bluuebunny/crossref_metadata_2025 huggingface dataset:
Ability of Geostatistical Simulations To Reproduce Geology: A Critical Evaluation
Authors: Hand J. L. , Yang Chung-Tien , Chopra A. K. , Moritz A. L.
Published: December 2007

Geostatistical techniques are being used increasingly to model reservoir heterogeneity on multiple scales. Several techniques are now available which differ in their underlying assumptions, complexity and applications. This paper compares the geostatistical sequential gaussian, sequential indicator, and truncated gaussian simulation techniques with the more traditional geological hand mapping description technique and compares their influence on flow simulation performance.

The base geological description was generated using a hand drawn map of the geological facies associations within a 3-D model area in a fluvio-deltaic environment. The average values of porosity and permeability were assigned to the respective facies associations. A second description was generated using sequential gaussian simulation by honoring the porosity and permeability well data, the corresponding vertical variograms, and the inferred lateral variograms. A third description was generated using sequential indicator simulation to distribute porosity and permeability instead of sequential gaussian simulation. Both of these simple geostatistical descriptions were not constrained by explicit geological facies association information. A final more complex geostatistical description was generated in which the underlying geological framework of facies association was first simulated using truncated gaussian simulation and then the porosity and permeability were distributed within each facies association using sequential gaussian simulation. All of the fine scale descriptions were compared in detail and scaled up to large grid blocks appropriate for flow simulation using a pressure solver.

A comparison of the 3-D hand drawn facies association map with the one computed using truncated gaussian simulation showed that the hand drawn map contained less variations than the geostatistical facies association map when conditioned to the same well data. Comparison of the fine scale porosity and permeability maps showed that the distribution of the average values of porosity and permeability in the 3-D hand drawn facies association map failed to reproduce the complex texture of the rocks giving a considerably more uniform distribution of these attributes. It was found that distributing porosity and permeability geostatistically without the influence of explicit facies association information significantly reduced the effective control on the distribution of these attributes, resulting in a more continuous distribution of porosity and permeability than that obtained when facies association information was used. Comparison of the fine scale permeability distributions to those obtained after scaleup showed that the pressure solver maintained the major permeability features apparent in the fine scale distribution which were important to reservoir performance. The influence of these description techniques on reservoir performance was compared using a fluid flow simulator.
Geostatistical Modelling of Heterogeneities in a Mixed Carbonate Platform: The Characterization of Complex Progradational and Retrogradational Mechanisms
Authors: Biver P. Y. A. , Norris R. J. , Vittori J. J-M. , Alabert F. G.
Published: December 2007

In mixed carbonate siliciclastic platforms, deposition is strongly constrained by sea-level fluctuations which induces heterogeneities with complex lateral and vertical sequences. In such sequences, a logical scheme of deposition can be identified over several orders of cyclicity.

Although many geostatistical methods are available, very few are suitable to represent simultaneously the three main characteristics of such environments: the order of deposition, the evolution of facies proportions (lateral and vertical), and the correlation length of the facies. In this paper, we present a methodology well suited to reproduce those features; it is based on probability field simulation, facies are obtained by the truncation of a continuous random variable. The truncation thresholds are determined by indicator kriging.

The technique has been applied in a practical case: a recursive application of such a treatment allows the characterization of lithofacies and petrophysical classes, in consistency with the geological model and with the distributions of petrophysical parameters.

Subsequently, porosity values are assigned using a multiple sequential gaussian simulation which provides the appropriate porosity (ϕ) distribution for each petrophysical class.

Effective permeabilities (K) are then deduced from ϕ-Log(K) correlations which are different from one petrophysical class to another.

Finally, a sub seismic fracturation is roughly taken into account by a deterministic anisotropy factor on permeability. In addition, the main fracture axes are represented, after restoration of the actual geometry, using structural maps containing this information. The obtained reservoirs’ structure is therefore constrained by all the expected geological and petrophysical properties.
Field Results Of Injection Well Stimulation Treatments Using Micellar Dispersions
Authors: Moran J.P. , Maxwell W.N.
Published: December 2007

Use of micellar dispersions to increase water injection capacity of wells has grown rapidly during the past year. Treatments have been performed in many types of formations in nearly all oil-producing areas. The majority of these treatments have proved highly effective and economical. The purpose of this paper is to review the technology of stimulation with micellar dispersions, and compare theoretical results with those actually achieved. This analysis will attempt to show what factors might affect results, and determine where and how this type of treatment can be used most effectively.

Introduction

Injection well stimulation with micellar dispersions was first described by W. B. Gogarty, et al, in 1969. During the past year, this service has been commercially available and different types of formations in many areas have been treated by this process. The results of these treatments process. The results of these treatments (Table 1) indicate that micellar solutions can economically and successfully increase injectivity of water input wells. Analysis of the treatments has provided information which is useful in determining how and where these treatments might be used most effectively.

THEORY

Micellar solutions increase well receptivity to water by removing residual oil from the critical injection area around the wellbore. Removal of this irreducible oil saturation increases the relative permeability to water in the treated area. If all the oil is removed, relative permeability to water becomes equal to absolute permeability or single-phase flow.

Figure 1 is a plot of relative permeability to water and oil versus water permeability to water and oil versus water saturation. This is an actual plot of Bartlesville sand. The solid black lines represent actual plotted values. The dotted lines are extrapolated to show how relative permeabilities would change if varying permeabilities would change if varying percentages of residual oil were removed for percentages of residual oil were removed for the rock. Various formation cleaners and solvent systems are capable of relative permeability changes as indicated by the solid permeability changes as indicated by the solid lines, but only the micellar dispersions so far have been able to effect the changes represented by the dotted lines.

To show effect of the critical matrix on the overall injection rate, a formula can be developed using a cylinder (Fig. 2) where:

rw = well radius

rt = radius of treated matrix
Phase Behavior Impacts of Supercompressible Fluids on Pressure Transient Analyses
Authors: Beliveau Dennis , Fair P. S.
Published: December 2007

Use of the real gas pseudopressure allows most gas well tests to be analyzed using techniques developed for the ideal slightly-compressible fluid problem. However, at near-critical conditions (ie. Tr < 1.1), fluids show dramatic changes in density, viscosity, and isothermal compressibility. The pressure transient behavior of these fluids is not duplicated by the pseudopressure approximation; this requires solution of the nonlinear problem.
Use of Pressure Transient Data To Obtain Geostatistical Parameters for Reservoir Characterization
Authors: Yadavalle S. K. , Roadifer R. D. , Jones J. R. , Yen Nai-Shyong
Published: December 2007

Recent interest1,2,3 in the use of pressure transient data in the area of geostatistical reservoir description has focused on constraining permeability realizations to well test derived average permeabilities or to the measured pressure response. These methods assume an a priori knowledge of the horizontal variogram. Such information is difficult to obtain from the common sources of well data (cores and logs) particularly at the small lag values which can dominate the information in a well test. In this paper we investigate the possibility of deriving an estimate of the horizontal variogram directly from well test data. We also present information on the significance of average permeability values derived from well test information.

Our results indicate that well test average permeabilities, kwt, are not generally a good approximation of the average of the underlying permeability field even if the field is completely random. In the correlated cases, the relationship of the well test derived average and the distribution average is heavily realization dependent. With respect to variograms, we find that our methods produce a reasonable estimate of range and short-lag shape when kwt/kgm for the correlated case compares favorably with the value derived from the uncorrected case with the same level of variability. No estimate of input values of nugget or sill can be derived using the approach presented here.
Real Time Pressure Transient Analysis Methods Applied to Wireline Formation Test Data
Authors: Proett Mark A. , Waid Margaret C. , Kessler Calvin
Published: December 2007

The primary objective of wireline formation testing is to estimate formation pressure and permeability from short duration transient well tests. This paper demonstrates new real time pressure transient analysis methods which may be used during testing to estimate permeability and pressure. These new plots may also be used to determine when sufficient data has been acquired for accurate pressure and permeability determination. Additionally, for tight zones with permeability less than 1 millidarcy, new methods and special plots are presented for interpretation of real time data obtained during the initial drawdown and buildup times. For tight zones the early time data may be distorted by flowline storage effects and is normally ignored by traditional well test analysis techniques. New methods are given in this paper for estimating the compressibility of the actual fluid within the flowlines and chambers of the tester during each test, and this value for compressibility is used in each real time model.

A full 3D finite element near wellbore simulator (NEWS†) that represents an exact solution is used to show that these new plots give the same values of permeability and pressure as would be obtained from very long buildup times using conventional analysis methods. The tight zone analysis substantially reduces the time required to test tight formations and utilizes data obtained within the optimal dynamic range of pressure transducers.
Gas Optimization at the Kuparuk River Field
Authors: Stoisits R. F. , Scherer P. W. , Schmidt S. E.
Published: December 2007

The Kuparuk River Field is located on the North Slope of Alaska, original oil in place was approximately 6.4 billion barrels of oil. Total cumulative production to date is approximately 1.2 billion barrels, and current average daily production is 300,000 barrels of oil. The total number of wells in the field is 750, approximately half of these are producers and half are injectors. A number of enhanced recovery processes including; waterflood, water alternating immiscible gas, and water alternating miscible gas are underway.

Oil, water, and gas are separated at three Central Processing Facilities (CPFs). Production can be routed between the various CPFs to more efficiently utilize facility processing capacity. Gas is compressed at each facility for use in gas lift operations and for miscible and immiscible water alternating gas pressure support projects. Currently the central processing facilities are gas handling limited; therefore, a gas optimization strategy is vital to the efficient operation of the field.

The objective of the optimization strategy is to maximize oil production by; efficient allocation of lift gas to the producing wells, non-gas lifted production well selection, allocation of production to the various CPFs, load balancing between centrifugal and reciprocal compressors. If Kuparuk had no compression limitations then all wells would be on production and all gas lifted wells would be operated at maximum rate. The limited compression capacity requires Kuparuk to optimize formation gas and recycled lift gas in order to optimize field oil production.

A computer program has been developed to facilitate optimization. This program may be run in lift gas allocation and production well selection mode or in system analysis mode. In the lift gas allocation/producer well selection mode, lift gas rates for wells are determined based on the facility incremental gas oil ratio (IGOR), for a given set of facility operating conditions. The formation gas oil ratio (FGOR) cutoff for wells not on gas lift is set at the IGOR. These two criteria provide starting points for the optimization. The program then performs an iterative search technique to converge on the optimum IGOR and FGOR for each CPF. In the system analysis mode, thousands of simulations are run to explore the system response to a variety of operating conditions. Optimal facility operating parameters are determined from the result of the system analysis simulations.

The lift gas allocation/producing well selection processing is done on the field data acquisition system, and the system analysis simulations are implemented via parallel distributed processing on a network of workstations. Surface line hydraulics effects are modeled using nonlinear adaptive models (neural nets) based on rigorous hydraulic simulations. The distributed processing and adaptive models implementation minimizes processing time and cost.
Prediction of Formation Damage Due to Suspended Solids: Modeling Approach of Filter Cake Buildup in Injectors
Authors: Khatib Z. I.
Published: December 2007

Solid particles in injection water build up a filter cake when intercepted on the face of the formation matrix, in the perforations, or even in the gravel pack. The effect of applied pressure, solids type, and oil presence on the porosity and permeability of these thin cakes was determined using a compression–permeability cell. The solids investigated were iron sulfide, iron hydroxide, iron hydroxide/bentonite mixture, calcium carbonate, calcium sulfate, and produced silt and clay. Empirical correlations between permeability and porosity were determined and used to predict injectivity decline rate under reservoir conditions for four common well completions.

A new model for calculating the combined matrix and filter cake resistances in perforations and fractures was developed by using the electrical circuit analog theory.

The results of this study and an earlier study1 were implemented in a user-friendly PC program. This program predicts matrix damage and the injectivity decline rate as a function of solids properties. Consequently, filtration requirements and/or well stimulation schedules can be determined.
Selecting Economic Refracturing Candidates
Authors: Reese J. L. , Britt L. K. , Jones J. R.
Published: December 2007

Since the first fracture treatment was performed in 1947, hydraulic fracturing has been used to accelerate production and improve ultimate recovery in many reservoirs. However, many of the early fracture treatments resulted in wells which underper-formed expectations. Naturally, refracturing has been proposed as a means of improving performance in these wells. Even with improved operational practices, fracturing techniques, and understanding, refracturing has been applied with mixed success.

Our literature survey shows that refracture stimulation treatments in tight formations require increased fracture length and that refracture stimulation treatments conducted in wells in permeable reservoirs require increased fracture conductivity to be commercially successful. Further, refracturing in depleted reservoirs, though responding similarly, may not be commercially viable. We present simulation results and interpret field data which support these conclusions. Our contribution is to evaluate refracturing and provide guidelines to the working engineer with respect to refracture stimulation design and commercial viability.

The paper is broken into three sections. These include a review of previous work, a simulation study of the refracturing process, and a section on the interpretation of field data where refracturing has been applied.
A 100-MMSCFD Portable Gas Lift Compressor
Authors: Thompson V. W. , Palfreyman D. G. , Duhon R. D.
Published: December 2007

This paper discusses the design and installation of two DR-61 Dresser-Rand Gas Turbines powered by LM 2500 gas generators driving tandem centrifugal gas lift compressors on converted jackup rigs. The units are currently in use in Lake Maracaibo, and they are the largest installations of their kind in the world. This discussion emphasizes the engineering and project leadership strategies that allowed the project to be completed within restrictive schedule and budget requirements.
The Effects of Light Ends and High Pressure on Paraffin Formation
Authors: Brown T. S. , Niesen V. G. , Erickson D. D.
Published: December 2007

A thermodynamic model for paraffin formation is presented which accurately accounts for the effects of light ends, such as methane, ethane, and propane, and high pressures. The model uses the Simplified, Perturbed Hard Chain equation of state for all fluid phase fugacities and contains no adjustable parameters for the solid-liquid equilibria. Model predictions are compared to binary solid-liquid, solid-vapor, and solid-liquid-vapor equilibria data with good results. Also, a high-pressure, cold-stage microscope technique was developed to measure cloud points of live oils with which to test the model. Comparisons between the predicted and measured cloud points for live oils are presented.
Study of Perforation Friction Pressure Employing a Large-Scale Fracturing Flow Simulator
Authors: Lord D. L. , Shah S. N. , Rein R. G. , Lawson J. T.
Published: December 2007

Accurately estimating perforation friction pressure is important to the design and analysis of fracturing treatments. Currently, in the absence of a better approach, the industry is using sharp-edged orifice correlations developed with Newtonian fluids such as water. These correlations, however, are probably inaccurate when applied to the rheologically complex fracturing fluids being used today.

A detailed investigation of the effects of fluid type, fluid viscosity, perforation size, and perforation flow rate is conducted with a unique large-scale, high-pressure simulator (HPS). Construction of this simulator was a joint effort involving the Gas Research Institute (GRI), the Department of Energy (DOE), and the University of Oklahoma (OU). Test fluids include water, linear polymer solutions, and crosslinked polymer gels. After fluids are prepared under simulated field mixing conditions, they are pumped into a simulated wellbore through a set of four perforations on a 1-ft spacing into a simulated fracture having variable crack width. Differential pressure transducers are used to monitor pressure drop across the perforations and pressure recovery downstream in various crack widths.

Correlations are developed to describe the perforation pressure-loss behavior. Predictions of these correlations are shown to differ significantly from those made by conventional orifice-type equations. In the new correlations, pressure drop is shown to be dependent on fluid type, viscosity, and perforation size in addition to the conventional dependence on fluid density. These new correlations should significantly improve real-time and post-treatment pressure data analysis.
Film Thickness Distribution for Annular Flow in Directional Wells: Horizontal to Vertical
Authors: Paz R. J. , Shoham Ovadia
Published: December 2007

An experimental and theoretical investigation has been carried out on two-phase annular flow in inclined pipes. The study focused on the effect of the inclination angle on the liquid film thickness distribution. A conductance multi-probe instrument was utilized to measure the local liquid film thickness around half of the pipe periphery for inclination angles of 90°, 75°, 60°, and 45° from the horizontal. A simple analytical model has been developed for the prediction of the liquid film thickness at the top and bottom of the pipe. The model is applicable for the entire range of inclination angles, from horizontal to vertical. Good agreement is observed between the prediction of the model and the experimental data collected in this study and from the literature.
Oriented Perforations - A Rock Mechanics View
Authors: Abass Hazim H. , Meadows David L. , Brumley John L. , Hedayati Saeed , Venditto James J.
Published: December 2007

Hydraulic fracture initiation dictates the communication path between the wellbore and fracture plane. Nonplanar fracture geometries such as multiple, T-Shaped, and reoriented fractures are not advantageous and they adversely affect the potential to achieve a desired stimulation treatment. Oriented perforation can be the solution to initiate a single wide fracture in vertical and deviated wells. Also oriented perforations may be used to create stable tunnels in poorly consolidated formations thus avoiding sand failure and consequently preventing sand production.

This paper presents laboratory experimental results related to oriented perforations for hydraulic fracturing. It also discusses the use of oriented perforation for sand control. Experiments were designed to investigate the effect of perforation orientation in vertical and horizontal wells on hydraulic fracturing treatment.
Overview of Water Saturation Determination For the Ivishak (Sadlerochit) Reservoir, Prudhoe Bay Field
Authors: Holstein E. D. , Warner H. R.
Published: December 2007

This paper is an overview of the water saturation determination processes applied to the Ivishak, sometimes referred to as the Sadlerochit Reservoir, the major producing horizon in the Prudhoe Bay Field. Oil-base-core water saturation (Swobc) values were used to calibrate resistivity-log-derived Sw values. These log Sw values were used, in turn, to tune coefficients for a six-term algorithm (Sw= f(porosity, height)) for use in volumetric calculations of HPV. This overview discusses 1) the technologies used to validate the Swobc values, 2) the areal variations in saturation functions arising from geologic factors, 3) the observed variations in connate water salinity both areally and vertically and 4) the methods used to determine Archie ‘n’ and six-term algorithm coefficients. Other, referenced papers address each these subjects in greater detail.
Delaware Basin Sulfur Development
Authors: Barry Charles B. , Davis Glen R.
Published: December 2007

The Frasch sulfur industry has taken on a new dimension with the development of mineable deposits in West Texas. The sulfur bearing formations in West Texas are generally limestone and similar to those on the Gulf Coast. The West Texas sulfur search is complicated by lost circulation zones and new drilling methods have been developed to cope with these zones. This paper describes the Frasch process and discusses the variables which affect costs and efficiencies. ARCO's Fort Stockton sulfur plant is described and its flow process plant is described and its flow process diagram is presented. The unusual viscosity-temperature relationship of sulfur and its significance in sulfur mining and storage is emphasized.

Introduction

Production of commercial sulfur from gypsum beds such as occur in the Delaware and other West Texas basins will have a significant impact on the sulfur industry. The occurrence of brimstone in gypsum beds throughout the world has been known for years. But it took the recent drilling and development in West Texas to indicate how important such reserves may be. A recent article, by these same authors, presented in the British publication, presented in the British publication, "The Journal of World Sulphur," relates to the Delaware Basin sulfur activity. Gypsum and anhydrite sequences here as well as in other parts of the world contain isolated areas in which elemental sulfur occurs in concentrations up to 50 weight percent. Economic recovery of the percent. Economic recovery of the elemental sulfur from gypsum and anhydrite members is the goal of Frasch mining operations in West Texas. The feasibility of mining these deposits could not be determined until it was shown that mine water could be contained in the ore body, that water supplies were adequate, and that the water could be treated and subsequently heated to the required temperatures economically.

That these requirements could be met was demonstrated by separate pilot operations initiated by Duval and Sinclair early in 1967 near Fort Stockton in Pecos County, Texas. Both operations were later expanded to commercial levels and Duval now also operates a large mine in Culberson County, Texas.
Commercial Polymer Injection in the Courtenay Field, 1994 Update
Authors: Putz A. G. , Bazin Brigitte , Pedron B. M.
Published: December 2007

The polymer injection in the Courtenay field has reached a mature stage as a large part of the polymer slug has been injected. The total production of oil confirms the original expectations and the operation is profitable.

The Courtenay field is an elongated layer at a depth of 600 m. The oil is viscous (40cp), water is fresh and the temperature is 30°C, making the conditions favorable for a polymer injection.

The area swept by polymer encompasses 640 000 m3. It consists of three contiguous zones with a total of 4 injectors and 18 producers. Injection of a 900 ppm solution of polyacrylamide diluted in field water started in July 1989 at a total rate of 380 m3/day. Up to now, 640 000 m3 (100 % pore volume) of solution have been injected, polymer injection was terminated in November 1993; since then, water is injected at a rate of 420 m3/day.

Compared to primary production, a strong increase in oil production has been observed. Definite tertiary oil banks breakthroughs have been observed at 14 producing wells.

The operation has been simulated with the Σcorepol model, a 3 dimensional 3 phases simulator with polymer and tracers option.

The total oil production is well represented on a global basis but the actual quantity of polymer produced in the effluent water is lagging behind the value expected by simulation.

A full physico-chemical characterization of the polymer in the effluents of the well CY55 has confirmed that it was not degraded by its flow through the formation and the injection/production facilities.
Reservoir Characterization and Production Forecasting for Antrim Shale Wells: An Integrated Reservoir Analysis Methodology
Authors: Zuber M. D. , Frantz J. H. , Gatens J. M.
Published: December 2007

This paper presents an integrated reservoir simulation based approach for analyzing production data and forecasting future production for Antrim Shale wells. The practical experience that has been gained through analysis of 40+ projects is presented, including guidelines for estimation of key reservoir properties for use in analysis. Guidelines are presented for conducting Antrim Shale formation evaluation for operators wishing to facilitate accurate reservoir analysis and reserves forecasts.
Pilot Testing of a Radio Frequency Heating System for Enhanced Oil Recovery From Diatomaceous Earth
Authors: Kasevich R. S. , Price S. L. , Faust D. L. , Fontaine M. F.
Published: December 2007

This paper describes a high power, full scale field demonstration of a radio frequency (RF) downhole applicator system which has the objective of ultimately expanding the scope of Texaco’s thermal operations beyond conventional operations. Field testing of KAI Technologies radio frequency heating system was performed in the Texaco Denver Producing Division’s Midway area, N. Midway field, CA, in a shallow diatomite reservoir during the summer of 1992. Two tests (a low power test and a high power test), gave every indication that RF technology is a viable way of heating a formation.
A Fresh Look at Wettability Detergent Flooding an Secondary Recovery Mechanisms
Authors: Kamath Krishna I.S.
Published: December 2007

On the basis of surface energetics of solid-liquid and liquid-liquid interaction, our present concepts of oil-wet reservoirs and present concepts of oil-wet reservoirs and conventional waterfloods are subject to serious limitations. The significant part played by electrolytes in wettability played by electrolytes in wettability alteration floods and by small amounts of impurities in surfactant floods are interpreted as evidence to support the view that electrokinetic and interfacial forces play an important, but not yet clear, role in oil recovery processes.

Introduction

It is well known that by present methods only a third or less of the petroleum originally present in the oil reservoir can be economically recovered. The development of new methods for producing all or part of the oil thus left behind in the ground will not only be a major contribution to conservation, but will also increase our oil reserves at a time when these are being depleted at a rapidly increasing rate. The only means by which this can be achieved is through improvements in our recovery methods with the aid of new technology. The prospects of developing such new technology are good, because much remains yet to be learned about the mechanism of oil recovery and the related area of multiphase flow through porous media. Much of our work in oil recovery porous media. Much of our work in oil recovery research has been empirical, so far, with a fundamental approach to the understanding of multiphase flow through porous media on the basis of surface chemistry principles shows promise of being far more fruitful. A promise of being far more fruitful. A beginning has already been made in this direction with initially encouraging results, but much more remains to be done. This paper proposes to point out some of the apparent inconsistencies in our thinking in some aspects of petroleum recovery research from the viewpoint of petroleum recovery research from the viewpoint of surface chemistry and the necessity of clearing them before progress can be made in this area.

DARCY'S LAW AND MULTIPHASE FLOW

The petroleum engineer is interested mainly in understanding the distribution and flow of oil, water and gas in an oil reservoir and using such knowledge to enhance oil recovery. The presence of more than one phase in a porous medium generates large areas of interfaces in addition to the enormous surface area of the porous medium itself. These solid-fluid and fluid-fluid interfaces are associated with forces which are determined by the chemical nature of the fluids and the porous medium. Though such a system teems with interfacial forces, our present description of the flow process, nearly completely ignores them. In applying Darcy's law to multiphase flow we consider only one rock property, the relative permeability, and only one fluid property, the viscosity. property, the viscosity.
An Improved Viscosity Model for Natural Gases: Application of the Free Volume Concept
Authors: Awuy A. I. , Bretz R. E.
Published: December 2007

A model to predict viscosities of natural gases was developed using the Doolittle free volume equation as a framework. The model was tested against experimental values and in comparison to the three commonly used viscosity models used in petroleum engineering calculations. It was found superior to the other models with respect to deviation from experimental data, ranges of temperature and pressure, and ranges of compositions and components.
Reconstruction of Petrophysical Images Using Cross-Well Traveltime Tomography
Authors: Mendoza-Amuchastegui J. A. , Ramirez-Cruz L. C.
Published: December 2007

In this paper we present the results obtained from a cross-well seismic tomography experiment carried out in an oil producing field of the West Permian Basin, Texas, U.S.A.

Three fundamental stages can be identified from the tomographic method: Field data acquisition, data conditioning, and the actual tomographic process including forward modeling and inversion. For our case, we present a synopsis of each.

The resulting Vp and Vs tomograms show a clear separation of high and low velocity zones that are in agreement with sonic logs. From the final tomograms, we computed images of Vp/Vs ratio, Poisson ratio, porosity and density using well known empirical formulas.

The results attained from the experiment provide an idea of the potential usefulness of the tomographic method as an alternative for in-field exploration and detailed characterization of hydrocarbon producing reservoirs.
On the Petrophysics of Carbonate Reservoirs through Whole Cole Analysis
Authors: Rafael Herrera G. , Fernando Samaniego V. , Francisco Hernández P.
Published: December 2007

This paper presents results of petrophysical whole core analyses carried out in highly permeable dolomite cores, intensively vugular and fractured. The estimated parameters were: multi-directional permeability tests kHθ and kv, matrix ϕmab and fracture porosity ϕfb, the high velocity flow coefficient β, relative permeabilities to oil and water, the effective oil permeability (as a function of effective stress), capillary functions, and the variation of absolute permeability with temperature. The temperature and effective hydrostatic stress used ranged up to 150°C and 20 000 psi, respectively. Several sleeve materials were tested, finding that silicon withstood successfully the test conditions. Stainless steel was used for the flow screens needed for the horizontal permeability measurements. The fluids used in these tests were nitrogen, helium, and brine. As an example of the values estimated for some of these parameters, the ratios for horizontal to vertical permeabilities at an standard effective stress of 400 psi were kh0°/kv = 117, kh90°/kv = 17, and kh0°/kh90° = 6.87. The ratio of matrix to fracture porosities ϕmab/ϕfb = 9.15 and for the compressibilities cfb/cmab = 5.56. Finally, specific values of matrix porosity and multidirectional permeabilities for an increment of the effective stress conditions from 1000 to 8000 psi, resulted in a decrease of 23% for the total 78% for vertical permeability. A new correlation for the high-velocity coefficient is presented for conditions of these highly macrovugular formations, which approximately is parallel 1.6 log cycles above the Firoozabadi and Katz correlation.
Evaluation of Fracture Distribution and Continuity in Carbonate Reservoirs Using Wellbore Imaging Tools
Authors: Roca-Ramisa Luis , Mendoza Jesus , Sanchez-Galindo Miguel Angel
Published: December 2007

Electrical wellbore images had been used extensively in Mexico in order to identify geological features including the distribution and continuity of fractures in carbonate reservoirs.

The main problem associated with the evaluation of fracture continuity has been the fact that sometimes is difficult to distinguish between natural fractures (those present in the rock before drilling) and induced fractures (produced as direct result of drilling), especially when shallow depth of investigation electrical imaging tools are used.

Drilling induced fractures observed in carbonate rocks occur as a result of reduction of stress field around the wellbore and propagate in a direction perpendicular to the unloading direction. In this study, the integration of mechanical properties derived from dipole sonic data and wellbore images has considerably improved the understanding of the induced fracture development.
The Micro TLP Production System for Deepwater Gulf of Mexico
Authors: Zimmer R. A.
Published: December 2007

This paper will describe a production system and associated operating scenarios which allow more cost effective methods of accessing and depleting deep water reservoirs in the Gulf of Mexico. The system is named the "Micro TLP" (Tension Leg Platform) and it has been developed by a multi discipline team. It is based on Conoco's operating experience over the last five years in the deep waters, particularly that gained from the Jolliet TLWP.

The Micro TLP is a very small tension leg platform. It achieves the required performance through load management techniques and past experience from a strong multi discipline design team. Its small size makes it is easier and quicker to fabricate. The Micro TLP is also easily installed, moved and reused in different water depths which facilitates staged or phased production. Staged development with several Micro TLPs instead of a single large TLP will lead to fewer more productive wells being used to deplete the reserves.

In the Gulf of Mexico, deep water may be generally broken into areas near and far from existing infra-structure. This paper will show how a properly designed and operated Micro TLP System may greatly reduce up front capital costs and cash exposure in near infrastructure deep water development scenarios. Further, it will discuss how a Micro TLP may be used in conjunction with a second generation semi-submersible to provide greatly improved economics for a far from infrastructure scenario.
Single-Trip Subsea Completions
Authors: Johnson K. J. , Lorenzatto R. A. , Rittershaussen J. H. , Barreto J. L. , Filho Everaldo Lima
Published: December 2007

Reliability of completion equipment and rig time are becoming more and more critical for subsea completions because of continually increasing water depths in which operators are being required to complete wells. In addition, completion designs must reflect the more stringent economic requirements of today's oil and gas industry. This paper will describe the use of a single-trip completion system that has been successfully and economically installed in the offshore Marimba and Bonito fields of South America. This new completion system has the capability to land the tubing hanger and install it in the wellhead before setting the packer and compensating for subsequent tubing movement.1

The new system also can employ pre-job calculations — based on initial well conditions and anticipated conditions during production — that help determine appropriate completion configurations and bottomhole equipment compatibility. Many failures in offshore wells, whether platform or subsea, can be attributed to inappropriate application of downhole completion tools or methods.2 Use of pre-job calculations during the equipment design stage can facilitate proper selection of design criteria and can help ensure operational safety and cost efficiency.

The development of this new completion system will be discussed in detail. Three case histories that document successful test completions will be reviewed along with the economic gains and advantages that the reduction in rig time generated.
Faulted Reservoirs Characterization by an Image Processing Technique
Authors: Martinez-Angeles Raymundo
Published: December 2007

This paper has developed an image processing method for obtaining the discontinuous areal distribution of oil parameters (formation top, porosity, water saturation,...) of faulted heterogeneous oil reservoirs. For its application it requires the previous knowledge of a set of discret values z(k,l) from well-logs and seismic profiles. Faulted structures were discretized into continuous structures or blocks bounded by faults. The theoretical fundamental assumption of the proposed method establishes that the natural distributions can be considered as the superposition of several elementary brownian distributions, represented by discret values z(k,l), whose physical model is the diffusion differential equation and its solution associated. This is a technique that allows the representation of a composed brownian distribution as a linear combination of all elementary brownian functions. For illustrating the operational aspect of brownian analysis, two examples are studied. The results are presented as a digital images by means of an image processing software.

This method can be applied in mapping, three dimensions interpolation and reserves calculation of faulted reservoirs.
A Simplified Method for Analyzing Naturally Fractured Reservoirs Based in Mathematical Properties of Type Curves
Authors: Alvarado D. A. , Briones M. F.
Published: December 2007

A new simplified method is presented for analyzing wells with wellbore storage and skin in double porosity systems. The method applies to damaged, acidized and fractured wells in fissured reservoirs, and it is based on the mathematical properties of the solutions (Bourdet et al. 's solutions1,2).

By taking the second derivative of the dimensionless pressure solution for a well with wellbore storage and skin in a homogeneous system a locus is defined which contains the maximun of the curve of p/tp/Cp) vs. tD/CD, for each value of the parameter CD exp(2S). The use of the maximun points curve together with the derivative value for radial flow of the total system (fracture and matrix) is used to define a Match Point on the log-log field data graph. This Match Point is also defined on the Type Curve and allows the calculation of C and k, without the neccessity of using the conventional Type Curve Analysis, nor a computer program for pressure transient analysis.

Further properties of the solutions are used to determine S, ω and X, making use of the transition curve minimun (for the pseudo-steady interporosity flow model) and the late transition data (for the interporosity flow model). The simplified analysis presented in the paper is illustrated with actual field examples from several different fissured reservoirs; it is accurate enough for engineering purposes (average relative errors less than 10%) and only requires a few calculations, using the log-log field data graph and a hand held calculator. It can be used as a screening method of analysis. It can also be implemented in more advanced programs of analysis.
Interpretation Model for Fracture Calibration Tests in Naturally Fractured Reservoirs
Authors: Ehlig-Economides C. A. , Fan Y. , Economides M. J.
Published: December 2007

Recent work provided a model for the fracture calibration test in a homogeneous reservoir and an interpretation methodology that enables determination of the formation permeability. The previous study used a rate-dependent skin for the filtercake resistance. Pressure drop in the formation was modeled using a closed form solution for linear flow. The need to analyze tests conducted in naturally fractured reservoirs has motivated the work in this paper.

To model dual-porosity reservoir heterogeneity, the linear flow closed form solution was replaced by an analytical solution. The heterogeneous model uses a standard pressure transient model formulation while incorporating the filtercake resistance from the previous work.

Analysis of data from fracture calibration tests in naturally fractured reservoirs shows that the homogeneous model fails to capture transient behavior attributed to natural fractures. Sensitivity studies using the new model illustrate the pressure falloff response behavior and show what can be determined from the failoff analysis.
Numerical Simulation by the Quadrature and Cubature Methods
Authors: Civan Faruk
Published: December 2007

In this paper, practical quadrature and cubature formulae for numerical differentiation, integration, interpolation, and extrapolation purposes are derived; the method for determination of the quadrature and cubature weights is given, and the procedure for development of finite-analytic quadrature and cubature schemes is presented. It is demonstrated that these methods provide rapid and practical means of obtaining algebraic discretization formulae for numerical approximation.
Application of Multiple Techniques to Determine In-Situ Directions in Marlin and Albacora Fields
Authors: deLima B. B. , Viana R.
Published: December 2007

This paper presents techniques used to determine in-situ stress orientation and magnitude in the Marlin and Albacora offshore fields located in the Campos Basin. These data were collected from anelastic strain recovery (ASR) tests, a low-frequency dipole tool, and a downhole extensometer that provides a new means of analyzing in-situ stress directions and rock properties.

The paper also describes general prejob planning for drilling ship operators performing a microfracturing stress test in deep-water wells. Discussion includes equipment configuration and layout, string configuration, and fluid used to create and propagate the required hydraulic fractures. The possible causes of success or failure for each running session are also discussed.
Improved Recovery Strategies for Heterogeneous Reservoir With High Permeability Contrast
Authors: Surguchev L. M. , Hanssen J. E. , Johannessen H. M. , Abusdal Turid
Published: December 2007

The present paper is a case study of improved oil recovery (IOR) process evaluation for a reservoir in the North Sea that has been particularly diffi-cult to develop by waterflooding — the method of first choice in the area — due to its complex geology and faulting and to the coexistence of regions of very high and very low permeability.

First, a multicriterion analysis based on general IOR experience and the applicability of specific processes in different geophysical conditions was used for a first-order screening of promising IOR technologies. Next, possible development scenarios for a particular stratified formation with high permeability contrast were modelled analytically, using an IOR screening tool developed in-house, and numerically, using a commercial reservoir simulator. Conventional water and gas injection, various horizontal well injection and production scenarios, as well as "traditional" enhanced oil recovery (EOR) methods, such as surfactant and polymer flooding and Water-Alternating-Gas (WAG) injection, all showed limited efficiency for the reservoir in question.

However, the study also showed that novel, in-novative water/gas injection processes and foam-assisted WAG injection, in combination with ho-rizontal production wells, may give considerable improvement of reservoir sweep efficiency. Field model simulations demonstrated high recovery potential of these new processes. The practical applicability in offshore and deep-water completions for these processes were considered with the conclusion that field-scale implementation may be quite feasible.
Numerical Simulation of Fracture Rocks and Wave Propagation by Means of Fractal Theory
Authors: del Valle G. Raul
Published: December 2007

A numerical approach was developed for the dynamic simulation of fracture rocks and wave propagation. Based on some ideas of "percolation theory and fractal growth", a network of particles and springs represent the rock model. To simulate an inhomogeneous medium, the particles and springs have random distributed elastic parameters and are implemented in the dynamic Navier equation. Some of the springs snap with criteria based on the confined stress applied, therefore creating a fractured rock consistent with the physical environment.

The basic purpose of this research was to provide a method to construct a fractured rock with confined stress conditions as well as the wave propagation imposed in the model. Such models provide a better understanding of the behavior of wave propagation in fractured media. The synthetic seismic data obtained henceforth, can be used as a tool to develop methods for characterizing fractured rocks by means of geophysical inference.