bluuebunny/crossref_metadata_2025 huggingface dataset:
A General Formulation for Compositional Reservoir Simulation
Authors: Rodriguez Fernando , Galindo-Nava Agustin , Guzman Javier
Published: December 2007

In this paper we present a general formulation to solve the non-linear difference equations that arise in compositional reservoir simulation. The general approach here presented is based on Newton's method and provides a systematic approach to generate several formulations to solve the compositional problem, each possesing a different degree of implicitness and stability characteristics. The Fully-Implicit method is at the higher end of the implicitness spectrum while the IMPECS method, implicit in pressure-explicit in composition and saturation, is at the lower end.

We show that all methods may be obtained as particular cases of the fully-implicit method. Regarding the matrix problem, all methods have a similar matrix structure; the composition of the Jacobian matrix is however unique in each case, being in some instances amenable to reductions for optimal solution of the matrix problem. Based on this, a different approach to derive IMPECS type methods is proposed; in this case, the whole set of 2nc + 6 equations, that apply in each gridblock, is reduced to a single pressure equation through matrix reduction operations; this provides a more stable numerical scheme, compared to other published IMPECS methods, in which the subset of thermodynamic equilibrium equations is arbitrarily decoupled from the set of gridblock equations to perform such reduction.

We discuss how the general formulation here presented can be used to formulate and construct an adaptive-implicit compositional simulator. We also present results on the numerical performance of FI, IMPSEC and IMPECS methods on some test problems.
Experimental and Mathematical Modeling of Helical Buckling of Tubulars in Directional Wellbores
Authors: Salies J. B. , Azar J. J. , Sorem J. R.
Published: December 2007

Experimental testing of helical buckling of tubulars, using three different test facilities, is presented and discussed. The tests provide information to better understand the buckling behavior of circumferentially restrained tubulars. The finite element method is used in the analysis of helical buckling, allowing inclusion of friction during the development of the helix. There was an excellent agreement between the finite element solution and the experimental results.
Big Mineral Creek Barnes Unit - A Successful Water Injection Pressure Maintenance
Authors: Alderman J.H.
Published: December 2007

A successful water injection pressure maintenance operation has been in progress in the Big Mineral Creek (Barnes sand) field, Grayson County, Tex., since Aug., 1962. The Barnes sand is typical of many fields in North Texas in that it is composed of several separate sand bodies operated as a single reservoir. one of the objectives, therefore, in planning the supplementary recovery operation was to insure maximum hydrocarbon recovery from each of the five sands which constitute the Barnes reservoir.

To insure this, a stage flood was initiated in which injection and production was confined to the lower sand member initially. When the flood front was sufficiently advanced, the next shallower zone was opened for production and injection. This procedure will be repeated until all five zones are effectively flooded out.

Introduction

The Big Mineral Creek (Barnes sand) field is typical of many fields in the North Texas area in that it is composed of a number of individual sand bodies which are in reality individual reservoirs and which have been grouped together and classified as a single field. This type of grouping did not offer any major production problems during the primary production portion of the reservoir's history. production portion of the reservoir's history. However, early in the life of the field it was realized that a pressure maintenance project would be desirable in the Barnes sand, and a plan of operation would be needed which would plan of operation would be needed which would maximize production from each individual sand member. Experience in other fields of this type had shown that, unless some type of selective injection was initiated, water breakthrough could occur in one of the minor sand intervals with better permeability. Corrective measures later in the life of the flood, if this sand was located in the center of the interval, could be costly.

GEOLOGY

The Big Mineral Creek area is located as shown in Fig. 1 on the west side of Marietta syncline and on the eastern flank of the Walnut Bend platform in Grayson County, Tex. This area is composed of a stratigraphic series of sandstone reservoirs which include the Barnes sand. The Barnes reservoir was established by field rules as a stratigraphic interval existing between the approximate depths of 4,900 and 5,200 ft. Contained within the Barnes interval are five correlative sand bodies that are lithologically characterized as fine to medium grained sandstones containing traces of chert. A type log of this interval is shown in Fig. 2. These zones comprise the basal portion of the upper Des Moines strata.
Analysis Method for Contact Forces Between Drillstring-Well-Riser
Authors: Bueno R. C. S. , Morooka C. K.
Published: December 2007

This paper proposes a methodology(1) to estimate the contact forces generated by the drillstring against the wellbore and the marine drilling riser system. A new procedure for overall analysis of the drill string behavior inside the riser and wellbore is described.

This is important in the safety analysis of the wellhead equipment and also in planning drilling operations. The results also suggest that the forces should be used in the dynamic analysis of marine riser system.
Coiled Tubing Drilling on Lake Maracaibo
Authors: Adamson S. J. , Rodriguez A. , Leising L. J.
Published: December 2007

Drilling through shallow gas zones can be a major hazard, especially in offshore operations. An innovative technique using tender-assisted coiled tubing (CT) drilling is presented, which allows the determination of hazardous shallow gas presence with minimum risk, prior to mobilization of a large drilling barge. One advantage of the use of CT drilling is in increased safety because there are no personnel on the platform while drilling as the barge is kept 1 50 ft. away from the platform. Should a shallow gas flow occur, the gas is diverted with only minimal equipment exposed to damage and no danger to personnel.

The technique of tender-assisted coiled tubing drilling has been used to drill five 3-7/8 in. slim hole wells in Lake Maracaibo, Venezuela. Equipment, techniques, and safety merit to perform the drilling operation are described. The successful multiwell campaign has provided

References and illustrations at end of paper a drastic improvement in safety while significantly reducing top-hole drilling costs. With the learning curve progress allowed by a multiwell program, it is demonstrated that drilling rates with CT can exceed those of conventional rotary drilling.

Applications

This technique is applicable to many shallow gas problems both on land and offshore.

Technical Contributions
Risk Analysis Theory Applied to Fishing Operations: A New Approach on the Decision-Making Problem
Authors: Cunha J. C. S.
Published: December 2007

In the past the decisions concerning whether to continue or interrupt a fishing operation were based primarily on the operator's previous experience(1). This procedure often led to wrong decisions and unnecessary loss of money and time.

This paper describes a decision-making method based on risk analysis theory and previous operation results from a field under study. The method leads to more accurate decisions on a daily basis allowing the operator to verify each day of the operation if the decision being carried out is the one with the highest probability to conduct to the best economical result. An example of the method application is provided at the end of the paper.
Effects of Porosity and Permeability on In-situ Combustion Fuel Consumption
Authors: Couch Earl J. , Rodriguez Harold V.
Published: December 2007

This paper presents a method for estimating field fuel consumptions by adjusting laboratory in-situ combustion fuel consumption data for the effects of formation porosity and permeability. permeability. Results from combustion experiments were used to establish the reaction kinetic and heat loss parameters in an in-situ combustion model. After attaining satisfactory agreement between calculated and experimental results, both for unconsolidated and consolidates media, the model was used to calculate the effects of changes in porosity and permeability on the fuel consumption. Calculations were made for a wide range of crude oil viscosities. The study showed that porosity and permeability have marked effects on fuel consumption, and that these effects depend on the crude oil viscosity.

Introduction

In-situ combustion has become an important process for oil recovery. Successful process for oil recovery. Successful engineering of one of these projects depends on the estimate of the fuel concentration, which determines air requirements for propagation of the combustion front. Air requirements can critically affect the technical and economic prospects for an installation. prospects for an installation. Because of the importance of fuel concentration to the process, many studies aimed at correlating fuel with the various chemical physical and operating parameters of the physical and operating parameters of the system have been made. These attempts have not produced generally applicable correlations. Consequently, current practice in estimating fuel for a particular field prospect involves laboratory experimentation to characterize the system. Commonly a combustion tube run provide an estimate of the fuel concentration under laboratory conditions. This value may be corrected for various field operating condition which differ from those in the laboratory, such as pressure or gas flux.

Two parameters which should affect the fuel, but whose effects have been treated only briefly in the literature, are permeability and porosity. Alexander, Martin and Dew found that porosity. Alexander, Martin and Dew found that with a 21.8 degrees API crude oil., crushed Curtis core gave essentially the same fuel availability as consolidated Crutis core, and that an Ottawa sand pack gave essentially the same fuel availability as a consolidated Berea core. Moss, White and McNiel presented two combustion tube runs which gave fuel values closely comparable to field test results. Theoretical papers make no direct mention of the effects papers make no direct mention of the effects of permeability and porosity on fuel concentration.
Fractal Distributions of Reservoir Properties and Their Use in Reservoir Simulation
Authors: Berta Dominique , Hardy H. H. , Beier R. A.
Published: December 2007

Geostatistics has become a popular way to distribute reservoir properties between wells. One of the geostatistical methods being used is fractal geostatistics. Most porosity well logs have been found to have a fractal character. An analysis of vertical and horizontal logs, core photos, and outcrop photos has led to a rather simple model to describe porosity and permeability distributions. This representation has been tested in reservoir simulation of a mature waterflood and found to match production history with very little history matching. Fractal distributions were found to require much less history matching than classical layer cake models. Conoco is now actively applying this new technology to a number of its reservoirs.
New Polymer/Surfactant Systems for Stabilizing Troublesome Gumbo Shale
Authors: Alonso-Debolt M. A. , Jarrett M. A.
Published: December 2007

With increasing environmental regulations on the use of oil-based (or synthetic-based) invert emulsion drilling fluids, options for designing more inhibitive water-based drilling fluids with greater versatility are being explored. The challenge set for water-based drilling fluid technology is to meet the same performance expectations of oil-based drilling fluids, particularly for improving shale stabilization.

This paper discusses the development and application of water-based polymeric mud systems that incorporate new chemical classes of surfactants. These new zwitterionic surfactants demonstrate unique synergistic benefits with polymers for improving shale stabilization.
Unusual Lacustrine Reservoirs and Seals of the Murteree Horst Area, Eromanga Basin, Australia
Authors: Williams N. V. , Theologou P. N. , Boult P. J. , Zwigulis Maris , Schlichting R. P. , Price R. A.
Published: December 2007

The Murta Member within the Murteree Horst area consists of a very thin, high permeability sand (HPS) within predominantly low permeability, thinly laminated, carbonaceous siltstones collectively referred to as the low permeability region (LPR). This HPS has a thickness of about 1 foot and a large lateral extent of about 10,000 acres.

The HPS and LPR together have been postulated to contain an OOIP of up to 74 million bbls in the Murteree Horst area, however the LPR also acts as a capillary seal to the underlying McKinlay reservoir. The production behaviour of the Murta reservoirs has remained enigmatic since their discovery.

Under production the HPS initially shows a rapid pressure drop indicative of oil expansion drive in a closed or almost closed system. However eventually a water drive develops which behaves as though there is a very large or possibly infinite aquifer.

Although most of the postulated 74 MMB of oil was thought to be in the LPR it appeared none of the LPR oil was being produced. It was not clear whether this oil could be mobilised. This investigation suggests that oil contained within the LPR is largely immobile and may even be representative of oil migration conduits only.
Three-Dimensional Fully Coupled Flow: Consolidation Modelling Using Finite Element Method
Authors: Sukirman Y. B. , Lewis R. W.
Published: December 2007

A versatile numerical solution will be presented for simulating a compacting oil reservoir and its subsidence at the surface. The mathematical formulation was derived based on Biot's self consistent theory which describes a fully coupled governing equation system for a saturated oil reservoir. It consists of the equilibrium and continuity equations for oil, gas and water-phases flowing in a porous media. The non-linearities due to mobility and accumulation terms were implicitly determined at each iteration level. These non-linear variables account for the effects of reservoir heterogeneity, relative permeability contrasts, rock and fluid compressibility factors, capillary pressure and other rock properties.

An elastoplastic reservoir rock model, based on a Mohr Coulomb yield surface, was used for simulating the deformation behaviour of both reservoir and overburden/underburden formations. The Galerkin based finite element method will be applied to obtain simultaneous solutions to the governing equation system where the displacement and the fluid pressures are the primary unknowns. Finally, several simulations are to be conducted for predicting the overall performance of a compacting oil reservoir and its subsidence problem at the surface.
A Predictive Model Enhances Optimized Production and the Completion of the Production System
Authors: Farshad F. F. , LeBlanc J. L. , Root P. J.
Published: December 2007

A gas or an oil production system is usually composed of several distinct elements, one of which can be characterized as "flow through the well completion section with the pressure drop from the sandface flowing pressure to the bottomhole flowing pressure". This segment consists of fluid flow through different types of completions such as openhole completion, perforated and gravel-packed or conventionally perforated tunnels that are not gravel-packed.

The prediction performance, the production optimization and the productivity of a gas or an oil well is strongly affected by a composite or total skin around the completion zone.

In perforated completions, the completion interval consists of the perforation tunnels extending from the inside casing wall through the casing and cement sheath to a point within the sandface near the wellbore. A principal factor in the design of a well completion is the consolidation or competency of a producing formation. If the completion is a gravel pack, as in the case of poorly or unconsolidated sands, perforation tunnels should be gravel-filled to a point outside the cement sheath or perhaps up to the cement sheath-sandface interface. In non-gravel packed perforated completions, as in the case of highly consolidated or competent formations, the perforation tunnels are probably unobstructed and extend to a point within the sandface. A thin zone of compacted formation surrounds each perforation tunnel creating a "skin effect" due to perforation damage.

The objective of this paper is to show that the economic development and production of gas or oil wells dictates consideration of two separate but related subjects: Total optimization of the production systemLimitation of pressure drop through gravel packed or conventionally perforated completions that are not gravel-packed.

This paper will show that the maximum production rates possible from gas wells are usually restricted by limiting design parameters. Proper evaluation of these critical areas can extend the life of the a well six to seven-fold. Although this paper is addressed specifically to gas wells, the techniques shown can be applied to oil wells as well as any other gas production system.
Simulation of Fluid Flow in Coal Using a Discrete Fracture Network Model
Authors: Choi S. K. , Wold M. B.
Published: December 2007

A discrete element model for coal which combines simple mechanisms of matrix deformation and discrete fracture network fluid flow has been applied to investigate stress-induced permeability alteration and stress change around a wellbore during a step rate injection test. The model demonstrated that the dominant physical processes at a relevant length scale can be simulated.
Java Sea Gas Reservoir Development Design
Authors: Pathak Prabodh , Kasim A. T. , Yusmiati Ida , Ismoyo Hadi , Bukhari Tahir
Published: December 2007

Gas deliveries were started from the Offshore North-West Java Sea (ONWJ) concession area to Indonesian electricity generating facilities in 1993. This paper addresses the development and reservoir engineering of shallow gas fields underlain by bottom aquifers. A multi-disciplinary team of geologists, geophysicists, reservoir engineers, production engineers and facilities engineers conducted an extensive study to optimize the development plan. This paper shows that the critical coning rates for high permeability reservoirs with a large gas column thickness are very high and the reservoirs can be drained effectively by vertical wells. Low permeability reservoirs with a small gas column thickness require horizontal wells to increase production rates and ensure high recovery efficiencies. Water breakthrough is early in the field life and there is substantial gas production after water breakthrough. This paper uses the concepts generated from single-well models to develop the reservoir depletion plans for four gas fields in the ONWJ concession.
Numerical Geology: Predicting Depositional and Diagenetic Facies From Wireline Logs Using Core Data
Authors: Altunbay Mehmet , Barr D. C. , Kennaird A. F. , Manning D. K.
Published: December 2007

To exploit a reservoir, the geological model must accurately define the depositional environment and the effects of diagenesis on the pore network. Current methods for establishing the geological model of a field usually require subjective, qualitative interpretation of geological and petrophysical data. A method -Numerical Geology - has been developed that greatly reduces the subjectivity in geological modelling efforts. This method also allows geological attributes to be quantified and predicted.

Numerical Geology involves the integration of petrophysical, petrological and geological data with wireline log responses. The geology of "Hydraulic or Flow Units" intervals with similar hydraulic characteristics is described using conventional sedimentology, petrography and core analysis data. These data are translated into a matrix of geological indices classified according to hydraulic unit profile of the section. Hydraulic units are then predicted for uncored sections based on their unique log signatures that are obtained from cored sections. By combining predicted hydraulic units profile with the matrix of geological indices for eachflow unit, profiles of geological attributes are derived. The prediction reliability of hydraulic units is calculated based on the uniqueness of log signatures for each flow unit. Therefore, the confidence level for geological predictions can be assigned to estimated profiles of geological attributes. This eliminates much of the subjectivity from future geological interpretations and predictions.
A Model for Multiphase (Gas-Water-Oil) Stratified Flow in Horizontal Pipelines
Authors: Neogi Sudarsan , Lee Aihsin , Jepson W. P.
Published: December 2007

A mechanistic model for gas-liquid-liquid systems has been developed. Given the superficial velocities of the constituent phases and their physical properties, and the pipe diameter the corresponding oil and water film thicknesses in three phase stratified flow canbe predicted. Experimental data has been obtained for gas velocities upto 7 m/s. The model predictions agree well with the experimental data.
Pressure Drop in Perforated Pipes: Experiments and Analysis
Authors: Su Ze , Gudmundsson J. S.
Published: December 2007

The total pressure drop in horizontal wells is considered to consist of reversible (acceleration) and irreversible (wall friction, perforation roughness, mixing effects) pressure drop. The fundamental equations for pressure drop are presented along with relationships used for pipe junction flow. Experiments on a perforated pipe with 144 perforations, geometrically similar with wellbore casing (12 SPF, 60° phasing), are presented and analyzed. The results are applied to a typical horizontal oil well in the North Sea. It was found that the total pressure drop consists typically of 80 percent wall friction, IS percent mixing effects (including perforation roughness) and 5 percent pressure drop due to acceleration.
The Application of Pressure Drop Through a Horizontal Well Correlation to Oil Well Production Performance.
Authors: Arshad Azmi M. , Manan Muhammad A. , Ismail Abdul R.
Published: December 2007

From the petroleum engineering standpoint, pressure drop through a horizontal wellbore is very small and is negligible in predicting the production performance. However, not much research has been done to study this phenomenon and more importantly to prove the above assumption.

This paper discuss the application of published pressure drop through a horizontal well correlation in the prediction of horizontal oil-well production performance. The correlation relates two-phase pressure drop along the hole to the fluid inflow from the reservoir. This correlation together with friction and hydrostatic effects were used to determine the total pressure drop from the wellhead to the well tip. The calculations by iteratively solving pressure drop along pipe equations with reservoir flow equations was done with the aid of computer program.

The study proves that pressure drop is very important in predicting the inflow rate distribution along wellbores especially when using small perforated rough pipes and dealing with long horizontal wellbores.
The Separation of Solids and Liquids With Hydrocyclone-Based Technology for Water Treatment and Crude Processing
Authors: Ditria J. C. , Hoyack M. E.
Published: December 2007

Hydrocyclones have been used in a variety of process industries for over 100 years. They are a simple and effective device, but still widely misunderstood in the oil and gas industry. Hydrocyclones ideally lend themselves to numerous separation applications, overcoming conventional technical and economic operating constraints.

The objective of this paper is to "demystify" the basic operation of hydrocyclones and identify separation situations where hydrocyclones can offer significant advantages. These include a significant reduction in equipment size and weight which equates to significant costs savings on new projects, especially offshore. Hydrocyclones also provide the opportunity for additional processing capacity on existing facilities where little or no expansion space is available. Furthermore, hydrocyclones offer enhanced separation efficiencies when compared to conventional equipment.

When coupled with complementary conventional process equipment the resultant hydrocyclone based water treatment system is smaller than an equivalent conventional system. This results in an increase in process efficiency per volume utilized.
Computer Programs for Application to Large Volumes of Digitized Well Logs
Authors: Althaus V.E. , Lean J.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.

Large volumes of digitized well logs can only be used efficiently if computer programs are available to assist in digitizing quality control, data editing, storage and retrieval, analysis and display. To date, the major industry effort has been directed toward improved analysis programs. This paper summarizes several of the more important applications of computers to well logs.

Introduction

The number of uses of digitized well logs is increasing in the mineral industries. Standard and exotic analysis programs are yielding more information from logs than was previously economical by hand methods. These previously economical by hand methods. These programs are applicable to one or several programs are applicable to one or several wells in reservoirs, fields or basins. The efficient use of these analysis programs for multiple wells demands other computer programs to quality-check and edit the digitized data, to store and retrieve it and to display the analysis in a form appropriate to the study in progress. Underlying all uses of digitized well logs, however, it the assumption that the digitized data faithfully represent the measurements made by the logging sonde.

Data Quality

Many applications of digitized logs depend as critically on the digitizing process as they do on the logging operation. Porosity calculations are sensitive to errors in the amplitudes of digitized logs, and certain log correlation and filtering methods may require curves digitized in equal increments of arc length rather than in equal increments of well bore depth.

The computer can assist in the editing and quality control of the log data. The most widely accepted method of checking data is a plotback and overlay technique. While this plotback and overlay technique. While this method is the most accurate when used by technical persons, it has two limitations: it assumes the source document is the most accurate basic information, and it does not take advantage of the computer's speed.
Estimation of Water Saturation from Clay Microporosity Data
Authors: Hurst Andrew , Nadeau Paul
Published: December 2007

Clay microporosity data are derived from image analysis of petrographic sections. These data allow estimation of clay-bound water and establish a quantitative relationship between clay texture and effective volume. Small quantities of highlymicroporous clay may cause drastic degradation of permeability with little effect on total porosity.
Teamwork: The Methodology for Successfully Drilling the Judy/Joanne Development
Authors: Kelly J. H.
Published: December 2007

A "non-integrated" approach was used to manage development drilling of the Judy/Joanne field. Phillips Petroleum Company United Kingdom Limited ( the Operator ) elected to retain the role of project and operations coordinator. Others have felt it necessary to integrate the provision of drilling services to achieve operational effectiveness. The Operator approached the management of the operation on a more traditional tack but with the same goal. The management emphasis was on team building and ensuring each party's contribution was optimized. The "non-integrated" approach to service provision enabled the Operator to maximize the value of inhouse experience, to select the preferred suppliers based on safety and operational performance, and to maintain the leading role required of the lease holder. An incentive contract with the drilling contractor rewarded and penalized performance. It provided a "win/win" arrangement. Contracts with the third party companies were awarded on the basis of "best for purpose". The "non-integrated" approach has proven cost effective and an operational success [1].
Low-Cost Integrated Teamwork and Seismic Monitoring Improved Reservoir Management of Norwegian Gas Reservoir With Active Water Drive
Authors: Grinde Per , Blanché J. P. , Schnapper D. B.
Published: December 2007

This paper shows how new techniques, using integrated seismic and reservoir modelling, have shown there is no need to drill two previously proposed additional producers on the Heimdal gas field. Older simulations had shown this to be necessary in order to recover locally trapped gas. The study emphasizes the necessity of close team work to obtain the detailed reservoir description needed for such a study.

A multidisciplinary team of geologists, geophysicists and reservoir specialists performed this study to reappraise the Heimdal Field. Using seismic attributes from 3D (mainly 2D amplitude versus offset AVO) a detailed structural and seismic stratigraphic interpretation provided the geometrical basis for the field model. A heterogenetic approach (identifying potential flow barriers) to detailed geology was then applied using regional experience and detailed field data including the production characteristics. The resulting reservoir model also incorporated offset fields on common regional aquifers, to properly monitor and predict the dynamic pressure behaviour and aquifer energy in this series of connecting, Paleocene, turbiditic sands.

Two repetitive seismic campaigns have been acquired since the pre-production 3D seismic survey. Mapping of the water encroachment was accomplished using advanced interpretation techniques of 2D AVO and inversion. The results have been integrated into the dynamic matching process in the reservoir simulation.
Targetting the Guinevere Horizontal Well: A Case Study Involving Geostatistics, Reservior Description, Reservoir Simulation, and Drilling Engineering
Authors: Fisher W. C. , Bond D. J. , Skeith G. L. , Bonnett Nigel , Gadgil A. G.
Published: December 2007

The 48/l 7b-G2 well was the second and final development well on Guinevere; a UK Southern North Sea Rotliegendes gas field.

Guinevere is an aeolian reservoir developed within a faulted anticline with a partial gas column. A horiwntal well as the primary prod ucer was deemed necessary to avoid water influx problems.

The surface location was constrained by the existing vertical well. Optimisation of the bottom hole location and reservoir target was achieved by integrating analysis from a variety of disciplines. The location of the horiwntal section was determi ned by considering the following factors: The thickness of the gas column was prognosed using geostatistical depth conversion methods based on 30 seismic. This was integrated with fault detection and seismic amplitude as an indicator of reservoir quality. Additionally the target horiwn was derived from a detailed geological model and the orientation of the internal reservoir heterogeneity determined the optimum well orientation. Potential interference of the existing vertical and horiwntal wells also influenced the location of the G2 well.

Drilling constraints placed limits on our ability to satisf y all of these requirements.

A well location was chosen which satisfied most of the above considerations. This involved a 160 degree left hand turn in the borehole trajectory. In early 1993 the well was drilled to the chosen location and a 3500 ft horizontal section was successfully completed. The well has proved to be the most prolific in the Lancelot complex.
Assessment of Choke Valve Erosion in a High-Pressure, High-Temperature Gas Condensate Well Using TLA
Authors: Birchenough P. M. , Cornally Darren , Dawson S. G. B. , McCarthy Patrick , Susden Steven
Published: December 2007

Many planned new developments in the North Sea will involve the exploitation of hostile high pressure, high temperature gas condensate reserves. The extremely high pressure letdown over the wellhead choke leads to very high flow velocities, and consequent risks of erosion damage occurring to the choke internals. In a recent study, measurements of erosion have been performed during an offshore well test under flowing conditions using advanced Thin Layer Activation techniques and scaled Laboratory tests.
A New Graphical Technique for Well Performance Projections
Authors: Henry William A. , Vest Gary L. , Tyler James C.
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.

This paper presents a technique which combines the Rawling and Schellhardt steady state back pressure equation and the standard pressure decline relationship of a gas reservoir to form a graphical display of a well's ability to produce against any one of a multitude of back pressures. This graphical display is constructed on an individual well basis and summarized to form a graph which represents the producing ability of a reservoir or group of reservoirs. This procedure is performed through the use of procedure is performed through the use of a Burroughs 5500 computer and the results are shown on graphs drawn by a Calcomp plotter. In addition to graphical plotter. In addition to graphical presentations, this information is also stored on presentations, this information is also stored on magnetic tapes which can be used in automated studies. The curves are designed to show deliverability and effective producing time as a function of cumulative producing time as a function of cumulative production against three specified back production against three specified back pressures. An interpolation technique is pressures. An interpolation technique is then employed which will allow any back Pressure between a minimum and maximum Pressure between a minimum and maximum to be utilized. The effective use of these curves will allow an engineer to immediately answer for management such questions as how much gas could a well, field, etc., deliver, assuming certain system requirements such as horsepower, etc., in a specified time interval selected by the user? By generating curves for all wells in a reservoir or field and knowing the appropriate allocation formula, we have investigated the future producing capabilities in light of current or producing capabilities in light of current or future regulatory limitations. By summation of the individual well results into curves representing a reservoir or groups of reservoirs, we make up a composite curve representing a field gathering system attached to our mainline pipeline. Utilizing these gathering system composite curves and an allocation procedure for scheduling gas volumes from procedure for scheduling gas volumes from the individual gathering systems, a total pipeline system availability study against pipeline system availability study against varying market conditions can be made for a specified time period.

Introduction

It is obviously important for the management of any gas transmission company to have the facility to very quickly review their gas supply situation to maintain continuity with a changing market.
Nitrogen Injection Into Stratified Gas-Condensate Reservoirs
Authors: Sänger P. J. , Bjørnstad H. K. , Hagoort Jacques
Published: December 2007

Nitrogen injection is an attractive recovery process for gas condensate reservoirs. It maintains the reservoir pressure and thus prevents condensate drop-out as a result of pressure depletion. A disadvantage is that liquid drop-out occurs in the mixing zone between the injected nitrogen and the gas condensate. This occurs not only at the displacement front, but, due to bypassing, also at the boundary between layers of different permeability.

This paper presents the results of a detailed, high resolution simulation study of nitrogen flooding of a stratified reservoir. The reservoir simulator used is a fully compositional simulator, based on the Peng Robinson EOS. The gas condensate is a 3 component hydrocarbon system that is representative of a North Sea reservoir.

The main result of the study is that in stratified systems severe drop-out (up to 50 percent) may occur at the layer boundaries, in particular just downstream of the trailing displacement front. The latter can be explained by crossflow caused by an unfavourable mobility ratio. It is shown how this mechanism is affected by permeability contrasts, dispersion, aspect ratio and gravity.
Treating of Produced Water for Surface Discharge at the Arun Gas Condensate Field
Authors: Madian S. , Moelyodihardjo Tarwanto , Snavely E. S. , Jan R. J.
Published: December 2007

Mobil's Arun Field in northern Sumatra produces natural gas, hydrocarbon liquids and water condensate. Purification of the water for surface disposal is the subject of this paper.

The Arun waste water contains about ppm of liquid hydrocarbons in the form of a very stable oil-in-water emulsion. Stability of the emulsion is enhanced by the small diameters of the oil droplets, low salt content of the water and low pH. The water is saturated with carbon dioxide and hydrocarbon gases which bubble from the water when pressure is released. Returns of acids, surfactants, emulsifying agents and corrosion inhibitors from acid fracturing operations also contribute to the composition of Arun waste water.

Increases in waste water production, now about 32,000 BPD, and relatively high concentrations of BOD, phenols and ammonia have prompted Mobil to upgrade the Arun waste water treating facilities to protect the receiving bodies of water from contamination.

The upgrade focused on two areas of water treating: 1). removal of suspended liquid hydrocarbons from the water; and, 2). biological oxidation of dissolved organics.

Demulsifier chemical and a skim tank were added to the oil removal facility; the decarbonator and caustic addition before air flotation were eliminated. Without added caustic, the gas flotation unit remove acid gases from the water very effectively. The new skim tank removes over 90% of the suspended hydrocarbons.

The biological oxidation ponds were upgraded by adding barriers to improve plug flow, increasing dispersed air flow, increasing sludge recycle volume, lowering the oil input and by adding nutrients and biological seeding.

Results of the biological pond upgrades are not yet available because increased sludge recirculation and the optimization of biological seeding are not yet completed. Tests of the use of locally-produced biological sludge are planned.
Viscosified CO2 Process: Chemical Transport and Other Issues
Authors: Bae J. H.
Published: December 2007

Supercritical CO2 viscosified by two orders of magnitude using a commercial silicon polymer and toluene as cosolvent, was used in the laboratory corefloods and the results reported previously. More corefloods in Berea cores with pressure taps along the core were conducted to investigate the transport of chemicals in the core. In an attempt to reduce the chemical costs, different silicon polymers and hydrocarbon cosolvents were tried. The effect of methane on the solubility of polymers was also investigated. Scoping economic runs were made by modifying an actual economic analysis of a field CO2 project, which showed that chemical costs have to be reduced significantly for the process to be economic.
Permeability-Dependent Propagation of Polyacrylamides Under Near-Wellbore Flow Conditions
Authors: Zitha P. , Chauveteau G. , Zaitoun A.
Published: December 2007

A new type of polyacrylamide flow-induced retention has been observed in core experiments simulating near-wellbore flow conditions. The retention is due to the bridging of pore throats by adsorbed macromolecules previously stretched under elongational flow. It occurs in low-to-medium permeability granular packs (up to k = 1000 mD in our test conditions) and leads to progressive but severe plugging. The present paper shows that polymer placement in the reservoir surrounding the wellbore can be very different from what is predicted from stable values of polymer mobility. In heterogeneous reservoirs, polymer penetration in low-permeability layers is expected to be strongly reduced, thus allowing a deeper penetration into higher permeability zones. The polymer can thus improve reservoir conformance around the wellbore when injected directly through the entire opened interval. Near-wellbore polymer or gel treatments may thus not require zone isolation to be efficient.
New Chemistry for Chromium-Free Bentonite Drilling Fluids Stable at High Temperatures
Authors: Burrafato Giovanni , Miano Fausto , Carminati Stefano , Lockhart T. P.
Published: December 2007

The broad substitution of aqueous drilling fluids for oil-based muds will require that the performance limitations of current aqueous muds be overcome. The research described in this paper is focused on the most commonly-used aqueous drilling fluids, lignosulfonate (LS03)-dispersed bentonite muds, and addresses two important issues that restrict their wider use: their limited stability at elevated temperature, and their reliance on chromium-containing additives (Cr-LSO3 and Cr-lignite) for control of their rheological properties.

In this paper, new hypotheses regarding the mode of action of Cr(VI) and Cr(III) in Cr-LSO3/bentonite muds are formulated on the basis of new and published experimental observations. Of primary importance are the ideas that (1) LSO3-bound Cr(III) is the form which enhances the thinning power of LSO3 and (2) Cr(VI) stabilizes LSO3/bentonite muds primarily by acting as a latent source of Cr(III). Acting on these hypotheses, it has been found that Cr(III) complexes of appropriate kinetic stability can duplicate the rheology-stabilizing function of Cr(VI). Further pursuit of this coordination chemical approach has led to the identification of a family of Zr(IV) complexes with which chromium-free drilling fluids of outstanding rheological stability can be prepared. The general chemical factors influencing the rheology-stabilizing activity of metal ion complexes are examined. Finally, the unexpected and remarkable thinning power of the Zr(IV) citrate complex is described and its implications for the formulation of novel drilling fluids are briefly discussed.
An Improved Viscosity Equation to Characterize Shear-Thinning Fluids
Authors: Allen Elise
Published: December 2007

An improved viscosity equation is proposed for shear-thinning polymer solutions, using a kinetic approach to model the rate of formation and loss of interactive bonding during shear flow. The bonds are caused by temporary polymer entanglements in polymer solutions, and by coordination bonding in metal ion cross-linked gels. The equation characterises the viscosity of shear-thinning fluids over a wide range of shear rates, from the zero shear region through to infinite shear viscosity.

The equation has been used to characterize fluid data from a wide range of fluids. Recent work indicates that a range of polymer solutions, polymer-based drilling fluids and frac-gels do not have a measurable yield stress, and that the equations which use extrapolated values of yield stress can be significantly in error. The new equation is compared with the Carreau and Cross equations, using the correlation procedure of Churchill and Usagi. It gives a significantly better fit to the data (by up to 50%) over a wide range of shear rates. The improved equation can be used for evaluating the fluid viscosity during the flow of polymeric fluids, in a range of oilfield applications including drilling, completion, stimulation and improved recovery (IOR) processes.
Determination of the Chemistry of HF Acidizing with the Use of 19F NMR Spectroscopy
Authors: Shuchart Chris E. , Buster Douglas C.
Published: December 2007

A more thorough understanding of the chemistry of HF acid and its reaction products on silica and alumino-silicates is essential to the design and optimization of HF acidizing treatments. So far, results from laboratory flow tests and HF acid well returns have not been explained readily by traditional theories. To more clearly define the chemistry of HF acidizing, an indepth investigation of the reaction of HF and H2SiF6 with alumino-silicates was undertaken using 19F Nuclear Magnetic Resonance (NMR) spectroscopy.

In addition to the fluosilicic acid (H2SiF6) and A1F2+ predicted by traditional theories, 19F NMR spectroscopy shows a complex mixture of silicon and aluminum fluoride species in reacted HF acidizing solutions. During a secondary reaction of silicon fluorides with alumino-silicates, a constant F/Al ratio was maintained until the silicon fluorides had reacted completely. The distribution of the fluoride species depends on the HC1 concentration.

In this investigation, a tertiary reaction of HF acid on alumino-silicates was identified. When the silicon fluorides have reacted completely to give silica gel, the aluminum fluoride complexes continue to react on fresh alumino-silicates. The reaction causes the aluminum content to increase and the F/Al ratio and acid concentration to decrease. The final F/Al ratio is dependent upon acid strength and temperature.

Numerous HF acidizing well returns have been analyzed to verify the reactions conducted in the laboratory. The extent of the reaction of HF acid can be determined with the use of 19F NMR spectroscopy. In wells with temperatures of 150 to 200°F, the reaction of H2SiF6 is complete. Silicon content was quite low, and pH levels were 2 to 3. The F/Al ratios of the returns were 0.5 to 1.3, depending on the concentration of HC1 and HF used in the treatment. In wells less than 100°F, the secondary reaction did not go to completion. Silicon and aluminum fluoride complexes were present in the returns along with live HC1.
A Comprehensive Approach for Stimulating Produced Water Injection Wells at Prudhoe Bay, Alaska
Authors: Fambrough J. D. , Lane R. H. , Braden J. C.
Published: December 2007

The paper presents a three-component approach to removing damage from produced water injection wells of Prudhoe Bay Field, Alaska: 1) identification of plugging material, 2) evaluation and selection of potential treatment chemicals, and 3) design and implementation of a well treatment and placement method. Plugging material was sampled anaerobically and kept frozen prior to identification and evaluation. Appropriate treatment chemicals were determined through a series of solvation, filtration, and weight-loss tests. Field treatments were designed so that the treating chemicals entered the formation under normal operating conditions, i.e., at pressures and rates similar to those present during produced water injection. A number of treatments improved injection rates and profiles, but continued injection of oil- and solids-laden water caused deterioration of well performance at rates that precluded general application of the treatment at Prudhoe Bay.
Laboratory Study and Subsequent Field Results of Chemical Stimulation for Use in Open Hole Environments
Authors: LaFontaine-McLarty Jackie , Ali S. A. , Sanclemente L. W. , Sketchier B. C.
Published: December 2007

This paper describes the results of a two-year study conducted to optimize cleanup systems in open hole environments. Specifically, the study originated from problems encountered in the design of a series of open hole horizontal completions and the effort to improve well productivity.