bluuebunny/crossref_metadata_2025 huggingface dataset:
Using a Pulse Test to Determine Pore Volume Compressibility in a Gulf of Mexico Unconsolidated Reservoir
Authors: Deskin R. H. , Tinker G. E. , Crawford G. E.
Published: December 2007

Pore volume compressibilities have a major impact on recovery estimates for unconsolidated sand reservoirs. A realistic estimate of the recovery factors is imperative to prospect development decisions. Confirmation of higher pore volume compressibilities may lead to development of new discoveries or preclude secondary recovery measures in complicated reservoir systems. By performing a pulse test at the East Breaks 165 field, an "in situ" measurement of pore volume compressibility for a producing Gulf of Mexico unconsolidated reservoir was obtained to verify the large compressibilities measured from uniaxial core testing.

The pulse test was run between two East Breaks 16S wells. High quality pressure data was obtained, and the formation’s diffusivity and transmissivity were determined. To extract the formation’s pore volume compressibility from the test data, key components of the reservoir had to be suitably identified. PVT work was required to confirm that the reservoir was not originally at its bubble-point as first assumed, and therefore, no free gas was present in the system to mask the pore volume compressibility. In addition, the approximated reservoir thickness produced an unrealistic estimate of pore volume compressibility. Consequently, a production log was run in the puiser well indicating that two-thirds of the perforated interval was not contributing to flow. Utilizing this additional information, the final pore volume compressibility derived from the pulse test compared favorably with the core data.

An outgrowth of this investigation was a better understanding of the suspected formation damage believed to be caused by fines migration. Interpretation of the related pressure build-ups reflected extremely high damage in both welk. The production log and a subsequent pulse neutron log confirmed the probability of significant fines movement in the formation. These results substantiated the deterioration of well productivity observed over the past three years. Identification of near wellbore damage and its cause will allow appropriate remedial work to recover lost well capacity and maximize reserves recovery.
Radial Response of a 2-MHz MWD Propagation Resistivity Sensor
Authors: Barnett W. C. , Meyer W. H.
Published: December 2007

Electromagnetic propagation resistivity sensors have become common in MWD logging applications. These tools are unique among resistivity sensors in that the depth of investigation of the phase shift and attenuation resistivity measurements varies dramatically with the formation resistivity, measuring deeper into the formation in higher resistivity environments. The fact that the depth of investigation can vary by more than a factor of two across a normal range of formation resistivities requires the log analyst to have an understanding of this phenomenon when performing both qualitative and quantitative interpretations of these logs. Other measurement characteristics such as regions of negative or sharply-rising radial response can produce log responses which may seem peculiar when compared to traditional induction logs or laterologs. However, the radial response in virtually any borehole and formation environment can be quickly determined by computer modeling. This modeling, coupled with comparisons between propagation resistivity and induction logs can provide the log analyst with an understanding of the radial response of these sensors and facilitate both qualitative and quantitative interpretations.
A Method for Porosity, Permeability, and Water-Saturation Estimates From Logs in Tight Gas Sands With Rugose Holes
Authors: Everett R. V. , Culbertson J. S. , Quircin M. C.
Published: December 2007

Log calculations of porosity and permeability from case studies on staged field experiment (SFE) wells sponsored by the Gas Research Institute (GRI) were compared to core. In good hole conditions, log-derived porosity and permeability compared to core analyses were favorable. However, when rugose hole occurred, pad-type tool measurements were questionable. A technique for reconstructing the bulk density reading in poor hole conditions was needed.

The conventional method to estimate the bulk density in rugose hole replaces the questioned density measurements with neutron or acoustic measurements. However, this conventional method may not represent the changes in the true bulk density. The new method employed, possible only if elemental log measurements are available, reconstructs the bulk density in terms of its probable magnitude using mineral information. The elemental measurements allow the derivation of mineralogy, which is valid in spite of rugosity.

The new method of density reconstruction in rugose hole used the log-calculated minerals. Porosity was calculated from the acoustic log and clay minerals. From these two porosity estimates and the matrix density derived from the minerals, an estimated maximum bulk density (bulk density derived from clay porosity) and minimum bulk density (bulk density derived from acoustic porosity) are calculated. In areas of good hole, the recorded bulk density was retained. In areas of rugose hole, the most probable bulk density was between this maximum bulk density and minimum bulk density. A discriminator system involving the caliper was used to determine the rugosity of the borehole.

Using the rugose hole discrimination, the dielectric and microresistivity log measurements were selectively utilized in good hole with log element-derived mineralogy to produce an estimate of variable porosity-cementation exponents, level by level. A "wet" resistivity, Ro ("wet" refers to the assumption of water without hydrocarbons in the pore space), was calculated and compared to measured resistivity where the hole was smooth. An overlay in a wet zone or shale zone verified the mineral modeling of clay type, abundance, water resistivity and porosity. The variable exponents were then used in water saturation calculations. The mineral-based methodology when logs of elemental concentrations were available, was applicable in spite of rugosity that invalidated the bulk density measurement. The calculations implementing the reconstructed density log resulted in favorable correlations with core porosity and, additionally, permeability and saturation on the GRI wells studied.
Investigation of Drilling Fluid Properties to Maximize Cement Displacement Efficiency
Authors: Smith T. R. , Ravi K. M.
Published: December 2007

This paper describes techniques for improving the percentage of wellbore volume that is circulated before cementing. The effects of drilling fluid filtercake deposits, aging of filtercake, mechanical scraping of the filtercake, and annular velocity on the displacement efficiency are discussed. Four different water-based drilling fluids (potassium acetate, potassium chloride, gypsum, and fresh water bentonite) used by Shell Canada in their day-to-day operations were investigated in this study.

A large-scale test apparatus was used for this study. The test apparatus consisted of a steel casing run inside a permeable core to realistically simulate a wellbore. The test procedure simulated conditions such as circulation, drill string tripping, drilling fluid conditioning, and cementing. A computerized tracer technique was developed to continually monitor the percentage of wellbore volume that was circulated. A continuous history of the wellbore was recorded when parameters such as annular velocity, drilling fluid rheology, and fluid loss of the drilling fluid were varied. Drilling fluid filtercake buildup and erosion were monitored throughout the test. After cementing, the test model was removed from the test well and cut into sections, and displacement efficiency was measured. The agreement between the measured displacement efficiency and calculated percentage circulatable hole volume verified the test method. The effects of modifying parameters such as drilling fluid properties, annular velocity, and mechanical scraping of filtercake on cement displacement efficiency are presented. Recommendations on which drilling fluids are most desirable for cement displacement efficiency are included.
Asphaltene Deposition: Development and Application of Polymeric Asphaltene Dispersants
Authors: Schantz S. S. , Stephenson W. K.
Published: December 2007

Asphaltene deposition has a significant detrimental effect on oilfield production. The key to effective treatment of asphaltene deposition is recognition of the problem. Asphaltenes can be identified and quantified using laboratory methods. In the past physical, mechanical and chemical treatments have been used to control asphaltene deposition in the oilfield. Chemical treatments have included aromatic solvents and low molecular weight dispersants. However, many of these treatments are ineffective.

Recently, technically and economically effective methods to control asphaltene-created production problems have been developed. These applications make use of a new polymeric dispersant/inhibitor at clean-up dosages of 1,000 to 10,000 ppm and continuous dosages of 50 to 400 ppm.

As a result of downhole clean-outs and chemical squeezes using the new dispersant/inhibitor, production increases have been achieved and maintained. Tank bottom and interface control has been achieved through continuous feed applications. In one case, an additional benefit of the treatment was increased effectiveness in demulsifying oil/water emulsions and maintaining cleaner discharge water.
New Simultaneous Operations Guidelines Enhance Safety of Offshore Operations
Authors: Gilbert D. L.
Published: December 2007

Exxon Company, U.S.A. has had a Simultaneous Operations Plan for offshore operations since 1978. The plan has provided valuable guidance in conducting safe and environmentally sound operations. However, new learnings identified opportunities to make the existing plan better. A task force formed to review Exxon’s Gulf of Mexico operations with regard to overall safety and emergency response capabilities concluded that an enhanced plan would assist in describing the procedures appropriate for conducting operations (production, drilling, construction, etc.) concurrently on offshore platforms. Exxon’s Offshore Division revised Simultaneous Operations Manual was subsequently published in November 1990. The new document, developed with input from field operations personnel, describes a series of minimum requirements for each simultaneous operations scenario. A definitions section provides an understanding of various equipment, conditions, activities, etc. which are addressed in the manual.

Provisions for deviating from the Manual’s requirements with management approval are included, provided special precautions and/or unique circumstances are involved. The process utilizes office automation (computer mail) which provides for timely responses to deviation requests. This system will also be used to track the types and frequency of deviations. This tracking capability will also provide input regarding future Manual revisions and ensuring that the Manual remains "evergreen."
Actions Needed To Comply With API RP 750 Management of Process Hazards for Offshore Facilities
Authors: Arnold K. E. , Roobaert N. C.
Published: December 2007

API RP 750, Management of Process Hazards, which does not include offshore facilities in its scope specifies the elements required of a safety management system. It is possible to comply with RP 750 by revising an existing API Recommended Practice and making minor revisions to existing safety systems already in use by most offshore operators. This paper describes how this can be accomplished in such a manner as to derive the benefits of having a safety management system, without subjecting the industry to an unnecessary and counterproductive burden of documentation.
Snubbing Unit Applications in Potentially High-Rate Gas Wells: A Case Study of the Anschutz Ranch East Unit, Summit County, Utah
Authors: Leggett R. B. , Griffith C. A. , Wesson H. R.
Published: December 2007

Snubbing has recently been implemented as a method of routine well-control during workovers and completions at the Anschutz Ranch East (ARE) field in Summit County, Utah. This action was taken in response to poor post-workover performance caused by a water retention problem in the Nugget sandstone formation with the use of water-base well-control fluids. The incremental expense of snubbing at ARE averaged 25–40% of the cost of a standard workover and was considered reasonable in view of the alternative of poor well performance with existing well-control methods.

The concept of snubbing as a "commonplace" well-control method at ARE represents a major departure from historical control methods employed there. The new experience gained with surface control of potentially high-rate, medium-pressure, retrograde gas wells may benefit other operators in planning and executing safe, efficient snubbing operations in wells with similar conditions.

A review of the decision logic which chose snubbing versus other alternative well-control methods is presented. In addition, an overview of job pre-planning activities is provided. Finally, a detailed discussion of actual implementation problems and solutions is given with particular emphasis on underbalanced drilling of plugs and fill.
Determining Effective Residual Oil Saturation for Mixed Wettability Reservoirs: Endicott Field, Alaska
Authors: Wood A. R. , Wilcox T. C. , MacDonald D. G. , Flynn J. J. , Angert P. F.
Published: December 2007

Waterflood residual oil saturation, in mixed wettability reservoirs, is often a strong function of pore volumes (PV) injected. The Endicott Field, Alaska displays typical mixed wettability behavior with coreflood remaining oil saturation varying from 40% at 1 PV to 12% at infinite PVs. Although only about 1 PV will be injected in the reservoir, surface film drainage may act to reduce oil saturation making determination of the correct effective residual oil saturation difficult.

Accurate determination of waterflood residual oil saturation is essential for assessment of waterflood performance and evaluation of enhanced recovery processes. To minimize uncertainty in predicting effective residual oil saturation in mixed wettability reservoirs it is necessary to consider the competing effects of relative permeability, gravity forces, and imbibition capillary pressure. A mechanistic simulation approach is presented for scaling up laboratory results, that considers all active forces.
An Integrated Approach EOR Evaluation of Production Scenarios in the Field Delineation Phase
Authors: Lemouzy P. M. , Eschard R. , Beucher H.
Published: December 2007

A method for evaluating the production scenarios in the delineation phase of an oil field is described, and illustrated with a synthetic example build from a Mesa Verde (Colorado) area outcrop. At delineation time, only a few wells and some geophysical surveys are available for reservoir characterization. The geologist analyses these data, and determines some major characteristics of the deposition system as its type, its direction, etc.

This interpretation is then quantified so as to be used as the input of a geostatistical simulation model, in terms of lithofacies proportion curves, and variogram function parameters. This quantification is not unique, and the geologist provides ranges for each parameter.

The geostatistical simulator gives several images, with different parameters varying in the selected ranges. A first investigation among these images is performed by looking at the volume of reservoir connected to the producing or injecting wells, for various wells spacing.

Then, these images are translated into petrophysical description, allowing to perform oil recovery calculations, for the selected images. Finally, an estimation of the oil production for different development scenarios, taking into account uncertainties is performed.

This methodology is possible thanks to a geostatistical simulation model enabling integration of geology and reservoir engineering.

The geostatistical simulation model is a tool for translating geological knowledge into parameters manageable for reservoir engineers. The proposed methodology allows to make better decisions in the delineation phase, as impact of uncertainty can be more easily computed.

The availability of an integrated model, avoiding painful data handling (petrophysical data attribution, upscaling), is an important point.
A Numerical-Dispersion-Free Method for Modeling the Gas Cycling Process
Authors: Chang E. Y. , Lo T. S.
Published: December 2007

This paper describes an effective methodology for accurate evaluation of liquid recovery during the gas cycling of condensate reservoirs. First, the fluid flow problem is solved by potential flow, which is shown to be applicable to compressible gas flows also. The mass transfer and phase behavior within the potential flow streamtubes can then be calculated using one dimensional reservoir simulators, which can efficiently control the numerical dispersion errors to any desired level. An example illustrates this method’s efficiency and accuracy advantages over conventional finite difference methods.
Analysis of the Waterflood Response of a Naturally Fractured Reservoir
Authors: Beliveau D. , Payne D. A. , Mundry M.
Published: December 2007

The 500 million barrel Midale oilfield is part of a trend of large Mississippian oil accumulations located in southeastern Saskatchewan, along the northern margin of the Williston Basin. The field was discovered in 1953 and developed on 80-acre spacing. In 1962 Midale was unitized for waterflooding, with 83 320-acre inverted ninespot patterns (Figure 1).

Waterflood performance in Midale is dominated by a system of oriented natural vertical fractures typically spaced 1–4 feet apart. Production wells located "ontrend" from injectors (aligned with the fractures) showed sharp early response to waterflood. In contrast, response of "offtrend" producers was smooth and delayed. Oil produced to-date represents recovery of 20% of the original oil in place (OOLP); ultimate waterflood recovery is predicted to be only 24% OOLP. Current watercut in the mature operation is about 80% (Figure 2). Even with the natural fractures, the Midale Unit is a low-productivity reservoir, with average production rates of 75–100 STB/D/well.

A major reservoir and process mechanism characterization effort began in the mid-1980s to guide ongoing Midale field development opportunities. A detailed study team consisting of a geologist, a petrophysicist, and production, reservoir, and research engineers spent three years analyzing waterflood performance. The large-scale effort was dictated by the complexity of predicting performance in a heavily fractured reservoir. Obviously, good communication and cross-discipline integration of expertise was a key to the project’s success. The resulting reservoir and process model honors all available data and can match performance of the field-scale waterflood as well as a tertiary CO2 flood pilot.
Floating Production Storage and Offloading: Disconnectable or Not?
Authors: d’Hautefeuille B. B.
Published: December 2007

Single Point Mooring Systems are commonly used to moor Floating Production tankers or barges at exposed offshore locations. The first mooring systems were designed for permanent applications. In the last five years, disconnectable systems have been developed mainly for South East Asia.

These disconnectable systems have been designed around the turret mooring concept, due to their mechanical simplicity and cost attractiveness.

The turret systems have been developed for a wide range of criteria such as environmental conditions, water depth and operating constraints.

After a brief review of different turret mooring systems, this paper discusses the concept of disconnectability. Some mooring systems have been designed to be disconnected in an event where the design weather conditions are reached or in case of typhoon or cyclone warnings.

A comparison of disconnectable versus permanent mooring systems is presented with regards to mooring feasibility, safety of personnel, equipment availability, operating philosophy, downtime, investment cost as well as operating costs.
The Uses of Buoyancy in Completing High-Drag Horizontal Wellbores
Authors: Hood J. L. , Mueller M. D. , Mims M. G.
Published: December 2007

Unocal has been actively developing horizontal well drilling and completion technology. This technology has been used to drill and complete wells with horizontal displacement to true vertical depth ratios (HD/TVD) of up to 2.92. This technology has also has been used to drill and install casing in the world's two longest horizontal wells, each containing approximately 1.1 miles of producing formation. This paper presents the techniques used to analyze torque and drag forces, and the buoyancy assistance technology used to overcome those forces.
Dewatering Technology A Current Overview and SE Asia Applications
Authors: Tapin T. P. , Blake L. D.
Published: December 2007

This paper discusses the operational aspects and advantages of dewatering drilling fluids at the rigsite. It covers the use of dewatering for waste control and minimization, as a recycling process for water conservation, and for total solids control. Detailed descriptions of the process and the parameters involved in setting-up and operating dewatering units are presented. A general description of the flocculation process using chemical flocculants and coagulants are also discussed.
Production and Pressure Decline Curves for Wet Gas Sands With Closed Outer Boundaries
Authors: Mohaghegh S. , Ertekin T.
Published: December 2007

A family of pressure and production decline curves are generated for wet-gas sands with closed outer boundaries. Wet-gas sands are characterized as gas reservoirs which produce substantial amounts of water together with gas. Production of water introduces complications when practicing engineers use decline curves designed for gas reservoirs in which gas is the only flowing phase. This usually translates to over estimation of the production performance of the reservoir.

In this paper a series of pressure and production decline curves which accounts for the water production in wet-gas sands is presented. These decline curves provide a simple way of extracting valuable information from available data, using graphical methods and simple calculations. The proposed decline curves are generated for a radial system with closed outer boundary with one centrally located well which fully penetrates the formation. The application of the proposed decline curves is illustrated through a series of examples.

In the case of constant pressure inner boundary, production decline curves are generated for different ratios of sandface pressure and initial formation pressure, and in the case of constant flow rate inner boundary, pressure decline curves are generated for different initial formation pressures. The proposed decline curves covers a broad spectrum of reservoir extents and have proven to be unique for a wide range of fluid and formation parameters.
Pre- and Post-Stimulation Well Test Data Analysis from Horizontal Wells in the Devonian Shale
Authors: Salamy S. P. , Aminian K. , Koperna G. J. , Locke C. D.
Published: December 2007

Recent drilling and completion operations have demonstrated the technical and economical successes of horizontal wells over that of vertical wells. The need for horizontal wells was established as a vital production enhancement technique for wells producing from economically marginal, low permeable gas formations in the Appalachian Basin exhibiting strong permeability anisotropy.

As part of a U.S. Department of Energy (U.S.DOE) funded research project, several horizontal wells were drilled and completed to the Devonian Shale strata in the Appalachian Basin. Production from these wells exhibited high improvement ratios to that from vertical wells; however, to enhance the economics of the horizontal wells, stimulation was indicated. The success of the stimulation techniques and the measure of improvements were determined from production results and/or pressure analyses.

This paper exhibits and summarizes the results of production and pressure buildup data analyses for the different horizontal wells. Based on pre- and poststimulation production and pressure data, various well test analysis techniques such as type curves for horizontal gas wells, reservoir simulation, Horner's method, and other applicable techniques are utilized.

Finally, the correlation of production and pressure analysis results helped in the assessment and evaluation of the stimulation techniques.
Mathematical and Experimental Simulation of Hydraulic Fracturing in Shallow Coal Seams
Authors: Abass H. , Hedayati S. , Kim C. M.
Published: December 2007

Laboratory hydraulic fracturing experiments on unconfined coal blocks were conducted to simulate fracture stimulation of shallow coal seams. Fractures were initiated by injecting a gelled water into an openhole section of a wellbore. Multiple fractures appeared at the sample periphery during injection period. This paper describes observations made during laboratory experiments, and discusses implications of the experimental results to field-scale treatments. The results have application in modifying fracture width calculations for shallow coal seams. When a shallow coal seam is hydraulically fractured, the created fracture width may be developed as a result of inflating some cleats and closure of surrounding cleats. Stress-strain curves for coal samples under uniaxial compression showed nonlinear, stress-dependent Young's modulus. The traditional approach for the fracture width calculation based on a constant Young's modulus is not valid in shallow coal seam fracturing. Therefore, an approach that accounts for nonlinear compaction using stress-dependent modulus in calculating fracture width is described.
Design and Evaluation of Stimulation and Workover Treatments in Coal Seam Reservoirs
Authors: Nimerick K. H. , Hinkel J. J. , England K. W. , Norton J. L. , Roy M.
Published: December 2007

This paper presents the results of field trials conducted primarily to evaluate the efficacy of a new additive developed specifically for use in fracturing coal seams and shale wells. The case histories were carefully chosen so that the effects related to use of the new material could be isolated as well as possible. The data show that substantial production improvements may be achieved. This paper also presents results from laboratory tests which show that the new additive may also be useful in workover treatments.
Field Use of the Compiled Spreadsheet Analysis (CSA): Log Analysis for the Laptop
Authors: Walbe K. A. , Collart D.
Published: December 2007

With the introduction of reasonably-priced 386-based, co-processed, multi-meg. hard drive laptops occuring at the same time ASCII formatted log data became available in the field from logging companies, the ability of the company geologist or engineer to quickly analyze this data themselves, while in the field, became possible.

Basically the CSA program takes a spreadsheet with all pertinent formulas, macros, settings (print, database and communications) and compiles these templates into runtime applications. The advantages of this system are in both the mechanical aspect (where the compiled program will run many times faster than the original; will utilize co-processor and expanded memory support; and will support virtual memory by using the system hard drive as temporary storage when all available RAM has been exhausted), and the programming aspect (where all formulae, macros and settings can be easily tailored to customer criteria and then become secure and unmodifiable).

Once the templates have been compiled into a CSA runtime application, they may be legally run without the need of the original spreadsheet software or the resulting royalties.
New System for Advanced Well Test Analysis
Authors: Da Prat G. , Pacheco E. , Sierra L.
Published: December 2007

In this work the fundamentals and theoretical principles are presented that describe a system used for both pressure data acquisition and analysis. The advantages of using equivalent time and pseudo equipment time in the plotting functions used for pressure transient analysis is explained. For pressure data analysis, the system automatically optimizes the reservoir parameters, resulting in a theoretical profile that matches the measured data with minimum standard deviation within the noise band of the measured data. Regarding calculation of reservoir parameters, the system calculates the value of the parameter by non linear regression using the entire test profile. The reservoir models included in the system are described and several field applications are presented. A main result derived from this work is that we can conduct an accurate test faster and reduce rig time using advanced plotting functions and regression techniques. Complex systems like layered reservoirs and horizontal wells can be handled by the system.
Solids Control and Low-Solids: Important Binary to Drill Deep Wells
Authors: Machado J. C. , Castilho P. F
Published: December 2007

This study describes experiments and techniques relative to the control of solids and fluids used for deep well drilling, in the Marajó Basin, in the Amazon area, in Brazil, where the well bottom temperatures reach around 148,9°C(300°F).

The solids removal system associated to a low solids fluid, non disperse, without densifier, basically composed of bentonite/polyacrylamide/potash have been considered as important factors for drilling with density inferior to 1080Kg/m3 (9.O lb/gal), during all phases of the drilling process.
Water Invasion in the Morichal-01 Reservoir, Jobo Field, Monagas State, Venezuela
Authors: Chedid R.
Published: December 2007

The invasion of water in the reservoir Morichal-01, Campo Jobo in Monagas State Venezuela (Fig.1) has affected the production of oil and therefore has dropped the volume of remanent reserves in the area. The water front has advanced 37 feet into the reservoir but the water incursion has reached up to 170 feet. Considering the effective permeability and the dipping of strata, it is stated then the probable way of water for invasion. Of the seven sand bodies (A, B, C, D, E, F, G) that form the reservoir, three of the lower part (E, F, G) are mostly affected, the upper four are not.

Fig 1 Jobo Field Location Map
Light Oil Steamflooding: A Laboratory Study of Oil Recovery from Oil-Wet and Water-Wet Porous Media from a 2-D Physical Model
Authors: Olsen D. K. , Sarathi P. S. , Mahmood S. M. , Ramzel E. B. , Roark S. D.
Published: December 2007

Laboratory experiments were conducted in a two-dimensional (2-D) physical model to determine the effect of wettability on the light oil recovery by steam from previously waterflooded porous media of different wettabilities. The results show that light-oil steamfloods from oil-wet porous media (silylated sand) start at a higher waterflood residual oil saturation, respond faster to steam, and flood to the same residual oil saturation as water-wet porous media. Oil-wet reservoirs typically are poor waterflood candidates and produce at stripper well status but have a high waterflood residual oil saturation. These results indicate that light-oil steamflooding of oil-wet reservoirs can recover significant quantities of oil, whereas waterflooding oil-wet reservoirs can leave most of the oil in place.

Oil recoveries from steamfloods using oil and core material from two light-oil steamflooding pilot projects were compared with laboratory-prepared, oil-wet and water-wet sandpacks. These field cores of intermediate wettability show behavior between that of oil-wet silylated sand and strongly water-wet sand. Steamflooding changes the wettability of oil-wet porous media to a more water-wet state. A direct correlation exists between steam temperature, steam volume, and the degree of alteration of rock surface to a more water-wet condition.
Primary Results Of A Geological And Geophysical Reconnaissance Of The Jizan Coastal Plain In Saudi Arabia
Authors: Gillman Michel
Published: December 2007

Gillman, Michel (Auxerap Jeddah)

Geological and above all geophysical surveys, followed by the deep well of Mansiyah, have permitted a better knowledge of the structure of the coastal plain of Jizan stretching along the foot of the Asir high granitic or metamorphic mountains in the south western part of Saudi Arabia. This elongated plain belongs to the eastern edge of the Red Sea wide graben formed by tension and limited with a faulty, volcanic zone. It is only in the eastern limit of the Jizan Plan that the Secondary and Tertiary sedimentary series outcrop; that is to say, the Khums sandstone and the Hanifa limestone from the ante-Jurassic to Upper Jurassic time which were deposited on the southern margin of the Arabo-Nubian shield and were covered with the Upper Tertiary Baid formation in angular disconformity.

The Baid formation corresponds to the marginal deposits of the Red Sea graben, basinwards the Mansiyah well No. 1 penetrated a thick continental series, then a massive salt penetrated a thick continental series, then a massive salt sequence and finally marine clastic deposits.
Further Studies of the Relation of Physical Properties of Rock to Rock Drillability
Authors: Somerton W.H. , Esfandiari F. , Singhal A.
Published: December 2007

In the present study, the work of Gstalder and Raynal on the correlation of physical properties of rocks with drilling performance properties of rocks with drilling performance has been extended and some new methods of measuring rock drillability have been proposed. Their conclusions that sonic velocity is a good indicator of rock drillability have been substantiated, provided a mineralogical factor is taken into account.

Rock drillability [ ], defined in the present work as the volume of rock drilled per present work as the volume of rock drilled per unit of energy input, has the same dimensions as Gstalder and Raynal's "Effritement Specifique" as obtained from a Schreiner hardness test. A good correlation is obtained between these two quantities but it is apparent that 6 to 34 times as much rock breakage occurs by penetration tests as by air drilling tests for the same expenditure of energy. The value of drillability [ ] varies with bit type and may be a good indicator of the most efficient bit type for a given rock.

Drilling strength., as defined earlier by Somerton, and drillability [ ] both correlate well with sonic velocity but both require a mineralogical factor. However, drilling strength shows a linear relation to triaxial strength, which is only slightly dependent on mineralogical character.

Triaxial elastic moduli values correlate well with rock drilling parameters. This is to be expected since the relations between elastic moduli and sonic velocity are well known. In fact the evidence all seems to indicate that a function of sonic velocity could be introduced into rock drilling equations to account for the rock strength term.

Introduction

Drilling Strength

In drilling performance equations one quantity that has been found difficult to evaluate is the resistance of the rock to drilling. Whether it be "drilling strength" as defined by Somerton, a variable strength exponent as used by Galle and Woods, or an intercept value on a drilling rate-bit weight plot as proposed by Bingham, this quantity plot as proposed by Bingham, this quantity cannot be evaluated by a single simple test.

Simon has proposed that drilling strength be defined by an impact loading test as the ratio of energy input to volume of rock broken.
New Methods for the Analysis of Closed-Chamber Tests
Authors: Xiao Jinjiang , Reynolds A. C.
Published: December 2007

A closed chamber test (CCT) is characterized by a variable wellbore storage coefficient, whereas, in a slug test, the wellbore storage coefficient is assumed to be constant. It is shown that for ranges of parameters often encountered in practical cases, a large span of the CCT pressure data can be converted to equivalent slug test pressure data which can then be analyzed by several available slug test analysis techniques. In addition, we derive a new convolution method for analyzing buildup data obtained in a closed chamber drillstem test. We also present a method to analyze slug test data influenced by a step change in the wellbore storage coefficient due to a change in the well-string diameter.
The Effect of Oil Composition and Asphaltene Content on CO2 Displacement
Authors: Huang E. T. S.
Published: December 2007

A west Texas crude oil containing 5% asphaltenes had a slim tube MMP measured to be 2150 psig at 120°F. When a CO2 coreflood test was performed for this oil at 2500 psig under a tertiary mode, only about half of the waterflooded residual oil was recovered, which implied the displacement process to be immiscible. A series of tertiary CO2 coreflood tests have been conducted at 120°F and 2500 psig to attempt to understand this anomaly. These displacement tests were conducted using 4 foot Berea cores and two west Texas crude oils having different asphaltene contents. The results indicate that oil recovery efficiency decreases if the C5 to C19 fraction in the oil decreases- or the asphaltene content increases.

For the oil containing more than 5% asphaltenes, using the slim tube MMP as a criterion for evaluating a tertiary miscible CO2 flood process could be misleading. An alternate displacement evaluation method is suggested. The guidelines to determine the process applicability are (1) a strong oil bank followed by a plateau on the oil recovery curve, and (2) little change in the produced oil compositions during the first two thirds of the oil production period.
Qualifications of an Enhanced Oil Recovery Project Pursuant to the Texas Railroad Commission's Statewide Rule 50
Authors: Richter T. H.
Published: December 2007

Enhanced Oil Recovery (EOR) projects are an expanding technology. In an effort to provide an incentive to industry to create more EOR projects, the Railroad Commission recommended and endorsed new legislation, which would grant severance tax incentives to Railroad Commission approved EOR projects. The Legislature recognized the benefit EOR projects could be to the State of Texas and enacted amendments to the Texas Tax Code § 202.052 and added new section 202.054. This legislation gave the Railroad Commission the authority to implement Statewide Rule 50.

Statewide Rule 50, as originally adopted on September 1, 1989, provided a severance tax incentive to all oil produced from EOR projects which qualified as "new and distinct" and met the other requirements of the rule.

Statewide Rule 50 provides for a state severance tax rate decrease for an approved EOR project for 10 years, unless the project is sooner terminated, beginning the first day of the month following the date the Railroad Commission certifies that a positive production response has occurred.

EOR projects which may qualify include secondary recovery applications as well as tertiary recovery programs which includes alkaline flooding, carbon dioxide, cyclic steam, miscible and immiscible displacement processes, in-situ combustion, microemulsion, polymer augmented and steam drive projects.

It is necessary that industry understands the intent of the rule which governs those projects which qualify versus those projects which the Commission has determined do not qualify. Since September 1, 1989, several cases which were not administratively approved have been considered and acted upon by the Commission.

In the recent Legislative session, the Railroad Commission recommended amendments to Tax Code section 202.054 to specifically provide for expansions of existing EOR projects. The legislature amended the Tax Code effective September 1, 1991. On September 1, 1991, the Railroad Commission adopted emergency amendments to Statewide Rule 50 to implement these provisions.

Project expansions which previously did not qualify as "new and distinct" under the- original Rule 50 may qualify under the amendments and receive a severance tax exemption as to the incremental oil produced by the project.

This paper will assist industry in deciding under which section of the rule that their proposed EOR project may qualify.
Two- and Three-Phase Relative Permeability Studies at High-Capillary Numbers
Authors: Foulser R. W. S. , Goodyear S. G. , Sims R. J.
Published: December 2007

In surfactant flooding the form of the relative permeabilities at high capillary numbers has a crucial role in determining the transport of equilibrium phases through the reservoir. A conventional assumption is that a system which produces ultra-low interfacial tensions is close to miscibility, making the use of straight line relative permeabilities appropriate. In gas/oil systems this assumption may be justified, however, in surfactant systems it is unclear that the ultra-low interfacial tensions are associated in the same way with miscibility. There is little conclusive data in the literature to clarify this. This paper describes experimental work undertaken to complement the development of an alternative three phase relative permeability model for surfactant flooding based on the concept of droplet flow.

Two and three phase relative permeabilities have been determined for equilibrium phases from an optimal surfactant system. All relative permeabilities have been measured under steady state conditions and the pressure drop held constant to ensure that the relative permeabilities are determined at a constant capillary number, as defined within chemical flooding simulators. Initial measurements suggested that the relative permeabilities were linear functions of saturation. However, a careful investigation showed that these results arose from gravity segregation in the core endcaps. This was overcome using an improved endcap design and the relative permeabilities were then found to be a nonlinear function of saturation. In particular the micellar phase relative permeabilities were concave functions of saturation, in agreement with our model.
NMR Imaging for Water/Oil Displacement in Cores Under Viscous-Capillary Force Control
Authors: Enwere M. P. , Archer J. S.
Published: December 2007

One-dimensional saturation distribution (saturation profile) and subsequently the saturation gradients in core floods were obtained directly from measurements using nuclear magnetic resonance (NMR) imaging. The core floods (water displacing oil in a water-wet Portland limestone core plug) were conducted at a very low flood rate, hence the saturation profile was influenced by the contribution of both viscous and capillary forces. The imbibition capillary pressure curve for the limestone rock was available and was used in conjunction with the measured saturation profile to quantify the capillary pressure gradients. This paper reports a successful approach to conducting and interpreting laboratory displacement tests at viscous-capillary force ratios typical of oil reservoirs.

This test demonstrated the NMR imaging technique as a useful complementary tool for laboratory study of water -oil displacement in cores. The practical contribution of this work is that it demonstrates the possibility of analysing laboratory core flood tests which yield information on both viscous and capillary forces, and hence the potential for scaling-up relative permeability data from laboratory tests to simulator-scale grid blocks using displacement force ratios.
Numerical Evaluation of CO2 Effects in Thermal Oil Recovery Processes
Authors: Latil M. J. , Le Thiez P. A.
Published: December 2007

Up-to-date relations for oil/water-CO2 thermodynamics have been implemented in SARIP 1, the IFP compositionnal thermal simulator.

Several field and laboratory cases of steam-CO2 injection and of in-situ combustion axe presented and discussed. In thermal processes, gaseous and oil-dissolved CO2 may improve the final oil recovery in thermal processes by only a few percent but significantly accelerate the oil recovery rate. CO2 dissolution in water, which is slightly detrimental, needs only to be taken into account at high water saturations.
Performance of an Up-Dip Injection Strategy in a Steeply Dipping Steamdrive
Authors: Zmick D. R. , Dennis E. L.
Published: December 2007

The purpose of this paper is to describe the evolution of a successful steamflood, and to discuss various operational parameters that have been recorded over time. Also described are the techniques that were employed to maintain the project's profitability as the flood became more mature and less efficient.

Section 2F (T.11N./R.24W.) is located in the southern end of the Midway Sunset Oil Field, near Maricopa, California. The reservoir is composed of 5 primary sand bodies (referred to as the A-E sands) delineated by interbedded, impermeable shales. A unique characteristic of this reservoir is that it dips at 53 degrees on average. The 14 degree API (.97 g/cm3)oil production has been accelerated in 3 of the 5 sands through thermally assisted gravity drainage.

In 2 of the 3- original target (E and D) sands, we are phasing out continuous updip injection due primarily to economics and project maturity. A number of operational parameters have been recorded from the project start up until the present. See table 1. For these 2 sands, the project has performed nearly as predicted in the- original scoping. The flood in the third (C) sand has been in operation for less than 1 year, and it therefore has little information available to report.
A Mathematical Model for Microbially Enhanced Oil Recovery Process
Authors: Zhang Xu , Knapp R. M. , Mclnerney M. J.
Published: December 2007

A three-phase, multiple-species, one-dimension model has been developed to simulate bacterial transport, growth, and metabolism processes involved in microbially enhanced oil recovery (MEOR) and to predict permeability modification that results from these microbial activities in porous media. Convection-dispersion equations and microbial kinetics are incorporated in the model system to characterize and quantify biomass production, product formation, and nutrient utilization in the MEOR process. Permeability modification is assumed to be due to both pore-surface retention and pore-throat plugging by bacterial cells.

The model has been applied to static (sand packs) and core-flooding (sandstone cores) experiments to describe microbial movement, metabolite production, and nutrient consumption during growth and metabolism and to estimate permeability reduction. Comparison between numerical solutions and experimental results indicated that the model does simulate the essential microbial kinetics of laboratory experiments and can be extended to provide numerical predictions for the purposes of design and evaluation of MEOR field projects.
Competitive Bidding Tactics for New Exploration Concessions
Authors: Hawley P. W. , Bramley A. D. , Castellani J-M.
Published: December 2007

In some (mostly developing) countries, oil companies compete for new exploration agreements by bidding the key economic parameters. Companies are faced with a trade off between profitability of potential discoveries and probability of winning the bid.

We believe that an increasing number of companies are making generous offers in order to win bids, in the expectation of being able to renegotiate economic terms if they make a discovery. This tactic is hard to recognise and may have a good chance of success, due to the strength of the oil company's bargaining position upon discovery. However, the tactic damages the performance of the E&P industry in developing countries - for governments and companies alike.

The means of combating "tactical underbidding" rest largely with governments and national oil companies in making better contracts and taking a cautious approach to the evaluation of bids. Reputable companies can contribute to the process by emphasising that their bids are formulated in good faith and based on sound commercial considerations.