bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining Optimal Capacity and Recovery From Gas Reservoirs: Impact of Permeability Contrast, Tubing Size, and Compressor Horsepower
Authors: Dougherty E. L. , Chang Jincai
Published: December 2007

This paper presents optimal solutions, obtained with commercially available software, that provide answers to a selected six important questions encountered by gas developers. The questions are concerned with optimizing; (1) development of a mix of reservoirs, (2) tubing size, (3) spare capacity, (4) intraformation gas migration, (5) dual completions and (6) division of production between compressor stations. The solutions show that economic benefit obtained from determining an optimal solution will usually far outweigh the cost of collecting data, validating a model and making computer runs.
Capillary Pressure Characteristics at Overburden Pressure Using the Centrifuge Method
Authors: Ajufo A. O. , Daneshjou D. H. , Warne J. D.
Published: December 2007

This paper contrasts the results of centrifuge capillary pressure measurements determined at ambient and overburden pressures. The effects of centrifugal forces and overburden pressure on the integrity of well consolidated uniform rock samples are minimal. However, unconsolidated sands, poorly consolidated sandstones, and friable cores are susceptible to deformation and grain re-arrangement, while vuggy cores are susceptible to surface drainage. The severity of these occurrences, which depend on sample lithology and the magnitude of centrifugal forces, can be minimized or avoided by proper jacketing and application of overburden pressure.
Relative Permeability and Capillary Pressure Data From Non-Darcy Flow of Gas/Brine Systems in Laboratory Cores
Authors: Civan Faruk , Evans R. D.
Published: December 2007

Most of the previously reported work for extracting relative permeability and capillary pressure data has been indirect and based on reservoir core history matching which requires iterative numerical solutions of inverse problems until a satisfactory match is obtained. The direct methods are based on integral formulations of the equations describing the fluid pressures and saturations for laboratory cores and they do not require numerical solution methods for differential equations involved in the indirect methods. Therefore, the numerical stability and accuracy and the history matching problems associated with the indirect methods are eliminated.

In the present study, a new direct method for determination of relative permeability and capillary pressure data from unsteady-state non-Darcy fluid displacement in laboratory cores is presented. The new method takes advantage of the internal fluid displacement data that can be obtained by noninvasive techniques in addition to the usual external fluid rate and pressure data. The mathematical interpretation method developed in this study enables the determination of relative permeability and capillary pressure simultaneously without the inherent limitations of the previous methods. It is also computationally more convenient, based on a semi-analytic solution of an algebraic formulation of the flow through porous media. Because it is an algebraic formulation it also provides a numerically more accurate interpretation of laboratory core data. The method is applied with typical gas/brine data to demonstrate its capability.
Identification and Comparison of True Net Fracturing Pressures Generated by Pumping Fluids with Different Rheology into the Same Formations
Authors: Wright T. B. , Aud W. W. , Cipolla C. , Meehan D. N. , Perry K. F. , Cleary M. P.
Published: December 2007

Different hydraulic fracture simulators predict different levels of net pressure, especially with respect to changing/varying fluid viscosity. The level and distribution of net pressure in the fracture must be known to accurately calculate fracture width, which has major implications for the correct calculation of the other fracture dimensions and the location of the proppant. Fracture width also determines the amenability of the formation being fractured toward accepting higher proppant concentrations.

This paper presents various examples of measured data from fracture treatments pumped in a variety of reservoirs, using fluids with widely varying viscosities. The primary aspect of the dataanalysis technique is the evaluation of friction-pressure data obtained from strategically-timed shut-ins and flow-rate changes. Many of the examples are from research environments where more stringent data gathering techniques were used, as opposed to most commercial situations where such procedures are rarely allowed due to (often unjustified) fear of negative impact on treatment effectiveness.

Bottomhole pressure is sometimes seen to change significantly with changing theology. However, shut-ins done immediately after such pressure increases strongly indicate that these increases are due to changing frictional pressure in the perforation-adjacent, near-wellbore region (e.g., due to tortuosity) connecting the wellbore to the fully developed fracture. If this near-wellbore friction is subtracted from measured pressure, the data indicate relative insensitivity of net fracturing pressure to fluid rheology.

The primary implications of these observations are: that commonly-ascribed needs for high viscosity fluids are justified only when near-wellbore problems exist, and that viscosity cannot be used to control fracture geometry (versus proppant placement in the fracture).
Accelerated Fatigue Phenomena in High-Horsepower Turboexpander Wheels
Authors: Russell T. G. , Duncan Colin , Ershaghi Behrooz , Dyason G. J. , Agahi Reza
Published: December 2007

Radial expansion turbines or "turboexpanders" are widely used in the gas industry in both process and power recovery applications. The increasing cost of plant inputs such as power and feedstocks, coupled with abrupt swings in plant throughput as a function of markets and pipeline system linepack, places a premium on tuxboexpander designs capable of operating efficiently and reliably over a broad range of operating conditions.

High horsepower turboexpander wheels which operate over a wide speed band are subject to fatigue failures if the wheel's operating frequency window is too narrow. The fatigue failure mechanism is accelerated by resonance. Appropriate wheel designs, which will deliver extended operating life, may require modified wheel hub profiles and the use of higher strength alloys. Strict control of forging and heat treatments must be maintained to ensure metallurgy of a uniform high quality.

This case study outlines the systematic methods adopted in identifying the cause of turboexpander wheel failures at the Karr Creek Gas Plant, and the engineering design revisions required to eliminate them.
Effect of Orifice Meter Orientation on Wet Gas Flow Measurement Accuracy
Authors: Ting V. C.
Published: December 2007

In many unprocessed natural gas measurement locations between wellheads and process plants, water and condensate are entrained with the gas flow. How measurement at these locations is used for reservoir management, monitoring, control, production allocation, and custody transfer. The accuracy of wet gas metering is of great importance, especially allocation and custody meters, because of the monetary value of the large volume of unprocessed natural gas being transferred daily.

This paper presents the effect of orifice meter orientation, installed in horizontal, upflow, and downflow positions, on the accuracy of flow measurement. Tests were conducted at the Chevron Petroleum Technology Company's Air How Facility in La Habra, California. Two-inch orifice meters with three different orifice/pipe diameter ratios (beta ratios) were selected for testing. Air and water were used as flowing fluid, and they were controlled and measured by sonic nozzles and turbine meter, respectively.

The effects of liquid entrainment on metering error are characterized at each operating position. The results of this study indicated liquid entrainment in orifice meters always contributes lower gas flow rate measurement, up to −2% at vertical upflow position. In order to minimize metering errors in wet gas flow measurement, an orifice meter should be installed in a horizontal position with a mid-range beta ratio.

Currently, there is no acceptable correlation to adjust low liquid entrainment in orifice metering flow. To maintain metering accuracy, the author recommends improving system design to avoid liquid entrainment in orifice meters. In addition, unaccountable liquid condensate accumulation in the meters is a potential loss of revenue.
Dynamic Gas Hydrate Formation and Properties of Diamondoids
Authors: Holder G. D. , Enick R. M. , Jones J. W. , Reiser J. A. , LeBlond C. R.
Published: December 2007

Two solids which can form or deposit in gas transmission lines, gas hydrates and diamondoids, were investigated.

A high pressure apparatus has been designed which enables the rates of hydrate formation from ice to be determined under dynamic gas conditions. The rate of hydrate formation was found to increase with gas flow rate at gas temperatures slightly above the ice point, but this effect was diminished at lower temperatures.

Vapor pressure curves for two diamondoids, adamantane and diamantane, were determined between 25 C and 300 C. Solubilities of these diamondoids were also determined in various organic liquid solvents and dense CO2.

Analytical solutions to the rate of hydrate or diamondoid removal from pipelines containing significant hydrate or diamondoid deposits were also derived.
Improved Performance in Aquifer Gas Storage Fields Through Reservoir Management
Authors: Hower T. L. , Fugate M. W. , Owens R. W.
Published: December 2007

Active water influx into a gas reservoir reduces ultimate recovery from that which would be expected under volumetric conditions due to reduced sweep efficiency and residual gas which is trapped at high pressure. Previous investigations on Gulf Coast gas fields presented in the literature1,2 have demonstrated reservoir management techniques which can increase the expected ultimate recovery over 10% of the original gas in place. This paper presents new work in the form of a detailed case history which extends this emerging technology into aquifer gas storage reservoirs. By their nature, aquifer gas storage fields are water-drive reservoirs. Thus, prudent reservoir management is required to reduce the detrimental effects of trapped gas and poor volumetric sweep.

A detailed reservoir characterization and numerical simulation study are presented for a mid-continent aquifer gas storage field. It is demonstrated that rate optimization during both injection and withdrawal cycles can significantly improve the performance of the storage reservoir. Performance improvements are realized in the form of a larger working volume of gas, a reduced cushion volume of gas, and a decrease in field water production. This research has significant implications for the business facet of the natural gas industry. By utilizing these reservoir management techniques, gas storage operators will be able to minimize their base gas requirements, improve their economics, and determine whether the best use for a particular storage field is base loading or for meeting peak day requirements.
Prediction of Long-Term Deliverability in Tight Formations
Authors: Mattar Louis , Hawkes R. V. , Santo M. S. , Zaoral Karel
Published: December 2007

Those experienced in the natural gas industry know that tests conducted early in the life of a well, in a tight formation, tend to yield optimistic deliverability forecasts. It is not uncommon for producers to report to government agencies, or to purchasers, the results of such deliverability tests, and then to discover, after the well has been placed on production, that rates and pressures have declined continuously to as low as 10-20% of the initial test quantities.

By understanding what controls this transient flow behavior, sometimes called "flush" production, and by collecting appropriate pressure data during the deliverability tests, we can make use of pressure transient analysis to accurately predict the "stabilized" gas rates that the well will eventually achieve.

It is to the producers' advantage to make practical use of current deliverability testing regulations, and to apply the latest state of the art technology to Pressure Transient Analysis. From the pressure buildup data, and the informed use of ADVANCED well test analysis software, one can obtain completion and reservoir characteristics to accurately predict the well's longterm deliverability behavior.

Unlike conventional reservoirs, production from tight formations must be forecast utilizing the "transient flow" equations rather than the "stabilized flow" equations. It is no longer necessary, nor is it acceptable, to use simplistic reservoir models.

Realistic forecasts must take into account the reservoir characterization and model description derived from flow and buildup test analysis. The transient flow forecast in tight formations may control the economics of production, and must therefore be modelled rigorously
Equivalent Drawdown Time for Pressure Buildup Test Analysis for Hydraulically Fractured Wells
Authors: Liao Yizhu , Lee W. J.
Published: December 2007

This paper presents an "equivalent drawdown time" for hydraulically fractured wells. This new equivalent time is derived from a general elliptical flow model. This new equivalent time is helpful in post-fracture pressure buildup test analysis for wells with finite-conductivity fractures including wellbore storage and fracture-face skin. Examples are provided.
Optimizing Matrix Acidizing for Near-Borehole Remediation Using the CIRF Reaction-Transport Simulator
Authors: Chen Yueting , Mu Jun , Chen Wei , Davis D. , Ortoleva P.
Published: December 2007

A new two-dimensional reaction-transport code CIRF (chemical interaction of rock and fluid) is used to design matrix acidizing fluids. Processes accounted for include aqueous phase, mineral and gel reactions, temperature and salinity-corrected activities, texture-dependent Darcy flow, thermal transport, dispersion, effective reacting surface, diffusion limited kinetics and nucleation. CIRF has built-in thermodynamic and kinetic databases, transport parameters, new adaptive gridding and mixed finite element-finite different schemes and user-friendly graphical I/O for complex lithologic geometries.

Examples are shown in which well designed fluids enhance permeability through matrix dissolution; permeability damage is shown to result from formation collapse induced by excessive dissolution or the formation of plugs through precipitation. Effects of injected fluid composition and velocity and initial formation state are illustrated in the case of a shaly sandstone. Flow self-focusing is shown through flow-reaction coupling via texture-dependent permeability to produce dissolution fingering and holes.
Extended Production Testing of the Bearberry Ultra-Sour Gas Resource
Authors: Chernik P. S. , Williams P. J.
Published: December 2007

The Bearberry ultra-sour resource is estimated to be 61-75 Bern (2-3 Tcf) of natural gas with an H2S content In excess of 90%. Hence Bearberry is a potential in place source of approximately 100 million tonnes of sulphur. In 1991/92 this source of sulphur was brought into production (two wells into a nearby processing plant) to assess the viability of long term production of this resource.

At reservoir conditions (37 Mpa, 118 C) the 90%+ H2S gas contains significant dissolved elemental sulphur which precipitates as liquid sulphur (analagous to retrograde condensation) in the formation and the wellbore during production. During the production test, approximately 6 tonnes/day of elemental sulphur were precipitated. Unique equipment and production techniques were required in order to produce the Bearberry gas stream. For example, continuous circulation of sulphur solvent was required to prevent plugging of tubing and flowlines.

From a reservoir engineering perspective, the concern was long term well productivity impairment due to precipitation of elemental liquid sulphur in the reservoir as the reservoir pressure declined. In order to quantify the productivity decline a one meter interval was completed in the 11-35 well. This technique enabled a region of low pressure to be created in the near wellbore area of the reservoir which simulated the long term performance of future commercial wells. Permanent gauges with continuous surface readout were used to measure downhole temperatures/pressures and track performance with time.

This paper describes how the reservoir data was evaluated and the basis for the conclusion that it is technically viable to produce the Bearberry resource.
Development Planning of the Coalbed Methane Gas: A Future Energy Prospect in Java, Indonesia
Authors: Nugroho Wisnu , Mucharam Leksono
Published: December 2007

During 1980-1990. the economic growth of South East Asia countries ranged between 5.5% to 7.9% per year. Along with this development, the energy would be an important element to maintain or increase this growth. In Indonesia, for instant, the growth of energy demand is estimated to be 6% during years of 2000 to 2010. For natural gas demand especially, Indonesia will consume about 1.1 Tcf/year. Java Island, in this case, would become the highest increase of energy demand, from 393 MMcf/D in 1989 to 1200 MMcf/D by 2010. By that time, the natural gas production from both non associated gas and associated gas reservoirs in the Northwest Java basin from where the large amount of gas is produced, is predicted to decline.

In order to overcome this problem, another prospective gas resources that could be exploited is coalbed methane. This kind of prospective gas resource has been found in large reserve in the of Northwest Java basin, epecially in Talang Akar formation, some of the coalbed methane layers found in Talang Akar posses overpressure condition. In this formation, it is found that the vitrine reflectance of coal, ranges from 0.5% to 1.9%. The gas resources from coalbed methane reservoir in Indonesia is estimated about 213 Tcf, and of 33.4 Tcf of this volume is found in Northwest Java basin area. Until this time, these coalbed methane deposit have not yet been developed or exploited commercially.

The economics and the technical aspects of the coalbed methane exploitation and its properties in Talang Akar formation are evaluated and discussed in this paper.
Restimulation Techniques To Improve Fracture Geometry and Overcome Damage
Authors: Schraufnagel R. A. , Spafford S. D. , Conway M. W.
Published: December 2007

This paper discusses remedial hydraulic stimulations used to increase production rates from two coalbed methane wells at GRI's Rock Creek project. The poorly performing stimulation was plugged with cement and the well restimulated using a non-damaging gel, nitrogen foam, and sand stimulation. These treatments suggest: 1) cement can be used to abandon undesirable hydraulic fractures prior to restimulation, 2) the use of an alternative gel polymer, identified by core testing for a specific coal sample, minimized permeability damage during stimulation, and 3) a special foam and sand stimulation created a more effective fracture than the original water and sand treatment in the same well.
Stimulation Technology in the Antrim Shale
Authors: Reeves S. R. , Cox D. O. , Smith M. B. , Schatz J. F. , Schatz John F.
Published: December 2007

The Antrim Shale of the Michigan Basin has been one of the most active natural gas plays in the U.S., with 1992 drilling exceeding 1200 wells. Gas production from the Antrim, reported to contain 76 Tcf (2.1 x 1012m3)of in-place resource, reached 74 Bcf (2.1 x 109m3) in 1992 with 2,600 wells producing at year end. Much of the 1992 drilling activity can be attributed to the expiration of the Section 29 tax credit which was applicable to the Antrim Shale.

The Gas Research Institute has targeted the Antrim Shale as a focus of stimulation research. Two field research projects addressing stimulation technology in the Antrim Shale were initiated during 1992 in cooperation with producing companies, one which is investigating methods to optimize hydraulic fracturing treatments and one which is investigating the potential application of alternative, low-cost stimulation methods.

The first project, being performed in cooperation with Ward Lake Energy, is studying whether single-stage fracture treatments (one treatment for two shale horizons) are more cost-effective than individual treatments for each zone. Four offset study wells were selected for the project; two open-hole completions to evaluate single-stage treatments and two cased-hole completions to evaluate multiple-stage treatments. Pre- and post-stimulation pressure transient testing, mini-fracs, bottomhole treating pressure data, and post-frac borehole camera surveys have been incorporated into the research program. Preliminary results indicate that single-stage fracture treatments do contact both shales, however the stimulation achieved in each zone has not been clearly defined yet.

The second project, being performed in cooperation with Terra Energy, is comparing the costs, stimulation effect and production performance of three offset wells stimulated by (a) an acid bailout treatment, (b) high-energy gas fracturing and (c) hydraulic fracturing. Post-stimulation pressure transient testing, production testing and stimulation diagnostics have been incorporated into the research program. Preliminary results indicate that hydraulic fracturing provides superior production results. The lower costs of the alternative treatments, however, may still make them attractive under certain reservoir conditions.
Gas Migration Velocities During Gas Kicks in Deviated Wells
Authors: Johnson A. B. , Cooper Steven
Published: December 2007

A key factor in the evolution of a gas kick is the rate at which free gas rises up the wellbore. One of the main parameters governing the gas propagation is the wellbore trajectory. A comprehensive model incorporating the effects of deviation and geometry is necessary for an accurate gas kick simulator.

There is no data in the literature which details a comprehensive examination of the effects of deviation and geometry on the gas migration characteristics in a drilling environment. There is a limited amount of data reporting full scale experiments; but these did not characterise the effects separately.

We report tests made in a realistic drilling geometry with Theologically accurate fluids. The tests were in a large pipe and annular geometry with orientations between vertical and 60° deviation.

There is a significant difference between the effect of deviation on gas migration characteristics in pipe and annular flows.

We also address the controversy over gas migration velocities during shut-in. We show how the conventional field derivation of slip velocity from the surface pressure rise rate is inaccurate, and can underestimate the slip velocity by an order of magnitude.
The Application of Slim-Hole Drilling Techniques to High-Pressure and High-Temperature Exploration Programs in the North Sea
Authors: Eide Egil , Hage J. l. , Burge P. M. , Jürgens Rainer
Published: December 2007

Slimhole drilling is a method of lowering well costs by reducing consumables used during the drilling and completion process. The technique has been used to drill high pressure high temperature wells in the North Sea from floating installations.

A three year development program between a major operator and a service company has led to the development of the "retrofit" slimhole drilling concept which allows a slimhole to be drilled using modified conventional equipment from any rig. The problems of well safety and drilling efficiencies have been addressed in the project.

An enhanced kick detection system has been successfully used to detect influxes of less than 1 barrel, and alarm levels as low as 10 gallon/minute influx rate can be used.

The use of high temperature downhole motors and anti-vibration technology ensures that drilling efficiencies and drillstring integrity are maintained during slimhole operations. Well engineered drilling fluids reduce total system pressure losses and improve the hydraulic power available for the bit and downhole tools.

The design of a high pressure high temperature well to T.D. in 5-¾" or 4-⅛" can lead to total cost savings of up to 15 %.
Development and Field Testing of a New Downhole MWD Drillstring Dynamics Sensor
Authors: Zannoni S. A. , Cheatham C. A. , Chen C-K. D. , Golla C. A.
Published: December 2007

The development and field testing of a new three-axis shock and vibration MWD sensor are presented. The sensor is shown to have the capability to detect harmful BHA dynamic conditions such as whirling, lateral BHA shocks, stick-slip, and bit bounce by measuring the changes in acceleration in the axial, tangential, and radial directions. Interpretations of these conditions have improved insight into the drilling process and are expected to result in improved drilling efficiency.
Coiled-Tubing Radials Placed by Water-Jet Drilling: Field Results, Theory, and Practice
Authors: Dickinson Wade , Dykstra Herman , Nordlund Robert , Dickinson Wayne
Published: December 2007

The URRS makes multiple 25 to 150 ft (8 to 46 m) radiais in one or more layers. The range of stable production enhancement with multiple radiais in both light and heavy oil wells in various formations varies from a two times (200%) to as much as a ten times (1,000%) improvement depending on reservoir and wellbore conditions. The average production improvement is two times to four times (200% to 400%). The comparison is made with respect to either (a) the production in a well after radial placement compared to the production prior to radial placement or (b) the production in a new well with radiais compared to similar offset vertical wells.

This paper examines the value of multiple radiais in penetrating skin or near wellbore damage (Figure 1);the calculated magnitude of oil production improvement by penetrating near wellbore damage; andtypical light oil field results involving stable production in a new well with radiais, and a reentered well with radiais.
Design, Construction, and Operation of a Novel Well Control System
Authors: Marschke C. R. , Wu Nanping , Alcocer C. F.
Published: December 2007

This paper presents the development of a revolutionary oil/gas well control system. This system has been created to provide effective control and management of oil/gas wells under diverse abnormal situations. The system is versatile in its capabilities and can be used both offshore and onshore. The system mainly consists of a cutting tool, a specially designed plug/valve, supporting structures and a power system.

This paper describes the prototype of the new system and the results of laboratory tests simulating the actual conditions of operating oil/gas wells. Actual casing and tubing arrangements were used in the laboratory tests. Finite Element Analysis (FEA) and force and stress/strain analysis were performed to design the system and to ensure the integrity of the structure of the well during control operations.
The Success of Synthetic-Based Drilling Fluids Offshore Gulf of Mexico: A Field Comparison to Conventional Systems
Authors: Park Sandy , Cullum Daryl , McLean A. D.
Published: December 2007

The first wells have been successfully completed offshore Gulf of Mexico using a new synthetic-based drilling fluid. Potyalphaolefin (PAO), the synthetic base used for these fluids, is unique to the drilling fluids industry at this time.

The environmental benefits of PAO-based synthetic systems over conventional oil-based fluids and some water-based fluids has already been presented in prior papers. However, the practical benefits gained from utilizing PAO as an alternative to conventional systems can now be documented after a series of highly successful field tests in the Gulf of Mexico.

The non-aqueous PAO system has been used on several wells in the Gulf of Mexico to drill problematic formations previously drilled with either inhibitive water-based or oil-based fluids. Wells with angles up to 86° and formations from 4500 ft to 18300 ft have been successfully drilled.

Direct comparisons can be made regarding performance benefits of PAO-based synthetic systems verses water-based and oil-based systems previously used to drill in the same location. Benefits in hole stability, cuttings integrity, lubrication, and gauge wellbores, all leading to increased penetration rates and subsequent reduction in drilling days, can be seen.

This paper reviews the results of the first field tests with PAO synthetic systems in the Gulf of Mexico concentrating on the practical aspects of drilling rather than the detailed environmental information which has been covered in prior literature.
Engineering Salary Trends in the Petroleum Industry
Authors: Judah J. S.
Published: December 2007

Results of the 1992 SPE member salary survey indicate that salaries are up 3 to 8% compared to salaries reported in October 1991. Results of the 1993 SPE Starting Salary Survey reflect a decrease in starting salaries accepted by B.S. graduates in petroleum engineering to $3,417/month, which is down 2.4% from a year ago.
Achieving Environmental Awareness: A Comprehensive Training and Awareness Program
Authors: Seith B. J. , Green G. J. , Platt J. D. , Purl K. F.
Published: December 2007

Taking a proactive approach to managing environmental affairs offers many benefits including improved regulatory and permitting compliance, reduced operating costs and improved public perception. In an effort to be more proactive and promote environmental awareness, BP Exploration (Alaska) Inc. (BPXA), in conjunction with ERM-Northwest, Inc. (ERM-NW) developed an environmental awareness program, Achieving Environmental Excellence. The program was designed to address the environmental concerns associated with operating an oil field on the North Slope of Alaska. In addition to educating personnel, it has been designed to promote environmental responsibility and stewardship among all BPXA employees and contractors. The program components include seven technical modules on these topics: spills, solid waste management, pollution prevention, the Arctic environment, environmentally responsible lifestyles, a framework for compliance, and a motivational overview of BPXA’s efforts to demonstrate environmental leadership.
The Use of Air Injection To Improve the Double Displacement Processes
Authors: Fassihi M. R. , Gillham T. H.
Published: December 2007

The Double Displacement Process (DDP) has been defined1 as the gas displacement of a water invaded oil column. The purpose of injecting gas into a watered out oil reservoir is to recover more oil by creating a gas cap and thereby allowing gravity drainage of the liquids to occur. During 1994, Amoco Production Company, in partnership with the United States Department of Energy, will initiate the first project to combine air injection with the DDP. Due to the relatively low cost and potential for accelerated recovery, this unique IOR process may prove to be economically viable in low price environment. This report introduces the project by describing: (1) the initial project design, (2) core and fluid property tests, (3) details of the scoping reservoir models, (4) projected production performance and (5) safety considerations.

Modeling of the DDP with air indicated that injection/production rates are predominant factors on the performance of the DDP and need to be optimized. Also, gravity drainage is enhanced due to mobilization of oil by the thermal front. It is shown that the in situ generated flue gas strips the light hydrocarbon components. These appear as natural gas liquids (NGL) in the producing stream. Experimental results indicate that the oxygen in the injected air will spontaneously combust with the residual oil saturation in the reservoir. Compared to nitrogen injection, air injection should yield the same cumulative oil at a lower cost.

The use of air injection with the DDP will be applicable in watered out oil reservoirs which have both: (1) sufficient reservoir temperature to accelerate oxygen consumption, and (2) low oil viscosity in conjunction with sufficient bed dip and permeability for gravity drainage to occur.
Water Disposal From Coalbed Methane Wells in the San Juan Basin
Authors: Cox D. O. , Stevens S. H. , Hill D. G. , McBane R. A.
Published: December 2007

Water produced with coalbed methane in the San Juan Basin presents a costly disposal problem. Production increased from 15,000 bpd in 1988 to 115,000 bpd in 1992, and is projected at 180,000 bpd in 1995. Over the next 20 years, 644 million to 1.04 billion barrels of water production is anticipated. Currently, the main disposal method is underground injection. The rate capacity of existing disposal wells in part of the Colorado portion of the basin will not be sufficient to handle all the water to be disposed of. The volume of produced water during the next ten years will exceed the volumetric capacity of the deep disposal zones there, and other disposal zones or methods will be needed. Alternative treatment technologies are available to treat produced water and make much of it suitable for surface discharge. A smaller volume of concentrated brine remaining after water treatment would still require underground injection or other acceptable disposal methods.
Development and Implementation of an Integrated Risk Assessment Methodology
Authors: Cutten F. B. , Evoy D. F. , Grecu I. M. , Palmer J. H.
Published: December 2007

This paper summarizes a project evaluation methodology developed and implemented by Petro-Canada Resources. The two key objectives of the methodology were to improve the technical quality and consistency of evaluations, and to develop measures that would facilitate risk comparisons among different projects. The paper includes a discussion of the actual methodologies and measures, and the implementation process used in introducing the methodology to the organization.
Determination of Reference Doses for Mineral Spirits, Crude Oil, Diesel Fuel No. 2, and Lubricating Oil
Authors: Ryer-Powder J. E. , Custance S. R. , Sullivan M. J.
Published: December 2007

Petroleum products are involved in the contamination via spills and leaks of many environmental matrices. Unlike sites contaminated with compounds having discreet physicochemical properties, petroleum hydrocarbons represent complex mixtures. Complications involved in evaluating the site and setting clean-up goals include a lack of summarized toxicity data for the petroleum hydrocarbons and the absence of government agency-derived allowable exposure levels. The purpose of this work was to (1) review the toxicity literature pertaining to mineral spirits, crude oil, diesel fuel number 2, and lubricating oil, and (2) determine a reference dose (RfD), defined by the Environmental Protection Agency as a estimate of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime, for each of these petroleum hydrocarbon mixtures.
Experimental and Numerical Studies of Miscible Displacements in Five-Spot Porous Media
Authors: Sorbie K. S. , Zhang H. R. , Tsibuklis N. B.
Published: December 2007

This paper reports new experimental and numerical results on miscible displacements in saturated, homogeneous five-spot bead packed flow models. A series of experimental floods at a range of mobility ratios is presented which generates new data for unstable displacement processes. This data is presented up to 100% recovery and includes: the effluent concentrations and recovery profiles, in situ visualisation of the flow patterns and measurement of the pressure field. A comparable cycle of floods at mobility ratios of approximately M = 4,11, and 25 in a repacked five-spot system showed excellent reproducibility between tests. The volumetric displacement efficiencies compare very well with the published experimental data where this is available. The measurement of the pressure field is particularly novel and this information can be utilised in order to assess averaged (upscaled) models of viscous instability.

A high-accuracy numerical method with third order differencing for convection and second order temporal differencing is proposed which is equivalent to an 11 point interpolation. The simulator treats the full velocity-dependent anisotropic diffusion/dispersion tensor and is validated by comparing numerical results with the analytical solution for incompressible radial flow. The numerical method is further tested by simulating the experimental five-spot stable and unstable displacements. The simulation reproduces the experimental effluent concentrations, recovery performances and pressure drops very well and also matches the main features of the experimental finger evolution.

It is concluded that (1) a complete quantitative experimental dataset, including novel pressure field measurements, has been obtained which can be used to validate theoretical models of viscous fingering in five-spot (almost) homogeneous systems and (2) the proposed mathematical model is capable of accurately simulating the flows characterised by sharp fronts, instability and low levels of physical dispersion.
A Compositional Simulation Evaluation of the Brassey Artex B Pool, British Columbia, Canada
Authors: Rossall J. W. , Gurpinar O. M.
Published: December 2007

A compositional reservoir simulation evaluation1 of the Brassey Artex B Pool, located in British Columbia, Canada, was undertaken to predict hydrocarbon recoveries under a variety of development schemes. The subject reservoir is a thin aeolian sand containing a volatile, highly undersaturated oil. A miscible flood was initiated in 1989 immediately following delineation drilling.

The numerical model was constructed using the most up-to-date geological, geophysical, and petrophysical data. Surface facilities were incorporated into the model, through the use of individual well test separators for production tests performed prior to implementation of a miscible flood, and by a four-stage separator after implementation of the miscible flood. This model was then calibrated by history matching three years of volumetric and compositional data. Tracer survey results were also used in the model calibration phase.

Reservoir fluid compositions were represented in the model with a nine pseudo-component Peng-Robinson equation of state. The equation of state was calibrated to laboratory constant composition expansion, differential liberation, swelling test, and slim tube data to provide representative PVT properties of the reservoir fluid and injected solvent.

The history matched model was then used to forecast the production performance for a variety of production and injection schemes, including infill drilling and sensitivities to injected solvent composition.

The reservoir fluid characterization phase of the study verified that the recovery process was one of first-contact miscibility at the 4000 psia operating pressure. Analysis of the pressure, saturation, and fluid composition distributions demonstrated that an effective first-contact miscible displacement was occurring in the reservoir. While the majority of the pool will be swept with the existing well configuration, two infill drilling locations have been identified. Phase behaviour analysis indicated that the current injection gas is richer than required to achieve first contact miscibility; therefore, liquids can be extracted and sold from the injection gas stream.

History matching of the compositional model suggested an initial oil in place volume approximately one-third less than that derived from previous pseudo-miscible black oil studies. However, the initial analytical material balance estimates derived from production tests conducted prior to the miscible flood showed an oil in place volume midway between the two model estimates. This comparison highlighted the difficulties of characterizing the volumetric behaviour of near-critical fluids using either compositional or black oil techniques.
Natural Gas and the Newly Evolving OPEC
Authors: Ebneyousef M. H. , Bogart A. J.
Published: December 2007

This paper reviews Opec’s current standing, its limitations, the impact of geopolitics, and the organization’s future, particularly its new role as a major supplier of natural gas.

Up to now, many Opec producers have neglected their natural gas sector and failed to develop the required infrastructure and local or regional markets.

For strategic purposes consistent with their political goals, several Opec members upgraded their reserves of oil and natural gas, sometimes without any dependable link between oil and associated gas.
Faster History Matching and Uncertainty in Predicted Production Profiles With Stochastic Modeling
Authors: Tyler K. J. , Svanes Tarald , Omdal Sturle
Published: December 2007

High resolution sequence stratigraphical methods have been used in the detailed geological modeling of an element of the Ness formation of a North Sea field. This updated geological description has been used as input to the stochastic geological model MOHERES. 14 realizations of facies architecture and petrophysical properties have been generated.

The stochastically generated realizations have been scaled up to a refined element of an existing deterministic, history matched reservoir simulation model for the full Upper Brent reservoir. The upscaled versions of the realizations have been connected to the full field model, and reservoir simulations have been performed to compare twelve years of production history with simulated results for well production, RFT- and PLT-data. Six of the realizations gave good to very good results when compared to measured production data. These realizations were used for simulation of the future production performance to the year 2010, making it possible to estimate its uncertainty.
A New Model for Well Testing in Water Injection Wells Under Fracturing Conditions
Authors: Ovens Jonathan , Niko Helmut
Published: December 2007

Water injection under fracturing conditions can sometimes be of significant benefit to a field development, enabling fewer injection wells to be drilled either for recovery processes or waste disposal. In the case of water floods in tight formations, fracturing water injectors may in fact form a part of the development policy, competing with horizontal injectors. Accurate simulation of fracture size, geometry and possible vertical containment is required to ensure an optimal injection policy, but measuring fundamental rock mechanical parameters such as fracture toughness and the poro/thermo-elastic constants have, until now, been confined to laboratory measurements or microfrac tests. In this paper we describe a novel technique which will enable the in-situ measurement of these basic parameters from a pressure transient test under fracturing conditions, assuming a pre-existing fracture of known size. This technique eliminates the uncertainty in length scale inherent in microfrac tests and hence will provide a more accurate measurement of fracture toughness, thus enabling more accurate predictions of fracture size, geometry and containment. The new model explicitly combines a transient description of fluid flow - including two phase flow - and the underlying rock mechanics to allow the prediction of the early rate of growth of a water injection induced fracture. The model gives the useful result that the traditional square root time plot can be used to precisely locate the pressure at which fracture growth begins and over a limited period of time to estimate the early rate of fracture growth. Based on this observation, we also demonstrate a graphical method for deducing fracture toughness directly from in-situ test data.
Determining Reservoir Properties in Reservoir Studies Using a Fuzzy Neural Network
Authors: Zhou Cheng Dang , Wu Xi-Ling , Cheng Ju-An
Published: December 2007

The uncertainty, fuzziness and incompleteness widely existent in reservoir studies require a powerful tool to deal with them more precisely. And fuzzy sets and neural networks seemed quite suitable for this purpose. In reservoir studies, it would be very advantageous to combine the symbolic level of processing conveyed by fuzzy sets with the computational power of neural networks. With the advantage of fuzzy sets in knowledge representation and the high capacity of neural networks in learning knowledge expressed in data, in this paper, a fuzzy neural network is used to solve for the inverse problems in reservoir studies with the purpose of determining the reservoir properties from well logs.

This paper presents a fuzzy neural network approach for determining reservoir properties from well logs, based on fuzzy sets and a self-organizing mapping neural network. Both the details of the algorithm of this fuzzy neural network and its implementation are given.

A field example for recognizing lithology from well logs is used to demonstrate the dependability of this fuzzy neural network approach.
Laminated Reservoir Evaluation in a Case of High Apparent Dip
Authors: Frisch G. J. , Gulick B. D. , Manning M. J.
Published: December 2007

In several offshore reservoirs composed of thin, interbedded sands and shales, a recently reported technique to correct standard induction logs for the effects of formation dip is incorporated into an established method for the well log analysis of laminated reservoirs to yield a superior petrophysical characterization.

Both shale anisotropy and bedding effects are included in the correction of the induction log for apparent dip. In a single well, electrically anisotropic properties of shales are difficult to determine solely by well logs. In the example reservoir, multiple wells with varying hole deviation were drilled from the same platform. By analyzing logged intervals from different wells, the electrical anisotropy of the shales is determined and appropriate corrections are made to the induction log.

Procedurally, a laminated reservoir analysis technique using a dipmeter or another high resolution shale indicator is first applied to the log data. Induction resistivities are corrected for dip effects arising from both sand/shale boundaries and shale anisotropy using an estimate of anisotropy. Then, corrected induction resistivities are used in the laminated reservoir analysis technique. Finally, parameters related to shale anisotropy are varied so that the analyses of wells with high and low apparent dip are consistent.

Quantitative analysis within each individual well is improved using these methods; more importantly, the combined techniques allow comparative evaluations between wells with significantly different hole deviations. Therefore, inclusion of dip effect corrections yields a more accurate well-to-well comparison in laminated reservoirs.
Fracture Evaluation from Quantitative Azimuthal Resistivities
Authors: Faivre Ollivier
Published: December 2007

The ARI* Azimuthal Resistivity Imager is a standard laterolog equipped with an additional segmented electrode. This segmented electrode provides twelve deep calibrated azimuthal resistivity measurements. As any electrical device, the ARI tool is sensitive to fractures filled with conductive fluid. Finite-element modeling was performed to study the tool response to fractures. It shows that techniques similar to those used to characterize fractures with the FMI* Fullbore Formation Microlmagcr can be used with the ARI tool. But it also demonstrates that the extension of the fracture (or the length of mud invasion for an oil filled fracture) and its width (aperture) are equally important parameters when characterizing the fracture. From the resistivity image, the geometry of the fracture (dip and azimuth) can be computed. A lower limit of the fracture aperture and a lower limit of the fracture extension can be estimated from the azimuthal resistivities. Log examples illustrate the proposed technique.