bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Decline Curve Analysis Using Normalized-Time and Type Curves for Vertically Fractured Wells
Authors: Fraim M. L. , Lee W. J. , Gatens J. M.
Published: December 2007

The purpose of this paper is to present a new constant pressure type curve to analyze long-term production from a well with a finite-conductivity vertical fracture. In addition, the paper presents a method to account for real gas properties and non-Darcy flow existing in the fracture. Solutions are presented for production with both'constant bottomhole pressure and constant surface pressure.

At the present, for rapid long-term production predictions for stimulated wells in bounded reservoirs, the Fetkovich1 constant pressure type curve for radial flow can be used. This type curve models production from high conductivity fractures with a maximum fracture half-length one tenth the outer radius of the drainage area. For early transient production, the Guppy2 constant pressure type curves for hydraulically-fractured wells are available. Guppy presents type curves for selected conductivities and non-Darcy flow coefficients. The type curves terminate at the end of bilinear flow, which is about two log cycles before pseudo-radial flow begins.

Constant pressure type curves are particularly useful in modeling long-term production from stimulated low-permeability formations with long fractures, and there is a need for modeling both transient and non-transient flow. To meet this objective, this paper presents overlays for the Fetkovich type curve for dimensionless fracture conductivities, Cr, from 0.2 to 100, (Cr=kfbfπkxf) and drainage area to fracture half-length ratio, xe/xf, from 1 to 64. We use a normalized time function to correct for real gas properties and for non-Darcy flow in the fracture, tubing, and surface facilities.
Permeability Variation in a Sandstone Barrier Island-Tidal Channel-Tidal Delta Complex, Ferron Sandstone (Lower Cretaceous), Central Utah
Authors: Stalkup F. I. , Ebanks W. J.
Published: December 2007

This paper describes a study to determine how permeability varies spatially in outcrops of an ancient barrier island-tidal channel-tidal delta complex. This type of information is useful for developing models of between-well reservoir permeability heterogeneity for application where data are not available.

Fifteen outcrop exposures representing different vertical sections of the complex were examined to determine the lithofacies present and their distribution. Horizontal cores approximately six in. long and one in. in diameter were taken at selected locations for permeability measurements.

These observations and measurements give the following picture of permeability structure in the sediments of this particular complex. Permeability heterogeneity occurs on several size scales. On the largest scale, crossbedded, burrowed, rippled, and shaly lithofacies are distinguished for characterizing gross permeability layering. These permeability units are continuous over distances of at least 500 to 1000 ft in the seaward direction and probably are continuous over much greater distances in the along-shore direction. Some lithofacies did not define independent permeability units, however, and had to be combined with vertically adjacent facies to form a unit. On an intermediate scale, permeability sublayers on the order of 2 to 4 ft thick occur within some of the units. The lateral extent of these sublayers was not determined. On a small scale within the sublayers, permeability variation appears to be random for samples that are separated by at least 6 in., the minimum sample separation investigated. Estimates are given in the paper for the magnitude of permeability contrast between permeability units, the lateral variation of mean permeability within a unit, and the permeability contrast between sublayers within a unit.

Permeability of the rocks in outcrops was compared to that of similar rocks in the same stratigraphic unit in a nearby well. Permeability contrasts among lithofacies are greater in the subsurface than in the outcrops because of surface weathering, but the vertical arrangement of statistically different permeabilities is similar in the two situations.
Multiphase, Multicomponent Compressibility in Petroleum Reservoir Engineering
Authors: Macias L. C. , Ramey H. J.
Published: December 2007

Coefficients of compressibilities below the bubble point were computed with a thermodynamic model for single and multicomponent systems. Results showed coefficients of compressibility below the bubble point larger than the gas coefficient of compressibility at the same conditions. Two-phase compressibilities computed in the conventional way are underestimated and may lead to errors in reserve estimation and well test analysis.
A New Method of Gas-Bearing Zone Identification by Well Logging
Authors: Tan T.
Published: December 2007

Conventional methods for gas bearing zone identification are based on the comparison of the neutron log porosity to the density log porosity. In low porosity, varying matrix formations the gas detection is often difficult.

The method proposed in this paper is a new method which identifies gas bearing zones by using a Difference Ratio of Equivalent Elastic Modulus of formation rock (EDR). The ratio is calculated by the combination of sonic log, density log and neutron log. The formula used to calculate the ratio is as follows: EDR= (Ecw−Ec)/Ec

in which, Ec is the equivalent elastic modulus of the formation of interest in dyne/cm2, Ecw is the equivalent elastic modulus of the same formation of interest 100% water saturated in dyne/cm2.

When Ecw is greater than Ec, EDR is greater than zero and this indicates gas bearing zone. On the contrary, when Ecw is smaller than Ec, EDR is smaller than zero and this indicates a non-gas bearing zone.

The method has been used to interpret some sand and carbonate gas reservoirs of China. The results presented in this paper show that higher resolving power of gas bearing zones, better interpretation accuracy, and "quick look" estimates can be readily achieved.
Stability of Waterflood Diverting Agents at Elevated Temperatures in Reservoir Brines
Authors: Nagra S. S. , Batycky J. P. , Nieman R. E. , Bodeux J. B.
Published: December 2007

Water channelling is a significant problem in oil producing reservoirs. One way to improve sweep is "by diverting water to unswept zones through the placement of polymeric gels as diverting agents. The key to successful application of these materials is the amount of time over which the gels will he effective at reservoir conditions. Gel stabilities of a range of polymer compounds were tested in reservoir brines with salinities up to 10% TDS and at temperatures up to 90°C. One characterization of gel stability was the amount of time (half-life) required for a gel to shrink to half its initial volume. Results at 90°C with Polyacrylamide, cellulosic and xanthan gels showed short half-lives ranging from less than a day (complete syneresis) up to 45 days depending on concentration and polymer type. Intermediate stabilities were observed with scleroglucan while the most stable gels with half-lives of more than a year were observed at 90°C with lignosulphonate and phenoformaldehyde materials. Based on this screening procedure, phenoformaldehyde gels were tested for permeability reduction in both homogeneous and fractured cores after which the products were field tested. Preliminary results from a number of field tests provide optimism to continue a cautious program to develop placement and evaluation techniques.
Restructuring – Survival or Suicide
Authors: Hassell Richard Lee
Published: December 2007

Looking back on the last four plus years, our industry has had the unique opportunity to navigate uncharted waters in our attempts to cope with the slide in oil/gas prices. Most of our forecasts, planning sessions, meetings, and seminars during this time have continually underestimated the extent, duration and depth of the problems we face today. Throughout these years, countless individuals have sold their plans or forecasts by predicting – "When things turnaround …." For those of us believing in a turnaround I suggest that this is like waiting for the flight which has been cancelled.

Some firms have done reasonably well during this time – namely the major international energy companies, a few domestic producers, and a very small percentage of the oilfield service, supply and manufacturing industry. The vast bulk of our industry, however, is still "twisting in the wind" as they attempt to cope with restructuring. Continual application of short-term remedies where more extensive measures are required still is the norm. Many are destined to commit slow suicide, a few will survive.

Although the term "restructuring" may be relatively new, our industry has been going through it for many years, even prior to 1982. Restructuring may be defined as:
General Formulation of Drillstring Under Large Deformation and Its Use in BHA Analysis
Authors: Ho H.-S.
Published: December 2007

The paper presents the basic formulations adopted in a 3-D BHA program called DIDRILSM*, for drillstring deformation under general static downhole loadings. These formulations account for large deformation effects, and have been simplified for fast solution using the finite difference method, while retaining second order terms. An explicit formula for the bit side force is presented. In addition to previously demonstrated effects of WOB, TOB, and borehole curvatures on the bit side force, this paper demonstrates some non-linear effects on the bit side force, which increase with large deformations, mainly due to increased borehole curvatures. For 2-D borehole with less than 5°/100′ curvature, the nonlinear effects on the bit side forces are in general small. The nonlinear effects are seen to be insensitive to WOB, TOB, and hole clearance for the examples considered. Effects due to these latter variables on the local force/moment distributions may be more pronounced.
Combined Effects of Shut-in and Production: Solution with a New Inner Boundary Condition
Authors: Correa A. C. , Ramey H. J.
Published: December 2007

A new approach was used to solve the the problem of pressure buildup following constant bottom hole pressure production. Previous methods of solution involve finite difference solution or numerical evaluation of the superposition integral. An analytical solution correct for both the flowing and shut-in periods was obtained by solving the diffusivity equation with a single inner boundary condition which included the mixed conditions for flow and buildup. Both a skin effect and wellbore storage were included even though the production period was at constant wellbore pressure. Solution was obtained by Laplace transformation.

The procedure presented in this paper may be used to solve other interesting problems. One example presented is the joint solution of constant rate production and shut-in with wellbore storage and skin effect. The procedure used does not involve superposition.
A Comparison of the Use of Pseudotime and Normalized Time for Gas Well Buildup Analysis in Various Geometries
Authors: Spivey J. P. , Lee W. J.
Published: December 2007

The real gas flow equation is effectively linearized for drawdown when expressed in terms of pseudopressure and time. Two time functions have been proposed to linearize the flow equation for buildup: pseudotime and normalized time.

This paper compares the use of pseudotime and normalized time for a variety of different analysis techniques. The study focuses on buildup following constant rate drawdown for systems in which the reservoir is still infinite acting. For radial flow, analysis methods considered include log-log type curve matching and Horner analysis. Analysis methods for wells with infinite conductivity vertical fractures include linear flow analysis, log-log type curve matching, and Horner analysis.

Except for wellbore storage, no major difference in accuracy is found between pseudotime and normalized time.

Also compared are two different methods for treating producing time effects when using pseudo-time or normalized time. A new method of calculating the equivalent drawdown time function is presented which is independent of initial pressure.
Underground Storage in Cerville-Velaine, France: A Case History in Conversion and Inert Gas Injection as Cushion Substitute
Authors: Laille J. P. , Coulomb C. , Tek M. R.
Published: December 2007

Whether on an aquifer or depleted field storage, the cushion gas represents a substantial, if not major, component of Investment required to develop the storage project. The economic advantage of an inert cushion which can be produced at a lower cost than pipeline quality storage gas has been recognized for sometime.

This paper presents a complete case study of a gas conversion and inert gas injection in Cerville-Velaine, an aquifer storage operated by Gaz de France. First, for 1986-87 a programmed change from low BTU to high BTU gas will be described. Then, in second stage, part of the cushion will be replaced by an inert substitute.

The engineering plans for the two equations involved numerical simulation by several different models. The degree of complexity of the simulators ranged from those corresponding to simplified, equal mobility displacements to 3-D with compressibility, miscibllity and diffusional transport through porous environment. The conditions related to mixing were characterized by using data from field tests involving hydrogen as a tracer.
Mechanism-Based Simulation of Oil Recovery Processes
Authors: Heiba A. A. , Jerauld G. R. , Davis H. T. , Scriven L. E.
Published: December 2007

Accurately modeling recovery processes mathematically and simulating their performance numerically requires (1) a consistent theory of capillary pressures, relative permeabilities, and dispersivities that characterize the flow and distribution of fluid phases, and (2) a flexible discretization of the governing equations that resolves the moving steep fronts that often develop. Recent advances in both are combined and applied to two-phase and three-phase displacements as in cores and reservoir streamtubes. Cases exemplifying one-dimensional displacement in various water-drives and gas-drives are examined. Such simulations can be used to design and interpret laboratory measurement of flow properties and tests of process performance.
Capillary Pressure Discontinuities and End Effects in Homogeneous Composite Cores: Effect of Flow Rate and Wettability
Authors: Hinkley R. E. , Davis L. A.
Published: December 2007

The optimum construction methodology of composite cores for multiphase flow tests is an important practical petrophysical concern. The critical feature of construction is the minimization of saturation disturbances which occur due to capillary pressure discontinuities at individual core segment interfaces. The effect of matrix discontinuities on two-phase flow in homogeneous composite cores was studied as a function of flow rate and wettability. Five composite cores, representing a range of wettabilities, were prepared. The composite cores were constructed by splicing multiple core segments with bridging materials of differing wettabilities. Saturation profile data were measured with a microwave saturation scanner during imbibition and drainage floods.

The interface between core segments had a strong effect on the saturation distributions when capillary contact was not maintained between contiguous segments. Under drainage conditions at low flow rates, each core segment behaved as though it were an independent core experiencing a strong exit end effect. In steady-state fractional flow experiments this occurred only at fractional flows close to unity. The most effective bridging materials for water-wet Berea were thin paper sheets. No bridging material was found to be completely adequate in an oil-wet environment. In the absence of good capillary contact, increasing the flow rate is a practical remedy for the saturation disturbances.
3-D Seismic Lithologic Modeling To Delineate Rapidly Changing Reservoir Facies: Case History From Alberta, Canada
Authors: Gelfand V. A. , Taylor G. , Tessman J. , Larner K. L.
Published: December 2007

Although river-channel reservoirs are attractive because of their potential high porosity and permeability, their development is difficult because of rapid variations in the distribution of sands and shales. The Taber-Turin area of Alberta, Canada is a known oil province characterized by such reservoirs. To delineate potential reservoirs in detail, a 4-km2 3-D seismic survey was conducted, resulting in a square grid with traces 20-m apart. The Seismic Lithologic Modeling (SLIM™) process, an automated procedure that refines initial geologic models, was then applied to provide a thin-layer interpretation of the processed data. Although the initial model for the seismic lithological modeling was based on information from only one borehole (primarily for calibration purposes), the derived velocity model revealed, in detail, the thin Glauconitic reservoirs (0-30 m thick) that are the targets of the delineation effort. All six boreholes previously drilled in the area, four of them producers and two dry, are consistent with the SLIM interpretation. With the help of the SLIM results, five additional boreholes were proposed. All of them have been completed, and all are oil producers.
Laboratory Testing of High-Pressure, High-Speed PDC Bits
Authors: Maurer W. C. , McDonald W. J. , Cohen J. H. , Neudecker J. W. , Carroll D. W.
Published: December 2007

A high-speed drilling system has been developed which drills medium strength rocks at rates up to 1000 ft/hr (328 m/hr). This system uses special motors to operate high-pressure PDC bits at pressures up to 10,000 psi (69 MPa) and at speeds of 800 to 1000 RPM. High drilling rates were achieved due to the high rotary speeds and the use of PDC cutters to remove the rock ledges left on the hole bottom by the high-pressure jets.
Roller-Bit Penetration Rate Response as a Function of Rock Properties and Well Depth
Authors: Walker B. H. , Black A. D. , Klauber W. P. , Little T. , Khodaverdian M.
Published: December 2007

A rate of penetration (ROP) prediction equation for an insert roller cone bit is determined from laboratory drilling tests as. a function of bit weight, well depth and laboratory measured rock properties. A complete description of each of the seven rock types used in the study is presented. A comparison of ROP at different flow rates for each rock shows minimal hydraulic cleaning problems at the base hydraulic energy levels chosen. The predictive equation will be valuable in predicting drilling rate and understanding how the rock properties affect it.
Reservoir Simulation Based on the Finite Analytic Method
Authors: Iqbal G. M. , Civan F.
Published: December 2007

Traditionally reservoir simulation has been accomplished by solution of reservoir flow models using variations of the methods of finite differences and less frequently by finite elements. The accuracy of these methods depends heavily on the size of grid blocks and time steps employed for the numerical solution. Consequently, computational time and memory requirements may be overwhelming in many cases.

In the present study, a recently proposed method called the finite analytic method is shown to alleviate the difficulties associated with the conventional methods. The finite analytic method is operationally and principally different than the conventional finite difference and finite element methods in that a general analytical solution of the simulation model is used over mesh elements to obtain a numerical scheme. Therefore, for comparable accuracy, finite analytic method can lead to higher order approximations than those achieved by the finite difference and finite element techniques. Finite analytic schemes are derived from the reservoir flow models and therefore they are naturally problem dependent. This is the reason for the efficiency of the finite analytic method. By this method problems such as numerical diffusion, numerical instability, slow convergence, as well as requirements of large number of time steps and grid blocks are significantly reduced.

In this study, the methodology of formulating and calculating with this method is illustrated by means of a typical two-phase immiscible flow problem described by the Buckley-Leverett equation. The results are compared with the analytic solution of Buckley-Leverett problem and solutions obtained by finite difference and finite element methods. The present study demonstrates that the finite analytic method is capable of producing accurate flow behavior in porous media even when relatively large time steps and grid blocks are used.
Prediction of Static Elastic/Mechanical Properties of Consolidated and Unconsolidated Sands from Acoustic Measurements: Correlations
Authors: Montmayeur H. , Graves R. M.
Published: December 2007

Basic measurements required for a proper static-dynamic rock properties determination were presented in a previous paper by the same authors1. Biot's theory and Walsh's microcrack analysis are combined to study static-dynamic property relations. In the absence of microcracks, Biot's relations are used to compute static "uncracked" rock properties using density, porosity, and the travel times of longitudinal and shear wave velocities. When microcracks are present, relations derived from Walsh's microcrack analysis along with Biot's relations are used to obtain the static properties from dynamic measurements.
Turbine-PDC Applications in the Gulf of Suez
Authors: Howard D. C. , Day J. C. , Mansour S.
Published: December 2007

GUPCO (Gulf of Suez Petroleum Company) is the largest operator in Egypt. The last 2-1/2 years activity level has been high, with an average of 10-12 rigs operating, and annual footage drilled in excess of 600,000' [183,000 m].

Straight hole turbodrills and polycrystalline diamond compact (PDC) bits have improved drilling efficiency in the Gulf of Suez (G.O.S.) since their initial use in April 1983. Applications in mature fields and areas where conventional drilling techniques had been optimized have benefited from the infusion of this new technology. Although PDC turbine applications in both the 12-1/4" [311.15 mm] and 8-1/2" [215.9 mm] hole sizes have been successfully undertaken, the majority of our turbodrilling experience is in the 12-1/4" [311.15 mm] section. Accordingly the primary focus of this paper will be 12-1/4" [311.15 mm] bit runs.

We have identified successful applications in various lithologies using both water and oil base drilling fluids. This paper documents some of GUPCO'S turbine-PDC successes and failures and outlines the analytical process which we are using to optimize our application selection.
Fractured Clastic Reservoirs in South Oman: Possible Models of Origin and Implications
Authors: Mäkel G. H.
Published: December 2007

Fracturing of Paleozoic clastic reservoirs in South Oman is most likely related to halokinetic structuration during the deposition of Al Khlata sediments. Locally, in the Qata Field, fracturing may be attributed to syn-Al Khlata collapse due to melting of embedded ice formed during the Late Paleozoic Gondwana glaciation. Lithological differences are the reason that the fractures in the Al Khlata are primarily closed but those in the Haima sandstones represent favourable conduits for fluid flow. Erosion of (much of) the fractured sediments, especially from the crest of Haima-cored structures, may be the reason that fractures have not been found in all the fields. Alternatively, rather than pervasive fracturing, faulting or the reactivation of faults may have been the response to halokinetic structuration.
Modernizing Offshore Control Systems
Authors: Dodin M. J.
Published: December 2007

Modern Control Systems can provide sophisticated control for unmanned Wellhead platforms and Offshore Oil and Gas production plants. This paper describes design concepts formulated to modernise offshore control in ADMA-OPCO's fields in the U.A.E. These concepts cover the inter-related topics of Wellhead control and safety shutdown, supervisiory control and data acquisition, fire and gas detection and protection and solar system appliations.
Experience with Seawater Injection
Authors: Al-Rubaie J. S. , Muhsin M. A. , Shaker H. A. , Washash I.
Published: December 2007

ADMA-OPCO has been injecting seawater for more than 10 years into two separate fields offshore Abu Dhabi. Some wells have shown deterioration in injectivity. The causes of deterioration and remedial action to regain injectivity are discussed. Steps have been taken not only to remove the plugging material from the system but to prevent corrosion which constitute the main source of the debris.
Review of Dual Completion Practice for Upper Zakum Field
Authors: Othman M. E.
Published: December 2007

Oil in Zakum field is produced since 1983 from six different zones. Water is injected into these zones since 1984 for pressure maintenance. In this field, a total of 233 wells (producers and injectors) have been permanently completed with dual strings to give a segregated production or injection capabilities from two separate zones in each well. These two zones are isolated fran each other by natural barier and cement behind the casing and by packers in the bore hole. Developed offshore completion technology has been used to take the maximum advantage of the dual completion hook-up.

The major advantage of this feature of the completion is in its effectiveness of maintaining production or injection and montoring performance of each zone separately in the field.

Operationally, this type of completion is performing satisfactorly in all producer wells whereas string annulus ccmmunication is experienced in large number of injector wells. Solution of this problem is defined and being implemented for final evaluation.

FORWARD

The upper Thamama structure in Offshore Abu-Ehabi is of a lower cretaceous age and consists of an alternating series of porous and dense limestones. In the Zakum field, this structure has been divided, as indicated in Fig.l, into six porous zones, named Thamama IA, II, IIIA, IIIB, IIIC and IIID-H. These zones are separated by six dense intervals, well developed all over the field, acting as natural barriers which prevent the cross flow between the different zones.
Anomalous Oil Saturation and Fluids Contacts in Mauddud Reservoir, Bahrain Field
Authors: Samahiji J. A. , Kolluri S. R.
Published: December 2007

Previous assessments of Mauddud reservoir of Bahrain Field have considered the reservoir to be a homogeneous unit and that long term gas injection has helped increase recovery efficiency. The present study revealed that the anomalous fluid saturations are the combined result of (1) heterogeneity and layered nature of the reservoir, (2) differences in drive efficiencies by natural water drive and induced gas cap. It is concluded that the recovery efficiency can be improved, firstly by injection of gas in the lower layers of the reservoir and secondly by systematic employment of low volume producers as against the present practice of high volume production.
Khuff Gas Production Experience
Authors: Kasnick M. A.
Published: December 2007

The non-associated gas from the Khuff reservoirs has been developed to provide supplemental fuel gas and petrochemical feedstock. The production systems are centered on the ’Uthmaniyah and Shedgum areas of the Ghawar field because of the close proximity to sour gas handling plants.

Untreated sour gas is produced through the gathering systems directly to gas plants. The high rate, high pressure sour gas production is closely monitored so the system operates within acceptable guidelines. Scale formation in tubulars, hydraulic limits of surface and subsurface pipes, and potential corrosion/erosion problems in surface facilities are typical concerns in this sour gas producing system.
Pipeline Systems for Tail Gases Distribution and Optimization of Long Distance Pipelines
Authors: Giesen H. P.
Published: December 2007

Unlike general transmission pipelines the emphasis lies on the distribution of the captured lean gas in a restricted area rather than transmission over a long distance.

The production of oil is often accompanied by a vast amount of associated gas which represents a substantial part of the energy content of the field and which is often simply flared due to the lack of a pipeline system to distribute it to customers in the vincinity of the field. Using the example of an on-shore field in the Emirate of Sharjah, UAE, this paper demonstrates how at least part of the associated gas which originally was flared has been collected, compressed and distributed to power stations and industrial consumers to substitute distillate fuel. It also describes how the project was implemented from the initial feasibility study to initial commercial operation.

The second part of the paper deals with long distance pipelines such as those which carry natural gas from western Siberia to Europe. One of the main aims in the optimization of these lines is the improvement of transportation efficiency. This means the reduction of fuel gas requirements and increasing the overall efficiency of the compressor stations.

The development in this field has led to large diameter pipelines and high operating pressures which in turn make it compulsory to use high grade steels like X 70 or even X 80 for the pipes. The improvement in machinery and related station equipment has reduced fuel gas losses from the former figure 13 % to approximately 10 %. Further reductions to below 10 % are probable if all the-modern possibilities of waste heat recovery and computer aided load management are applied.
Development of Field Design Rules for Viscous Fingering in Acid Fracturing Treatments: A Large-Scale Model Study
Authors: Davies D. R. , Bosma M. G. R. , de Vries W.
Published: December 2007

The development of effective stimulation procedures for homogeneous, low permeability, chalky formations is of concern to many operators. One technique – the employment of viscous fingering during acid fracturing treatments – has proved to be suitable for use in the development of limited oil columns sandwiched between underlying water and overlying gas.

The literature on the study of unstable displacement processes contains extensive references to the displacement on one Newtonian fluid by a second Newtonian fluid. However, the unstable displacement of a non-Newtonian fluid by a Newtonian fluid – as occurs during the viscous fingering, acid fracturing process – has not been previously addressed in the literature.

Experiments were performed in a large-scale, parallel plate model sized to simulate the conditions in the field. The experiments showed that, after a short transition period, a pseudo-steady state was reached in which the 'finger' grows in length at a constant height.

Viscosity ratio, injection rate and fracture width were identified as the variables that controlled the fingering process.

The experiments were analysed quantitatively and guidelines were developed for the design of viscous fingering, acid fracturing treatments. Results from field experience of the stimulation of a Middle East, low permeability chalky reservoir using these optimum design rules are presented.
Toward Unmanned Oil and Gas Production Offshore
Authors: Johnston I. W. , Young H. L. , Huntington J. R.
Published: December 2007

With the continuing increase in marginal field developments particularly in the North Sea, the pressure continues to minimise costs. There has been a continuous trend towards unmanned facilities to capitalise on reduced operating and first costs.

This article reviews the current remote processing facilities utilised offshore with particular emphasis on subsea hardware, process and utility equipment and control and communication systems.

The key element to the further use of unmanned systems is the reliability of process equipment. This article analyses the reliability of process and utility systems utilised in offshore oil and gas processing and projects future unmanned facilities scenarios.
A New Approach to Drill Bit Selection
Authors: Rabia H. , Farrelly M. , Barr M. V.
Published: December 2007

This paper describes a novel approach to bit selection based on the use of Specific Energy. Since the 1960s, Specific Energy has been used in many rock-working studies as a measure of rock-cutting efficiency. Two previously derived equations are examined using laboratory data and a modified equation proposed. When applied to field data this equation has been shown to be a potential aid in bit selection.
Well Spacing Performance, Relative Permeabilities and Acidization Effects in a Limestone Reservoir
Authors: Folmar L.W. , Williams J.M. , Stephenson E.K.
Published: December 2007

The degree of drainage interconnection in a 40,000-acre, heterogeneous limestone reservoir of depletion type was analyzed through the use of unique reservoir pressure data. These data were available from five separate test-well locations representing the maximum drainage radius required of producing wells on 80-acre spacing. The knowledge of the reservoir pressure at the extreme radius of drainage after substantial production from adjacent producing wells provided a unique method of calculating the distribution of reservoir pressure from the extreme radius into the producing well rather than the usual reverse procedure. This unusual type of data in effect provided a field laboratory for the study of relative permeability effects upon the three phases present during depletion and the related effect upon the producing pressure gradients of surrounding wells. Indications as to the magnitude of effect from acidizing the producing wells were also observed.

The analyses showed that drainage performance of the reservoir studied was predictable by adjustment of air-derived permeability for formation water saturation and by the use of an average expected effect from acidization of producing wells. Excellent correlation between relative permeability and formation water saturation was obtained for the five test-well areas studied. The analyses further showed that efficient and effective drainage of the reservoir on an 80-acre spacing pattern was being accomplished and would continue to be accomplished under primary operations. Actual field performance is the only gauge of the accuracy of performance predictions.
A Model for Measuring the Effectiveness of MWD Systems
Authors: Ryan D. M.
Published: December 2007

A conceptual framework can be developed for measuring effectiveness of MWD services in terms of availability, reliability and capability. Availability is defined as the condition of being ready to provide services when required. Reliability is defined as providing service during the specified interval of a bit run. Capability is defined as performance within tolerance. The effectiveness of MWD systems can be mathematically modeled using these concepts.
Density Modeling for Pure and Mixed-Salt Brines as a Function of Composition, Temperature, and Pressure
Authors: Kemp N. P. , Thomas D. C.
Published: December 2007

Electrolyte solutions containing high concentrations of salts such as sodium chloride, potassium chloride, calcium chloride, calcium bromide, and zinc bromide have several important applications in the oil field· The so-called "heavy brines" are used as solids-free completion fluids* Brines are also a major constituent of many drilling fluid systems including both water and oil-based muds. This paper describes the density behavior of brine solutions containing single salts and salt mixtures under varying conditions of temperature and pressure. Examples are given for using the derived density model to calculate both downhole differential pressures for brine completion fluids and the solids content in brine muds.
Transport of Cuttings in Directional Wells
Authors: Martin M. , Georges C. , Bisson P. , Konirsch O.
Published: December 2007

The aim of this research is to define easily applicable quantitative relationships for optimizing flow rates and drilling-fluid rheology depending on the inclination of the well. The research project involves various aspects: (1) laboratory experiments, (2) experiments in wells during drilling, (3) building a numerical model based on experimental data obtained in both the laboratory and wells.

Laboratory experiments performed in tubes and annular-space models have analyzed the influence of various parameters such as inclination, rotation of the drill string and fluid rheology, including thixotropy. The results of these experiments have led to equations describing the minimum fluid velocity required for evacuating cuttings versus their density, the density of the fluid and its rheological properties. In the numerical model, with a view to applying these equations to the well, they have been adjusted with the help of results obtained by checking the arrival of cuttings at the drill site during the drilling out of hardened cement in the casing above the casing shoe after cementing jobs.

Among the conslusions reached, the following points can be noted:

The influence of inclination becomes apparent as soon as the well becomes slightly deviated (10°). Evacuation of cuttings is more difficult in slanting zones, depending on the case, with an angle between 30 and 60°. High viscosity of the drilling fluid is favorable for the cleaning of the well in the nearly vertical part but may reduce the transfer capacity in the slanting parts. High thixotropy of the drilling fluid is very unfavorable in the slanting parts, especially if the rotation speed of the drill string is low. The increase in the density of the drilling fluid facilitates transport.
Deep Offshore Drilling Case History of North Padre Island 960-L #1
Authors: Roth E. G. , Payne M. L. , Leary M. J.
Published: December 2007

This paper summarizes the planning and drilling of the North Padre Island (NPI) 960-L No. 1 well. This well was drilled to 24,938-ft. RKB offshore South Texas. The well experienced temperatures in excess of 420°F and pressures above 23,000 psi at total depth. In addition, several other aspects of the well were unique to offshore drilling operations including:

Development of a 2,000 kips static hook load offshore rig. Use of newly-developed 30 in, 3,000 psi ram type BOP. Drilling of deep large diameter holes (24-in. to 1, ,897-ft. RKB, 16-1/2-in. to 15,863-ft. RKB). Designing, testing, running, and cementing of heavy weight casing strings up to 2,110 kips air weight.
A Cost-Effective Rig Move
Authors: Buchanan R.
Published: December 2007

USING A COST EFFECTIVE MOVE you can add up all of the equipment cost for each task and all of the labor cost for each task and it will be the same as the invoice and labor cost for the rig move. If these items are out of balance you have a reason to ask WHY?
A Systems Approach To Implementation Of A State Of The Art Solids Control Package For The Southern North Sea.
Authors: Kew S. A. , Robichaux M. P. , Mclnnes J.
Published: December 2007

This paper describes the pre-planning, design, selection and field test results of a state-of-the-art solids control system purpose built for development drilling of ‘V’ field wells. After contracting the Britannia as the prime drilling rig for the ‘V’ Field development drilling, Taywood-Santa Fe, the operator of the Britannia, prepared the rig for a major upgrade to equip the rig with the most technically advanced drilling equipment existing, to ensure fast efficient Southern North Sea development drilling.
Prediction of Average Cutting Size While Drilling Shales
Authors: Hayatdavoudi A. , Durugbor N. C. , Ghalambor A. , Okoye C.
Published: December 2007

The consensus among drilling personnel is that shale shaker as a primary solids control tool should reject the shale cuttings at first pass. In our effort to contribute to the design of a new shaker system, a basic and fundamental need was recognized with regard to the magnitude of power needed to generate a given or average size of shale cutting. The logic was that the power expended at the rock face, excluding the effect of hydrational and in-situ stresses, could be correlated with the shale cutting (chip) average size as has been done in comminution theories.

Following this logic, two detailed sets of field tests, one in Nigeria and one in Lafayette Parish, Louisiana, were analyzed for two different hole sizes. The results showed a good correlation between power input-output and average cutting size for both 8 1/2 and 6 5/8 inch drill bits.
Calculation of Relative Permeabilities From Displacement Measurements of Their Ratios
Authors: Loomis A.G. , Crowell D.C.
Published: December 2007

Individual relative permeabilities in both gas-oil and water-oil systems are required for reservoir engineering applications to evaluate oil displacement in steeply dipping reservoirs where gravitational effects are important. Although the individual values as functions of saturation may be established by applying steady-state, semi-static or capillary methods, it is highly desirable to calculate individual relative permeabilities from their ratio, as measured by the rapid displacement method now in general use for core samples. Three proposed methods for determining individual relative permeabilities have been compared - the Johnson-Bossler-Naumann, the Higgins and the "alternate method" - and excellent agreement was obtained for typical core samples. However, the foregoing methods can be applied with assurance to oil-water systems only when the system is oil-wet, but they cannot be recommended for water-wet systems.

Introduction

As pointed out by Johnson, Bossler and Naumann, individual permeabilities in gas-oil and water-oil systems are required for several reservoir engineering applications such as the evaluation of oil displacement where gravitation effects are significant, i.e., a water drive or crestal gas injection in a steeply dippling reservoir. Individual relative permeabilities for both types of system as functions of the saturation may be accurately measured by steady-state, semi-static or capillary methods. However, the unsteady-state displacement method is now in general use, because of its rapidity and reliability for both gas-oil and water-oil systems, in the latter case provided that the system is clearly oil-wet. Since relative permeability ratio as a valid function of saturation is measured by the displacement method, it is desirable to develop methods to obtain the individual relative permeabilities from their measured ratios. Such methods have been published by Johnson, Bossler and Naumann and by Higgins, both for gas-oil and water-oil systems.
New Wellhead Equipment for Old Oilfields
Authors: Bazile D. J. , Kluck L. M.
Published: December 2007

The purpose of this paper is to illustrate the benefits of a new wellhead design which is a variation of the independent screwed wellhead equipment (ISWE) presently on the market. The design offers most of the performance characteristics of low pressure flanged equipment up to 3000 psi, but at a substantial initial cost savings. The application is for moderate depth wells and/or Enhanced Oil Recovery (EOR) fields, that have limited flowback potential.
Unique Well Control Choke: Design Objectives vs. Commercial Field Performance
Authors: Cain L. L.
Published: December 2007

This paper discusses some objectionable operating characteristics of most present day conventional well control chokes. It then sets forth design objectives for a different type choke to overcome these objectionable characteristics. The paper then describes the final design, presents some performance charts for comparison to conventional chokes, and relates general field performance of the choke in commercial service.
Prediction of Cement Slurry Laminar Pressure Drops by Rotational Viscometry
Authors: Denis J. H. , Guillot D. J.
Published: December 2007

The flow behaviour of cement slurries, as measured with different types of equipment – a pilot-scale pipe viscometer, a Searl and a Couette coaxial cylinder viscometer – is analyzed.

The dimension of the flow geometries, respectively pipe diameter and annular gap size, was varied to detect the presence of an apparent slippage at the wall.

Different cement formulations were tested including a wide range of specific gravity from 1.7 to 2.2. Experimental flow curves were also compared for a polymer solution, and two water-base bentonitic muds.

For cement slurries, experimental results show that the flow curves obtained with the pipe and the Searl viscometer are very similar. The abrupt increase in viscosity at low shear-rates is attributed to the existence of a yield stress (τy), For stresses lower than τy, flow is still observed in both cases. The size dependence of the flow curves indicates that such a behaviour can be attributed to an apparent slippage at the wall. For stresses higher than τy little or no slippage is observable, and slurries exhibit a shear thinning behaviour that can be well fitted to a power law model from 30 to 500 s−1.

Different methods of calculating pressure drops in pipe flow from rotational viscometer data are presented. Their precision and limitations are compared. As a conclusion, it is established that laminar pipe flow pressure losses can reliably be predicted from rotational viscometer measurements if made on representative samples using equipment which minimizes particle centrifugation e.g. Searl systems instead of Couette systems.
Application of the 1987 IADC Roller Bit Classification System
Authors: Winters W. J. , Senger J. , Oliver M. S.
Published: December 2007

The IADC (International Association of Drilling Contractors) roller bit classification system provides a convenient method for categorizing rock, bits according to their design features and intended applications. The system has been used worldwide since 1972. The 1987 version includes improvements which reflect the latest design trends in roller cone bits.

This paper explains the IADC roller bit classification code. Current classification charts are shown for major bit manufacturers. The relationship between IADC code, bit design factors, and operating guidelines is discussed. Examples depict the major design features included in the code.
Diamond Bit Handling and Operation
Authors: Allamon J. P. , McKown T. , Hill D. , Brooks B. A. , Bayoud B. B. , Winters W. J.
Published: December 2007

The predominant experience throughout the drilling industry is with roller cone rock bits. However, diamond bit use has increased substantially in the past five years and continued increases are likely. Diamond bits are different enough in their design and function that they require distinctly different handling and operating procedures. This paper describes such procedures from the point the bit is unboxed, through make-up in the rotary table, tripping into the hole, washing and reaming to bottom (with attention to downhole motors), establishing a new bottomhole pattern, identifying pumpoff effects if present, establishing a satisfactory penetration rate, responding to formation changes, and recognizing and diagnosing indications that may lead to the decision to trip out of the hole. This paper bridges the gap between two other related papers which describe how new diamond bits are classified before they go in the hole23 and how worn diamond bits are graded once they are out of the hole24.
Drilling and Workover Experiences in the Greater Ekofisk Area
Authors: Anvik H. K. , Gibson W. R.
Published: December 2007

Since its discovery in 1969, the Ekofisk Area has developed into one of the most industrious oil centers in the North Sea. The Ekofisk Area presently encompasses twenty-five permanent platforms of which eleven are production/injection platforms with over 125 active wells. To date, 113 workovers have been performed on these wells. Production from the Ekofisk Area peaked on February 8, 1980, when 618,000 BOPD and 1,860 MMSCFD gas were produced. Development drilling activity peaked in late 1979 when there were ten active drilling or workover rigs on nine platforms. Today, there are four drilling and workover crews active in the area.

Reservoir depletion and compaction and the resulting seabed subsidence have altered drilling and workover operations over the past six years. This paper discusses how current drilling and workover practices have evolved in the Ekofisk Area.