bluuebunny/crossref_metadata_2025 huggingface dataset:
An Advanced System for the Early Detection of Sticking Pipe
Authors: Jardine S. I. , McCann D. P. , Barber S. S.
Published: December 2007

Today when drill pipe, drill collars and MWD units become stuck in the hole it can result in significant loss of time and money. To reduce stuck pipe requires early indication of the problem and the relevant information to be made available to the drilling team. Sticking events may be the result of several contributory factors which can produce symptoms detectable before the event. This paper describes a system for realtime monitoring of wellbore friction using surface measurements logged by a computer system in order to give advanced warning of changing borehole conditions before they result in stuck pipe.

The basis of the friction monitoring system is a method of recording representative values of hookload and torque to produce depth indexed "profiles" of expected values for a particular well. The profiles form a template which serves to indicate when measurements exceed expected values and conditions are worsening. A "Smart Alarm" has been developed to detect these differences and to trigger a warning directly to the driller. Automatic processing of hookload and torque measurements while drilling identifies anomalies which may be indicative of sticking problems. The system provides realtime displays to all key rig personnel and an offline workstation which can be used to investigate the problem in detail.
Why Compressive Loads on Drill Bits Produce Tensile Splitting in Rock
Authors: Paul B. , Gangal M.D.
Published: December 2007

Conventional methods of drilling with rotary and percussive bits utilize a wedge-shaped tooth form which places a compressive line load on the rock. According to the classical theory of elasticity, the stresses caused by a compressive line loading at the surface are everywhere compressive within the interior of the rock. Paradoxically, it has been observed in the laboratory that the rock directly under the point of the bit undergoes a splitting type of failure which strongly suggests the presence of reasonably large tension stress in the rock, notwithstanding the prediction of the classical theory.

It is shown that the classical solution, for stresses under a line load does not reproduce the true condition underneath a rock bit, and a more realistic boundary condition is proposed. Having formulated a more realistic boundary condition one is still faced with the very difficult mathematical problem of solving the field equations of problem of solving the field equations of the theory of elasticity to find the state of stress in the rock. In this paper, we apply a recently developed paper, we apply a recently developed digital computer program which clearly shows the presence of tensile stresses, directly under the bit, which are of such a nature and such a magnitude as to explain the "splitting action" observed in practice.

Introduction

Rock drill bits are essentially wedges, or indentors of various shapes, which load the rock over a small surface area in order to produce high contact stresses. It is therefore perhaps natural to analyze the situation by treating the applied load as a line loading (for a wedge bit) or concentrated load (e.g. for a button-bit) in an effort to estimate the stress field in the rock. This approach is all the more attractive because the stress and strain fields in a semi-infinite elastic body, subjected to a line load, as shown in Fig. 1-a, have been found by Flamant to be given by the simple expressions:

..............(1)
Field Experiences with an Environmentally Acceptable Rotary-Shouldered Thread Compound
Authors: Stringfellow W. D. , Jacobs N. L.
Published: December 2007

Environmental regulations are prompting the oil and gas industry to consider replacement of thread compound formulations which have served for more than three decades. Replacement is necessary because these traditional compounds contain significant percentages (up to about 65%) of heavy metal powders. Use of copper, lead and zinc, as well as persistent synthetic materials, such as PTFE, has been restricted by environmentally conscious governments. Replacement presents several problems because of the nature and severity of the application.

This paper summarizes field experiences using a new technology rotary shouldered thread compound. This work includes field tests and drilling experiences in several geographic areas. In addition, it describes practical challenges and economic considerations with an environmentally acceptable compound.

Because new technology is needed soon, this paper provides a brief overview of the application, general performance requirements, and basis for changing to environmentally acceptable compounds.
The IADC Roller Bit Classification System
Authors: McGehee D. Y. , Dahlem J. S. , Gieck J. C. , Kost Bill , Lafuze Dave , Reinsvold C. H. , Steinke S. C.
Published: December 2007

The LADC (International Association of Drilling Contractors) roller bit classification system provides a convenient method for categorizing rock bits according to their design features and intended applications. The system has been used worldwide since 1972. The 1992 version includes improvements which reflect the latest design trends in roller cone bits.

This paper explains the IADC roller bit classification code. Current classification charts are shown for major bit manufacturers. The relationship between the LADC code, bit design factors, and operating guidelines is discussed. Examples depict the major design features included in the code.

Since this version contains only minor changes from the 1987 Roller Bit Classification System,1 these changes will be listed at the beginning of the paper. Those experienced with the code need only read the changes. Subsequent paragraphs present a complete discussion of the classification system for the benefit of the readers who may not be familiar with the system or who wish more detail. IADC bit topics also updated in 1992 include Fixed Cutter Classification2 and Dull Bit Grading.3,4
New Horizontal Drilling Techniques Using Coiled Tubing
Authors: Wesson H. R.
Published: December 2007

This paper describes the status of an ongoing project to both prove the feasibility of and provide a testbed for the development of processes and tools for drilling with coiled tubing. To date a total of three horizontal wells have been drilled in the Austin Chalk formation in Texas. These wells consisted of two 4 1/2" (114 mm) reentries in the Pearsall Field and one 5 1/2" (140 mm) reentry in the Austin Chalk near Bryan, Texas. To our knowledge these are the first horizontal wells to be drilled using coiled tubing.

These wells have been drilled using 2" (50.8 mm) coiled tubing with a 0.156" (3.96 mm) nominal wall, downhole mud motors, wireline steering tools and downhole mechanical orienting tools. The coiled tubing had a 5/16" (7.9 mm) single conductor wire installed inside it to allow the use of conventional wireline steering tools. The tools and techniques developed during this project and the advantages, limitations and future potential for this type of drilling operation are the subject of this paper.
Geophysical Methods for Reservoir Characterization
Authors: Zimmerman L. J. , Chen S. T.
Published: December 2007

Petroleum resources are finite and becoming ever more elusive. As known reserves are depleted, efficient management of existing reservoirs is crucial. One valuable tool for reservoir development is computer simulation. Unfortunately, although the technology is available to construct geologically complex computer models of reservoirs, the level of detail which can be included in such models is far beyond the ability of traditional methods for measuring reservoir properties to accurately constrain those models. For example, geostatistical techniques permit a modeler to describe a geologic representation of a generic reservoir which is realistic and empirically matches historical measurements related to reservoir performance. However, the resulting model will not be a true representation of the specific reservoir and consequently predictions based on the model may be suspect. Seismic imaging methods are emerging as promising new measurement tools which can be used to bridge the information gap between wells and help constrain stochastic models. 1

Recent breakthroughs in hardware and software have improved the resolution of seismic methods to the point where they can now address production-scale problems. Parameters and attributes extracted from seismic data can be empirically and analytically related to rock properties of interest for reservoir development. This offers the tremendous potential for improving profitability through efficient development of reservoirs. This paper will illustrate the application of seismic imaging to, characterize reservoir properties. Examples from two geologic settings will be used to compare the resolution of four seismic imaging methods; Surface Seismic Surveying, Reversed Vertical Seismic Profiling (RVSP), Cross well Reflection Imaging, and Crosswell Tomography.
Microbes: The Practical and Environmental Safe Solution to Production Problems, Enhanced Production, and Enhanced Oil Recovery
Authors: Brown F. G.
Published: December 2007

This paper presents the theory and field application of microbial treating oil well systems and reservoirs to control paraffin wax deposition, increase producing rates and enhance oil recoveries. The technology applies to paraffin base crude oils produced from solution gas drive reservoirs. The application of this microbial enhancement technology can increase oil recoveries in all stages of reservoir depletion.
Techniques for Accelerating Production Response in Steam-Foam Recovery
Authors: Mohammadi S. S.
Published: December 2007

Incremental oil production response to steam-foam application can be accelerated by improved surfactant formulations and modification of techniques for foam emplacement. By considering the effect of gravity on surfactant and steam flow, a number of injection strategies for accelerating production response have been developed using a steam-foam simulator. The prototype model used, is an idealization of a section of Midway Sunset Field. Comparisons are made between various steam and foam injection strategies at different formation intervals. The results indicate that by injecting foam high in the structure while injecting steam near the bottom, production response can be accelerated over bottom injection alone. Maximum recovery can be achieved by gradually lowering the foam injection interval while injecting a portion of the foam near the bottom of the structure. Mechanically, these techniques can be implemented by multiple completion methods, simultaneous injection through tubing and annulus, or use of two adjacent wells for steam and steam-foam injection. Although demonstrated results are reservoir specific, the concept can be extended to other types of structures since the underlying principal deals with optimum placement of the surfactant for correcting gravity override.
Case History of Pressure Maintenance by Crestal Gas Injection in the 26R Gravity Drainage Reservoir
Authors: Wei M. H. , Yu J. P. , Moore D. M. , Ezekwe Nnaemeka , Querin M. E. , Williams L. L.
Published: December 2007

This paper is a field case history on the performance of the 26R Reservoir. This is a gravity drainage reservoir under pressure maintenance by crestal gas injection. The 26R Reservoir is a highly layered Stevens turbidite sandstone. The reservoir is located in the Naval Petroleum Reserve No.1 (NPR-1) in Elk Hills, Kern County, California (Figure 1). The 26R Reservoir is contained within the steeply dipping southwestern limb of the 3 1S Anticline. The reservoir had an initial oil column of 1,800 feet. Original oil-in-place (OOIP) was estimated at 424 million barrels.1

Pressure maintenance by crestal gas injection was initiated immediately after production began in October 1976. The total volume of gas injected is about 586 BCF. This exceeds one reservoir pore volume. Reservoir pressure has declined from 3,155 psia to 2,461 psia at 6,000 feet subsea. This pressure decline is believed to be due to migration of injected gas into the overlaying shale reservoirs. Under the gas injection pressure maintenance strategy, reserves are estimated to be approximately 212 million barrels.

Reservoir studies have concluded that the aquifer at the base of the reservoir has been relatively inactive. Well recompletions, deepenings, and horizontal wells are used to improve oil recovery.

An aggressive program of controlling gas production began in the mid 1980's by the installation of multiple packers and sleeves. As the gas-oil contact (GOC) has dropped, sand intervals have subsequently been isolated behind packers. A cased hole logging program was recently undertaken to identify possible remaining reserves in the gas cap.
Thermal Simulation of Elk Hills Light-Oil Steamflood Pilot
Authors: Burzlaff A. A. , Harris B. R.
Published: December 2007

A light oil steamflood pilot project was conducted from 1987 to 1991 in the Shallow Oil Zone of the Elk Hills field. A thermal simulator, employing a distillable component and a non-distillable component, was used to construct a steamflood model and duplicate over three years of pilot performance. In addition, a conventional black oil model was used to duplicate pre-pilot primary production performance and quantify the distribution of oil, water and gas saturations prior to the start of steam injection. Uneven thermal energy distribution and limited steam zone temperatures minimized the effectiveness of the steam distillation recovery mechanism.
Imbibition Assisted Two-Phase Flow in Natural Fractures
Authors: Babadagli Tayfun , Ershaghi Iraj
Published: December 2007

For modeling naturally fractured reservoirs (NFR) under active water drive, the multi-phase flow in the fractures and the interporosity flow effects need to be formulated accurately to represent the physics of the countercurrent imbibition.

This paper presents experimental results on two-phase (oil and water) flow through natural fractures under many different configurations. Flow experiments were enhanced with the saturation measurement technique using the CT scan. Important variables in our experiments were the nature of the matrix rock and its wettability characteristics and fracture configuration. A wide range of matrix wettabilities were investigated. Flow rate in the fractures, which plays a significant role in effectiveness of the countercurrent imbibition, was carefully monitored.

Relative permeability measurements for the bulk system were conducted under unsteady state flow conditions. Unlike homogeneous systems with a single set of relative permeability plots, for the fractured systems under study, a series of plots are generated. Composite system relative permeability response, which are referred to as Effective Fracture Relative Permeability (EFRP) curves, are formulated. This formulation is a potential tool for reducing the dual-porosity model to a fracture network model, where the matrix is a sub-system of the fracture network, and the matrix-fracture interaction is represented by the EFRP.
Inflow Performance of Slanted and Horizontal Wells in Solution-Gas Drive Reservoirs
Authors: Kabir C. S.
Published: December 2007

Simple analytic tools are presented to predict a horizontal or slanted well's inflow performance relationship (IPR) producing from a solution-gas drive reservoir. Although a great body of work has been reported for a vertical well's performance during two-phase flow in the reservoir, only a few papers describe the same for a slanted/horizontal well.

Two recent studies developed empirical correlations for horizontal wells along the lines of Vogel, who had correlated flowing bottomhole pressure with flow rate for vertical well-bores by using numerical simulations. This work shows the difficulty of using these new correlations for evaluating the absolute open flow potential (AOFP), thereby limiting their applications in a predictive mode when field data are unavailable.

We also show that once the AOFP or the maximum oil flow rate is properly evaluated, both Vogel and Fetkovich correlations, originally intended for vertical wells, can be used to describe a well's IPR regardless of its orientation. Likewise, methods available for future prediction of a vertical well's IPR are equally applicable for wells having a different orientation. The AOFP can be computed by using any of the productivity index expressions developed for horizontal wells for various outer-boundary conditions. For slanted wells, the Cinco et al. correlation is used to calculate an effective wellbore radius and hence the well's productivity index.

Synthetic examples are used to show the application of the proposed methodology for computing a slanted well's IPR. On the other hand, a field example illustrates the method's applicability in a horizontal well.
Characterization and Removal of Amorphous Aluminosilicate Scales
Authors: Braun Gerald , Boles J. L.
Published: December 2007

Characterization of amorphous aluminosilicates is best accomplished using an integrated approach involving polarized light microscopy, X-ray diffraction, and SEM-EDS analyses. The amorphous scales discussed in this study are from the near wellbore area and consist primarily of SiO2 and Al2O3 with minor Na2O and H2O. Their refractive index ranges from 1.49 to 1.51, and at least one broad X-ray diffraction "hump", ranging from d = 3.1 Å to 3.5 Å is always present. Field results and laboratory studies indicate that effective removal of these deposits generally requires the use of a combination acid treatment. The use of an organic acid preflush (10% acetic) followed by hydrochloric-hydrofluoric (12%-3%) acid has been particularly successful. In addition, metal chelating agents (e.g., nitrilotriacetic and citric acids) should be incorporated in all acid treating systems to prevent aluminum-rich amorphous phases from reprecipitating.
Deep Heavy-Oil Recovery by Steam Injection Using Twin Horizontal Drainholes
Authors: Cooper G. A. , Gondouin Michael , Zeyrek M. S.
Published: December 2007

We propose a novel method for improving the efficiency of recovery of heavy oil. Two horizontal drainholes are made at the bottom of a vertical well so that one may be steamed while the other is in production. Downgoing steam and rising produced fluids are carried in the same vertical casing so that heat from the produced fluids reduces heat losses from the steam. This arrangement requires a downhole valve that will switch steam and produced fluids between the boreholes. We discuss the design of a suitable well and of the valves, and report results of tests to select suitable materials to function in the high temperature downhole environment.
Options Theory: A New Way Forward for Exploration and Engineering Economics?
Authors: Markland J. T.
Published: December 2007

Techniques used in conventional project appraisal are mathematically very simple in comparison to those used in reservoir modelling, and in the geosciences. Clearly it would be possible to value assets in mathematically more sophisticated ways if it were meaningful and worthwhile so to do. The DCF approach in common use has recognised limitations; the inability to select a meaningful discount rate being particularly significant. Financial Theory has advanced enormously over the last few years, along with computational techniques, and methods are beginning to appear which may change the way we do project evaluations in practice.

The starting point for all of this was a paper by Black and Scholes, which asserts that almost all corporate liabilities can be viewed as options of varying degrees of complexity. Although the financial presentation may be unfamiliar to engineers and geoscientists, some of the concepts used will not be. This paper outlines, in plain English, the basis of option pricing theory for assessing the market value of a project. It also attempts to assess the future role of this type of approach in practical Petroleum Exploration and Engineering economics. Reference is made to relevant published Natural Resource literature.
The Anatomy and importance of Project Finance for Oil and Gas Developments
Authors: Whyatt A. S.
Published: December 2007

Project financing can be of great benefit to oil and gas projects because by separately identifying and securing assets and cashflows it can provide large sums not otherwise accessible to whole projects or to individual companies. Project financing is of interest to members of the SPE because it routinely requires the expertise of petroleum engineers and other professionals to vouch for the viability of petroleum projects and the recoverability of reserves. Its essential attraction is that risk analysis and the application of precise professional criteria enable large projects and amounts to be financed, which otherwise might not occur. This is particularly the case when there are a number of participants in a large project, none of which is on its own able to support the finance. The growth in the average size of projects means that an increasing number of projects must be financed in this way or not be able to go forward.
An Integrated Approach to Prediction of Hydrocarbon in Place and Recoverable Reserve With Uncertainty Measures
Authors: Abrahamsen Petter , Egeland Thore , Lia Oddvar , Omre Henning
Published: December 2007

A method for calculating the probability distribution for oil in place and recoverable reserve is presented. A stochastic reservoir model describing spatial variability is specified and conditioned on available observations. A large set of possible reservoirs are generated from the specified model by stochastic simulation. This set of simulated reservoirs displays the uncertainty and variability in the stochastic model and they can be further processed to

– obtain probability distributions for oil in place and recoverable reserve, – compare contributions to the uncertainty, – constructing maps showing the uncertainty, – evaluate reduction in uncertainty when drilling new wells, – study the uncertainty in the lateral extension of the reservoir.

The first part of the paper outlines the stochastic models for the geometry and the petrophysics. The last part shows several examples of results from case-studies. Emphasis is made on graphical presentations of maps and probability distributions.
Automatic Optimization of Well Locations Using a Front Tracking Reservoir Simulator
Authors: Søreide Ingolf , Flach T. A. , Rian D. T.
Published: December 2007

Waterflood projects on land often well spacing for development, e.g. 5-spot pattern with 40-acre spacing. Deep water offshore waterflood projects, in contrast, are limited to far fewer wells, and hence, well density and location are critical design parameters.

Numerical simulators are often used to optimize these parameters, frequently at considerable expense, using manual trial-and-error techniques and three-dimensional (3D) finite difference simulators.

This study applies an automated technique for the optimization of well locations in a North Sea reservoir developed by waterflooding. An optimization routine was combined with a two-dimensional (2D) areal front tracking reservoir simulator. The simulator is characterized by being very CPU efficient, independent of grid orientation, and free of numerical dispersion.

With the objective of maximizing pretax net present value of oil production, the optimizer was used to find the optimal well locations for two injectors and two to three producers. Optimization runs were performed for a seven-well development case and an alternative nine-well development case. Both cases were examined using two different flood directions.

Results from several optimization runs are presented, including the optimal well locations found. In addition, production data are compared for different optimization runs.

The procedure proved to be both CPU and man-time efficient, and is recommended as a screening method prior to using large, more detailed 3D numerical models.
Optimization Techniques Application in Oil Recovery Problems
Authors: Virnovsky G. A.
Published: December 2007

The paper surveys several applications of the optimization algorithms in different problems of oil reservoir development, well testing and gas resource distribution for gas lift wells. For all these cases the optimization technique proved to be beneficial. The results of calculations show, that the optimal solution may give a substantial gain in oil production in the first and third cases. In the second case the optimization formulation of the problem is the only opportunity to solve it.
A Substitute for Test Separators
Authors: Jensen Flemming
Published: December 2007

A concept is described for predicting the mass flow rates of all phases in a production well from pressure and temperature measurements is described. The approach uses rigorous thermodynamic methods for calculation of physical properties. It is shown that a very simple flow model is sufficient to predict the flow rates with a reasonable accuracy.
A New Approach for Modeling Fluid Inertia Effects on Sucker-Rod Pump Performance and Design
Authors: Khodabandeh Ardeshir , Miska Stefan
Published: December 2007

The elastic behavior of the sucker-rod string, in most models, is simulated by a second-order wave equation with a viscous damping factor, which does not consider the inertia effects of the fluid surrounding the rod string. To consider these effects, another system of first-order wave equations must be solved simultaneously with the rod string equation. Solution of the system of partial differential equation becomes even more complicated if the sucker-rod string properties are not uniform. Because tapered and combination rods are often used in the string, a new approach has been developed. This approach can simulate any combination of rods and fluid inertia effects in a relatively simple and effective manner. It applies the Bergeron method, which can be used for pressure and stress propagation in fluids and solids respectively, by using a system of linear algebraic equations instead of the wave equation(s). A simple example problem is solved before applying the approach to a sucker-rod pumping system. The numerical results are compared to the actual measured surface dynamometer cards. Analysis of the numerical results shows that the fluid inertia effects are important for accurate modeling and design of the sucker-rod pumping system.
Light Oil Recovery from Cyclic CO2 Injection: Influence of Drive Gas, CO2 Injection Rate, and Reservoir Dip
Authors: Karim Fatma , Berzins T. V. , Schenewerk P. A. , Bassiouni Z. A. , Wolcott J. M.
Published: December 2007

Laboratory corefloods were performed to investigate the effects of CO2 injection rate, reservoir dip, and the use of a drive gas on the cyclic CO2 stimulation process. Experiments were conducted in 6 foot long Berea sandstone cores using Timbalier Bay, a light oil, under immiscible conditions (500 psig and 78 °F).

Process performance was maximized at moderate injection rates. Oil recovery efficiencies and gas utilization factors were poorer at very high or low injection rates. The inclination of the core and the site of injection substantially influenced oil recovery efficiencies and gas utilization factors. Process performance was favored when CO2 was injected into the lower end of a core tilted at a 45 or 90 degree angle. The use of a horizontal core or injection into the top of a tilted core yielded a poorer response.

The benefits of a nitrogen drive (or chase) gas were evaluated by comparing the results of injecting CO2 followed by nitrogen with injection of CO2 or nitrogen alone. First cycle injection of a certain mass of CO2 followed by nitrogen yielded over twice as much oil as injection of that mass of CO2 alone. In the second injection cycle, the drive gas experiment recovered over three times as much oil as recovered by CO2 alone.
Shallow, High-Gravity Steamflood Economics Improved by New Application of High-Temperature Scale Inhibitor
Authors: Doll T. E. , Tyler M. L. , Dutton R. E.
Published: December 2007

The Shannon Reservoir at the Naval Petroleum Reserve No. 3, Natrona County, Wyoming, has some six years of Thermal Steam EOR history and has been expanded to six patterns with four 50 MMBTU/hr natural gas fired steam generators in operation.

During Pilot Steam Flood operations, scale formation at producing wellbores and tubulars became excessive. One pulling unit was employed full-time to mechanically cleanout tubulars and replace scaled pumps in 21 original Pilot producers. Acid Cleanouts and scale inhibitor squeeze jobs were expensive and short lived.

Due to planned fieldwide expansion of the Steamflood Pilot, the magnitude of costs associated with production side scale treatment would adversely impact project economics. A means to inhibit scale formation insitu from the injection to production wellbore was investigated.

Based on scale inhibitor application in steam generator tubulars in California, a successful chemical formulation was known to be available. Research determined that the product could be injected with the softened generator feed water and remain in the liquid phase of the injected steam. Sufficient residual was expected to be seen at the producing wellbore to prevent scale formation. A new analytical method had recently been developed to allow measurement of the chemical residual in the produced water. The chemical formulation had not been used in this type of application prior to use at NPR-3.

This paper details the successful application of scale inhibitor injected in the steam generator feed water, transported through the reservoir in sufficient concentration to inhibit scale and to provide measurable residual for confirmation. The economic feasibility is shown to be dramatic with long term reduction in pulling costs, elimination of ineffective acid cleanouts and scale squeezes, and minimal chemical cost to maintain residual at producing wellbores.
Delayed Borate Crosslinked Fluids Minimize Pipe Friction Pressure
Authors: Tan H. C. , Wesselowski K. S. , Willingham J. D.
Published: December 2007

Borate-crosslinked fluids have increased in usage for fracturing treatments in recent years because of their low cost and low damage potential to formations. Until recently, most applications have been in shallow wells below 200°F because of high friction pressures and relatively low thermal stability. Recent advances in borate fluid chemistry have resulted in new techniques to minimize pumping pressure through the use of chemically delayed borate crosslinking agent.

Ability to minimize friction pressure with delayed borate crosslinker has reduced treatment cost and extended the application of borate-crosslinked fluids in deeper wells with higher bottomhole temperature (to 300°F). Laboratory and field data have been gathered to investigate the effects of fluid parameters on the friction behavior of the delayed borate-crosslinked fluid.

The laboratory experiments were performed with a recirculation flow loop to simulate field conditions. The field test was performed in a vertical wellbore. Measurements were made with three bottomhole memory gauges installed at various depths.

This paper presents friction pressure correlations derived from laboratory and field data for calculating realtime bottomhole treating pressure on-site to enhance the fracturing treatment analysis. Case histories are used to demonstrate the accuracy in friction pressure prediction for delayed borate-crosslinked fluids using the correlations presented in this paper. A method is also presented for field application of the friction pressure correlations provided in this paper.
High-Rate Refracturing: Optimization and Performance in a CO2 Flood
Authors: Hejl K. A.
Published: December 2007

This paper presents the methodology used to optimize high rate refracturing treatments in a massive sandstone reservoir and associated incremental production response in a carbon dioxide (CO2) flood. Fracturing at high rates (70 to 100 bbl/min) using 10 lb/gal sand concentrations is necessary to fracture 700 ft of gross interval with 250 ft to 300 ft of net pay from six producing horizons.

Optimization of the work process reduced workover costs, fracturing costs, and contamination of the reservoir by fracturing additives and fluids. After the workover procedure was streamlined, fracture fluid additives and volumes for the pad, ramp, and final sand stage were examined.

It was hypothesized that fracturing in the area of the reservoir flooded with CO2 would accelerate CO2 breakthrough problems, causing increased CO2 production. Refracturing has increased the produced processing rate in the CO2 area of the reservoir, with little or no increase in CO2 gas production. Refracturing bypassed near well bore damage caused by barium sulfate scale and asphaltene precipitation associated with the CO2 miscible flood. Incremental oil response attributed with refracturing for the full field and CO2 flooded areas since March 1990 has averaged 52 and 58 BOPD, respectively, on a total of 85 wells.
The Effects of Mechanical Properties and Selection of Completion Interval Upon the Created and Propped Fracture Dimensions in Layered Reservoirs
Authors: Rahim Zillur , Holditch S. A.
Published: December 2007

With the use of well log data and stress tests, reservoirs can be characterized by layers with different values of porosity, permeability, in-situ stress, Young’s modulus, and fracture toughness.1,2 These fluid flow and mechanical properties dictate not only the height, length, and width of a created fracture, but also affect the distribution of proppant in the fracture. Also, the location of the perforated interval in a layered reservoir plays an important role in the overall propped fracture dimensions.

We have developed a finite-difference, hydraulic fracture treatment simulator that computes fracture dimensions in a layered reservoir.3 Each layer can have different mechanical properties. The model allows initiation of the fracture in multiple producing intervals simultaneously. In this paper, we have used this model to illustrate the effects of mechanical properties on fracture dimensions and proppant transport profiles. In reservoirs with multiple producing zones, we have generated examples where the fracture is initiated in one or several intervals simultaneously, so that we can illustrate the effects of perforation placement upon the distribution of proppant within the fracture. These examples illustrate that the location of the perforations can substantially affect the final proppant profile. We have then taken the propped fracture geometry and used a single-phase finite-difference reservoir simulator to show the production increase and long-term production performance for the different scenarios.
A New and Improved Material Balance Equation for Retrograde Gas Condensate Reservoirs - Part I
Authors: Alvarado Gus , Le Blanc J. L. , Farshad F.
Published: December 2007

A new and improved material balance method by which the original dry gas in place and the original condensate in place can be calculated for a retrograde gas condensate reservoir has been formulated.

This new MBE is a result of theoretical research that is validated using experimental data. Ultimate validation of the new MBE can be made with field cases, and after a laboratory Bc procedure is established.

The new MBE requires a modified PVT procedure to determine the condensate formation volume factor, Bc as introduced here. This variable is currently not in use in the industry and hence is not being measured in current PVT lab procedures.

A basic assumption in the new MBE is that no reservoir condensate is produced. Additionally, the new MBE assumes normal pressure, volumetric conditions, and existence of the reservoir at the dew point. Modifications to accommodate water influx and rock and water compressibility were made to the basic equations after validation.
Pressure Compartments in the Powder River Basin
Authors: Iverson W. P. , Martinsen R. S. , Surdam R. C.
Published: December 2007

The Powder River Basin of northeastern Wyoming contains numerous subsurface pressure anomalies, both above and below normal hydrostatic. A study of approximately 5000 drill-stem-tests (DST’s) from the Powder River Basin reveals the geographic distribution of pressure compartments. The abnormally high pressure compartments within the Muddy Sandstone are selected initially for detailed analysis. Over-pressure in the Muddy pressure compartments is approximately 2000 psi over normal hydrostatic. Lithologie units surrounding a pressure compartment are sampled and measured for threshold displacement pressure with Mercury injection techniques. The seals surrounding the pressure compartment are not impermeable rocks; rather, they are capillary seals due to anomalously high displacement pressure in isolated portions of the Muddy Sandstone. These zones of high displacement pressure appear to correlate with unconformities within the Muddy Sandstone. This model of pressure compartmentalization is in marked contrast to Gulf Coast type models where overpressured aquifers are a result of disequilibrium compaction. Rocky Mountain pressure compartments require more effective sealing, as provided by capillarity and low-permeability rocks.
Simulation and Economics of Coalbed Methane Production in the Powder River Basin
Authors: Reid G. W. , Towler B. F. , Harris H. G.
Published: December 2007

Coalbed methane has emerged as a significant resource for natural gas production in the United States, with estimates of gas-in-place of 400 trillion cubic feet. In Wyoming the largest coalbed methane resources occur in the Greater Green River, Powder River, and Wind River Basins. Very little of this gas has been exploited. This paper examines the potential of coalbed methane production in the Powder River basin by history matching early production from five gas wells in the Rawhide Butte field using a commercially available coalbed methane simulator, COALGAS. Sensitivity studies showed the most important parameters for establishing production were permeability, initial desorption pressure and drainage area. Langmuir constants, desorption time, porosity, well-bore diameter and skin were comparatively less important for long term production. An economic analysis showed that, based on current capital and operating costs obtained from industrial companies, the development of coalbed methane in the Powder River Basin may be economic if the gas sales price is greater than approximately $1/Mscf.
Deviation of Horizontal Well Interference Testing From the Exponential Integral Solution
Authors: Malekzadeh Dariush
Published: December 2007

Interference tests provide valuable information about reservoir characteristics such as areal average transmissivity, storativity, and degree of communication between wells. Due to the larger radius of influence and larger contact area of a horizontal well with the formation than its vertical counterpart, the transmissivity and storativity obtained from interference testing of horizontal wells would be much more representative of the formation than the ones obtained from interference testing of vertical wells.

This paper provides the dimensionless pressure drop and dimensionless pressure derivative type curves for interference testing of horizontal wells and the appropriate equations to be used in conjunction with the type curves in order to determine transmissivity and storativity from field data. Solutions were also obtained for interference testing between horizontal and vertical wells. The deviation of this solution from the exponential integral solution is explained. Dimensionless time and dimensionless distance criteria is established for a particular set of dimensionless parameters to explain this deviation. Guidelines are given for interference test design.
Effect of Afterflow on the Analysis of Pressure Buildup Data From Solution-Gas-Drive Reservoirs
Authors: Hatzignatiou D. G.
Published: December 2007

This work investigates the effect of wellbore storage on the analysis of pressure buildup data obtained in a solution-gas-drive reservoir. All results assume radial flow to a single well draining a solution-gas-drive reservoir with the initial reservoir pressure equal to the initial bubble-point pressure. Although connate water is present, the water is immobile and therefore during production only oil and gas flow within the reservoir. Wellbore storage effects are incorporated by specifying a sandface oil flow rate which during shut-in decreases exponentially from a stabilized constant value of the surface oil flow rate at the time of shut-in to zero. Based on a superposition equation new computational equations for computing effective oil and gas permeabilities as pointwise functions of pressure from the measured values of the shut-in wellbore pressure are presented. The computational equations require that the sandface oil flow rate be measured and incorporated into the analysis. By combining the computed effective permeability versus pressure relation with the oil saturation versus pressure results computed from the material balance equation, one can approximately construct the effective oil and gas permeabilities as functions of oil saturation. It is also shown that a semilog plot of shut-in pressure-squared versus Horner time represents a viable method for obtaining estimates of the mechanical skin factor and the effective oil permeability at the final value of shut-in wellbore pressure.
Clay Removal and Cut-Point Curve Analyses of a One-Step Solids Control Equipment
Authors: Malekzadeh Dariush , Hayatdavoudi A. , Ghalambor A. , Okoye C. U.
Published: December 2007

The objective of this paper is to evaluate the performance of a One-Step Solids Control Equipment (OSSCE) based on the actual field data. The material balance technique was used to achieve this objective. The data obtained consisted of density, volume flow rate, solids content, and size distribution of each flow stream of OSSCE. The cost-effectiveness of using OSSCE as compared to mud cleaners was investigated using the actual field data obtained on the same mud run through the two equipment. In addition, the cut point curve for each equipment was obtained.

The results indicated that the cost of using mud cleaner on the mud sample analyzed is about 4.5 times higher than that of using OSSCE. This is due to the fact that the mud cleaner discarded only 1.7 times more low gravity solids than weight material while OSSCE discarded 4 times more low gravity solids than weight material. About 31% of Chlorite that entered OSSCE was discarded by concentric discharge and screen overflow discharge. This high percent by volume of Chlorite discarded is attributed to the high amount of flocculation of Chlorite particles. The lowest percent by volume of clay type discarded belongs to Kaolinite (3%), which is due to the lesser amount of flocculation by this clay type. Finally, the results indicated that the cut point curve will shift to the left as the volume flow rate of screen overflow discharge increases, resulting in sharper separation or lower d50.
Safety and Shutdown Systems for Offshore Facilities
Authors: Heraiba F. A. , Rahman O. A.
Published: December 2007

ZADCO operates three offshore fields which comprise crude oil production facilities and process plants. The facilities present potential hazards in handling flammable hydrocarbon liquids and vapours.

Comprehensive safety philosophy was employed to minimize the associated risks and sophisticated detection, and control systems based on Programmable Controllers were installed.

This paper outlines the approach adopted by ZADCO and describes the installed safety systems. The paper presents the experience gained during the operations and provides recommendations for similar installations.
Health Care in Developing Countries
Authors: Dawson Donald G.
Published: December 2007

Each country presents its own set of challenges when a health care programme is to be developed. It may include malaria in Africa, snakes and insects in Myanmar, rabies or gun shot wounds in the outback of Colombia, sexually transmitted diseases in Thailand, or the health hazards of poor hygiene anywhere. What I wish to do today is to outline the development of a health care programme required in a developing country through the various phases of exploration work, to hopefully the final long awaited production of oil and gas in a sophisticated modem plant.
The Effect Of Low-Water-Loss Additives, Squeeze Pressure, And Formation Permeability On The Dehydration Rate Of A Squeeze Cementing Slurry
Authors: Hook F.E. , Ernst E.A.
Published: December 2007

The Effect of Low-Water-Loss Additives, Squeeze Pressure, and Formation Permeability on the Dehydration Pressure, and Formation Permeability on the Dehydration Rate of a Squeeze Cementing Slurry

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

In an effort to improve the success ratios of squeeze cement jobs, recent studies were made of the effects of fluid-loss control additives, differential pressures, formation permeability, and placement techniques on the performance of squeeze cement slurries. The studies showed that the rate of filter cake build-up is the most important factor to be considered in squeeze cementing. They further showed that this rate is a function of the variables listed and can be calculated by Darcy's equation for flow of liquids through a permeable media. Use of Darcy's equation showed that fluid-loss additives currently in use function by reducing the permeability of the filter cake. This slows down the rate at which filtrate can be forced through the filter cake and controls the dehydration rate of the slurry.

This paper presents data relating the effects of the various factors on the dehydration rate of the slurry, and shows how a knowledge of well conditions and mechanisms of filter cake build up, along with good control over slurry properties can provide an appreciable improvement in the success ratios of squeeze cementing operations.

GENERAL DISCUSSION

Squeeze cementing is a remedial cementing technique which has always been difficult. Since the introduction of low-water-loss additives for cement; however, the success ratio has consistently increased. These additives have made possible many placement techniques which previously would have been impossible. An understanding of the factors which influence water loss and filter cake formation is a great aid in the selection of the optimum slurry properties and placement techniques.

In order to attain a successful squeeze job, it is necessary to properly place the cement slurry. The slurry consists of finely divided particles mixed with enough water to contact all of the particles. As the slurry is forced against a permeable formation, particles will be filtered out on the face of the formation to form a filter cake. In most squeeze jobs, it is desirable to form this filter cake—but it is necessary to control its growth rate.
Drilling Manpower Planning: Using a Systems Dynamics Approach
Authors: Brett J. F. , McCuish J. D. , Oates K. W.
Published: December 2007

This paper summarizes the results of a study testing the idea that "System Dynamics" techniques can be applied to gauging the effects of manpower application on drilling performance. The techniques discussed here are traditional engineering modelling techniques that have lately been applied to management2,3,4,5 and petroleum problems,1 and hold promise of broad applicability in drilling management. The specific problem of manpower planning was chosen as a test case for other drilling applications.

The concept behind these techniques is to quantify the behavior of the system describing the specific problem at hand. In this way, the consequences of assumptions about a process are explicitly tested. The manpower planning model described here is the result of an iterative process, whereby the model's basic form and predictions were compared with actual results. The scope, purpose, and benefits are described on the following pages. The study showed that System Dynamics techniques are useful tools for planning drilling manpower requirements.