bluuebunny/crossref_metadata_2025 huggingface dataset:
Improve Your Gas Lift Design
Authors: Mukherjee H. , Brown K. E.
Published: December 2007

This paperdiscusses the state of the art in gas lift technology. Different sensitivity parameters in the continuous and intermittent gas lift design systems are explained. Common methods of trouble shooting gas lift wells are also presented.
Computer Modeling for Strategic Planning of Petroleum Exploration and Production
Authors: Katz M. L. , Campbell W. M. , Blackburn C. R.
Published: December 2007

A computer model has been constructed and usedfor strategic planning in an integrated oil and gas company. The model contains representations ofopportunities in exploration, drilling, producingplant, and other types of exploration and production investments. The user specifies alternative strategies and alternative economic scenarios, anduses the model to examine the consequences of these strategies.

Examples are shown of the use of the model to calculate present worth, profit effects, and cashflows for two different economic environments, with a strategy designed to maximize present worth. The consequences of misunderstanding the future economic environment are examined. Other types of model uses which have proven useful are reviewed and summarized.
The Development of the Dubai Condensate Recovery Facilities in the United Arab Emirates
Authors: Bick H. A. , Caceydo L.
Published: December 2007

The description of the development and facilities of the Margham field in Dubai, United Arab Emirates, is the subject of this paper. In February, 1980, ARCO International Oil and Gas Co., adivision of Atlantic Richfield, signed a concession agreement with the Government of Dubai, in the United Arab Emirates. In March, 1982, with Britoil as a partner, a discovery well was completed that confirmed a thick accumulation of gas condensate.

The principals agreed to immediate development, and construction of the production facilitieswas completed in late 1984.

This gas-condensate field is currently producing 24,000 barrels per day (3815 m3/day) of condensate and reinjecting 300 MMSCFD (8.5 × 106 standard m3/day) of the produced gas. As of October 1, 1985 it hadproduced eight million barrels (1.27 × 106m3).
The Role of Bit Type and Drilling Fluid Type in Drilling Performance
Authors: Morton E. K. , Clements W. R.
Published: December 2007

The drilling efficiency of any operation is directly related to borehole stability and optimized drilling parameters. Borehole stability is directly related to reactions with the drilling fluid being used. Penetration rate, although directly related to the strength of the formation, can also be affected by the drilling fluid.

Many active drilling areas around the world have seen the advent of new drilling fluid systems along with new types of drilling bits. A study was initiated to correlate the similarities of these two aspects into the improved penetration rates being realized. Primary interest has been with the use of the PCD (polycrystalline) bits and the use of oil muds, especially the low toxicity oil muds for offshore use. The oil mud drilling fluid has prevented many of the wellbore instability problems that can occur with the use of water base muds. With the use of oil muds and the PCD bits, considerable savings in drilling costs have been realized.
Hydraulic Fracturing of Jointed Formations
Authors: Murphy H. D. , Fehler M. C.
Published: December 2007

Measured by volume, North America's largest hydraulic fracturing operations have been conducted at Fenton Hill, New Mexico to create geothermal energy reservoirs. In the largest operation 21,000 m of water were injected into jointed granitic rock at a depth of 3.5 km. Microearthquakes induced by this injection were measured with geophones placed in five wells drilled into, or very close, to the reservoir, as well as 11 surface seismometers. The large volume of rock over which the microearthquakes were distributed indicates a mechanism of hydraulic stimulation which is at odds with conventional fracturing theory, which predicts failure along a plane which is perpendicular to the least compressive earth stress. A coupled rock mechanics/fluid flow model provides much of the explanation. Shear slippage along pre-existing joints in the rock is more easily induced then conventional tensile failure, particularly when the difference between minimum and maximum earth stresses is large and the joints are oriented at angles between 30 and 60 degrees to the principal earth stresses, and a low viscosity fluid like water is injected. Shear slippage results in local redistribution of stresses, which allows a branching, or dendritic, stimulation pattern to evolve, in agreement with the patterns of microearthquake locations. These results are qualitatively similar to the controversial process known as "Kiel" fracturing, in which sequential injections and shut-ins are repeated to create dendritic fractures for enhanced oil and gas recovery. However, we believe that the explanation is shear slippage of pre-existing joints and stress redistribution, not proppant bridging and fluid blocking as suggested by Kiel.
Stimulation Studies of Chinese Formations
Authors: Parker M. A. , Adams R. W. , Liankui L.
Published: December 2007

Tests to determine mineralogy and formation characteristics were conducted to collect data on formations from the Sichuan Basin, the Zhong Yuan area, the Su Field and the Renbei Field.

This paper will outline the test results and treatment recommendations for stimulation of the various formatioils. A brief review of completion techniques is included. The completion technique can have a direct effect on the type of treatment procedure that is employed.
Pressure Derivative Enhances Use of Type Curves for the Analysis of Well Tests
Authors: Pirard Y. M. , Bocock A.
Published: December 2007

Numerous type-curves of dimensionless pressure versus dimensionless time have been developed in the past. They all suffer from the fact that the log-log representation has poor resolution at late time, thus the uniqueness of the match is reduced.

The semi-log representation enhances the character of the pressure response but, because of the cartesian pressure scaling, the type curve technique cannot be applied. This drawback is alleviated by plotting the slope of the semi-log curve (i.e. the pressure differentiated with respect to the logarithm of time) on a log-log grid. The pressure type-curves differentiated in the same manner can thus be matched to the derivative data. The matching procedure is further improved by combining on the same plot both pressure and derivative data.

Field examples are presented showing how interpretation is enhanced by using the derivative. It is shown that the derivative sheds light on facets of pressure response that were imperceptible on pressure data alone.

The derivative can also be used to deconvolve pressures during the afterflow period of a build up, to compensate for the wellbore storage effect. Provided the wellbore storage coefficient is reasonably constant, the true reservoir response, which is masked at early times by wellbore storage, can be restituted allowing interpretation of early time data. This proves especially useful in the case of heterogeneous formations with permeabilities on the high side, as demonstrated by the examples.
Techniques for Simulating Complex Reservoirs
Authors: Hillestad J. G.
Published: December 2007

Advances in computing hardware and software have provided the reservoir engineer with a wide range of alternatives in analyzing and projecting reservoir behavior. The ability to economically run large simulation models offers a means to generate more accurate technical answers and to develop full-field models of larger, more complex reservoirs. However, there are still situations, due either to reservoir complexity or size, in which full-field models will not be practical. Therefore, detailed segment models will continue to be an important part of reservoir behavior analysis and development planning, and there is still a need for approximate approaches, such as the use of pseudo relative permeability and capillary pressure functions.
Delineation of River-Channel Reservoirs by Seismic Lithologic Modeling of 3-D Seismic Data in Southern Alberta
Authors: Gelfand V. A. , Taylor G. , Tessman J. , Larner K. L.
Published: December 2007

Although river-channel reservoirs are attractive because of their potential high porosity and permeability, their development is difficult because of rapid variations in the distribution of sands and shales. The Taber-Turin area of Alberta, Canada is a known oil province characterized by such reservoirs. To delineate potential reservoirs in detail, a 4 -km 3-d seismic survey was conducted, resulting in a square grid with traces 20-m apart. The Seismic Lithologic Modeling (SLIM™) process, an automated procedure that refines initial geologic models, was then applied to provide a thin-layer interpretation of the processed data. Although the initial model for the SLIM process was based on information from only one borehole (primarily for calibration purposes), the derived velocity model revealed, in detail, the thin Glauconitic reservoirs (0-30 m thick) that are the targets of the delineation effort. All six boreholes previously drilled in the area, four of them producers and two dry, are consistent with the SLIM interpretation. With the help of the SLIM results, three additional boreholes were proposed. To date, two of them have been completed, and both are oil producers.
Drill-Stem Testing From a Floater: The Practical Approach
Authors: Rolleg M. E.
Published: December 2007

Many different aspects of DST procedures must be considered in floating drilling operations. Over the years, viable procedures have been developed as DST technology, equipment and quality of data have improved. This papr discusses actual field-developed operational procedures and proven equipment applications based on floater operations conducted in the South China Sea, Gulf of Mexico, North Sea and Mediterranean Sea from the deployment of semisubmersibles, shipshaped rigs and drilling barges.
Prediction of Miscibility for the Enriched-Gas Drive Process
Authors: Kuo S. S.
Published: December 2007

Minimum miscibility pressure (MMP) is an important parameter for screening and selecting reservoirs for miscible gas injection projects. This paper presents a new correlation for the enriched-gas process that can be used to calculate the miscible slug compositions which consist of methane and mixtures of intermediate molecular weight hydrocarbons such as ethane to butane. The miscibility correlation was developed from MMP predictions of four reservoir fluids and several enriched-gas mixtures using the Peng-Robinson equation-of-state model. The correlation can be used to predict MMP for a fixed slug composition, or predict methane concentration for a given operating pressure. The correlation was tested with published data and showed an average prediction error of ± 2.5 mol% methane.

The miscibility conditions for two reservoirs and several enriched-gas mixtures were also determined in this study using slim tube apparatus. The miscibility in the slim tube tests was judged from the change of phases in the miscible transition zone rather than arbitrarily choosing oil recovery at the 90% level. A photosensor was used to aid the determination of miscibility. This experimental technique has proved to be very consistent. The results of these tests were compared with the new correlation and showed an average prediction error on MMP of less than ± 4%.

In general, either a higher pressure or a higher concentration of C2 to C4 hydrocarbons in the injection gas is required for achieving miscibility as (1) reservoir fluid C5+ molecular weight increases, (2) average molecular weight of C2 to C4 components in the injection gas decreases, or (3) reservoir temperature increases.
Photoelastic Modeling of a Complex Welded Structural Assembly
Authors: Fowler David W. , Panak John J. , Matlock Hudson
Published: December 2007

Publication Rights Reserved

This paper is to be presented at the Society of Petroleum Engineers of AIME Symposium on Offshore Technology and Operations to held in New Orleans, La., May 23–34, 1966, and is considered the property of the Society of Petroleum Engineers. Permission to publish is hereby restricted to an abstract of not more than 300 words, with no illustration, unless the paper is specifically released to the press by the Editor of the Journal of Petroleum Technology or the Executive Secretary. Such abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. publication elsewhere after publication in Journal of Petroleum Technology or Society of Petroleum Engineers Journal is granted on request, providing proper credit is given that publication and the original presentation of the paper

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

A welded bracket supporting the leg of an offshore drilling unit was investigated by means of a photoelastic model after proving to be too complicated for analysis. The steel plates were modeled by plastic sheets and welded joints were simulated with epoxyresin. The model was subjected to different loading and restraint conditions. Stresses were computed from readings taken with a reflecting polariscope. The tests demonstrated that welded structural assemblies may be reasonably simulated by the epoxy-to-plastic combination.

Introduction

A complex welded bracket supporting the leg of a mobile drilling unit proved to be too complicated for theoretical analysis. An experimental model investigation seemed to be the most logical solution since the large size of the bracket made full-scale testing impractical.

A photoelastic model (Fig. 1) was constructed in which steel plates were modeled by birefringent plastic sheets and welded joints were simulated with epoxy resin; the more usual procedure is to bond the plastic sheets to the actual structure or model itself. Static load was applied to the model by means of dead weights on a pin that transmits forces to a leg of the structure in the prototype. The bracket model was tested with two different degrees of restraint corresponding to two different assumptions about the support offered by the hull of the barge. As in the prototype, reinforcing billets and struts were added to the model structure. Photoelastic readings were taken by means of a reflecting polariscope. With the model fringe values of the plastic sheets known, the stresses in the model were determined. Prototype stresses can be easily scaled from the model stresses.

PHOTOELASTICITY

David Brewster's discovery in 1816 that some materials become doubly refractive when subjected to stress marked the beginning of the science of photoelasticity.
The Pressure Transient Behavior for Naturally Fractured Reservoirs With Multiple Block Size
Authors: Cinco-Ley H. , Samaniego V. F. , Kucuk F.
Published: December 2007

A new analytical model is presented to study the pressure-transient behavior of a naturally fractured reservoir composed of a fracture network and matrix blocks of multiple size. Matrix blocks are considered to be uniformly distributed--through a reservoir of infinite extent. A general model for fluid transfer between matrix and fractures is established; this model justifies the use of both the Warren and Root model and the transient matrix flow model for double porosity systems.

The multiple block size situation is handled through the use of a distribution function f(hma) that represents the fraction of matrix pore volume contained in blocks of size hma. It is demonstrated that classical parallel semilog straight lines can be present under these circumstances and the transitior zone may exhibit the characteristic half slope straight line when there is no flow restriction between matrix and fractures; --however, the transition between the end of the second and the third semilog straight line appears to be longer. It is found that the behavior of this type of systems is dominated by matrix of smaller size and the matrix blocks size computed from well testing by using the semilog straigt line intersection method corresponds to the weighted harmonic average; that is, in discrete form 1/h¯ma  =  Σi=1NB  f i/hmai where NB is the number of block sizes.

On the other hand, the λ value from well test analysis corresponds to the arithmetic weighted average, that is λ  =  Σi=1NB  f iλ i. These findings are important wher applying the transient pressure result to waterflooding project design.
Mixing in Underground Storage Reservoirs
Authors: Carrière J. F. , Fasanino G. , Tek M. R.
Published: December 2007

Underground storage fields developed on aquifers or converted from producing reservoirs frequently encounter problems related to molecular transport and mixing phenomena. The need for understanding flow and displacement processes as affected by mixing and dispersion in the porous matrix surrounding storage wells is important, both in design and operation of storage units.

There are four specific occasions where mixing and dispersion takes on practical significance in storage: Total or partial conversion of working inventory from native to pipeline quality dry gas.Use of the storage unit for selective storage of gases having different compositions.Prospects of replacing part of the cushion gas by a lean or inert substitute.Use of chemical or radioactive tracers in investigating possible leak paths.

In order to provide a capability to predict the field performance as affected by mixing and dispersion, a new methodology has been developed which emphasizes numerical simulation implemented by appropriate computer programms. The programms permit calculation and graphical tracking of the front separating the gases involved in the miscible displacement process as affected by heterogeneities, operating conditions and the physical dispersion. Identification of physical parameters necessary for appropriate modeling is included.

The field data reported in the paper include one storage reservoir where an entire working inventory and about half of the cushion gas, have been displaced by cycling a gas of different characteristics. Similar conversions are currently being planned for two other storage reservoirs in the next few years.

In an area which will have profound implications in economics of underground storage, interesting data have been collected by substituting inert gas for part of the cushion gas in two storage reservoirs. One of these substitutions has recently been completed while the other is in progress.
Estimation of the Coefficient of Inertial Resistance in High-Rate Gas Wells
Authors: Noman R. , Shrimanker N. , Archer J. S.
Published: December 2007

The pressure drop due to non-Darcy flow in a gas well producing at high rates can be determined from analysis of multi-rate pressure test data. In the absence of such data calculation of the non-Darcy term requires a knowledge of the coefficient of inertial resistance.

This paper presents correlations for estimating the coefficient of inertial resistance from reservoir porosity, permeability and gas saturation. These correlations were derived from analysis of multi-rate pressure tests conducted in over one hundred gas wells and are supported by experimental data using core plugs. They are found to be better than other published relationships in predicting observed performance.
Chemical Stability of Polyacrylamide Under Simulated Field Conditions
Authors: Yang S. H. , Treiber L. E.
Published: December 2007

The chemical instability of Polyacrylamide polymer during both polymer and micellar-polymer flooding can seriously affect flood performance. Results of this study utilizing special laboratory techniques and long-term tests to simulate conditions typical of petroleum reservoirs show the effects of key variables on chemical stability. The rate and extent of degradation are governed most by oxygen content (although limited oxygen produces only limited degradation) and temperature. Metal ions, pH, and redox reactions can also have a major influence on degradation.
Prediction of Formation Response from Fracture Pressure Behavior
Authors: Conway M. W. , McGowen J. M. , Gunderson D. W. , King D. G.
Published: December 2007

During examination of numerous treating pressure charts, it was discovered that most wells exhibited predictable pressure changes which could be classified into a limited number of generic formation treatment types. Once a limited number of calculations of bottom-hole treating pressure (BHTP) and instantaneous shut-in pressures (ISIP) are obtained early in the treatments, these formation type curves can be utilized to identify the anticipated pressure changes during the treatment.

Subject paper identifies five basic types of treating pressure behaviors with physical interpretations describing the proposed fracture geometry associated with each response. An optimum fracture treatment is proposed as an aid for fracture pressure interpretation both during the treatment and during post-job analysis.

Guidelines for post-treatment analysis are presented showing the use of treating pressure history as an aid to improving future fracture treatment design in a given formation.
Four-Parameter Modification of the Lawal-Lake-Silberberg Equation of State for Calculating Gas-Condensate Phase Equilibria
Authors: Lawal A. S. , Van der Laan E. T. , Thambynayagam R. K. M.
Published: December 2007

The rapid development of digital computers during the past several years has made the calculation of hydrocarbon phase behavior feasible by methods based on rigorous thermodynamic principles. A number of these methods report comparisons of cubic equations of state (EOS) and laboratory PVT results for a wide variety of reservoir fluids and conditions. Most of them emphasize the C7+ fraction splitting as the key element in attaining an agreement between EOS and laboratory results. The work reported in this paper reflects our experience with predictive EOS without splitting C7+ fraction to match laboratory data. The use of the Four-Parameter modification of Lawal-Lake-Silberberg (LLS) EOS has made the splitting of C7+ fractions and the adjustment of EOS parameters unnecessary.

A modification of the LLS EOS has been formulated specifically for application to gas condensate reservoir fluids. The modification consists of establishing the heptanes-plus coefficients, αc7+, βc7+ in the attractive pressure term and new parameters for Ac7+ and Bc7+ which are related linearly to the characteristic properties of heptanes-plus fractions. These characteristic properties, molecular weight, API gravity, and Watson characterization factor are obtained from 4460 experimentally determined data points of condensate reservoir fluids which cover a range of temperatures from 40°F to 322°F and pressures up to 15,500 psia. The usefulness of the modified LLS EOS in improving phase equilibria predictions of complex systems without splitting C7+ fraction is illustrated by applying the EOS to several crude-oil and gas-condensate systems. The LLS EOS was also applied in predicting laboratory PVT data of published multicomponent systems which contain significant amounts of aromatic hydrocarbons. The prediction results of applying other equations of state (PR, SRK) without altering their parameters are also presented for comparison.
Automatic Facies Analysis in the Arab Formations, El Bunduq Field, Offshore Abu Dhabi/Qatar
Authors: De La Cruz M. A. , Takizawa H.
Published: December 2007

A computer-based program has been used for zonation of wells into electrofacies according to log responses. The process determines a number of clusters from similar log values.

To ensure that the electrofacies obtained are geologically meaningful, log responses from key wells were calibrated with geological facies from cores. Input logs were selected accordingly.

The creation of a data bank helped to obtain consistency in the twenty-six wells processed in El Bunduq field offshore Abu Dhabi/Qatar.

The complex and variable lithology of the Arab formation provided good log contrasts for clear zonation into eleven electrofacies which were identified with facies described in cores. The occurrence of these electrofacies reflects their origin in different sedimentary and diagenetic environments.

The following stratigraphic relationships were observed: –The cyclical character of the upper Arab formations A, B, and C showing several carbonate-anhydrite cycles (electrofacies F7 to F16)–The thickness and frequency of the anhydrite beds increase upwards from the Arab C to the Arab A (electrofacies F7).

Correlation of electrofacies from well to well indicates that: The high complexity of diagenetic facies and their lateral changes affecting reservoir quality can be monitored.Reservoir quality in the Arab C increases towards the crestal zone due to the occurrence of less anhydrite (F7, F8) in the carbonate facies.In the Arab D, porous electrofacies F3 and F5 (porous and dolomitic mudstones) are well represented in the crestal part of the field but get very thin or pinch out towards the flanks.
Developments in the Simulation and Design of Multiphase Pipeline Systems
Authors: Norris H. L. , Fuchs P. , Malnes D. , Klemp S.
Published: December 2007

Two-phase pipelines offer the potential for substantial cost savings in the offshore transport of hydrocarbons. Their design has been hampered by uncertainties in two-phase pressure drop relations, in flow regime determination, and in liquid slug length prediction. This uncertainty makes difficult the choice of pipe size and the design of downstream separation facilities. In order to reduce the uncertainty in two-phase flow pipeline design, Esso, Statoil, Mobil, Texaco, and Getty have sponsored the construction of the Norwegian Two-Phase Flow Laboratory now being operated by SINTEF. A large pipeline-riser expe imental facility has bee constructed to obtain laboratory quality data in a field scale apparatus. In addition, analytical modeling о two-phase flow is proceeding to provide a framework for interpretation of the experimental measurements. The experimental facility, results of experimental measuremen s, and analytica modeling techniques are described. The two-phase flow data and analysis resulting from this project promise to reduce substantially the uncertainty in the design of two-phase pipelines and downstream separation facilities.
Enhanced Oil Recovery by Surfactant-Enhanced Volumetric Sweep Efficiency
Authors: Arshad A. , Harwell J. H.
Published: December 2007

A new enhanced oil recovery process is proposed for improving volumetric sweep efficiencies in reservoirs. The new process makes use of the chromatographic and phase separation behavior of surfactants to seal off high permeability, low residual oil saturation regions of reservoirs. Though making use of surfactants, the new process is not to be confused with classical (low tension) surfactant flooding, which is designed to enhance oil recovery by reducing oil/water interfacial tensions. In the new process, a sequence of surfactant species is injected into the reservoir. Those injected last are chosen to have higher chromatographic velocities than the former. The species are also chosen so that when they mix in situ, a phase separation occurs, resulting in formation of a pore blocking precipitate or of a high viscosity gel-like coacervate phase. Because the oil recovery mechanism is completely different from that in low tension surfactant flooding, the new process can operate at much lower surfactant concentrations and higher injectivities, greatly reducing the upfront costs of the new process, improving its economic feasibility. Sandpack studies are presented to demonstrate: 1. The process mechanism, 2. The ability of ppm concentrations of surfactant to plug porous media on in situ mixing, 3. The ability of the process to selectively plug high permeability regions, 4. The ability of the process to produce a tertiary oil recovery from a sandpack. Various potential advantages of the new process over other currently developing sweep efficiency enhancement processes are also briefly discussed.
New Technology and Tools for the Recovery of Representative Cores From Uncemented Sand Formations
Authors: Tibbitts G. A. , Radford S. R.
Published: December 2007

Coring the uncemented Faja Petrolifera del Orinoco oil sands in Venezuela is a difficult operation. In order to obtain better formation characteristics from the Faja oil sands, a laboratory research program was conducted to develop techniques and equipment to core these sands. The laboratory tests showed that specific coring parameters and mud compositions must be maintained during the coring process, and that a fully open entry and full closure core barrel coupled with a polycrystalline diamond compact core bit are essential to successful core recovery. These techniques and equipment were then used to recover uncemented sand in the field.
A Method To Identify the Effects of No-Flow Boundaries Upon Pressure Buildup Data
Authors: Payne R. E.
Published: December 2007

A technique has been developed to identify the effects of no-flow boundaries by using the deviation of pressure buildup data from the infinite-acting case. A dimensionless, pressure depletion group consisting of the measured initial reservoir pressure, the extrapolated pressure from the Horner plot and slope of the infinite acting data on the Horner plot is used as a parameter. The ratio of the late time slope to the middle time slope on a Horner plot is plotted against the Horner plot time. For a given value of the dimensionless pressure depletion group, these data are matched against the curves for a given boundary configuration. Analysis of actual field data has been included to illustrate this technique.
GEODYN2: A Bottomhole Assembly/Geological Formation Dynamic Interaction Computer Program
Authors: Baird J. A. , Caskey B. C. , Wormley D. N. , Stone C. M.
Published: December 2007

This paper describes the current development of a three-dimensional transient dynamic finite element computer program, GEODYN2, capable of simulating the behavior of a rotating bottom hole assembly (BHA) interacting with a non-uniform formation. The GEODYN2 Program facilitates a very detailed analysis/ simulation of the behavior of a BHA with a polycrystalline diamond compact (PDC) bit and various stabilizer designs. The basic drill string mechanics implemented within the program, the overall algorithm, and the more pertinent modeling features which permit this level of analysis are briefly outlined. The implementation of these features and how they allow calculation of the response behavior of a bottom hole assembly are demonstrated. Although the development and enhancement of modeling capabilities within GEODYN2 is ongoing, it is anticipated that the preliminary verification results thus far generated will further the understanding of the response behavior of BHAs.
Probabilistic Stability Analysis of Multiphase Flow in Porous Media
Authors: King M. J. , Scher H.
Published: December 2007

The problem of viscous fingering in multi-phase fluid flow in porous media affects the understanding, design, and evaluation of both laboratory experiments and reservoir processes. Existing methods of studying fingered floods are either phenomenological, or rely heavily on high order numerical methods. In this work, a novel "random walk" analysis is described and utilized to study both miscible and immiscible floods. Simple "walking" and "trapping" rules are derived directly from the usual differential equations describing multi-phase flow. It is straight forward to include the effects of capillary pressure, heterogeneity, diffusion-dispersion, gravity, different geometries, and to study multiple (>2) phase flow.

The random walk model implicitly performs a stability analysis as the flood proceeds. The solutions vary from compact to highly fingered profiles, depending upon the value of the mobility ratio, M. The entire range of displacements, from stable to unstable, may be simulated.

The random walk methods are an extension of the diffusion-limited aggregation (DLA) model of Witten and Sander. The concept of trapping has been substantially generalized beyond that of DLA. The DLA rules are recovered dynamically as a special case in the extreme mobility (M → ∞) limit.
Replacement Costs of Domestic Natural Gas
Authors: Kuuskraa V. A. , Morra F.
Published: December 2007

As the country uses its reserves of natural gas, it will need to continually replenish them if production is to be maintained. The outlays associated with this continuing search, development and production of new reserves is defined as "replacement costs." Thus, the replacement cost of natural gas is the minimum selling price a firm must receive to recover its costs and to achieve a reasonable return on capital.

This paper estimates the range of natural gas replacement costs to the year 2010 and measures the uncertainty associated with these estimates due to the size of the underlying resource base, new unconventional gas extraction technologies, and the rate of domestic gas production.
Drilling with PDC Bits on Rotary vs. Downhole Motor: Southeast Central Texas Austin Chalk Fields
Authors: Pain D. D. , Johnson E. T. , Byers R. H. , Vader E. R.
Published: December 2007

Polycrystalline diamond compact (PDC) drill bits have proven to be economical in the Austin Chalk fields in Southeast Central Texas. Many contractors have expressed concerns over reduced drill pipe life when using the PDC bits on rotary because of the higher rotating speeds and higher bit torque. Field results and economic analyses show that PDC bits are more cost-effective, even with reduced drill pipe life, than roller-cone bits in the proper formations. These results also show that the use of downhole motors in conjunction with PDC bits can eliminate the problem of premature drill pipe failures, while still resulting in lower overall drilling costs and fewer days to drill a well.
Surfactants for CO2 Foam Flooding
Authors: Borchardt J. K. , Bright D. B. , Dickson M. K. , Wellington S. L.
Published: December 2007

A great deal of information has been published on the use of surfactants in CO2 foam flooding applications. However, generally the chemical composition of the surfactant has not been specified and little work describing the relationship of surfactant chemical structure and physical properties to foaming agent performance has been reported. This laboratory study examines the performance of more than 40 surfactants in 1 atmosphere foaming experiments. Several classes of surfactants were studied including alcohol ethoxylates, alcohol ethoxysulfates, alcohol ethoxyethylsulfonates and alcohol ethoxyglycerylsulfonates.

Surfactants which performed well in the 1 atmosphere (1.01 X 105 Pa) foaming experiment were also good foaming agents in sight cell and core flood experiments1,2 performed in the presence of CO2 and reservoir fluids under realistic reservoir temperature and pressure conditions.
Field Test of CO2 Mobility Control at Rock Creek
Authors: Heller J. P. , Boone D. A. , Watts R. J.
Published: December 2007

This paper reports the objectives, design and progress of a field test of "CO2-foam" as a lowered mobility displacing fluid. It includes the background of mobility control considerations leading to the trial, and describes the influence on it of various operational conditions and constraints. The Rock Creek oil field of Roane County, West Virginia, has been produced since 1906 from a low permeability sandstone with high clay content, and is now near the end of economic life. The area utilized in this test is a smaller portion of two ten-acre five-spots that have been subjected to a conventional CO2 flood and subsequent waterflooding, in addition to gas recycling and primary production. A major goal of the test was to determine whether the oil remaining in this area could be displaced by a slug of thickened CO2 to form a mobile oil bank that could be detected at a nearby observation well. A second goal was to test the injectivity of CO2-foam as liquid CO2 and dilute surfactant solution were pumped simultaneously down fiberglass tubing into the injection well. The design of the test was based on published measurements of the ability of the chosen surfactant (Alipal CD128) to form a foam-like dispersion with liquid CO2, on stability at reservoir temperature (73°F; 23°C), on the extent of adsorption onto the reservoir rock, and on the appropriate values of the relative mobility of the CO2-foam (0.2 cp−1). Although it has been possible to inject more than half of the specified quantity of CO2-foam, lowered injectivity and other field circumstances have as yet prevented the test from proceeding far enough to show an unequivocal result for the first objective.
Prediction of Compositional Grading in a Reservoir Fluid Column
Authors: Montel F. , Gouel P. L.
Published: December 2007

A method of predicting fluid compositional grading with depth is presented. It was designed to enable numerical simulations of this phenomena, now required in compositional model studies: the nature of petroleum fluids today (condensate gases, volatile oils, "critical" fluids) increases this need.

Based on ONSAGER's theory, general relations between compositional grading of a fluid with depth make predictive calculations of this evolution possible.

Our method only takes into account the gravitational effect; it enables to calculate the phase behavior of a fluid everywhere in a column, assuming the stationary state has been reached. The proposed algorithm is an iterative calculation based on the fugacities of each component at different depths; knowing pressure, temperature and overall composition at a reference depth we can predict the compositional grading, gas-oil contact location and even physical state change with depth.

The required conditions to realize such a prediction are discussed.

In addition, a "new" thermodynamic fitting method is suggested.

An example is given for a North Sea real "critical" fluid; it clearly shows that the gravitational segregation alone can largely explain the compositional grading observed in the reservoir.

PVT and compositional simulations of the fluid are based on the PENG-ROBINSON's equation of state1 but this method can be developed with any other equation.
Wm. Berryhill Micellar Polymer Project: A Case History
Authors: Crawford C. C. , Crawford M. E.
Published: December 2007

This paper describes the implementation of the expansion phase of the Wm. Berryhill Micellar-polymer flood. Stages in the injection processes and related problems are presented in chronological order. When developments in the pilot project dictated changes in the expansion, the pilot experience is discussed in detail.

In 1979, a pilot micellar polymer project was initiated in the Glennpool Field southwest of Tulsa, Oklahoma, on the Wm. Berryhill lease. The 18 acre pilot project was maintained until September, 1983, injecting into the upper member of the Bartlesville (Glenn) sand. Field tests from observation wells prompted expansion of the flood in 1982 to the adjacent 92 acres of the lease and to include the Middle Glenn sand.

Since lithology plays an important role in the flood behavior, the case history is prefaced by a geological review and reservoir characterization.

While the pilot production response indicates the flood to be a viable process, the expansion is an on-going project with final results yet to be determined. The flood is currently in the polymer phase, which will continue through May, 1987.
Fractured Water-Injection Wells: A Pressure Falloff Test for Determining Fracture Dimensions
Authors: Koning E. J. L. , Niko H.
Published: December 2007

Pressure transient theory for a water-injection well in the presence of a closing fracture and a discontinuity in fluid mobility is developed in elliptical coordinates. Solutions are obtained using the Laplace transform and numerical inversion. From the results it is concluded that a pressure fall-off test with a closing fracture, in principle provides three different methods for determining the fracture length. The first method is based on rock mechanical principles only. The second method makes use of formation linear flow. The third method analyses the transition of the pressure transient from the inner fluid region to the outer region in conjunction with a heat or volume balance. If more than one method is applicable consistent results should give a reliable estimate of the fracture length. The in-situ horizontal rock stress can also be determined from the test. It is equal to the pressure at which the closing of the fracture is observed.
Improved Lithology and Hydrocarbon Saturation Determination Using the Gamma Spectrometry Log
Authors: McGuire J. A. , Rogers L. T. , Watson J. T.
Published: December 2007

Many papers have been written describing the theory and interpretation models of the GST* gamma spectrometry tool. This paper presents actual field examples where GST interpretation techniques were used to improve lithology identification and pore-fluid saturation determination. Examples are of varied geographic locations and reservoir conditions.
Sand Transport Experiments in Thin Fluids
Authors: Medlin W. L. , Sexton J. H. , Zumwalt G. L.
Published: December 2007

Computer-controlled experiments were conducted by flowing thin, sand-laden fluid through a long lucite slot model. An optical absorption method was used to obtain computer-generated sand density profiles at a distance far from the slot entrance. Profiles were obtained at various flow rates, injected sand concentrations, and fluid viscosities. These were combined with visual observations from filmed records to investigate the three observed transport mechanisms, bed load, turbulence, and viscous drag. The experimental results were used to test theoretical predictions related to these mechanisms. We find good agreement between theory and experiment. We show that viscous drag is the only important transport mechanism under field conditions. Bed load transport is important in 1aboratory-scale experiments where it can produce equilibrium settled bank heights. But it is unimportant on the scale of field treatments because it does not scale up with slot height. Turbulence contributes little to sand transport under almost any condition. This means there is no transport mechanism for producing equilibrium banks in field treatments. Only viscous drag is left as the dominant transport mechanism in field treatments. This conclusion is examined in the light of large frac treatments using slick water. It is hard to account for the large quantities of sand carried in these treatments by viscous drag alone. This suggests the existence of a fourth mechanism which does not show up in fixed width slot flow experiments. Other possible mechanisms are considered including avalanche effects associated with a growing crack width.
Technically Recoverable Devonian Shale Gas in Ohio, West Virginia, and Kentucky
Authors: Kuuskraa V. A. , Sedwick K. , Yost A. B.
Published: December 2007

Large volumes of natural gas may be technically recoverable from the Devonian shales of Kentucky, Ohio, and West Virginia. The technically recoverable gas from the Huron, Rhinestreet, Cleveland, and Marcellus intervals is estimated to range from 26 Tcf to 82 Tcf, depending on the success of new gas extraction technologies and practices. The total estimated in-place Devonian shale gas of this tri-state area is 394 Tcf. While much of the resource is in the Huron shale interval, significant portions are located in other thinner, yet organically rich, shale units that have experienced less development to date. This study represents the most current appraisal of Appalachian Devonian shale gas potential, and serves as an update of the 1980 National Petroleum Council work for this tri-state area.
Individualized Fracturing Treatment Design Benefits Clinton Sands
Authors: Mack D. J. , Mason R. A.
Published: December 2007

Significant advancements have been made in the past few years in the areas of vertical fracture growth determination and treatment design. Techniques have been developed that use changes in the bottom hole treating pressure to describe fracture growth. In addition, open hole logs are available which will allow for the determination of vertical growth boundaries as a function of the increase in the bottom hole treating pressure.

A series of six wells have been drilled and fractured in the Clinton Formation of Northeast Ohio. Three of the wells utilized frac height logs for pressure boundary determination, while interpolation techniques were used on the other three. Fracture treatments were then designed for each individual well based on the rock properties of that well. The primary consideration in each design was vertical containment of the fracture and the placement of an effective proppant pack across the productive zone. By doing this, the productivity of the well will be increased.

The treatments were then performed and bottom hole treating pressure either calculated or monitored This pressure analysis has indicated fracture containment within the design boundaries.

This paper will discuss the treatment design procedure and results of the bottom hole treating pressure analysis. In addition, an explanation for the general lack of effectiveness of cross-linked and foamed treatment in the study area will be presented.
Geometry Determination for Multi-Stage Acidizing Treatments With or Without Viscous Preflush
Authors: Lee W. S.
Published: December 2007

In recent years, significant progress has been made in the determination of fracture geometry. However, most effort is geared toward massive hydraulic fracturing treatments with proppants. Little progress has been made in the determination of fracture geometry especially for acidizing treatments.

This paper presents a method of determining fracture geometry for fracture acidizing treatment. The fracturing fluids used in an acidizing treatment are classified into four stages: preflush, viscous preflush, acid and overflush, each with different rheological properties. If viscous preflush is not used, relative positions of all fluids together with the resulting geometry are determined simultaneously based on the assumption that fluid pumped at a later time is unable to overtake fluid pumped at earlier time. If viscous preflush is used, relative positions of all fluids, together with the resulting geometry, are determined simultaneously allowing the possibility that acid and overflush can tunnel through and even completly overtake the viscous preflush pumped ahead of acid. Before the acid over takes the viscous preflush, the advancement of acid inside the fracture is rapid, and the acid creates an effective etching pattern. Once the acid overtakes the viscous preflush, its advancement slows down resulting in less effective etching pattern. An optimum design would most likely be the one where live acid barely overtakes the viscous preflush.

Two examples will demonstrate the effective use of this method for better acidizing design.