bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of the Critical Gas Saturation
Authors: de Swaan A. 
Published: December 2007

Introduction
The critical or threshold gas saturation is a specific property of the porous medium and internal fluids. property of the porous medium and internal fluids. Compared with the experimental research on the subject, I the theory of gas saturation development to its critical value and the significance of this growth on reservoir performance have received little attention. For a volumetric reservoir - i.e., one with negligible water influx and negligible change of rock porosity with internal fluid pressure change, and with porosity with internal fluid pressure change, and with water production and expansion also considered zero - the usual procedure to compute gas saturation development is the material balance equation:
Bo - Boi + Bg (Rsi- Rs) Np=------------------------ N,..............(1) Bo + Bg (Rp - Rs)
with average reservoir pressure below the bubble-point pressure and Sg less than Sgc. In Eq. 1,
1 Np Rp = --- RsdNp.........................(2) Np 0
In words, only the solution gas has been produced, since the gas saturation remains insufficient for gas flow. The recovery percentage is obtained from the material balance equation; the gas saturation is obtained from the recovery percentage. Eq. 1 is an involved integral equation of a type unknown to me. Np is a self-dependent variable with the limit of the integral in the denominator - Eq. 2. In Ref. 2, Eq. 1 is not presented in the form shown but as a numerical solution procedure that simplifies the presentation. In fact, this numerical solution is an everyday affair for the practicing engineer. An alternative formula is presented. presented. JPT
P. 907
Oil-Recovery Surfactant Formulation Development Using Surface Design Experiments
Authors: Gerbacia W. , McMillen T. J. 
Published: December 2007

Abstract
Experiments were conducted to study the effects of three surfactant flooding variables on oil recovery and interfacial tension (IFT). The variables studied were the fraction of high-equivalent-weight sulfonate, the cosurfactant hydrophile-lipophile balance (HLB), and the weight ratio of cosurfactant to sulfonate. We then evaluated the data statistically, obtaining optimal formulations for this data space. From trends observed in the investigation, a high crude-oil recovery formulation was developed for this crude-oil/brine system. All three variables had a significant effect on oil displacement. The high-equivalent-weight sulfonate was detrimental to recovery of the crude oil used in this investigation. Systems with low measured interfacial tensions did not produce the highest recoveries. This is explained by extraneous dominating effects.
A Copper Ion Displacement Test for Screening Corrosion Inhibitors
Authors: Hughes William B. 
Published: December 2007

Abstract
A method for the selection of the most suitable corrosion inhibitor for a particular system is given. The method involves the evaluation of surface passivity by means of copper ion displacement after the metal surface has been subjected to the corrosive atmosphere. The application of the method to the selection of suitable inhibitors for use in producing wells is described.
Correlation with recognized laboratory tests has been found to be good within the limitations of the test. The use of the test to evaluate inhibitor persistence is described.

Introduction
Corrosion as it is associated with the industry shows wide variations in its qualitative as well as its quantitative aspects. This complicates the work of the corrosion engineer.
In the past few years the efforts of the corrosion engineer have been further taxed by the large numbers of products being marketed as corrosion inhibitors by various manufacturers. These products are submitted to him together with a limited amount of data to support their use as inhibitors. The data are usually authentic and reliable yet all too often when these products are applied to an actual corrosive system the results are disappointing due to the ineffectiveness of the inhibitor and the corrosive system.
The corrosion engineer must select a comparatively limited number of inhibitors for field trial from the large number available. The selection is usually made on the basis of a standardized laboratory test such as that adopted by the National Association of Corrosion Engineers or by field experience in an area; however, testing of this type is discouraging on large numbers of compounds, particularly in view of the specificity of environment.
It has been an object of this work to devise a method which will allow the corrosion engineer to select the best inhibitor for a specific environment under field conditions. The test would of necessity be rapid and inexpensive. It would preferably eliminate the need for expensive and delicate instruments.
Pore-Level Observation of Gravity-Assisted Tertiary Gas-Injection Processes
Authors: Ren W. , Bentsen R. , Cunha L. B. 
Published: December 2007

SummaryIn waterdrive oil reservoirs, more than half the initial oil in place (IOIP) is trapped in the water-contacted zone after natural water influx or waterflooding. Gas injection into such reservoirs, with the assistance of gravity, interfacial tension, and oil-film flow, can cause the displacement of excess water and the redistribution of reservoir fluids in the pore space. As the result of such fluid redistribution, most of the residual oil can be recovered. Moreover, a second waterflood following the gas injection can recover the oil in a shorter period of time.Gravity-assisted tertiary gas-injection processes include the double-displacement process (DDP) and the second-contact water-displacement (SCWD) process. The DDP consists of injecting gas into waterflooded oil zones. The SCWD process consists of submitting these gasflooded zones to a new water-displacement process. In this work, the DDP and the SCWD process were conducted in a transparent sandpack micromodel, and a pore-level observation was performed to investigate the microscopic mechanisms of the two processes.Observation of the two processes confirmed that the oil films play a very important role in achieving high recovery efficiencies in the DDP. The oil film was seen clearly; such observation also showed that oil flowing through oil films and layers was driven not only by its own weight but also by the increasing volume of the gas. In the SCWD process, trapped gas reduces the possibility of the residual oil being trapped in the center of the pores. Consequently, residual oil can be recovered quickly by a second water-flood. Therefore, the SCWD process is suitable to apply in situations in which the source of gas is not sufficient and in which the formation has a high irreducible gas saturation.
The Transfer of Through-Tubing Drilling Technology Between Provinces
Authors: Morrison John W. 
Published: December 2007

Summary
Many companies operate on a global basis. Often, a new idea or technology can make a step change in the economics or performance in a particular province or field. That leaves the company with the enviable problem of understanding how and where it could impact operations in other areas of the world.
One area in which BP has had such success is in the North lope of Alaska, where through-tubing drilling (TTD) has made a dramatic impact on their infill-drilling program. In fact, Alaska had developed two distinct TTD techniques—coiled-tubing drilling (CTD) and through-tubing rotary drilling (TTRD). This paper discusses how the technology was transferred to the North Sea. The subject is tackled on three levels:
Transfer of practical knowledge. Tactical choice on the optimum technique. Determination of the strategic value of the technology.
This paper illustrates what needs to be done to ensure a successful business outcome when trying to gain the benefits of a new technology in a different operating environment.
To illustrate the issues, this paper presents performance information on both TTD techniques used in Alaska, discussing their differences and why the application of CTD, in particular, has made such a significant impact. It then discusses how the North Sea's operating environment differs from the North Slope, how this influenced the choice of technology, and the potential magnitude of the benefit that could be realized.
By the end of the analysis, it became clear that the solution and strategy for the North Sea had to be different from that of Alaska, and it became apparent why CTD has struggled to make an impact in the North Sea.
Marlin Failure Analysis and Redesign: Part 3—VIT Completion With Real-Time Monitoring
Authors: Gosch S. W. , Horne D. J. , Pattillo P. D. , Sharp J. W. , Shah P. C. 
Published: December 2007

The redesign solution for the batch-drilled wells remaining after the deformation of the Marlin Well A-2 production tieback and tubing was vacuum-insulated tubing (VIT). VIT implementation, however, required a number of computational and experimental innovations.To ensure well survival, a distributed temperature-monitoring system was developed and evaluated during full-scale VIT testing. Fiber-optic cable run on completions continuously monitors the production-annulus temperature profile. The monitoring system has also proved to be a valuable quality-assurance measure for special annular gels used to minimize conduction and natural convection in the production annulus.AbstractFollowing the failure of the initial well in the Marlin field,1 the preferred solution for completing the remaining wells was to control wellbore temperature by means of VIT.2 Implementation of VIT required a number of computational and experimental innovations, including:Provision for insulating the tubing couplings, the source of up to 90% of VIT heat loss. Detailed flow-loop temperature profiles with both axial and radial probes traversing the annulus outside the VIT. These profiles supplemented the conventional values of the overall heat-transfer coefficient and thermal conductivity obtained from the flow-loop measurements. VIT performance, as measured experimentally, must exceed both thermal and mechanical design bases.Because well survival depends on proper VIT performance, a distributed temperature-monitoring system was developed and evaluated during full-scale testing. On the Marlin tension-leg platform (TLP), fiber-optic cable is run in each well along the length of the VIT to monitor the production-annulus temperature profile continuously. A software system was also developed to feed binary fiber data to an integrated thermal-simulator casing-design software package that calculates safety factors for the B and C annuli. These real-time safety factors interface with the platform alarm system and are continually monitored by operators. If a low safety factor is calculated, a well will be shut in. In addition to feeding the platform alarm system, the software provides data to a web-based plotting program. If a single VIT joint loses its insulating properties, this specific joint can be identified, and appropriate action can be taken. The monitoring system has also proved to be a valuable quality-assurance measure for special annular gels used to minimize conduction and natural convection in the production annulus.This paper focuses on the value of the combined VIT and fiber/software monitoring system as a means of both controlling and observing well thermal behavior. Typical temperature vs. depth curves are used to illustrate the detailed information retrieved.
Pressure Buildup Analysis of Geothermal Steam Wells With a Parallelepiped Model
Authors: Economides Michael J. , Ogbe David , Miller Frank A. , Cinco-Ley Heber , Fehlberg Eric L. 
Published: December 2007

Summary
Geothermal well testing, a discipline that evolved from conventional oil and gas well testing, often requires special considerations. The geometry of the reservoir and those characteristics frequently found in geothermal systems engendered the idea of a parallelepiped model with interpenetrating fractures. Such geometry can be described mathematically using Green's and source functions. Equations of reservoir pressure behavior then can be developed for both drawdown and buildup tests. Graphs describing dimensionless pressure as a function of time and various reservoir parameters are provided in this paper. The general method used is type-curve matching.

Introduction
There are three major types of geothermal resources:(vapor-dominated (dry-steam) such as in The Geysers (CA) or in Tuscany of central Italy,two-phase such as in New Zealand, andhot-water, found in several locations.
The most useful, in terms of power production, are the vapor-dominated reservoirs. They are also the most rare. A number of geothermal reservoirs exhibit transient pressure behavior that indicates large, highly conductive fractures. The size of these reservoirs is controlled by faults and overlying impermeable rocks. A constant-pressure boundary, presumably boiling water, often is observed.
A parallelepiped model conceptually could approximate such a configuration. A model with closed, no-flow boundaries on five sides and a constant-pressure boundary on the bottom was described by Cinco-Ley et al. The fracture system was simulated as a rectangular-shaped source. The concept is limited to vapor-dominated reservoirs. Both geologic evidence and production histories have precluded the use of radial models in both The Geysers and Larderello, Italy. Hence, the parallelepiped model, with the included fracture and subformation boiling front, is intended to analyze pressure transient behavior in dry-steam geothermal wells.

Model Description
The model assumes constant-flow-rate production in an anisotropic, homogeneous reservoir. If the flow rate vases, an influence function such as that described by Economides et al. can be used in the subsequent type-curve matching. The reservoir described by the model contains a slightly compressible fluid of constant viscosity and compressibility c. an assumption totally inadequate in the case of geothermal steam. Yet the shortcomings can be overcome if the pseudopressure function m(p) is used. The real-gas pseudopressure was discussed by Al-Hussainy and Ramey. All of these assumptions normally are used in geothermal well testing, irrespective of the model. Although the solution can be modified to incorporate fracture(s) anywhere in the reservoir, a vertical, partially penetrating fracture has been used. The fracture is in the center of a parallelepiped reservoir of square horizontal cross section.
JPT
P. 925^
Equation of State of a Complex Fluid Column and Prediction of Contacts in Orocual Field, Venezuela
Authors: Smith Richard W. , Bard Wade A. , Guerini Agostino , Lugo Claudia , Yemez Ivan 
Published: December 2007

SummaryThe Orocual field is located in the northern Monagas state of Venezuela and is owned and operated by Petroleos de Venezuela S.A. (PDVSA), the national oil company of Venezuela.Reservoir compartmentalization adds complexity to the field, and structurally equivalent, noncommunicating fluid regions exist. An equation of state (EOS) is needed for reservoir modeling, requiring a review of available data and area fluid distributions.A seven-pseudocomponent EOS with a single characterization defining the compositional gradient of the hydrocarbon column from gas to black oil is defined. The method demonstrates that composition relative to depth can be predicted in those parts of the reservoir in which samples do not exist but in which production and test data must be matched, and thus where a gas-to-oil transition occurs.This paper demonstrates a technique to identify representative samples for use in developing an EOS and for initializing fluids in place. A method is presented to adjust the component composition vs. depth, providing consistent vertical composition distribution and compositional-model stability. This method meets the objectives of matching field production observations. A method is presented to quickly initialize a full-field model using a 1D compositional simulator to give full-field-model stability using the local high-temperature gradient.Results of compositional simulation show a single EOS, and vertical compositional and thermal variation reproduce the complex character of the field hydrocarbon column, matching field-measured observations of saturation pressure (ps), gas/oil ratio (GOR), and fluid densities.
Three-Phase Displacement Theory: An Improved Description of Relative Permeabilities
Authors: Juanes Ruben , Patzek Tad W. 
Published: December 2007

SummaryIn this paper, we revisit the displacement theory of three-phase flow and provide conditions for a relative permeability model to be physical anywhere in the saturation triangle. When capillarity is ignored, most relative permeability functions used today yield regions in the saturation space where the system of equations is locally elliptic, instead of hyperbolic. We are of the opinion that this behavior is not physical, and we identify necessary conditions that relative permeabilities must obey to preserve strict hyperbolicity. These conditions are in agreement with experimental observations and pore-scale physics.We also present a general analytical solution to the Riemann problem (constant initial and injected states) for three-phase flow, when the system satisfies certain physical conditions that are natural extensions of the two-phase flow case. We describe the characteristic waves that may arise, concluding that only nine combinations of rarefactions, shocks, and rarefaction-shocks are possible. Some of these wave combinations may have been overlooked but can potentially be important in certain recovery processes.The analytical developments presented here will be useful in the planning and interpretation of three-phase displacement experiments, in the formulation of consistent relative permeability models, and in the implementation of streamline simulators.
Shaybah-220: A Maximum-Reservoir-Contact (MRC) Well and Its Implications for Developing Tight-Facies Reservoirs
Authors: Saleri N. G. , Salamy S. P. , Mubarak H. K. , Sadler R. K. , Dossary A. S. , Muraikhi A. J. 
Published: December 2007

Summary
This paper presents drilling, completion, well-performance, and reservoir-characterization results of a recently drilled maximum-reservoir-contact (MRC) well in the Shaybah field with a total of eight laterals and an aggregate reservoir contact of 12.3 km (7.6 miles). The well was drilled as part of a pilot program to evaluate both the practical challenges and the reservoir performance impact of MRC wells.
The results to date on eight MRC wells in Shaybah indicate significant sustainable gains in well productivities as well as reductions in unit-development costs. A useful byproduct of MRC drilling is the enhancement achieved in reservoir characterization. These benefits point to MRC wells as disruptive technologies (DTs)1,2 that have positive implications for developing tight-facies reservoirs.
Subsea Development of Shallow, Low-Pressure Gas Reservoirs With High-Performance Well Designs
Authors: Burton R. C. , Davis E. R. , Hodge R. M. , Gilbert T. , Stomp R. , Abdelmalek N. , Bailey M. 
Published: December 2007

SummaryIn the summer of 2000, ConocoPhillips began a program to develop a series of shallow, low-pressure gas reservoirs in the Indonesian waters of the west Natuna Sea. The project consists of a series of subsea wells linked by pipeline to a central mobile gas-processing and -compression unit that feeds a sales line to Singapore. The overall project life is 20 years and will require developing eight small fields with reserves on the order of 1 trillion scf gas.Initial project planning used conventional well designs to deliver rates on the order of 20 MMscf/D/well from a number of gas reservoirs. This type of well productivity required 10 wells to meet ConocoPhillips Indonesia's maximum contract supply rate, with several wells allocated to each reservoir. To improve project economics, a reduced well count employing high-performance completion designs was developed. The high-performance completions were designed to provide flow rates on the order of 100 MMscf/D at initial reservoir pressures ranging from 1,250 to 1,900 psi. These flow rates allowed well counts to be reduced to one well per reservoir.This paper will review ConocoPhillips's methodology for design and implementation of the first four high-performance completions in the west Natuna Sea gas project. Well deliverability and initial project results are discussed.
Study of Vuggy Carbonates Using NMR and X-Ray CT Scanning
Authors: Hidajat I. , Mohanty K. K. , Flaum M. , Hirasaki G. 
Published: December 2007

Summary
Most existing nuclear magnetic resonance (NMR) permeability correlations for carbonates assume that vugs do not contribute to permeability. The objective of this work is to improve permeability estimation from NMR responses for carbonates by including vug connectivity. Six carbonate samples from a west Texas field were studied. NMR T2 measurement, mercury porosimetry, thin-section imaging [using optical microscopy and a scanning electron microscope (SEM)], computerized tomography (CT) scanning, and electrical measurements were conducted. The permeability of the samples studied is controlled by the channels that connect vugs. Capillary pressure and NMR T2 measurements show multimodal pore-throat and pore-body-size distributions. A modified Chang model, which includes the tortuosity factor, is proposed and proven to yield a better permeability prediction than the original Chang model. It is also shown that for the samples studied, the tortuosity can be estimated from NMR T2 distribution, hence allowing permeability prediction from the NMR T2 distribution alone.
Filtration Properties of Oil-in-Water Emulsions Containing Solids
Authors: Al-Riyamy Kassim , Sharma Mukul M. 
Published: December 2007

Summary
This paper describes a laboratory study of the factors controlling the filtration and fluid-leakoff properties of emulsions containing solid particles. Such fluids are sometimes used as low-leakoff completion fluids.
High-pressure/high-temperature (HP/HT) filtration tests clearly demonstrate that emulsions have the ability to reduce filtrate loss to the formation. However, the emulsion droplets tend to invade the formation and form an internal filter cake. This is evident from the liftoff pressures needed to initiate flowback and deep invasion of emulsion droplets in long-core experiments. Emulsions containing solids (CaCO3, in our case) had lower filtrate volume and higher return permeabilities than solids-free fluids. The effects of percent oil, filtration pressure, core permeability, temperature, and viscosity of the continuous phase were investigated. Filtration pressure and core permeability had major influences on the filtration properties of the emulsified completion fluids. Higher injection pressures increased internal damage and lowered the return permeability. Higher-permeability cores had higher filtrate loss. Emulsion droplets were observed in the effluent, and solid particles are needed to form a stable external filter cake.
Long-core experiments showed that using emulsions containing acid-soluble solid particles have 100% return permeability after an acid squeeze, showing that the emulsion-droplet invasion depth is less than 1 in. It is shown that solids-free fluids had the highest formation damage and higher liftoff pressures.
Analysis of the fluid-leakoff data indicates that emulsions containing solids do not behave as classical filtration theory predicts because of the invasion of emulsion droplets into the formation.
Sizing the solid particles and emulsion droplets in completion fluids and muds according to the permeability of the rock is important in forming stable external filter cakes. This increases the return permeability and results in easier cake removal (low liftoff pressures).