bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk Management for Planning of Challenging Reservoir Sections
Authors: Nilsen T.
Published: December 2007

Planning of reservoir sections of wells in faulted and stratified reservoirs is often complicated by the large uncertainties involved. Incomplete knowledge of geological factors and the performance of equipment and operators gives rise to uncertainty with respect to operational outcomes throughout the construction, installation and operation phases, which in turn influence the project cash flows and eventually the overall profitability of the well project. The aim for high production rates promotes technologically ambitious well designs, i.e. penetration of a high number of reservoir zones or an otherwise challenging section trajectory. Efforts for obtaining smooth and safe operations, on the other hand, motivate simpler concepts. Complicated causal relations and lack of methods for quantifying uncertainty makes risk-based optimisation in the well planning process difficult. This paper describes a modelling approach aiming at improving the basis for decision-making by analysis of the uncertainty involved. Risks identified in a review of experiences from a field on the Norwegian continental shelf are presented. Objectives for a risk-based decision tool are discussed and a modelling framework outlined. Examples of detailed modelling for analysis of selected phenomena, depending on proper pressure control in the well construction phase, are described.
High-Frequency Mud Pump Pressure Monitoring Enables Timely Wear Detection
Authors: Spoerker H. F. , Litzlbauer C. H.
Published: December 2007

Higher circulating pressures result in increased wear on mud pump parts, subsequently causing rig downtime for pump maintenance. The paper presents the field experience gained with mounting high-frequency mud pressure transducers and analyzing the pressure signatures of Triplex Mud Pumps to identify pump wear in time for running routine maintenance and service. By comparison with recorded drilling data, every operating condition can be allocated to pressure curves. The characteristics of typical pump wear as expressed in these signatures are discussed together with suggestions how to automate the monitoring system. In addition, mud pumps have been fitted with vibration sensors for supplemental information.
Gripping Without Slipping — The Safe Handling and Running of Chrome Pipe with Hard Surfaces
Authors: Kinzel Holger , Buettner Kurt , Jaensch Manfred
Published: December 2007

In a corrosive downhole environment, the service life of a completion can be severely reduced if suitable precautions are not taken. Pipe made of corrosion resistant alloys (C.R.A.) is used to minimize corrosion. Recently, steel manufactures have developed modified corrosion resistant alloys (C.R.A.), specifically derivatives of Cr13, that are characterized by a black smooth scale surface on the outside of the pipe.

When these so called "Super" or "Hyper" alloys were first used, occasional slipping was reported by field personnel. Fortunately no string was lost and no injuries occurred, however, precious rig time was lost in resuming safe operations. These slippages occurred with various inserts and with all types of slip-type elevators or spiders.

An investigation carried out by the University of Hannover revealed that the surface scale on the pipe had a hardness of over 60 Rc. Even inserts specifically designed for C.R.A. pipe that use special gripping elements, such as the Micro-Grip™ system have a hardness that is only slightly higher than this surface scale. Using conventional wedge type spider and elevator systems can lead to slippage under certain load conditions, if no special precautions are taken.

Based on these results and on the operating principles of wedge type spiders and elevators, a new Compact Spider/Elevator was designed. This device can be either air or hydraulically operated and puts an additional downward force onto the slip, as much as 40 tons for the hydraulic version, so that a firm grip is assured. In addition to conventional steel inserts, the device can be equipped with so called MicroGrip ™ inserts, a gripping system that distributes the required load equally onto a large number of small peaks. This minimizes the indentation of each single peak and thus, as previous research and field experience has shown, preserves the surface integrity of the pipe with regard to corrosion [2, 3, 4]. The device can be run flush-mounted, further enhancing safety on the rig-floor.
REAL-TIME DOWNHOLE DRILLING PROCESS DATA COMPLEMENT SURFACE DATA IN DRILLING OPTIMIZATION
Authors: Robnett E. W. , Heisig G. , McGinley P. J. , Macpherson J. D.
Published: December 2007

In directional drilling, MWD technology is applied to transmit directional and petrophysical data from downhole. In combination with modern directional drilling tools such as rotary steerable systems, MWD technology has enabled the drilling of complex 3D well profiles precisely placed in the reservoir. However, even on these high-tech wells the drilling process itself is still controlled mainly using traditional surface acquired data such as hook load, ROP, RPM etc.

The transmission and utilization of downhole drilling process data in addition to the surface logging data offer a not yet fully explored potential for drilling process optimization, since modern data acquisition technology close to the bit can provide not only more accurate data but also important additional parameters not available at the surface. Examples of value-adding downhole drilling process data are annulus pressure, weight-on-bit, drillstring bending, RPM, bit torque and dynamics diagnostics. Additional drilling process information on drilling hydraulics or drillstring friction can be obtained by feeding drilling engineering algorithms with downhole and surface acquired data.

The paper provides an overview of the available downhole drilling process data and demonstrates with numerous case studies the value that these parameters add. Furthermore, the paper discusses factors constraining the use of the technology and gives an outlook on future developments in drilling process optimization utilizing real-time downhole data.
Simultaneous Stimulations and/or Packing in Multiple Zones. Effective Solutions.
Authors: Romero Jorge L. , Pizzarelli Sergio , Mancini Jimmy
Published: December 2007

This paper describes 12 history cases of the successful applications of Alternate Path (shunt tube) Technology in wells in Bachaquero Lago, Tía Juana Lago and Lagomedio fields, in Lake Maracaibo.

The use of divergent tubes combined with packoff in these wells, allowed to complete two zones in a single trip (stimulation or packing in the superior zone and packing in the inferior zone), reducing the number of pipe trips in each well and therefore, reducing the operational risks and drilling costs. This type of completion will also allow independent isolation in anyone of the zones in the event of watering problems, allowing selective production.

In all the cases, successful gravel packing were achieved as well as 45% saving in drilling time, compared with conventional completion. In all the cases productivity was higher than the initial estimate, without formation sand production, confirming the success of the application.

This technology provides a reliable and profitable alternative for the completion of two or three simultaneous zones.
Using Computational Fluid Dynamics (CFD) Simulation to Model Fluid Motion in Process Vessels on Fixed and Floating Platforms
Authors: Frankiewicz Ted , Lee Chang-Ming
Published: December 2007

Computational Fluid Dynamics (CFD) is a mathematical tool capable of simulating a wide range of fluid flows. Integrated CFD software has been applied to study the flows in two- and three-phase oilfield separators. The influence of inlet nozzle configuration, flow distributors, perforated plates, and outlet nozzles have been studied.

Of particular value has been the ability to simulate wave induced sloshing in vessels mounted on floating platforms. The design and placement of baffles to mitigate liquid sloshing was determined by using CFD to simulate fluid flows in vessels destined for service on floating platforms. The simulations accounted for the movement of the vessel based upon its actual location on the platform and identified the influence of process fluid flows on slosh motion. Where possible, laboratory testing has been used to validate CFD simulation results, leading to increased confidence in the mathematical models.
Crude Oil Emulsions: A State-of-the-Art Review
Authors: Kokal Sunil
Published: December 2007

Formation of emulsions during oil production is a costly problem, both in terms of chemicals used and due to production losses. This paper discusses production and operational problems related to crude oil emulsions, and present a review that will be very useful for practicing engineers.

The first part of this paper presents why emulsions form during oil production, the types of emulsions encountered, and new methods for characterizing them. Crude oil emulsions are stabilized by rigid interfacial films that form a "skin" on water droplets and prevent the droplets from coalescing. The stability of these interfacial films, and hence the stability of the emulsions, depends on a number of factors including the heavy polar material in the crude oil (asphaltenes, resins, waxes, etc), solids (clays, scales, corrosion products, etc), temperature, drop size and drop size distribution, pH, oil and brine composition. These effects on emulsion stability are reviewed.

The second part of this paper presents ways to tackle crude oil emulsions. The focus is on the destabilization of emulsions and the demulsification process. Emulsions are destabilized by increasing temperature and residence time, removal of solids, and controlling emulsifiers. The mechanisms involved in demulsification (flocculation, aggregation, sedimentation, creaming, and coalescence) are discussed in terms of the stability of the interfacial films. The methods involved in demulsification including thermal, mechanical, electrical, and chemical are also presented. Experience and economics determine which methods and to what degree each method is used for emulsion treatment.

Finally, a section on field applications is included that should be useful for the practicing engineer who deals with emulsions, either regularly or on a limited basis. Herein the field emulsion treatment program is discussed, and more importantly, methods to prevent emulsion problems are highlighted. Recommendations are made for reducing and optimizing demulsifier dosage and controlling emulsion problems.
Thermal Desorption as an Alternative to Cutting Reinjection in Niger Delta Waste Management Operations
Authors: Ntukidem James , Omonigho Raymond , Anighoro Sunny
Published: December 2007

Thermal Desorption Units (TDU's) are gradually supplementing cutting re-injection in Niger Delta waste management operations. Its acceptance is based on report from operators in other oil zones and not on any comprehensive study on this inconclusive waste management methodology.

This technology separates contaminants from soil. Contaminated soil is heated in a chamber where water, organic contaminants and certain metals are vaporized. Most of our wastes treated so far are pseudo-oil-based mud cuttings using the High Temperature Thermal Desorption (HTTD) units at 400 to 800 °C (752 to 1472 °F) off well site.

This paper would look at the questions environmental managers' believe are not answered by this method. It would also compare cost cut at future date and draw an analysis based on its benefits, limitations and concern over alternatives as a new form of technology as it is applicable to our geomarket.
Quantifying Tortuosities by Friction Factors in Torque and Drag Model
Authors: Gaynor Tom , Hamer Doug , Chen David C-K , Stuart Darren
Published: December 2007

Tortuosity occurs when a well deviates from a straight hole. The most commonly known tortuosity is the local dogleg severity variation associated with the use of steerable motors in "slide/drill/slide" drilling. However, there is a tortuosity that exists in many wells, which the authors will refer to as "micro-tortuosity" in which the hole axis is a spiral instead of a straight line. This paper presents a study of micro tortuosity using field data from the North Sea wells. The friction factors and tortuosity index are used to quantify the effect of tortuosity on the torque and drag. The results show that hole spiraling, associated with the use of conventional short-gauge bits, is a major contributor to today's friction factors used in the torque and drag model.
Exploitation Evolution of a Mature Oil Field from Campos Basin, Brazil
Authors: Ida M. , Ferreira D.M. , Malagutti S.R. , Thedy E.A. , Castro F.C.C.
Published: December 2007

This paper presents the successful exploitation strategy chosen for a matureoil field from Campos Basin, Brazil. The field was discovered in March 1984 and began producing in April 1985. The exploitation was carried out by stages, eachstage supported by increase in geological and production behavior knowledge obtained along the time. This strategy led the field to be one of the majorproducers of Brazil. Management aspects, such as well production plan, waterinjection and sand control are presented.

Introduction

The field is located in a water depth that varies from 300 to 700 m. Thecurrent production is 49,000 BOIP from 25 wells tied up to three floating production units.

The field produces oil from santonian cretaceous and eocene turbiditesandstones. There are minor occurences of oil in maastrichtian and turonianturbidite sandstones.

The main reservoir of the field is the santonian reservoir, that contains 95% of the OOIP. A non associated gas reservoir also occurs in an oligocenesandstone. Nowadays the field is at half life, having produced half of the recoverable oil volume.

History

The field exploitation was carried out by stages, each stage supported byincrease in geological and production behavior knowledge obtained along thetime. Due to this strategy, the limits of the reservoir have been enlargedalong the time, demanding the implementation of five exploitation projects forthe field.

The period 1984/85 corresponds to the discovery and inicial delimitation ofthe santonian reservoir, based on 2Dseismic data. In order to anticipateproduction and gather reservoir behavior information, in 1985 the wildcat wellwas tied up to a Production Floating System nearby. Three appraisal wells weredrilled and confirmed the existence of the reservoir.

In 1987, the first exploitation project was approved for the field, supported by good production behavior of the wildcat well and based on new3D-seismic data interpretation. The Project I consisted of a FloatingProduction Unit for the field, utilizing three already drilled appraisal wells, four new producers and two new water injectors plus the convertion of thewildcat well into a water injector (Figure 1).

Parallel to that, the exploration staff continued the investigation of thereservoir limits towards east. Two new appraisal wells confirmed that thereservoir extended to the eastern area, incorporating oil volume (Figure 2).One of them was put on stream afterwards, in a water depth record for thattime.
Sand Control: Sand Characterization, Failure Mechanisms, and Completion Methods
Authors: Abass H. H. , Nasr-El-Din H. A. , BaTaweel M. H.
Published: December 2007

Sand production has historically been a problem associated with some consolidated, poorly consolidated, and unconsolidated sand formations. The result is usually lost production due to formation sand and fines plugging gravel packs, screens, perforations, tubular, and surface flow lines or separators.

Completion methods applied to minimize sand production include: gravel packing, sand consolidation, critical production rate, oriented/selective perforation, FracPacking, or any combination of these methods. These techniques are used in consolidated, poorly consolidated, and unconsolidated sand formations. However, there are no guidelines available in the literature on how these methods are selected.

Mechanisms for sand failure include: tensile, shear, cohesive, and pore collapse. Additionally, failure due to chemical effects can occur when the cementation materials are weakened due to chemical interactions. Many mathematical models have been presented in the literature to predict sand failure, and consequently determine sand production. These models are based on different failure mechanisms and include: pressure drawdown/compressive strength, failure based on a given failure criterion such as Mohr Coulomb, cohesive strength failure, elastoplastic failure around a perforation, viscoplastic modeling, and empirical correlations. However, there are no guidelines on how these models are applied based on the characteristics of the sand formation.

Experimental studies have been presented in the literature to model sand failure. These studies include sand arching, hollow cylinder strength, triaxial and hydrostatic, and large scale testing. Laboratory testing are designed to study a given failure mechanism, and thus to predict sand production.

The objective of this paper is to categorize sand formations that potentially exhibit sand failure and sand production. Based on this characterization, an appropriate laboratory testing and mathematical modeling are recommended, and a completion method is suggested. Examples from standstone reservoirs in Saudi Arabia will be used to demonstrate certain methods used for sand control.
Experiences Learned After Production More Than 300 Million Barrels of Oil by Polymer Flooding in Daqing Oil Field
Authors: Wang Demin , Cheng Jiecheng , Wu Junzheng , Wang Gang
Published: December 2007

Daqing Oil Field started industrial scale polymer flooding in 1996. The production by polymer flooding since then has rapidly increased. In year 2001, the annual production by polymer flooding was more than 70 million barrels (bbl), cumulative production more than 300 million bbl and more than 3 thousand wells are on polymer flooding. In these 6 years, much experience has been learnt on large scale polymer flooding including: actual recovery in the field; major factors that influence the recovery and methods to increase the recovery; measures to obtain a uniform polymer flood front; and how to lower the costs of producing crude oil by polymer flooding.
Transient Pressure Unloading – A Model of Hydrostatic Pressure Loss in Wells after Cement Placement
Authors: Nishikawa Somei , Wojtanowicz Andrew K.
Published: December 2007

Hydrostatic pressure loss (unloading) after cement placement is widely considered a reason for early gas migration in wells. In the presence of high-pressure zone, the unloading leads to pressure underbalance causing gas invasion and flow in the cemented annulus.

The work, reported here, is an attempt to analyze and model pressure unloading as a propagation of pressure transient resulting from downhole fluid loss-a primary mechanism of slurry volume reduction. (Experiments, discussed here, had shown that another mechanism of volume reduction-volumetric shrinkage is not at work early enough to contribute to the pressure unloading process.)

The pressure-unloading model has been validated using data from field experiments in the instrumented wells. The theoretical results matched experimental data showing exponential trend of the downhole pressure loss. Also, the model was used in a sensitivity study to identify parameters controlling the process.

The study revealed that large annuli with high water loss would give rapid and large reduction of hydrostatic pressure in the cement column and more likely intrusion of gas. The observation implies that surface holes should be more sensitive to gas migration than deep holes and the cement slurry filtration should be minimized in surface holes. Another finding showed that compressible annular cement systems would be more tolerant to fluid loss in terms of losing hydrostatic pressure than the low-compressibility systems. The observation emphasizes the importance of annular system compressibility control.
Identifying Bypassed Reserves and Monitoring Fluids Using Carbon-Oxygen Logs in Tia Juana Field, Lake Maracaibo, Venezuela
Authors: Mendoza Erasmo , Duran William , Monsegue Alan , García Germán
Published: December 2007

Carbon-oxygen (C/O) tools have been used historically to evaluate wells that are candidates for recompletion, and slim tools introduced in the 1990s permitted the analysis of intervals behind the casing without having to pull the production tubing. The challenge was then to evaluate zones behind both the tubing and casing and very often behind gravel packs. This logging technique requires diligence because the tool is run through the production tubing, which contains accessories such as mandrills, sleeves, and packers that are responsible for changes in the fluid distribution in the annulus. Identification of the fluids in the formation and the well (i.e., in the tubing, in the gravel pack, or in the tubing-casing annulus) requires a full understanding of the C/O tool response in these conditions.

This technology has enabled recovery of bypassed or ignored reserves in mature areas of the Tia Juana field in Venezuela and has permitted the reconditioning of wells with low production and high water cut. It has also facilitated the workover of neighboring wells, mapping fluid contacts by way of construction of structural and stratigraphic sections. This paper briefly discusses the conditions of acquisition, interpretation, and applications of the C/O data acquired in three cases and emphasizes the impact of the workovers on production.
Application of Permeability Predictions in Profile Modification and Water Shutoff Using Genetic Algorithms
Authors: Zheng Jian , Liu Yusong , Li Jiyong , Zhang Daisen , Chen Dehong , Shao Hongyun
Published: December 2007

This paper deals with a new method used to describe the present permeability of reservoir theoretically and its application in profile control and water shutoff. The reservoir permeability has been changed greatly compared with the initial stage of development after long time water flooding. Generally speaking, it is very hard to obtain the current reservoir permeability data. Only the native permeability, which has great diversity with the actual reservoir conditions, can be considered in profile modification. So a lot of problems usually exist in the process program designed according to the native permeability data. It doesn't conform to the actual conditions of current reservoir. So the expected result is hardly obtained after field implementation according to project design. In such cases a good predictor is necessary, requiring more rigorous models capable of adequately handling any inherent non-linearity. Genetic algorithm is a new intelligent computing method, based on which the technology of permeability prediction is developed. The approach adopted here allowed us to integrate the theory of survival of the fittest into our geologic understanding of the reservoir to look for the permeability distribution that is closest to the actual reservoir conditions by using the three operators of selection, crossover and mutation repeatedly. Using genetic algorithm, we have established a relationship between permeability and field production datas that are available. These datas include bottom hole flowing pressure, production rate, waterflood injection rate and water cut etc of test field. This technology is suitable for well pattern or fault-block with balanced injection and production. According to the relative accurate and reliable permeability distribution, the blindness of profile modification project design can be avoided. Accordingly the implementation result can be improved greatly, and can obtain good evaluation by using this technology again after implementation.

This technology has been applied successfully in L58-2 Fault-Block of Linpan Oilfield, M12 Fault-Block of Qinghe Oilfield, M14 Fault-Block of Qinghe Oilfield and Feiyantan Oilfield before and after profile modification to predict their present permeability distributions and evaluate implementation results. The predicted results basically accorded with the performance results analyzed by field technicians, which had led to an enhanced reservoir characterization and decreased reservoir heterogeneity. This benefits both daily operations and reservoir stimulation efforts. This technology will be popularized in Gudao, Gudong Oil Field. With further development and improvement, it will play more and more important role in profile modification, water shutoff and enhanced oil recovery in heterogeneous reservoir.
Laboratory Testing of Long Term Fracture Permeability in Shales
Authors: Cuisiat Fabrice , Grande Lars , Høeg Kaare
Published: December 2007

The results from laboratory and theoretical work pertaining to the permeability of fractures in shale are presented. The main objective of the work is to improve existing models for hydraulic fractures in basin simulators.

A simple theoretical model is proposed to quantify the effect of creep on the permeability of fractures in shales. The model assumes that the aperture of the fracture changes due to creep of the intact shale material at contact points (asperities). The interaction between contact points is not taken into account. The time dependent deformation of the asperities is based on a model published in the literature for the behaviour of clays, and which is calibrated on cap rock materials tested at NGI. The permeability of the fracture is calculated directly from the aperture changes, assuming that the flow along the fracture can be represented as flow between parallel plates. The results from the model show that the effect of creep on the fracture aperture and permeability is not negligible, although closure of the fracture due to creep is only attained after extremely long times.

Some preliminary results obtained with new laboratory equipment suitable to investigate the long term permeability and hydraulic aperture of fractures in shale are presented. Fractured samples from typical North Sea cap shale are subjected to constant effective normal stress. Flow through the fracture and change of fracture aperture are measured continuously with time. The results show that the fracture behaviour is highly sensitive to its degree of "matedness". The measured significant variation in permeability during creep does not seem compatible with the measured small reduction in fracture aperture. The preliminary test results demonstrate the experimental difficulties in obtaining reliable fracture permeability (conductivity) with time.
Dependence of Drilling Specific Energy on Bottom-Hole Pressure in Shales
Authors: Detournay Emmanuel , Tan Chee P.
Published: December 2007

Cutting experiments were carried out to quantify the dependence of the specific energy e (the energy required to cut a unit volume of rock) on the bottom-hole pressure pm and on the pore pressure po in shales. The experiments were conducted with an instrumented cutting device specially designed to operate inside a triaxial cell. With this set-up, four longitudinal grooves could be cut simultaneously on epoxy-coated shale plugs, under confining pressure and initial pore pressure (which is different from confining pressure). The results of about 20 cutting experiments performed on Mancos and Pierre I shales and on Johnstone, an artificial shale, for various combinations of confining pressure (up to 50 MPa) and initial pore pressure are reported in this paper. This preliminary experimental investigation supports the theoretical findings that the specific energy s depends only on pm, and not on the "differential" pressure pm- po in shales under conditions when the rock is shear-dilatant. In such cases, e can indeed be expressed as ε = εo +mpm, where εo denotes the specific energy under atmospheric conditions and m is a coefficient which is a function of the cutter backrake angle θ and the internal friction angle φ of the shale.
New Integrated 3D-Fracture Modeling and Flow Simulation Study: A Giant Saudi Arabian Carbonate Reservoir
Authors: Al Qassab Hisham M. , Al Khalifa Mohammad A , Al-Ali Zaki , Ameen Mohammed , Phillips Robert , Hartley Lee
Published: December 2007

An innovative fracture modeling process has been successfully developed and utilized in a giant Saudi Arabian fracture carbonate reservoir. This modeling process constrains the discrete fractures to sets of geologic drivers describing the fracture relationships to reservoir matrix properties such as porosity, lithology and stylolites as well as to structural attributes including faults and curvature. The reservoir has very good matrix permeability, but it is enhanced significantly by faults, fractures and strataform.

The workflow starts with the construction of a stochastic discrete fracture network generated in a given simulation volume by providing the static distribution of all relevant fracture parameters from image and core logs and geologic drivers. The fracture distribution is then validated in wells with the fracture counts from image logs and cores. The fracture counts from the model were found to give a consistent magnitude with the observed fracture counts in core and image logs in more than 70% match.

The fracture network is then translated into fracture properties by incorporating geo-mechanical in-situ stress information including direction, magnitude, and vertical gradient to identify open fracture and to determine the effective fracture aperture. Due to high matrix permeability a representation of the matrix and strataform was incorporated with the fractures to produce a discrete feature model of the combined fracture/matrix system. This is essentially single medium model was used to calibrate against well-test data.

Single flow simulation was then performed for the discrete feature model on each of the cells in the model. The calculated fracture properties include fracture permeability, fracture porosity, and the transfer function (sigma) measuring the interaction between the matrix and the fracture.

The dynamic behavior of the simulated fracture permeability compared well to the Kh from pressure buildup tests. Results were very encouraging, as it appeared that in general, the fracture distribution in the reservoir had been properly described. Moreover, calibration of the fracture parameters such as permeability to match the observed dynamic behavior proved to be an effective way to achieve history match of both pressure and water cut, as was seen from simulation models using both dual porosity dual permeability and single porosity single permeability modeling techniques.
Challenges of Horizontal Drilling with Coiled Tubing in a Depleted, Hard and Abrasive Sandstone in Algeria
Authors: Leslie Charles , Shero Winston , Ortiz Richard , Weihe Axel
Published: December 2007

This paper discusses how the challenge to improve production from a depletedoil field in Algeria was approached using an advanced Coiled Tubing DrillingSystem. The paper covers the planning and implementation of the project anddiscusses lessons learned, results and conclusions.
Reliability Analysis Spanning Whole Well Life
Authors: Hother John A.
Published: December 2007

Reversionary Mode Analysis (RMA) was used to analyse the reliability of the whole life-cycle of a proposed well development, so that the risks associated with different well designs could be quantitatively compared. The technique combines engineering analysis and economic modelling in a systematic and rigorous way. For this project, we needed to extend the economic aspects, to match the level of detail used in the business case economics for this field development.

RMA is an innovative and powerful system analysis technique that has been adapted from its aerospace origins for application in oil and gas projects. The engineering aspects, founded on conventional failure mode analysis methods, were already well developed.

The process started with engineering analysis of the failure modes, determining cause, effect and probability. To ensure proper coverage of the whole life-cycle, RMA handles both activities, defined by process flow diagrams, and equipment defined by system block diagrams. To confirm the validity of the analysis, the estimated probabilities of failure were checked with alternative sources.

Then an economic model was produced, quantifying in financial terms the consequences of a whole range of different types of failure. The analysis software consolidated all the failure mode data with the economic model.

The results in ‘risk-Dollars’ highlighted the aspects that are critical to the project's viability, and provided a good basis for comparing different well options. The rigorous data structure provided the capability to ‘drill-down’ into critical aspects, to identify key causes for which mitigating measures were needed, which may occur at any stage in life-cycle.
Structure and Regional Context of Onshore Fields in Abu Dhabi, UAE
Authors: Johnson Christopher A. , Sattar Mohamed Abdul , Rosell Rafael , Al-Shekaili Fatema , Al-Zaabi Naema , Gombos Andrew
Published: December 2007

High quality 3-D seismic and well data allow detailed structural analysis of the major onshore fields of Abu Dhabi. Most of the large onshore fields were examined for this study. The fields are generally asymmetric anticlines with reservoir units in the Mesozoic section. All are interpreted as deepseated (probably Proterozoic) grabens and half grabens that were gently inverted to various degrees in Late Cretaceous time. The timing, distribution, and geometry of structural relief link trap formation to foreland compression during orogenesis and ophiolite obduction along the Arabian margins, particularly in Oman.

Traps are cut to varying degrees by remarkably regular sets of cross faults that grew as strain developed in more competent units during structural growth. Some traps display welldeveloped conjugate cross faults indicative of NW-SE or WNW-ESE compression. Other traps have only one set of cross faults, indicative of more oblique transpression at an angle to the underlying basement structure. On 2-D seismic data the cross faults are quite linear and often appear to cut the entire structure for distances of several kilometers. However, 3-D data reveals that the faults are actually fault zones composed of arrays of smaller en echelon faults. These observations indicate oblique offset and show that the fault zones can be interpreted as conjugate shears. Some of the faults are detached, limited stratigraphically, and their vertical offset diminishes from 10's of meters near structural culminations to zero off structure. If true for the majority of faults, this would indicate an origin related to internal strain within the fold, not a major, through-going basement shear zone. However, some faults may not terminate at the structural limbs, but instead could extend much further off structure. This, combined with possible evidence for basement involvement, would support a regional shear or wrench model. Ongoing interpretation is focused on deciding which of these models is appropriate.

The cross faults can influence fluid flow and are thus of interest from a trap segmentation and production perspective. In general, steps and relays between fault segments allow diminished fluid communication across the fault zones, but do not completely partition the reservoirs into compartments.
Analysis of Bed Height in Horizontal and Highly-Inclined Wellbores by Using Artificial Neural Networks
Authors: Ozbayoglu Evren M. , Miska Stefan Z. , Reed Troy , Takach Nicholas
Published: December 2007

Knowing the amount of cuttings that accumulate inside horizontal and highly-inclined wellbores is part of the information that is essential for controlling bottom-hole pressure, preventing stuck pipe, minimizing the circulation time for cleaning the wellbore, etc.

A dimensional analysis is conducted using basic drilling information such as pump rates, fluid densities and viscosity, drilling rate, and wellbore geometry. By using these drilling variables, three dimensionless groups (Reynolds Number, Froude Number and cuttings concentration at the bit) are developed for estimating the height of stationary cuttings beds deposited in horizontal and highly-inclined wellbores for a wide range of drilling fluids, including foams and compressible drilling fluids for underbalanced drilling.

A series of cuttings transport tests were conducted within the annular test section of Tulsa University's Low- Pressure/Ambient-Temperature Flow Loop. The test fluids included water, polymer muds and foam with a wide range of pump rates and rates of cuttings injection. The experimental data are used to develop two different models. The first model is a traditional least-squares fit of the dimensionless groups to the data. The result is an equation with four empirical constants. This equation calculates bed heights that are within 15% of measurements for all fluids. One of the disadvantages of this traditional approach is that different correlations are needed for different flow regimes, e.g., turbulent flow requires a correlation that is different from one for laminar flow.

The second model is an Artificial Neural Network (ANN) program that uses the same dimensionless groups but has been "trained" by using the test data. The ANN model predicts bed heights with an error of less than 10% over the entire range of measured data. One of the advantages of the ANN model is that it can accommodate data from all flow regimes and provide equally good results. It can also be more easily extended to include other effects such as drillstring rotation.
Application and Comparison of Two Models of Foamy Oil Behavior of Long Core Depletion Experiments
Authors: Bayon Y. M. , Coates R. M. , Lillico D. A. , Cordelier Ph. R. , Sawatzky R. P.
Published: December 2007

The behavior of gas in foamy oil is one of the key factors for the heavy-oil solution-gas-drive process. Due to the high viscosity of the oil, and the interaction between capillary pressure and viscous forces, the depressurization of live heavy oil below the bubble point causes bubbles of gas to nucleate, grow, cluster, and eventually connect into a free phase.

In this paper, two models aimed at simulating foamy oil behavior are described and compared. One model partitions the gas into three groups (solution gas, dispersed gas, and free gas), while the other distinguishes four groups (including two types of dispersed gas). In the first model, two kinetic equations for mass transfer are defined to describe how one group of gas is transformed into another, while in the second model six kinetic equations for mass transfer are proposed. Each model defines in an original way the mobility of the gas groups, which leads to different relative permeability models.

Both models were applied to two sets of long core depletion experiments with significantly different depletion rates. A comparison of the matched results from the two models is presented in this paper.
Improving Project Performance in a Heavy Oil Horizontal Well Project in the San Joaquin Valley, California
Authors: Cline Veronica J. , Basham Michael
Published: December 2007

The Tulare Steeply Dipping Horizontal Well Project is a multi-year project that is designed to recover oil by steamflooding the Tulare and Amnicola sands in the Cymric and McKittrick fields in the San Joaquin Valley, California utilizing horizontal producers and associated vertical steam injectors. The scope of the project includes ~79 horizontal wells, associated vertical injectors and surface facilities, using a staged-development for a multi-year drilling program. The average horizontal well produces about 100-250 BOPD in comparison to an average vertical well in the reservoir that makes approximately 30 BOPD. Throughout the early phases of the project, the multi-disciplinary team gained insight into improving the design and implementation of the project. Several improvement areas were identified to reduce drilling costs and enhance early oil production, which resulted in improved project economics.

The first stage of development drilled in 1997-98 included eleven horizontal wells. Although these wells demonstrated good productivity and the viability of applying horizontal producers in these fields, the overall economics were poor, partly due to high capital costs and a slow production response. During a low price environment, the team took an initiative to identify areas that would reduce costs and optimize operability for future development of the field with horizontal wells.

Some of the changes affecting costs identified were reducing the casing size in both the build and lateral sections of the wellbore, selecting a directional drilling contractor with extensive experience in the area and eliminating LWD. Operational and start-up changes included cyclic steam stimulation of the horizontal wells before placing them on production, maximizing lift, and the use of fiber-optic temperature surveys to understand heat distribution in and near the lateral. Another change later identified before drilling the next set of horizontal wells were to utilize 3-D well path planning tools to iterate plans in real time with the directional drilling contractor to meet geologic and anti-collision parameters. The eight well drilling program in 2000 resulted in a 30% reduction in both the drilling costs compared with the 1997-98 program. As a result of cyclic steaming, the wells averaged between 150-250 BOPD above forecast for the first six months of production. A third stage of development in early 2002 resulted in a 45% reduction in drilling costs relative to the 1997-98 programs.
An Alternative Water Supply for Heavy Oil Steam Generation Plants: Potential Sources of Brackish Water From the Cretaceous Mannville Group in the Cold Lake Region
Authors: Horne Emmett , Stephen Sun , Lee Nichols , Agatonovic Vlad
Published: December 2007

Heavy oil production requires large quantities of freshwater for steam generation. Currently these operations utilize surface water and shallow groundwater for supply. An alternative source of water is the brackish groundwater from basal aquifers which exist in the lower portion of the Mannville Group and below the heavy oil horizons. Hence, the term "basal aquifers" is used to describe these water bearing sediments.

Due to corrosion and precipitation concerns, source water must have acceptable salinity and Total Dissolved Solid (TDS) levels. Salinity and TDS of groundwater can be conveniently estimated from electrical logs using empirical formulae.
CHOPS in Jilin Province, China
Authors: Dusseault Maurice B. , Liang Chun Xiu , Ma Yiqiu , Gu Wu , Xu Baoci
Published: December 2007

Taobao Oilfield has been producing viscous oil (μ = 1850 mPa.s @ 18°C) with sand for several years from a fine-grained reservoir on the west flank of the Songliao Basin in northern Jilin Province, China. The practices used closely follow the approaches developed in Canada in the last 15 years, but production is from a much shallower depth (-160m) and from a field that is fault-controlled and possesses some dip, rather than being stratigraphically controlled. The reservoir is composed of unconsolidated sands with high porosity (~35%) and high permeability (5 Darcy), suggesting a good prospect for CHOPS. The aggregate thickness of the sands is about 15 m with a formation thickness of 28 m; individual layers are 1-6 m thick, with an average of 4 m, substantially thinner than the beds usually exploited in Canada. Over 75% of the oil in place is in layers less than 5 m thick.

The first well started production in Aug 13, 1997. At present, there are 71 wells producing oil in Block 87 and Block 92. A crude oil recirculating system from the stocktank is used to keep oil flowing down the annulus to prevent blockage of the well. Conventional production using progressing cavity pumps is still low, the best wells are only producing approximately 25-30 b/d, but production can apparently be sustained for as long as 16 months.

Taobao Oilfield initiated CHOPS in approximately 22 wells in Blocks Bai 87 and Bai 92. The sand cuts range from 0.1 to 10% by volume, which is a broad range for a single field, compared to Canadian experience. Water cut is very reasonable, from as low as 0% to as high as 52%, with an average of 5-8%.

The article will review the geology and the production history of the Taobao CHOPS project to date. Petrophysical parameters and reservoir properties will be presented and compared to typical Canadian and Venezuelan information. Case histories from existing developments are used to illustrate how technologies developed in Canada have allowed the difficult heavy oil fields to be developed. Finally, the future direction for this CHOPS project is discussed, aiming at improving the oil production rate and the oil recovery. It appears that production gains are possible through improvements in operational practices.
An Example of a Steam Drive Pilot Project Management With 3D Seismic Survey in Northeast Brazil
Authors: da Silveira Cursino Delson Fernando , Mynssen Ferreira Andre Luis , Ferreira Gomes Frederico Aguiar
Published: December 2007

Estreito field contains heavy oil and has been successfully cycled with steam since 1984. The first steam drive pilot was initiated in November 1998 in the standard pattern of the field.

A seismic survey to monitor the steam front was acquired six months after the pilot had begun.

This work intends to present the integration of the pilot results, the seismic survey and the numeric flow simulation as a way to manage a steam drive process.

The paper shows also the importance of 3D seismic activities to support the steam drive management in a large scale, creating possibilities of improvements and optimization.
Optimal 3-D Directional & Horizontal Wells Planning Using Genetic Algorithm
Authors: El-M Shokir E. M. , Emera M. , Eid S. M. , Waly A. A.
Published: December 2007

This paper introduces a new software that uses the genetic algorithm to give the optimum drilling depth of directional & horizontal wells in 3-D. A special penalty function, mutation, crossover probabilities, and a special accuracy of the stopping criterion were used to get the global minimum of the problem. The minimum drilling depth is achieved at the minimum values for kick-point, inclination, and angle build-up and drop-off rates. The minimum parameters reduce the dogleg severity, which in turn reduce the chances for operational problems like high torque and drag. The optimized design has been compared with the conventional design (based on trial and error method) and WELLDES program (based on Sequential Unconstraint minimization Technique) for a well drilled in the Gulf of Suez (application I) and with conventional design for a theoretical well (Application II). Results of the comparison have been validated by genetic algorithm software. The optimization model reduced the total drilling length of the two applications. This was achieved while all other operational parameters were kept within the limiting constraints and casing setting depths were taken into consideration. In contrast, WELLDES program and conventional design have some variables within their constraint limits and the casing setting depths are outside their consideration.