bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Laboratory and Field Testing to Identify Potential Production Problems in the Troll Field
Authors: Hartley R. , Jadid M. Bin
Published: December 2007

The areal extent of the oil found in Troll made it clear at a very early stage in the field's appraisal that subsea wells would be required if the oil were developed. Owing to cooling in the subsea flowline, subsea wells can be expected to pose more production chemistry problems than would be expected with conventional platform wells. Consequently, a number of laboratory tests were carried out during the appraisal campaign to identify problems to be expected with scaling, foaming, emulsification, wax deposition, and hydrates. Dehydration and wax deposition tests were also carried out offshore during appraisal-well testing. These tests are described, together with the methods subsequently adopted to minimize future production problems.
Beckingham 36 Horizontal Well
Authors: Hardman P.
Published: December 2007

BP Petroleum Development Ltd. successfully drilled and completed the first horizontal well in the United Kingdom as part of its 1985 R&D program. The well, Beckingham 36 (BK 36), was drilled on an existing land field near Gainsborough, U.K. This paper discusses the detailed planning for and the execution of the drilling operation. Conclusions and recommendations are presented for future wells.
Water Content of CO2 in Equilibrium With Liquid Water and/or Hydrates
Authors: Song Kyoo Y. , Kobayashi Riki
Published: December 2007

Experimentally measured water content in CO2-rich fluid in the gaseous or liquid state in equilibrium with liquid water or hydrate is presented for pressures ranging from 100 to 2,000 psia [0.69 to 13.79 MPa] and temperatures from −19 to 77°F [−28.33 to 25.0°C]. The water content of the CO2-rich phase along the three-phase equilibria, i.e., liquid water/liquid CO2/gas to the three-phase critical endpoint, is also reported. The experimental results from this study on the water content in the CO2-rich phases have been combined with earlier research results of the CO2/water binary system in the hydrate-free region from 77 to 200°F [25.0 to 93.33°C] and pressures to 3,000 psia [20.69 MPa] to produce a comprehensive plot.

The high degree of complexity in the phase behavior of a CO2/water binary system, which exhibits several pairs of equilibrium phases for the conditions, is shown. To make the data more intelligible than they are in their raw form, the data are presented in terms of the pressure enhancement of the water content along isotherms. Finally, the activity coefficients of water in the CO2-rich phases are summarized.
A Simple Buildup Analysis Method To Determine Well Drainage Area and Drawdown Pressure for a Stabilized Well
Authors: Bossie-Codreanu D.
Published: December 2007

This paper presents a new method that applies to wells that are shut in after having reached pseudosteady-state flow conditions. Based on the complete Miller-Dyes-Hutchinson (MDH) equation, a corrected pressure is defined that allows extension of the semilog straight line by about two log cycles for symmetric systems and one-half log cycle for others. The drainage area is directly computed. If the final recorded shut-in pressures depart from the straight line, it is also possible to compute the shape factor and the average pressure independently of the initial pressure.
Hydrocarbon Saturation Equation in Shaly Sands According to the S-B Conductivity Model
Authors: Silva Pedro L. , Bassiouni Zaki
Published: December 2007

The Silva-Bassiouni (S-B) conductivity model is used to derive a water-saturation equation for hydrocarbon-bearing shaly sands. The performance of the equation is evaluated by comparing calculated and experimental Sw values obtained at 25°C [77°F]. The comparison proved the equation to be valid and accurate.

Several saturation-exponent determination procedures are presented and evaluated. These methods require laboratory core measurements. In the absence of such data, the use of a generalized value of two is supported by statistical analysis.

In its present form, the S-B model can be used in the analysis of laboratory measurements, especially in the determination of the saturation exponent, n, of shaly sands. It is believed that further extension of the S-B model will provide means of saturation determination from log data. This possibility is currently being explored.
Selecting a Perforating System
Authors: King George E.
Published: December 2007

The purpose of a perforator is to create in the casing a hole that extends into the formation to allow the efficient production or injection of fluids. This entrance hole may be made by any of three methods.

Shaped-Charge Perforating

The most common method of perforating is shaped-charge or "jet" perforating. The shaped charge-an outgrowth of the World War II bazooka-is available in several sizes and types for various perforating applications. It has four principal components (Fig. 1): the outer case, the primer, the powder, and the metal liner. When the charge is fired, the pressure from the exploding powder deforms the metal liner. The shape of the charge, which is dictated by the case and the liner, focuses the energy in a single direction. The pressure and the now-fluid liner form a "jet" that can punch a hole through the casing and into the formation. The time from initiation to completion of the jet is about 0.1 ms and pressures up to 4 million psi [27.6 GPa] drive the tip of the jet at speeds of roughly 30,000 ft/sec [9144 m/s]. The jet penetrates the formation to depths of from about 3 to 18 in. [7.6 to 46 cm], depending on the type and shape of the metal liner, the characteristics of the formation, and, to a lesser extent, the weight of the explosive.

The charges may be held in any of three types of guns: casing guns, expendable guns, and through-tubing guns. The casing gun, which may be run on wireline or conveyed by tubing, is available in diameters from 1 3/8 through 7 in. [3.5 through 17.8 cm]. The charges are contained within the gun (Fig. 2), protected from impact damage and from the well fluids. In the larger guns, they range from 1 to 16 shots/ft [3 to 52 shots/m]; in the smaller guns, from 1 to 4 shots/ft [3 to 13 shots/m]. The charges are aligned by sleeves, rubber pop-up caps, or in metal strip holders in the guns. The positioning is necessary to let the charge penetrate the special thin sections of the guns. Reusable guns use screw ports or port plugs with a center thickness of 0.1 in. [0.254 cm]. This thin section of the port plug is much easier to penetrate than the 0.5- to 0.68-in. [1.27- to 1.727-cm] gun wall thickness. The single-use or "retrievable expendable" scallop guns have the gun body section over the charge locations milled to about 0.1 in. [0.254 cm] thick. The jet punches a hole through the port plug or scallop and into the casing, cement, and formation. The perforation penetration is sharply reduced if the charge is misaligned and shoots through the body of the gun. Casing damage from perforating with even the high-density guns is relatively minimal if the casing is backed up with cement (Fig. 3).

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The Apparent Viscosity of Foams in Homogeneous Bead Packs
Authors: Falls A. H. , Musters J. J. , Ratulowski J.
Published: December 2007

The mobilities of aqueous foams of known texture have been measured in homogeneous bead packs. To correlate the data, a theory developed recently to describe the apparent viscosity of foams in smooth capillaries is extended to account for (1) the capillary pressure imposed by the porous medium and (2) constricted flow paths. In porous media, apparent gas viscosity depends strongly on foam-bubble size; for large bubble sizes, it is proportional to the third power of the ratio of the hydraulic radius of the pack to the bubble radius. Foams of uniform texture are pseudoplastic. At low shear rates, the viscosity varies inversely with a capillary number; at higher rates, it depends on the capillary number to the - ⅓ power when the bubble size is large compared with the pore size and on the - ⅔ power of capillary number when the bubble size is smaller.
Top-Drive Drilling System Evaluation
Authors: Cavanaugh James M. , Adams David M.
Published: December 2007

Since drilling began, the industry has continuously strived to improve rotating and handling of drillpipe. With these improvements, on-bottom rotating time has been reduced to 25 to 30% of total well time, which has proved acceptable for the U.S. gulf coast. Attention is now being focused on nonrotating time, and with the introduction of the top-drive system, this time can be reduced primarily through pipe handling. Three wells were drilled from a platform in Mustang Island, offshore Texas, and the top-drive drilling system was used and tracked for time savings vs. a typical kelly/rotary system. It has been reported that as much as 20 to 25% time savings can be obtained with the top drive. Definite time savings can be expected with the top-drive drilling system, but the magnitude reported was not experienced on the three wells discussed here. It was established that roughly 6% of drilling cost or 4% of total well cost could be saved with the top drive, which represents 11 % of drilling time or 8% of total well time.
Onboard System Provides Stability, Mooring, and Motion Analysis for Semisubmersible Drilling Operations
Authors: Foreman Russell D. , Beynet P. A. , Singhal S. N. , Seidl L. H.
Published: December 2007

Vessel stability, mooring, and motion-related decisions on semisubmersible drillships have historically been made with a combination of the marine crew's experience and guidelines documented in the ship's operating manual. This is especially true once the vessel is on location and operations are under way. This situation leaves the operator dependent on contractors to anticipate problems and to take correct remedial action.

This paper presents a computer system that combines state-of-the-art marine technology with a simple user interface to provide information useful to operations personnel in making decisions. The purpose of the system is not to take over any of the contractors' responsibilities. It does provide additional information useful in making marine-related decisions. This allows the contractor and the operator to combine experience and analysis and work toward a mutual decision.

This tool, referred to as the "Onboard System," was used by drilling personnel on two semisubmersibles in the Bering Sea. In addition to stability, mooring, and motion capabilities, the Onboard System provides a data base of environmental information and corresponding vessel responses while on location.
Operational Aspects of Extended High-Pressure Well Tests from a Floater
Authors: Roberts E. W.
Published: December 2007

During Summer 1985, an extended high-pressure gas-condensate well test was conducted from a semisubmersible drilling unit in Block 29/5a. This paper is a case history discussing the planning and implementation of the production-test operation.

The Well 29/5a-3 production test is believed to have been the most extensive high-pressure test conducted in the U.K. North Sea from a floating drilling unit. In the past, because of equipment and/or environmental constraints, high-pressure testing has been limited to short flow and buildup periods. Also, the majority of "expected" high-pressure tests conducted with 15,000-psi [103-MPa] equipment either have rapidly depleted (high-pressure, low-volume zone) or have been terminated prematurely because of mechanical problems. In contrast, the Well 29/5a-3 production test experienced no major equipment failures. In addition, surface pressure readout gauges were successfully installed under extreme pressure and temperature conditions.

Proper operational planning and equipment selection proved vital in implementing the production test and achieving the main objectives.
Evaluating Drilling Practice in Deviated Wells With Torque and Weight Data
Authors: Lesage M. , Falconer I. G. , Wick C. J.
Published: December 2007

This paper shows how to estimate two friction coefficients on a foot-by-foot basis at the wellsite with both measurement-while-drilling (MWD) and surface values of weight on bit (WOB) and torque. A log of the coefficients with depth can be used to diagnose drilling problems in directional wells. Field examples are given that show how the technique detects incipient sticking and hanging stabilizers. Data are also used to evaluate the time spent on wiper trips and in circulating before making connections.
Prediction of Wellbore Trajectory Considering Bottomhole Assembly and Drill-Bit Dynamics
Authors: Brakel J. D. , Azar J. J.
Published: December 2007

This paper presents a numerical dynamic model to predict wellbore trajectory in both the vertical and horizontal planes. The model is three-dimensional (3D) and consists of the idealization of the bottomhole assembly (BHA) into a number of finite elements. Inertia properties are included to predict the transient dynamic behavior of the assembly during drilling. To ensure the correct boundary condition at the bit/rock interface, two rock/bit interaction models, one for a roller-cone bit and one for a polycrystalline-diamond-compact (PDC) bit, are developed. The time average of the rock/bit interaction force components is used to obtain an indication about the directional tendencies of the BHA. Examples of the rock/bit interaction forces for roller-cone and PDC bits and examples of the motion of a holding assembly for both bit types are given. The effects of hole inclination, weight on bit (WOB), rotary speed, and bit/stabilizer clearance are presented for an example of a building, holding, and dropping assembly. The deviation tendencies, as predicted by the model for several building and holding assemblies, are compared with field case data.
The Effect of Vertical Fractures on Well Productivity
Authors: McGuire W.J. , Sikora V.J.
Published: December 2007

Introduction

Several years ago, we used an electric analogue computer to study the effect of vertical fractures on the productivity of wells in expanding fluid-drive reservoirs. The results of this work were used both as a guide to research and as a basis for the design of actual fracturing operations. In 1958, Dyes, Kemp and Caudle published portions of the data from this study. The results were released in 1959 to service companies for use in fracturing guides.

The purpose of this note is to discuss the experimental conditions and assumptions which were made to derive the information which is already partially a matter of public record.

Assumptions

This study applies to fractures which extend in a vertical plane symmetrically from the well. For simplicity, we chose to study the case of a well in a square drainage area with its fractures extending toward two of its nearest neighbors. We have assumed no migration of fluid across the boundary of this area. The quadrant shown in Fig. 1 models this system.

We made the usual assumptions that the reservoir is homogeneous and isotropic, that the fluid is homogeneous and that production is effected by fluid-expansion drive. We also assumed that the fracture extends from top to bottom of the reservoir.

Of more practical interest is our assumption that the fracture does not change the size of the drainage area. This premise is appropriate if all the wells in the reservoir are fractured in the same way. But where a single well is fractured, its drainage area may be enlarged at the expense of its neighbors. This could be of economic importance. The assumption that the fracture will not extend beyond the established drainage area of the well also limits the application of the results. Such long fractures will yield benefits in excess of those predicted here.

When we assume homogeneity, we disregard the frequently observed zone of damage in the vicinity of the well. Where damage is severe, the benefits resulting from by-passing it will far exceed those predicted by this study. All comparisons were made of systems producing in the semi-steady state. By this we mean that equal volumes contributed equally to flow (pressure was dropping at a uniform rate throughout the system) when the rate of flow was observed.
Safe Purging of Natural Gas Pipelines
Authors: Perkins T. K. , Euchner J. A.
Published: December 2007

When a newly constructed natural gas pipeline is put into service, it can be safely purged of air by injection of a slug of inert gas, such as N2. The method of sizing the required slug is based on a model of dispersion in turbulent flow in conjunction with flammability limits.
Analysis of Electric-Submersible-Pumping Systems
Authors: Nolen K. B. , Glbbs S. G.
Published: December 2007

This paper presents a field-proven analytical method of evaluating electric-submersible-pumping equipment and well performance jointly. A computerized mathematical model that considers the effects of free gas, pump speed (variable-frequency drives), and pump tapering is described. The method allows accurate calculations of important downhole parameters, including pump intake pressure, pump intake volume (including free gas), pump pressure, and fluid density profile. Lifting cost parameters—such as pump and motor power requirements, monthly power consumption, pump and motor performance, and overall system efficiency—are also determined. Once operating conditions are known, decisions can be made on ways to increase production (if additional potential exists) or to reduce operating costs. Thus, the same basic goals that often justify frequent analysis of rod-pumping systems can be applied to submersible pumping.
Porous-Media Momentum Equation for Highly Accelerated Flow
Authors: Blick E. F. , Civan F.
Published: December 2007

A new porous-media momentum (capillary-orifice model) equation has been developed to account for unsteady flow through porous media. The equation contains not only the familiar permeability and non-Darcy factor terms but also momentum flux and acceleration terms. An analysis of the order of magnitude of these terms indicates when they are important.
Thermodynamic Analysis of Transient Two-Phase Flow in Petroleum Reservoirs
Authors: Tlab Djebbar , Duruewuru Anthony U.
Published: December 2007

This paper presents a new method of analyzing the performance of a flowing well. The method uses a thermodynamic property known as the "availability function." The advantage of the availability-function method of analysis is that it allows the calculation of the thermodynamic efficiency of all processes, including not only those that are large work producers or consumers but also those that do not have work production or consumption as their goal. The efficiency of a process indicates how closely the process reaches its ultimate performance. It can be used as a tool to compare various processes and to make a sound decision on where improvements are possible.

The model developed in this study is capable of handling a single-component, single-phase or two-phase flow. The fluid-flow equations provide the thermodynamic properties—energy, enthalpy, entropy, and the fluid velocity—for use in the calculations of the theoretical maximum reversible work, the useful energy used to lift the hydrocarbon fluid from the bottom of the well to the surface, and the energy lost because of irreversibilities.

Results obtained from this study show that (1) a considerable fraction of the fluid energy is lost because of irreversibilities, especially at the early stages of production, and (2) the thermodynamic efficiency of fluid production would be greatly improved by minimizing wellbore heat loss.
Characterization and Control of Formation Damage During Waterflooding of a High-Clay-Content Reservoir
Authors: Leone Joseph A. , Scott E. Mark
Published: December 2007

Permeability damage was suspected as a factor contributing to postcompletion production declines observed during waterflooding of a friable to unconsolidated sandstone. A loss in water injectivity also indicated that near-wellbore damage may have been occurring. This paper summarizes the laboratory studies undertaken to evaluate and understand permeability damage in this formation. The experimental program consisted of primarily coreflooding experiments to evaluate the influence of injection fluid composition, temperature, mineralogy, and flow velocity on permeability damage. The significance of damage during brine injection was observed to be a strong function of mineralogy and injection rate. Permeability losses of > 60% were observed in cores from some sand intervals, while little or no damage was apparent in cores from a second zone in identical wells. In the sands that were susceptible to brine damage, a critical velocity below which permeability damage did not occur was repeatedly established. The occurrence of a critical velocity, along with other observations, indicated that the primary damage mechanism was fines migration. Damage could be controlled by maintaining velocities below the critical value or reducing the pH of the injected brine.
Settling Velocity of Variously Shaped Particles in Drilling and Fracturing Fluids
Authors: Peden James M. , Luo Yuejin
Published: December 2007

The settling velocities of a variety of shaped particles to simulate drilled cuttings were measured in both Newtonian and non-Newtonian fluids. The results showed that the particle drag coefficient is a function of the particle Reynolds number and, in the case of power-law-model fluids, of the flow behavior index. A new generalized model has been developed for predicting the settling velocities of particles of various shapes in both Newtonian and power-law fluids over a range of flow regimes.
Thermal Cracking of Heavy-Oil/ Mineral Matrix Systems
Authors: Monin J. C. , Audibert A.
Published: December 2007

At temperatures and pressures encountered during thermal recovery, chemical reactions involving oil, possibly water, and mineral matrix may lead to significant changes in composition of the phases. This work focuses on thermal alteration of four crude oils with different geochemical compositions. The tests were performed in an autoclave at 350°C [660°F] for 200 hours. The oil was in the presence of water and a mineral matrix representative of reservoir rocks.

The formation of significant amounts of insoluble organic material was observed in all tests. Gaseous hydrocarbons (mainly methane) formed by pyrolysis. CO2 evolution depended on oil and matrix compositions; moreover, water was found to be a reactant in the formation of oxygen-containing components.

For crude oils investigated, the oil phase was significantly enriched in lighter hydrocarbons (mainly in saturates). However, aromatic content was less affected by the thermal treatment. On the other hand, asphaltenes and, to a lesser extent, resins were the main precursors of insoluble material. These results provide new insight on mechanisms of the cracking reactions involved in thermal recovery processes.
Role of Silicate and Aluminate Ions in the Reaction of Sodium Hydroxide With Reservoir Minerals
Authors: Thornton S. D.
Published: December 2007

A chemical model is presented for extrapolating laboratory data on mineral/alkali reactions to reservoir time scales. Minerals in sandstone and ions in caustic solution that control sodium hydroxide consumption during alkaline flooding were identified. This work may help operators predict when significant dissolution of the formation will occur and where precipitates will deposit.

The dissolution of eight silicate minerals in caustic solution at 24 and 70°C [75 and 158°F] was determined. The minerals studied were quartz, two feldspars (microcline and albite), two micas (muscovite and biotite), and three clays (kaolinite, montmorillonite, and chlorite). The concentrations of sodium, silicate, aluminate, and hydroxide were measured periodically during bottle tests. Balanced chemical reactions are written for quartz, kaolinite, and phillipsite, and the corresponding equilibrium quotients are defined. A kinetic model is presented that includes rate constants, solid/liquid ratios, and equilibrium quotients to account for the effect of solution composition. The model was tested for kaolinite. The equilibrium quotient for kaolinite was found to be three times higher at 70°C [158°F] than at 24°C [75°F]. Dissolution-rate data were fitted successfully with the kinetic model.

The reaction of Kern River reservoir sand with sodium hydroxide was studied to test the model. Consumption of sodium hydroxide occurred as predicted. However, caustic consumption was delayed in a slim tube packed with 99% quartz and 1% kaolinite, probably because of reduced nucleation of new minerals.
Pipeline-Life Assessment Based on a Leak-Growth Model
Authors: Hansen D. A. , Boah J. K. , Shelkh A. K.
Published: December 2007

An empirical model is used to forecast the frequency of pipeline leaks and to assess pipeline failure rate. The model, which is based on a simple exponential-growth relationship, predicts the cumulative number of leaks, n, as a function of time: n = A exp(mt), where A and m are empirical constants. The model is applicable to essentially all carbon-steel pipelines exposed to serious corrosion attack, either internal or external. The model is useful in evaluating the technical and capital alternatives in pipeline design, operation, and maintenance.
Mechanisms of Residual Oil Displacement by Steam Injection
Authors: Stewart L. D. , Udell K. S.
Published: December 2007

In an attempt to isolate various thermal and hydrodynamic mechanisms, a model of one-dimensional (1D) steam displacement of residual oil has been developed. The quasisteady model considers capillary pressure gradients and gravity forces during the simultaneous flow of oil, water, and steam to be the dominant factors in oil-bank mobilization. It was shown that under most conditions, the Buckley-Leverett displacement velocity is significantly faster than the steam-condensation-front velocity. This feature dictates the use of the steam-condensation-front velocity as the characteristic velocity in the problem formulation. Semianalytical solutions of saturation and pressure distributions are presented.

Experiments were conducted to examine steam displacement of volatile, partially volatile, and nonvolatile nonaqueous-phase liquids at a residual saturation of 2.5%. Complete displacement of all low-viscosity, partially volatile liquids was observed. Displacement of a high-viscosity, nonvolatile oil was not observed. These experiments and similar results from the literature were in reasonable agreement with the model. It is concluded that mass-transfer-limited evaporation of hydrocarbon components with significant vapor pressures is responsible for the observed low residual oil saturations (ROS’s) in the steam zone.
Foam Production During Steam Displacement of Aqueous Surfactants
Authors: Michaels Karen F. , Udell Kent S.
Published: December 2007

The formation and flow of foam in porous media under conditions characteristic of steam injection were examined through a series of one-dimensional (1D) displacement experiments. The steam-front propagation velocity and temperature field ahead of and behind the condensation front were not significantly different for steam injection into partially saturated or dry media compared with injection into a water-saturated medium. Significant differences in measured parameters were observed during steam displacement of a 1 wt% surfactant solution. The steam-phase mobility decreased upstream of the condensation front by factors of 5.7 and 14 under conditions where noncondensable gases were not present and present as an initial gas saturation, respectively. These results clearly indicate that foam is produced during steam displacement of a surfactant solution without the presence of a noncondensable gas. Furthermore, noncondensable gas in the porous matrix was immobilized by the surfactant and aided in the stabilization of the foam in the steam zone.
A Regression Technique With Dynamic Parameter Selection for Phase-Behavior Matching
Authors: Agarwal Rajeev K. , Li Yau-Kun , Nghlem Long
Published: December 2007

The major problem in phase-behavior matching with a cubic equation of state (EOS) is the selection of regression parameters. Many parameters can be selected as the best set of parameters; therefore, a dynamic parameter-solution scheme is desired to avoid tedious and time-consuming trial-and-error regression runs. This paper proposes a regression technique in which the most significant parameters are selected from a large set of parameters during the regression process. This technique reduces the regression effort considerably and alleviates the problem associated with a priori selection of regression parameters. The technique's success is demonstrated by matching experimental data for a light oil and a gas condensate.
Development of Reservoir Descriptions To Aid in Design of EOR Projects
Authors: Chopra A. K. , Stein M. H. , Ader J. C.
Published: December 2007

A technique was developed to obtain reservoir descriptions to aid in the design of EOR projects. This technique incorporates the reservoir performance during primary and secondary processes and the geological, petrophysical, and pressure-transient data. The application of this technique is illustrated for a San Andres formation reservoir.
Laboratory Study of Foaming Surfactant for CO2 Mobility Control
Authors: Di Julio S. S. , Emanuel A. S.
Published: December 2007

The effectiveness of foam as a mobility-control agent has been tested by an immiscible CO2 coreflood displacement of a California heavy oil (14°API [0.97 g/cm3]). Foam was produced by simultaneous injection of 0.5 wt% surfactant solution and CO2. Foam injection recovered an incremental 33.6% of original oil in place (OOIP) by reducing CO2 mobility and diverting CO2.
The Effects of Size, Shape, and Orientation of an Impermeable Region on Transient Pressure Testing
Authors: Britto Paulo R. , Grader Abraham S.
Published: December 2007

A practical consideration of the effects of the shape, size, and orientation of an impermeable reservoir region on transient pressure testing is presented. The constant-rate production well is external to the impermeable region. Impermeable regions may be in the form of sealing fractures of finite length that have little volume associated with them and that are only a local restriction to fluid flow. These regions may also be shale lenses or reduced-permeability regions that, in addition to being a restriction to flow, occupy a significant reservoir volume. This paper considers a single impermeable region with various sizes, shapes, and orientations with respect to the active source well.

The transient pressure response of the constant-rate well is generated by replacing the impermeable boundaries by a set of line sources and then applying the method of superposition. This method can be extended to include pressure responses of interference wells. The method is validated by matching the pressure responses of simple cases like a linear no-flow boundary and an internal circular no-flow boundary.

The key issue of this paper is the detectability of large-scale impermeable reservoir regions by transient pressure analysis. The presence of an impermeable region causes the pressure response to deviate from the homogeneous line-source response. This pressure deviation is the indication that the reservoir is heterogeneous. Four major parameters affect the pressure response of the active source well in the presence of an impermeable region: (1) the shortest distance between the well and the impermeable region, (2) the size of the region, (3) the shape of the region, and (4) the orientation of the region. This paper presents combinations of these four parameters that significantly affect the transient pressure response, as well as some criteria for deciding what impermeable regions may be uniquely detected.
A Comparison Between the Pressure-Lag Model and the Rate-Type Model for the Prediction of Reservoir Compaction and Surface Subsidence
Authors: Smits R. M. M. , de Waal J. A.
Published: December 2007

A theoretical study has been carried out to investigate whether the nonlinear compaction behavior of sandstone reservoirs, which has been reported for most well-documented field cases, can be explained by pressure lags in interbedding and/or neighboring low-permeability (shale) layers. On the basis of the results obtained, it is concluded that pressure-lag effects in normally encountered production scenarios cannot account for these nonlinearities, even under worst-case conditions. Therefore, the nonlinear field-compaction behavior must be caused by rate effects in the sandstone reservoir rock itself. This is supported by the fact that a rate-type compaction model recently introduced does indeed give a good description of the observed field behavior.
Advances in Borehole Seismic Fracture Diagnostics
Authors: Thorne B. J. , Morris H. E.
Published: December 2007

Recent redesign of the hardware, software, and data-reduction techniques associated with a triaxial borehole seismic system (BSS) have made possible better estimates of hydraulic fracture geometry. The redesigned triaxial system now incorporates three geophones per axis and provides 30 times the downhole gain of the replaced system, resulting in improved signal-to-noise ratios. This stronger signal, with an increased digitization rate for each of the six simultaneously digitized channels from two borehole seismic tools, has made possible the acquisition and processing of data that previously were inaccessible. The new electronics makes use of a null system and an improved calibration system that includes a synthetic event generator to produce sinusoidal signals of specified amplitude, frequency, and phase. These make readjustments to maintain system balance while the tool is in place downhole. A maximum likelihood event location scheme, incorporating an algorithm based on the use of directional statistics, is used to compute the location of microseisms and error estimates for these locations. Based on the ability to locate perforation shots, a 25-ft [7.6-m] uncertainty in the location of individual microseisms is the estimated accuracy of the redesigned system. This resulted in a fairly high level of confidence in the determination of the azimuth of the Nov. 1, 1986, hydraulic fracture in the fluvial zone at DOE's Multiwell Experiment (MWX) site.
Influence of Fracture Toughness on the Geometry of Hydraulic Fractures
Authors: Thiercelin M. , Jeffrey R. G. , Naceur K. Ben
Published: December 2007

This paper presents an assessment of the importance of fracture toughness in hydraulic fracturing. The results show that fracture toughness can significantly affect the geometry of hydraulic fractures.
Dynamic Etching Tests Aid Fracture-Acidizing Treatment Design
Authors: Anderson M. S. , Fredrickson S. E.
Published: December 2007

Satisfactory stimulation of oil- and gas-bearing formations by fracture acidizing depends on development of adequate fracture conductivity in the hydraulically induced fracture. The created fracture conductivity is a result of the reaction of the injected acid with the fracture face. This paper describes a laboratory core-testing procedure to evaluate the feasibility of an acid treatment and to allow optimization of several treatment parameters. Applications to treatment design for formations that typically are difficult to stimulate by fracture acidizing are given.
Author's Reply to Further Discussion of Application of Oil Muds
Authors: Bloemendal J. W.
Published: December 2007

I thank Benning for his extensive comments and support of most of my remarks.

In my 38 years as a mud engineer, both in research and in the field, I have seen many magic applications rise, shine, and sink. Much frustration and waste of money is prevented if petroleum engineers are more critical and distinguish between sales talk and science, between theory and practice.

Undoubtedly, oil-based muds (OBM's) outperform water-based muds (WBM's) in specific problem areas, but I believe they have been oversold and applied where no hard facts justified their use. In particular, the claimed higher rate of penetration has never been proved scientifically. In drilling practice, too many factors play a role to justify the conclusions without studies supported by measurements in the laboratory. With a relaxed WL CLS mud of the same weight and bottom-cleaning performance, with more weight on bit (as read on the weight indicator) to correct for the friction loss, and with all other factors the same, I expect little noticeable difference between OBM's and WBM's.
Modeling of the Stability of Highly Inclined Boreholes in Anisotropic Rock Formations
Authors: Aadnoy Bernt S.
Published: December 2007

Simulators have been developed to study the fracture and collapse behavior of boreholes. To take into account the directional properties of real rocks, an anisotropic stress model is used. The model takes into account anisotropic elastic properties, directional shear, and directional tensile strengths. The orientation of the borehole, the in-situ stresses, and the bedding plane can all be arbitrarily related to each other to model actual field situations. This paper presents some of the results of the model. It is shown that neglecting the anisotropic effects introduces an error. Also, studying the anisotropic model yields further insight into the behavior of the borehole.
Concentration Measurements Above an Underwater Release of Natural Gas
Authors: Løes M. , Fanneløp T. K.
Published: December 2007

Underwater gas releases resulting from blowouts, pipeline or riser breaks, etc., represent a fire hazard for structures and craft near the surfacing zone. The hydrodynamics of the underwater bubble plume has been the subject of several recent investigations, but no method or data that are useful in predicting the gas concentration above the surfacing zone are known to exist. This paper presents measurements from a field experiment using methane flow rates up to 1.3 normal m3/s [46 scf/sec] at a depth of 50 m [164 ft]. In addition to the continuous concentration measurements from four sensors in the surfacing zone (50 cm [20 in.] above the water surface), certain plume parameters (e.g., plume rise time in air and water and plume center wandering and offset) were either measured or deduced from video recordings. The experiments were performed under ideal weather conditions and the data obtained were not influenced by such extraneous environmental factors as wind, waves, currents, or stratification. For comparison with the data, a simple momentum theory was developed for the zone of formation of the light-gas plume. The agreement with the averaged concentration data is very good over the range of flow rates investigated.
Chemical Shrinkage Properties of Oilfield Cements
Authors: Chenevert M. E. , Shrestha B. K.
Published: December 2007

Chemical shrinkage was measured at elevated temperatures and pressures for 29 different cements with modified PVT equipment. Results showed that a "dilution" effect exists; i.e., the cements that had the highest yield had the lowest chemical shrinkage. For the 29 tests, the maximum chemical shrinkage measured was 4.6% and the minimum was 1.6%. Tube column tests showed that chemical shrinkage helped to reduce hydrostatic pressures.
Uses and Limitations of Drillstring Tension and Torque Models for Monitoring Hole Conditions
Authors: Brett J. F. , Beckett A. D. , Holt C. A. , Smith D. L.
Published: December 2007

This paper presents the results of the application of a tension/torque model to directional wells drilled worldwide. The final inclination of the wells ranged from 25 to 70°, and the tension/torque model was effectively used in these cases to aid in planning the directional program before spudding, to monitor the wells during drilling, and to analyze particular drilling problems after completion. The first set of examples represents the situations to which the tension/torque model can be routinely applied and shows that the model can effectively aid the well planner in selecting the best well path, drillstring designs, casing program, and mud system before spudding. A second set of examples shows how real-time monitoring of drilling conditions can be combined with the model to develop a baseline so that deviations from expected behavior can be analyzed and explained. Appropriate action can then be taken to remedy problems before they become serious. A final set of examples shows how a tension/torque model can be effectively used to determine the actual cause of a particular drilling problem after a well is completed. Experience gained from postanalysis of problems can be used to improve later operations. This paper also compares field data with model predictions for a wide range of different inclinations.
Swelling of Oil-Based Drilling Fluids Resulting From Dissolved Gas
Authors: O'Bryan Patrick L. , Bourgoyne Adam T.
Published: December 2007

The method presented in this paper uses an experimentally calibrated equation-of-state (EOS) model to estimate the swelling of oil-based drilling fluids caused by dissolved methane. With this method, the pit gain associated with a given kick size can be determined. The calculation method was verified by experiments conducted in a 6, 000-ft [1828.8-m] test well. Example calculations are also presented.
Directional Acoustic Surveying Instrument
Authors: Treherne D. M. , Harper P. G. , Su D.
Published: December 2007

A new type of acoustic detector capable of determining the direction of a noise source was developed. Under granite transmission at a depth of 600 m [1,970 ft] and ranges up to 200 m [655 ft], directional accuracies of 1 to 2° were achieved. Detectable sources included quasicontinuous (e.g., drill-bit) noise and pulses (e.g., explosive or sparker tool). The sensing element is a symmetric resonator whose flexural modes are readily excited by an external acoustic source. The physical principle is that the phase plane of a strong acoustic spectral component fixes the nodal directions of the resonant flexural vibrational mode, thus establishing the propagation direction in relation to the modal symmetry. The resonator is encapsulated in oil to damp the vibrations and to retain and communicate the acoustic signal. (The vibrational modal pattern is detected with strain gauges and processed to provide directionality.) This paper presents (1) vibrational response theory; (2) construction details; and (3) analysis of field data leading to directionality.
Flow of Non-Newtonian Fluids Through Eccentric Annuli
Authors: Luo Yuejin , Peden J. M.
Published: December 2007

The laminar eccentric annular flow of non-Newtonian fluids is analyzed with a new method where an eccentric annulus is represented by an infinite number of concentric annuli with variable outer radii. The analytical solutions for the shear stress, shear rate, velocity, and volumetric flow rate/pressure gradient are obtained for both power-law and Bingham-plastic fluids. This method is shown to provide more accurate approximations for various profiles and good predictions of the volumetric flow rate/pressure gradient in eccentric annular flow. In addition, turbulent eccentric annular flow is discussed.
Drag Bit Wear Model
Authors: Slnor A. , Warren T. M.
Published: December 2007

A performance model for polycrystalline-diamond-compact (PDC) bits was modified to include the wear prediction of individual cutters. Wear predictions are based on the geometry of each cutter, the rock type, the forces acting on the cutter, cutter velocity, and cutter temperature. The results of predicted and actual cutter wear for different 8½-in. [21.6-cm] field-worn PDC bit designs are shown. The worn geometry of each cutter was measured and compared with the model's prediction.

Laboratory performance tests were also conducted with similar bit designs to quantify the effect of bit imbalance. Reduced rate of penetration (ROP), drilling an overgauge hole, and increased cutter wear and breakage can result from bit imbalance.
Computation and Interpretation off Miscible Displacement Performance in Heterogeneous Porous Media
Authors: Corrêa A. C. , Pande K. K. , Ramey H. J. , Brigham W. E.
Published: December 2007

Computation of miscible displacement performance requires an estimate of the amount of mixing in the reservoir. Dispersion coefficients measured from displacements in laboratory cores are often used to compute reservoir performance. This paper considers interpretation of effluent flowing concentration data obtained from heterogeneous cores by use of the Coats-Smith, porous-sphere, and transverse-matrix-diffusion heterogeneous models. Analytical solutions to the three heterogeneous models are presented in Laplace space. Approximate solutions for short- and long-time effluent flowing concentrations, developed from simplification of the Laplace transformation solution, are used to develop practical methods of interpreting effluent concentration data to determine model parameters. Criteria for design of laboratory experiments based on these results are suggested.
Composition Paths in Four-Component Systems: Effect of Dissolved Methane on 1D C02 Flood Performance
Authors: Monroe W. Wesley , Silva Matthew K. , Larsen L. L. , Orr Franklin M.
Published: December 2007

New measurements of phase compositions and densities are reported for a quaternary system containing CO2, methane, butane, and decane and related ternary systems at 160°F and 1, 250 psia [71°C and 8620 kPa]. Measured values of phase compositions and vapor densities agreed well with values calculated with the Peng-Robinson equation of state (PREOS), though calculated liquid densities were less accurate. Composition paths for two-phase flow of four-component mixtures were calculated with the method of characteristics and the equation-of-state (EOS) representation of the phase behavior. Analysis of resulting paths indicates why displacement efficiency in ID CO2 floods is insensitive to the addition of dissolved methane to the oil displaced. Methane in the oil partitions so strongly into the more mobile vapor phase that a methane-rich bank forms at the leading edge of the transition zone. The displacing CO2 then encounters hydrocarbon mixtures without methane. Analysis indicates that high displacement efficiency is possible even when two-phase flow occurs throughout the displacement and that high recovery is possible even when a live oil is displaced below its bub-blepoint pressure (BP), if the pressure is above the minimum miscibility pressure (MMP) for the same oil with all methane removed.
A Cross-Sectional Simulation of West Heidelberg In-Situ Combustion Project
Authors: Kumar Mridul
Published: December 2007

In-situ combustion (ISC) in a deep, thin, dipping reservoir was simulated to delineate major production mechanisms and to improve reservoir management. Results show that air injection is preferable over flue-gas injection because pressure maintenance accounts for less than half of the cumulative oil production. Water injection following air breakthrough resulted in little incremental recovery. Recovery can be maximized by placing the production well near the lower edge.