bluuebunny/crossref_metadata_2025_split huggingface dataset:
Foundation Engineering For Gravity Structures In The North Sea
Authors: Schjetne Knut 
Published: December 2007

American Institute of Mining, metallurgical and Petroleum Engineers, Inc.
Discussion of this paper is invited. Three copies of any discussion should be sent to the Netherland Section of the Society of Petroleum Engineers, P.O.Box 228 The Hague, The Netherlands. Such discussion may be considered for publication together with the paper.

Abstract
The paper outlines the particular problems related to the foundation problems related to the foundation design of offshore gravity structures in comparison with structures on shore. The following aspects are dealt with in more detail:The current NGI method for overall foundation-stability on clay,the effect of cyclic loading on clay,the dynamic analysis of the soil structure system andplatform behaviour during the installation phase.

Introduction
Since 1968, when the Ekofisk oil field was discovered, we have witnessed a hectic activity in the northern part of the North Sea. Many oil and gas fields have been discovered, most of them along the borderline between the British and Norwegian sectors. (Figure 1) Several of the fields are now being developed and the Ekofisk field alone is already producing enough oil to cover Norway's producing enough oil to cover Norway's total petroleum consumption. Most of the fixed platforms installed have been the pile-supported steel jacket type, as developed in Lake Maracaibo and in the Gulf of Mexico. However, new types of structures have been developed, those today commonly known as gravity structures, i.e. structures sitting on the sea bottom by their own weight with no anchors or pile support.
The first gravity structure installed in the North Sea was the Ekofisk Tank in the summer 1973. It was a one million barrel oil storage, concrete tank designed by C.G. Doris (Figure 2).
Two years later, in the summer of 1975, three concrete drilling platforms were installed, Beryl A and Brent B, both the Condeep type designed by A/S Hoyer-Ellefsen and Frigg CDPL, another Doris design. At the moment there are 9 more concrete platforms under construction in the countries surrounding the North Sea (Doris 2, Andoc 1, Sea Tank Co. 3 and Condeep 3).
First of all because of the water depths and the hostile weather conditions in the area, the dimensions are huge compared to on-shore structures.
Environmental Aspects of Offshore Disposal of Drilling Fluids and Cuttings
Authors: McAuliffe C.D. , Palmer L.L. 
Published: December 2007

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.
This paper was prepared for the Improved Oil Recovery Symposium of the Society of Petroleum Engineers of AIME, to be held in Tulsa, Okla., March 22–24, 1976. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
Concern has recently been expressed that the discharge of drilling fluids and cuttings from offshore oil and gas exploration and production wells may cause adverse environmental effects. Laboratory studies using various organisms show these materials to generally be relatively nontoxic. Rapid dispersion and dilution, measured during discharge of drilling fluids and cuttings to seawater, explain the lack of long-term effects in areas with 20 to 40 years of petroleum operations. This indicates that offshore discharge is an environmentally acceptable method for disposal of drilling wastes.

Introduction
During the drilling of offshore exploration and production wells, drilling fluids and cuttings are usually discharged to the surrounding waters. This practice was followed at most of the 19,000 or more wells drilled to date in U.S. coastal and offshore waters.
With the accelerated OCS leasing program, concern has been expressed by program, concern has been expressed by some as to possible adverse effects of such discharges on marine life.
In this paper we review brieflydrilling practices,the composition of drilling fluids,bioassays conducted by Chevron Oil Field Research Company on selecteddrilling fluids,bioassays on drilling fluids and their components as reported in the literature,observations of marine life and measurements for chemicals and turbidity made during cuttings and fluids discharges,observations of marine life in areas where drilling has occurred for long periods of time, anda comparison of fluid and cuttings discharges with sediment inputs from rivers and storm-resuspended near shore and sea bottom sediments.
Acid Stimulation Studies in Simulated Radial Flow Conditions: Laboratory Results Compared With Field Data
Authors: Kotlar Hans Kr. , Hove Arvid O. 
Published: December 2007

Abstract
Most laboratory tests for qualification of acid stimulation treatments are performed in traditional core flow experiments. A single core, with all treatment fluids flowing through the core, in laminar flow pattern is used.
By such set ups the contact time to the matrix and the residence time of the spending acids will not be matched with the actual field conditions. Thus, it will be difficult to reproduce possible secondary and tertiary reactions. Such reactions might prove to be very important, especially in "dirty" sand with high clay content.
A survey done in the industry reveals that 1/3 of all acid stimulation jobs fail. This is due to various reasons. i.e. incorrect acid formulations as well as pumping schedule procedures, improper placement, specific field related problems with cross flow, etc.
The present paper reports on the first experiments in acid treatments using a multi-core set up simulating radial flow conditions. Furthermore, this is done in combination with two-phase flow.
These experiments are using actual pumping and treatment schedules from the Gullfaks field. The results are compared with the actual field data.
The spent acid flow back, representing the total acid injection volume, is analyzed for dissolved elements and the treated cores are inspected by environmental scanning electron microscope (ESEM).
Tangible evidence gives indications that secondary and tertiary reactions can be detected by this method.
The Near-Well State of Stress and Induced Rock Damage
Authors: Nikolaevskiy Victor N. , Economides Michael J. 
Published: December 2007

Abstract
High-stress concentration and substantial weakness of loosely consolidated to unconsolidated petroleum formations may cause considerable mechanical damage both during the drilling and the subsequent reservoir fluid production. Damage in our context is the appearance of a cloud or swarm of rock defects (microcracks) and the opening or, even, closing of preexisting pores or cracks. A physically and conceptually adequate idea is the mathematical modeling of the phenomena using an elastoplastic approach, which accounts for stress-sensitive matrix failure and solid/mass movements. Volume deformation because of dilatant interaction with shear is also accounted for.
Damage is characterised by the increase of a zone of plasticity augmented by internal-to-the zone phenomena. The emergence of plasticity does not necessarily mean total formation failure or loss of wellbore stability. Such a conclusion can be drawn only with the determination of displacement (i.e., strain) fields. Because problems such as the ones envisioned here are complex and their tracking depends on a number of parameters, computer modeling is necessary along with, at times tedious, laboratory determination of rock parameters. In the absence of measurements, published "typical" data for similar rocks can be used. The parameters include initial porosity and pore pressure, permeability, the elastic moduli, cohesion, and the friction and dilatancy coefficients, which change with changing stress. Problems described in this paper include the near-well damage effects because of high stress anisotropy and pore collapse. In this case local strains are determined. A second problem that is considered is the impact of well curvature and deviation from the vertical and the effects of crossing layers. Finally, sand production and some thoughts on water-shale interaction during drilling are addressed.
Constitutive Law for Permeability Evolution of Sandstones During Depletion
Authors: Boutéca M. J. , Sarda J-P. , Vincké O. 
Published: December 2007

Abstract
Permeability changes have been measured during triaxial tests performed on two sets of Vosgian sandstones. The obtained results led to the definition of a criterion in the p’-q plot (effective mean stress – deviatoric stress) for the evolution of permeability. Inside the domain defined by the criterion, the permeability change is nil or small whatever the loading path is. The results are generalized in a normalized p’*-q* plot. The normalized stresses p’*-q* were previously defined by Wong et al., and depend on the onset of grain crushing under hydrostatic loading. We suggest herein a simpler way to determine the normalizing stress. Furthermore, the experimental results are interpreted to propose an explicit law for the evolution of permeability as a function of the stress path.
Cavity-Like Completions in Weak Sands
Authors: Palmer Ian D. , McLennan John D. , Vaziri Hans H. 
Published: December 2007

Abstract
This study is about when, where, and how to implement an advanced completion technique, based on deliberate sand production, in order to induce "cavities" that increase productivity of a well (a "cavity" can be a void, or an enhanced perm zone of disaggregated sand). The concept spans the spectrum of well life, from a cavity as the initial completion, to managing sand flowback in mature wells. Folds-of-increase (FOI) in the range 3–20 have been found in field applications. This compares with FOI of 2–5 after hydraulic fracturing. In certain field cases, sand does stop coming into the well as the cavity stabilizes. A strong enough caprock (overburden material) is a key to the success of cavity completions in some unconsolidated formations in the field. Two kinds of laboratory tests have been conducted: (1) centrifuge tests in unconsolidated sands with low stresses, (2) large block tests in weakly consolidated sands, with more realistic stresses. In both cases, allowing sand to flow increased the productivity of the well by several fold, and the cavity geometries provided insights into what may happen in the field. The work has also included evaluations of subsidence and casing stability, due to sand production. Also, a model has been created to optimize a cavity completion by calculating the productivity increase (PI), stability of cavity, and sand disposal costs, all as a function of volume of sand removed. The results herein have implications for other business areas: eg, sand management; increasing injectivity for injection wells; and underbalanced drilling, perforating, surging applications.
Viscosification of Oilfield Brines: Guidelines for the Prevention of Unexpected Formation Damage
Authors: Javora P. H. , Ali S. A. , Bowen K. D. 
Published: December 2007

Abstract
Polymer viscosified oilfield brines have been accepted by the industry and routinely used to transport sand in gravel pack applications, to control fluid loss to the formation, and in other oilfield applications. However, recent observations of precipitate formation from heat aged viscosified brines indicated that the thermal stability of viscosified oilfield brines can vary dramatically. Variations were observed not only for the same polymer in different oilfield brines, but also for the same polymer from a different source in the same brine, and even for the same polymer in different concentrations of the same brine.
This paper details the systematic study conducted to identify and map the safe operating environments for selected oilfield polymers used to viscosify standard oilfield brines. Polymer viscosified brines were prepared by standard procedures, and statically heat aged at prescribed temperatures. The clarity of aged samples, including precipitation and separation tendencies, retained viscosities, and return permeability measurements were used to determine thermal stability. Systematic polymer-brine composition-temperature relationships were observed, and certain combinations were found to be a significant source of unexpected polymer precipitation and formation damage.
Results from this study provide the basic guidelines for the selection and field application of polymer viscosifiers for oilfield brines presented in this paper. Details concerning the viscosification process, its impact on TCT (True Crystallization Temperature), and the viscosification of zinc based brines are outlined. A two step viscosification process for brines containing low zinc concentrations is presented.
Factors Affecting the Performance of Enzyme Breakers for Removal of Xanthan-Based Filter Cakes
Authors: Luyster Mark R. , Monroe Terry D. , Ali Syed A. 
Published: December 2007

Abstract
The use of enzymes as an external breaker for removal of xanthan based filter cakes has exhibited cost savings and effective clean up in several open-hole horizontal Gulf Coast wells.
Enzymes are specialized proteins produced by cells of living organisms. They act as catalysts to promote specific reactions. Polymer-specific enzymes hydrolyze xanthan resulting in non-damaging fragments. As a catalyst, the structure of an enzyme is unchanged by the reaction it promotes; therefore, the enzyme has the ability to initiate another reaction. The reactivity of the enzyme is essentially infinite with the exception of damage to the enzyme by chemical, thermal, or mechanical means, i.e. denatured. Xanthan-specific enzymes degrade or cleave either the α – 1,2 or β – 1,4 glycosidic linkages of the substituent and the β – 1,4 linkages of the backbone.
Recent laboratory investigations revealed several factors, which can control the effectiveness of an enzyme. These factors include xanthan quality, iron, base brine and hydrocarbons. These factors can function as barriers and prevent the enzyme from cleaving specific linkages of the xanthan structure.
This study presents guidelines for formulating an enzyme compatible xanthan based drill-in fluid for open-hole horizontal completions. These guidelines were recently applied to two recent open-hole horizontal completions in the Gulf of Mexico that yielded optimum results.
Investigation of a Long-Term Cement Deterioration Under a High-Temperature, Sour Gas Downhole Environment
Authors: Krilov Z. , Loncaric B. , Miksa Z. 
Published: December 2007

Abstract
The indications of cement deterioration at one of the greatest gas condensate fields in Pannonian basin (Croatia) was the motivation for research study carried out in order to investigate the possible involved mechanism of impairment. After almost 15 years of hydrocarbon production form naturally fractured carbonates, some wells begun to suffer of plugging across the perforated zone with unidentified debris, which was accompanied with water cut increase.
This paper describes the laboratory evaluation of the actual environmental downhole impact (high reservoir temperature, BHST &gt; 180°C, sour gas: 22% CO2 and 150 ppm H2S) to the cement, as well as debris identification.
The work indicated that oilwell cement under hostile downhole conditions after long-term exposure could be deteriorated loosing of compressive strength and its integrity. The dominant mechanism of cement deterioration is caused by CO2 corrosion process in the form of carbonic acid leaching.
The CBL log data verified the cement disintegration behind 7-in. casing after 15 years of well production period.
Gravel-Pack Evaluation Using a Memory Gamma-Gamma Density Tool
Authors: Fisher Kevin , Kessler Calvin , Rambow Fritz , Tucker Charles , Madigan William 
Published: December 2007

Abstract
Completions in poorly consolidated formations often require gravel packing or frac packing to eliminate the inflow of formation fines. The effectiveness of gravel placement in the screen-casing annulus or openhole annulus or behind casing (such as when prepacking perforation tunnels) may be qualitatively evaluated with treatment-pressure data. Voids in the gravel-packed screen-casing or openhole annulus are evaluated with data from density, neutron, gamma-tracer, or pulsed-neutron logs. When radioactive materials are used for evaluating proppant placement in the formation, however, gamma measurements are affected by the background signal produced by these materials. This signal makes conventional density and pulsed-neutron silicon-activation techniques ineffective. A high-resolution, memory gamma-gamma density logging tool has been developed that measures changes in the bulk density of the annular region of a gravel-pack completion. The source-to-detector spacing and source strength have been optimized to minimize the effects of variations in borehole fluid and of changes in casing-screen size and geometry. Most importantly, this measurement will not be affected by the presence of radioactive tracers used to evaluate proppant placement.
The new memory-based logging system allows the tool to be placed in the washpipe prior to the completion and for the logging pass to be recorded as the washpipe is retrieved from the well. Significant savings in rig costs and in time to production are gained through use of the washpipe-conveyed memory logging technique. This paper reviews the measurement principles of the tool and presents data from tests in calibration pits.
High-Pressure Water Jetting: An Effective Method to Remove Drilling Damage
Authors: Aslam Javed , Alsalat Talib 
Published: December 2007

Abstract
High-Pressure Water Jetting (HPWJ) has been used for decades for various industrial applications. The major uses of this technology have been to clean the various surfaces, as well as demolishing or cutting different materials. The process has been used in oil and gas wells to clean tubulars from deposits of asphaltene, paraffin, and common inorganic scales e.g. calcium and magnesium compounds. These scales are usually very hard and difficult to remove by chemical methods. By utilizing abrasive materials such as sand and beads, the process has been used to cut steel pipes or make perforations.
In recent times, drilling technology has revolutionized the shape of the wells. Most of the new wells are drilled in a horizontal direction across the reservoir thus exposing a relatively large reservoir area for drainage or injection. Majority of the new wells is completed ‘bare-foot’ i.e. without cementing a casing or a liner. As the horizontal wells have usually long open holes, the use of conventional acidization to remove drilling damage requires large volumes of acid. As a result acidization is very expensive. The acid utilization is very inefficient as most of the acid leaks into ‘thief’ zones.
In an effort to reduce the cost of damage removal in long horizontal open holes, Qatar General Petroleum Corporation (QGPC) has utilized HPWJ technology to remove the drilling damage. The treatment has been applied to more than 10 horizontal wells to date and it has been found to be very successful. The process is simple to use because the only consumable is water. Service costs are minimal as the pumping equipment of the rig is utilized for the treatment. This paper covers theoretical aspects of the HPWJ technology, case histories and well performance data.
Through-Tubing Gravel Packs Performed by Electric Wireline–Case History
Authors: Rice R. T. , Navaira G. , Champeaux G. 
Published: December 2007

Abstract
A high success rate has been seen on twelve through-tubing gravel packs performed with a unique electric wireline technique. This paper is a case history and analysis of these jobs.
The method is primarily designed for zones with marginal reserves, which cannot justify costs of more conventional TTGP techniques. The case study shows that this method is profitable for these marginal zones and also higher reserve zones with certain criteria.
The paper discusses the selection criteria, pros & cons of this method, and lessons learned.
Several of the wells have bottom-hole pressure survey data, the results and implications being presented in the paper.
Perforating Requirements for Sand Prevention
Authors: Venkitaraman A. , Behrmann L. A. , Noordermeer A. H. 
Published: December 2007

Abstract
Sand prevention implies an acceptable risk of sand production over the producing life of the well with no sand control mechanisms implemented. This paper reviews available methods to optimize the choice of perforation parameters (phasing, shot density and charge type) for sand prevention. Prior work has shown that sand production is preceded by failure of the perforation tunnels. In order to have successful sand prevention it is necessary to have stable perforation tunnels through rate (drawdown) changes, depletion, and water-cut. Available methods to determine the ability of perforation tunnels to produce sand free can be classified into theoretical models, experimental methods and historical techniques.
Deep penetrating charges are recommended as they produce smaller diameter perforation tunnels that are more stable than larger diameter tunnels produced by big hole charges. Optimum phasing technique relies on the maximization of distance between adjacent perforations in 3-dimensional space for a given wellbore radius and shot density. This is advantageous in avoiding inter-linking of failed zones around adjacent perforations. Data from the Magnus field in the North Sea supports the use of these two techniques in minimizing sand production. Where there are significant stress contrasts in the formation and the directions are known, oriented perforating can be used to increase the stability of perforation tunnels (especially when increasing drawdown and when depleting the reservoir).
It is shown how these three main techniques can be used to perforate for sand prevention. In addition, the paper also provides guidelines on how to avoid sand production at the time of perforation, selective perforating where there is a contrast in formation strength with depth and the use of experimental techniques to determine perforation stability due to rate (drawdown) changes, depletion and water-cut.