bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Second Pressure Derivative for Automatic Model Identification in Well Test Analysis
Authors: Bourgeois Marcel J. , de la Combe Jean-Luc Boutaud , Ajjoul Mohamed
Published: December 2007

This paper deals with automatic model identification in the analysis of pressure transients. The choice of the model, sometimes called diagnostic, is one of the first steps in the interpretation process, and it is important as it affects the values of the parameters deduced from the match.

This diagnostic is traditionally based on the shape of the derivative, plotted on a log-log scale. The shape of this derivative can be described with the second derivative, which is defined as the slope of the conventional derivative on a log-log plot. This second derivative can be computed and coded after smoothing, filtering and segmentation of the measured data. Several reservoir models can then be proposed, as they are chosen in accordance with the data base of previously interpretated well tests.

This 3-year project was ambitious as its goal was to recognize not only the usual models with a characteristic signature, but also those which the interpretator would sometimes overlook.

Introduction

Diagnosing all possible reservoir models from a pressure derivative curve is not a simple task, and automating this aspect of a pressure transient analysis is understandably attractive. This paper describes the development of such an automation technique, using the second pressure derivative curve prior to parameter estimation.

The listing of possible reservoir models corresponding to the measured response will sometimes remind the user of some models or combinations which are not common or straightforward.

Methodology

The main difficulties in the automatic analysis of real data, especially using the pressure derivative, are the separation of the true reservoir response from wellbore or gauge effects, and then to associate the signal to a known reservoir model. To do so, the following steps are followed:

1) Preprocessing of data

The data are considered to be a distribution of points, which are smoothed with a function passing through them so as to minimize the differences between measures and approximation. This is the ((diffuse approximation)) approach. This function is filtered with a low-pass Butterworth filter of order 2.

2) Segmentation of the second derivative

This step is performed with a split and merge algorithm. It should be robust, but still exact enough to detect even incomplete or short reservoir responses.

3) Coding

This segmentation is then coded in alphabet-attributes to establish the relationship between shape description and knowledge of about 30 base models. Finally, this coding is split into one, two or three coherent subsets to enable the correct interpretation (well, reservoir, boundaries) as a composition of the base models.

P. 959
Seabed Rawwater Injection : An Alternative Pressure Maintenance System
Authors: Waite R. J. , Eden R. , Cousins A. R.
Published: December 2007

Extended Abstract

Introduction. In the search for improved value from their offshore developments, oil companies have focused on a number of technology initiatives aimed at reducing facilities costs. One such initiative focuses on the use of raw seawater injection for reservoir pressure maintenance.

Traditionally, seawater undergoes significant and costly treatment prior to injection; typically this involves deoxygenation and dosing with various combinations of free chlorine, other organic biocides and corrosion inhibitors.

A number of oil companies have, in recent years, questioned the need for such treatment, suggesting that untreated, raw (but chlorinated) seawater could deliver adequate reservoir pressure maintenance at significantly lower cost.
Comparison of Perforating and Notching a Horizontal Wellbore for Hydraulic Fracturing
Authors: Underwood Porter J.
Published: December 2007

In horizontal well fracturing operations, minimized wellbore entry to the formation improves fracture placement and enhances production response. Generally, operators most commonly jet-perforate along a 1- to 5-ft interval to connect the wellbore with the formation, but a new method is available in which water-entrained sand is used to notch the casing. Slurry is then pumped through a jetting nozzle to complete the operation. To compare the two processes, operators performed an eight-stage fracturing treatment in which alternating stages of conventional jet-perforating and treatments with the newly designed jetting tool were both used.
Oil Recovery in Fractured Oil Reservoirs by Low IFT Imbibition Process
Authors: Al-Lawati Shabir , Saleh Saad
Published: December 2007

This paper presents the results of an experimental study performed to investigate the effect of reduced interfacial tension (IFT) on oil recovery by spontaneous imbibition and gravity segregation. The results of the static imbibition experiments, in which a matrix block was surrounded by the imbibing fluid, showed that a minimum Bond number (NB-1) was required to increase the final oil recovery. However, the reduction of the IFT may increase or decrease the rate of imbibition substantially depending on the relative contribution of capillary and gravity forces. The results of the experiments performed on three ranges of permeabilities with four different surfactant solutions (different IFT values) showed that imbibition can occur in three different regimes: capillary dominated, gravity dominated, and a regime in which both forces affect the imbibition process.

In order to examine the effect of IFT on oil recovery on the same core, core wettability has to be restored after each test. Several cleaning procedures were investigated to reproduce original core wettability. As an outgrowth of this research, a core cleaning technique for restoring core wettability has been suggested. Firing the core after toluene cleaning for seven hours at 950 F was found to be an effective procedure to restore core wettability after solvent extraction. The same procedure also proved effective for restoring the original core wettability after surfactant solution imbibition tests.

Imbibition has been recognized as an important factor in recovering oil from water-wet fractured reservoirs subjected to waterflood or water drive. Water imbibition is the process by which water flows into porous media by capillary forces. These forces allow the water to flow from the fractures into the water-wet, oil-saturated matrix blocks, which causes the oil to be displaced from the matrix into the fracture. Unfortunately, water imbibition is inefficient in recovering oil, often leaving more than half of the original oil-in-place unrecovered.

A static imbibition by surfactant solution imbibition process recovers residual oil by reducing the surface forces between the oil and the imbibing fluid. On the other hand, by reducing the interfacial tension, the capillary forces that cause imbibition are reduced.

Objective:

The objective of this static imbibition work is to investigate the effect of reducing IFT in different oil/water/rock systems on final oil recovery.

Methods of Investigation:

Sets of experiments were performed by using a specially designed static imbibition apparatus. Each experiment consisted of exposing an oil-saturated Berea sandstone core to water imbibition (base case), cleaning and saturating the core with the same oil, and exposing it to surfactant solution imbibition. Oil recovery by water and surfactant solutions imbibition from each core are compared.

P. 107
A New Approach to P/Z Analysis in Abnormally Pressured Reservoirs
Authors: Guehria Fawzi M.
Published: December 2007

Future performance of gas reservoirs can be predicted if one identifies the main drive mechanisms and the original gas-in place. The extrapolation of the p/z versus cumulative gas production plot is a commonly accepted method that is used to estimate original gas in-place in volumetric gas reservoirs.

However, abnormally pressured reservoirs usually exhibit initial pressure gradients in excess of 0.65 psi/pt at depths greater than 10,000 ft. As a result, in addition to fluid expansion, gas is produced by sand grain expansion, rock compaction and water expansion. As formation compressibility approaches gas compressibility, the standard p/z curve tends to bend downward, making "straight line extrapolation" questionable. To account for this compaction phenomenon, some authors suggested to modify the material balance equation by incorporating constant pore and water compressibilities.

Unfortunately, by assuming a constant pore compressibility, the original gas in-place can be overestimated by as much as 60%. These errors are caused by pore compressibilities continually changing as fluids are withdrawn and as pressures decline to a normal range. To overcome this shortcoming, we propose to rigorously account for the variation of pore compressibility with pressure.

Assuming that pore compressibility as a function of pressure is available, a straight-line method which allows estimation of original gas in-place is presented. If pore compressibility is not readily available, we show that by adopting simplified models for pore compressibility versus pressure, we can regress on measured gas production versus reservoir pressure data to obtain initial gas in-place and parameters for pore compressibility model. Regression is performed using a public-domain Levenberg-Marquardt algorithm, and the model parameters are constrained using simple previously-published algorithms.

We demonstrate the validity of our approach by considering synthetic data from a finite difference simulator. We also successfully apply our analysis to data from two abnormally-pressured fields.

Introduction

The observed behavior of abnormally pressured reservoirs has been discussed in the literature.

P. 249
World Wide "Tier" 3 Response
Authors: Neilson D.E.
Published: December 2007

Tier three response to major incidents is not a common occurrence. However when this level of response is required it must be swift and seamless. Oil spills that need an international response may not always be large, location and lack of infrastructure my be some of the main drivers. If a Tier 3 response is not carried out quickly the effort required and the consequences increase. This paper discusses the issues to be overcome and methods to bring about a successful Tier 3 response.

"Tier" 3 Response

The term has two possible meanings. One, that is normally used within the United States and one normally used through out the rest of the world. The US interpretation would be a level of response to counter a worst case spill within an organisations response planning standards. This would be a situation that required cascade of extra response equipment from "out of region" equipment stockpiles. The international understanding is similar. The incident would be one that out striped the local "Tier" 1 and regional "Tier" 2 capabilities. The situation would then require international assistance. As already stated, international assistance may well be required because neither Tier 1 or Tier 2 capabilities exist at, or near the spill location. (Fig 1)

Key Requirements

The key requirements of a Tier 3 response organisation are :-–To provide an effective response world-wide–Hold well maintained state of the art equipment (suitable for air transportation).–Able to provide highly trained, self motivated staff.–Retain a logistical capability.

As with most successful organisations an effective Tier 3 response facility will have suitable equipment and well trained, motivated staff. People are the key to making things work. Tier 3 response organisations have to function in many differing geographical regions. Often, with little support infrastructure. Climate, language, certain political and cultural differences all have to be understood. Equipment that Tier 3 organisation hold normally requires to be air transportable. The selection of equipment for such organisations requires the careful consideration of a number of factors. Size, weight, suitability for different spilled oil characteristics and maximum possible recovery efficiency, all have to be considered during this process. A successful Tier 3 organisation must maintain a high level of logistical capability with a heavy focus on aviation.

Emergency Response

If the response to a Tier 3 oil spill incident is not carried out swiftly and effectively, the consequences for companies can be far reaching. The ability to provide a successful response becomes difficult. The effort and therefore cost to the company increase tremendously. The consequences and damage to the company image can be catastrophic.
Solvent Stimulation of Viscous Crude-Oil Production
Authors: Gates G.L. , Caraway W.H.
Published: December 2007

To improve both the rate and volume of production of viscous crude oils, the USBM made a production of viscous crude oils, the USBM made a study of solvents to stimulate production. Five laboratory methods were used to evaluate the effectiveness of several solvents in the stimulation of viscous oil production. These methods were (1) viscosity reduction, (2) gravity drainage production from sand columns, (3) displacement from capillary tubes, (4) effect of organic acids on crude oil viscosity and (5) hydrocarbon analysis. Solvents ranging from refinery cuts to chemical compounds were used with six California and one Kansas crude oils. Results indicated that small quantities of effective solvents greatly reduced the viscosity of viscous crude oils. The rate and volume of production of viscous crude oils by gravity production of viscous crude oils by gravity drainage from laboratory sand columns were increased greatly by small quantities of effective solvents. It was also found that low molecular-weight aromatic-hydrocarbon solvents effectively removed viscous crude oils from glass capillary tubes.

Introduction

Because of the rapidly growing national demand for energy, a study was made by the USBM of improved methods for producing viscous crude oils. Previous USBM studies showed that over 100 billion bbl of viscous crude oil are present in over 2,000 petroleum reservoirs. present in over 2,000 petroleum reservoirs. California has the largest resource of viscous crude oil — about 75 percent of the oil classified as most favorable for recovery by stimulative methods. Exploration costs for viscous oils are almost nonexistent because the large reserves are in known fields where many producing facilities already exist. Interest producing facilities already exist. Interest in the viscous crude oil resource has been enhanced further by the development of high-yield hydrocracking refinery processes to convert low cost viscous crude oils into valuable fuels. Some hydrocracking processes yield up to 80 percent volatile fuels from viscous oils. percent volatile fuels from viscous oils. In this study, methods of evaluating solvents were examined in the San Fracisco Energy Research Laboratory, and the results obtained using viscosity reduction, sand columns, capillary tubes, addition of organic acids, and hydrocarbon analysis are described.

Previous Related Work Previous Related Work A review of published information (1958 to 1968) showed that stimulation of the production of viscous crude oils in California has been improved by the addition of steam to the reservoir. Stimulation of production of viscous crude oils has been obtained by injecting large quantities of steam to heat the oil above normal reservoir temperature. Improved production by the addition of heat to decrease the viscosity of crude oil in the reservoir has been outstanding in the Kern River field of California where production has increased from 9,500 bbl a day in production has increased from 9,500 bbl a day in 1950 to 70,000 in 1970.
The Fastest Way to the Bottom: Straighthole Drilling Device - Drilling Concept, Design Considerations, and Field Experience
Authors: Ligrone A. , Oppelt J. , Calderoni A. , Treviranus J.
Published: December 2007

The Fastest Way to the Bottom: Straighthole Drilling Device - Drilling Concept, Design Considerations, and Field Experience A. Ligrone, SPE, AGIP S.p.A., J. Oppelt, SPE, Baker Hughes INTEQ, A. Calderoni, SPE, AGIP S.p.A., J. Treviranus, Baker Hughes INTEQ

A straight top hole section in many cases is a strict requirement to be able to drill deeper sections with complex well geometries. Especially in an environment where the geological parameters tend to deviate the course, and if the hole stability is a risk, drilling of a straight surface portion of hole is a must. Conventionally, this will be achieved by applying steerable motors and changing between sliding mode for directional changes and rotary mode to drill straight ahead. The Straighthole Drilling Device, SDD, has been developed as a fully automated instrumented downhole motor with integral expandable ribs to steer a permanent vertical well path without any supervision required from the surface operator.

This technology had first been verified through long-term continuous application in the KTB ultra deep scientific well bore in Germany, which was drilled solely for scientific purposes. Only through consequent application of the automated vertical steering could the very critical hard rock formation be drilled with minimum deviation and dog leg severity, thereby exceeding the 9,000 meter goal.

Today, the basic technology has been converted into a highly durable drilling tool to be applied in commercial oil wells. The first part of this paper will be a description of technical concept, details and performance features of the Straighthole Drilling Device. The second half will emphasize drilling experiences. AGIP has identified some fields in the south of Italy as ideal candidates to prove both the technology and the economic benefits of SDD. The main idea is to drill quickly a straight and vertical top hole section without the need to ream the hole as is required with traditional methods. Field results from southern Italy are reported.

Introduction

Early need for an automated guiding device for straight vertical boreholes occurred in the mining industry during the late 70's. Up to then the state-of-the-art had been to operate passive devices to maintain the direction of a borehole, such as large-diameter, ultra-heavy drill collars. Such means utilize the earth gravity force and a tight annular gap to guide the direction of the borehole as close as possible to the anticipated course. Since, in many cases, the natural forces of the formation dip could not be overcome in this way, the concept of active steering devices was investigated with special focus on providing a vertical borehole course.

Such development activities were all limited to shallow wells of a few hundred meters depth until the management of the "Continental Deep Drilling Program" (KTB) adopted the same concept for their ultra-deep scientific borehole in 1989.

P. 115
The Future Of West Coast Energy And Oil
Authors: Carlton C.J.
Published: December 2007

World wide trends of oil supply demand, prices and pollution control regulations all have a bearing on the oil pollution control regulations all have a bearing on the oil deficient West Coast. Even more directly, the changing energy situation in the U.S. and increasingly stringent environmental controls affect the West.

With decreasing gas availability, demand for low sulfur oil to meet pollution requirements will grow. The whole oil industry will be feeling the necessity for change as it seeks to serve this changing market pattern.

Introduction

In 1947, the first gas came to California from Texas and New Mexico. This started a whole new era in which California and the West Coast has changed from energy exporters to energy importers. Up until that time, there had been ample gas in California for its own use. Hydroelecyric power had been the principal source of electricity with fuel oil supplementing where necessary. And California and the whole West Coast were oil exporters to other parts of the world. Today, we have a very different picture. We now bring in huge quantities of gas from Texas, New Mexico, and Canada. We bring in large volumes of oil from Canada and from overseas. Hydroelectric power has faded into a small percentage of total energy use.

This switch of the West Coast from being an energy exporter to an energy importer has a special significance when we view today's worldwide energy and oil situation.

This year, the world will use about 107,000,000 barrels a day oil equivalent of energy. By 1980, it will be about 175,000,000 barrels a day - nearly five times the amount it was in 1950.
Application of Stacked Template Structures Offshore Indonesia
Authors: Landeck Chris R.
Published: December 2007

The successful application of unique structures offshore East Kalimantan, Indonesia has formed a key element in a strategy of aggressive exploration and rapid exploitation of small discoveries in the area. This paper describes the development of the Stacked Template Structure design and the first two installations.

In July 1995 the Scguni Field was discovered with the drilling of the Seguni #1. The discovery well was located 12 km offshore Balikpapan, East Kalimantan, Indonesia, 4 km from the Scpinggan Field in a water depth of 105 ft.

Upon initial consideration the value of the Seguni prospect was enhanced by its shallow water location close to infrastructure offered by mature producing operations.

The size and shape of the prospect was not likely to produce a significant enough discovery to justify development using a conventional wellhead platform. The use of a large diameter driven caisson would not allow the use of a preferred riscrlcss drilling technique. The complexity of the reservoirs in the area and frequent intervention requirements made subsea development unattractive.

With this in mind, a unique Stacked Template Structure (STS) was conceived and designed prior to and during the drilling of the Seguni prospect. The first STS allowed the Seguni Field to be developed and placed on production with a total of four wells only eight months after confirmation of the discovery.

A second STS of slightly modified design was installed in 154 ft of water at another discovery offshore East Kalimantan in May 1996. This STS allowed the first development well to be spudded 34 days after spudding of the exploration well which justified the project
An Approach for the Selection and Design of Slim Downhole Motors for Coiled Tubing Drilling
Authors: Sanchez Alfredo , Samuel G. Robello , Johnson Philip
Published: December 2007

Recent advances in coiled tubing drilling have opened new applications for slim holes, in particular, high-angle, extended-reach horizontal wells drilled with downhole motors. This has created a need for high performance drilling engines. The present study covers torque and flow rate requirements based on the geometry of these wells. It shows how "slim" these motors can be and still satisfy the power requirements at the available flow rate. The analysis is supported with practical examples. Positive displacement, turbines, and electric motors are covered. Comparisons based on performance are also presented. The motors' compatibility with coiled tubing systems is also discussed.

The modeling reveals that the available downhole motors are capable of producing more torque than is actually needed for drilling horizontal holes. It is therefore possible to have slimmer motors whose lower torque is still sufficient.

Background

The use of downhole motors to replace conventional rotary drilling has increased over the years, and its performance has been the focus of research in recent years. The use of coiled tubing to drill horizontal, slim holes has also increased the use of these motors. Currently there are three types of downhole motors: turbines, positive displacement (PDM), electric. Even though turbine downhole motors were introduced to the United States in 1960, their use has been limited to less than 1% of the total footage drilled. The positive displacement motor (PDM) has been the downhole motor of choice in the United States since 1968. Electrical downhole motors are less common than turbines and PDM's and have been mostly used in the Soviet Union. In 1976 General Electric (in a joint project with the Energy Research and Development Administration, ERDA) developed and tested an electric type downhole motor built by General Electric, the main contractor. The project was later abandoned due to non-technical reasons.

Among the most important characteristics to consider when selecting or designing any of the three motors mentioned above are: size (outside diameter), torque output at the bit, and the availability of power to drive them. The power available to turn the motor becomes more important when using a turbine or a PDM because it depends on the hole cleaning requirements and on erosional velocities. Insufficient flow rates could result in inappropriate cuttings transport, while excessively high flow rates (mainly when drilling with air) could cause erosion problems. In this study, torque, horsepower, and volumetric flow requirements are used as criteria for modeling the design and selection of slim downhole motors to be used in drilling horizontal (short radius), re-entry wells using coiled tubing. The configurations considered are schematically shown in Fig. 1.

In estimating torque requirements it is necessary to consider the characteristics of the formation being drilled as well as the mechanical behavior of the bottom hole assembly (BHA).

P. 197
Methodology of IPR Study for Steam Stimulation Horizontal Well
Authors: Liu Huiqing , Wu Xiaodong , Zhang Qi , Liu Shumin , Harris H.G.
Published: December 2007

Steam stimulation well shows much difference production performance with conventional well. An extensive inflow performance relationship (IPR) for steam stimulation well was obtained by regression based on the thermal numerical simulation. It has been shown that the amount of energy injected and horizontal well length play an important role. Two stages appear about reservoir pressure performance in the production period, joint is at the point where cumulative production to injection ratio is unity; maximum production rate shows two stages, joint is at at the point where ln (Xd) is 0.003. For the same amount of energy injected, production performance is almost identical. Well performance become better as the horizontal well length increase for a specific drainage area. The new IPR equations have been successfully tested through a numerical simulation running and applied in artificial lift designing of two oil fields in China.

Introduction

Although steam stimulation has been successfully used in heavy oil reservoir for decades, there exists unsolved problem in well operation designing, no suitable IPR equation is available for this kind of well. As the progress of horizontal well drilling, horizontal well with steam injection makes this problem more complex.

Several authors have made studies on IPR. In 1968, Vogel developed a famous IPR equation, this equation states the relation between dimensionless bottom-hole pressure and dimensionless production rate for solution gas drive reservoir, reservoir is under the steady state. Reservoir pressure and maximum production rate are constant and can be known with the help of well-test operation. However, this equation can not be used in artificial lift designing for steam stimulation well due to the limitation of well-test operation, reservoir is composite after steam injection and is under strong unsteady state. Obviously, it defies the Vogel's guidelines, reservoir pressure and maximum production rate are definitely changing in the production period. So, the purpose of this work is to extend Vogel's equation, including to construct the relation between reservoir pressure or maximum production rate and recovery; energy injected and horizontal well completion length will be involved. With the same way, water-cut and liquids temperature changing relations can be found also.

Brief of IPR Study Method

The following simplifying assumptions have been made:Reservoir is horizontal, with no dipping, both of upper and bottom cap rocks have no difference;There is neither gas cap at the top nor free gas inside the sand and no hydrocarbon distillation occurs, oil viscosity reduction is a principal mechanism;Fluid saturation are uniform throughout the reservoir, steam stimulation is in the first cycle;A specific (X type) water/oil and gas/oil relative permeability curve and no temperature dependent was used;No capillary pressure effect was involved;

P. 887
Re-Engineered Formation Evaluation Suite Brings Higher Efficiency to Wireline Logging Operations in South East Asia
Authors: Sibbit A.M. , Nelson R.
Published: December 2007

A new wireline combination tool called PLATFORM EXPRESS integrates sensors traditionally used for formation evaluation into a short, highly reliable and efficient wireline logging system.

The sensors of the conventional triple combination logging string (density, neutron, resistivity and auxiliary logs) have been upgraded, re-packaged and re-engineered into a combination tool which is less than half as long, can be logged twice as fast and delivers better quality answers. The reengineering of the tool incorporates an accelerometer for real-time depth-matching, and improved pad kinematics for better quality log measurements in poor hole conditions.

In the following, we show case studies of the results of PLATFORM EXPRESS logs from the Asia Pacific region, comparing logging times with those of routine operations using conventional technology. A number of example logs are included to illustrate the benefits of the new logging system for improved wellsite data analysis.

Introduction

One of the objectives of logging is to provide continuous depth-indexed quantitative measurements of formation properties, in order to assist operators in making testing and completion decisions soon after drilling. In the last twenty five years, the combination of density, neutron porosity and resistivity log measurements together with auxiliary curves such as the gamma ray, spontaneous potential and caliper, has become the industry standard evaluation suite. With the introduction of computerized surface equipment and high-speed data transmission these measurements were combined into one logging string, the so-called 'Triple-combo'. Triple-combo's are available as wireline logging combinations or as logging while drilling ("LWD") combinations. In recent years the emphasis in the logging industry has been to improve the accuracy and resolution of individual sensors and to provide yet more combinations.

The PLATFORM EXPRESS is a radical departure from this trend. A combination string has been designed from scratch, integrating sensors into a shorter, more robust platform of inter-linked measurements. This change of approach not only yields benefits in terms of compactness and hence operational efficiency, but also generates improvements in data quality and interpretation.

P. 415
Novel Oxidizing Breaker for High-Temperature Fracturing
Authors: Shuchart Chris E. , McCabe Michael A. , Terracina John M. , Walker Michael L.
Published: December 2007

A novel oxidizing breaker system has been developed for fracturing fluids at high temperatures. Below 200°F, the system is not active, but above 200°F, the oxidizing system aggressively attacks the polysaccharide backbone of the fracturing fluids, resulting in a complete break of the crosslinked fluids. In the presence of a gel stabilizer, an intermediate, reactive oxidizing species is formed. The result of this formation is a delayed, soluble, high-temperature oxidizing system.

Controlled viscosity reduction at 200°F to 300°F in crosslinked gelled fluids with and without a gel stabilizer will be demonstrated. Testing included Model 50 viscosity profiles, high-temperature static break tests, and conductivity testing. Results from all testing showed the effect of oxidant concentration in producing apredictable, controlled break of the thermally stabilized crosslinked systems. Data were obtained in low-pH and high-pH Zr-crosslinked fluids as well as in borate-crosslinked fluids. The delayed mechanism of the new breaker system provides fluids with excellent crosslinked viscosity properties at early times with predictable, long-term viscosity reductions. Case histories show that the breaker system can be used throughout the treatment in the pad fluid, proppant-laden fluid, and flush.

This paper provides data that allow significant improvements in job design. The operations engineer can obtain predictable, controlled gel degradation by using the data provided for temperature, gel type, gel stabilizers, and breaker concentration. The results are optimized treatment designs with rapid fluid recovery, improved proppant-bed conductivity, and increased well productivity.
Core Damage From Crude Asphaltene Deposition
Authors: Minssieux L.
Published: December 2007

In order to study the flow properties of asphaltenic crudes, corefloods with an oil asphaltene content in the range 0.1% to 6.0 % weight, were systematically performed in various rock material.

These laboratory tests carried out at reservoir temperature, have shown evidence of core damage occurring under dynamic flowing conditions. Plugging effects due to asphaltene deposition were evaluated in each case through comparison with the reference oil permeability measured with a selected hydrocarbon, prior to and after crude flow. Chemical nature and amount of organic deposits found in-situ at the end of tests, were determined by means of the Rock-Eval pyrolysis technique. This method allowed both to characterize the asphaltene fraction in deposits and to determine their distribution along the core.

Core impairment resulting from in-situ asphalt accumulation, was found to cause a 20% to 90% loss of initial oil permeability, depending on rock morphology, mineralogy and crude asphaltene content.

It turns out that trends in permeability reduction related to asphaltene deposition exhibit clear similarities with formation damage caused by solid fines migration. So pore blocking mechanisms models which have been proposed to describe fines migration effects have been successfully applied to the results obtained with asphaltenic crudes. Such an approach leads to an interpretation of the more or less fast permeability reductions observed with the different couples (crude oil/rock material) considered in this work.

Introduction

Production problems related to asphaltene deposition generally appeared in the fields first in surface facilities, especially in separators, during the oil final depressurization step. Another critical point along the production chain is within tubing in which deposits form at depth corresponding to the bubble pressure of produced oil. Afterwards the asphaltene deposit zone can migrate to bottomhole and well neighbouring formation as reservoir depletion proceeds. It is the known and long story of Hassi Messaoud field.

However in some recent fields, well impairment has begun even in early stage of production and seems to concern the reservoir itself.

In vitro flocculation phenomenon and asphaltene precipitation have been the topics of many papers. But the effects in porous medium of asphaltene flocculation have just come under investigation.

Published work deals with experiments and observations carried out in micromodels. A few ones only were performed in sandpacks or cores, but with isolated asphaltenes redissolved into an aromatic solvent.

P. 401^
Performance of a New Biodegradable Ester Based Lubricant for Improving Drilling Operations with Water Based Muds
Authors: Argillier J-F. , Audibert A. , Janssen M. , Demoulin A.
Published: December 2007

The development of new drilling technologies like extended reach drilling (ERD) or slimhole drilling and the reinforcement of environmental legislations require new adaptation of water based formulations. Good lubricating properties of the mud that would minimize any risk of differential pressure sticking of the pipe are of major impact on the efficiency of drilling operations.

A biodegradable and non toxic ester based lubricating formulation has been developed that significantly reduces torque and pipe drag. Efficiency of the lubricant has been confirmed by an extensive testing under strictly controlled laboratory conditions simulating actual drilling conditions. The lubricant is very efficient on many different water based formulations, even containing high content of salts or solids, cases where classical lubricants are usually poorly efficient. The ester based lubricant is also very efficient for low solids formulations used for slimhole drilling. It is readily dispersible in water based muds and does not affect mud rheology nor filtration behavior nor any other mud property; in some cases its addition may even improve the filtrate loss reduction. Furthermore this highly efficient additive is completely biodegradable and non ecotoxic. Field tests carried out in Africa, north sea and US have largely confirmed the laboratory results presenting, for instance, a torque reduction of more than 40%.

Introduction

Environmental constraints concerning drilling fluids require new formulations that are non toxic for replacing mineral oil based muds. Water based muds are good candidates but new drilling conditions (deep drilling, slimhole drilling, extended reach drilling, multilateral drains) rise specific technical problems in particular concerning lubrication and risk of differential pressure sticking. When drilling long sections of highly deviated wells large friction between the drill pipe and the wall will increase torque and power required to rotate the drill pipe and the stress on the drill pipe. It could also interfere with running the pipe in and out of the hole. As a consequence good lubricating properties of the mud will improve greatly drilling operation efficiency.

An joint research programme has been undertaken by IFP and FINA for developing a new performant and non toxic lubricant in order to increase drilling rates in operations using water based muds. The major goal set forward when starting the ester based lubricant R and D programme was to achieve superior performance combined with full ecological and human safety.

This paper describes extensive laboratory tests and also results from field tests showing the performances of the ester based lubricant for reducing torque and pipe drag when using water based muds. P. 539^
Numerical Coning Applications
Authors: Sonier F. , Besset P.
Published: December 2007

A recent paper presented last year described a two-dimensional-numerical coning model with radial symmetry. Its main characteristics were:

1. Fully emplicit models with respect to all variables by using the simultaneous solution of the different equations describing the multiphase flow.

2. Representation of wellbore boundary conditions which comes closer to expressing physical phenomena caused by end effects.

The model was checked by the simulation of several cases which had previously been studied on a physical model.

The simulation of actual field cases showed that the model was very efficient. This paper describes:

1. The simulation of an actual field case having a long production history. The geometric and influx characteristics production history. The geometric and influx characteristics of the well are in good agreement with a radial circular geometry. The model restores the production history very correctly.

2. An analysis of sensitivity to some poorly understood petrophysical parameters (capillary pressure, relative petrophysical parameters (capillary pressure, relative permeabilities, anisotropy) has been performed. permeabilities, anisotropy) has been performed.

3. The point arises of assessing the effect of built-in impermeable barriers which may occur in the porous medium as either horizontal or cylindrical screens in the vicinity of the well.

Introduction

Fitting field results with a numerical model usually requires a great many parameter adjustments. In the first part of this paper we describe how, in a field case where most of the paper we describe how, in a field case where most of the characteristics are well known, we have succeeded in recreating the production history while modifying only the following parameters: parameters:

anisotropy ratio

shapes of capillary-pressure and relative-permeability curves

and we describe their influence on the results.

The second part of the paper takes up the problem of well treating for the purpose of delaying the arrival of water or gas. Since the present coning model obviously cannot take into consideration the presence in the pay of a fluid used for well treatment, e.g. foam, polymer, gel, etc., we give an extremely rough diagram of this phenomenon by introducing theoretical barriers having zero permeability and infinite stability in time. This analysis could be conducted because we have at our disposal an accurate and efficient numerical coning model (the presence of an impermeable barrier does not increase calculating time, and less than one minute of CDC 6600 time is required to simulate each case).
Mud programs and drilling problems pertaining to the tertiary Clays and Shales, Norwegian Northsea
Authors: Siem I.
Published: December 2007

Problems encountered in drilling Tertiary clays and shales in the southern part of the Norwegian Continental Shelf and the mud system most frequently used in this area, are reviewed in this paper.

Severe viscosity problems frequently arise while drilling the top 10,000 feet of hole, which predominantly consists of clays and shales, and are the direct cause of several problems like swabbing formation; blocking of flowlines and shaker screens by very soft sticky clay; sticking of drill pipe; and bit and collar balling.

The viscosity problems are the result of lack of solids removal equipment, the dispersing type drilling fluid used which makes the solid separation more difficult, and the facts that the lower 5,000 feet of formation is overpressured, behaves plastically, and has a high montmorillonite content.

A salt solution base mud is discussed as an alternative to the commonly used lignosulfonate system. Hydration tests of formation samples in various salt solutions indicate that low density solid content in the drilling fluid might be controlled more economically by the use of a salt water base mud and centrifuges and fine screen shakers. To date mud properties have partially been controlled in the unsatisfactory manner of discarding old mud and making up new mud.

It is concluded that a saving of 25% on the cost of barite alone seems possible with a salt solution base mud. possible with a salt solution base mud. More important however, are the potentials for reducing rig time and potentials for reducing rig time and consequently cost.

Introduction

This study presents mud programs and drilling problems pertaining to the Tertiary clays and shales in the southern part of the Norwegian Continental Shelf (see Fig. I).
Trials of the Dynamic Positioning of a Drill Ship
Authors: Auberger J.F.
Published: December 2007

Introduction

Let us go rapidly over file sub-assemblies which compose the dynamic positioning system of a drill ship like the Pelican.

There are essentially four sub-assemblies:

a. a displacement detector of the acoustic position measurement system deducts the horizontal displacement of the ship in relation to its assigned point, from a series of measurements of the length of time of ultrasonic wave transmission between the bottom and surface.

b. dual digital computers having the following functions:

- pace the start of the subsea acoustic system;

- process the data from the acoustic position measurement system to deduct the position displacement;

- work out thruster commands to pass on to the propulsion system;

- check the performance of the parts of the dynamic positioning system and start off the alarms or switches in case of failure.

c. a back-up analog processing unit, using the position displacement system data supplied by a taut-wire inclinometer in order to figure the thrusts to pass on to the propulsion system.

d. a unit for auxiliary measurements, allowing the following data to be gathered:

- measurements directly involved for calculating, like wind direction and velocity, which are used in the control loop for a wind pre-correction;

- corrections of pitch and roll enabling the transmission time measurements to be adjusted to take into account the slope of the plane (in relation to the horizontal plane)where the hydrophones, installed on board, are located to receive the ultrasonic beams for displacement detection.
Stratigrafy Drilling in Deep Water With Aluminum Drill Pipes Application
Authors: Gelfgat M. Y. , Podrazhansky A. M. , Geise J. , Paff G.
Published: December 2007

This paper presents the experience gained with the use of special large diameter aluminum drillpipes (ADP) in the Atlantic Ocean, Norwegian Sea. Gulf of Mexico and Gibraltar Straight. The maximum water depth achieved was 1616 m. Both rotary and down hole motor drilling and coring techniques have been used for drilling and coring in variety of formations – from soil till hard rocks. Various types of retrievable tools are available to offer a spectrum of possibilities.
Dynamic Anchoring and Anti-Heave Slide: Key Device for using Floating Supports on the High Seas
Authors: Delacour J. , Castela A. , Harbonn J.
Published: December 2007

To extend subsea oilfield exploration and exploration to greater water depths, work supports set on the sea-bottom must progressively be replaced by floating supports. Work efficiency progressively be replaced by floating supports. Work efficiency then requires the limiting and, if possible, elimination of movements imparted to such supports by the action of the elements, in particular drift, roll and heave.

Two systems have been developed to meet this objective:

1) Dynamic anchoring which cancels out drift and reduces roll by purposely positioning the support.

2) A surface slide which eliminates the effect of heave.

The operating principle of these systems and practical examples are described briefly in this paper along with the experience gained from using both systems together during the past seven years under a wide variety of operating conditions aboard the I.F.P. experimental vessel "Terebel". It is shown in particular that the great flexibility and adaptability, of these systems make it possible to do the most difficult - jobs on the high seas with remarkable safety and efficiency.

Introduction

The current search for new off-shore oil and gas fields in deeper and deeper waters and the commercial exploitation of these fields have set a trend for the progressive replacement of work-platforms set on the sea-bed by floating supports: ships, semi-submersibles and the like.

Increasing water depths and more hostile seas such as the North-Sea or the ice infested Labrador offshore have made it necessary to use less cumbersome and more efficient mooring systems and to drastically improve platform stability, by reducing such motions as surge, sway, yaw, heave, roll and pitch. pitch. Two devices developed during these last years have gone a long way towards meeting these requirements:

1) Dynamic Positioning, which has solved the difficult problem of fast and safe anchoring in deep waters and which problem of fast and safe anchoring in deep waters and which has brought a Feat improvement in stability by allowing the floating support to head permanently towards the on-coming seas, thus reducing considerably the roll motion.

2) The Heave Compensating Device, which has greatly reduced the vertical motions of any piece of machinery being handled from a floating support.

As early as 1963, the "Terebel", a 900 metric tons experimental vessel of the Institut Francais du Petrole, was outfitted with dynamic positioning and a heave compensator.

This paper describes sonic of the work done by the "Terebel" and how dynamic positioning and heave compensator have made it possible to carry out some operations with relative ease which, otherwise, would have been very difficult, if not impossible.