can be related to residence time of water and other electrolytes to formulate effective mitigation processes. This could serve as the basis for a mitigation program and significantly increase the useful life of a pipeline system.
Predicting Reservoir Compaction and Casing Deformation in Deepwater Turbidites Using a 3D Mechanical Earth Model
Authors: Sayers C. , den Boer L. , Lee D. , Hooyman P. , Lawrence R.
Published: December 2007

Production from deepwater turbidites is made more challenging by geomechanical problems arising from overpressure, reservoir compaction, casing failure, etc. The impact of reservoir compaction on field development is best examined early in the life of the field, when there is an opportunity for proactive planning. The interaction between heterogeneous reservoir layers, well trajectories and stress changes due to depletion is a complex 3D problem; it is best solved using a 3D approach. This paper illustrates the use of a 3D MEM (Mechanical Earth Model) to quantify reservoir compaction, casing failure and surface subsidence for a deepwater Gulf of Mexico turbidite.

Reservoir flow simulation data are used to evaluate stress changes, reservoir compaction, casing deformation and surface subsidence resulting from production. Geomechanical hot spots, where reservoir compaction is predicted to be greatest, are identified to allow production strategy to be optimized. Several possible modes of production-induced casing failure are examined. The likelihood of casing failure is then assessed to facilitate development of strategies for either avoiding such risks, or reducing their impact.

This work shows the importance of developing a 3D MEM early in field development. In high-porosity, pressure-compartmentalized sandstones, quantification of reservoir compaction is essential for planning the casing and completion integrity through the life of the reservoir.
Kuwait Oil Company's Latest Semiautomated Deep Drilling Rig – HAH Rig 124, The Middle East's Most Modern 3,000-HP Land Rig
Authors: Al-Kandari Ayad , Al-Saeedi Mohammed , Kingsborough Roger , Brewster T. W. , Mckinnell David
Published: December 2007

KOC has been drilling deep HPHT wells from the mid 1980’s, and during this time the Kuwait deep well prospects have become deeper and more challenging. The rigs utilized to drill these wells have evolved over the years to meet these challenges, with new technologies being used to improve both operational and safety aspects.

Five years ago an enhanced rig type upgrade was introduced with the application of Top Drive, additional third 1700 HP mud pump and larger 5 1/2" O.D. drill pipe. This resulted in a step-change improvement in drilling performance.

In 2003 KOC began a project to look into the radical re-design of the deep rig specifications. Hamad Al Hamad and Partners was awarded the contract to complete the detailed design, procure and operate the rig, and National Oilwell Varco was assigned as the main rig construction contractor.

For the rig design certain new concepts were to be developed in readiness for a future campaign of deep HPHT exploration wells. These included the following; the rig should be safer and more automated, the capacity of the main equipment items and the mud system should be state of the art both in capacity and equipment specifications, the 15M BOP stacks should be re-designed to minimize handling, and the rig should be adapted for operation in the harsh summer conditions in Kuwait.

This paper will discuss the evolution of Deep Drilling Rig design in Kuwait, the design and specification of the new HAH-124 rig plus the construction/rig-up of the unit. The case study will also focus on lessons learned during this process and conclude with recommendations for future new rig builds.
Gas-Liquid-Solid Coupled Flow Modeling in Fractured Carbonate Gas Reservoir With High H2S Content
Authors: Zhimin D. , Xiao G. , Yong Z. , Xuefeng Y. , Gaojun S. , Yong W.
Published: December 2007

Technical studies, production and operations, and management of fractured carbonate gas reservoir with high H2S-content are difficult and uneconomical tasks to perform due to high toxicity and corrosivity of H2S. The optimization of conceptual design of these reservoirs may become cost efficient through the use of integrated simulation. However, to our knowledge, previous models do not well allow for the characteristics of complex flow through porous media in fractured carbonate gas reservoir with high H2S-content, nor do they consider the influence of the special physical and chemical changes on production performance, which makes the prediction of production behavior uncertain. In this paper, mechanisms of the gas-liquid-solid migration and formation damage resulting from sulfur deposition in fractured carbonate gas reservoir with high H2S-content were investigated by means of numerical simulation. A new gas-liquid-solid coupling model in fractured carbonate gas reservoir with high H2S-content, accounting for sulfur deposition, phase behavior variation, geochemical rock-water-gas interactions, adsorption, was presented. A modified equation of state was also used to describe phase behavior variation and combined with the integrated model. The model can forecast the production mechanisms and performance of fractured carbonate gas reservoir with high H2S-content, particularly, evaluate accurately and rapidly H2S concentration, mole content spatial distribution and dynamic change with pressure or time. This work can also promote safer development design to fractured carbonate gas reservoir with high H2S-content and avoid failure in operations.
Drilling Performance and Environmental Compliance—Resolution of Both with a Unique Water-Based Fluid
Authors: Young Steven , Ramses Gamal
Published: December 2007

In an industry where the technical demands on a drilling fluid are ever increasing, the use of invert emulsion fluids has been seen as a necessity to meet required drilling performance criteria. At the same time there is increasing pressure to comply, and even exceed, the tightening environmental demands on our industry which has made the use and associated waste treatment of these invert fluids complex and costly. A drilling fluid, which has the drilling performance characteristics of an invert emulsion fluid, but can exhibit the benign environmental characteristics of a simple water-based fluid, has long been the goal of fluids development.

This paper describes the development and application of a unique water-based fluid that utilizes a triple inhibition approach to delivering invert emulsion-like drilling performance. Each component of the fluid system has also been designed to ensure compliance with some of the world's most demanding environmental requirements. The resulting fluid is flexible in formulation such that it can be utilized in freshwater on land wells to meet chloride discharge requirements, can be formulated in seawater for shelf wells to meet low toxicity and logistics requirements, and can be formulated in saturated salt water to meet toxicity and performance requirements for deepwater environments.

The applications of this fluid on a global basis will be evaluated, comparing the drilling performance and economics to offset wells which have utilized both conventional water-based fluids and invert emulsion fluids.
Integrated Reservoir Modeling for Evaluating Field Development Options in Agua Fria, Coapechaca, and Tajin Fields of Chicontepec Basin
Authors: Takahashi S. , Abbaszadeh M. , Ohno K. , Soto H. S. , Cancino L.O. A.
Published: December 2007

This paper presents a methodology for pixel-based hierarchical geostatistical reservoir characterization and flow simulation of submarine fan turbidite sandstone deposits in the Agua Fria, Coapechaca and Tajin fields of the Chicontepec basin in the Gulf of Mexico. Extreme heterogeneity of rock fabric and petrophysical properties prevails within the multiple stacks of turbidetic sequence events across the fields. Capturing this complex geologic heterogeneity in reservoir characterizations and reservoir simulation models for strategic decision making in field development is a major challenge. We first present a general methodology based on multivariate Gaussian formalism for integrating various sources of data at different scales to build high-resolution geostatistical reservoir characterization models directly at log scale for the Agua Fria, Coapechaca and Tajin fields. Multiple seismic attributes and geological diagenesis information at sequence and subsequence scales are integrated into these models to generate representative reservoir descriptions.

Next, we use the constructed geostatistical models to investigate recovery performance of Chicontepec fields under primary and waterflood processes. Sector models and pilots of multi wells in the Tajin and Agua Fria fields are considered for this purpose. The fine-scale and coarse-scale reservoir characterization models are calibrated to dynamic performance data by history matching the primary production and an actual waterflood pilot data in Agua Fria, and then used as predictive tools for other field development scenarios. The viability of waterflooding the very low permeability and highly diagenized Tajin filed is investigated, where large reservoirs are still left in-place because of loss of reservoir energy due to primary depletion.
Long-Term Comparative Evaluation of HCl/Formic Acid System Used To Stimulate Carbonate Formations at Severe Conditions in Saudi Arabia
Authors: Nasr-El-Din H. A. , Al-Driweesh S. M. , Sierra L. , van Domelen M. , Welton T.
Published: December 2007

The high levels of carbon dioxide and low levels of hydrogen sulfide content of some deep and high temperature gas producers contributed in the requirement to complete these wells using super Cr-13 tubings. Due to the low permeability of the formation and the associated formation damage issues, acid fracturing treatments were required to optimize the productivity of these wells.

This paper describes the selection, optimization and long term comparative evaluation of the gelled and in-situ cross-linked HCl/formic acid systems used this type of wells. The high temperatures encountered in deep wells and the susceptibility of super Cr-13 to severe corrosion in high concentration HCl systems used for stimulation purposes added one additional difficulty to the acid stimulation process. To overcome these problems, extensive experimental and field studies were performed to select an acid system to enhance the productivity of these wells.

Core flood tests performed with HCl/formic acid systems showed their ability to create deep wormholes in tight carbonate cores; however the corrosiveness of these systems at downhole conditions could be severe if the correct type and concentration of corrosion inhibitor is not used. In general, for the HCl/formic acid systems at downhole conditions (275°F) it was found that high concentrations of corrosion inhibitors are required to protect the super Cr-13 completions.

Based on lab tests study acid stimulations were performed, the flow back fluid was recovered and analyzed to observe the corrosion problems and to optimize the corrosion inhibitor.

In all the cases the wells responded very well to the acid stimulation and the completion integrity was not compromised in a short or long term. The paper also shows for the first time a comparative long term well response to the acid stimulation of the two acid systems used in the area, showing the better performance of the in-situ crosslinked HCl/formic system over the gelled HCl/formic system.
Reaction Kinetics of Gelled Acids With Calcite
Authors: Nasr-El-Din H. A. , Al-Mohammad A. M. , Al-Aamri A. M. , Al-Fuwaires O.
Published: December 2007

Hydrochloric acid is used to stimulate carbonate formations (both matrix and fracturing treatments). However, the reaction rate of the acid with carbonate minerals, especially calcite, is very fast. In addition, the viscosity of HCl solution is relatively low. Acid-soluble polymers are usually added to the acid to increase its viscosity, which is needed to enhance acid diversion during matrix acidizng and reduce acid leak-off rate during acid fracturing. Gelled acid is extensively used in matrix and acid fracturing treatments performed in carbonate formations. However, a few studies have evaluated the impact of these polymers on the reaction rate of the acid.

This paper uses a rotating disk instrument to measure the reaction rate of gelled acids with calcite rocks. Measurements were conducted over a temperature range of 25 to 65°C, a pressure of 1,000 psi, and rotational speeds of 100 to 1,000 rpm. Acid formulations that are typically used in the field were examined. Polymer concentration was varied from 0.5 to 2 wt%. The apparent viscosity of the gelled acid was measured using a Brookfield viscometer. Measurements were done for the same solutions tested with the rotating disk instrument. The temperature was varied from 25 to 100°C, while the pressure was maintained at 300 psi. The shear rate was varied from 57 to 1,700 s−1.

The results obtained indicated that the apparent viscosity increased notably as the concentration of polymer increased from 0.5 to 1.5 wt%. On the other hand, there is significant decrease in the dissolution rates as the concentration of polymer was increased from 0.5 to 1.5 wt%, where there was no measure difference as the concentration increased to 2 wt%. Reverse and toroidal flows were noted within the rotational spends examined. The etching pattern on the surface of the disk depends, among other factors, on the disk rotational speed and polymer concentration. The dissolution rate was found to be a function of temperature, rotational spend and polymer concentration.
Production Optimization of Turbidite Reservoirs in Russia—A Pilot Field Development Case Study
Authors: Kryuchkova T. , Igoshkin V. , Edelman I. , Ruiz H. , Kalita N. , Poettmann P. , Voicu B.
Published: December 2007

This paper presents a field development case study of a low permeability turbidite reservoir in Russia. The giant Priobskoye field contains 30 API crude in laminated sandstones of 0.1 to 20 md at a depth of around 2500 meters. The complex geology, lack of reservoir information and lack of technology availability caused a 20-year gap between discovery and development.

The initial pilot development was halted after poor drilling success, thus the operator invested in 3D seismic acquisition and an integrated, multidisciplinary reservoir modeling and simulation effort. The subsequent development was based on oriented water flooding patterns and massive hydraulic fracturing, together with an artificial lift system equipped with permanent pressure and rate monitoring for evaluation and real time production enhancement.

The optimization of operational practices and introduction of fit for purpose technologies enabled a production increase from an intermittent hundreds of BOPD to more than 75000 BOPD in a period of 3.5 years. The exploitation strategy of this pilot area demonstrated commercially sustainable production from the reservoir and will form the basis for full field development.