bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas Well Testing Using Negative Superposition
Authors: Slider H.C. 
Published: December 2007

Introduction
The prediction of gas well deliverability under various operating conditions including variations in spacing and reservoir depletion has always caused problems. Many years ago it was observed that in most cases a plot of the log of the producing rate versus the log of the static reservoir pressure squared minus the square of the flowing well pressure. log (Pe2-pw 2), resulted in a straight line. It has since been shown that theoretically such a straight line is obtained only when pseudo steady state flow is obtained at each rate which means that each rate must be maintained until the effects of that rate have been felt throughout the drainage area of the particular well. If this condition is not met, the apparent straight line that is obtained does not represent the slope that-would be obtained from stabilized (pseudo steady state) data. Furthermore, there is generally a great difference between the position of the deliverability curve for the uncorrected flow after flood type data and the deliverability curve that would be obtained for stabilized flow. These points are illustrated in Figure 1. Note that "pseudo steady state" and "stabilized conditions" are used interchangeably in this paper.
The problem is that in most gas reservoirs the stabilization time is excessive. In some tight widely spaced, commercially produced wells it can be shown that stabilization is not obtained after one year's time. Thus, it becomes necessary to test the well under infinite acting conditions and interpret the data in terms of the performance that would be obtained after stabilized conditions are reached The isochronal, technique was proposed for performing such infinite acting tests and performing such infinite acting tests and interpreting the data in terms of stabilized data. Ideally this technique involves producing at a particular rate for some relatively short particular rate for some relatively short period of time, shutting the well in until the period of time, shutting the well in until the reservoir pressure reaches static conditions, initiating production again at a different rate for the same length of time, shutting the well in until the static pressure distribution is again obtained in the reservoir, producing at a third rate for the same length of time, shutting the well in … etc. Theoretically, this technique has much to offer and a correct application of the data will provide the desired predictions. However, in practice the engineer predictions. However, in practice the engineer is always faced with the problem of how long to shut the well in between flow periods.
Application of a Decision-Making Model for Economic Evaluation of Production-Sharing Contracts in India
Authors: Vikas Shree , Eppink Jeffrey , Godec Michael 
Published: December 2007

Abstract
In this paper, the production sharing contract (PSC) terms and conditions are incorporated into a decision-making model of hydrocarbon production. Based on input parameters such as oilfield size, prices, exploration, development and operating costs, decline rates, cost recovery methods and profit oil split, the model was used to evaluate best, worst, and most likely scenarios. In each of the scenarios, the oil production rate from the field increases initially up to the maximum efficient production rate, as surface facilities are built, followed by a plateau period of constant production rate and then finally a decline as in typical offshore fields. Using the expected net present value (ENPV) of a project under various technology and financial arrangements, the model performs the summary economics of a scenario based on the pro-forma cash flow analyses. The numerical example for India has been developed to reflect geological, economic, and the recent contractual data as defined in the 1997 New Exploration Licensing Policy (NELP) for PSC agreements. The best and worst cases examine the optimistic and the pessimistic scenarios about the profitability of a project. In the third case (most likely case), probability distributions for various crucial parameters are specified in the model. The model also calculates India's share of economic rent from oil and gas production in these cases. Finally, a sensitivity analysis is performed on parameters which provides insights into mutually beneficial negotiating terms between the government and the multinational corporation.
Results indicate that recent PSC terms in India can be attractive to multinational corporation (MNC) investors for medium to large discoveries. Conversely, smaller projects have greater difficulty achieving profitability. The most likely case indicates a modest government take of around 46 percent in India. Sensitivity analyses show that reserve size and production decline are the dominant factors for determining project payout and net present value. In addition, PSC projects in India are less sensitive to factors such as profit oil split and cost recovery oil terms.
Evaluation of a New Sealing Fluid for Water Control Problems as Well as for Sealing Highly Porous Formations
Authors: Garcia C.F. , Otto R.L. 
Published: December 2007

Abstract
Controlling the permeability of subterranean formations adjacent to the well bore has three aspects which are important to effective production during the life of a well. These are:
1. Controlling lost circulation during drilling.
2. Minimizing water production from oil producing zones.
3. Blocking thief zones in steam and water injection wells.
An effective solution of all three problems is embodied in a low viscosity, problems is embodied in a low viscosity, polymer carrying fluid which, on polymer carrying fluid which, on mingling with dissolved salts in formation brines, coagulates into a solid and is thereafter rendered inert to aqueous fluids. Among the polymer's advantages are that,
(1) It can be utilized to penetrate the seal the more permeable zones penetrate the seal the more permeable zones without substantially affecting the less permeable zones;
(2) It can be chemically altered to promote deeper penetration;
(3) The sealing reactions do not require curing time and a well can be returned to production immediately after treatment; production immediately after treatment;
(4) It can aid in retaining cement slurries in place to allow the cement to set in a formation incapable of maintaining hydrostatic pressure and
(5) Any positive pressure differential on the polymer positive pressure differential on the polymer increases effectiveness of the seal.

Description of the sealing fluid's properties
The sealant consists of micron sized resinic vinyl copolymers dispersed in water and having a milk-like appearance. Just like milk, the polymeric dispersion will coagulate into a solid when treated with acids. Due to the tall oil stabilizers used in maintaining the colloidal dispersion in fresh water, the polymer can also be made to coagulate with salts of multi-valent ions. Typical properties of the polymer are listed below.
Stochastic Modeling of Geometric Objects and Reservoir Heterogeneities
Authors: Lanzarini W. L. , Poletto C. A. , Tavares G. , Pesco S. , Lopes H. 
Published: December 2007

Abstract
The object based method used for reservoir characterization is a technique for geometric modeling and stochastic simulation of geological units and reservoir heterogeneity. A set of geological objects representing basic reservoir units is conceptually and quantitatively defined, has its parameters quantified and modeled on an interactive computer environment. The objects include channels, lobes, sigmoids, dunes, ellipsoids, plane beds and wedges.
The conditional stochastic simulation of these objects produce 3-D models of the depositional or diagenetic reservoir architecture. This methodology has been applied in fluvial (Potiguar basin) and turbidite (Campos basin) reservoirs.

Introduction
Modeling of reservoir geometry and heterogeneity is a necessary activity of oil exploitation. Mathematical and computer methods are used to integrate efforts in geology, geophysics and reservoir engineering for defining optimal reservoir characterization and oil production.
The use of probabilistic mathematical models to represent reservoir heterogeneities is booming. However, the stochastic simulation models based only on variograms is insufficient to represent the geometry and distribution patterns of genetic units as well as the diagenetic and structural reservoir features (Fig. 1).
The combination of stochastic and geometric methods in the object based approach has proved an adequate alternative to generate equiprobable realizations of the reservoir architecture.
An object based method for reservoir characterization is presented in this work. This technique consists of geometric modeling and stochastic simulation of discrete features such as, genetic units and diagenetic heterogeneities of the reservoirs.
Boolean and Object Based Models The Boolean model has been designed to express the intuitive idea of an union of independent objects located at random, and a mathematical morphology method used mainly to 2-D modeling of natural or technical images.
The object oriented model, according to the stochastic geometry terminology, is a Point Process, more specifically defined as a Random Closed Set.
Pressure Transient Behavior of Stress-Sensitive Reservoirs
Authors: Jelmert T. A. , Selseng H. 
Published: December 2007

Abstract
The choice of state variable in the non-linear diffusion equation may be of importance when analytical solutions are desired. The behavior of stress-sensitive reservoirs can best be predicted when the diffusion equation is formulated in terms of a permeability-like variable. Then the resulting equation becomes practically linear and approximate analytical solutions are possible.
We find that the validity of a steady state skin factor is uncertain for stress-sensitive reservoirs. Different conceptual models are possible. A skin factor based on the equation of steady state flow in a stress-sensitive reservoir is recommended.
The most common linearization techniques, the Cole-Hopf and the Kirkhoff transformation, are equivalent when the permeability pressure relationship is given by an exponential function.
A material interface leads to a discontinuity in the transformed variable. The jump condition is given by powerlaw relationship. Hence application of linearization techniques to layered and commingled reservoirs may be problematic. We find that the technique may be applied when the modulus to permeability is approximately the same in each layer.
Stress Analysis of Casing String Submitted to Cyclic Steam Injection
Authors: Plácido João C. R. , Ademar P. , Paulo Luíz A.B. F. , Pasqualino Ilson P. , Estefen Segen F. 
Published: December 2007

Abstract
Oil well casing string may present intervals with cementing failure. If the well is submitted to cyclic steam injection, some problems may happen to this section. The heating and cooling process may generate residual stresses (tension) in the casing interval where cementing is not well bonded to the formation or to previous casing. These residual stresses decrease the casing collapse capacity. In this interval, may exist fluid trapped behind the casing, which may be or previous fluid that was not well displaced or free water from cement. Therefore, in the next heating step, this fluid will expand and may collapse the casing. A numerical model and an experimental apparatus were developed to simulate this situation. A finite element analysis incorporating geometric and material non-linearities is carried out to evaluate the residual stresses and their effects on the collapse pressure capacity of the casing. The experimental work allowed to understand this phenomenon. The numerical model is validated using results from tests performed at PETROBRAS and literature data.
New Approach on Cement Evaluation for Oil and Gas Reservoirs Using Ultrasonic Images
Authors: Coelho de Souza Padilha Solon Thomasz , da Silva Araujo Romero Gomes 
Published: December 2007

Abstract
The cement job is one of the final operations during completion and has a major importance on the performance of the well productivity. A poor interpretation of the cement job quality due to lack of information can lead to wrong decisions, such as inappropriate squeeze jobs and at worse poor reservoir fluid evaluation, usually these operations are expensive and result in high losses.
The use of high vertical and horizontal resolution quantified acoustic impedance images from ultrasonic measurements brings a new perspective in cement evaluation for oil/water wells and combined with traditional CBL-VDL log provides a complex understanding and definition of cement quality in oil/gas reservoirs helping the completion efficiency. Examples are presented and the interpretation is discussed showing the superiority of the measurements and results.

Introduction
The lack of cement integrity can compromise the final well production and cause unwanted communication between different reservoir zones, which in some cases can result even in ecological damage when, for example, a hydrocarbon zone communicates to an aquifer, situation which can happen where this was carried on. Cement evaluation logs are being studied more and more in order to achieve a full understanding of the cement quality and performance of the cement job.
The usual interpretation of cement evaluation logs is based on sonic and ultrasonic principles, each one has its applications and limitations. Lately, with the introduction of the new wireline logging tool for cement evaluation and corrosion detection by ultrasonics, the USI* (Ultrasonic Imager), the cement quality analysis has had a great improvement due to its high vertical and horizontal resolution of the quantified acoustic impedance image display and together with the traditional CBL-VDL log, a conclusive interpretation of the cement quality can be achieved.
Some problems like gas contaminated cement and channelling have always been causing doubts on the interpretation of cement evaluation logs and in several cases increasing costs due to cement correction with squeeze jobs.
The technique proposed here is based on the fact that the information of the CBL-VDL log and the full radial cement acoustic impedance image, provided by the USI, complement each other, greatly eliminating interpretation doubts and giving a conclusive definition on the decision to run a squeeze job or not.
An Intelligent System for Process Plant and Well Production Control with Problem Diagnosis
Authors: Patricio A.R. , Morooka C.K. , Rocha A.F. 
Published: December 2007

Abstract
In an oilfield production, the operation of a process plant is very sensitive to the disturbance such as variations in the flow rate and the pressure from the wells. Moreover, variations in the parameters of the oil production could represent abnormalities in the well production. Identification of problems in operation of process plant and, especially oil well production operation demand mainly symbolic reasoning. In gas lift well, gas surface card provides important information but not all data required for decision making then, symbolic reasoning is needed. Many kinds of problems can occur in a production process plant and well operation. In the present paper, neural nets are used to develop an intelligent system whose purpose is to support intelligent control of well production and process operation. Laboratory and field test results are presented. The main purpose of the intelligent system is to help operators in making the correct decision in contingency situations, in an effort to avoid problems and production losses.

Introduction
In a well production system which includes the process plant, the oil/gas well itself with production devices, disturbances that produce oil and gas load disconnection or other emergency situations have to be localized as quick as possible. To localize a disturbance quickly and exactly is extremely important to start the process plant reconfiguration to restore normal oil and gas production. Moreover, variations of oil and gas production parameters normally indicate abnormality situations in the well production system.
However, the identification of the faulted points in that system is not always an easy task which frequently delays the start of correction procedures. It usually occurs when the protection system does not behave as expected.
The petroleum process plants in commissioning phase or even ones already in operation with complex constructive and operational natures, they have high incidence of failures in their protection system. On those plants, disturbance localization can take a long time due to a great amount of information to be analyzed, even visual inspection can be required. The difficulty and the time necessary in order to identify faulted points significantly increases in non-conventional process plants and wells.
The present paper describes the main characteristics of algorithms here proposed to identify faults and to make diagnosis in a process plant and well production (Patricio, 1997). Symbolic neural nets are used for fault diagnosis and control the well production. Finally, results collected from the field at different operational conditions are discussed.
Stochastic Models for Reservoir Characterization : A User-Friendly Review
Authors: Galli A. , Beucher H. 
Published: December 2007

Abstract
Stochastic models are widely used in the petroleum industry for reservoir characterization. Although there is now an extensive literature on the subject either presenting new models or revisiting older ones, most of these papers have been written with the professional geostatistician in mind. This makes it rather difficult for potential users to understand the methods and to work out their strong and weak points. This paper reviews the broad families of stochastic models that are currently available from a practical point of view. Users are faced with a number of questions like whether to use pixels or object based methods, or how to incorporate various type of information. These points will be addressed in this paper.
Effect of Coiled Tubing (CT) Initial Configuration on Buckling/Bending Behavior in Straight Deviated Wells
Authors: Qiu Weiyong , Miska Stefan , Volk Len 
Published: December 2007

Abstract
Current sinusoidal and helical buckling models are valid only for initially straight CT. This paper stresses the effect of the initial CT configuration (residual bending) on sinusoidal and helical buckling in straight, deviated wells. Using the conservation of energy and the principle of virtual work, new general equations are derived for predicting the sinusoidal and helical configurations of CT. Practical examples are provided to show the effect of the initial amplitude, hole inclination angle, and size on sinusoidal and helical buckling behavior of CT with residual bending. The effect of residual bending is important for predicting the axial force transfer, stresses along pipe, the maximum permissible axial force for sinusoidal configuration, and the least axial force to produce helical configuration. These new equations reduce to those previously published when the initial pipe configuration is straight.

Introduction
Current sinusoidal and helical buckling models1,2,4–9 assume that CT is initially (stress free) straight, lying on the low side of the wellbore. However, this assumption is not always satisfied in actual drilling operations. Minor initial curvature is present in all real CT. It is therefore desirable to investigate the buckling behavior of CT with an initial curvature. In our preliminary study1 we investigated the effect of this initial curvature on the imperfect column. Fig. 1 shows a free body diagram of a pipe with initial (stress free) curvature (1/R). The load-deflection curves for such a column are shown in Fig. 2 for pin-pin type end conditions. The deflection variation at the mid-span with a load ratio P/PE (actual axial load/critical load) is plotted for two different values of the initial radius of curvature (R=150 ft, and R=75 ft). Examination of these curves reveals that bending begins as soon as the load is applied. The deflection increases slowly at first and then more rapidly as the ratio of the applied load to the critical Euler load increases. Clearly, a pipe with a small radius of curvature deflects considerably at loads well below the Euler load whereas a pipe with a large initial radius of curvature does not bend appreciably until the load is fairly close to the critical Euler load. Therefore, it is reasonable to expect that the initial curvature of CT may affect the buckling/bending behavior. In this study, we focused on the effect of the CT residual bending on the buckling/bending behavior in straight, deviated wells. In order to attack this problem, we used the energy approach.
Slag Cementing Versus Conventional Cementing: Comparative Bond Results
Authors: Silva M. G. P. , Miranda C. R. , D’Almeida A. R. , Campos G. , Bezerra M. T. A. 
Published: December 2007

Abstract
The first publication on the use of slag as a material capable of substituting the traditional Portland cement in well cementing appeared in 1991, when it was seen that it could be added to drilling fluid and solidify it with some advantages over traditional methods.
As a result, only recently, the use of this emerging technology has been suggested for situations where difficulty in removing the drilling fluid mud cake has been expected, as in HP/HT wells, for example. In this case, the practical rules for a successful cementing operation cannot always be implemented.
As these high temperature wells are fundamental to the exploitation of important Brazilian fields, it was decided, as one of the strategies for overcoming the difficulties in obtaining good cementing results, to invest in evaluating the performance of the slag-mix technology.
An extensive research project has therefore been conducted in a large-scale wellbore physical simulator, with the principal objectives of investigating the ease or difficulty of mixing the slag-mix and to evaluate the bond quality obtained after cementing and acidizing the well. Thus, the object of the present paper is to investigate the performance of slag-mix slurries under three distinct scenarios: cementing surface casing; cementing production casing at medium temperatures; and cementing production strings at high temperatures. The resistance of the set slurry to the attack of HCl / HF is measured in a physical simulator under static and dynamic conditions.