bluuebunny/crossref_metadata_2025 huggingface dataset:
The Benefits of Integrating Different Information Disciplines
Authors: Bigelow E.L.
Published: December 2007

The technical and economic benefits of integrating different information sources is well founded. It is important that drilling, well completion, and production personnel be included in such task forces if optimal information gathering is to be accomplished. The pulling together of people and data from several information disciplines, and utilizing individual strengths, while learning to accept specific weaknesses as such, leads to a cooperative team effort in resolving difficult reservoir characterizations.

Introduction

As our proven oil and gas resources diminish. and new sources become more difficult to find and produce, technology in virtually every inflation discipline has demonstrated dramatic advances. Despite the technical improvements, there are many cases where individual disciplines continue to achieve only marginal success. Too much impetus is directed toward self-promotion of a particular information discipline, and too often competitive disciplines are criticized for their particular weaknesses.

Combining the attributes and strengths of different disciplines, and recognizing where each have inherent weaknesses leads to much more accurate analysis of subsurface real estate. When petroleum reservoirs are found with fewer exploration wells. and when accurate analysis of all the available information is utilized to appraise and describe newly discovered reservoirs, oil company economics is drastically improved. Case histories show:

- the positive aspects of using both seismic and borehole data to establish the size and location of a potential reservoir.

- the use of well logs, seismic, and borehole seismic methods to define the size. shape. and internal characteristics of a newly discovered reservoir, and

- the capability of planning and implementing the most economical and technical extraction of discovered reserves. Total integration of both surface and borehole data and personnel is cost-effective and leads to more effective reservoir evaluation. Effectiveness of information gathering is enhanced when drilling, well completion, and production personnel are made aware of the difficulties some procedures cause for the different information-gathering disciplines. Reconciling procedures before a problem arises is beneficial for all.
Coiled Tubing Applications in the Sultanate of Oman
Authors: Al-Harthy Salim Said , Kalam Mohammed Zubair
Published: December 2007

The use of coiled tubing (CT) drilling technology is rapidly expanding and its important to note that the technology is still in the process of testing its boundaries and limitations. However, this is a necessary phase in the learning curve. Probably the most logical approach is to consider the market or application niches best suited to coiled tubing drilling technology.

Six horizontal sidetrack wells were drilled in North Oman using CT. The objective of these trials was to evaluate the technical and economical feasibility of this drilling technique. For all the six wells, the existing completion was removed from just above the upper packer and the remaining completion abandoned, then a window was milled in the 7 inch casing, allowing the well to be sidetracked using a whipstock, and built up through the formation of interest.

This paper discusses the three main problems faced during drilling these wells, and the suggestions for improvement. The problems discussed involves the following: difficulties in setting the whipstock, problems in cleaning the hole, and difficulties in handling the tubing. Whipstock types are discussed, and the one best suited for this type of application is recommended. A proposed schematic of a rig is shown to minimize the problem of handling the tubing for this type of application.
Advancements in SPOOLABLE Completions to Accommodate Wireline Operations
Authors: Gauthier Sammy , McGavern Cecil , Sides Winfield
Published: December 2007

The benefits of SPOOLABLETM completion systems have become more apparent as the technology develops. Advancements in the first generation of center-set spoolable products have led to the development of concentric throughbore and wireline retrievable technology. This technology includes such products as through-bore, surface-controlled subsurface safety valves, tubing-retrievable, concentric, gas lift valves and wireline-retrievable center set gas lift valves. The advantages of these products is the ability to perform wireline operations, including bottom hole surveys, well control and gas lift valve installation and retrieval through the coiled tubing without pulling the string.

This paper discusses the development and testing of these products along with manufacturing the system assembly and developing installation methods specific to spoolable completions. In addition, typical completion designs including options for hanging the completion and bottom hole seal assemblies are reviewed.

Issues such as helical buckling and residual bend inherent in coiled tubing installations affecting the ability to perform standard wireline operations in coiled tubing completions are discussed. Extensive wireline testing has demonstrated the ability to set and retrieve a gas lift valve through several spoolable completion products. The results and implications of these significant tests are detailed in this paper.
Elongation of Coiled Tubing During its Life
Authors: Newman K.R. , Sathuvali U.B. , Wolhart S.
Published: December 2007

Due to plastic bending at the reel and guide arch, coiled tubing (CT) elongates with each trip into and out of the well. Laboratory experiments, finite element, numerical and theoretical modeling were performed to determine the magnitude of this elongation. The elongation for loads above an axial transition load are permanent while the elongation for loads below this load can be removed by a bending cycle. Theoretical modeling shows that rotation of the CT in the well and axial loading while bending significantly increases the axial elongation.
Surface Characteristics of Coiled Tubing and Effects on Fatigue Behavior
Authors: Tipton Steven M.
Published: December 2007

The manufacturing procedure for coiled tubing induces different surface morphologies on the inner and outer surfaces. Since fatigue is a surface phenomenon, this can lead to different fatigue behavior at the two locations. This has been demonstrated in full-scale bending tests and in axial tests conducted on small coupon samples in closed-loop servohydraulic strain-control. Furthermore, service environments can cause localized defects on the outer and inner surfaces of coiled tubing, such as griding marks, corrosion pits, tool marks or injector block damage, which can have a first order effect on fatigue strength. However, it is demonstrated in this paper that there is an inherent tendency for cracks to initiate on the inner surface of coiled tubing. This tendency leads to the hypothesis that a "threshold severity" for external surface defects could exist, below which the fatigue strength of the tubing is not affected. Limited data confirm this hypothesis, and suggest that the severity could depend on the material grade.
Determining the Mechanical Properties of Coiled Tubing
Authors: Crabtree A. , Skrzypek H. , Wilde G.
Published: December 2007

Coiled Tubing is developing into a multi-talented work horse. Efforts to use the technology in high pressure deep wells, horizontal drilling and production logging require a better understanding of the mechanical properties of the tubing material. The basic design of any Coiled Tubing system causes the tubing to experience bending strains beyond the material's Yield Point when passing between the reel and the wellhead equipment. It is widely expected that such levels of cyclic straining will cause work softening of the tubing material. This paper describes a series of experiments to investigate the effects of plastic levels of strain on the Yield Point and Young's Modulus. A modified method of performing full body uniaxial tensile tests is described.

Further tests were conducted to demonstrate whether any evidence of anisotropy between the material properties in the axial and hoop directions could be found. The use of linear elastic theory to predict the stability of Coiled Tubing during well operations is acceptable in the presence of small degrees of anisotropy.
Using Coiled Tubing to Remove Silicate Scale from Geothermal Wells
Authors: Turton Simon D. , Courville Perry W. , Hewitt Patrick T.
Published: December 2007

Geothermal power plants use heat from the Earth’s interior to produce one of the cleanest sources of electric power currently available, but the production of geothermal fluids can be costly if large quantities of silica scale are deposited on production tubulars. This widespread problem significantly reduces the ID of the tubulars, thereby reducing the production rate of the well. Previously, scale removal techniques involved the use of a drilling rig and a combination of such mechanical tools as drill bits and mills. Rig-based methods, however, are expensive and time-consuming. This paper discusses the design, use, and evaluation of an alternative technique that includes a coiled tubing unit (CTU).

When compared to traditional rig-based scale removal techniques, coiled tubing methods offer several economic, environmental, and safety benefits.1 Specifically, the use of coiled tubing reduces job time because coiled tubing is faster to rig up/down and pull out of the well. From an environmental standpoint, well effluent and debris can be flowed through the flowline to the existing processing facilities; pits are unnecessary. Coiled tubing also provides a greater degree of safety and well control when operations are being performed on a live well.

In the case histories provided in this paper, three methods were used to remove scale. For the first method, the cleaning energy was applied by highly focused polymerized fluid jets, which were specially designed for the job by a computer program. This hydraulic technique can be performed on a live well, which results in additional savings over traditional methods. The steam production during cleaning creates the required annular velocities to remove debris from the well without the need for energized treatment fluids.

The second method consisted of a high-speed coiled tubing motor in combination with a flat-bottom junk mill. Although both mechanical techniques have been performed with varying degrees of success, both increased the geothermal production rates of the wells treated.

The third method involved the use of a silicate scale remover that was used between the slotted liner and openhole section. It was also used to treat the well when either of the first two techniques were slowed or stopped by particularly hard scale deposits.
Development & Application of Inline Connectors for Weight Restricted Offshore Operations
Authors: Reaper Alan
Published: December 2007

Cranage limitations in the North Sea have caused problems for coiled tubing operations for some time, particularly in the southern sector. This has been compounded by the increases in reel weights brought about by the trend towards larger tubing diameters, necessary to provide the desired pumprates and to cope with highly deviated wells. Until now, the options open were limited and all had practical and/or safety implications involving joining of tubing strings offshore by welding followed by radiography, or at least part of the operations being performed between the supply boat and platform. As a solution, in-line connectors for 1.5" and 1.75" OD Coiled Tubing (CT) have been developed which allows two ends of a previously split string to be joined on the platform by simply screwing the ends together before spooling on to a single reel. Once the connection has been made, the pressure and structural integrity of a single string is retained. The connectors are suitable for use in both conventional fluid or gas pumping operations and stiff wireline applications. The technology has now been proven offshore following extensive bench and full scale testing. This paper details the tools development plus the initial application in the North Sea.
An Advanced Coiled Tubing Control System
Authors: van Walsum Eric , Stakkeland Helge
Published: December 2007

A land-based coiled tubing rig with a Cyberbase workstation as its control station is currently in operation. The control system for this rig, including the distributed I/O and PLC networks, man machine interface, data acquisition and logging functions are described. Particular attention is paid to the digital control, automated drilling, tripping and safety shut-down functions. Benefits of the design include reduced cost, rig weight, rig up and tear down time and improved ergonomics for the operator.
Brent Field Reservoir Modelling: Laying the Foundations of a Brown-field Redevelopment
Authors: James S.J.
Published: December 2007

The Brent field was discovered in 1971. It is now a mature asset and, in order to increase oil and gas ultimate recovery, will commence depressurisation in 1997. The redevelopment of the field has been underpinned by extensive static and dynamic modelling studies. Developments in geological computing and the numerical processing power of reservoir simulation platforms significantly improved the quality of the Brent field static and dynamic models. The static models have been used for a range of studies including gas cap volumetrics and bypassed oil investigations. Their functionality provides significant scope for target sizing as a basis for selecting the appropriate reservoir access well technology.

Introduction

The Brent field, located 100 miles north east of Lerwick, Shetland Islands (Fig. 1) was discovered by well 211/29–1 in 1971. With total hydrocarbons initially in place of some 3.8 MMMbbl oil and 7.5 Tscf gas the Brent field ranked as one of the largest fields in the northern North Sea. Following 20 years of production remaining reserves are estimated to be some 400 MMbbl oil and 2.6 Tscf gas and in these terms the Brent field continues to rank as the largest field in the U.K. Sector of the North Sea.

The Brent field is a mature asset. Facilities comprise four platforms providing a total of 154 well slots. Oil export is via the Brent systems pipeline to Sullom Voe and gas export via the FLAGS line to St. Fergus. Production from the extensive West Flank area commenced in 1976 and by January 1997 cumulative production amounted to 1.6 MMMbbl oil, some 80% of anticipated waterflood ultimate recovery, and 3.2 Tscf gas. In order to significantly increase ultimate recovery through field depressurisation an extensive brown-field redevelopment project, costing 1.3 billion, was initiated in 1994. This is now reaching completion with depressurisation commencing in 1997 and low pressure operation in the year 2000. This project has extended the life of the field and increased ultimate recovery.

The redevelopment of the Brent field involved extensive static and dynamic reservoir modelling studies which will continue to guide reservoir management during depressurisation. This paper reviews the development of the current generation of static reservoir models and illustrates their use, not only as the basis for dynamic studies but also in delineating areas of bypassed oil and monitoring gas cap volumetrics.
Experience With a Global Optimisation Approach to Project Scheduling and Resource Allocation
Authors: Harding A. M. , Ponniah D. A.
Published: December 2007

In recent years there has been a growing trend in major projects towards considering the whole project life cycle and its costs. This analysis initially considered concept to commissioning, and later, particularly after Brent Spar, concept to decommissioning. Within this project life cycle, optimal solutions are sought. However, the field of optimisation still tends to focus on improving the performance of elements of the project or small subsystems within the project as a whole. An optimisation across the whole project life cycle is not normally carried out. This paper proposes a general system for such a global optimisation model, which will allow the whole project to be considered within a single optimisation. The strategy consists of a basic scheme for input to an objective function and the definition of its constraints. The objective function can map to a value relating to cost, time, performance or risk, allowing the most important criteria to be maximised or minimised. Other values not mapped to by the objective function can be used as constraints to restrict any detrimental impact to them during the optimisation. The size and complexity of a true globally optimising model is extremely large. If the model is to be able to optimise globally, then it must also be able to arrive at an optimal solution for a local optimisation problem. Therefore its suitability for optimisation is tested on project scheduling and resource allocation, a subsystem of the project. A new approach to modelling project schedule and resource allocation, which will allow the model to fit into the globally optimising model, is developed. Using examples from the literature, the performance of this model on specific locally optimising problems is investigated, using Monte Carlo random search. This, although not normally considered as being an efficient means of finding an optimum, was considered the best approach to initial investigation where the nature of the optimising surface is unknown. In particular, the model is used to solve resource constrained scheduling problems. The difficulty of finding the optimum within the model is also studied, and extensions to the model for further research are proposed.
The Subsea Well Decommissioning Project
Authors: Morrice B. , McGennis E. , Kirby S. J. N.
Published: December 2007

An important new initiative to clean up the seabed has resulted in a major project to decommission and remove redundant subsea wells. The subsea well decommissioning project was instigated by BP Exploration to fulfill its commitments and obligations under various license agreements. When exploration wells are no longer required for further appraisal or development, the requirement is to remove all subsea wellhead equipment and clear the seabed. This paper will describe first the organisation and execution of the project. It will then look at the experience gained and how it challenges the current well suspension philosophy.
Onshore Decommissioning - Receipt, Dismantling, Recycling and Waste Management of Offshore Structures Returned Onshore
Authors: Chaplin Paul D
Published: December 2007

The objective of this paper is to outline some of the issues, equipment and facilities which are required to enable the onshore decommissioning of offshore facilities once they are returned onshore.

It covers the receipt, materials, waste management, methods of dismantling, discussions on the form in which structures are likely to be returned and the requirements of the facilities onshore.
Future Developments in Subsea Autonomous Control Systems
Authors: Garbuglia E. , Calore D. , Guaita P.
Published: December 2007

The need for life cycle cost reduction to increase or simply to allow the profitability of a subsea development does not permit the extended use of conventional control technologies in scenarios more and more characterised by deepwater and long distance. The future subsea scenarios will probably see the development of fields beyond 20 km from the host facilities. The economic advantages of the introduction of autonomous control systems has been demonstrated in several studies. Some technologies have been designed and successfully tested and can today be considered as the valid starting point for any other future initiative. The recent developments in the acoustic transmission techniques through seawater, in the autonomous subsea power generation and in the subsea closed loop hydraulic systems, make now possible to eliminate the control and power umbilical in many subsea development with step-out distances up to 40 kilometres. With respect to the acoustic through seawater, the research efforts in the last years have led to more sensitive and efficient acoustic transducers and to more capable detection algorithms based on coherent demodulation techniques.

In this paper, an overview of these recent developments regarding the acoustic signal transfer is presented. Considering that the electrical power requirements increase with the number of functions and variables to be controlled and monitored, different solutions for subsea power generation are considered for different production scenarios. The progresses regarding the seawater batteries and the thermoelectric generators combined with the developments in the field of low power electronics allow now to satisfy the electrical power requirements in multi wells developments. In case of considerable amount of electric power, the feasibility of subsea turbines, powered by produced or injected fluids, was also demonstrated. Although autonomous solutions have been proven by means of prototypes their reliability is still to be demonstrated in order to gain the necessary acceptance by the oil industry. The next step will be the engineering of the existing prototypes in order to achieve devices suitable for real field scenarios.
Maximizing Profits from Exploration To Marketing
Authors: Oxford Robert J. , Shannon John E.
Published: December 2007

The natural gas industry is now in the midst of the most critical period in its history. The energy crisis in our nation offers the professional engineer a challenge that perhaps equals the opportunities of the engineers who pioneered the technology in the petroleum industry years ago.

The increasing need for clean-burning fuel by our expanding industry-oriented society requires that we be more diligent in our search for gas, more intelligent in our evaluation of reserves, and more innovative in our approaches to producing and marketing this valuable resource. For years, gas has been an enigma to the petroleum industry, from the lease operator, to the engineer, up to the highest level of management. The discovery and production of crude oil has been our primary goal. We have avoided the handling of gas production problems in favor of maximizing oil recovery. problems in favor of maximizing oil recovery. It has essentially been a matter of economics. Oil has generally been priced at values commensurate with the cost of exploration and production. Gas has had values up until this past year of six cents to twenty cents per thousand cubic feet, and in some cases, no relative value at all. Considered on an energy basis compared to the price of oil, gas should have been valued at over 50 cent per thousand cubic feet at the wellhead.

Engineering technology has begun to grasp the value of the total well stream and significant advances have been made in the production and treatment of gas. We have discovered that a cubic foot of natural gas has many uses and valuable components, just as a barrel of crude produces a variety of products. We must advise petroleum management of this value and assist them in a more vigorous search for gas and development of a broader perspective of its market opportunities.

It is not the purpose of this paper to discuss the technical aspects of gas engineering. We would like to stimulate your imagination with several questions we think are pertinent to the business of handling natural gas in the most profitable manner.
Increased Costs or Increased Profits - Is there a choice?
Authors: Ashraf J. , Vote R.
Published: December 2007

Pressures on the economic margins for offshore production have prompted efforts of reducing costs, usually at the most visual ‘Capital Expenditure’, and ‘Preventative Maintenance’. However, in most cases the lull effects of these measures are not assessed, and there is a real risk that perhaps for a short term gain that problems may arise later and potentially overwhelm the savings that were sought in the first place.

This paper outlines a strategy for increasing profitability in the offshore industry, which is just as effective for optimising existing assets as well as a decision making tool for future developments. This encompasses not only the traditional physical and environmental risk, but also the long term impacts of decision made for investment, design and operations. Hence, the most efficient business strategy can be evolved on a quantitative, rather than merely a qualitative basis.

The method developed is a user friendly menu driven hierarchical modelling system, that encompasses both engineering and economic inputs, which then captures the effects of varying influences on them.
Improvements in the Design of Water Shutoff Treatments
Authors: Hardy Mary , van Batenburg Diederik , Botermans Wouter
Published: December 2007

In the past, high-volume water-shutoff treatments have not been applied because of the economic burdens they incur. Today, many operators have reconsidered high-volume water-shutoff treatments because these treatments make oil production from mature reservoirs more economically feasible. Many wells in mature North Sea reservoirs produce a large amount of water. Consequently, these wells often produce less oil than they potentially could.

The evolution of diagnostic and interpretation techniques has significantly enhanced the degree of accuracy and completeness of production problem diagnoses. Reservoir models can be used to identify and design effective water-shutoff treatments. This paper describes how a production operation simulator is used with an advanced-processes reservoir simulator to design water-shutoff treatments. The following reservoir simulator options were necessary to design the treatments properly.–thermal options–chemical-injection options–chemical-reaction options–flexible-gridding options

The technique was recently used to design water-shutoff treatments and their placement for jobs in the North Sea area. The results of the simulations were used to predict the effects of the following factors.–interval permeability distribution–treatment rate–reaction rates of treatment fluids–resulting gel strength

The technique also allows treatments to be designed on the basis of realistic treatment temperatures rather than bottomhole static temperatures. The results of the simulations were used to optimize treatment placement rates, fluid composition, and shut-in times of jobs pumped in the Norwegian sector of the North Sea.

One case shows how cooldown inside the reservoir can be used to place a treatment that would have otherwise spontaneously gelled at reservoir temperature. Another case shows how temperature histories for different stages of the treatments were constructed from the simulation results. These temperature histories showed that different activator compositions and/or concentrations were required for early, intermediate and final treatment stages.

Introduction

Water production can seriously compromise the profitability of oil- or gas-producing wells. The cost of produced-water disposal is becoming a major burden for many operators. Although prevention is usually more effective than treatment, excessive water production is most often treated rather than prevented. The keys to the success of shutting off or preventing excessive water are:–proper identification of the water-production mechanism–appropriate design of the treatment–effective placement of the treatment

Steps of Typical Water-Shutoff Treatment

Figure 1 illustrates the process of a typical water-shutoff (or conformance) treatment. Each step of the process will now be discussed.

P. 611^
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

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

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

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

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

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

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

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

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

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.