bluuebunny/crossref_metadata_2025_split huggingface dataset:
Beyond The Concrete Gravity Platform
Authors: Mcleod Iain L. 
Published: December 2007

Abstract
Whilst large concrete gravity platforms have been operating successfully in the North Sea since installation of the Ekofisk Tank in 1973, new applications for floating concrete structures are emerging. The first concrete floating structure for the North Sea, an articulated loading column (ALC) for the Maureen field is under completion at the Howard Doris Group Loch Kishorn construction yard in North West Scotland.
Although massive, with for example the 600,000 tonnes displacement of the previous Ninian Central Platform built in the Kishorn dry dock, gravity platforms are required to float during a relatively short construction period. Conversely, the Maureen ALC at 5,000 tonnes displacement, is required to maintain buoyancy throughout its working life. It is thus the pioneer for the future use of concrete in North Sea Oilfield floating structures.
Following from the concrete loading column, the Group have detailed the design of a heavy duty concrete Semi Submersible vessel for the North Sea.
Recent Advances in Cathodic Protection Surveys of Subsea Pipelines
Authors: Backhouse Geoffrey H. 
Published: December 2007

Abstract
Over the last three years, a new system for measuring the cathodic protection potential of subsea pipelines has been developed. The equipment consists of a dual silver/silver chloride electrode probe, mounted on a remote controlled submarine, a silver/silver chloride reference electrode which is maintained at a distance from the pipeline and support ship, and a monitor console. As the submarine moves along, over the pipe, the monitor console records the cathodic protection potential profile and radial field gradient on a continuous chart recorder and also on a strip printer. At intervals, contacts with anode bracelets or bare pipe are used to calibrate the system. A complete potential profile is obtained, together with measurements of current density on damaged areas, and anode output currents.
Typical results obtained from a number of North Sea pipelines are discussed.
Comparison of Preconditioners for the Conjugate Gradient Method in Reservoir Simulation
Authors: Towler Brian F. , Killough John E. 
Published: December 2007

ABSTRACT
Five methods of partial decomposition are compared as preconditioners for the conjugate gradient method for solving the pressure matrix equation of a sequential mode reservoir simulator. Three unsymmetric decompositions, Strongly Implicit Procedure; Dupont, Kendall, Rachford method; and Additional Bands (AB) proved effective and comparable, with AB being the most efficient when used on a scalar computer. The two symmetric Incomplete Cholesky methods did not prove as effective as the three unsymmetric methods.
On the CRAY-1 computer, the SIP-conjugate gradient method was most efficient because it could be vectorized, and in comparison to Red-Black LSOR it was far superior for the example problem considered here.
The insensitivity of the SIP-conjugate gradient method to the iteration parameter was an additional advantage of the method.
Application of D4 Ordering And Minimization In An Effective Partial Matrix Inverse Iterative Method
Authors: Tan Thomas B. S. , Letkeman John P. 
Published: December 2007

ABSTRACT
A new algorithm is presented for solving simulation problems which employs minimization and a partial decomposition of the matrix resulting from an alternate diagonal ordering. The method also maintains material balance in its formulation, important for severely ill-conditioned problems.
The technique has been applied to problems in two and three dimensions with good results and examples are given to show the convergence of the method. Examples include heterogeneous, ill-conditioned problems as well as ones with negative and positive co-efficients. Comparisons are made with currently available methods such as SIP, ORTHOMIN, the semi-direct algorithm of Letkeman and the diagonal method of Watts.
The results show that the new method achieves convergence with less work than the other methods. In two dimensions, Stone's heterogeneous model problem with homogeneous sub-regions was solved with seven equivalent SIP iterations compared with 20.5 for the diagonal method. Coats, problem 1 in three dimensions was solved in 21 equivalent SIP iterations. SIP did not converge for this problem.
Unlike SIP and similar to the Watts’ diagonal method, a sequence of iteration parameters is not required and this feature together with the stability of the method makes it relatively easy to use.
The Mathematical Basis of the Adaptive Implicit Method
Authors: Thomas G. W. , Thurnau D. H. 
Published: December 2007

ABSTRACT
The adaptive implicit method enables a reservoir simulator to choose the degree of implicitness in a grid block to guarantee stability. At any moment different grid blocks can have different degrees of implicitness. As a calculation proceeds these shift in space and time depending on simulator-supplied criteria. The technique can be applied to any simulation problem involving N unknowns. The advantage is substantial reduction in computing time and storage requirements compared to fully implicit formulations.
The mathematical procedure involves labeling the implicit/explicit mix of unknowns and then composing the matrix problem. The latter is reducible as long as there is one or more unknowns to be computed explicitly; consequently, appropriate operations are performed to put it in reduced form. This leads to matrix equations of lower order than the original problem which are solved at less cost. We demonstrate each step of the procedure with an example.
Grid Orientation During Steam Displacement
Authors: Abou-Kassem Jamal Hussein , Aziz Khalid 
Published: December 2007

ABSTRACT
The simulation of oil displacement by steam injection is affected by the orientation of the grid. Under certain situations vastly different results are obtained when grid lines are parallel or diagonal to the line joining an injector-producer pair in a five-spot flood pattern. The same problem exists in the displacement of oil by water under conditions of unfavorable mobility ratio.
Several approaches have been used by investigators to reduce the effect of grid orientation. Three of these are investigated in this paper: (1) use of a nine-point finite-difference operator as opposed to a five-point finite-difference operator, (2) use of the two-point upstream mobility instead of a single-point, and (3) use of harmonic total mobility average for calculation of flow across a boundary.
A compositional, three-phase, two-dimensional steam model was developed to investigate the grid orientation problem during steam displacement.
A realistic steam displacement problem for a highly viscous oil reservoir was selected for detailed study. The effects of grid orientation on important primary variables and recovery performance curves are presented for this problem. It is shown that, at least for the problem considered, the nine-point scheme alleviates the effect of grid orientation, while the two-point upstream mobility and the harmonic total mobility approaches aggravate the problem. It is also shown that use of the two-point upstream mobility is not appropriate for thermal process simulation. The present model does not suffer from the " bullet-like" displacement front reported by other investigators.
The test problem was chosen to maximize the effect of grid orientation.
Source Distributed Fracture Model for the Numerical Modelling of Oil Sands Steam Stimulation
Authors: Geshelin Borys Michail , Grabowski Janusz Wojciech 
Published: December 2007

ABSTRACT
This paper describes a source distributed dynamic fracture model. The model, coupled with the thermal simulator ISCOM, was used to investigate oil sand reservoir performance during steam stimulation.
The source distributed fracture model developed is based on the following assumptions: The fracture can propagate through a given path of adjacent reservoir blocks, creating a fracture channel within a reservoir. The number of fracture channels and reservoir geometry are not restricted. The position of a fracture or microfracture system inside a given reservoir block is not defined - the fracture is represented as an effective source of fluid and heat transferred to the block. Fracture volume is disregarded. The mass and heat balances are solved exactly for each fracture channel. Fractures can be operational only during the injection period. Fracture opening and closure are governed by calculated values of opening, propagation and closure pressures. Effective absolute permeability and conductivity inside a drainage area are treated as adjustable parameters.
Results of this investigation show that reservoir performance is strongly affected by the variation of effective fracture parameters, especially changes in effective fracture conductivity in the vicinity of a wellbore and the mobile and connate water saturations.
Solution of Pressure Equations for Large Reservoir Models Using Block Successive Overrelaxation and an Array Processor
Authors: Emanuel Alan S. , Lee Seong H. , Chung Ernest Y. 
Published: December 2007

ABSTRACT
Block successive overrelaxation is used to solve the pressure equations of large 3-dimensional reservoir models with limited or zero permeability between layers. Each block consists of several vertical planes of the model. Composing the blocks of vertical planes allows wellbore pressure equations to be included along with the reservoir cell block equations to implicitly couple wellbore pressure to reservoir grid block pressure. The equations for each block are solved simultaneously using sparse elimination techniques. The work of factorization, forward and backward substitution is transferred from the host computer to an attached array processor. The host computer is an IBM 168 or a VAX 11/780, and the attached processor an FPS 190L or FPS 120B.
For large anisotropic multi-layer models with limited vertical permeability between layers, the block technique shows two or three times better convergence than plane SOR. Convergence may be further improved by overlapping a few planes in adjacent blocks. Host computer CPU time and cost may be reduced by up to a factor of two to five for these models. Two hypothetical test problems and three reservoir problems are described.
A Study on Some New Water-Soluble Copolymers and Polymer Blends Used for Exploitation of Oil Field
Authors: Xi Xu , Qin-gong He , Qi-jiang Zhuo , Wei-you Mao 
Published: December 2007

ABSTRACT
Some water-soluble copolymers used for oil recovery were prepared by copolymerizing acryloraide and acrylonitrile using ammonium persulfate as initiator. The properties of the mixed aqueous solution of a natural and synthetic polymer blend (carboxymethyl cellulose-partially hydrolyzed polyacrylamide) were modified by ultrasonic technique, a new type material for oil field exploitation is thus provided. In addition, the gel characteristics of several etherified poly(vinyl alcohol) and their blends were also studied in this paper, some new applications of poly(vinyl alcohol)were exploited.
Scale Inhibition for Injection of Incompatible Waters
Authors: Vetter O. J. , Kandarpa V. 
Published: December 2007

ABSTRACT
The utilization of scale inhibitors is the most common and promising method of combatting the scale problems in oil and gas field operations. The extension of the scale inhibition technique to geothermal operations faces some problems mainly due to the high temperature and high salinity of the brines. In addition, the injection of foreign waters and their associated mixing of incompatible waters give rise to some additional problems in chosing proper inhibitors. The brines resulting from incompatible water mixing contain non-equilibrium concentrations of anionic and cationic species and sometimes at extremely high supersaturations of scale forming compounds.
The present paper gives the results of evaluating commercially available inhibitors in preventing CaSO4 and BaSO4 precipitation from supersaturated solutions. Four different types of commercial inhibitors have been chosen for this evaluation. They are phosphonates, polymaleic acids, polymers and phosphate esters. The conditions chosen for the evaluation represent the conditions found in the injection wellbore (for CaSO4 precipitation) and at the surface facilities of the producing well (for BaSO4 precipitation). The effect of the presence of iron in the producing brine on the efficiencies of the inhibitors were also studied as part of the present work.
Several inhibitors have been found to perform with high efficiencies againat CaSO4 precipitation at 135°C from solution at a supersaturaion of 8. In general, the phosphonate based inhibitors have been found to perform better than the inhibitors based on polymers, pbosphate eaters and polymaleic acids.
All the inhibitors performed poorly against BaSO4 at high supersaturations. Using high concentrations of the inhibitors and/or mixtures of some specific inhibitors, their efficiencies have been brought to values larger than 0.6. However, the presence of iron in the brine solution caused drastic decreases in the efficiencies of even the best inhibitors and inhibitor mixtures. In the presence of iron, Dequest 2010 (phosphonate inhibitor) in combination with a few of the other inhibitors showed efficiencies larger than 0.4 for times greater than 4 hours. At 120°C the time for failure of the inhibitors is 2 hours or less in the presence of iron.
The paper gives all the data in the form of tables.
Salinity Tolerance and Solution Property Correlations of Petroleum Sulfonate-Cosurfactant Blends
Authors: Shankar P. K. , Bae J. H. , Enick R. M. 
Published: December 2007

Abstract
A petroleum sulfonate (Petrostep 465/420) was combined with commercially available ethoxylated and other cosurfactants. Salt tolerance, phase volume behavior, interfacial tensions, and viscosities were measured; correlations among these parameters are presented for the 21 systems studied. Salinity tolerance levels as high as 120 g/kg NaCl, optimal salinities as high as 95 g/kg NaCl, and ultralow interfacial tensions on the order of 1 × 10-4 mN/m were exhibited by some systems. Optimal salinities were accompanied by ultralow interfacial tensions and lower microemulsion viscosities only when the range of salinity over which the three-phase region persisted was narrow. Furthermore, some systems were characterized by almost 95% microemulsion volume at optimal salinity. The width of the three-phase region decreased as the middle-phase microemulsion volume at optimal salinity increased. Consequently, the microemulsion viscosities were lower for systems that displayed a narrower three-phase region. It was also concluded from our results that optimal salinity does not necessarily occur at the middle of the three-phase region. For most of the systems studied, it occurred at lower values. The plots for the interfacial tension versus solubilization parameter were similar to those reported by Reed and Healy.13 The interfacial tension between the microemulsion phase and the excess phases was correlated with the excess phase volumes. We also found that the interfacial tension between the excess oil and brine was close to and parallel to that between the microemulsion and excess brine phases.
Clay Stabilization — Criteria for Best Performance
Authors: Hill Donald G. 
Published: December 2007

ABSTRACT
A recent study has demonstrated the importance of cation exchange capacity in determining optimum use concentrations of cationic clay control agents.
Determining the concentration of polymer required to adequately stabilize clays is dependent upon many factors. Normally, the concentration required for clay control is based only on the clay content of the reservoir. In addition to the clay content, careful consideration should also be given to the type of clay, the natural wettability of the reservoir, the adsorbed cations in equilibrium with the formation, the treating fluid and the additive concentration in the treating fluid. It is important to consider all of these factors for each reservoir to be treated; however, some of the factors may not be known. The most important factor is the cation exchange capacity of the reservoir rock. This may be determined in the laboratory and used to predict the required concentration of the cationic additive to obtain stabilization.
Filtration of Oil Field Brines — A Conceptual Overview
Authors: Sharp Keith W. , Allen Barrington T. 
Published: December 2007

Abstract
The use of solids free brines as completion/work-over fluids has given rise to the need for methods of fine solids removal. Filtration of clear brines has become a major concern to operators. This paper will address the problem of removal of fine suspended particles in the .5-50 micron range.
The body of the paper deals with the removal of fine solids by flow through porous media. The mechanics of removal discussed include sieving, bridging, adsorption, and settling within the porous matrix. Parameters such as flow density or velocity and pressure drop will be defined. Each of the removal mechanisms will be discussed in terms of how the operational parameters affect filtration efficiency. A discussion of surface and depth filtration will be included. Also, performance parameters such as effluent quality, dirt capacity, and clear pressure drop will be discussed. Design of the porous media will be covered along with a discussion of how filters are rated. Current filtration techniques used in the oilfield will be reviewed and classified. The classification will include the type of removal mechanism whereby the specific filter operates, the effect of operating conditions on efficiency, and what kind of performance can be expected.
Nondamaging Fluid Loss Additives for Use in Hydraulic Fracturing of Gas Wells
Authors: Penny Glenn S. 
Published: December 2007

Abstract
An effective fluid loss control measure that has recently found application in the hydraulic fracturing of gas wells is the addition of an iramiscible hydrocarbon phase to aqueous fracturing fluids. In this work the effectiveness and regained permeabilities after employing hydrocarbon and common particulates are assessed. Laboratory studies indicate that reduced hydrocarbon concentrations (&lt;5%) may be beneficial in achieving efficient fracture cleanup. A detailed evaluation of the parameters controlling fluid loss of an immiscible hydrocarbon phase in aqueous fluids has led to an optimized hydrocarbon-surfactant system, with which excellent regained permeabilities and efficient fluid loss control are achieved at reduced hydrocarbon concentrations.
Short Interval Gravel Packing Technique
Authors: Sokoll Robert Edward , Rogers Alan Kent 
Published: December 2007

SUMMARY
Conventional slurry packing methods involve a screen and from 120′ to 160′ (36.5m to 48.7m) of blank pipe above the screen. The blank pipe acts as a sand reservoir for the gravel pack screen. Sand settles after the gravel pack is completed and after the gel breaks. To help ensure a good gravel pack job in a well that has less blank pipe than screen, a multiple stage slurry pack process was designed along with a multiple stage crossover tool.
Alteration of Rock Properties by Adsorption of Petroleum Heavy Ends: Implications for Enhanced Oil Recovery
Authors: Clementz David M. 
Published: December 2007

ABSTRACT
Clay mineral properties are irreversibly altered by adsorption of petroleum heavy ends. As a result of this alteration, rock sensitivity to injected fluids is reduced; rock wettability is changed from "water wet" to "neutral"; adsorption of surfactants is reduced; rock property measurements are changed; and cores can be irreversibly altered. All of these changes can affect enhanced recovery processes and related laboratory studies.
The extent of this interaction has been found to depend upon the type of clay minerals present in the rock, the composition of the petroleum heavy ends, and the interaction environment. After the adsorption occurs, a clay-organic complex is formed which is hydrophobic and very stable. Expansion of swelling clays is reduced and clay surface area and cation exchange capacity are reduced.
Practical implications of these observations are demonstrated in Berea sandstone cores and in friable California sand cores when the clays were stabilized against dispersion and subsequent migration. Berea sandstone permeability is rendered insensitive to fresh water and the friable sand, in which clays are the primary cementing material, is stabilized against failure under increased flow rates. In other studies, surfactant adsorption on montmorillonite was found to be three to ten times lower when the clay was pretreated with petroleum heavy ends. Surfactant retention in clean Nevada sand is also reduced when a surface layer of heavy ends is present on the sand grains.
The Modelling of Multisegment Production Profiles Using Hybrid Systems and Ordinary Differential Equations
Authors: Haavardsson Nils F. , Huseby Arne Bang 
Published: December 2007

Abstract
When an oil- or gasfield project is evaluated, it is crucial to have a satisfactory model for the production. Knowledge about the properties of the reservoir should be included in such a model. When used in a total value chain analysis, however, also economic and strategic factors need to be taken into account. In order to do this, more flexible modelling tools are needed. In this paper we demonstrate how this can be done using hybrid system models. In such models the production is modelled using ordinary differential equations representing both the reservoir dynamics as well as strategic control variables. The approach also allows us to break the production model into a sequence of segments. Thus, it is possible to represent various discrete events affecting the production in different ways. The flexibility of the modelling framework makes it possible to obtain realistic approximations to real-life production profiles. As the calculations can be done very efficiently, the framework can be incorporated in a full scale uncertainty analysis based on Monte Carlo simulation.