bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Evaluation of Key Liner Cementing Variables on Cement Bonding
Authors: Saleh S. T. , Pavlich J. P.
Published: December 2007

This paper presents field evaluation results of several key variables which affect liner cementing performance in deviated and horizontal wells. The investigated variables are: displacement flowrate, cement slurry rheology, turbulators placement, and back pressure. These variables were identified based on several years of database development and analysis in the Prudhoe Bay field (PBU) in Alaska. The development of successful liner cementing practices has increased liner cementing success to 90% based on well log evaluation and production history. The results of the comprehensive field experimentation along with laboratory testing are presented.

An efficient centralization program with turbulators has evolved based on field data and experimental results derived from a flow loop model. The flow loop allowed visual observations of turbolator's effectiveness under different flow conditions. The emerging turbulator placement program was field tested and evaluated. Operational considerations and hole condition prior to cementing are discussed. Caliper logs and cement bond logs were correlated and showed the detrimental effect of hole washout on cement bonding.

Back pressure application immediately after cement slurry placement was evaluated experimentally. The experimental results supported field data, which concluded that back pressure helped prevent gas migration and obtain a better cement bonding.
Case Histories: New Horizontal Completion Designs Facilitate Development and Increase Production Capabilities in Sandstone Reservoirs
Authors: Harrison R. D. , Restarick Henry , Grigsby T. F.
Published: December 2007

Premature water breakthrough and sand production are problems that have plagued operators worldwide in the development of sandstone reservoirs. In many cases, these difficulties have limited the productivity of sandstone reservoirs to such an extent that operators have ignored recoverable reserves, considering them to be economically unfeasible. Today, however, horizontal technology can offer operators a viable sand control completion technique to address these issues; its capabilities of reducing formation damage by decreasing production flow velocities and drawdown pressure across the production zones while reducing the water content provides solutions to many basic sand control problems.

As demonstrated by the successes recently achieved using this technology, horizontal completions have dramatically changed operational outlook for both new wells and recompletions in a sandstone environment.
Southeast Lost Hills Hydraulic Fracturing Stimulation of the McDonald Shale Zone: Case History
Authors: Martinez A. D. , Marquez M. R. , Knauss M. E. , Shotts K. D.
Published: December 2007

This paper is a case history of the hydraulic fracturing stimulations applied to the McDonald Shale (MS) zone in the Southeast Lost Hills (SELH) Field located in Lost Hills, CA. Approximately 25 wells have been stimulated in this naturally fractured, low permeability (.07 md), thick (+ 200 feet) reservoir since 1982. Hydraulic fracture treatments have been refined to their current design.

Approximately 65% of the wells fracture stimulated in this zone have screened out. Several design changes have been implemented which have proven successful in preventing screen outs and resulted in placing designed treatment volumes. These changes include ramping vs stair step proppant schedules, the use of higher viscosity gel pads, and smaller perforation density.
Drilling Faster and Cheaper With Dayrate Contracts in the Texas Panhandle
Authors: Riker J. E. , Reynolds G. D. , Westermark R. V.
Published: December 2007

This paper discusses changes made in drilling practices in the Texas Panhandle resulting in increased penetration rates and less cost per foot.

Most drilling in the Texas Panhandle has been left to the drilling contractor on footage contracts. To implement ideas for improvement it was necessary to have control over the drilling operation. A change from footage contract to daywork contract was made on one rig.

Surface modifications were made to meet safety and well control standards. The mud system was modified with an additional pit and an independently driven triplex mud pump. An inspection program was initiated for the drill string.

By utilizing low solids mud, aggressive weight and RPM on new bit designs, and increased annular velocities, penetration rates have been substantially increased and cost per foot decreased.
Case History of Live Storage Cavern Snubbing Unit Work Where 100,000 bbl of Butane Were Recovered
Authors: Endacott M. S. , Buntt J. W.
Published: December 2007

The purpose of this paper is to provide a case history of methods used to work on an underground storage cavern containing butane. This refined product had become trapped behind the casing set point. The product was recovered using a mechanical casing cutter and a snubbing unit.
Determining the Integrity of a Pipeline by Hydrotesting
Authors: Lenhoff D. A.
Published: December 2007

One of the key methods used in determining the integrity of an existing pipeline is hydrotesting. Prior to commencing hydrotest procedures, research data such as original resurvey plats, pipeline reports, failure reports, and topographic maps are compiled to profile the pipelines characteristics. Based on this information, a practical test pressure for an unregulated pipeline can be determined by using ASME B31.8,"Gas Transmission and Distribution Piping Systems". During hydrotesting, failures resulting from metal corrosion must be anticipated so that appropriate safety and repair preparations can be undertaken. Repair of failures requires a systematic approach including the calculation of the length of piping to be replaced, development of a process by which test water from one section may be transported to another without undue delay in operations, and development of a cost effective means of test water disposal. Although hydrotest has been proven to be an accurate and dependable gauge of line integrity, the process is not yet fully defined and improvisation is still necessary to optimize both efficiency and accuracy of results.
Use of Least Squares To Estimate Gas-Well Gas Recoverable Reserves and First-Year Gas Production
Authors: Iledare W. O.
Published: December 2007

This paper presents a statistical model of the natural gas depletion process1. The model is developed to estimate gas-well recoverable reserves and predict first-year production rate in a typical mature petroleum basin in the U.S. Our empirical results suggest that we can estimate, using least squares approach, new gas-well gas recoverable reserves and predict its first year production using our knowledge of the well's absolute open flow potential and the prevailing wellhead natural gas prices. Our results also suggest that we have no strong statistical evidence to reject the null hypothesis that per gas-well recoverable reserves and first-year gas production increase with wellhead natural gas prices. Given a set of geologic conditions, we utilized the model to determine the sensitivity of gas-well reserves and first-year production to changes in wellhead prices.
Hydrates: Significance for Design and Operation of Multiphase Pipelines
Authors: Fadnes F. H. , Schei R. S. , Majeed A. I.
Published: December 2007

This paper describes the hydrate prevention concept for an actual North Sea subsea development, and how this concept was established.

Based on the outline of the development, an extensive program of hydrate characterisation tests was performed. These tests consist of semi-static experiments in visual high pressure PVT-cells and dynamic studies in pressurised flow loops and flow simulators. Special emphasis has been put on the investigation of the potential of hydrate blockage and the future use of unconventional hydrate inhibitors.
Technical Integrity and Continuous Improvement: Key to Survival Beyond the Nineties
Authors: Thorogood J. L.
Published: December 2007

Drilling decisions made before a rig reaches location make a significant contribution to an oil company's financial success. Of value to the company is not the ability to drill wells, but the ability to plan with confidence in the knowledge of what is possible. In spite of this, operators have tended to over-work day to day decisions about drilling out of proportion to their significance. Recognition of this fact has resulted in the present wave of contracting initiatives. A major challenge for the industry is to achieve the necessary transfer of responsibility without compromising the operator's licence to operate. These changes will compel the service sector to develop a new culture of technical integrity and continuous improvement. To operate safely, measure performance and manage drilling risk, the transformation will oblige the service sector to adopt many technologies presently owned by oil companies.
Rock Mechanics Aspects of Drilling and Completing Highly Inclined Wells in Weak Formations
Authors: Morita Nobuo , Whitebay Lee
Published: December 2007

This paper reviews how rock mechanics concepts may be used to predict borehole stability during the drilling and production phases of field development. Cases are presented to illustrate the impact of in-situ stresses on drilling, completion, and production operations. The stability of highly inclined or horizontal wells is greatly influenced by rock strength and the effective vertical stress; which increases as the pore pressure in the reservoir drops. Factoring rock mechanics data into reservoir development plans can potentially save millions of dollars by reducing drilling and completion costs, and earn additional revenue through having more productive wells.
Misunderstood or Overlooked Gas-Lift Design and Equipment Considerations
Authors: Winkler H. W.
Published: December 2007

Gas-lift (GL) installation design calculations and examples are presented in GL manuals, text books and other publications. Example calculations range from very simplified to detailed designs requiring accurate well information and gas-rate throughput performance for the gas-lift valves (GLV's). Unfortunately, the actual GL installation does not always operate as predicted. Certain wells will require more injection gas and produce less fluid than the other wells in the same injection-gas system. The poorer performing wells have the same fluid properties and may have similar or better productivity characteristics. The objective of this paper is to discuss several design and operating procedures that can prevent unloading a well, lead to heading and surging, and other considerations that cause excessive injection-gas usage and lower than predicted production rates.
A Multiphase Pump Application in a Low-Pressure Oilfield Fluid-Gathering System in West Texas
Authors: Oxley K. C. , Shoup G. J.
Published: December 2007

A multiphase pump (MPP) application in a West Texas field is discussed. The paper describes the original production system and explains the factors limiting production. Several competing concepts for increasing production are compared including a gas gathering system, separation and single-phase pumping/compression, and multiphase pumping. The paper gives a brief history of the multiphase pump project, including performance testing before installation, installed performance, response of the production system to the pump, and long-term goals of the project.
Scale Inhibition in Wellbores
Authors: Crowe Curtis , McConnell S. B. , Hinkel J. J. , Chapman Ken
Published: December 2007

Adsorption is considered the primary mechanism of scale inhibitor retention during squeeze treatments of sandstone formations. Steps are often taken to avoid inhibitor precipitation for fear of formation damage. In limestone and dolomite formations, phosphonic acid inhibitors are deliberately allowed to react with the formation and precipitate as the slightly soluble calcium salt. This can result in longer scale protection times. Even neutralized inhibitors react with limestone to form precipitates.

This paper investigates the factors that affect the inhibitor precipitation and retention in carbonate formations. Core tests show an absence of damage during inhibitor injection but good retention. A slow rate of inhibitor return is observed during brine backflow. In formation brines containing Ca++, inhibitor dissolution is slowed by the common ion effect.
Deepwater Activities Offshore Brazil: Evolution on Drilling Technology
Authors: Barcelos André , Awad S. P. , Assunção R. B.
Published: December 2007

Petrobrás started drilling deep water wells offshore Brazil in the mid-eighties. Nowadays, after ten years of experience, 180 wells have been drilled in water depths ranging from 400 m to 1800 m. Several records have been broken since the Marlim Field Pilot System came on stream. Recent activities and new prospects are pushing on limits into even deeper waters, where Petrobrás is committed to drill and produce wells in the near future.

This paper addresses main problems faced in the Campos Basin area, southeast Brazil, during the deep water exploratory program and the solutions achieved to solve them. A a brief description of the current field developments is also given. Finally, a point about the future challenges to be overcome is made.
Influence of Composition and Texture on the Failure Properties of Clastic Rocks
Authors: Plumb R. A.
Published: December 2007

New relationships are identified between the composition and texture of clastic rocks and their Coulomb failure parameters, unconfined compressive strength and friction angle. Rocks examined in this study have porosities that vary from 0% to 40% and the volume fraction of clay minerals varies from 0% to 72%. Results show that unconfined compressive strength depends on porosity, clay content and the degree of cementation. Young's modulus was found to be a better indicator of unconfined compressive strength than porosity. Friction angle depends on porosity, clay content and effective confining pressure. These results indicate that measurements of porosity, clay content, cementation and in-situ stress are required to evaluate strength variations among rocks typically encountered in a single well.
Measuring Compaction and Compressibilities In Unconsolidated Reservoir Materials Via Time-Scaling Creep
Authors: Dudley John W. , Myers Michael T. , Shew Roger D. , Arasteh Mike M.
Published: December 2007

A testing procedure and analysis method is proposed that gives compaction and compressibility data that are independent of test duration for unconsolidated sands. Compaction data on unconsolidated sand material (including several Gulf of Mexico reservoirs) using this method are presented. Tests on twin plugs give essentially the same stress-strain data for test durations from 1 day to three months. This occurs because of a fundamental time-scaling property of these unconsolidated materials. The creep behavior is modeled using a fractional power law dependence with time, which represents the Voigt material model having an extremely broad distribution of relaxation times. This analysis indicates that the characteristic relaxation times of these materials are measured in decades or longer. ‘Creep equilibrated’ tests are therefore impractical and not relevant to a reservoir that will be depleted in one or two decades. Analysis of the power law creep parameters indicates the creep behavior is consistent at higher stresses among the materials tested. The creep parameters scale with stress and provide a means of decoupling the time-dependent behavior from the stress-strain behavior.
Basin scale rock mechanics: Logs and core measurements
Authors: Marsala A. F. , Ragazzini G. , Meazza O. , Brignoli M. , Santarelli F. J.
Published: December 2007

The Northern Adriatic basin contains a great number of developed fields at depth ranging between 1000 and 4000 meters, and a comprehensive geophysical, petrophysical and mechanical characterization of these weakly consolidated formations was carried out. For 15 wells cored in the pay zones, a systematic campaign of core measurements was undertaken and comparison between logs and cores made. Typical log programmes contained porosity, gamma ray, resistivity and sonic, including full waveforms and dipole. In the laboratory typical core measurements consisted of density, porosity, permeability, residual oil saturation, formation resistivity factor, granulometry, clay content, ultrasonic velocity measurements along with triaxial and oedometric tests. Empirical correlations and statistical analysis of this entire database at the scale of a geological unit is presented.
Relationship between frictional strength and fault gouge generation from direct shear testing under constant normal displacement control
Authors: Crawford B. R. , Smart B. G. D. , Ngwenya B. T.
Published: December 2007

The production of frictional wear debris (fault gouge) under optimum non-dilatant conditions conducive to maximum dynamic fragmentation has been undertaken utilising a novel direct shear machine. A wide variety of sedimentary lithologies have been tested under constant normal displacement control and a mechanistic model for the evolution of frictional resistance developed. X-ray diffraction quantitative mineral identification and laser diffraction particle sizing technologies have been employed to characterise the induced debris distributions. A relationship is presented between the frictional strength of the sliding surfaces and the specific surface area of the induced cataclastic debris.
An estimation of bulk moduli of sandstones as a function of confining pressure using their petrographic and petrophysic description
Authors: Vincké O.
Published: December 2007

In a previous paper, we developed a model to estimate the terminal bulk modulus of sandstones using their petrographic and petrophysic description. The above mentioned model is summarized. A method which is introduced in the previous formulation is then developed to estimate the evolution of the bulk modulus as a function of confining pressure. The role played by the cement and the cracks is emphasized. We test the model using a basic data set in which the bulk moduli have been measured for 17 different sandstones for confining pressures up to 100 MPa.
Numerical Simulation of Three-Dimensional Natural Convection in Porous Media
Authors: Holst P.H. , Aziz K.
Published: December 2007

The equations of motion and the energy equation are developed for the prediction of temperature and velocity fields in the problem of natural convection in porous media. The equations are made suitable for numerical computation by introducing a vector potential which is the counterpart of stream function in two dimensions. This vector potential has previously been used by one of the authors to solve previously been used by one of the authors to solve the Navier-Stokes equation in three dimensions. The partial differential equations are solved by finite difference methods employing Alternating Direction Implicit Procedure [ADIP] and Successive Over Relaxation [SOR] methods. The model may be used when the heated side is vertical, horizontal or inclined. The detailed structure of three-dimensional cells predicted by this model is compared with previous two-dimensional studies conducted by the authors.

Analytical solutions are possible and available for the linearized partial differential equations for this problem. Such solutions only predict the onset of convection and fail to reveal what happens after convection sets in.

This is the first attempt in solving these equations for the case where nonlinear terms are not neglected and the predictions are carried out as a function of time and all three space directions.

The results are presented in the form of contour maps and show the interesting structure of convection cells in porous media.

Introduction

Natural convection is a phenomena conceivable in a petroleum reservoir subjected to fire or steam flooding. It is the result of adverse temperature gradients generating buoyancy forces that in turn cause fluid motion. A mathematical analog of the physical phenomena may be obtained by writing mass, force and energy balances on a differential volume of porous media. If Darcy's law is employed to porous media. If Darcy's law is employed to relate fluid flow to potential gradients and the Boussinesq approximations [fluid properties independent of temperature except where they contribute to buoyancy] are assumed to be applicable, the three balances reduce to two nonlinear partial differential equations. The two-dimensional form of these equations has been solved by a number of investigators. The reader is referred to Karra's thesis for a comprehensive literature review on the subject. In order to apply the mathematical model with some degree of confidence, an experimental verification is desirable if not necessary. As any experimental verification would presumably involve a three-dimensional apparatus, a study as to the effect of the third dimension on the solution was clearly indicated.
Comparison of borehole breakouts from laboratory and field tests
Authors: Martin C. D. , Martino J. B. , Dzik E. J.
Published: December 2007

Laboratory testing of granite blocks containing a circular borehole was carried out with uniaxial and biaxial loading conditions, and with borehole diameters ranging from 5 to 103 mm. Borehole breakouts were also investigated in situ using borehole diameters ranging from 75 to 3500 mm. Results show that the same strength-scaling law cannot be applied to both laboratory and in situ breakouts.
Basin Scale Rock Mechanics: Field Observations of Sand Production
Authors: Moricca G. , Ripa G. , Sanfilippo F. , Santarelli F. J.
Published: December 2007

Sand production is very common in the gas wells of the Adriatic Sea. Accurate field surveys have been conducted before and after sand production has occurred in wells where no sand control methods had been initially introduced. Unlike the numerous other papers dealing with sand production, this one describes the sand production observed in low permeability gas-bearing formations which include a significant amount of clays. The main parameters inducing sand production are identified and an empirical correlation is established which enables its prediction. Moreover, the influence of parameters such as depth, drawdown, depletion, gas rate, water gas ratio etc. on the occurrence of sand production is determined. The paper also reports the results of a sand flow test performed in a gas field situated in the surveyed area. Finally, these results are discussed in terms of geological history of the Northern Adriatic Basin.
Interaction and Link-up of Hydraulic Starter Fractures Close to a Perforated Wellbore
Authors: Weijers L. , de Pater C. J.
Published: December 2007

A hydraulic fracture treatment in a cased-perforated well may result in the initiation of inclined starter fractures from each perforation. We performed scaled model tests and observed that link-up of starter fractures was affected by the confining stress difference and the pressure in the fracture during a treatment. A large stress difference in the plane perpendicular to the perforations prevents starter fractures from linkage. Also, fracture linkage is affected by the cementation of the well. Fluid flow in the annulus between borehole and casing may results in better linkage, but the fracture may grow through the annulus and avoid the perforations.
Deformation Characteristics of Weakly Cemented Sandstone
Authors: Nikraz H. R. , Press M. , Evans A. W.
Published: December 2007

This paper reports the finding of a investigation carried out to evaluate the deformation characteristics of saturated sandstone aquifers in the Collie Coal Basin under conditions anticipated during dewatering operations.

A drained triaxial compression test technique for various combinations of confining pressure and back pressure was designed to examine the applicability of the effective stress theory suggested to Terzaghi (1), with particular reference to the Collie sandstone. Further, the results obtained were utilised to characterise the strength and deformability properties of the Collie sandstone.
Real-Time Microseismic Monitoring: Automatic Wave Processing and Multilayered Velocity Model for Accurate Event Location
Authors: Senfaute G. , Bigarré P. , Josien J. P. , Mathieu E.
Published: December 2007

At the Provence colliery, France, the remote microseismic monitoring used for the prevention of dynamic phenomena is an integral part of a strategy for exploring zones where there are risks of violent instability or rockbursts. Precise location, in real time, of the hypocentres associated with daily microseismic activity is one of the main objectives in the interpretation of data to optimise countermeasures. A study has been carried out with the purpose of calibrating an inclined wave propagation multilayered model. This article describes the operational microseismic monitoring network, the method used to calibrate the velocity model, the results obtained and the undeniable contribution which it makes to the quality of data interpretation.
Parametric or Nonparametric Analysis of Induced Seismicity Sequences
Authors: Lasocki Stanislaw
Published: December 2007

Methods of the seismic risk analysis in either natural or induced seismicity can be divided into the parametric methods and the nonparametric ones. Within the presented work correlations between ten functions representing nonparametric traits of the local sequence of induced seismicity, a risk function issued from the parametric model and the number of strong events in the sequence were studied. The analysis showed that the parametric approach to time-varying processes like the triggered seismicity process may give more reliable results than the nonparametric inference.
Storing Liquid Natural Gas in a Depleted Reservoir: Preliminary Results of a Feasibility Study
Authors: Brignoli M. , Santarelli F. J. , Zausa F.
Published: December 2007

Some rock mechanics laboratory tests at low temperature on both poorly consolidated sand and drilling cement samples have been performed. These may be useful when examining the feasibilty of storing LNG in depleted reservoirs as an alternative to more traditional methods; in the paper is presented a list of some of the questions which need to be answered in order ensure the feasibility of such a project and particular attention is given to the rock mechanics aspects of the problem. Variations of in-situ stress state due to thermal effects and behaviour of both rock and cement at low temperature are examined and some conclusion derived from simple models are given.
Sealing of Boreholes using Natural, Compatible Materials: Granular Salt
Authors: Finley Ray E. , Zeuch David H. , Stormont John C. , Daemen Jaak J. K.
Published: December 2007

Granular salt can be used to construct high performance permanent seals in boreholes which penetrate rock salt formations. These seals are described as seal systems comprised of the host rock, the seal material, and the seal rock interface. The performance of these seal systems is defined by the complex interactions between these seal system components through time. The interactions are largely driven by the creep of the host formation applying boundary stress on the seal forcing consolidation of the granular salt. The permeability of well constructed granular salt seal systems is expected to approach the host rock permeability (<10-21 m2 (10−9 darcy)) with time. The immediate permeability of these seals is dependent on the emplaced density. Laboratory test results suggest that careful emplacement techniques could result in immediate seal system permeability on the order of 10−16 m2 to 10−18 (10−4 darcy to 10−6 darcy). The visco-plastic behavior of the host rock coupled with the granular salts ability to "heal" or consolidate make granular salt an ideal sealing material for boreholes whose permanent sealing is required.
First Underground Refrigerated LPG Caverns in Brazil
Authors: Franciss F. O.
Published: December 2007

It is reported about the geotechnological investigations and the subsequent analysis as well as about the pre-design considerations of a planned underground refrigerated cavern system for gas in Brazil.
Mechanisms of Chalk Compaction
Authors: Powell Benjamin N. , Lovell Gary L.
Published: December 2007

A scanning electron microscope study of textures in several companion pairs of uncompacted and experimentally compacted Ekofisk chalk samples has documented two principal mechanisms of chalk matrix compaction. The dominant mechanism — which we have quantified through processing and analysis of digitized backscattered electron images — is simple grain displacement, which results in larger pore spaces being partially filled in by single calcite rhombohedra and other small fragments of bioclasts as the matrix porosity becomes more homogeneous with compaction. A second mechanism — which we have quantified by counting intact coccoliths in 100 secondary electron images per sample — involves the mechanical breakup (cataclasis) of bioclasts. The second mechanism contributes to the first. However, it clearly played a more significant role in the natural process of compaction over geologic time and is likely to be of only secondary importance relative to simple grain displacement during production-related compaction of the reservoir.
Changes in Mechanical Properties of Chalk Caused by Deformation and by Pore Pressure
Authors: Risnes R. , Gjesdal S. A. , Landaas T. L. , Madland I.
Published: December 2007

A laboratory study on weak high porosity outcrop chalk has been performed in order to see how mechanical strength is affected when the material is strained beyond the elastic limit. Both tensile and compressive strength and Young's modulus are considerably reduced, although there is some strain hardening in compressive strength with increasing degree of deformation.

A second part of the study addresses the possibility of causing damage when the pore pressure is increased like in stimulation operations. Samples that were pressurized, when locked in an oedometer cell, became weaker than samples with no pressure cycle.
Behaviour of Chalks
Authors: Siwak J. M. , Pecqueur G. , Mikolajczak A.
Published: December 2007

In order to study the behaviour of chalk, four chalks were tested under different loading conditions. We present, in this paper, the behaviour of these chalks under hydrostatic, oedometric, deviatoric, proportional and torsional tests. It appears that the behaviour of chalk can be predicted from Lade's model with a differenciation between after and before the pore-collapse. We observed that Lade's model agrees with chalk's case. The simulation of the torsional tests were made by fmite element analisys. From Chang's model and the one of Lade's model, the results give some good agreement between simulations and experimental tests.
Geophysical Monitoring during a Hydraulic Fracture in a Fractured Reservoir: Tiltmeter and Passive Seismic Results
Authors: Schemeta J. E. , Minner W. B. , Hickman R. G. , Johnston P. A. , Wright C. A. , Watchi N.
Published: December 2007

UNOCAL and Japan National Oil Corporation jointly carried out a hydraulic fracture operation in the Monterey Formation in the Newlove 110 well, located in the Santa Maria basin in central coastal California, USA. The treatment well was monitored by an array of tiltmeters to measure the surface deformation, and with a 3-component oriented geophone to monitor microseismic events during the stimulation. There is good agreement between the results of the two monitoring programs, each showed the procedure produced a vertical fracture with an azimuth of about N 60° E. This orientation also agrees well with the regional data from tectonic stress and fracture orientations.
Heterogeneous Stress Orientations in the North Sea Basin
Authors: Cowgill S. Mark , Meredith Philip G. , Murrell Stanley A. F. , Brereton N. Robin
Published: December 2007

The orientations of stress induced wellbore breakouts in the North Sea Basin are diiectionally heterogeneous. Few obvious trends are apparent. Consistent orientations can only be observed in relatively small geographic domains. In constrast, more consistent orientations are observed when the data are divided into separate chronostratigraphic intervals. We propose that the stress distribution within each domain is controlled by the superimposition of the local geological structure and the effects of palaeostress fields onto the present day tectonic stress field.
Some Field Observations Of Heterogeneity Of Reservoir Rocks And Its Effects On Oil Displacement Efficiency
Authors: Elkins Lincoln F. , Skov Arlie M.
Published: December 2007

Ten to possibly thousand fold ratios of horizontal permeability to vertical permeability are required in two "clean" sand reservoirs to match actual water-free product ion of oil and. gas of wells having bottom water. Layer models with average permeabilities of cores at similar stratigraphic position in the reservoir rather than values selected from the permeability frequency distribution and with highly restricted cross flow yield the best match between actual and calculated dilution of wet gas by injected gas in two cycling projects. These same reservoir modeling concepts yield reasonable agreement with actual performance of the Seeligson enriched gas drive test without assumption of serious viscous fingering with gravity segregation.

Introduction

The effects of heterogeneity off reservoir rocks on fluid displacement efficiency remain as a very important unsolved problem in this period of rapidly growing application of fluid injection for increased recovery of oil. Hypotheses of reservoirs ranging from non-connecting layers characterized by permeability frequency distribution, irrespective of spatial origin of cores, to reservoirs so heterogeneous they are nearly homogeneous have been offered as bases for evaluation of actual oil recovery projects. Since we are forever barred from knowing the actual variation arid continuity of rock properties, it is imperative that we test our simplified models against performance of actual reservoirs to select those assumptions most appropriate as guides to judgment. This paper presents two types of field observations having a bearing on these models:Determination that 10 to possibly1000 fold ratio of horizontal permeability to vertical permeability is required to match water coning performance of a number of wells in "clean" sand reservoirs in contrast with very low ratios usually observed in small core plugs. Possibly cross flow between layers in laboratory fluid flow models or calculated mathematically for multilayer systems with equal horizontal and vertical permeabilities may not be representative of actual reservoirs in which gross anisotropy appears to be much greater than that of small cores.Agreement between actual dilution of gas streams by injected gas in two cycling projects and that calculated with assumption of parallel flow in separate layers is reasonable if permeabilities assigned to individual layers are average permeabilities of cores from different wells at the same relative vertical position in the reservoir section rather than values from the permeability frequency distribution.

Most performance features of the current Seeligson enriched gas drive project are adequately matched by this parallel layer type analysis.
Evaluation Of Cement Systems For Permafrost
Authors: Morris E.F.
Published: December 2007

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Cementing of casing in the permafrost on the Alaskan North Slope presents new problems to many operators. Primarily, the cement system must be kept from freezing until after the setting reaction is complete. Different types of systems have been suggested and used to solve this problem. High alumina cement systems, however, appear to be the most satisfactory at this time.

This paper presents data of several systems proposed for permafrost cementing and attempts to point out the merits and disadvantages of each.

Introduction

Cementing of pipe set through the permafrost in Alaskan North Slope wells introduces permafrost in Alaskan North Slope wells introduces new problems. The permafrost section is reported to vary from unconsolidated sands and gravels with ice lenses to some areas of icefree, consolidated rock. A broad definition of permafrost is that formation from surface to a depth where the temperature is at 32 degrees F or below. This depth may vary from 500 feet to 2000 feet. The permafrost temperature may range from 15 degrees F up to 32 degrees F. Conventional cement systems, commonly used in oil well cementing are not satisfactory under these conditions. Conventional cement slurries will freeze, preventing the development of set cement when placed in the low-temperature environment.

Operators on the North Slope requested a cement system that could be mixed, pumped and conventionally placed behind the pipe set through the permafrost. The cement should set to adequate compressive and bond strengths, sufficient to support the pipe and prevent the circulation of drilling fluids up the annulus as drilling is continued. It was further requested that the cement system and placement technique be kept as simple as possible due to the adverse working conditions present on the North Slope.

Conventional laboratory methods commonly used for designing and testing cement systems were not adequate to develop reliable cement systems for permafrost cementing. A test method more closely resembling permafrost conditions and one that could be readily reproduced was needed. A model was developed which met these requirements.
Unenclosed Gas Plants for Colder Climates
Authors: Kyllo M.A. , Phillips M.D.
Published: December 2007

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Construction of unenclosed gas processing plants is suitable for cold processing plants is suitable for cold weather operation provided appropriate winterizing procedures are followed. The result should be a safer operating plant with less investment. plant with less investment

Introduction

Hudson's Bay Oil and Gas Company Limited is a producing company employing 875 people. It was formed through an agreement between what is now Continental oil Company in the United States and the Hudson's Bay Company Limited. The Hudson's Bay Company was incorporated in 1670 under a charter given by King Charles II. It is the oldest company in existence in North America.

Hudson's Bay Oil and Gas operates seven sour gas plants and one sweet gas plant in Alberta. These vary in size plant in Alberta. These vary in size up to our largest, the Kaybob South Gas Processing Plant which is designed to Processing Plant which is designed to produce 2080 long tons of sulphur, produce 2080 long tons of sulphur, 25,000 bbls. of condensate and 6,800 bbls. of LPG per day. This plant is located on 54.5 degrees North Latitude and is subject to severe winter conditions. It is this plant and our Edson Gas Plant, about 60 plant and our Edson Gas Plant, about 60 miles south of the Kaybob South Plant, which will be discussed in this paper.

Discussion

Winter temperatures in North Central Alberta will drop to 60 degrees F below zero on occasion. Minimums of 40 degrees F below are expected. Unless proper design precautions are taken, temperatures at this precautions are taken, temperatures at this level can make a plant inoperable.

One of the first decisions to be made in plant design is the extent of housing for the plant. The plants being considered in this paper are basically unhoused. only process pumps containing water, compressors, firing ends of boilers and other small equipment containing water are housed. One major reason for this decision is safety. The gas we handle contains up to 17% hydrogen sulphide, which is extremely poisonous. poisonous.
Quantification of Production Prediction Uncertainty and Its Impact on the Management of Oil and Gas Price Risk
Authors: Edwards R. A. , Hewett T. A.
Published: December 2007

Oil and gas commodity price risk is a manageable component of economic risk, and can be reduced or controlled by the use of financial derivative securities such as futures, forwards and options. The ability to manage oil and gas commodity price risk is dependent, in part, upon the ability to quantify uncertainty in production forecasts and reserve evaluations. Based on the explosive growth of commodity price risk management strategies and the ability of sophisticated reservoir characterization and modeling algorithms to quantify uncertainty, the prevalence of probabilistic production and reserve evaluations will continue to increase, as well as the importance of the petroleum engineer in the process of financial risk management. In this paper, a historical review of the volume of transactions involving oil and gas derivative securities shows the broad based growth of risk management strategies among oil and gas producers. Additionally, this paper presents a methodology and describes a computer model which incorporates financial derivative securities into a stochastic economic model of oil and gas producing properties.
Pressure Transient Analysis of Two Horizontal Wells in the Ann Field
Authors: Ghazarian V. , McCoy T. F. , Beebe G. D.
Published: December 2007

The Ann gas field offshore United Kingdom was successfully developed in 1993 using two subsea completed horizontal wells in a layered Rotliegend sandstone. Requirements for well test design, implementation and the subsequent interpretation of transient pressure data from a layered reservoir test are discussed. Use of field appraisal data for validation of initial test interpretations, which have formed the basis for prediction of long term performance, is emphasized. In addition, field data for the first six months of production are presented and recommendations to optimize testing and improve performance of horizontal wells in layered reservoirs are made.
Downhole Mass Flow Rate Measurements Enhance the Analysis of Well Test Data: A Field Example
Authors: Paux F. , O’Callaghan A. W. , Deruyck B. G. , de la Combe J. L. Boutaud
Published: December 2007

Measurements associated with drillstem tests (DSTs) comprise surface flowrates and downhole pressure and temperature. Sandface rate and fluid density are important data but are generally not measured for lack of the appropriate instrumentation. These measurements are occasionally available when a production logging survey is conducted during DST operations. This is, however, not often the case because of the risk of spinner clogging when the well is cleaning up or when significant sand production occurs.

This paper presents a DST data set composed of continuous downhole density and mass flowrate measurements in addition to the "standard" pressure and temperature. It was acquired with a prototype fullbore multiphase flowmeter located below the tester valve.

Sandface fluid density provides a means to monitor the clean up period. Sandface rate measurements are used to convolve the reservoir pressure response and to estimate reservoir permeability and skin from flowing transients. Of particular interest in this field example, the additional measurements provide evidence of the formation of a gas cap below the tester valve during the main shut in, allowing interpretation of the apparently incoherent build up response.
Geostatistical Integration of Geological, Petrophysical, and Outcrop Data for Evaluation of Gravity Drainage lnfill Drilling at Prudhoe Bay
Authors: Hand J. L , Moritz A. L. , Yang Chung-Tien , Chopra A. K.
Published: December 2007

An integrated geostatistical methodology for a site-specific reservoir description was used in reservoir simulations to establish additional recovery benefits for gravity drainage infill wells for the Romeo interval for Drill Sites 2 and 5 at Prudhoe Bay. The available geological information varied over multiple scales and included: a detailed chrono-stratigraphic framework relating rocks of similar depositional times, a detailed depositional model with facies associations described at each well from log and core data, and analog outcrop training images obtained using photomosaics.

The reservoir description methodology transformed the facies associations at each well into indicator variables and used these variables to analyze vertical and lateral spatial correlation. Conditional truncated gaussian simulation was then used to generate 3D facies association maps within the model area constrained by the chrono-stratigraphic framework. Input from geologists was critical in the evaluation of the geological realism of the computed facies association maps. Porosity and permeability vertical and lateral spatial correlations were then determined for each facies association. Vertical correlation was determined from variogram analysis while lateral correlation was determined from the outcrop training images. Conditional sequential gaussian simulation was then used to distribute 3D porosity and permeability, separately within each facies association, throughout the model area. A pressure solver was used to scale up the 3D fine scale permeability distributions to grid blocks appropriate for direct input into a flow simulation model.

The conditional simulation methods allowed the integration of geological information on a number of different scales, thereby capturing the 3D complexity of the Romeo interval. The 3D facies association description generated using this methodology was judged by geologists to depict a very reasonable geological picture of the DS-2,5 Romeo interval. The pressure solver used to scale up the fine scale permeability distributions maintained the major permeability features apparent in the fine scale distribution which were important to reservoir performance.
Implementing a Total Productive Management (TPM) System in Production Operations
Authors: Carpentier P. L. , Devereux J. E. , Harper D. R. , Miller R. W.
Published: December 2007

In 1993, Shell Western E&P Inc. implemented a pilot Total Productive Management system for Production Operations in the Wasson Field near Denver City, Texas. As a result, significant changes have been made in the work processes used by personnel in Operations, and there has been a dramatic reduction in operating expenses.

In less than two years, Shell employees have been able to achieve cost savings of more than $3 million per month at Shell-operated producing properties in the Wasson Field.

Because of the success of the Wasson Field pilot, TPM systems are now also being implemented at other locations and properties operated by Shell Western E&P Inc.

This paper describes the eight activities that characterize the Total Productive Management (TPM) system that is now in place in the Wasson Field. The benefits that have occurred and problem areas that affected implementation of TPM are also discussed. Three key pieces of the TPM system are addressed in the paper: Surface Maintenance and Repair; Rig Work; and Operations.