bluuebunny/crossref_metadata_2025 huggingface dataset:
The Evaluation of Prudhoe Bay Waterflood Conformance and Reservoir Characterization by Thermal Modeling
Authors: Severson C. D. , Selisker G. R.
Published: December 2007

The evaluation of vertical sweep has been a long standing problem when determining waterflood efficiency in massive sandstones. As a result of reservoir heterogeneities and gravitational effects the vertical distribution of water near an injection well is typically different than its distribution in the reservoir. A thermal modeling approach has been successfully applied to this problem in the Sadlerochit sands at the Prudhoe Bay field to attain a greater understanding of the vertical sweep efficiency in a portion of this reservoir.

A thermal simulator was used to construct a 3-D model of one half of a 320 acre inverted 9-spot waterflood pattern in the Flow Station 2 waterflood area of Prudhoe Bay. The model was history matched to a temperature profile taken in a replacement injector drilled 720 feet (220m) away from its original location. The amount and location of reservoir cooling observed is a function of the water volume that has passed through it at a given location and its associated conductive and convective cooling. The replacement well modeled was drilled 4.75 years after injection had been initiated in the original well. The analysis thus provides an understanding of the vertical water distribution in the reservoir 720 feet (220m) from an injector, 4.75 years after the initiation of secondary recovery.

The producing sand modeled is approximately 170 feet thick and is characterized by a high permeability (0.1-5.0 darcy) thief zone at its top and 0.5 to 1.0 darcy sands below. In this waterflood pattern approximately 62% of the injectant had entered this thief zone. Thermal modeling indicated that 60% of the water had slumped from this thief interval into the sands below, 720 feet (220 m) from its injection point. This result indicates that although the thief zone has taken a high percentage of the water injected into the pattern, the vertical distribution of that water in the reservoir is far different from its distribution at the sand face as measured in the wellbore. By quantifying the volume of water that slumped out of the thief zone, an estimate of vertical permeability was determined and our understanding of vertical sweep efficiency greatly enhanced.
An Improved Linear Chemical Model for Alkaline Steamflooding
Authors: Okoye C. U. , Ping-Hu W. , Oungpasuk P. , Hayatdavoudi A.
Published: December 2007

Laboratory displacement tests using alkaline steamflood and conventional steamflood were successfully conducted. The results from the experiments were used to obtain correlation equations which in turn were used to simulate oil recovery performances.

A chemical displacement model which incorporates the thermal and chemical oil recovery mechanisms was used to history match the experimental oil recovery performances. The model prediction of the oil recovery performances matches fairly well with the experimental results. Furthermore, the model was tested with data obtained from the displacement tests and it led to some modification and adjustment until its application for history matching and prediction became satisfactory.

The model predicts higher oil recovery for caustic steamflooding over conventional steamflooding and agrees quite well with the experimental results obtained. The experimental results show that caustic steamflooding recovers more oil with increase in temperature, but above 300°F the incremental oil recovery becomes insignificant. The optimum temperature for enhanced oil recovery by caustic steamflood seems to be about 300°F. At a given temperature caustic steamflooding recovers more oil than conventional steamflood by between 18 to 35% and 8 to 13% of the original oil in place for primary and secondary recovery processes respectively.
A Simplified Approach for In-Situ Characterization of Desorption Properties of Coal Seams
Authors: Anbarci K. , Ertekin T.
Published: December 2007

A simplified analysis technique to determine the desorption characteristics of coal seams using pressure transient analysis is presented. The proposed technique is based on formulation of single phase gas flow in coal seams with unsteady state sorption/diffusion phenomena in coal matrix and laminar flow in cleat system. The matrix geometry is represented by using spherical elements.

A line source solution which defines the pressure distribution in an infinite-acting radial-cylindrical coal seam is used in the development of the proposed analysis technique. The simplified analysis presented in this paper is first tested against a previously developed closed form solution which describes the pressure transient behavior of coal seams. The proposed solution shows excellent agreement with this more rigorous solution, and its versatility is demonstrated through a simple analysis procedure which does not require the use of computationally laborious functional groups. Furthermore, a pressure transient data generated by a coal seam degasification numerical model is analyzed successfully using the methodology presented here. As an example application of the proposed technique to the analysis of drawdown test data is also included.

The proposed inverse solution procedure which is devised as a viable pressure transient analysis technique is applicable to coal seams and other unconventional gas reservoirs where adsorption/desorption phenomena are effective. The methodology introduced in this paper has the potential of providing the necessary tools that can be used in in-situ determination of the transport properties and the sorption characteristics of the coalbed methane reservoirs.
A Numerical Well Test Model
Authors: Puchyr P. J.
Published: December 2007

This paper describes a pressure transient analysis model which uses a numerical reservoir simulator to generate the pressure solutions. The accuracy of the solution is controlled by the grid and the wellbore-reservoir interaction. The methods used to construct the grid, and the representation of the wellbore-reservoir interaction are described. The simulation results are compared to a new large compressibility analytic solution, and to conventional analytic solutions.
Simulation of Slattery South Field, a Minnelusa ‘A’ Reservoir
Authors: Towler B. F.
Published: December 2007

A Reservoir Simulation study of the Slattery South field has been made to determine the drive mechanisms present in the field and to determine the amount of oil that has been produced from under eighty undeveloped acres in sec 30 of the field in order to resolve a drainage dispute. The primary drive mechanism has been shown to be solution gas drive in conjunction with fluid expansion and gravity drainage. Of the 308,928 STB of oil drained from the offended lease, 107,145 STB has been produced in well Burroughs A-18, and 131,420 STB has been produced in Ham Krause No.1.
Delineation of Favorable Areas for EOR From Differential Oil-in-Place Calculations in Bell Creek Field, Montana
Authors: Cheng A. M. , Sharma B.
Published: December 2007

Based on examination of the distribution of differential oil-in-place (OIP) in a reservoir, a method is presented to identify the effect of geological heterogeneities on nonuniform oil production. A well differential oil-in-place (DOIP) is defined by the equation: DOIP = volumetric OIP at a given spacing − material balance equation OIP. This method is based on the theory that positive differential OIP areas could indicate the presence of geological heterogeneities like high clay content, sealing faults, or different types of flow barriers, whereas negative differential OIP areas may imply presence of highly permeable clean sands, nonsealing faults, fractures, etc. By using the fairly complete geological and engineering data from 54 wells in the four sections enclosing the Department of Energy Tertiary Incentive Project (TIP) area of Bell Creek (MT) field, a differential OIP map was prepared. The map indicated several areas with significantly positive and negative differential OIP anomalies.

An overlay of the DOIP map with maps of structural anomaly, clay content, porosity, permeability, Dykstra-Parsons coefficient, and log-derived heterogeneity index indicated that low-permeability valley-fill sediments with a high degree of clay content and several sealing faults coincided with areas having a significantly positive differential OIP. High-permeability barrier sandstones adjoined by numerous small, conductive faults (throws around 10 ~ 20 ft) with excellent drainage efficiency were responsible for a significantly negative differential OIP. DOIP contour patterns indicated that optimum injection sweep efficiency could be obtained by locating the injectors parallel to a cluster of differential oil-in-place contour lines covering the area to be flooded.

The differential OIP was strongly dependent on geological heterogeneities and was an effective index for measuring the role of different heterogeneities on oil production in a reservoir. Main applications of the method are to determine: (1) remaining oil reserves, (2) geological heterogeneities, (3) well drainage area and efficiency, (4) optimal well spacing, and (5) best injection and production well sites for waterflooding, infill drilling, EOR, and horizontal well drilling programs. Results of the method can be used independently or integrated with other information for optimal reservoir production planning.
Application of PD' Well Testing of Naturally Fractured Reservoirs
Authors: Okoye C. U. , Songmuang A. , Ghalambor A.
Published: December 2007

This study presents the exact semi-analytical dimensionless pressure derivative solutions of transient pressure in naturally fractured reservoirs with pseudosteady state and transient stat interporosity flows. Integration by part technique was used to obtain in Laplace space dimensionless pressure derivative solutions which were used to generate new type curves. The type curves are dimensionless pressure derivative and dimensionless pressure-pressure derivative functions.

Dimensionless pressure-pressure derivative type curves are easier to use than existing type curves for transient pressure analysis of natural fractured reservoirs because they require only horizontal sliding to obtain matching.

Some of the type curves were used to analyze and interpret published field examples of transient pressure data. The results of the analyses show good agreement with published results. The validity of both our results and the published results were varified by using them, as well as the given rock and fluid properties, to simulate transient pressures for the duration of the test periods. Comparison of the closeness of simulated pressures with given pressures provides a level of confidence in the models and type curves used for data analysis and interpretation.
Transient Pressure Analysis for Variable Rate Testing of Gas Wells
Authors: Samaniego V. F. , Cinco-Ley H.
Published: December 2007

A method is presented to analyze variable rate tests in gas wells considering the effect of damage and high-velocity flow. This is a direct method that allows an estimation of the turbulent term coefficient D and the skin factor without using a trial and error procedure. The methods are applicable to infinite acting radial flow.

The method considers a step-function approximation of the flow rate. It consists of two parts: a) a graph of ∂Δpp(p)∂t∑j=1N(qi−qj−1t−tj−1)

is made from which we can estimate the formation conductivity kh and b) a graph of 1.1513[Δpp(p)m1qN−[∑j=1N(qj−qj−1qN)log(t−tj−1)+log  (1ϕμ(pi)ct(pi)rw2)+log(4βtγ1)]   vs   qN

is made that yields an estimate of the parameter D and of the skin factor s. This method can also be applied to continuosly varying rate flow tests.
Estimating Fracture Height from Gamma Ray Spectroscopy of Radioactive Tracers: A Case Study
Authors: Willis G. B.
Published: December 2007

Five wells in the Big Horn Basin of Wyoming were perforated in the Phosphoria formation and subsequently treated with acid. Each of the acids was tagged with a radioactive isotope. Spectral gamma ray logs were then run to determine the effectiveness of the treatments. After processing and analyzing the data, two facts became evident: 1) Several pitfalls need to be avoided in selecting the isotope and designing how the acid is tagged. For example, the correct isotope must be selected with the correct specific gravity to allow the isotope to stay suspended in the treatment fluid and the borehole fluid must be displaced with non-radioactive fluid. 2) Looking at total gamma ray counts alone to determine isotope distribution is inconclusive and sometimes misleading because this does not distinguish between tracer material in the borehole from tracer material in the formation.

When gamma rays pass through any median such as formation, cement, and casing, Compton downscattering occurs.(1) By applying a weighted least squares (WLS) algorithm to the gamma spectroscopy data, the compton downscattering was taken into account to determine both borehole and formation components.

The geology of the formation, treatment design, isotope design and isotope selection are discussed as they apply to the log data. The logging procedure, processing of the log data, and log examples are presented in more detail as this is the main thrust of this paper.
Fracture Patterns in Low-Permeability-Sandstone Gas Reservoir Rocks in the Rocky Mountain Region
Authors: Laubach S. E.
Published: December 2007

Fracture permeability is of primary importance to producibility of gas from many low-permeability-sandstone gas reservoirs in the western United States, but the location, orientation, spacing, and connectedness of fractures in the subsurface is difficult to measure directly. The Upper Cretaceous Pictured Cliffs Sandstone (San Juan Basin, Colorado and New Mexico) and Frontier Formation (Green River Basin, Wyoming) form low-permeability gas reservoirs for which production data indicate locally important fracture permeability. In the wells studied, fractures are present in core or visible on borehole-imaging logs. Insight into the types of fracture patterns that may occur in these rocks could help guide exploration, completion, and stimulation strategies.

Maps of fractures provide the most accurate representation of fracture spatial distribution, trace length, connectivity, and size and shape of fracture-bounded blocks. In mis study, fracture patterns were characterized by mapping large exposures of Pictured Cliffs and Frontier sandstone along the margins of the San Juan and Green River Basins. A set of fractures is recognized in both formations that is interpreted as having formed in flat-lying rocks prior to local Tertiary folding and uplift. In contrast to the conventional map pattern of regional fractures, in which fractures are arranged in regularly spaced, orthogonal arrays, these fractures occur in discrete swarms separated laterally by domains that either lack fractures or that have only rare fractures. These less fractured domains may be as much as several hundreds of meters wide. Within swarms, fractures are well interconnected along the length of the swarm, but poorly interconnected across the width of the swarm. Fractures between swarms are commonly isolated. For the Pictured Cliffs and Frontier outcrops that were studied, the fracture pattern is self-similar over scales ranging from outcrop to interwell scale with fractal dimension D = 1.2. In the low-permeability sandstones of the Rocky Mountain region, irregularly spaced fracture swarms are potential targets for gas exploration and should be incorporated into fractured-reservoir models.
An Improved Gelled Oil System for High-Temperature Fracturing Applications
Authors: Cramer D. D. , Dawson J. , Ouabdesselam M.
Published: December 2007

A gelled oil system has been developed for high temperature fracturing treatments. It uses several innovations, including two-stage gelation and a liquid gel breaker. The system works by adhering to rigorous testing and quality control procedures. Case histories in the Williston and D-J Basins document the results obtained with this improved system.
The Effects of Viscoelasticity on Friction Pressure of Fracturing Fluids
Authors: Keck R. G.
Published: December 2007

Despite the existence of many correlations to predict the friction pressures of fracturing fluids, there is little understanding of the effects of viscoelastic properties on this behavior. One reason for the relative lack of understanding of this problem is that the interactions between the turbulent velocity fluctuations and the viscoelastic fluid properties that cause the observed friction pressures are extremely complex. As a result, there are no theoretically-based methods for either pipe diameter scale-up or friction pressure predictions for fracturing fluids.

This paper presents an attempt to predict turbulent friction pressures of fracturing fluids by extending results of a numerical simulation for viscoelastic fluids found in the literature. The literature work provides near-wall velocity profiles for two viscoelastic fluid models. These profiles are integrated to generate friction factor versus Reynolds number expressions with the Deborah number as a parameter. Comparison to available data shows good agreement but requires an independent calculation for the Deborah number. Calculations using three Deborah number correlations yield inconsistent results. The lack of agreement between the theory and the data suggests increased modeling sophistication is needed to predict friction pressures of fracturing fluids in turbulent pipe flow.
Slant-Hole Completion Test in the Piceance Basin, Colorado
Authors: Myal F. R. , Frohne K-H.
Published: December 2007

The Piceance Basin of western Colorado contains a major gas resource in the tight naturally fractured sandstones, siltstones and coals in the Mesaverde. The objective of the Slant Hole Completion Test, funded by the U.S. Department of Energy, is to evaluate directional and horizontal drilling as an alternate development strategy for these reservoirs.

The well is located 700 ft south of the DOE Multiwell Experiment site in Section 34, T6S, R94W, Garfield County, Colorado. The hole was designed to intersect the paludal Mesaverde at 60° beneath the Multiwell pad and continue north to intersect the Cozzette close to 90°. The well is positioned to drill normal to the regional fracture system. Coring operations included a coal pressure core, 276 ft of conventional core across two paludal sandstones, and 118 ft of conventional core perpendicular to the natural fracture system in the Cozzette.

Drilling operations proceeded as planned through the first build interval, pressure coring, and conventional coring in the 60° hole. Subsequent caving in the coal and in the adjacent naturally fractured siltstone, in conjunction with lost circulation in the Rollins, necessitated prematurely running 7-in. casing below the Rollins. The remaining 800 ft of hole drilled was 6-in. diameter, cased with 4-1/2-in. liner. The high hole angle, in conjunction with the long tangent (60°) section (1,824 ft), made sliding the 4-3/4-in. motors in the second build extremely difficult. Drillpipe conveyed logging operations were successfully conducted in the Cozzette.
Productivity of Horizontal Wells
Authors: Al-Haddad S. M. , Crafton J. W.
Published: December 2007

Many horizontal wells are being drilled all over the world. One of the objectives is to increase the well productivity, compared to vertical wells. This increase in productivity occurs in a naturally fractured reservoir because many fissures are intercepted by the horizontal well. A two phase (oil and water), two dimensional simulation model, that uses the single porosity formulation and divides the reservoir into blocks that contain either matrix or fracture, has been solved implicitly to simulate naturally fractured reservoirs. This simulator is able to represent the transverse imbibition observed in a laboratory experiment. The impact of horizontal and vertical wells on the produced water oil ratio and the cumulative oil recovery, has been studied for fractured reservoirs with different matrix permeabilities. The horizontal well, in general, gives a lower water oil ratio and a higher cumulative oil recovery. It was also found that the horizontal well productivity is better in low matrix permeability, fractured reservoirs.
Extension of Fracture Pressure Decline Curve Analysis to Fissured Formations
Authors: Mukherjee H. , Larkin S. , Kordziel W.
Published: December 2007

Currently, a major part of our oil and natural gas production comes from wells in tight naturally fractured or fissured formations. In many cases, the commercial viability of these wells depends on the success of hydraulic fracturing. Properly designed fracture treatment enhances the production from these wells substantially. However, the complexities of fracture treatment of such reservoirs often lead to premature screenouts due to accelerated leakoff in the fissures from stress sensitivity. Normally, the fissures dilate with increased treatment pressure and the permeability of these fissures increases exponentially as suggested by Walsh1 model for stress sensitive fissures. Such stress or pressure sensitivity of fissures need to be diagnosed and remedied before a successful optimum treatment can be achieved in these formations.

Conventional minifrac analysis of injection pressure and decline pressure often helps in diagnosis of such pressure dependent leakoff case. The original Nolte decline analysis was for wall building fluids or for a constant leakoff case. When this analysis is applied to the pressure dependent leakoff case, the fluid efficiency is over-predicted suggesting inadequate pad volume and pump rate requirements. Such designs with inadequate pad volumes often cause proppant dehydration and premature screenout.

This paper presents a modification to Nolte's decline curve analysis that helps in the diagnosis and evaluation of pressure dependent leakoff. It is also observed that such analysis leads to substantially lower fluid efficiency calculation resulting in increased pad volume and treatment rate. By applying the suggested method of analysis an empirical relation between the net pressure and fluid leakoff coefficient can be obtained.
Fracturing Fluid Loss at High ∆P: Laboratory Tests and Field Applications
Authors: McMechan Dave E.
Published: December 2007

An increasing number of gas wells that exhibit a large difference in reservoir pressure and fracture treating pressure recently have become candidates for hydraulic fracturing. When these reservoir conditions are encountered, the result is an abnormally high pressure differential driving the fluid leakoff mechanism during the hydraulic fracturing treatment. In some deep well applications, fluid loss differential pressures (FLDP) up to 10,000 psi have been witnessed.

Neither laboratory core testing nor conventional minifrac techniques have accurately predicted fluid loss behavior for fracturing treatments in these wells. Standard laboratory test procedures use differential pressures of 1,000 psi (as per API recommended test procedures) to determine fluid loss coefficients. Minifrac test methods and analysis techniques currently used for field application estimates of fluid loss parameters were modeled after data measured in gas reservoirs where normal fluid loss differential pressures occur.

Laboratory fluid loss testing typically has predicted significantly less fluid loss than actually is encountered. Use of this data in computerized fracturing simulators to design the treatment has resulted in many premature screenouts. Conversely, minifrac tests tend to be pessimistic and overpredict the fluid loss in wells with very high FLDP's. A number of treatments have been completed successfully following minifrac tests that predicted screenouts for the jobs actually pumped.

This paper reports on laboratory fluid loss tests conducted at differential pressures of up to 9,000 psi to determine the nature of the fluid loss occurring in these wells. Significant spurt volumes have been observed even on cores of less than 1 md permeability with fluid systems that do not exhibit measurable spurt loss at the conventional 1,000 psi test pressure differential. Also, the fluid loss coefficients (Cw values) have varied little with escalating pressure differential, contrary to many published correlations.1 Results from actual field cases also are reviewed as illustrations where the observed FLDP was several thousand psi during fracturing.
New Concepts for Vertical Drilling of Boreholes
Authors: Oppelt J. , Chur C. , Feld D. , Juergens R.
Published: December 2007

Directional drilling equipment has been developing from conventional whipstock rotary assemblies over downhole motors with bent housing to navigational motors. A self-contained downhole automatic closed loop system is recognized as being the next major development milestone. As a first step such a drilling tool which automatically compensates for any deviation from the vertical direction has been introduced within the German scientific super-deep drilling project KTB. Technical function of the tool as well as recent field experience is reported.
Pore Pressure Ahead of the Bit
Authors: Hanson J. M. , Tibbitts G. A.
Published: December 2007

This paper discusses the results of a numerical study of the effects of wellbore overpressure on the effective stress encountered by a PDC cutter. Results suggest that the length of time for the creation of the work face damage zone may strongly influence the effective rock strength felt by the bit in low strength formations. Field observations of large ( > 0.5 in.) cutter bit performance in weak formations can be explained by these model results.
Hydrodynamics of the Drilling in Deep, Thick, Abnormal Pressure Reservoirs
Authors: Mnatsakanov A. V. , Litvinov A. I. , Zadvornykh V. N.
Published: December 2007

This paper reports a general hydrodynamics theory of steady-state isothermal flow of non-linear viscoplastic drilling muds through the annular space of the well. The theory has been developed to fit an optimal circulation program design for conditions of high probability of circulation losses and/or formation fluid kickings. Mud compressibility problems are discussed as well as the adequacy of different rheological models to the behaviour of various mud types.

There are briefly stated fundamentals of the engineering procedure used to design optimized rheohydraulics programs for drilling wells. The said procedure with the corresponding computer program has been successfully used for drilling in deep thick abnormal pressure reservoirs of several Soviet oil and gas fields (Tengiz and others).
Helicopter-Supported Drilling Operation in Papua New Guinea
Authors: Wagner E. R. , Juneau M. S.
Published: December 2007

Drilling cost per foot of Chevron's helilift drilling operation in the remote Southern Highlands of Papua New Guinea was reduced from 1360 to 267 $/ft (4462 to 876$/m) during the period from 1985 to 1989. The operation provides many challenges, as it is thousands of miles from major oil-field supply centers. This requires advanced well-planning and logistical management of drilling materials so that they arrive at the drilling rig in a timely matter. The wells are also drilled into structurally complex geology without the aid of seismic data which can lead to unexpected results. The drilling rigs are entirely supported by helicopters from a forward supply base and are completely heli-transportable. PNG's operational improvement and optimization program during a 5 year period had a four-fold decrease in drilling dollars per foot.
Development and Field Trial of a Biodegradable Invert Emulsion Fluid
Authors: Peresich R. L. , Burrell B. R. , Prentice G. M.
Published: December 2007

This paper presents the development and field trial of a novel biodegradable invert emulsion drilling fluid.

Responding to environmental concerns and legislation restricting the discharge of mineral oil base drilling fluids, research into biodegradable alternatives commenced in the mid 1980's. Laboratory testing found that some complex esters form stable invert emulsion fluids and are readily biodegradable in both aerobic and anaerobic environments.

After reviewing the laboratory and environmental data, the Norwegian Government agencies (SFT and NPD) granted their approval for a limited field trial of the new ester mud system. The Ester mud system was successfully used in an Ula Field appraisal well. Hole conditions and drilling rates were comparable to nearby wells drilled with conventional Oil Based Mud. Compared to an offset well drilled with a water base mud, normalised drilling time savings of 13.2 days were realised over two hole sections.

Toxicity levels on new and used mud samples have been well within Norwegian government statutorylimits for drilling muds. An independent laboratory biodegradation test on used field mud found it81% degraded after 28 days, allowing the ester mud to be classed as "readily biodegradable" by European Community (EC) protocol.

To assess the environmental impact, a long-term seabed survey programme at the wellsite is ongoing.
Chemistry and Field Practice of High-Temperature Drilling Fluids in Hungary
Authors: Dormán J.
Published: December 2007

The development of new high-temperature drilling fluid formulations and field practice optimization is a major task worldwide. The role of divalent ions in colloidal stabilization led to the field proven Ca-muds especially under high-temperature conditions. In case of gyp-muds however Ca-tolerant dispersants, protective colloids and specialty chemicals must be used. Sulfomethylated (chemically crosslinked) lignite derivatives have been developed and used extensively for rheology and filtration control in deep and hot wells in Hungary. Optimized combination of modified lignites and selected low and high molecular weight synthetic polymers gave further improvement in temperature stability of high weight Ca-muds. Field results in several wells proved the performance of new synergistic blends at temperatures up to 490-500 K (225 °C).

Field and lab data showed the very special role of chemical equilibrium.

On theoretical basis and experience gained recently new lime mud formulation was developed. The relatively high filtrate Ca++ - inspite of high pH - combined with K-ions provides exceptional inhibitive properties.

The very special combination of synthetic polymers gives extreme temperature stability and unique performance.

Ionic and polymeric colloidal stabilization opens nwe ways in high-temperature drilling fluid formulations.

These systems have been successfully used in HPHT wells and show new promises in geothermal drilling as well.
Noise Reduction and Improved Hearing Protection on MODUS
Authors: Smith G. D. , Gloeckler D.
Published: December 2007

This paper will report on a program which has been initiated to improve working conditions on MODUS(Mobile Offshore Drilling Units) through reduction of noise level exposures for all personnel. Theprogram contains four (4) approaches to the problems of air and structure borne noise on MODUS and will review the modifications that have been implemented or will be completed to provide lower levels ofexposure through hardware or systems changes as well as improved personal protection.
Risk Analysis of Drilling and Well Operations
Authors: Ostebo R. , Tronstad L. , Fikse T.
Published: December 2007

Formal safety assessments have become a regulatory requirement in Norway and the UK. This paper outlines different types of risk and safety analysis methods that can be used to evaluate the safety of drilling operations, associated equipment and installations.
Improved Heave Compensation
Authors: Baker R. J.
Published: December 2007

The efficiency of drilling operations carried out from floating drilling units in hostile environments is adversely affected by movement of the vessel, particularly heave. Over the years various systems have been developed in an endeavour to minimise the problems caused. This paper describes the impact that heave has on the efficiency of floating drilling operations, the compensatory methods and systems that have been used to date, and highlights some new developments that promise to improve safety and drilling performance, while reducing the potential adverse environmental effects of drilling operations.
Downhole Blowout Preventer
Authors: Sangesland S. , Sivertsen A. , Hiorth E.
Published: December 2007

A Down Hole Blow Out Preventer (DHBOP) for the downhole control of gas kick has been developed. Tests performed on an onshore drilling rig with simulated gas kick have demonstrated that the tool can effectively seal off the borehole, while mud of adequate density (to control the borehole pressure) is circulated above the Down Hole Blow Out Preventer.
Removal of a Kick With the Partition Method
Authors: Fleckenstein W. W. , Mitchell B. J.
Published: December 2007

This paper compares kick removal variables between the "Partition Method", the Driller's Method, and the Wait and Weight Method. In the Partition Method, the kick is circulated out of the wellbore in discrete partitions which yield lower pressures within the wellbore, casing and surface equipment than the two conventional methods.
A Study of Load-Shape Factors of Jackup Legs With Raw Water Guides
Authors: Jensen A. G. , Orbe F. G.
Published: December 2007

Shape factors for five different configurations of a triangular jack-up leg have been determined through load measurements on scale models in a wind tunnel.

The drag, lift, and yaw-moment shape factors of the different configurations were determined in the search for an optimal arrangementof the three raw water pipes that minimize the current load on the combined jack-up leg-raw water pipe-structure.
Horizontal Drilling in a Depleted Sour Gas Reservoir: A New Application
Authors: Niggemann L. , Ehlers R.
Published: December 2007

A horizontal well has been drilled in the depleted Siedenburg sour gas field with an H2S content of 6.7%. Concession holders of this field, located in N-W Germany, are BEB and Mobil.

The field has been producing since its discovery in 1964, from 2 reservoirs, the Middle Bunter sandstone and the Main Dolomite, both now depleted to a pore pressure gradient of 0.5 and 0.3 bar/10 m respectively.

A horizontal well in the Main Dolomite, if feasible, was considered as the best solution to increase recovery from the reservoir, by reducing the water influx and creating greater access to the reservoir by increasing millidarcy-feet.

After the reservoir engineering aspects of this project indicated a potential 5-8 fold production increase with a 400 m long horizontal completion interval, the drilling and completion aspects were analyzed for technical feasibility.

Restrictions in surface location and target description (2 intermediate targets) required build rates of appr. 4°/30 m in the 8-3/8" hole section and a medium radius profile of about 13.5°/30 m in the 5- 7/8" section. Both drilling phases had to be accomplished in geologically difficult formations with tight target tolerances.

The proposed entry point was planned to be as close as possible to the old Z-2 well in an area of the reservoir where best facies was expected. The walk tendency experienced in the offset well Z-2 was used for planning the final profile and therefore no directional work was required in the top hole section to line up the well for the final target direction.

Finally it was required to drill horizontally with a hydrostatic overbalance as high as 240 bar to maintain safe operating conditions in a severe H2S environment. The hydrostatic overbalance of that magnitude required precautions to be taken with both mud properties and BHA design to avoid differential sticking. The completion design included corrosion resistant alloy (CRA) for the unprotected pipe below the 7" liner top as well as for the 4-1/2" slotted liner covering the horizontal section.
Portfolio Modeling: A Technique for Sophisticated Oil and Gas Investors
Authors: Hightower M. L. , David A.
Published: December 2007

In the past three decades, much work has been conducted in the development and application of various analytical techniques used in investment decisions. Two of the most powerful of these techniques include risk analysis and portfolio analysis. Because of the speculative nature of the petroleum industry, risk analysis has become readily acceptable and widely used by most oil and gas investors. Meanwhile, portfolio analysis has gained little acceptance and remains a mystery to most of the petroleum sector. Like risk analysis, portfolio analysis evaluates projects based upon the investment's expected return and its perceived risk or uncertainty. However, while risk analysis limits its perspective to the merits of the individual project, portfolio analysis expands this view to include the effects and contributions that potential projects will have on the investor's entire portfolio. In turn, portfolio analysis broadens the restrictive, myopic view of selecting projects based solely on individual merit and criteria and allows the investor to determine how potential investments will affect the goals and objectives of his overall portfolio.

This analytical technique is based upon modern portfolio theory which provides a conceptual framework for selecting projects in order to create portfolios that offer the best combination of risk and return. Within this framework, Harry Markowitz proposed a mathematical model that utilizes quantifiable risk/return parameters to create efficient and optimal portfolios designed to meet the goals and risk preferences of the large private or institutional investor. While sophisticated investment managers have successfully applied this portfolio model to the capital markets, this quantitative method has obtained little exposure in the oil industry. Earlier studies have shown, however, that the conceptual application of portfolio analysis has much merit and utility in the decision process employed by oil and gas investors. Yet none of these qualitative applications utilize the full potential that the Markowitz model provides.

While not applicable in its original form, the portfolio model needs modification to meet the investment objectives and information limitations characteristic of the oil industry. It is the objective of this paper to demonstrate how a modified model can be effectively applied to the selection process of petroleum ventures. To illustrate its applicability, this modeling technique is applied to an investment decision involving the construction of an exploratory drilling program. In this example, this analytical technique predicts how an efficient and optimal portfolio can be constructed given an opportunity set of investments and the goals of the oil and gas investor. It is believed that from this illustration investors will be able to effectively apply portfolio modeling as a tool to optimize their own selection of petroleum investments.
Xanthan and Welan: The Effects of Critical Polymer Concentration on Rheology and Fluid Performance
Authors: Powell J. W. , Parks C. F. , Seheult J. M.
Published: December 2007

Achieving optimal fluid performance with biopolymer viscosifiers, xanthan and welan, depends on reaching or exceeding a minimum or critical polymer concentration (CPC). CPC is affected by a variety of fluid and wellbore conditions, including: temperature and salinity, average shear rate, shear history, velocity gradients, hole angle, polymer configuration and rigidity, and the size, density, and concentration of suspended solids. The suspension and transport properties of xanthan and welan correlate directly to low-shear-rate-viscosity (LSRV) and elasticity (G'), properties which cannot be quantified with a conventional field viscometer. LSRV and G' are qualitatively related to a polymer's molecular rigidity and configuration, and quantitatively to the number of physical and chemical polymer chain associations, referred to as polymer networks and structures.
Waterflood Monitoring Technique Results in Improved Reservoir Management for the Hemlock Reservoir, McArthur River Field, Cook Inlet, Alaska
Authors: Starzer M. R. , Borden C. U. , Schoffmann A. B.
Published: December 2007

A peripheral waterflood monitoring method of subdividing the Hemlock Reservoir into areal groups has aided in development decisions for the McArthur River Field, Cook Inlet, Alaska. This analysis technique improved assessment of remaining development potential by separating the reservoir into more manageable areas. By respecting the inaccuracies associated with production data, the analysis method simplified reservoir management and improved performance predictions.

Seven "performance areas" were established to monitor waterflood performance and identify areas of remaining recovery potential. Each performance area represents an accounting block in which recovery and performance prediction methods were applied to monitor waterflood progress. Prediction methods for the undersaturated reservoir included water-oil ratio trending, material balance and decline analysis. Comparison of each area's performance with others and with analytical performance predictions easily identified local areas of unrealized potential. This method of waterflood management aided in assembling management strategies and promptly examining those strategies as conditions changed.
Development of Procedures for Hot Tap Welding Onto Sour Service Pipelines
Authors: Felix R. D. , Bruce W. A. , Threadgill P. L.
Published: December 2007

This paper describes the development of welding procedures for welding onto in-service pipelines that are used to transport mildly sour produced gas. The development of the procedure focused on obtaining a resulting weldment which met the hardness criterion of Rockwell C22 (Rc22), which is the maximum allowable hardness recommended in National Association of Corrosion Engineers (NACE) MR-01-75 to avoid sulfide stress cracking (SSC) in subsequent service. 1

Several techniques for minimizing weld hardness were investigated. Welds made included baseline single-pass welds at various heat inputs, standard multi-pass welds, multipass welds made at high heat inputs and various temper bead deposition sequences. The optimized procedure involved applying weld metal buttering to the fitting side of the weld joint by the fitting manufacturer prior to installation using preheat. Weld metal buttering was also used on the pipe side of the joint. The buttering was then ground to allow tempering by subsequent passes. A gas tungsten arc weld (GTAW) root pass with an autogenous remelt pass was used to allow tempering in the root region. A unique scheme to facilitate weld toe placement was devised to ensure that these areas received adequate tempering.

A quality assurance method for determining that the hardness criterion had been met was devised. Using this scheme, the suitability of the welding procedure was determined based on a series of measurements on confirmation welds made on the coupon that would later be removed by the action of the hot tap cutter.
Foundation Heave Induced by a Subgrade Cooling System Over Permafrost
Authors: Scher R. L.
Published: December 2007

The ADOT Jim River Maintenance Building, located over permafrost in central Alaska, has experienced significant floor heave following startup in late 1986 of an active subgrade cooling system (SCS), even though foundation soils appear to remain frozen year round. After constructing a new floor in mid-1987, cumulative floor heave by 1990 ranged from about 1-5 inches (25-127 mm). However, the annual heave rate has been decreasing as the mean frozen ground temperature progressively cools.

Published unfrozen moisture, hydraulic conductivity, and thermal induced heave relationships were used to reasonably model the recorded floor heave and rates. At Jim River, 25-50% of the heave recorded since mid-1987 may be associated with redistribution of unfrozen water under influence of thermal gradients established during operation of the SCS. The results suggest this phenomenon should be considered for some SCS designs, especially over warm permafrost.
State-of-the-Art Review of Nondestructive Testing with Computer-Assisted Tomography
Authors: Bansal A. , Islam M. R.
Published: December 2007

Computer assisted tomography (CAT) has been a revolutionary technique in medical radiology. Recently, CAT scanners started to be used as non-destructive testing facilities in different industrial applications. Most of the applications of the new technology are in the areas of petroleum engineering. Majority of this CAT scanner technology has been developed in the U.S.A. However, several Canadian companies have acquired CAT scanners and are using for novel commercial as well as research applications. This paper presents a comprehensive review of advances made in the areas of CAT scan technology as applied to the petroleum industry.

Recent efforts in developing CAT scan technology has been in the areas of core analysis methods. The ultimate objective is the quantitative monitoring of dynamic two- and three-phase experiments in porous media. Even though advances have been made in using CAT scan for quantitative evaluation of fluid flow, more research has to be done before gaining confidence in such a technique. This paper presents a critical review of recent research publications. Also, discussed is the possibility of using CAT scan as a unique reservoir characterization tool. Reservoir properties, such as direction and frequency of fractures, the presence of vuggs, stratification in the bedding plane, etc. may be identified only through non-destructive testing of reservoir cores. Various applications of CAT scanning to oil industry are discussed in detail.
Real Prospects for Further Utilization of Mineral Resources in the Arctic: Technology Adaption to Environment
Authors: Zamoshch M. N.
Published: December 2007

Development of mineral resources in the Arctic is fraught with distructive environmental effects of currently used technologies.Therefore a protest arises with the public against deposit mining. Presently in use reclamation methods are expensive, can't provide complete restoration of initial landscape, and reduce to a great extent numerous favourable effects of a technogenic landscape. Ecological problems of the Arctic might be successfully solved by designing technogenic landscapes before starting mining operations provided they are most fully adapted to environment. Maximum favourable result from technology adaptation might be reached in case of international cooperation of experience in mining and protecting mineral resources in the Arctic.
Horizontal Wells - A Test on Infinite Conductivity Solutions
Authors: Jelmert T. A. , Thompson L. G.
Published: December 2007

Line source solutions for uniform flux horizontal wells are well known The infinite conductivity well model has not received the same attention. An objective of the present paper is to investigate the behavior of some possible infinite conductivity well models. We test the properties of the step function and the piecewise linear rate density function.

We find that the linear rate density distribution model oscillates at late times. Depending on the solution strategy, these oscillations may come early or late in the second `radial flow period. We believe that this numerical phenomenon is connected to numerical interaction between steep gradients and the numerical Laplace transform inversion scheme. The solution resulting from the piecewise constant rate function is complete in the sense that it can handle all flow periods from the early linear to the pseudo steady period.

The results from the infinite conductivity models are compared to the results from the uniform flux model. For easy identification of possible linear flow periods, we plot the square-root derivative. A straight line at a constant value indicates that the pressure drop is a linear function of the square-root of time.