bluuebunny/crossref_metadata_2025 huggingface dataset:
Interference Tests in Naturally Fractured Reservoirs Under the Influence of Gas Cap or Water Influx
Authors: Al-Bemani A. S. , Ershaghi Iraj
Published: December 2007

Interference analysis in naturally fractured reservoirs can serve as an extremely effective reservoir characterization tool. Because of the conductive nature of fractures, rapid segregation of gas-oil in naturally fractured reservoirs is common place.Additionally, the upward movement of bottom water can rapidly displace the water oil contact influencing the behavior of individual wells. The purpose of the study is to address an important class of interfer-ence test where the contribution of gas-cap support or wa-ter oil contact movement can significantly affect the esti-mated parameters such as storativity and transmissivity. The theoretical framework needed to model interference re-sponse in a naturally fractured reservoir producing an oil zone overlain by a gas cap or affected by a desired outer boundary condition, including water-influx effects,is de-rived and discussed. General pressure response solutions (for the active and the observation well) are derived for a dual flow double porosity naturally fractured reservoir. Furthermore, the effects attributed to properties of indi-vidual wells such as wellbore storage and skin damage are incorporated in the general solutions and studied.

Deviations from the line source solution occur as a result of matrix, water-influx, or gas cap support to the fractured system. In case of the gas-cap effects, the deviation de-pends entirely on the contrast between fracture anisotropy parameter (λ1) and matrix-fracture interporosity parame-ter (λ), and between the total gas cap storage capacitance (1-ω1)and oil zone matrix storage (ω) for a particular radial distance between the active and observation well. On the other hand the deviation due to water-influx ef-fects depends on the distance from the boundary to an observation well.

A combination of matrix-fracture interporosity and any of the supporting systems can produce a non-uniform and extended or even multiple transition periods between the two line source solutions of a fracture dominated flow and of that of the total reservoir response.

During multiple well testing, differences between the re-sponse signal attributed to either gas cap or water-influx effects, if not taken into consideration, may be inter-preted as heterogeneity effects, or other extraneous in-terferences. Effects observed for gas-cap response, resem-ble pressure support, ordinarilly attributed to interference from a nearby injector. Both gas-cap support and slowly advancing water-influx affect interference tests with long duration.

Type curves presented in this paper improve diognostic capability of well test analysts in recognizing source and causes of pressure support in naturally fractured reservoirs.
On-Line Well Monitoring and Its Application in a South Oman Oil Field
Authors: Taylor R. D. H. , Nuttall R. C. H.
Published: December 2007

Connecting coriolis meters to rod pump controllers in a major Oman oilfield puts accurate on-line well test data on the production technologist's desk. Conventional test separator facilities have been rendered obsolete. Numerous benefits of this recent change are beginning to be realized.
New Well Testing Technology: A Portable Three-Phase Test Unit
Authors: Cary D. N. , Durrett M. G. , Al-Amir A.H. Abd Rab , Al-Nuwaigi K. A.
Published: December 2007

In the early 1980’s Saudi Aramco identified the economic advantage a multiphase well test meter could provide to their oil producing operations. Over the following years Saudi Aramco joined with Texaco to develop a tool to serve these needs.

This Multiphase Well Test Meter was installed and tested in two Saudi Aramco producing fields during 1991 and 1992. Test results, when compared to a conventional test separator, were favorable. Additional tests are underway to prove system reliability before installation in an offshore, unmanned environment.
Computer Design and Fieldwide Optimization for Gas-Lifted Wells
Authors: Lee H. K. , Liang Jun , Ader J. C. , Legget R. B.
Published: December 2007

A computer procedure and an optimal gas allocation model are presented for gas lift installation design and field wide optimization. The paper outlines the pre-design well performance analysis, system nodal analysis and the design procedure for mandrel spacing and valve sizing. It also describes the algorithm, criterion and implementation of the gas allocation model.

Examples which illustrate the computer design pro-cedure are presented. Results and production improvement after implementing the gas allocation model for the October Nubian field are also discussed.

Special techniques are discussed to accommodate changes in reservoir productivity and operating conditions. A re-design feature is presented for wells at which gas lift valves and mandrels are already installed. An economic and effective operation can be obtained through the redesign procedure. The optimal gas allocation model, which significantly improved field production, is discussed. The integrated study requires 3-D reservoir modeling, system nodal analysis and gas dis-tribution modeling.
An Assessment of Natural Fracturing in the Thamama Formation by Reservoir Surveillance
Authors: Gibson A. P. , Al Kaioumi Q. M. , El-Amin A. M.
Published: December 2007

The presence of natural fracturing in the Thamama Reservoir was postulated following its discovery in 1958. The performance of this reservoir was poorly understood being based on information gathered from a small number of well tests executed during the 1960’s and 70’s. An up to date assessment of this reservoir was sought utilising the latest reservoir monitoring technology. The objective was to confirm the existence, magnitude and orientation of any fracturing in the Thamama reservoir. A further objective was to evaluate their distribution within the zones of the Thamama reservoir. The surveillance programme included multi-well interference testing, pressure build-up testing, production logging and water saturation monitoring. It was concluded from this study that there were many small vertical fractures, predominantly located in the dense limestone intervals, which gave rise to a strongly anisotropic reservoir transmissibility.
Pulse-Test Interpretation for Badri Field
Authors: Mahmoud M. L. , Torre A. J. , Ayan Cosan
Published: December 2007

This paper shows the results of a Pulse Test conducted in Egypt's Badri Field. The test was conducted to understand the degree of hydraulic communication within the reservoir and to check a suspected fluid migration towards the nearby El-Morgan Field. The test involved 6 wells, including the active well. The pulses were created by an alternate sequence of injection and shut-in periods of 36 hours each. The resulting pressure pulses were monitored in the observation wells for 12 days.

The observed pressure responses were analyzed by history matching techniques. The analytical solution of the diffusivity equation for a homogeneous rectangular reservoir with mixed boundary conditions yielded an excellent correspondence between measured and simulated pressure responses.

The test indicated good hydraulic communication within the investigated area. It also showed that there was no leak towards the neighboring El-Morgan Field as it was previously anticipated. In addition, it was possible to determine the interwell -reservoir properties and the geometry of the area investigated during the test.

The test also suggested the presence of free gas in the upper part of the structure. This was confirmed by other sources of information.
Geometrical Characteristics and Geological Modelling of Fractured Middle East Reservoirs
Authors: Nurmi R. D. , Standen E. J. W. , Akbar Mahmood
Published: December 2007

Fracture geometry and basic characteristics (orientation, length, density, aperture, porosity) of fractures in a number of Middle East reservoirs (from Egypt to Pakistan), have been recently studied. These studies confirm that fracture orientation, distribution and characteristics important to reservoir behaviour do not vary randomly nor chaotically. Moreover, there are commonly lower densities of fractures in reservoirs than are seen in the same formations outcropping at the surface. The simple cubic models used in reservoir studies, are sometimes appropriate for reservoir studies but often more complex geometric models are needed.

The factors which determine the occurrence of natural, open, permeable fractures within Middle East reservoirs are nature and degree of folding and/or faulting, in-situ stresses, and changes in rock properties such as porosity, bedding, and lithology, especially shaliness. These geological factors can and are often already mapped in reservoir studies. By accurately defining the relationship of these various factors to the fracturing analyzed in a number wells within a field it becomes possible to extrapolate the fracture data through out a reservoir.

There is no routine direct evaluation of fracture porosity and permeability available at the present time. However, borehole imagery allows the fracture porosity and flow potential to be calculated by multiplying the fracture density and the aperture widths measured using a modelling package available on a computer workstation. The use of aperture and fracture density data to also calculate permeability (approximately the value of the fracture aperture cubed) means that fracture aperture and density are critical parameters in defining the reservoir potential of a fracture system intersected by a well bore. The observations concerning the variations of the major fracture characteristics especially aperture and density along with orientation are summarized.

The short-coming to fracture studies using either borehole imagery or oriented cores, however, is that the fractures detected may not be representative of the large-scale fracture network which will determine reservoir production. Thus, it is necessary that the geometrical characterization of any borehole data be related to geological studies (structure, stratigraphy, sedimentology, diagenesis, and geostatistics) of that reservoir.

The borehole-scale characterization and the geological modelling also need to be integrated with the dynamic testing and production data more than just compared as a type of quality control. Even when they are radically different, both sets of data may be correct. In fact, how the two types of data fit is a key to proper modelling of the reservoir.
Comparison of Petrophysical Method for STOIIP in a Refined Estimation of Fractured Basement Reservoir
Authors: Khalil M. M. , Pigaht Joerg , El Wazeer F. M.
Published: December 2007

The fractured Basement reservoir is considered as one pf the most difficult rocks to be evaluated due to its heterogeneity.

Extensive information is available in the literature concerning techniques to evaluate naturally fractured reservoirs in general. Little is known however, about approaches to calculate porosity and water saturation in fractured basement reservoirs with little or no real matrix porosity.

SUCO's Zeit Bay field is producing from the fractured basement as well as overlying sedimentary rocks. Evaluation of STOIIP in the Basement proved difficult, due to the problems of taking cores and to the low level of porosity expected in a naturally fractured rock.

This paper compares several tools and techniques used in the Zeit Bay field with a view to narrowing down the STOIIP estimation for this field. Due to the highly fractured nature of the Basement rock in this field, fracture porosity is estimated higher than usually expected in naturally fractured rocks. Core material recovered is, for the same reason, only recoverable from less fractured regions, i.e. less porous intervals. To supplement the sparse amount of qualitative core data, porosities were calculated from a comprehensive log analysis and from Formation Micro Scanner Data using a conventional approach as well as a "Fracview" interpretation.

Interpretation of the Array Sonic for the Stoneley wave is used for permeability identification.

Correlation between all available data is presented and their use for porosity or permeability estimation highlighted.

Critical comments are made on all approaches and results are shown on a comparative basis, with the view to narrowing down the porosity range for this reservoir rock.
Geostatistical Application for Exploration and Development: Porosity Estimation from 3-D Seismic Data Calibrated to Well Data
Authors: Chambers R. L.
Published: December 2007

The geostatistical external drift method is used to integrate 3-D seismic data into a reservoir description and is illustrated with an application on a west Texas Permian Basin interbedded carbonate-clastic reservoir. Seismic reflection amplitudes, calibrated to core and sonic-derived porosity data, supplements sparse well control to estimate interwell porosity.

An extensive well log and core data base was subsampled over a small portion of the field covered by a high resolution 3-D seismic survey to mimic scenarios similar to three stages in a reservoir's life: (1) a 7 well case, typical of a late exploration/early appraisal phase; (2) a 14 well case, similar to a development phase; and (3) a 55 well case (40-acre well spacing), representing a mature production phase.

Spatial interpolation by kriging porosity with and without seismic data are compared. Stochastic (Monte Carlo) simulations are used to evaluate interpolation uncertainty (standard error), a quantity not obtained from kriging. Interpolation uncertainty is greatly reduced when seismic data are integrated into the reservoir description.
Representing Fine-Scale Heterogeneities in Coarsely Gridded Models
Authors: Williams G. R. , Lockwood R. P.
Published: December 2007

An example of how fine scale heterogeneity was incorporated into a large full-field model is presented. A detailed geologic description was prepared and implemented in a 2D crosssectional model. The important heterogeneities in this reservoir were found to be shale barriers. A simple Markov method for modeling fine scale shales was developed. Stone's method for determining interblock relative permeabilites was superior to Kyte and Berry's method, in this case.
Calibration of Old Well Log Data Using a Multiwell Environment
Authors: Faqihi M. M. , Crossouard P. A.
Published: December 2007

This paper reviews the implementation of a special multiwell calibration technique to transform and normalise old well data within a petrophysical study. One problem in the evaluation of old wells is the porosity calibration of the Neutron counts. This can be achieved through a normalisation program on a single well basis if another porosity measurement such as the Sonic log is available in the same well. In the case of this study two such porosity-dependent measurements were not available and a new variable was needed to link old and new data. However, good log correlation in the field and the availability of a multiwell data base set-up allowed the use of log depth as this extra dimension.

Old data is imported into new well data and is automatically tied to them. This is done by extracting from the Multiwell Data Base the formation tops of old and new wells and by depth-shifting the old well data by an amount equal to the difference between the formation top depths. Then an auto-correlation depthmatching program using comparable curves such as old and new Gamma Rays refines the tie between wells.

Having linked the data through a common depth, a multiwell cross-plotting technique gives the best fit between old and new data. The best fit equation calibrates the old data and this is validated quickly against field trends using multiwell crossplots

To account for the different sensitivity of the GR detectors as the technology of logging tools has evolved, the same calibration technique can be applied to rescale the GR data of the old wells. This re-scaling of the GR of old wells gives the same ranges as the GR of key wells allowing the use of multiwell histogram/ estimation programs and the use of similar interpretation parameters throughout the field.

The old log data was successfully calibrated allowing their use as input to modem log evaluation packages.

For each old well the multiwell evaluation set-up gave easy calibration against one or several recent nearby wells and it ensured quality checks of the results. The technique can be used to integrate older data into a study, giving the more detailed coverage needed for reservoir characterisation and simulation work.
Customer/Supplier Cooperation: Working Together for Quality
Authors: Robins K. B. , Carlisle J. A.
Published: December 2007

This paper describes the impact on Total Quality Management (TQM) that improved customer/supplier relationships have had for a UK Exploration and Production Operator. The Drilling in the Nineties initiative introduced in early 1990 has been broadened to include well services and equipment supply areas with a resultant name change to Well Engineering in the Nineties (Win 90s). Experience has been gained with the implementation of this programme with two drilling contractors.

In E & P companies the focus for TQM improvement is invariably on the supply side, ie the well and production, unlike other industries where the focus is on the customer. Quality in E & P is thus driven, not by the end user; but by upstream (supply) pressure, for reasons of cost, safety and the environment.

The implementation of co-operative supplier strategies is increasing the demand for Total Quality Management in both supplier and customer companies.

The paper will describe how developing a co-operative relationship has resulted in a joint effort in initiating more continuous improvement activity, reducing waste and adding value.

Examples are discussed of appropriate planning and training initiatives and tools used to develop a co-operative relationship. The need for support and intervention from senior management such as modifying existing policies to support the new relationships is reviewed.

Win 90's implementation has shown that it is not the introduction of Total Quality Management with the operator or supplier individually but the integration along the supply chain which enables ‘leading edge’ performance.
A Monte Carlo Model for Pressure Transient Analysis
Authors: Baldwin D.E.
Published: December 2007

This paper describes a simple numerical model for simulating pressure behavior in petroleum reservoirs. The numerical procedure, which is based on a modification of the Monte Carlo technique, is extremely accurate and results in a significant saving in computation time over conventional finite difference methods.

The mathematical development of the Monte Carlo method and its implementation for pressure transient analysis are described in the paper. In addition, the general applicability of the method is illustrated by test cases involving a variety of pressure transient problems.

Introduction

Monte Carlo, or random walk, methods for solving partial differential equations are well known partial differential equations are well known and have been in use for over sixty years. Although the methods are simple and offer a number of advantages over conventional finite difference techniques, they suffer from excessive calculation time and the inaccuracies associated with probability sampling, A recent modification probability sampling, A recent modification of the classical random walk technique, known as the Exodus Method, has eliminated many of the computational disadvantages associated with Monte Carlo methods and has made them an attractive approach to the solution of certain classes of problems. In particular, pressure transient problems, where solutions are required at a selected point rather than over the entire finite grid system, are admirably suited to this technique.

This paper details the development and application of the Exodus Method for transient analysis and presents the results of computational experiments which were performed to evaluate the effectiveness of the resulting numerical model.

MODEL DEVELOPMENT

The flow of a slightly compressible fluid in a porous medium of non-uniform permeability is porous medium of non-uniform permeability is governed by the following equation:

(1)
Building a Drilling Partnership
Authors: McKee J. D. A. , Brandt W. H.
Published: December 2007

A movement away from conventional day rate contracting towards partnering and closer customer supplier relationships has been initiated with the advent of Well Engineering in the Nineties (Win 90s). This initiative is changing the traditional role of the drilling contractor and the drilling service companies. The drilling contractor will become the lead contractor for the provision of drilling services, and together with it's subcontractors will assume more control, accountability and risk associated with the drilling operation. As these responsibilities are handed over, the performance of the operator will become critically dependent on the performance of it's suppliers, and the development of a partnership between the operator, drilling contractor and drilling service companies with close customer supplier relationships and sound supply chain management will assume greater importance.

This paper describes how a drilling contractor has assumed the role of lead contractor and is developing long term, co-operative relationships with preferred service companies to provide a drilling service for Win 90s operations. The paper discusses the contract structures, procedures for selection of suitable service companies, and how to develop a business process plan for managing the changes to the drilling process. Integrating the services and the application of incentives to focus on the operator's needs is also addressed. It also examines the progress to date in implementing the new contracts and the business process plan, and summarises the successes and failures of the work so far.
Safety Management at Start-Ups is Key for Short-Term Drilling Contracts
Authors: Lievre Thierry
Published: December 2007

A fall of the drilling activity and a shortening of the drilling contracts were experienced during the past few years, in both offshore and on land activities throughout the world, ranging from European to desert areas. These together with the development of integrated services and turnkey contracts have had a considerable impact on the responsibility for safety by the drilling contractor. Furthermore, the safety management systems have become more sophisticated and the expectations-from all parties-for safety performances have increased. The assistance of safety professionals has become necessary on site to enable the application of this developing expertise and accomodate the additional workload. Their role must now be considered to be a primary component to the safety organisation.
A Simple Correlation To Predict the Hydrate Point Suppression in Drilling Fluids
Authors: Yousif M. H. , Young D. B.
Published: December 2007

Gas hydrate formation during deep-water offshore drilling is a well recognized operational hazard. At water depths in excess of 1000 ft[305 m], the sea-bed ambient conditions of pressure and temperature become conducive for hydrate formation. This can impose serious well control difficulties during the containment of a gas kick.

Salts and glycerol are the main hydrate inhibitors commonly used in water-based muds. To determine the required salt and/or glycerol concentration for a particular drilling fluid, costly and time consuming experiments are required.

This paper presents a simple correlation to predict the hydrate point suppression using mixtures of salts and glycerol. The correlation is based on rigorous thermodynamic principles and represents a substantial improvement over Hammerschmid's correlation. Example calculation is provided on how to utilize the proposed correlation.
The Design and Operation of the Support System Required To Operate a Cantilever Jackup in the Skidoff Mode for Tender-Assisted Drilling
Authors: Springett C. N. , Hinton R. O.
Published: December 2007

Using a jack-up in the tender assist mode is not new. It has been done by several contractors in different parts of the world. It has become increasingly attractive from a cost standpoint in the Central North Sea and has been proposed for production drilling on a number of new developments. Cantilever rigs of newer design, while having greatly increased water depth capability and highly rated drilling equipment, do not lend themselves to easy conversion to the skidoff mode of operation as do the older slot type rigs.

This paper describes the approach that has been taken by Santa Fe in developing a system that is not only usable with any of their four new North Sea harsh environment rigs, but which will be compatible with the widest possible range of production platforms. The paper also focuses on the need for maximum flexibility in installation techniques. The transition structure (skidbase) supporting the drillfloor can be erected using a derrick barge, using rig cranes, using platform cranes or installed on the jack-up while in sheltered waters and skidded in one piece onto the platform. The unique capability of the resulting system is that it is fully self contained, complete and self erecting, all that is required of the production platform is two parallel capping beams with spacing less than 60 feet (18 metres). The paper is of wider interest and application in that it provides a blueprint for the conversion and outfit of virtually any cantilever jack-up to the tender assist mode.
Enhanced Drilling Efficiency through Operator/Contractor Cooperation
Authors: Cole J. C.
Published: December 2007

An innovative management structure utilized by Shell Offshore Inc. for the Auger predrill program permitted a close-working relationship between the various departments at Shell, Sonat Offshore Drilling Inc. (the drilling contractor), and the third party service companies. The result was a substantial improvement in drilling performance and a large increase in the scope of work completed during a 29-month period.
Use of Drilling Parameters to Predict In-Situ Stress Bounds
Authors: Hareland Geir , Hoberock L. L.
Published: December 2007

This paper reports theory, procedure and results on the use of drilling parameters collected during typical drilling operations to predict bounds on minimum principal in-situ stress of rock. These predictions are desired in order that hydraulic fracturability of reservoir rock can be better determined and fracturing programs designed without the need for expensive fracturing stress tests, guesswork, or empiricism. A high fidelity tri-cone roller bit drilling model is used in an "inverted" mode to predict in-situ ultimate compressive rock strength. This compressive rock strength is a function of effective confining pressure available from published laboratory data for various rock types. Knowledge of the compressive rock strength failure as a function of confining pressure can be used to obtain the Mohr failure envelope at a given depth for rock. The angle of internal friction is determined from the Mohr failure envelope, which can be used to calculate a "coefficient for earth at rest." This coefficient, together with known overburden and pore pressure, can be used to calculate an upper bound on the minimum horizontal stress for each foot drilled. The calculated in-situ stress bound profiles are compared, with good results, with experimental field closure stress data obtained in 46 tests in four GRI (Gas Research Institute) wells, SFE (Staged Field Experiment) wells #1,2, 3, and 4.
Power and Quality: Two Approaches to Service Company Support for the North Sea Oil Industry
Authors: Krahn D. R.
Published: December 2007

This paper examines 21 middle tier offshore service (SSSCM) firms. Three models explore their difficulties and suggest ways forward. First is Porter's Model of the CompetitiveEnvironment;second is J.K. Galbraith's Model of Countervailing Power; and third is a Composite Quality Model based on Deming, Juran, Crosby, and Feigenbaum.
Drilling in the Twilight Zone: Somewhere Between Dayrate and Turnkey
Authors: De Wardt JD. P.
Published: December 2007

Dayrate contracts have been the normal mode for drilling operations for a long time. The environment is well known and therefore comfortable to the participants. The operator retains control over all aspects of the operations; essentially the operator leases men and equipment.

Turnkey contracts have been regularly utilised in the USA and have been used to a limited extent internationally. In their simplest and purest form they provide an understandable and usually clear assignment of responsibility to the contractor.

Dayrate contracts provide little incentive to perform, are professionally unrewarding to contractors' personnel and presently do not offer a profitable return on investment in most sectors.

Turnkey contracts, by contrast, provide a significant incentive to perform, are professionally rewarding to contractors' staff and can provide an environment whereby the contractor achieves a more profitable return on investment whilst the operator reduces well costs. Unfortunately, the application of the non variable turnkey contracts used today has been limited due to their inability to handle uncertainties and a reluctance of the industry to adopt this form of contracting.

As a result a significant movement has arrisen towards contracts which fall between the well known dayrate situation and the non variable turnkey.

This is the twilight zone – an ill defined region of major contrasts in control, responsibility, accountability and price. A region which requires thought and development to provide the mechanisms for successful contracts. A region through which the way forward to more meaningful contracting is being developed. The structure and orientation for contracting drilling operations in the twilight zone is developed in this paper.
Applying Short-Radius Horizontal Drilling to a Deep, Hot Reservoir in the Mubarek Field
Authors: Simpson W. A. F. , Spilsbury Paul , Ali I. H. , Hargreaves Christopher
Published: December 2007

The world's deepest short radius horizontal well was drilled by Crescent Petroleum in their offshore Mubarek Field in the second quarter of 1992. The reservoir objective was the Thamama formation which is a deep, hot, fractured limestone containing a sour gas condensate.

The well was built to horizontal at 14,115 ft TVD and over 1000 ft of the Thamama reservoir was drilled in 5-7/8" hole using short radius drilling equipment and a mixed metal hydroxide drilling fluid. The well was drilled without any major problems and a 3-1/2" perforated liner run to TD successfully.

This paper discusses the operational planning for the well including the reasons for the choice of short radius technology, the planning considerations for its application in this harsh environment and the selection of the mud system for use with the short radius motors at the high bottom hole temperature encountered in the Thamama reservoir.

A history of the overall drilling operation is discussed. The success of the short radius equipment and the mixed metal hydroxide mud system is evaluated and their performance, interaction and limitations are addressed. The problems encountered while drilling are considered and possible solutions or procedural changes which will improve performance in future wells are presented.
A Large Volume Computer System for Digitized Well Log Data
Authors: Lindseth Roy O.
Published: December 2007

A geological well data handling system has been developed to retrieve, edit, process and display processed digitized log data in a matter of which frees the user from any routine data handling considerations. The user may collect data and submit it to the system. From that point on processing can be handled by merely processing can be handled by merely describing the location and type of data to be analyzed and the functions to be performed on the data. The system ensures the data is in the file, that it is correct, and will submit it to the requested processing procedures and display it on processing procedures and display it on some appropriate form. The system places heavy emphasis on visual places heavy emphasis on visual display. Virtually every program attempts to display the output in some form of integrated visual pattern. pattern. Digitized log data is the normal input to the system. Editing procedures examine the data for rational procedures examine the data for rational values and will indicate where data errors may exist. A preliminary analysis calculates a set of parametric statistics which aid in parametric statistics which aid in determining the quality and nature of the input data. Extensive editing is done on the data to ensure that the basic information is reliable within obtainable limits. Erroneous data is often the true culprit for many problems which at first glance appear to be hardware or software in nature.

In a typical operation some 200 wells containing roughly 1.5 million feet of digitized log are manipulated through fifty programs. Segments of the log file meeting prescribed logical conditions may be subject to analysis and the output displayed on a machine contoured map. The modular nature of the system allows successive operations to be performed in any desired order. The output of many routines is placed in a format similar to the digitized log input so that results of operations may be operated on by succeeding programs in the same manner as log data.
Use of Variable Stabilizer in Horizontal Wells
Authors: Kristiansen Egil , Jones R. D. , Eriksen T. J.
Published: December 2007

This paper outlines the background, concept, preplanning, supervision and achievements made by use of variable gauge stabilizers in rotary drilling of horizontal wells. The experienced performance and behavior of PDM motor versus the variable gauge stabilizers are reviewed. The requirements and ability to drill at high penetration rates over long hole sections and with small vertical targets still being able to control the vertical depth within a target limit of ± 2.0 m are shown feasible. Examples from the Oseberg field will show results of the drilling operations including drilling parameters, BHA's, ROP, hole trajectory, torque and drag during the drilling and results of the consequent setting and cementation of pipe in the horizontal section.

The conclusions are; (1) rotary drilling of horizontal section gave higher ROP (m/hr), (2) inclination was satisfactory controlled with a variable gauge stabilizer over a horizontal section of 174 m, eliminating several trips and (3) this technique will enable vertical tolerances of horizontal wells as narrow as ± 1.0 m over long horizontal sections, even at high penetration rates.
Biodegradation and Drilling Fluid Chemicals
Authors: Bland R. G. , Clapper D. K. , Fleming N. M. , Hood C. A.
Published: December 2007

Biodegradability testing of drilling fluid chemicals is becoming a requirement for use in Europe, due in part to the persistence in the environment of the oils attached to discharged cuttings from oil-based drilling fluids. This paper defines some pertinent terms, presents a brief discussion of aerobic ready biodegradability testing based on the methods published by the Organization for Economic Cooperation and Development (OECD) and presents results and experiences from using an OECD proposed seawater closed bottle test procedure to screen hydrocarbon oils and alternatives for their potential marine biodegradability.
Vertical Drilling Technology: A Milestone in Directional Drilling
Authors: Chur Claus , Oppelt Joachim
Published: December 2007

The Continental Deep Drilling Program of the Federal Republic of Germany (KTB) is a fundamental research project to investigate the physical and chemical conditions and processes in the deep continental crust. To meet the geoscientific goals, it is necessary to drill an ultra deep borehole with a target depth of 10000 m.

To reach this depth safely it is necessary to minimize the drag and torque for the drill string as well as the loads on the casing strings. Therefore a unique drilling concept has been set up including the application of automatic Vertical Drilling Systems (VDS).

The latest development VDS-5 has an external negative steering device. Sensors, electronics, electric power supply and all hydraulic and mechanical parts are designed for an operating temperature environment up to 200°C (390°F) or a depth equivalent to 8000 m.

Applying the vertical drilling technology an average borehole inclination of less than 1° could be maintained under a foliation dip of about 60°. At a depth of 6700 m the horizontal displacement was only 4 m. Drag forces could be kept to values less than 120 kN.

Drilling results from more than 80 runs with the vertical drilling systems are reported.

These results promise various options for further development, such as an automatic closed loop drilling system for general directional drilling applications. This system could be steered either along a preprogrammed well course or with the incorporation of formation evaluation sensors, working in formation boundaries.
Surge Field Tests Highlight Dynamic Fluid Response
Authors: Wagner R. R. , Halal A. S. , Goodman M. A.
Published: December 2007

This paper presents actual surge and swab field data during tripping and circulating operations which include both surface and downhole measurements. These data are compared with a dynamic surge model which includes the effects of fluid inertia and compressibility, wellbore elasticity, axial elasticity of the pipe, and temperature dependent fluid properties. The transient response of measured downhole pressure, surface pump pressure, return fluid flow, and hookload are compared with the model and interpreted. The data clearly show dynamic and inertial effects not anticipated by conventional practices but predicted by the model.
Case History of Steam Injection Operations at Naval Petroleum Reserve No. 3, Teapot Dome Field, Wyoming: A Shallow Heterogeneous Light-Oil Reservoir
Authors: Olsen D. K. , Sarathi P. S. , Hendricks M. L. , Schulte R. K. , Giangiacomo L. A.
Published: December 2007

This paper summarizes the steam injection operations of the Naval Petroleum Reserve No. 3 (NPR-3), Teapot Dome field, Wyoming, a federally owned oilfield, located about 35 miles north of Casper, Wyoming. More than 24 million barrels of oil has been produced since initiation of production in 1922; more than 15 million barrels has been produced since full production began in 1976. The Shannon sandstone is the shallowest (350 to 500 ft) and most productive of nine producing zones and accounts for 55% of current production. The Shannon, composed of the Upper and Lower Shannon sandstones, was deposited as an offshore bar where bar margin, inter bar and bioturbated shelf sandstones are the reservoir. The reservoir is faulted and extensively fractured, with the two sandstone intervals separated by shaly non-productive siltstone. Maximum gross sand thickness is 100 ft with an average porosity of 18% and 63 mD air permeability.

Since only 5% of the Shannon's 144 million barrels of original oil-in-place was estimated to be recoverable by primary means, a study of recovery technologies was conducted in 1980 resulting in implementation of a polymer-improved waterflood pilot and an in situ combustion pilot in 1981. The polymer pilot was unsuccessful, while the in situ combustion pilot was considered a technical success although marginally economic. Favorable response to steam preheating in the in situ combustion pilot led to the development of a steamdrive pilot in October 1985. Favorable response in the steamflood pilot led to recent rapid expansion. Currently 150 acres are being flooded using five 50MMBtu/hr steam generators. The history of the steamflood has been reviewed in an effort to document successful application of steamflooding in a shallow, very heterogeneous, low-permeability, light oil (32° API gravity) reservoir which defies conventional screening criteria.
Evaluation of a New Method for Steamflooding Multisand Reservoirs
Authors: Kumar Mridul
Published: December 2007

A novel method of simultaneously processing two sands using a single injection string (the "checkerboard" injection scheme), in which adjacent pattern injectors are completed alternately into upper and lower sands, is evaluated numerically. The new scheme is compared with two others: (1) the conventional "sequential" injection and (2) the case where steam is injected into the lower sand only and the "hot-plate"-heated upper sand is drained by gravity alone.

Results show that the checkerboard injection scheme is superior to the sequential for a constant oil and gas price scenario. It results in accelerated production and has lower completion costs. However, the sequential scheme results in the highest recovery. The checkerboard scheme may be especially useful in situations where acceleration of oil recovery may be desired or when the steam injection period may be limited by external constraints. Oil production from the heated upper sand by gravity drainage alone results in the lowest recovery and is not recommended (unless steam injection in the upper sand is uneconomic). Results also show that, for this nondipping reservoir, a significant amount oil is recovered from heated areas outside the pattern boundaries.
Comparison of Thermal EOR Processes Using Combinations of Vertical and Horizontal Wells
Authors: Sarkar Avik , Deo M. D.
Published: December 2007

A comparison of three thermal EOR processes; SAGD (Steam Assisted Gravity Drainage), HASD (Heated Annulus Steam Drive) and CYS (Cyclic Steam Stimulation), has been made using a three dimensional thermal simulator by employing a combination of vertical and horizontal wells. Reservoir characteristics and thermal and fluid properties were maintained identical for process comparison. A 10-year project-time study was undertaken for CYS with vertical wells, CYS with horizontal wells, HASD with horizontal HAS pipe and aligned vertical injector and producer, HASD with offset vertical producers, and SAGD with horizontal injector and producer. The effect of reservoir heterogeneities on process performance was also examined. CYS vertical performed significantly better than CYS horizontal both in terms of cumulative % OOIP recovery and SOR. HASD recovered more oil, though the initial production rate in HASD was low. SOR in HASD was, however, very unfavorable (more than twice that of CYS vertical). HASD with offset wells made both SOR and % OOIP recovery more favorable. SAGD had better SOR than HASD; however, it recovered about half the oil recovered by HASD at the end of ten years. An unfavorable heterogeneity feature (low permeability layers or barriers) affected the recoveries and SORs for the horizontal well processes more adversely than vertical well processes.
Conformance Evolution during Cyclic Steam Stimulation in Cold Lake Reservoir
Authors: Wu Ray S. , Kry P. R.
Published: December 2007

Two observation wells, both instrumented with casing external thermocouples and one instrumented with casing external pressure transducers, were located 11 m and 25 m from a Cyclic Steam Stimulation well. The closer well was installed after 2 cycles of Cyclic Steam Stimulation and showed that the areal heated zone conformance changed little over the next several cycles. Most of the production was supported by increases in vertical conformance. The second well was installed after 5 cycles of Cyclic Steam Stimulation and demonstrated that non condensible gas saturation in later cycles controls the distribution of steam before the highest injection pressures are reached.
Development and Application of Pseudo-Functions for Reservoir Simulation To Represent Shear Failure During the Cyclic Steam Process
Authors: Ito Yoshiaki , Settari Antonin , Kry P. R. , Jha K. N.
Published: December 2007

The steam stimulation process is a proven, commercially viable recovery process in oil sand reservoirs. However, uncertainties remain in the analysis of the recovery mechanism of the process. One of the important aspects is the nature of shear failure created by pore pressure increase in the reservoir during steam injection. The changes in mass and heat transport properties in the heterogeneously deformed failure zone have been shown to be major factors affecting the recovery mechanism. This paper describes the theoretical and practical aspects of representing the shear failure sone in reservoir simulation, by means of pseudo relative permeability functions.

Relative permeability hysteresis is commonly used in the simulation of the steam stimulation process. The paper gives the theory for the pseudo relative permeabilities caused by heterogeneously failed media. The new functions are derived by considering the shear failure phenomenon and have a characteristic similar to relative permeability hysteresis. A set of stress-dependent pseudo relative permeabilities is proposed and a practical method for the use of the pseudo functions (including hysteresis) in a reservoir simulator is given. The pseudo relative permeability model is applied in the simulation of a well in the Esso Cold Lake site and shows that the hysteresis should be stress-dependent rather than saturation-dependent.
Stability of Conventional and Ceramic Gravel Park in Well Associated to an EOR
Authors: Alcocer C. F. , Toups M. , Hayatdavoudi A. , Okoye C. U. , Ghalambor Ali
Published: December 2007

The main objective of this research was to determine the effects of elevated temperatures on the size and shape of gravel pack materials, specifically as related to the generation of fines within the gravel pack itself. These objectives were achieved by examining 20/40 and 40/60 mesh samples of subject materials for the influence of various temperatures (room temperature up to 500°F). SEM photographs of 40/60 mesh gravel indicated an increased amount of pits caused by temperature. Also, the formation of striations and/or flaking were present on the 40/60 mesh gravel.
Stress Changes in Thermal Operations
Authors: Dusseault M. B.
Published: December 2007

Large-scale fracturing, fire floods, or hot water injection can alter principal stress magnitudes (σ1,σ2,σ3) and directions, even at the reservoir scale. In fracturing, this leads to changes in fracture orientation (Dusseault and Simmons, 1982); in firefloods, stress changes lead to yield and microseismic emissions, impairment of reservoir seal, and well loss through shear (Dusseault et al., 1988); hot or cold water injection can induce shear failure or tensile stress zones around the injection borehole (Hojka et al., 1993). Pore pressure changes also alter total and effective stresses (σ, σ’), and sand production or sand injection will lead to reservoir-scale stress changes (Dusseault and Santarelli, 1989).

This article addresses stress changes during thermal operations. Thermal loading is often a non-linear problem because reservoir response is modified:

principal stress fields are rotated and altered; volume changes occur and stresses change; yield and dilation of the reservoir occurs; absolute and relative permeability changes because of dilation and saturation alteration; bounding strata properties may be affected by tensile cracking or shear yield; and, overburden or reservoir shearing develops because of high pore pressures, thermal stresses, and weakening due to yield.
Surface Control on Thermal Front Movement in Fireflooding Process
Authors: Diyashev R. N. , Galeev R. G. , Kondrashkin V. F. , Shvydkin E. K.
Published: December 2007

This paper presents some data about heavy oil and bitumen reservoirs in Tatarstan (Russia), methods and results of surface magnetic and electric survey with the purpose of determination the burned and heated zones of formation as well as in-situ combustion front movement. Information receiving helps to increase sweep efficiency during the process.