bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting Phase Behavior of Mixtures of Reservoir Fluids With Carbon Dioxide
Authors: Grigg R. B. , Lingane P. J.
Published: December 2007

The use of an equation of state to predict phase behavior during carbon dioxide flooding is well established (see, for example, Yarborough20 and Whitson21 and references therein).

There is consensus that the characterization of the C7+ fraction, the grouping of this fraction into "pseudo components," and the selection of interaction parameters are the most important variables. However, the literature is vague as to how to best select the pseudo components, especially when aiming for a few-component representation as for a field scale compositional simulation.

Single-contact phase behavior is presented for mixtures of Ford Geraldine (Delaware), Maljamar (Grayburg), West Sussex (Shannon), and Reservoir D reservoir fluids, and of a synthetic oil C1/C5/C16, with carbon dioxide.

One can reproduce the phase behavior of these mixtures using 3-5 pseudo components and common interaction parameters. The critical properties of the pseudo components are calculated from detailed oil characterizations. Because the parameters are not further adjusted, this approach reduces the empiricism in fitting phase data and may result in a more accurate representation of the system as the composition of the oil changes during the approach to miscibility.
Synergy of Core Petrophysigal Measurements, Log Data, and Rock Examination in Carbonate Reservoir Studies
Authors: Nurmi Roy D. , Frisinger M. Rusty
Published: December 2007

The pore system characteristics of a wide range of limestone rock types have been reviewed including: reef skeletal framework, chalks, calcareous sands, and mud-stones with and without the presence of grains. The emphasis of the present discussion is on carbonate reservoirs that originated as calcareous sands. A synergistic study of the geological, petrophysical, and logging data of these rocks provided insight into their reservoir characteristics. For example, the geological analysis of porosity/ permeability crossplots on semi-logarithmic paper produced linear, or at least discrete, trends for each different depositional rock types. Furthermore, the attempts to understand the underlying relationships between the porosity and permeability of these depositional rock types also permitted a better understanding of the affects of diagenesis, dolomitization, and fracturing in more quantitative terms.

The diagenetic, or secondary, creation of porosity in carbonates, including grains tones, is quite common. In cases of moldic porosity and intragranular microporosity in grainstones this secondarily created porosity can be relatively isolated from the intergranular pore system. The secondary fraction of the pore volume was recognized and quantified through the analysis of porosity/permeability plots and SEM examination of the core and pore casts. Since this pore system data is relatable to the geological rock types and facies mapped and modeled by geologists, it is then possible to better understand the large-scale distribution of pore types and permeability. Furthermore, when the more thorough understanding of carbonate pore systems is related to the well-log data there is an improvement both in interpretation of logs and in the ability to map reservoir and depositional units.
Comparison of Uniaxial Strain and Hydrostatic Stress Pore-Volume Compressibilities in the Nugget Sandstone
Authors: Lachance D. P. , Andersen M. A.
Published: December 2007

This paper presents a comparison of rock compressibilities determined under two different stress states. One stress state was the traditional though unrealistic hydrostatic stress method; the other was the more realistic though more complicated uniaxial strain (triaxial stress) with pore pressure method. Compressibilities were determined by both stress methods on Nugget sandstone core plugs from the Rocky Mountain Overthrust Belt. The resulting relationship between the two types of compressibilities did not match with previously published predictions.

The uniaxial strain pore volume compressibilities averaged about one-third of the corresponding hydrostatic stress pore volume compressibilities. This was a greater difference than predicted using standard practices. Also, the uniaxial strain data varied only slightly between samples, while the hydrostatic stress data exhibited a greater range of values. From the uniaxial strain measurements, bulk volume compressibility of the Nugget sandstone is constant over the porosity and pressure range of the reservoir. Pore volume compressibility can therefore be easily determined from the porosity and the bulk volume compressibility.
Design and Operation of a CO2 Tertiary Pilot: Means San Andres Unit
Authors: Stiles L. H. , Chiquito R. M. , George C. J. , Long L. D.
Published: December 2007

This paper describes the design, implementation and operation of a CO2 tertiary pilot in the Means San Andres Unit, Andrews County, Texas. The pilot consisted of five wells on 1.5 acres. Detailed geological studies showed the reservoir to be more heterogeneous than broader studies had indicated. Pilot operations and evaluation were complicated by a dual permeability zone. Special tests to define this interval are described. Evidence of additional oil recovery was shown from both log analysis and fluid samples.
Frictional Pressure Losses for the Flow of Drilling Mud and Mud/Gas Mixtures
Authors: Langlinais J. P. , Bourgoyne A. T. , Holden W. R.
Published: December 2007

The calcuation of single phase and two phase flowing pressure gradients in a well annulus is generally based on an extension of empirical correlations developed for Newtonian fluids in circular pipes. Various techniques for extending pipe flow correlations to an annular geometry have been presented in the literature which involve the representation of the annular well geometry with an equivalent circular diameter and the representation of non-Newtonian fluid behavior with an apparent Newtonian viscosity. Unfortunately, little experimental data have been available which would allow a comparison of the relative accuracy of the various proposed techniques.

In this study, experimental pressure gradient data have been taken in two 6000 ft. wells. Frictional pressure losses for single phase flow (mud only) in two annuli were compared to values predicted by the Bingham Plastic and Power law Models. These calculations utilized the equivalent diameters defined by the Crittendon criteria, the hydraulic radius, and the slot approximation. Also, total pressure difference for two-phase flow was measured for one annular geometry. This data was compared to that predicted by the Poettmann and Carpenter, Hagedorn and Brown, Orkiszewski, and Beggs and Brill correlations.

Comparison of experimental data with the various prediction techniques was favorable, each having advantage in certain situations. For the data investigated, the Crittendon criteria using a Bingham Plastic Model gave the best results. The two phase flow data was best predicted by the Hagedorn and Brown correlation utilizing a hydraulic radius equivalent diameter.
A Laboratory Study of the Tapered-Quality Steam-Water Process on a Light Oil
Authors: Cheung Y. L. , Brown Alfred , Huang W. S.
Published: December 2007

The tapered-quality steam-water process, in which steam injection is converted to water injection via gradually decreasing steam qualities, is described. Laboratory tests performed in linear sand packs on a 43°API gravity crude oil show that (1) steam injection is very effective in recovering light oil, and (2) the tapered-quality steam-water flood is at least equal to, and potentially better than, the conventional steam flood in energy efficiency.
Rheological Characterization of Crosslinked and Delayed Crosslinked Fracturing Fluids Using a Closed-Loop Pipe Viscometer
Authors: Gardner D. C. , Eikerts J. V.
Published: December 2007

A closed-loop, high-temperature pipe viscometer was used to evaluate the effects that shear intensity, shear duration, temperature, and time have on the apparent viscosity of cross-linked fracturing fluids. Results indicate that much higher gel viscosity can be obtained in the fracture with certain types of delayed cross-linking agents than can be achieved with most of the conventional titanate cross-linkers so widely used in the industry. The maximum achievable apparent viscosity reached by either the titanate or zirconate cross-linked gels studied appears to be most affected by the level of shear or energy input encountered during the initial cross-linking phase.
A Multi-Function Compensated Spectral Natural Gamma Ray Logging System
Authors: Smith H. D. , Robbins C. A. , Arnold D. M. , Gadeken L. L. , Deaton J. G.
Published: December 2007

A natural gamma ray spectroscopy togging system has been designed which incorporates active compensation for differences in borehole conditions into the least squares calculation of the K-U-Th elemental concentrations. A low atomic number toolcase allows gamma rays in the photoelectric energy region to be detected, while a coincidence gain stabilization technique distinguishes formation gammas from those originating in the stabilizer source. These features permit additional measurements of formation lithology in open holes and mean casing thickness in cased wells.
A Simplified Method for Water Coning Predictions
Authors: Kuo M. C. T. , DesBrisay C. L.
Published: December 2007

Numerical simulation was used to determine the sensitivity of water coning behavior to various reservoir parameters. The simulation results were then used to develop a simplified correlation for water coning predictions. The correlation is general since the sensitivity studies cover a wide range of reservoir parameters (ratio of vertical to horizontal permeability from 0.01 to 1.0; perforated interval from 20 percent to 80 percent of oil zone thickness; production rate from 500 to 2000 RB/D gross fluid; mobility ratio from 1.0 to 10). The correlation is valid to predict watercut performance for most reservoirs with strong bottom water drives except those with local barriers present, those with a high degree of stratification (Dykstra-Parsons Permeability Variation > 0.8), or those with a thick oil-water transition zone.

With the correlation programmed on a hand-held calculator, field engineers can conveniently predict critical rate, breakthrough time and watercut performance. Compared to complicated numerical models, the correlation is particularly useful when detailed reservoir data are not available, or when decision time and project cost are limited. Field engineers can use the simplified correlation to compare watercut performance for various operating strategies and make appropriate decisions for production operations.
Predicting Gas Well Performance Coning Water in Bottom-Water-Drive Reservoirs
Authors: Kabir C. S.
Published: December 2007

Depletion strategy of a gas reservoir underlain by an active water drive requires careful thought and planning. Producing rate and completion interval are the apparent key considerations in a depletion scheme because of the potential water coning that may affect the ultimate recovery. As this study indicates, both the considerations are relatively unimportant from the stand point of theoretical ultimate recovery.

The primary purposes of this investigation are to develop an analytical solution for the water coning problem and to provide guidelines on the depletion strategy in thin reservoirs (< 60 ft). A systematic study of the variables indicates that permeability and pay thickness are the most important variables governing coning phenomenon. Other variables such as penetration ratio, horizontal to vertical permeability ratio, well spacing, producing rate, and the impermeable shale barriers have very little influence on both the water-gas ratio response and the ultimate recovery.

Generalized analytical solutions that are developed in graphical form, using a numerical coning simulator, allow a multitude of calculations. These calculations include predicting a well's behavior with or without a production history, determining an economical withdrawal rate, generating a rate-time profile, and estimating a breakthrough time. The type curves could also be used as a diagnostic tool to identify possible completion problems.
Technical Screening Guides for the Enhanced Recovery of Oil
Authors: Taber J. J. , Martin F. D.
Published: December 2007

The technical screening guides which are used to select enhanced oil recovery methods are described. The background and logic behind the various criteria are covered, and a brief description of each method is included. Economics are discussed, but the emphasis is on the technical guidelines.

A distinction is made between the oil properties and reservoir characteristics required for each process. Generally, steamflooding is applicable for viscous oils in relatively shallow formations. At the other extreme, CO2, nitrogen, and hydrocarbon miscible flooding work best with very light oils at depths great enough for miscibility to be achieved. Both steamflooding and in-situ combustion require reservoirs of fairly high permeability. Chemical flooding processes (polymer, alkaline or surfactant) are applicable for low-to-medium viscosity oils where depth is not a major consideration. However, at great depths, the higher temperature may present problems in the degradation or consumption of some of the chemicals.

Current values of the technical screening guides for the more common enhanced recovery procedures are given in tabular and graphical form. By the use of a simple graphical technique, it is shown that there is a complete spectrum of enhanced oil recovery methods available for all oils, ranging from the very lightest to the heaviest oil or tar sand.
A Three-Dimensional Well Planning Method for HDR Geothermal Wells
Authors: Scholes Haydn
Published: December 2007

This paper presents a method for planning sections of directionally drilled wells in three dimensions where azimuth and inclination is specified at the end points. It describes the implementation of the algorithm in a computer code and its use at the Camborne School of Mines Geothermal Energy Project for planning a proposed third well in an existing hot dry rock geothermal reservoir.
Combining Production History and Petrophysical Correlations to Obtain Representative Relative Permeability Data
Authors: Meads Roosevelt , Bassiouni Zaki
Published: December 2007

Prediction of gas reservoir performance under water drive is very sensitive to relative permeability data. Gas-water relative permeability ratio (Kg/Kw) at different values of water saturation (Sw) can be derived from production history. This technique provides data considered the most representative of reservoir characteristics since it reflects actual reservoir performance. However, the developed (Kg/Kw) vs Sw curve is only valid in the higher range of water saturation and in the absence of water coning and other forms of water intrusion. The valid portion of the curve can be used to calibrate a generalized correlation. The calibrated correlation is then used to derive relative permeability data over the entire water saturation range. The technique discussed can also be applied to oil-water systems.
Recovery Efficiency of Enhanced Oil Recovery Methods: A Review of Significant Field Tests
Authors: Hammershaimb E. C. , Kuuskraa V. A. , Stosur George
Published: December 2007

This paper analyzes past enhanced oil recovery (EOR) projects to determine how well they have performed as a function of reservoir and process variables. In total, over 100 key tests covering the following six major enhanced oil recovery techniques are analyzed: Steam Drive, In-Situ Combustion, Carbon Dioxide Flooding, Polymer Flooding, Surfactant/Polymer Flooding, and Alkaline Flooding.

The analysis includes, by technique and geographical area: The range of oil recovery due to EOR in barrel s per acre-foot and as a percentage of oil remaining in-place.A comparison between predicted performance and actual oil recovery.An examination of the performance of different EOR processes within each of the six techniques.An analysis of the relation of reservoir parameters and process variables to oil recovery.
Limitations on the Use of Single- and Multiple-Rate Horner, Miller-Dyes-Hutchinson, and Matthews-Brons-Hazebroek Analysis
Authors: Larsen Leif
Published: December 2007

A major objective of this paper is to present methods to determine the range of applicability of Horner and Miller-Dyes-Hutchinson analysis for a variety of reservoir shapes, outer boundary conditions, and producing times. This concerns limitations on the end of semilog data caused by approximations of the drawdown transient, and not limitations on the beginning of such data caused by effects in or near the wellbore. The results, based on derivatives of dimensionless pressures, also have some bearing on the use of drawdown type curves to analyze buildup data. Moreover, they imply that the "producing time" used in Horner analysis, or in type-curve analysis based on Agarwal's effective drawdown time, can be limited by tDA =0.08 for closed reservoirs. This is important when use of later portions of test data are essential to obtain valid results.

Limitations on the use of standard methods to determine the distance to the nearest boundary in closed reservoirs, both for short and long producing times, are also investigated. From an example presented, it is evident that exact doubling of the semilog slope is not necessary to determine this distance, but such doubling simplifies the analysis. This is important since exact doubling only occurs under favorable conditions.

Both Horner and Matthews-Brons-Hazebroek analysis have natural extensions from single- to multiple-rate buildup data. This leads to a formula relating the extrapolated pressure to the average reservoir pressure through a sum of Matthews-Brons-Hazebroek functions. Using the results from the first part of the paper, it follows that a single-rate Horner plot can be used if all drawdown transients have lasted longer than tDA = 0.08, even if a longer producing time is needed to reach pseudosteady state.
The Role of Well Log Interpretation in Well Completion of Naturally Fractured Reservoirs
Authors: Hirakawa S. , Yamaguchi S.
Published: December 2007

In planning well completion methods of wells in naturally fractured reservoirs, some problems relating to fractured zones must he considered and solved.

At first, an accurate detection of fractured zones plays an important role for the decision of completion methods. The former part of this paper presents two kinds of possible algorithm for analyzing well logs in a naturally fractured oil or geothermal reservoir. These two kinds of algorithm are applied to actual logs for the detection and quantitative evaluation of fractured zones and their availability is shown.

Secondaly, when one decides the full string completion, the completion schemes such as perforation zone must be investigated, for they affect the production performance of fractured reservoirs. The latter part of this paper mainly describes the effects of perforated zone on the production performance with typical examples of natural or artificial water drive reservoir problems.
Fluid-Loss Control in the Naturally Fractured Buda Formation
Authors: Hall B. E. , Houk S. G.
Published: December 2007

The Buda fonnation is a naturally fractured limestone. Initial production is limited by low matrix permeability and possible plugging of existing natural fractures during the drilling and completion of the wells. Consequently, proppant fracturing is an integral part of the completion of Buda wells.

Within the last year. Gulf Oil Exploration and Production Company has completed 12 wells in the Buda lime. During the fracturing treatments, 4 screenouts occurred on the first 7 wells treated. Laboratory data indicated that a different fluid loss program minimize screenouts in naturally fractured reservoirs. This technology was applied to the Buda wells. Using 100 mesh particles in conjunction with fine oil soluble resins, only 1 screenout was observed in the next 5 treatments. Laboratory data, treatment design, and well performance are presented in this paper.
Effect of Wettability on Two-Phase Relative Permeabilities and Capillary Pressures
Authors: Heiba A. A. , Davis H. T. , Scriven L. E.
Published: December 2007

The percolation theory of two-phase relative permeability at low capillary numbers (SPE 11015) is further developed to account for the physics of intermediate and mixed wettability in reservoir rocks. The elements of the theory are: a network representation of porespace connectivity; a distribution function description of porespace geometry; capillary pressure (i.e. quasistatic) and wettability criteria of allowability of the invading phase to poresegments according to their throat or body size; a Bethe network approximation to pore space connectivity, to estimate occupancy-conditioned poresize distributions that follow from the preceding elements and lead to occupancy-conditioned distributions of segment volumes (for saturations) and hydraulic conductances (for permeabilities); and a Bethe network transport path conductivity function for creeping flow of each phase that occupies continuously connected pore-segments. Also included is the volume occupied by virtually stationary thin films and pendular structures of the more strongly wetting liquid. Wettability is expressed in the capillary pressure criterion of allowability and acts through the pore-filling sequence in any displacement process. The theory reveals how pore-filling sequences depend on capillary pressure.

The theory predicts the saturation-dependent and saturation-history-dependent capillary pressure and relative permeability relations measured by Morrow and coworkers in uniformly wet porous media. Applied to reservoir rock in which a fraction of poresegments previously occupied by oil have become oil-wet, the theory, with that fraction a variable, accounts for the continuous spectrum of capillary pressure and relative permeability curves encountered in reality.

Parameter estimation from limited data will be treated elsewhere. The theory is so founded that it can be extended to three-phase relative permeabilities, as will be reported in a sequel.
Fundamentals of Relative Permeability: Experimental and Theoretical Considerations
Authors: Heaviside John , Black C. J. J. , Berry J. F.
Published: December 2007

Studies investigating the validity of the conventional description of two phase immiscible flow are reported. Laboratory techniques for relative permeability determination have been applied in well controlled experimental conditions to strongly wetting systems. The tests enable a definite description of drainage and imbibition displacement processes. Concurrently a numerical model, based on the conventional macroscopic flow equations was developed to simulate the dynamic displacement tests. The purpose was threefold; 1) To study the concept of relative permeability 2) To simulate the physical processes occurring during unsteady state displacement tests 3) To use the model to assist in the provision of laboratory data more relevant to reservoir simulation.

The results show the relative permeability concept is valid for drainage displacement. For imbibition processes the concept is not strictly valid and the macroscopic flow equations are limited in their ability to describe the physical process. Consequently the relevance of laboratory data derived using this conventional theoretical framework is limited and its applicability to the reservoir will depend upon the selection of the appropriate tests. Guidelines as to the selection of the laboratory tests suitable for the different occasions are given and illustrated with a small number of field cases.
Exact Kinematic Analysis of Pumping Units
Authors: Svinos J. G.
Published: December 2007

A new pumping unit Kinematic Analysis method was developed for the calculation of position, velocity, acceleration of the polished rod, and torque factors as functions of crank angle. This method can also be used to calculate the angular position, velocity and acceleration of any part of the pumping unit mechanism.

It is more accurate than previous methods because it produces exact results. It can be used to compare pumping units, and can analyze units with varying crank speeds. It can improve gearbox torque analysis by including inertia effects, and can allow the use of conventional dynagraphs for the prediction of downhole dynagraphs.
Controlling Numerical Diffusion in Reservoir Simulation Using Flux Corrected Transport
Authors: Carr A. H. , Christie M. A.
Published: December 2007

Flux Corrected Transport (FCT) is a technique developed to reduce numerical diffusion around shock fronts which has not previously been used in reservoir engineering. The first section of this paper describes the application of FCT techniques to solving a one dimensional waterflooding problem, and shows how to include FCT in an IMPES simulator. A second feature of our program is the implicit timesplit treatment of capillary pressure effects. A comparison between laboratory data and simulator results is included, and good agreement is obtained.
Random Choice Method for Treating the Convection-Diffusion Equation
Authors: Li K. M. G.
Published: December 2007

A numerical method is developed for solving the convection-diffusion equation arising from the conservation equations used to represent miscible displacement processes. This method is superior to the conventional finite difference methods in that it introduces only a negligible amount of numerical dispersion, in contrast to the significant numerical smearing introduced by most finite difference techniques.

The construction of the method is based on the method of operator splitting; the first fractional step solves the convection equation with zero diffusion, whereas the second step accounts for the diffusive part of the convection-diffusion equation. Unlike conventional finite difference methods, which approximate the convection term by some form of upwind differencing scheme, the present approach calculates the convective flow by the random choice method in the first fractional step. The advantage of this approach is that it propagates the solution correctly without smearing out the displacement front, regardless of the grid size. This desirable feature is absent in most finite difference techniques, and as a result they are unable to model the physical dispersion accurately. In the second fractional step of the method, the parabolic character of the diffusion term is appropriately approximated by the conventional central differencing scheme.

The combined scheme is unconditionally stable. Extensive numerical tests show that the method is able to approximate the convection-diffusion equation accurately without introducing any significant numerical dispersion. No spurious oscillation is observed even at small values of the diffusion coefficient. In the limit when the diffusion coefficient approaches zero, a perfectly sharp displacement front is calculated. Extension of the method to multidimensional problems is possible by the use of operator splitting, which reduces the problem to fractional steps of locally one dimensional problem.
Front Tracking for Petroleum Reservoir Simulation
Authors: Glimm James , Lindquist Brent , McBryan O. A. , Plohr Bradley , Yaniv Sara
Published: December 2007

The front tracking method gives high quality solutions for problems with important discontinuities. The method has been applied to several model problems in reservoir simulation. Results are given for quarter 5-spot studies in an areal reservoir and the water coning problem in a vertical cylindrical section surrounding a production well. Both problems were treated as incompressible flow in the absence of capillary pressure. We have studied miscible and immiscible displacement for frontal mobility ratios of 1 and 5. Validation studies include mesh refinement, grid orientation and orthogonal coordinate changes.
A New Equilibrium Coefficient Correlation Method for Compositional Simulators
Authors: Chien M. C. , Lee Sheng-Tai
Published: December 2007

A new equilibrium coefficient or K-value correlation useful in compositional simulation studies was developed to reduce computing times in phase equilibrium calculations while retaining good accuracy in the calculated results. This correlation is based on the convergence pressure concept. Unlike previous works, the mixture critical pressures are correlated from binary critical pressures, the convergence pressures are correlated by treating the mixture as a pseudo-binary mixture, and the functional form of this correlation was derived by considering the asymptotic behavior of K-values. In the low pressure region, it reduces to the Chao-Seader correlation. In the near critical region, it conforms to the critical exponent theory. The correlation is related to the overall fluid composition explicitly, and requires no iteration.

This correlation has been tested for three different reservoir fluid systems. The K-values calculated using the new correlation are in good agreement with those using the calibrated Peng-Robinson Equation of State (P-R EOS). The average deviation is less than 3% for the reservoir fluid systems studied. Slim tube displacement simulations, using CO2 and nitrogen as the displacing fluid, were also performed for the three reservoir fluid systems to validate the correlation developed. The predicted oil production rates using the new correlation to calculate phase equilibria are in good agreement with those using P-R EOS. The average deviation is less than 3%; at the same time, the computational cost is reduced by 4 – 14 times.
Some Observations on Field-Scale Simulation of the In-Situ Combustion Process
Authors: Coats K. H.
Published: December 2007

This paper describes and illustrates a method for ensuring sustained combustion in coarse-grid, field-scale simulation using a kinetic-based model. For the example problem treated, as in several unreported cases, the method considerably extends the grid block size which can be tolerated without severe grid size effects. The method is applicable only in cases where one accepts the assumption that no free oxygen passes unreacted through the combustion front.

The paper also presents and discusses results of very fine-grid one-dimensional simulations. Comparison of these fine-grid results with coarse-grid 1D results shows, for the particular problem data used, an unexplained, significant increase in amount of oil cracked with grid block size increased over the range of .5 feet to 10 feet.

2D areal, 5-spot pattern simulations show that the 9-point difference scheme very significantly reduces a large grid orientation effect in 5-point simulation of the combustion process.
A Consistent Method for Calculating Transmissibilities in Nine-Point Difference Equations
Authors: Coats K. H. , Modine A. D.
Published: December 2007

In the past few years there has been increased interest in modeling miscible and thermal recovery processes by the use of reservoir simulation models. The prediction of sharp saturation or temperature fronts resulting from these processes has shown that these simulators can in many cases be very sensitive to grid orientation. One method for minimizing the effect of grid sensitivity is to describe the difference equations with a nine-point rather than the standard five-point finite difference approximations. Inherent in the use of the nine-point approximations is the necessity for calculating consistent transmissibility coefficients. Previously published methods for calculating these coefficients do not have general applicability to heterogeneous reservoirs and/or various irregular grid spacings. This paper presents a method for calculating nine-point transmissibilities for a general heterogeneous system with unequal grid spacing.
Using Local Grid Refinement in a Multiple-Application Reservoir Simulator
Authors: Heinemann Z. E. , Gerken Günter , von Hantelmann George
Published: December 2007

This paper describes the application of dynamic local grid refinement in a multiple application reservoir simulator. Using this procedure generally enables a significant reduction of the total number of blocks necessary for a good reservoir description.

This procedure is combined with a number of EOR-options, automatic selection, variable in time of the implicitly computed variables, an ordering scheme for the equations devised specifically for the characteristics of local grid refinement, and several procedures for the solution of the system of equations. Together these features create a tool which is capable of providing quick and economic solutions to the problems encountered in reservoir simulation.
Nested Factorization
Authors: Appleyard J. R. , Cheshire I. M.
Published: December 2007

A new iterative technique for the solution of the linear equations arising in finite difference reservoir simulations is described. The method comprises a novel preconditioning for the Conjugate Gradient and Orthomin iteration procedures. Nested Factorization differs from the more commonly used incomplete Cholesky factorizations in that it does not form the preconditioning matrix from strictly upper and lower factors. Instead, it constructs block lower and upper factors using a procedure which adds one dimension at a time to the preconditioning matrix. The factorization procedure conserves material exactly for each phase at each linear iteration, and accomodates non-neighbour connections (arising from the treatment of faults, completing the circle in 3D coning studies, numerical aquifers, dual porosity/permeability systems etc.) in a natural way. A number of versions of the Nested Factorization algorithm are compared with other published methods for a series of 2D and 3D problems. It is found that the Nested Factorization algorithms are all roughly comparable and that all compare very favourably with other published methods in terms both of computing speed and storage requirements.
Results of Pressure Transient Well Testing in Appalachian Gas Reservoirs
Authors: Kimmel S. L. , Fulton P. F.
Published: December 2007

Pressure transient tests in hydraulically fractured low permeability natural gas wells require special analytical techniques. Linear flow must be identified before formation permeability can be determined. Proper test design based upon demonstrated well behavior can reduce testing costs and improve confidence in the results obtained. The analytical methods are described. Results from twenty-six pressure transient tests are presented.
Foamed Sand Provides Improved Stimulation Results from Devonian Shale
Authors: Strang D. L. , Norton J. L.
Published: December 2007

Generally, water saturations in the Devonian Shale are low. Production records indicate minimal, if any, water in the areas producing gas or gas and oil. This low water saturation appears to be the key to stimulating the shale, especially in the oil-producing areas.

The introduction of water in the stimulation fluid appears to reduce the permeability to oil, which is reflected in poorer production. The relative permeability reduction seems to be more of a problem than particle migration or clay swelling and could explain the good initial results from straight nitrogen treatments. However, the lack of a proppant, even with low closure stress, leads to very rapid declines.

Water-base stimulation fluids appear to increase water saturation in the Devonian Shale. Use of 90+ quality foam with sand should provide a method of minimizing saturation changes while creating a propped fracture. Initial results indicate this technique provides better sustained production increases in the Devonian Shale.

This paper defines areas of production, describes the geology and presents physical data of the Devonian Shale. It also compares results of several types of treatments that have been used in the Devonian Shale. These results indicate 90+ quality foam with sand should provide an improved stimulation technique for this formation.
Enhanced Load Water Recovery Technique Improves Stimulation Results in the Appalachian Area
Authors: Penny G. S. , Thomas B. D. , Soliman M. Y.
Published: December 2007

The roles of capillary pressure, wettability and relative permeability in controlling load water recovery following hydraulic fracturing treatments have been examined. It has been found in laboratory studies that the judicious alteration of wettability to control capillary pressure and/or relative permeability can promote a rapid thorough cleanup of injected water. Field applications of these concepts in Appalachia have resulted in enhanced load water recoveries and higher production.
A Case Study of Ultralightweight Cementing Practices in the Northeastern United States
Authors: Edmondson T. D. , Benge O. G.
Published: December 2007

Wells in the northeastern United States are generally drilled to a depth of from 3,000 to 6,000 ft. They are usually air drilled through several incompetent formations among which are the Marcellus and Coffee shales. Completions in this area are hampered by very low fracture gradients of 0.4 to 0.6 psi/ft, with most of the formations containing a large number of natural fractures. During cementing, pressures in excess of 1,100-psi hydrostatic can result in breakdown of the formation leading to incomplete fill up on the cement job.

This paper will discuss the existing completion practices in this area, which include the use of multistage cementing, and the incorporation of cementing baskets and other downhole tools. The current cement systems in use and the problems encountered in using them will also be discussed.

Several case histories of new cementing techniques, using ultralightweight foam-cementing systems, will be presented along with the job design used on these wells.

Bond logging of the foam-cemented wells creates an array of special problems for the logging companies, due to the ultra-low densities and the high porosities of these special cementing systems. Newly developed techniques for logging these wells will be discussed, along with the bond logs from the case histories.
Iron Control in the Appalachian Basin
Authors: Dill W. R. , Fredette George
Published: December 2007

The Appalachian Basin presents one of the most challenging production and stimulation problems because of the iron content of its hydrocarbon producing formations.

A variety of iron compounds in the producing formations present problems that have to be considered to effectively stimulate these formations. These iron compounds present three major problems: Relatively insoluble iron compounds that may be released by acidizing fluids and have a plugging effect when they migrate;Acid soluble iron compounds that may reprecipitate when the acid spends; andAerated fracturing fluids being incompatible with formation waters that contain ferrous iron.

A research program was initiated in the later part of 1980 to determine methods of more effectively controlling the iron problems in the Appalachian Basin. Results of this study provide data for comparing the effectiveness of various iron control systems that are used in acid stimulation or breakdown techniques that minimize the release of acid insoluble solids and stabilizes them to decrease the detrimental effect caused by fines migration. Also developed in this study was an iron control system that helps the compatibility of the treating fluid with ferrous iron in the formation water.

Flow test data and field results indicate the effectiveness of these iron control systems and treating techniques.
Early Production from Some Devonian Shale Gas Wells Stimulated with Several Kinds of Explosive Charge
Authors: Coursen D. L.
Published: December 2007

Early cumulative production from Devonian Shale gas wells stimulated with a high energy water gel explosive averaged 2 times that from nearby wells stimulated with dynamite. From an estimate of production loss due to well damage done by post-shot drilling in the shot zone, it is concluded that production from the wells stimulated with water gel would have averaged 5 times that from dynamite stimulations if no such drilling had been done.
A Dynamic Systems Analysis of the "Rocket-Type" Launching of a Well-Casing Tubing String
Authors: McLauchlan R. A.
Published: December 2007

A dynamic systems analysis has been made of the problem of the "rocket-type" launching of a well-casing, tubing string from a well at a hole depth of 3300 ft. The objective of this analysis has been to assess whether the observed "rocket-type" launching (15+ feet into the air) of the tubing string could have been caused by nozzle-breakthrough or tubing failure at the SRC No. 1 in Eddy County, New Mexico. The analysis considers tubing weight, fluid buoyancy, external fluid drag and fluid thrust forces on the tubing string. The tubing string and the fluid columns in the moving string and the annular region external to the tubing string are considered as a coupled dynamic system. Here the condition for motion of the tubing string is included using a one-sided inequality constraint for the resultant force on it. The dynamic system analysis has been implemented in a FORTRAN IV analytical/computer program called TUBERKET. TUBERKET allows the calculation and plotting of the four system state variables—distance traveled by and velocity of the tubing string, liquid heights in tubing string and in the annular region exterior to the tubing string (xT,vT,hT,hA, respectively)—as functions of time. Several situations of interest are considered relevant the dynamic behavior of and hence implied failure mode for the tubing string. Summary plots show typical dynamic behavior as a function of internal shut-in pressure and tubing nozzle diameter. These results indicate that for a specified shut-in pressure of 1200 psig, failure occurred in the tubing per se (at a depth of 1500 to 3300 ft) as opposed to breakthrough at the bottom nozzle opening in order to provide the "rocket-type" launching behavior of the tubing string which was observed.
A Multilog-Evaluation Package using Linear Programming Techniques to Evaluate Porosity and Lithology in Hydrocarbon Bearing Complex Lithologies
Authors: van Ditzhuijzen P. J. D. , Masson D.
Published: December 2007

A multilog-evaluation package using linear programming techniques has been developed to evaluate porosity and lithology in hydrocarbon bearing, complex lithologies. Conventional log evaluation techniques, using crossplots or iterative analytical solutions derived from two porosity logs, tend to give unsatisfactory results in hydrocarbon bearing, complex lithologies.

Linear log-response equations can be defined for several logs including the neutron and sonic logs, lithodensity log, (micro-) resistivity log and natural gamma ray spectroscopy log. By introducing an error term in the log-response equations, the linear programming technique calculates porosity, hydrocarbon saturation in the invaded zone and mineral fractions. This is accomplished by minimizing the sum of the error terms. The linear programming technique has no limitations for the number of logs used and the number of variables calculated. However, if the number of variables is significantly greater than the number of logs used, the solution calculated may not be unique and the results must be treated with caution.

The method has been successfully applied to evaluate porosity and lithology in the Central Luconia gasbearing carbonates offshore Sarawak, East Malaysia. These carbonates consist of limestones and dolomites with porosities ranging from 0 to 40 percent. The porosity and mineral fractions calculated agree very closely with core data and sidewall sample information.
Distributed Control Systems for Offshore Applications
Authors: Williams W. J. , Lyle D. K.
Published: December 2007

Outside of the present economic situation with worldwide petroleum consumption, it is realistic to state one fundamental objective of the oil exploration and production business:

"Continue development of offshore production facilities in key reserve areas for the long-range worldwide demand for petroleum related products."

From the United States perspective, this goal is substantiated by the estimate that 50% of all U S oil company investments will be in the South East Asia region, with emphasis on offshore opportunities.
Geological Studies as a Risk-Reducing Factor in Exploration Ventures
Authors: Wiroyudo Gatot K.
Published: December 2007

During 1981 and 1982, 473 new exploration wells had been drilled and 10 thousand kilometers of seismic lines had been recorded in the Indonesian Basins. New geologic syntheses were put forward. Some of them have led to a number of new discoveries. These activities were backed-up during the last 15 years by capital support with cumulative expenditures amounting close to half a billion US dollars. Despite that, more investments will still be required for further development, and more and bigger future exploration costs will have to be spent. Such massive capital investments apparently need careful handling from both the host country and the investors, in the face of current economic situation and especially in the face of geological risks involved. It is therefore desirable, that decisions involving future investments could be eased as much as possible from the risks they have to carry.

Being a host country, Indonesia accommodates external financial support, and intends to maintain a healthy investment "climate" appropriate for foreign investments. During the last 15 years of its life, the Indonesian petroleum industry offers various incentives, intended to meet investment demands for less and less risk on returns. Yet another new risk-reducing device is still being introduced, mainly to deal with geological uncertainties inherent with exploration decisions.

The approach has been designed to encourage a wide range of possibilities, from limited studies of generai ievei pertaining to geology, economicss and engineering up to in-depth study of specialized nature such as petroleum geochemistry, source rock study, etc.

Since decision common to exploration ventures implies basinal geology, such study could be extended into a joint study on basinal level. These joint efforts thus visualized may be appropriate in reducing investment risks in the basin, and therefore could also be regarded as an investment incentive.
Facilities Planning for the Semangkok Field – Offshore Peninsular Malaysia
Authors: Wan C C , Soong J L
Published: December 2007

This paper deals with facilities planning for Esso Production Malaysia Inc's (EPMI's) Semangkok oil field and is supplementary to the Semangkok Field Development Planning paper presented at this conference. The original plan was to develop the field with three platforms but further studies indicated that two platforms would reach all reserves utilizing higher angle wells. The production facilities include a manned central processing platform, Semangkok A, with gas re-injection facilities and an unmanned satellite platform, Semangkok B. Remote operation of the unmanned satellite platform is accomplished by a telemetry system operated from the central platform. Crude production is pumped to the onshore Trengganu Crude Oil Terminal (TCOT) via a pumping platform. Development planning had to consider the high CO2 content of Semangkok gas which required careful selection of materials in the facilities design.