bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Sensitivity Study on the Geological Factors Influencing the Oil Recovery from the Monterey Formation
Authors: Ucok H. 
Published: December 2007

ABSTRACT
To gain insight into the influence of geologic factors on the oil recovery from the Monterey Formation, a 3D slice model was constructed to simulate the Monterey Reservoir using a single-porosity reservoir simulator.
The complex geology of the Monterey Formation, which resulted from nonuniform mineralogic diagenesis, was first simplified by grouping the different lithologies into two categories: Fractured lithologies and unfractured lithologies. This simplification reduced the highly fractured and interbedded Monterey geometry into a thinly layered system with drastically different physical properties which can be easily handled with conventional single-porosity reservoir simulators.
In the modeling, emphasis was given to the understanding of the effects of this highly laminated reservoir geometry, represented by layering of the model, on the primary oil recovery due to solution gas drive, gravity drainage and partial pressure maintenance. The diffusion and imbibition forces were not considered here.
The sensitivity of oil recovery from the Monterey Formation to the ratio of fracture to gross pay and to the permeability contrast between the different lithologies were also investigated.
The sensitivity study indicated that the fracture content of the Monterey formation has a strong influence on the producing life of the fields. The shale matrix contribution to oil recovery remained significant at matrix permeabilities equal or greater than one microdarcy. The gravity drainage substantially increased the oil recovery from the fractured layers. Similarly, partial pressure maintenance by injection of the produced gas also increased the oil recovery from the high conductivity layers. However, this improvement in recovery from fractured layers was more than balanced by the reduction in oil migration from the matrix. Thus, gas reinjection did not improve the overall oil recovery. Actually, partial pressure maintenance reduced the ultimate oil recovery from the Monterey Formation.
A New Method for the Measurement of Gas Relative Permeability and Water Saturation Simultaneously in Low-Permeability Cores
Authors: Narahara G. M. , Holditch S. A. , Moore K. R. 
Published: December 2007

ABSTRACT
Since water is pumped into low permeability formations during stimulation treatments, two-phase rock property measurements are important if one wishes to model the effects of water upon gas recovery. Relative permeabilities are necessary to describe the flow of more than one phase in a porous medium.
Conventional steady-state measurements of relative permeabilities have extremely long stabilization times. Several days may be necessary to generate one relative permeability point. The determination of water saturations by gravimetrics may result in significant error due to handling of the core.
The purpose of this study is to present a new method for measuring gas relative permeability and water saturation simultaneously in low permeability cores. This two-phase transient technique incorporates the analytical solution developed in the early portion of this research project. Under conditions where the water is considered immobile and incompressible, the analytical solution can be used to match effective gas permeability and gas porosity simultaneously from the same transient data.
The new method has been verified with numerical simulation and actual measurements on cores. An extensive series of measurements were performed on two Travis Peak cores to measure the gas relative permeability curve, to check reproducibility of the measured values, and to establish the proper testing techniques.
A Flow Model Based on the Structure of Heterogeneous Porous Media
Authors: Narayanan K. , Deans H. A. 
Published: December 2007

Abstract
Laboratory and field experiments on carbonate core samples suggest that heterogeneities present on a centimeter scale control flow distribution. Heterogeneities on this scale are very important to local mass transfer process in this type of rock.
A three-parameter capacitance model called the ‘pore diffusion model’ has been used to simulate the nonideal features observed in carbonate tracer tests in both the laboratory and the field. The results from the lab tests indicate that even though the pore diffusion model can match experimental data very well, the model does not represent all the true mechanisms of mixing which take place in flow through vuggy cores such as those tested.
As a result an entirely different approach was pursued. Direct observations of flow structure were made using a fourth generation X-ray CT (Computed Tomography) scanner. Local concentration fluctuations on the centimeter heterogeneity scale are quite observable with a CT scanner.
Based on physical observations made using CT, a three-dimensional network cell model is proposed for this carbonate core sample. The model is a convection dominated dispersion model, and is based fundamentally on the heterogeneous nature of the rock. Dispersion behavior qualitatively similar to that predicted by the capacitance-dispersion model is shown to be produced by convection alone.
This work confirms that the nature of dispersion in highly heterogeneous porous media, at least on a laboratory scale, is convection-dominated rather than diffusion-dominated. Flow models based on convective mixing are more appropriate to characterize dispersion in laboratory scale systems compared to models that superimpose a diffusional process upon a convective flow field.
Effective Limits of Concentration the Reverse Osmosis Process
Authors: Johnson James S. , McCutchan Joseph W. 
Published: December 2007

1967 SPE Annual Fall Meeting, Houston, October, 1967

Abstract
An experimental program utilizing the Coalinga, California reverse osmosis pilot plant was undertaken to determine the effective maximum degree to which the brine could be concentrated. The effect of precipitate formation on the semipermeable membranes was also determined.
The tests were divided into essentially three phases:
the feed brine was acidified to determine the effect on the system of pH adjustment, with the pH of the feed brine adjusted by acid injection to control alkaline scale formation, the feed flowrate was lowered until scale formed in the system, and step two was repeated using reduced flowrate without pH adjustment.
The preliminary brine acidification resulted in a 53% increase in the flux of the 112 tubular membranes already in use in the plant while the flux of the new membranes which had just been installed was not effected. Simultaneously, a decrease of 29% - 48% in desalination ratio was observed for all membranes, new and old. These effects were attributed to the removal of particulate matter from the membrane surfaces.
Oil/Water Gravity Drainage Mechanisms in Oil-Wet Fractured Reservoirs
Authors: Hamon G. 
Published: December 2007

ABSTRACT
When oil-wet fractured fields are produced by natural water-drive, the ultimate oil recoveryof the block depends on the final balance between the capillary and gravity forces. Therefore to get reliable performance predictions with dual-porosity simulators, an accurate determination of the capillary pressure curve is needed. Oil-water gravity segregation mechanisms were investigated, by performing wettability tests, waterfloods and long-term gravity segregation experiments on field samples with live fluids.
Experimental and numerical results indicate that the oil recovery by water gravity drainage can be significant (depending on the matrix permeability). However when assuming no capillary continuity between blocks in a moderately fractured reservoir, the numerical predictionof the gravity segregation efficiency is very sensitive to the capillary pressure input inthe very low pressure range (less than -0.5 psia). An alternative method is proposed to accurately determine in reservoir conditions the crude oil-brine capillary pressure curve. It consists of matching by numerical simulation the transient production and differential pressure of an ultra-low rate waterflood, followed by floods at increasing rates. The reliability of this approach has been checked by simulating correctly some laboratory gravity drainage experiments.
The Use of Bottomhole Temperature Variations in Production Testings
Authors: Jones C. 
Published: December 2007

ABSTRACT
Temperature data recorded during production testing have been interpreted and the results found to be a useful source of information to supplement the pressure data. Increases in bottom hole temperature while flowing are explained by the Joule-Thomson inversion effect. During shut-in periods, the temperature declines and it has been found that the fall-off can be analysed using transient well test analysis techniques. Three field examples are presented where effects attributed to reservoir geometry yielded similar responses on both the pressure and the temperature analyses. A fourth example demonstrates how the analysis wrongly interpreted variations in temperature for no-flow boundaries. This paper shows how the variations in temperature during the shut-in behaves in a similar manner to the transient pressure behaviour in a wellbore. A procedure for estimating the static reservoir temperature is also recommended.
Improving the Performance of Parallel (and Serial) Reservoir Simulators
Authors: Barua J. , Horne R. N. 
Published: December 2007

Abstract
Parallel computers hold much promise for scientific computation. So a great deal of effort has been devoted to finding ways to parallelize linear equation solvers.
However in fully implicit reservoir simulators the real problem is the solution of non-linear equations. This paper shows how a judicious combination of linear and non-linear solution techniques can lead to the fastest overall simulator. It uses a combination of an approximate iterative solution of the Jacobian and a Quasi-Newton method.
The proposed method makes it possible to use the highly parallelizable Jacobi matrix solution techniques, which are poorly convergent, and still get good serial performance.
Experiments on a parallel computer show that even with a highly parallel method, problem sizes need to be quite large to get good efficiency.
The proposed method can also be used to speed up serial programs by simply using a good serial technique to iteratively solve the linear equations.
Multigrid Methods for Three-Dimensional Petroleum Reservoir Simulation
Authors: Dendy J. E. , McCormick S. F. , Ruge J. W. , Russell T. F. , Schaffer S. 
Published: December 2007

ABSTRACT
The purpose of this paper is to report on a preliminary study of a new multigrid scheme for solving three-dimensional problems of the type that arise from pressure equations in reservoir simulation. The basic idea of this new approach is to use both semi-coarsening and plane relaxation in order to accommodate all types of anisotropies and heterogeneities. The scheme also simplifies and reduces the cost of the setup involved in automatic coarsening of the fine-grid equations.
This paper presents the results of the new approach applied to several known test problems. A comparison of performance and complexity is made with the best solvers now in widespread use in reservoir simulation.
Improved Stability of the IMPES Formulation for Chemical Flooding
Authors: Foulser R. W. S. , Goodyear S. G. 
Published: December 2007

ABSTRACT
IMPES formulations of reservoir simulation equations solve for the pressure implicitly using time lagged mobility functions and subsequently update the concentrations explicitly. The Courant stability criterion for the explicit step is well known; however a new source of instability has been identified in the pressure equation when the mobility terms contain a pressure dependence which is time lagged. This can arise from shear dependent viscosities in polymer flooding or from the capillary number dependence of relative permeabilities in surfactant flooding. A stability criterion is derived for one dimensional problems and demonstration calculations for surfactant flooding are used to illustrate its application. If the criterion is violated stability cannot be restored by reducing the timestep.
Two new formulations of the pressure equation are derived to eliminate the instability and are implemented in one dimension using a modified Newton scheme implicit in the capillary number. One of these formulations uses an improved numerical representation of the capillary number and mobility terms, and is preferred because it reduces numerical dispersion and the solution time in the new pressure solver.
The new methods are generalised to two and three dimensions. This involves the introduction of more terms into the pressure matrix which is now non-symmetric. However to leading order the new representation of capillary number leaves the bandwidth the same as the conventional IMPES method, thus limiting the cost penalty of the improved scheme.
Automation in Drilling
Authors: Bromell R.J. 
Published: December 2007

American Institute of Mining, Metallurgical and Petroleum Engineers, Inc.
This paper was prepared for the 42nd Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Tex., Oct. 1–4, 1967. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.
Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
Application of a "systems concept" to the drilling operation is discussed in this paper. Through the use of hydraulics, electrical systems, electronics and a new approach in basic design, automation of oilwell drilling has been accomplished. The basic functions of the machine are described and methods of control are presented in simplified form.
Automation will permit an increase in the application of engineering to drilling operations through the use of computer control. Downhole variables can be adjusted for optimum drilling rates; safety features can be incorporated in the controls to minimize downhole hazards while tripping; and vast amounts of data can be accumulated since all machine functions are continually monitored electrically.
Rig safety should be greatly improved due to the remote operating position of the crew.
It is concluded, that through automation, economics of oilwell drilling will improve due to lower moving costs, improved safety, increased efficiency and better working conditions which will upgrade personnel.

Introduction
Any repetitive operation, such as the making and breaking of drill string connections when tripping or adding joints of pipe when drilling, lends itself to automation. Economics within the drilling industry have prevented, until now, the development of an automatic machine to perform drilling functions. Domestic land drilling has seen the exodus of most of its qualified personnel to offshore, foreign drilling and more desirable industries with better working conditions. Cheap equipment through cannibalization and auctions, has helped the remaining contractors to stay in business with no earnings from which to modernize. While replenishing their rigs from the vast reservoirs of used equipment they could not correct the economic pressures brought about by reduced demand. These same pressures forced personnel from the industry.
While the land contractors were retrenching, foreign and offshore drilling experienced a record growth.
Implicit Compositional Simulation of Single-Porosity and Dual-Porosity Reservoirs
Authors: Coats K. H. 
Published: December 2007

Abstract
This paper describes an implicit numerical model for compositional simulation of single-porosity and dualporosity oil or gas condensate reservoirs. A 3-component equation-of-state compositional approach is proposed as a desirable alternative to extended black oil modelling, requiring little more computing time than the latter. The approach is illustrated for an actual near-critical volatile oil reservoir. A simple method for reducing implicit formulation time truncation error is described and illustrated. A new bottomhole constraint function is described for better preservation of production well target rates in compositional models. A new matrix-fracture transfer formulation including matrix-fracture diffusion is presented for the dual-porosity description; its accuracy is examined in connection with several test problems where correct results are available from single-porosity simulation. Results are discussed for a 3D 600-block simulation of a highly fractured near-critical volatile oil reservoir.
Natural Fracture Distribution in Reservoirs Modeled by Backstripping and Finite Element Stress Analysis
Authors: Jensen O. K. , Bresling S. , Christensen O. W. , Rasmussen F. O. , Foged N. , Petersen K. 
Published: December 2007

ABSTRACT
A deterministic model is described which enables the stress conditions to be calculated based on the structural growth history. The method provides a framework for estimating natural fracture distribution and directions. The method is developed for two dimensional cross sections and can be extended to three dimensions.
A depth converted seismic profile is used for dividing the geological section into a finite number of time defined formations. The individual formations can be intersected by fault traces. The paleo-appearance of the cross section is constructed through steps in geological time by stripping off formations from the top. In each step the remaining section is decompacted under the decreased load based on the compaction trend of the individual formations. For structural restoration, unfolding and movement along fault traces are made. During this backstripping the displacements are recorded for the subsequent stress analysis.
Stresses are calculated by finite element modelling. An elastic/plastic strain hardening model is proposed. It includes a time dependent creep model making it possible to predict formation properties through geological time. An elastic/plastic finite element model has been designed to calculate stresses by use of these displacements.
The results of the stress analysis are predictions of the stress state being either elastic or plastic: compaction, compressible shear or tension fracture orientations is given too for each point in the reservoir at the steps in geologic time. The level of stress can be "history matched" with well data, well test analysis, fracture identification logs, in situ stress measurements etc..
Illustration of the method is presented for two oil bearing chalk reservoirs overlying salt diapirs in the North Sea. One example illustrates the stress state in a heavily fractured reservoir and the other, a less fractured reservoir.
Estimating In-Situ Permeabilities for Reservoir Simulation Using Multi-Variable Transforms: Two Case Studies
Authors: Carr B. S. , Metcalfe S. L. , Saleri N. G. 
Published: December 2007

ABSTRACT
This paper describes two case studies which illustrate the development and practical application of multi-variable permeability transforms in reservoir simulation studies. The complex lithologies of the two reservoirs under study and the apparent lack of adequate correlations between porosity and permeability necessitated the use of multi-variable transforms. The described methods proved instrumental in the permeability characterization of the reservoirs and in the construction and history-matching of the respective simulation models. In essence, the methods were based on the integration of reservoir information from well logs and cores, subsequently calibrated against well tests.
A Method for Modelling Incomplete Mixing in Compositional Simulation of Unstable Displacements
Authors: Nghiem L. X. , Li Y. -K. , Agarwal R. K. 
Published: December 2007

ABSTRACT
A major deficiency of current compositional simulators is their failure to model the effect of unstable displacements caused by adverse mobility ratios. Since the injected gas is less viscous than the oil, the gas front becomes unstable and numerous fingers develop and penetrate the oil giving rise to poor displacement and sweep efficiency. This shortcoming restricts the application of current compositional simulators, and engineers often opt for a pseudo-miscible black-oil simulator to model unstable gas displacements. This is certainly unfortunate because a pseudo-miscible simulator does not have all the phase-behavior mechanisms of a compositional simulator.
This paper presents a novel approach for modelling unstable displacements in a fully compositional model. The method distinguishes two flow regions in each reservoir gridblock:
a region where complete mixing occurs between the oil in place and the injected gas. a bypassed region where the oil is not contacted by the gas but can still flow because of pressure gradient.
Transfer of components is allowed between the bypassed region and the completely mixed region to simulate the phenomena occurring at the edges of the fingers. The bypassed region shrinks as components are transferred into the mixed region. A two-parameter model is developed to model the transfer rate. Equation-of-state flash calculations are performed in the mixed regions for accurate predictions of phase behavior.
The method is tested against data showing:
Unstable miscible displacement in one dimension. Unstable miscible displacement in two dimensions. Interaction between phase behavior and fingering effect in a near-miscible gas injection process.
Comparisons with a compositional model without fingering effect are also presented.
An Anistropic Coarse-Grid Dispersion Model of Heterogeneity and Viscous Fingering in Five-Spot Miscible Displacement That Matches Experiments and Fine-Grid Simulations
Authors: Ewing R. E. , Russell T. F. , Young L. C. 
Published: December 2007

ABSTRACT
Our objective is improved understanding of how to model the effects of heterogeneity and viscous fingering in adverse-mobility-ratio miscible displacements. We hypothesize that a formulation along the lines of Young, modified to allow for distinct longitudinal and transverse dispersivities, can use coarse-grid dispersion relationships to represent averaged fine-scale behavior. To study this question, we perform numerical simulations in five-spot geometries, using accurate finite-element methods on very fine grids, and attempt to match the resulting recoveries with coarse simulations employing an appropriate anisotropic dispersion term. We also compare the coarse-grid and fine-grid simulations to published experimental data.
It turns out to be very difficult to analyze the effects of the parameters in Young's model, due to statistical uncertainties in oil recovery. Different realizations of the same statistical properties of permeability can yield very different results. This raises many questions that should be studied further.
Despite the uncertainties, some clear conclusions can be drawn from our data. The anisotropic coarse-grid dispersion model can match experiments and averages of fine-grid realizations very well, while the traditional mixing-parameter model of fingering overestimates sweep efficiency and underestimates displacement efficiency when a comparable grid is used. Anisotropy is important, because it reduces recovery and avoids the optimistic predictions often attributed to convective-dispersion models. At the levels of heterogeneity considered in this study, with one standard deviation of a log-normal distribution representing a permeability increment of up to 50 percent, heterogeneity by itself does not influence recovery as much as fingering does.