bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Nordgren's Equation of Hydraulic Fracturing
Authors: Kemp L. Franklin
Published: December 2007

A nonlinear partial differential equation modeling the propagation of a vertical hydraulic fracture first derived by Nordgren is studied. When properly posed, Nordgren's derivation constitutes a Stefan problem and requires another boundary condition—namely, that the velocity of the fluid at the crack tip equals the velocity of crack propagation. With this addition, Nordgren's similarity solution in the no-leakoff case is perfected by a power-series solution. New shut-in solutions are derived in the large- and no-leakoff cases where the crack of the large-leakoff shut-in solution retracts and the crack of the no-leakoff shut-in solution extends forever. This study ignores the effect of crack-tip rock strength on crack propagation.
Velocity Profile Survey in a 16-in. Custody-Transfer Orifice Meter for Natural Gas
Authors: Shen Joseph J. S.
Published: December 2007

This paper describes a research project conducted at Chevron U.S.A. Inc.'s Venice, LA, facility to ascertain that the flow condition inside a nominal 16-in. [406-mm] custody-transfer orifice meter was in compliance with American Gas Assn. (AGA) requirements. The survey was conducted at four flow rates ranging from 160 to 200 MMscf/D [4.53 × 106 to 5.66 × 106 std m3/d] of processed natural gas at 880 psia [6.1 MPa]. Experimental data were collected by a portable data-acquisition system driven by a lap-top microcomputer. The measured profiles indicated that the flow was nearly fully developed at the orifice plate location, and no significant swirling motion was detected.

This test successfully demonstrated the techniques and equipment developed for determining actual flow distributions inside orifice meters in the field under normal operating conditions. This technology can be used to detect detrimental flow profiles and to verify compliance with AGA requirements on flow conditions in custody-transfer orifice meters.
Pulsed-Neutron Monitoring in the Bunter Sands of the Esmond Complex
Authors: Johnson Alan , Scanlon M. E.
Published: December 2007

The fields in the Esmond complex (Esmond, Forbes and Gordon) produce gas from the Triassic Bunter sandstone forma tion. Production started from all three fields in 1985, and an annual cased-hole, pulsed-neutron-monitoring program was initiated in 1986. The main objective of this program was to detect changes in formation water saturation resulting from invasion by influx from the aquifer.

Initial interpretation of the pulsed-neutron logs was hampered by two factors that make the Esmond complex a borderline environment for this type of logging: a large, gas-filled borehole that attenuates the tool response and a halite cement in the formation with a very high capture cross section. Increased understanding of these factors has improved the reliability of interpretations. Recent results indi cate water advance in all three fields. Currently, water production has been observed only on Forbes, the smallest of the three fields. Observed pressure behavior, however, does show the effects of water influx in all three fields, confirming the log indications. Detailed analysis of the log results led to the identification of different modes of water influx, either as an overall rise in the gas/water contact or as fingering along permeable layers. This information is valuable in production planning.
Temporary Chemical Block Brings Efficiency and Economy to Eastern U.S. Workover Operations
Authors: Terracina J. M. , McCabe M. A. , Cramer J. W. , Legenza J. E.
Published: December 2007

Gel plugs (GP's) have been used in the eastern U.S. for many years. They are a versatile and simple method of temporarily plugging a well. Gel plugs are often used to control a well while remedial workovers are performed. This paper describes the various types of gel plugs and their applications. Case histories are given for gel plug applications.
Explicit Pore-Pressure Evaluation: Concept and Application
Authors: Alixant Jean-Louis , Desbrandes Robert
Published: December 2007

A general method was developed to determine pore pressure in undercompacted shales on the basis of explicit relationships among measured shale properties, shale porosity, effective vertical stress, and pore pressure. Although calibration may be necessary, this technique neither uses empirical correlations nor requires establishment of normal trend lines. A modular approach allows users to implement custom equations. This paper outlines the concept and focuses on its application to real-time pore-pressure evaluation based on resistivity measurements.
The Unsteady-State Nature of Sorption and Diffusion Phenomena in the Micropore Structure of Coal: Part 2—Solution
Authors: Kolesar J. E. , Ertekin Turgay , Obut S. T.
Published: December 2007

A single-phase, 1D mathematical model, formulated in Part 1 of this study, is used to study unsteady-state micropore sorption in the composite micropore/fracture coalbed-methane-transport problem. The mathematical model is solved numerically by writing the transport equations in finite-difference form and linearizing the residual form of the difference equations with the generalized Newton-Raphson procedure. The numerical model is used to compare methane production rates predicted by unsteady- and quasisteady-state sorption formulations. Results indicate that the two models give different rates during early degasification periods. The high rates predicted by the unsteady-state model, however, generally approached lower quasisteady-state rates within the first few months of simulation.

The numerical model is also used to examine the time-dependent response of concentration gradients in the micropores to changes in fracture pressure, to compare diffusion rates predicted by spherical and cylindrical micropore elements, and to construct dimensionless type-curve solutions to the coalbed-methane flow problem.
Evolution of a Hybrid Fracture/Gravel-Pack Completion: Monopod Platform, Trading Bay Field, Cook Inlet, Alaska
Authors: Grubert D. M.
Published: December 2007

Placing a small fracture job before an inner-casing gravel pack has evolved as the preferred completion method for some reservoirs in Cook Inlet, AK. The hybrid completion gives the theoretical benefit of higher initial rates provided by the fracture and continuity of production provided by sand control.
Encapsulated Breaker for Aqueous Polymeric Fluids
Authors: Gulbis Janet , King M. T. , Hawkins G. W. , Brannon H. D.
Published: December 2007

Conventional breakers reduce fracturing-fluid viscosity much too rapidly, even at moderate temperatures (140 to 200°F), to be used at the high concentrations required to degrade polymers within proppant packs. A delayed-release, encapsulated breaker was developed that permits the use of high breaker concentrations and thus significantly increases fracture conductivity.
A Method for Selection of Cement Recipes To Control Fluid Invasion After Cementing
Authors: Beirute Robert M. , Cheung P. R.
Published: December 2007

A method to scale down well parameters to laboratory conditions for more realistic testing of cement recipes to be used to control wellbore invasion/migration of formation fluids after cementing is introduced. The scale-down procedure proposed here addresses a worst-case scenario. It assumes that the offending gas zone (source of the invading gas) has enough permeability, thickness, and gas volume to invade fully and to pressure-charge the cemented annulus (cement column), if conditions allow. The method is demonstrated in conjunction with the use of a certain laboratory gas-flow apparatus. This general scale-down procedure can be used with other test equipment.

An imaginary set of well conditions is used to illustrate the mechanics of the use of the technique. Tests run with the procedure and the computer-monitored gas-migration test cell are described. A preliminary set of criteria for selecting a cement recipe for a given well is presented. A field case illustrates the use of the procedure.
Visualization of Fluid-Loss Polymers in Drilling-Mud Filter Cakes
Authors: Plank J. P. , Gossen F. A.
Published: December 2007

The appearance of fluid-loss polymers in freeze-dried drilling-mud filter cakes was studied with scanning-electron-microscope (SEM) photography. Three fluid-loss polymers were studied: starch, polyanionic cellulose (PAC), and a high-temperature- (HT)-stable, sulfonated polymer. The effects of electrolyte contamination (NaCl, CaCl2, and MgCl2) and temperature (200 to 350°F) on the appearance of the fluid-loss polymers were also studied. A correlation between API filtrate and polymer appearance was sought.
A Decade of Drilling Innovation and Progress in the Paris Basin
Authors: Canter D. B. , Simon J.-M.
Published: December 2007

Since 1979, Esso Rep has drilled more than 150 exploration and development wells in the Paris basin. A cost-per-foot reduction of more than 40% was achieved despite a near doubling of rig rates. This paper discusses the unique directional drilling approach used and the drilling, formation evaluation, and contracting techniques.
Heavy Oil From Fractured Carbonate Reservoirs
Authors: Briggs P. J. , Beck D. L. , Black C. J. J. , Bissell Robert
Published: December 2007

This paper investigates the recovery mechanisms for steam injection into naturally fractured, carbonate, heavy-oil reservoirs. Interim ideas and results of laboratory and simulation studies are presented and topics for further investigation are suggested. Results so far indicate that both imbibition and internal gasdrive are effective at driving oil into the fracture network.
Simultaneous Estimation of Relative Permeabilities and Capillary Pressure
Authors: Chardaire-Rivière Catherine , Chavent Guy , Jaffré Jérôme , Liu Jun , Bourbiaux Bernard J.
Published: December 2007

An automatic numerical method is proposed for simultaneous determination of relative permeabilities and capillary pressure from the results of a single two-phase flow experiment in a range of velocities representative of field flow conditions. The experiment is a standard imbibition or drainage displacement with an imposed difference of pressure or flow rate. The experimental data used are the outlet production, the pressure drop between the two faces, and local saturation profiles at different times along the core. Relative permeabilities and capillary pressure are estimated with a least-squares technique. Use of a high-order numerical scheme significantly reduces the numerical diffusion. The optimal control theory is used to solve the minimization problem. The corresponding FORTRAN code is generated by a symbolic program. The validity of the method first is demonstrated with simulated data, then is tested in two laboratory experiments: one imbibition and one drainage. Good agreement is obtained for both situations.
Wettability of Reservoir Core Samples
Authors: Fleureau J. M.
Published: December 2007

This paper presents a method for assessing the preferential affinity of reservoir rocks on the basis of measured contact angles combined with imbibition tests from the same samples. Test results on a model sandstone and three reservoir rocks are compared with those of usual imbibition tests on plugs.
Experimental Investigation of Critical Condensate Saturation and Its Dependence on Interstitial Water Saturation in Water-Wet Rocks
Authors: Danesh Ali , Henderson G. D. , Peden J. M.
Published: December 2007

An experimental investigation of retrograde condensation in water-wet pores was conducted in micromodels and long cores to determine the critical condensate saturation and to evaluate the significance of interstitial water on condensate mobility. Although the interstitial water lowered the critical condensate saturation, it also could reduce the initial recovery rate by restricting condensate drainage.
Good Wells Make the Best Candidates for Well Stimulation
Authors: Jennings A. R.
Published: December 2007

When such factors as well response, return on stimulation costs, well cleanup, and sustained productivity are considered, it often becomes apparent that good wells are viable candidates for well stimulation. This paper discusses critical factors related to well-stimulation success, emphasizes that good wells possess the majority of these characteristics, and illustrates technical points with case histories.
Barium and Strontium Sulfate Solid-Solution Scale Formation at Elevated Temperatures
Authors: Todd A. C. , Yuan M. D.
Published: December 2007

Barium sulfate scale occurrence is a severe production problem in North Sea oil operations. Barium sulfate is often accompanied by strontium sulfate to form a completely mixed scale called (Ba, Sr)SO4 solid solution. This paper describes a laboratory study carried out at 70°C to examine (Ba, Sr)SO4 solid-solution scale formation in porous media and the formation damage resulting from the mixing of two incompatible waters. The paper is a continuation of the previously reported room-temperature work. Results of experiments carried out at the elevated temperatures again demonstrate that substantial scale deposition can occur in a rock core and can cause considerable decline of rock permeability as a result of concurrent flowing of two incompatible waters.
Effect of Wellbore Storage on the Analysis of Multiphase-Flow-Pressure Data
Authors: Hatzignatiou D. G. , Peres A. M. M. , Reynolds A. C.
Published: December 2007

This paper investigates the effect of wellbore storage on the analysis of pressure drawdown data obtained at a well producing a solution-gas-drive reservoir. Wellbore storage effects are incorporated by specifying a sandface oil flow rate that increases exponentially from zero to the specified constant value of the oil flow rate at the surface. Use of new computational equations derived here shows that effective oil permeability as a pointwise function of pressure can be computed directly from the measured values of the flowing wellbore pressure, provided the sandface oil flow rate is measured and incorporated into the analysis. If the sandface flow rate is unknown, effective permeability can be computed only after wellbore storage effects become negligible. In all cases, a semilog plot of wellbore pressure squared vs. time is shown to be a viable method for estimating effective oil permeability at initial conditions, effective oil permeability at the final flowing wellbore pressure value, and mechanical skin factor.
Cement Channeling: How to Predict and Prevent
Authors: Lockyear Christopher F. , Ryan Daniel F. , Gunningham Marcus M.
Published: December 2007

This paper describes experiments with a large-scale flow loop (45 ft of 7-in. pipe in nominal 8½-in. open hole) that measure the velocity of the interface between fluids of varying densities and rheologies. The work showed that single-fluid velocity profiles cannot be used to predict interfacial profiles (e.g., between spacer and cement) and confirmed the importance of turbulent flow in minimizing channeling through mechanisms of increased frictional pressure drop and mixing across the annulus. Large density differences, both negative and positive, also minimized channeling.
An Analysis of Miscible Flooding Chase-Fluid Strategies
Authors: Walsh M. P.
Published: December 2007

This paper presents a fractional-flow-theory analysis of miscible flooding chase-fluid strategies. Graphical solution methods to analyze flood performance for arbitrary solvent/water ratios, chase gas/water ratios (GWR's), and solvent slug sizes are presented. The graphical solution techniques include methods to predict the effects of wave interference, an important precursor to oil-bank destruction or loss in mobility control. An examination of interference leads to a deeper understanding of the miscible slug process. The advantages and disadvantages of chase-water, chase-gas, and simultaneous chase-gas/water injection are summarized. The analysis provides the theoretical basis for many chase-fluid design practices, including the idea of a minimum solvent slug size to ensure displacement integrity and the concept of an optimal chase GWR to minimize solvent requirements.
Why Cyclic Steam Predictive Models Get No Respect
Authors: Jones Jeff
Published: December 2007

This paper analyzes the reasons for the lack of wide acceptance of analytical cyclic-steam models. A reservoir-specific model is presented that provides excellent bistoiy-matehing results for a California heavy-oil project. Finally, several parameter-optimization projections that were carried to economic limit on a present-worth basis are presented.
Evaluation of Steam Resistance of Gravel-Packing Materials
Authors: Weaver J. D. , Knox J. A.
Published: December 2007

This paper compares the steam stability of common gravel-packing materials. The scope was limited to one set of down-hole conditions. Results indicated that none of the commonly used materials were entirely satisfactory, but another material not normally used in the petroleum industry was found to give excellent results.
Mathematical Simulation of Phase Behavior of Natural Multicomponent Systems at High Pressures With an Equation of State
Authors: Brusilovsky A. I.
Published: December 2007

This paper presents the new general cubic equation of state (EOS) for predicting phase and volumetric behavior of natural multicomponent systems under pressure and temperature conditions that conform to reservoir engineering processes. A new effective method to calculate the critical pressure of C5+ or C7+ fractions in reservoir fluids is presented. The method is of great importance for successful simulation at pressures greater than 25 MPa and can be used with any cubic EOS. The results of the mathematical simulation are described and the effects of porous media on phase behavior for natural multicomponent systems and of capillary pressure on dew- and bubblepoint parameters are investigated.
Miscible-Gasflood-lnduced Wettability Alteration: Experimental Observations and Oil Recovery Implications
Authors: Yeh S. W. , Ehrlich Robert , Emanuel A. S.
Published: December 2007

We present visual cell and coreflood data pertaining to the influence of water saturation on miscible gasflood residual oil (water blocking). In visual cell studies, we equilibrate miscible gases and oils at reservoir conditions with an intervening water phase. We find that the solvent-induced deposition of separated solids causes initially water-wet quartz surfaces to become oil-wet. A number of miscible coreflood displacements at high water saturation are considered, and the extent of water blocking is determined for Berea sandstone and reservoir cores.

Displacements of fluid systems with wettability alteration and those of refined oil systems without wettability alteration are reported. We find that water-blocking measurements with pure hydrocarbons overestimate miscible flood Sor regardless of the porous medium (Berea or reservoir sandstone or a reservoir carbonate) and the flood (CO2 or hydrocarbon miscible). We further find that water blocking is significantly more severe in Berea sandstone than in reservoir rock. We assert that water-blocking measurements with refined oil systems in Berea sandstone greatly overestimate water blocking in reservoirs, partially because refined oils cannot reproduce miscible-flood-induced wettability alteration.
Theoretical Study of Water Blocking in Miscible Flooding
Authors: Müller Thomas , Lake Larry W.
Published: December 2007

Miscible displacement processes can leave a substantial amount of residual oil behind the displacement front. This phenomenon has two general causes: instabilities caused by local heterogeneities or viscous fingering and water blocking. This paper describes a study of the latter. Numerous laboratory experiments have shown that significant blocking of oil from the solvent by mobile water can occur in water-wet media and at large water saturations. Despite this, water-blocking studies have been limited to either simple correction functions in numerical simulations or microscopic models. To the best of our knowledge, no explicit theoretical model considers the macroscopic bypassing and subsequent interaction of the solvent stream with a trapped hydrocarbon phase.

In this study, CO2 is the miscible solvent. A numerical model calculates the mass flux between flowing and stagnant regions separated by a water film. The model considers solvent diffusion and diffusional extraction of oil accompanied by swelling or shrinking of the stagnant hydrocarbon phase. The various process parameters are represented by a set of dimensionless numbers, which allow the problem to be scaled to any size. We show that the conditions for the mobilization of water-trapped oil are determined essentially by two numbers: the ratio of the stagnant water/oil volumes and the ratio of the solvent equilibrium constants at the phase boundaries. We apply the model to published laboratory miscible flood experiments. The water-film thickness is used as a matching parameter to reproduce closely the measured residual oil data for different flood velocities. Results indicate that solvent diffusion and oil swelling mechanisms effectively account for trapped oil on the laboratory scale. Trapping rapidly decreases at field scale if larger water barriers exist.
Significance of Quality Control of Liner-Wall Symmetry on Shaped-Charge Perforator Performance
Authors: Kececloglu Iflyenia
Published: December 2007

The objectives of this investigation were to demonstrate experimentally the significance of liner-wall mass uniformity and concentricity on the penetrating effectiveness (total target penetration and target hole size and symmetry) of conical shaped charges and to devise a systematic approach for selecting the optimum manufacturing conditions for the production of acceptably uniform shaped-charge liners. Experimental results indicated that total target penetration decreased with increasing liner-wall mass nonuniformity. Moreover, a statistical quality-control method was implemented to investigate systematically the variation in the symmetry of newly produced liners as a function of several manufacturing parameters, such as die vibration, die rotation, die pressing loads, and die dwelling/shaping times.
Empirical Correlations of Saturated Steam Properties
Authors: Chien Sze-Foo
Published: December 2007

Both steamdrive and steam stimulation processes for EOR involve thermodynamic and transport properties of steam. These properties have roles in the fluid flow, heat transfer, and mass and heat balances of recovery processes. Hence, they affect, not only the operation of the process, but also the economics and management of the oil recovery project. This paper presents empirical correlations of thermodynamic and transport properties of saturated steam in dimensionless forms as functions of either reduced temperature or reduced pressure. The pressure range of the correlations extends from atmospheric to 3, 000 psia [20.7 MPa]. The properties include saturation temperature, saturation pressure, specific volume, specific enthalpy, specific entropy, isobaric specific heat, dynamic viscosity, thermal conductivity, dielectric constant, surface tension, and isentropic expansion exponents. Compared with values listed in current steam tables, the calculated properties are accurate within ±0.02 % for saturation temperature and pressure, within ±0.12 % for thermodynamic properties, and within ±0.27% for transport properties.
Modeling Annular Flow Behavior for Gas Wells
Authors: Alves I. N. , Caetano E. F. , Minami Kazuloshl , Shoham Ovadla
Published: December 2007

A mechanistic model is developed for the prediction of annular two-phase flow behavior in gas wells. The model can predict annular flow characteristics, such as liquid film thickness, gas void fraction, and pressure gradient. It was evaluated against a data bank of 75 wells for which the pressure drop between the bottom of the well and the wellhead was available. The model was also compared with data from two wells with measured pressure profiles. Model predictions are in agreement with these data and superior to most commonly used correlations.
Hole Cleaning in Full-Scale Inclined Wellbores
Authors: Sifferman T. R. , Becker T. E.
Published: December 2007

A 4-year multifactor experimental study was completed recently on hole cleaning in inclined wellbores. Ten variables-annular mud velocity, mud density, mud rheology, mud type (oil- or water-based), cuttings size, rate of penetration (ROP), drillpipe rotary speed, drillpipe eccentricity, drillpipe diameter, and hole angle-were studied over a range of values. The full-scale annular test section was 60 ft [18.3 m] long, with 3- and 4.5-in. [76- and 114-mm] drillpipe in an 8-in. [203-mm] ID (wellbore diameter). Hole angle varied from 45 to 90° from vertical. Results frequently showed a large buildup of cuttings in the annulus, and cuttings were difficult to remove once a bed had built up on the low side of the wellbore. Cuttings-bed sliding also was more intense than anticipated. Mud velocity and mud density have the greatest effect on hole cleaning. Several two- and three-factor variable interactions also emerged from a subsequent statistical analysis.
The Use of Filtration Theory in Developing a Mechanism for Filter-Cake Deposition by Drilling Fluids in Laminar Flow
Authors: Flsk J. V. , Shaffer S. S. , Helmy Samy
Published: December 2007

This paper presents a mechanism for filter-cake deposition by drilling fluids in laminar flow. The mechanism evolved from analysis of filtration-data plots obtained from two linear equations derived from filtration theory. With these plots, various fluid-loss additives were evaluated on their ability to form a low-permeability filter cake that can be eroded by a fluid in laminar flow. The mechanism was tested on two wells with high torque and drag, and the static API high-temperature/high-pressure (HTHP) values were minimized.
NMR Imaging of Pore Structures in Limestones
Authors: Gleeson James W. , Woessner Donald E. , Jordan Clif F.
Published: December 2007

Nuclear-magnetic-resonance (NMR) imaging was used to examine pore structures and liquid flow paths in rocks nonde-structively. Various pore types were recognized in a spectrum of limestones, including growth-framework, moldic, vuggy, between-particle, and within-particle porosities. Pore connectivity was examined by fluid displacement and flow-weighted and 3D imaging.
Effect of Oxidation-Reduction Condition on Wettability Alteration
Authors: Wang Fred H. L. , Guidry Larry J.
Published: December 2007

This paper presents results of a laboratory study exploring the effect of the oxidation-reduction (redox) condition on crude-oil adsorption on rock mineral surfaces and consequent wettability alteration. Experiments were performed by aging Berea outcrop and Loudon reservoir sandstones with crude oil under various redox conditions and water saturations. Wettability alterations after aging were evaluated by the U.S. Bureau of Mines (USBM) method and by waterflood tests. The natural, oxidized Berea cores changed from strongly water-wet to mixed-wet conditions when aged at irreducible water saturation. Wettability alteration was greatly reduced when aging experiments were conducted under reduced conditions. The degree of wettability alteration depended on availability and redox state of iron on the mineral surfaces and also on aging time. We suggest two possible mechanisms to explain the role of iron in the wettability-alteration process. Wettability alteration in the water-wet Berea cores was insignificant when the cores were aged at residual oil saturation (ROS). Wettability alteration was also insignificant in the mixed-wettability Loudon reservoir cores, regardless of the water saturation or redox condition used in the aging experiments. We present the implications of these findings on core-handling procedures for wettability preservation.
Fractured Reservoir Characterization Through Injection, Falloff, and Flowback Tests
Authors: Peng C. P. , Singh P. K. , Halvorsen Hugo , York S. D.
Published: December 2007

This paper presents the development of a multiphase pressure-transient-analysis technique for naturally fractured reservoirs and the analysis of a series of field tests performed to evaluate the water injection potential and the reservoir characteristics of a naturally fractured reservoir. These included step-rate, water-injectivity, pressure-falloff, and flowback tests. Through these tests, a description of the reservoir was obtained.
The Design of Pulsed-Neutron Reservoir-Monitoring Programs
Authors: Kimminau S. J. , Plasek R. E.
Published: December 2007

The use of pulsed-neutron logs to infer fluid saturations behind casing in both stand-alone and time-lapse modes depends on the reproducibility of the intrinsic cross-section measurement. Experimental and field results from North Sea and North Slope fields show how imprecision and inaccuracy vary with conditions. A general design checklist is presented.
Impact of Flow-Unit Reservoir Description on Simulated Waterflood Performance
Authors: Silseth J. K. , MacDonald A. C. , Alvestad Jostein , Buller A. T. , Torp S. B.
Published: December 2007

The impact on simulated waterflood performance of adopting a "discrete" and simplified flow-unit representation of reservoir heterogeneity, rather than a conventional "smooth" model based on contouring of petrophysical zonal averages, was assessed with a synthetic model of a heterogeneous barrier-bar sand body. On the basis of comparative simulations, the contour models did not generate consistently optimistic predictions of reservoir performance (compared with their flow-unit counterparts). Individual well behavior, however, varied significantly according to model type.
Modeling Forces on a Beam-Pump System During Pumping of Highly Viscous Crude
Authors: Lea J. F.
Published: December 2007

In previous dynamic predictive models of beam-pump performance, drag forces on the rod string commonly are modeled by an input empirical drag coefficient multiplying the local rod velocity. This paper shows how forces on the rods and pump plunger can be modeled theoretically and calculated for viscous flow. Results of viscous-flow calculations to develop drag coefficients compare well with measured field data.
Normalization of Nitrogen-Loaded Gas-Lift Valve Performance Data
Authors: Nieberding M. A. , Schmidt Zelimlr , Blais R. N. , Doty D. R.
Published: December 2007

The flow performance of two nitrogen-loaded gas-lift valves and one combination gas-lift valve was tested under simulated downhole conditions. Set pressures up to 1, 500 psig and injection pressures up to 1, 650 psig yielded a maximum observed gas flow rate of 3.6 MMscf/D. Pressure-operated valve performance depends on injection pressure for specific production and dome pressures, valve geometry, and other factors. Two performance characteristics, separated by the test-rack opening pressure, are observed: throttling and orifice flows. Semimechanistic models predict throttling and orifice flow performance. Experimental performance characteristics tune the model for any port size used in the Camco R-20 valve.
Flow-Related Corrosion in Large-Diameter Multiphase Flowlines
Authors: Green A. S. , Johnson B. V. , Choi H. J.
Published: December 2007

A strong relationship between field measurements of flow regime and corrosion rate has been found. In multiphase flow, the slug flow regime produces high liquid velocities and high inherent turbulence levels for significant periods. The exact mechanism for removing a corrosion-inhibitor film from a pipe wall or preventing the film from forming remains unclear, but high turbulence and wall shear stresses always are present when flow-related corrosion occurs. The levels of wall shear stress may be estimated for a variety of pipeline features when subject to a passing slug. This provides a basis for realistic corrosion-inhibitor trials in the laboratory and a means of relating this information to field conditions. The onset of slug flow may be predicted to identify those times when a flowline may be especially at risk.
History Match of Multiwell Simulation Models of the Cyclic Steam Stimulation Process at Cold Lake
Authors: Boberg T. C. , Rotter M. B. , Stark S. D.
Published: December 2007

Various simulation model elements were examined in an effort to match observed behavior of a selected steam stimulation well at Cold Lake. The best match required a large model encompassing eight wells, but a three-well model provided an adequate match. Well location, fracture angle, and geology must be represented accurately.
A Superposition Method for Representing Wellbore Crossflow in Reservoir Simulation
Authors: Modine A. D. , Coats K. H. , Wells M. W.
Published: December 2007

Production from highly stratified reservoirs can result in significant crossflow between layers through wellbores. This paper describes a new, relatively simple superposition method to represent this, crossflow in a numerical simulator. The method calculates vertical wellbore saturation variations throughout the wellbore and gives more accurate results than a fully mixed wellbore method. Equations are given for the new method, a fully mixed wellbore method, and the exact solution for crossflow in a well completed in a column of gridblocks. Three examples, including a field-scale depletion, are given comparing exact results with those from the superposition and fully mixed wellbore methods.
Theory, History, and Results of Sealants for Subsea Service
Authors: Pennell R. G. , Baugh B. F.
Published: December 2007

This paper discusses the theories of repair sealants on ball valves and testing done on various sealants to determine their basic characteristics. Preliminary penetration, chemical, and flow testing results are presented, along with a discussion of field problems.
Cooperative Research—A Route To Reduce the Environmental Impact of Drilling Fluids
Authors: Oakley D. J. , Morrison A. , Burdis I. , Jones K. G.
Published: December 2007

Increasing environmental constraints on use of oil-based drilling fluids have fluids have prompted close cooperation between operators and service companies to maintain the technical performance of drilling fluids while reducing oil discharge. This paper describes how Amerada Hess Ltd. (AHL) and Intl. Drilling Fluids Ltd. (IDF) cooperated by extending laboratory developments into controlled field trials and how feedback from the field has allowed rapid progress toward performance and ecological goals. We achieved progress toward performance and ecological goals. We achieved success through two developments. First, as a result of a jointly funded research project, we developed a novel, oil-free, highly inhibitive water-based drilling fluid. The inhibition offered by this fluid approaches that offered by oil-based fluids. Second, we developed invert-emulsion and direct-emulsion fluids with low oil/water ratios for low oil-on-cuttings applications. The cooperative process improved the technical performance of these fluids demonstrably and reduced the oil on cuttings.
Internal Blowouts, Cratering, Casing Setting Depths, and the Location of Subsurface Safety Valves
Authors: Walters J. V.
Published: December 2007

This paper promotes industry awareness of the potential mechanisms that may take place in the rare event of a loss of well control and how these mechanisms may be assessed for field-specific conditions. This is particularly important when exploration/appraisal drilling involves penetrating highly overpressured accumulations. Depending on the geological burial history, these overpressures may be located in extremely competent or weakly consolidated formations, even at great depth. In-situ stress and rock-strength characteristics will play a major role with respect to the chances of reaching these target horizons successfully.
Automatic Grid Generation for Modeling Reservoir Heterogeneities
Authors: Garcia Michel H. , Journel André G. , Aziz Khalid
Published: December 2007

An automatic grid-generation and -adjustment method is proposed to produce grids that may be used for finite-difference simulators. The resulting blocks are as homogeneous as possible with respect to specified parameters (e.g., porosity and permeability). Creating a grid of homogeneous blocks is desirable in flow simulation studies because it allows easier evaluation of the block average (effective) properties.
Investigation of Stress-Induced Borehole Enlargement Mechanisms by a Liquid-Metal Saturation Technique
Authors: Ewy Russell T. , Myer Larry R. , Cook Neville G. W.
Published: December 2007

Stress-induced borehole enlargement was investigated with thick-walled hollow rock cylinders and a liquid-metal sample-preservation technique that permits observation of the microstructure of the broken rock. The observed breakouts are oriented and occur on the two opposite sides of the hole with the highest compressive-stress/compressive-strength ratio. Triangular (dog-eared) breakouts result from progressive spalling of thin rock slabs. The fundamental mechanism leading to this failure is the growth and interaction of microscopic cracks oriented parallel to the hole wall. Overbalance pressure in the hole changes this failure mechanism and greatly strengthens and stabilizes the hole wall. The apparent rock strength observed next to these small laboratory-scale model holes is higher than expected for field-scale holes.
Distribution of Residual Oil in Heterogeneous Carbonate Cores Using X-Ray CT
Authors: Hicks Paul J. , Deans Harry A. , Narayanan K. Ram
Published: December 2007

The use of X-ray computerized tomography (CT) for the measurement of residual saturations and porosity distributions in heterogeneous carbonate cores is illustrated. Semivariograms of porosity are calculated and used to determine correlatiort lengths on the laboratory scale. The relationship between residual saturation and porosity is presented for two different cores.
Breaker Concentrations Required To Improve the Permeability of Proppant Packs Damaged by Concentrated Linear and Borate-Crosslinked Fracturing Fluids
Authors: Brannon H. D. , Pulsinelli R. J.
Published: December 2007

The concentrations of an oxidative breaker required to reduce significantly the proppant-pack permeability damage caused by aqueous hydraulic fracturing fluids have been determined. Long-term, proppant-pack permeability testing was used to evaluate linear • and borate-crosslinked gels. Results indicate that increasing the breaker concentration can reduce proppant-pack permeability damage very effectively.
North Vickers East Waterflood Performance Prediction With Fractal Geostatistics
Authors: Di Julio Shoeleh S.
Published: December 2007

A detailed geostatistical cross section, combined with a fine-grid streamtube calculation was used to predict the improvements of the North Vickers East waterflood project in Inglewood, CA. The intent was to test the hybrid finite-difference/streamtube technique (HST) to predict workover and realignment in a complex reservoir that was not easily modeled by conventional methods. Results indicate that HST may offer a method to represent the performance of such reservoirs without conventional history matching.
Incorporating Reservoir Heterogeneity With Geostatistics To Investigate Waterflood Recoveries
Authors: Wolcott Don S. , Chopra Anil K.
Published: December 2007

This paper presents an investigation of infill drilling performance and reservoir continuity with geostatistics and a reservoir simulator. The geostatistical technique provides many possible realizations and realistic descriptions of reservoir heterogeneity. Correlation between recovery efficiency and thickness of individual sand subunits is shown. Additional recovery from infill drilling results from thin, discontinuous subunits. The technique may be applied to variations in continuity for other sandstone reservoirs.
The Use of Low-Density Particles for Gravel Packing a Highly Deviated Well
Authors: Bryant David , Hudson T. E. , Hoover S. W.
Published: December 2007

Packing the annulus and perforations with gravel in highly deviated wells, especially horizontal wells, is difficult. As well deviation increases, pump rates and carrier-fluid viscosities must be increased to prevent particle settling. Increasing the viscosity reduces fluid leakoff and performation-pack efficiency. Placement efficiency improves as particle density, ρp, and carrier-fluid density, ρc, become closer. In an ideal system, these densities would be equal, ρp/ρc= 1, and no viscosity would be required, thereby improving fluid leakoff and perforation packing. Using sand as the packing material causes perforation packing. Using sand as the packing material causes hydrostatic overbalance, thus limiting the application of this system. The use of this technique with a pack material having a density of 40% less than that of sand eliminates the overbalance. This paper provides technology applicable to gravel packing highly deviated provides technology applicable to gravel packing highly deviated (horizontal) wells and describes (1) a new method for completing highly deviated wells with low-density particles (LDP's) and low ρpρc ratios, (2) computer simulations used to aid in the design of completion techniques, (3) printouts of the screenout pressure and pump rates, (4) well design schematics, (5) pack logs, pressure and pump rates, (4) well design schematics, (5) pack logs, and (6) well performance data.
Acoustic Logging Based on Wellbore Resonance
Authors: Medlin W. L. , Schmitt D. P.
Published: December 2007

Wellbore resonance phenomena are the basis for a new acoustic logging method, the Stimulated Mode Acoustic Log (SMAL). The SMAL method stimulates a particular mode of wellbore vibration by exciting a resonance for that mode. Specific resonances are excited by driving an acoustic transmitter with a short tone burst of appropriate frequency. SMAL benefits include signal enhancement under adverse conditions, avoiding dispersion effects, propagating formation waves through cased and slotted liner completions, generating steady-state phase and amplitude data, and providing formation Q logs. All of these applications have arisen from studies of wellbore resonance phenomena through well logging and laboratory experiments. One means of study has been the wellbore excitation log, which shows the foot-by foot response of the wellbore to swept-frequency excitation across the acoustic band. Excitation logs show that resonances are sensitive to lithology and formation saturation conditions. Additional insight has been provided by generating standing waves under resonance conditions. This approach has led to a means of estimating a formation Q from the decay of standing tube waves. Q data, generated in this way, are consistent with laboratory data for core and quarry samples. A Q log, run through the gas, oil, and water legs of a thick Gulf Coast sand, is consistent with lab data for cores. Laboratory experiments in thick-wall pipe models have been another means of study. These field and laboratory investigations indicate that the combination of wellbore and logging tool behave somewhat like a resonance cavity for pressure waves in the wellbore fluid. Tool elements, especially the two ends, act as reflectors of fluid wave energy, giving rise to resonances and standing wave phenomena. The resonance characteristics of this cavity are dominated by the properties of the formation wall material and the coupling between the fluid and borehole wall. Other factors, such as fluid column and source resonances, play secondary roles. It is the strong dependence of resonances on formation properties that makes SMAL a valuable logging concept.
Nonplanar Fracture Propagation From a Horizontal Wellbore: Experimental Study
Authors: Abass H. H. , Hedayati Saeed , Meadows D. L.
Published: December 2007

This paper presents experimental results related to hydraulic fracturing of a horizontal well, specifically the nonplanar fracture geometries resulting from fracture initiation and propagation. Experiments were designed to investigate nonplanar fracture geometries. This paper discusses how these nonplanar fractures can be responsible for premature screenout and excessive treatment pressure when a horizontal well is hydraulically fractured. Reasons for unsuccessful hydraulic fracturing treatments of a horizontal well are presented and recommendations to ensure clear communication channels between the wellbore and the fracture are given.
Advances in Characterizing Natural-Fracture Permeability From Mud-Log Data
Authors: Dyke C. G. , Wu Bailin , Milton-Tayler David
Published: December 2007

Small drilling-fluid losses provide an accurate means of detecting conductive natural fractures and pinpointing potentially productive zones. We outline improved interpretation techniques that allow losses as small as 0.5 bbl to be used reliably as fracture permeability indicators. We compare results from four case histories with conventional fracture-detection methods.
Precipitation and Dissolution of Calcium Phosphonates for the Enhancement of Squeeze Lifetimes
Authors: Browning F. H. , Fogler H. S.
Published: December 2007

Injection of scale inhibitors into a formation is a commonly used technique to prevent scale formation during oil production. The success of a "squeeze treatment" often is determined by its effective lifetime in inhibiting scale in a reservoir system, and this lifetime is dictated by the retention/release mechanisms of inhibitor in the reservoir. This paper focuses on a study of the precipitation/dissolution of calcium 1-hydroxyethylidene-l, 1-diphosphonic acid (HEDP)in a porous medium to elucidate the important factors that affect the release of this precipitate.

Experiments carried out in ceramic cores indicate that precipitation squeezes offer longer squeeze lifetimes and more HEDP retention than adsorption squeezes. Micromodel experiments show that the calcium-HEDP precipitate placed in porous media is made up of long, fibrous particles preferentially situated in pore throats. The elution from micromodels indicates that slow dissolution of apparently strong pore-throat plugs dictates the long tailing region. Finally, multiple-shut-in experiments performed in ceramic cores show that, while the amount of calcium-HEDP retention per shut-in does not increase with successive shut-ins, an enhanced returns effect is observed with respect to the squeeze lifetime.
Perturbation Boundary Element Method for Heterogeneous Reservoirs: Part 1—Steady-State Flow Problems
Authors: Sato Kozo , Horne Roland N.
Published: December 2007

A perturbation boundary element method (BEM) for steady-state flow problems in heterogeneous media is developed, and various aspects of the model are tested. The perturbation series obtained by the BEM gives the complete solution for the original governing equation. For highly heterogeneous problems. Padè approximants are effective to accelerate the rate of convergence and to convert a divergent series into a convergent solution. Because the model does not suffer from numerical dispersion and grid orientation effects, it is possible to track streamlines accurately.