bluuebunny/crossref_metadata_2025 huggingface dataset:
Downward Two-Phase Flow Effects in Heat-Loss and Pressure-Drop Modeling of Steam Injection Wells
Authors: Galate J. W. , Mitchell R. F.
Published: December 2007

Modelling of the pressure drop and heat loss in steam injection wells has undergone a gradual evolution since the heavy interest in enhanced oil recovery by steam injection in the mid-60's. After briefly reviewing the evolution of steam models this paper presents a model which advances the state-of-the-art of steam modelling.

The main advance presented in this paper is modelling the effects of the various flow regimes that occur during steam injection. The paper describes the formulation of a two-phase downward vertical flow pressure drop model which is not limited by the "no-slip" homogeneous flow assumptions in most previously published models. By using different correlations for mist, bubble, and slug flow, improved pressure drop calculations result, which in turn improve temperature predictions. The paper describes how the model handles temperature predictions differently in the single and two-phase steam flow situations.

The paper also describes special features in the model to account for layered soil properties, soil dry out, cyclic injection, coupling heat losses, and reflux boiling in wet annuli. Two examples problems are presented which illustrate some of these features.
Pilot Gas-Lift System at Prudhoe Bay
Authors: Hanson E. S.
Published: December 2007

This paper discusses the design concepts and operating experiences of a small, twelve-well gas lift system in a unique arctic environment. The project was undertaken by Sohio Alaska Petroleum Company as operator for the Western Operating Area of the Prudhoe Bay Unit. This pilot system provided valuable operating data prior to the startup of the full field gas lift system which, in its final configuration, will be the largest gas lift facility in the United States.

This paper illustrates the intimate interaction of all of the variables that can affect gas lift such as supply pressure, separator pressure, tubing hydraulics, flowline hydraulics, geothermal temperature gradient, and gas lift valve characteristics. It also addresses some of the concerns that are unique to the operation of gas lift systems in an arctic environment.
One-Trip Perforate and Gravel Pack System
Authors: Hailey T. T. , Donovan J. F. , Van Sickle E. W.
Published: December 2007

A downhole tool system has been developed that makes it possible to perforate well casing with all the advantages of a TCP (Tubing Conveyed Perforating) gun and to gravel pack that well using proven techniques, all on the same trip in the hole. The system has been operated successfully in 7-5/8″, 7″ and 5″ casing, and is also available for 5-1/2″ and 9-5/8″ casing. The system has been in development for about 2 years in the Texas and Louisiana Gulf Coast area, in cooperation with several different operators and under varying well conditions.

The main components of the system are a casing sized TCP gun, a hookwall packer which is multiple acting and operated by reciprocation of the workstring only, screen and blank pipe common to gravel packed completions, and a hydraulically set seal bore packer.

The operation of the system is as follows:

–– As the system is run in the hole, a radioactive tag is installed in the workstring at a known distance from the TCP gun. With the gun at approximate perforating depth based on pipe measurements, a gamma ray logging tool is used to locate the tag and correlate its position back to previous logs. Knowing the exact location of the tag, the gun is re-positioned precisely for perforating. –– The hookwall packer, just above the gun in the assembly, is set and tested, then a bypass is opened allowing circulation through the packer. Lightweight fluid is then circulated down the workstring and the packer bypass is closed, creating an underbalanced pressure in the wellbore compared to reservoir pressure. –– The gun is then detonated by dropping a detonating bar or pressuring the workstring-casing annulus, depending on whether a mechanical or hydraulic firing head is used. The well can be flowed as necessary for clean up and testing. –– The well is killed by unsetting the hookwall packer and reverse circulating kill weight fluid into the workstring. –– The entire assembly is moved downhole and the hookwall packer is reset below the just-perforated interval. The seal bore packer is then hydraulically set by dropping a ball into the workstring and pressuring against the ball. This setting operation also converts a tool inside the packer to a dual flow path crossover tool, crossing over tubing flow above the seal bore packer to annular flow below it. –– After rotating the crossover tool free from the seal bore packer, upward movement of the crossover tool unseals a concentric string (washpipe) inside the screen from the hookwall packer. Fluid treatments such as acids, clay stabilizers, and the gravel slurry itself can then be circulated down and circulated through the screen or squeezed into formation similar to common industry practices. –– After the gravel pack is complete, the crossover tool and concentric string are removed, and a seal assembly is run inside the seal bore packer for production.

The chief limitation of the system is the amount of rathole available in the well. The area below the producing zone must be long enough to accept the spent TCP gun assembly.
Resin-Coated Sand Slurries for Repair of Damaged Liners
Authors: Murphey J. R. , Roll D. L. , Wong L.
Published: December 2007

Resin-coated sand can be used to repair damaged slotted liner gravel packs without removing the liner from the well. Either concentric or coiled tubing can be used to perform the treatment, using a small workover rig. The well can be returned to production typically in 24 hours.

This repair technique has been used with success in the Gulf Coast and West Coast areas. Economy of the treatment makes it viable for wells that are too marginal to justify complete liner workovers.

This paper describes the features and the application of the system and reports field results of 12 jobs performed over intervals up to 300 ft.
Studies of the Steamdrive Process in Inclined Reservoirs
Authors: Doscher T. M. , Marinello S.
Published: December 2007

Scaled physical model studies of the steam drive process in dipping reservoirs containing very viscous crudes, tars and bitumens, have shown that economic oil steam ratios can be achieved by judicious management whereas such economic ratios cannot be achieved in horizontal reservoirs where the opportunity for gravity drainage is much reduced.
Modeling Fracture Permeability Around a Well During Depletion
Authors: Bakhtar K. , Barton N. R. , Rakop K. , Jones A. H.
Published: December 2007

The normal closure behavior of fractures around a well during various stages of depletion has a major influence on the changes in fracture permeability and subsequent well production. Methods are described for providing a practical approach for obtaining fracture parameters to model these permeability changes. The parameters of interest include: i) the fracture roughness coefficient (JRCo), ii) the wall strength (JCSo), which can both be obtained from simple tests on cores, and iii) the overburden and horizontal stresses around the fracture. The transformation equations would then be applied to estimate the effective normal stress on the fracture plane. The model relates the fracture aperture to the effective normal stress and subsequently computes the resulting permeability for changes in pore pressure.
Geology and Hydrocarbon Occurrence of the Khuff Formation in Abu Dhabi, U.A.E.
Authors: El Bishlawy S. H.
Published: December 2007

The Khuff Formation in Abu Dhabi consists mainly of a thick shallow marine sequence of limestone, dolomite and subordinate anhydrite of Late Permian to Early Triassic age. The formation average thickness is about 2800 ft. and shows remarkable lateral consistency in lithology and log response that allow its correlation and sub-division into four major lithostratigraphic units, each of which is characterised by a specific lithofacies or lithofacies association. The formation depth of burial ranges between 11800 ft. and 19800 ft. subsea.

The Khuff Formation is generally characterised by poor porosity and low matrix permeability. The porosity types are of primary and secondary origins and are controlled by original depositional facies, depth of burial and diagenesis. Fractures are common in the section and have a significant impact on enhancing the effective porosity and permeability.

Production from the Khuff Formation is mainly gas and condensate with a maximum condensate ratio of 10 BBL/MMSCF. The main gas component is methane which forms more than 75% of the total Khuff gas composition, however appreciable amounts of hydrogen sulphide, nitrogen and carbon dioxide were also recorded in some of the wells.

The source of the hydrocarbon gas in the Khuff Formation is not yet well defined; however two sources are postulated: the first is a pre-Khuff source which is probably the Silurian Shales and the second is an indigenous one.
On-Line Inspection of Offshore Pipelines
Authors: Shannon R. W. E. , Fitzgerald E. M. N. , Jackson L.
Published: December 2007

Pipeline networks worldwide, which can be measured Pipeline networks worldwide, which can be measured in hundreds of thousands of kilometres, represent major capital assets with enormous revenue-earning capacity and as such often figure significantly in a country's economy. Of particular economic and strategic importance are under sea pipelines which provide the critical link between production provide the critical link between production platform and shore terminal sometimes over long platform and shore terminal sometimes over long distances. Such lines often take supplies from a number of sources via gathering lines and this makes their long term value, as old fields are depleted and new ones discovered, extremely high. In general these lines have been operated for many years during which time the pipeline industry generally has experienced changes in design, construction and maintenance methods some of which reflect the fact that high pressure pipelines are subject to deterioration to some degree or other. The rate at which this occurs depends on numerous factors not least being the chemical composition of the product carried, which may determine any internal corrosive action, and the degree to which an external protective coating and cathodic protection can be proof against the environment protection can be proof against the environment including third party interference. Such factors combined with the relative inaccessibility of submarine pipelines means that cost effective maintenance methods are an important factor in their operation. More particularly such methods must be capable at any time of quantitatively describing the structural integrity of the pipeline. This can be achieved only by pressure pipeline. This can be achieved only by pressure testing or some form of non-destructive evaluation.

Pressure testing will continue to be essential to Pressure testing will continue to be essential to the pipeline industry as an effective means of commissioning new and modified installations. Its value lies in the fact that it will reveal, sometimes in a spectacular manner, all defects that are significant at the particular test level.

It is not however a very cheap or convenient method of subsequent periodic testing being somewhat disruptive in terms of product supply unless additional pipeline capacity and/or storage can be used to maintain supply for the duration of the test. Clearly such an approach represents a significant capital investment especially in the case of main off-shore supply lines and is unlikely to be economically justified. Neither is it a straightforward test, requiring strict attention to time-consuming stages of filling with water, testing and drying out. In addition the location and repair of small leaks occurring during test is difficult.
New Cathodic Protection System Design for Dubai Platforms
Authors: Evans S.
Published: December 2007

New sacrificial anode protection criteria that were developed and tested by the Dubai Petroleum Company (DPC) have resulted in a 40 percent decrease in anode weight as compared to that required by conventionally accepted design. Derivation of the criteria are based on an analyses of extensive field results of potential surveys of seven DPC platforms that had conventional sacrificial anode protection systems. It was found that an initial platform current density of 310±20 milliampers per square meter of area exposed to seawater, resulted in polarization of the platform to −1 volt with respect to the silversilver chloride reference electrode. As a consequence of this high initial polarization, the electric current requirement for protection is significantly reduced. The new criteria were used in the design of Platform "JJ" which was installed in September 1982. Field results that include periodic potential surveys of Platform "JJ" will be presented and discussed.
Biodeterioration of Concrete Piling in the Arabian Gulf
Authors: Jadkowski T. K. , Wiltsie E. A.
Published: December 2007

Concrete is one of the most widely used materials in marine construction because of its characteristic durability in sea environments. Recent inspection of concrete piles installed in the Arabian Gulf has revealed that concrete with high content of calcareous aggregate is susceptible to biodeterioration. Marine rock borers and sponges, which are common in areas where the seabed is composed of limestone rock, have been identified as the marine species responsible for the biodeterioration. Boring organisms pose a significant threat to concrete pile structural integrity. Boreholes deteriorate concrete and expose outer pile reinforcement to seawater.

This paper describes the causes and magnitude of biodeterioration of piles installed in the Arabian Gulf and presents design parameters and material specifications for the selected preventive repair system.
The Occurrence and Origin of Oil in Offshore Abu Dhabi
Authors: Hassan T. H. , Azer S.
Published: December 2007

Offshore Abu Dhabi, an area of some 30000 sq. kms. (11,600 sq.miles) is one of the richest oil-bearing areas in the world. The oil occurs primarily in the Upper Jurassic carbonates of the Arab Formation and in the limestones of the Lower Cretaceous Thamama Group. Minor oil accumulations occur in the Middle Cretaceous Mishrif Formation and oil and gas/condensate in the Middle Jurassic Araej Formation. Geographically, the occurrence of oil in the Arab and Thamama appears to be controlled by the Hith Formation seal, immediately overlying the Arab Formation and the featheredge of which runs N-S in the centre of the area. Thus, oil in the Arab Formation occurs only in western offshore Abu Dhabi where the Hith is present, whilst the most important Thamama oil accumulations either straddle the Hith Edge or occur to east of it. There are however, Thamama oil fields to the west of the Hith edge. Two primary source rocks have been identified: (a) The Upper Jurassic Diyab Formation consisting of argillaceous limestone occurring in source facies in western offshore Abu Dhabi and considered to have sourced both the Arab and the Thamama oils and probably also the hydrocarbons of the Araej. (b) The Middle Cretaceous Shilaif Formation which sourced the oil in the Mishrif.

Generation of the Arab oil from the Diyab commenced late in the Late Cretaceous with migration taking place from south western part of the area and directed in a northerly direction. But in the central area, oil would not have been trapped in the Arab because of absence of the Hith Formation caprock but in the Thamama Group. It is likely that there was another source for the Thamama oil located to the east of offshore Abu Dhabi.

Although over much of Abu Dhabi, the Shilaif forms a good source rock, it is generally immature and the source of oil in Umm Addalkh and nearby areas was derived from the more deeply buried Shilaif in offshore Dubai.
Notes on the Uwainat Oil Rim Development, Maydan Mahzam and Bul Hanine Fields, Offshore Qatar
Authors: Hamam K. A.
Published: December 2007

As a result of reservoir simulation studies of the Uwainat reservoirs (Maydan Mahzam and Bul Hanine Fields), drilling to the Uwainat oil rim target became very "tight" with a very limited vertical tolerance. To achieve drilling to the tight target requires a precise position of the well at the top of the Lower Arab IV reservoir (a reliable marker) and an accurate isochore of the Lower Arab IV – Uwainat.

The discussion shows that the level of accuracy needed in determining both the actual subsea well position and in constructing the depth contours of the reservoirs is extremely high.
Determination of Residual Oil Saturation With the Borehole Gravity Meter
Authors: Maute R. E. , Gournay L. S.
Published: December 2007

Use of the borehole gravity meter (BHGM) to measure remaining oil saturation is a method new to the industry. The technique is described, and its applicability to Middle East reservoirs is discussed. Results of an extensive error analysis are presented.

The method, which we call log-produce-log, consists of running a base BHGM before significant production, and a later BHGM after production. The remaining oil saturation is computed from the difference of the two BHGM measured bulk densities.

The Middle East oil fields are ideal for application of this method. Porosities are high, crude is light, and connate water is dense (saline). The method is independent, for all practical purposes, of hole size, rugosity, number of casing strings, shale content, and acidization. The method also has a very large radius of investigation, 50 feet plus, which enables it to sense a far larger volume of the reservoir than any other method. As reservoirs are often heterogeneous in both porosity and fluid saturations, the remaining oil saturation thus determined would be more representative of the reservoir as a whole than any other technique.

The disadvantages of the method are the need for a base BHGM log prior to significant production from the zone of interest, and a poor vertical resolution of about 10 feet.

Results of a comprehensive and realistic error analysis are presented and show this technique as possibly the most accurate Sor method.
An Experimental Study of Techniques for Increasing Oil Recovery from Oil Reservoirs with Tar Barriers
Authors: Shamaldeen S. M. , Farouq Ali S. M.
Published: December 2007

A number of major oil reservoirs in the Middle East have a tar barrier between the oil zone and the underlying water zone, with a strong bottom water drive. This investigation is aimed at oil recovery from such reservoirs. Specifically, it is intended to explore several recovery methods that could be used for increasing oil recovery from such reservoirs. As far as one can ascertain, little or no work has been published on this subject of vital importance in Saudi Arabia, Kuwait, and Iraq.

The present investigation was experimental in nature, utilizing several models, and a variety of recovery schemes. In all instances, three zones were initially set up in the models: a light oil zone on top, a water zone at the bottom, and a tar zone between the two. The thicknesses of the oil and tar zones were varied to cover a range of conditions. The bottom water zone was equipped with a water drive.

The different recovery techniques tested were: (i) injection of water into the oil zone (internal waterflood), without a bottom water drive, (ii) internal waterflood, with a bottom water drive, (iii) bottom water drive, (iv) injection of solvent into the tar zone, (v) injection of steam into (a) oil zone, (b) tar zone, and (c) water zone.

The results show that when waterflooding the oil zone, an important factor is the extent of communication between the water zone and the tar zone. Such communication can be established by use of solvents or steam, though such processes are admittedly inapplicable in some of the deeper formations. Once communication is attained, an internal waterflood can be very effective. With bottom drive alone, recovery was found to be low in view of water channelling and coning. Solvent injection runs showed that large volumes of a suitable solvent will have to be injected in order to obtain the necessary communication. Steam injection into the oil zone mitigated the benefits of a water drive. However, injection into the tar zone was effective both in promoting the bottom water drive, and also in recovering some of the tar, although this was not a primary objective. Injection into the bottom water zone was largely ineffective, since the heating of the overlying tar layer required very large volumes of steam.
Royalty Trusts: Who Benefits and Who Suffers?
Authors: Goff W. R. , Dutton G.
Published: December 2007

The merger's which have been arranged to avoid takeovers from groups whose announced intention was to spin off a royalty trust have had a greater economic impact than the trusts actually formed. The obvious and immediate beneficiaries of these mergers have been the stockholders of the merged companies who were able to sell their stock at substantially higher prices than the values perceived by the stock market. Apparently the owners of the acquiring companies also benefitted since the purchases provide clear evidence of their desire to have the assets of the merged companies rather than the price which they paid.

In those cases where the trusts were actually formed, the visible beneficiaries are the recipients of the trust shares. Since these distributions usually represent a taxable transaction, government initially benefitted directly and other taxpayers indirectly. However, after this "windfall" of tax revenue, the tax collector begins to lose tax revenues on the royalty income placed in trust since double taxation of corporate dividends on royalty income is eliminated.

Two potential sufferers deserving more sympathy than the tax collector are the employees of the companies involved and the consumer. The harm to the latter would occur if the creation of the royalty trust – or the merger – reduced exploration and development substantially. Such a reduction of funds and the resultant decrease in activities could also harm the employee as a result of personnel decreases.

This paper examines the above facets of the royalty trust issue and provides an evaluation of the causes for the formation of one such trust and the effects on the parties involved.

In addition, it describes the exploration and development activities of the company which spun off the trust before and after the spin off. The future of royalty trusts and the part they could play in further mega-mergers is also discussed.
Clean Up Your Automation
Authors: Pipal Bill
Published: December 2007

To maintain operational automated systems we as and oil field contractor are confronted with many varied problems. The installation and maintenance of these systems are varied and each individual problem could not be discussed. The basis for this paper will be derived from actual invoices of maintenance performed on automatic tank batteries, production test equipment, waterflood stations, electrified injection and production headers, computerized operations, and LACT installations. It is believed that this information along with cooperation with manufacturers and producers there will be a reduction in down time, installation cost, and maintenance costs. The tabulated data in this technical paper will give us a starting point to eliminate the problems which are the most costly. Many of these procedures are being incorporated by some of the manufacturers, but as of this time not one has utilized the latest advances of electronics to facilitate a completely smooth automated system. For the purpose of this paper allied components will consist of switches, relays, contact closures, and valve operators or solenoids not mounted within the panel or control system operator. Panel components will be those items located within the panel itself, which is usually located on the skid or mounted very close to the above system. The following data was taken from all automated systems, but they are representative in cost and percentage to any installation.
Reserves Acquisition: A New Phenomenon?
Authors: Lipari C. A. , Cailleteau L. P.
Published: December 2007

This paper reviews the growth of the public oil and gas reserves acquisition industry and the underlying economic fundamentals that create buying opportunities. It presents an analysis of the methods and techniques used in the acquisition of oil and gas properties including the identification of properties to be acquired, their sources, the selection and screening process, predicting and developing ranges of expected reserve recovery. Program "deal structure" objectives and the predominant types available and the resultant economic impact are examined. In addition, general and specific investment criteria are reviewed along with the risk factors applied to cash flow predictions. The role of financial ratios and tests such as "income to investment ratios", "payout determinations", internal rates of return, pricing sensitivity analysis and other types of financial and economic analysis in the acquisition process. The impact of price escalation on "risked" reserves for the purpose of determining a range of acceptable purchase values. Also, a review of the role of land, accounting/financial, geology, engineering and operation disciplines in property acquisition will be included in the paper.
Oil and Gas Lending Practices
Authors: Cecil R. E.
Published: December 2007

Lending to an oil and gas producer requires a fine blend of both credit and technical analyses. The primary asset, and often the only asset is oil and/or gas in the ground. A loan to the producer is dependent on the valuation of these assets. Determination of reserves is necessary, but more often than not, of greater importance is the rate of production of these reserves and the corresponding cash flow. Wells may be capable of producing at rates greater than pipeline capacity or higher than the ability of the economy to absorb the production. With the technical and economic analyses, a thorough financial review is necessary.
Concentration of Assets in Petroleum Reserve Financing
Authors: Cochran R. J.
Published: December 2007

The concentration of assets in hydrocarbon financing is critical in the determination and elimination of risk associated with this form of financing. It is the purpose of this paper to present a method to define this risk, to measure its degree of severity and to illustrate methods of diminishing this risk to the lender and the borrower.

The risk associated with concentration of assets is that the increasing loss of the major asset will result in a financially untenable situation for the lender and borrower. Therefore, it is necessary to recognize this concentration, measure its magnitude and take steps to prevent its creating a problem for the lender and the borrower.
Pattern Recognition and Tomography Using Crosswell Acoustic Data
Authors: Albright J. N. , Terry D. A. , Bradley C. R.
Published: December 2007

Measurements of the travel time of acoustic signals transmitted between wells at the Department of Energy Multi-Well Experiment site (MWX) near Rifle, Colorado, are processed and analyzed. Interpretations relevant to sand geometry and continuity have proved possible through inspection of the signal travel time plotted against the coordinates of transmitter and receiver wellbore positions, or against the depth of receiver and ray path inclination. The continuity of several sands between wells is corroborated. A major lenticular sand terminating between wells could be inferred.

To explore the possible distortions in tomographic images derived from crosswell data, synthetic tomographs are constructed from computed travel times of signals transmitted through idealized models from stratigraphy thought to be present at the MWX site. The synthetic tomographs, although preserving the general character of the model stratigraphy, are distorted enough that detailed interpretations are not possible. Horizontal distortions predominate in reconstructions of flat-lying stratigraphy.
A Model of the Hydraulic Fracturing Process for Elongated Vertical Fractures and Comparisons of Results With Other Models
Authors: Palmer I. D. , Luiskutty C. T.
Published: December 2007

A summary is given of a fracture model that calculates fracture height as a function of distance from the wellbore for the case of a continuous payzone bounded by zones in which the minimum in situ stress is higher. The model is applicable if the vertical fracture is highly elongated, with length/height ratio ≥ 3.5. The fluid flow therefore is essentially one-dimensional along the fracture length. The flow can be non-Newtonian. Leak-off is included, as well as spurt loss, but pumping rates and injected fluid properties are constant with time. Elastic properties do not vary from one zone to another. The model calculates width profiles in each vertical section of the fracture. Finally, both fracture height and bottomhole pressure are calculated as a function of time.

A comparison is made between the results of this model (ORU model) and the AMOCO, MIT, and TERRA-TEK variable-height models. There are areas of agreement and disagreement. A critical assessment is made of assumptions that differ in the models in an effort to reconcile the models. The conclusion is that the ORU, AMOCO, and TERRA-TEK models are in basic agreement for highly elongated fractures.
In-Situ Physical Properties Using Crosswell Acoustic Data
Authors: Johnson P. A. , Albright J. N.
Published: December 2007

Crosswell acoustic surveys enable the in situ measurements of elastic moduli, Poisson's ratio, porosity, and apparent seismic Q of gas-bearing low-permeability formations represented at the Department of Energy Multi-Well Experiment (MWX) site near Rifle, Colorado. These measurements, except for Q, are compared with laboratory measurements on core taken from the same depths at which the crosswell measurements are made. Seismic Q determined in situ is compared to average values for sandstone.

Porosity was determined from crosswell data using the empirical relationship between acoustic velocity, porosity, and effective pressure developed by Domenico. in situ porosities are significantly greater than the core-derived values. Sources of the discrepancy may arise from (i) the underestimation of porosity that can result when Boyle's Law measurements are made on low-permeability core and (ii) the application of Dominico's relationship, which is developed for clean sands, to the mixed sandstone and shale lithologies represented at the MWX site.

Values for Young's modulus and Poisson's ratio derived from crosswell measurements are comparable to values obtained from core. Apparent seismic Q measured in situ between wells is lower than Q measured on core and clearly shows the heterogeneity of sandstone deposited in a fluvial environment.
Impairment Mechanisms in Vicksburg Tight Gas Sands
Authors: Abrams A. , Vinegar H. J.
Published: December 2007

The flow of nitrogen and brine in tight Vicksburg "P" Sand cores was studied under field stress conditions. The experiments simulated various stages of a hydraulic fracturing treatment. Measurements were made of critical gas saturation, gas flow vs pressure gradient, and gas permeability vs brine saturation. Brine saturations were imaged with a medical Computerized Tomography (CT) scanner.

The laboratory results suggest that water block is not important when drawdown pressures at the fracture face exceed the capillary entry pressure by several hundred psi. The addition of alcohol or an alcohol/surfactant package to the brine does not significantly increase final gas flow.
Proppant Settling Velocities in Nonflowing Slurries
Authors: Kirkby L. L. , Rockefeller H. A.
Published: December 2007

This paper examines the influence of proppant concentration and fracturing fluid rheology on the settling velocity of nonflowing (static) slurries. Static sedimentation behavior is important in proppant transport not only during closure, but also during pumping since a large fraction of the proppant slurry resides in regions of low shear rate.

Slurry settling-velocity measurement technology was devised, enabling velocity determinations to be made in simulated vertical fractures at sand concentrations from 0 to 12 pounds per gallon of fluid (lb/gal). Fluids examined included crosslinked and uncrosslinked fracturing fluids, plus a Newtonian fluid. Sedimentation behavior in fracturing fluids was dominated by a particle clustering phenomenon. Settling velocity was found to depend on proppant concentration in a very different manner than generally assumed by proppant transport models. Although all fluids had similar viscosities at typical rheological characterization shear rates, static slurry settling velocities differed by a factor of more than 100. Differences in fluid viscosities at very low shear rates explain the observed diversity of settling velocities.
Chemical Utilization and Discussions of Treatment Options at Gocon's Facility
Authors: Adeniji C. A.
Published: December 2007

GOCON production operations utilize various chemicals in enhanced oil recovery projects, production of potable water and demulsification of crude oil. Decline in 1983 crude oil production was accompanied by an increase in treating cost. Alternative treating methods are discussed in this paper. Also included are tables showing crude production and chemical consumption for 1980 and 1983, flow diagrams showing proposed treating alternatives, and figures showing GOCON's location pf Production and Pipeline Facilities.
Selective Up-grading Provides Rigs for Deep Drilling
Authors: Muscovalley J.N.
Published: December 2007

The drilling contractors of the Permian Basin have been hard-pressed to meet the demand for 20,000-ft drilling rigs since the discovery of the prolific gas reservoirs in the deep Delaware Basin. The demand came at a time when the contractors of the area had felt the economic squeeze to the point that they did not have the capital to purchase new rigs for this class of work.

Now, three years later, it is obvious that the contractor has met this demand. By maximum utilization of his existing equipment, he has spent a minimum of money. This has required a careful analysis of each of the major rig components to determine what demands a 20,000-ft well will impose. New equipment has been purchased only as a last resort and most of the rigs in service today on these wells are the products of a process of selective up-grading of older rigs.

By discussing each of these rig components, this paper will show what is required, when and where the horsepower is needed, and how and why the rigs that are working today have been assembled. The contractors have proven that these rigs are adequate and capable of successfully drilling deep wells.

Introduction

In Dec., 1965, there were 23 rigs in the Delaware Basin at work on wells scheduled to drill below 20,000 ft. An investigation of these 23 rigs surprisingly would show that just one of this number is a completely new rig. The remainder, although perhaps carrying a new company number, are the results of a process of selective up-grading of used equipment by the contractor.
Through Bore Subsea Christmas Trees
Authors: Huber D S , Simmers G F C , Johnson C S
Published: December 2007

The workovers of subsea completed wells are expensive and time consuming as even the most routine tasks must be carried out by a semi-submersible. This paper describes the economic, safety and operational advantages which led to the development and successful first installation of ‘through bore’ subsea production trees.

The conventional wet subsea trees have proved to be very reliable over the past ten years of operation in the Argyll, Duncan and Innes fields, however the completion strings require pulling on the average about once every three to five years. The conventional subsea tree/tubing hanger set up design requires the tree to be tripped and a rig BOP stack run to pull the tubing. This operation is time consuming, very weather sensitive and leaves the well temporarily without a well control stack on the wellhead.

The 7 1/16″ ‘through bore’ subsea tree was developed to minimize the tubing pulling workover time and several trees have been run successfully since the latter part of 1984. The time saving on a tubing pulling workover is three days. In addition, the design considerably reduces the hazards and equipment damage risks inherent in the conventional design. Hamilton Brothers and National Supply Company in Aberdeen designed the equipment which must be considered a new generation of subsea production trees.
Some Practical Considerations For Southern North Sea Gas Testing, – An Integrated Approach
Authors: Clark D G , le Foll P , Harding A
Published: December 2007

Testing gas wells in the southern North Sea area can be a time consuming affair, often involving fracture stimulation. Since a good assessment of reservoir characteristics and long term well productivity are essential design parameters in any development plan, test analysis, including post fracture test analysis, is of great importance. BP's extensive experience over recent years in the southern North Sea area has led to the development of a practical approach to well testing, which provides great flexibility yet has proven to be very reliable.

The design philosophies and details are discussed in this paper along with the hardware which incorporates some of the latest Flopetrol developments, such as the EZ Valve™, MUST™ AND COMPUTEST™ data acquisition system. Some of the more important advantages are considered with respect to actual tests performed.
Onshore Preparation of Hutton TLP to Minimise Offshore Hook Up
Authors: Repon J G , McDonell T E
Published: December 2007

The Conoco Hutton TLP achieved first oil production twenty two days after being tethered at its North Sea location (see Figure 1) A significant contribution to this offshore hookup record was due to the onshore completion of the deck prior to loadout. This paper describes the countdown to loadout and the work that was necessary to produce an essentially operational facility, prior to the mating of the deck and the hull.
Cathodic Protection of Offshore Structures – Problems and Solutions
Authors: Robson D. N. C.
Published: December 2007

The paper outlines the three basic options for cathodically protecting offshore structures; namely impressed current or sacrificial anodes protecting a bare metal structure or sacrificial anodes on a totally painted structure.

Some of the problems encountered by these systems are described and some specific examples experienced by Britoil structures are discussed in more detail.

Various solutions for overcoming these problems are discussed and comparisons made of their respective costs and ease of implementation.

Finally, some solutions to CP problems adopted by Britoil are described with emphasis on the difficulties in implementation.
An Overview of Recent Advances in Hydraulic Fracturing Technology
Authors: Veatch R. W. , Moschovidis Z. A.
Published: December 2007

There have been significant advances in the application and development of hydraulic fracturing technology in the past several years. This paper presents an overview of some of these advances to provide the reader with a perspective of the current fracturing state of the art. The discussion addresses economic design considerations; fracturing material behavior (propping agents, fracture conductivity, fluid loss, fluid rheology and proppant transport); field acquired fracture design, diagnostic and analysis technology (in-situ stresses and stress profiling, downhole fracturing pressure and pressure decline analysis, real-time on-site monitoring and control, and fracture mapping); and three-dimensional fracture propagation simulation. A comprehensive bibliography is provided as a resource for in-depth perusal of each area by the interested reader.
The Effects of Clay on the Displacement of Heavy Oil by Water
Authors: Martin John C.
Published: December 2007

The effects of clays on the displacement of heavy viscous oil by water are considered. Based on the assumption that the connate water is displaced ahead of the injected water in a waterflood, the theoretical flooding behaviour of homogeneous sands with small amounts of clay intermixed in the sands is investigated. Attention is given to the case where the relative permeability curve for the displaced connate water is higher than the relative permeability curve for the injected water. Under these conditions a simple graphical representation of the flooding behaviour is developed. Calculated results are presented which indicate that for highly viscous crudes displaced by fresh water the effects of small amounts of clays in the sands can cause large increases in the efficiency with which water displaces oil. Based on the calculated linear flooding behaviour a discussion is presented of the effects of clays on pattern waterfloods in which fresh water is injected. The report contains a considerable amount of evidence that indicates the effects of clays can cause large increases in the efficiency with which fresh water displaces oils with high viscosities. It is concluded that in spite of the difficulties encountered in injecting fresh water it may be a more desirable injection fluid than brine in some highly permeable reservoirs containing high viscosity crudes. The report also contains a review of the evidence of the effects of clays on core analyses and some speculations on the physical mechanisms by which clays affect the permeabilities of sands to water and oil.
Gravel-Pack Logging Experiments
Authors: Sollee S. S.
Published: December 2007

Gravel pack logging experiments were conducted in a full-scale test well to define the factors that affect tool response and to determine if quantitative log interpretation is practical. Gamma-gamma and compensated neutron gravel pack logging tools from five major service companies were used in the study. Results show that these logging tools are sensitive to varying conditions in the gravel pack environment. Quantitative interpretation of the amount of gravel in the pack is possible as long as borehole conditions such as casing size, liner configuration and wellbore fluid density are known.
Productivity Loss in Gas Condensate Reservoirs
Authors: Hinchman S. B. , Barree R. D.
Published: December 2007

Gas condensate wells, producing at a flowing bottom-hole pressure below the dewpoint suffer a more rapid decline in productivity than that predicted in theory for dry gas wells. The loss in productivity is caused by a liquid hydrocarbon accumulation near the well bore.

A compositional one-dimensional radial model has been used to predict the performance of a gas condensate well. The effect of composition (fluid properties, liquid dropout rate) and gas-oil relative permeability on gas productivity have been investigated.

Results show that relative permeability data is the most sensitive parameter in determining productivity loss. The predicted productivity decline of a gas condensate well using drainage and imbibition relative permeability data vary considerably.
An Analysis of and Correction Method for Gas Deliverability Curves
Authors: Corbett T. G. , Wattenbarger R. A.
Published: December 2007

This paper shows the effects of changing gas properties and non-Darcy flow on conventional deliverability plots. Changing gas properties cause the conventional deliverability plot to bend downward and to shift downward with time. Non-Darcy flow causes the conventional deliverability plot to bend upward. The commonly used deliverability equation does not adequately describe these effects. The real gas pseudo-pressure approach should be used to analyze backpressure tests and forecast gas well performance. A simple method of correcting existing backpressure test data to a real gas pseudo-pressure basis is presented along with a step-wise procedure of forecasting future gas well performance.
Development, Laboratory, and Field Test Results of a New Hydraulic Design for Roller Cone Rock Bits
Authors: Slaughter R. H.
Published: December 2007

This paper describes the development of a new hydraulic design for three cutter rock bits which has shown a substantial rate of penetration improvement in laboratory and field testing. The new design utilizes an integral nozzle extension which has been precisely directed toward the leading edge of the cutter and toward the formation face just prior to cutter contact. The results are improved cutter cleaning, more efficient bottom hole cleaning and improved rate of penetration.
Numerical Simulation of CO2-Heavy Oil Interactions in Fractured Medium: An Interfacial Film Concept
Authors: Ravel F. , Anterion F.
Published: December 2007

Laboratory experiments simulated static CO2 drainage without any forced sweep in fractured media of various permeabilities saturated with heavy oil. They emphasized the influence of complex thermodynamic phenomena in oil recovery processes such as CO2 dissolution and hydrocarbons vaporization.

The numerical simulation of the experiments was completed with a compositional simulator. A concept of interfacial film was developped and implemented to represent mass transfers at the matrix wall which are ruled by irreversible thermodynamics. The simulations cleared out the respective influences of various phenomena: oil swelling, stripping, gravity, capillarity. The diffusion coefficients were correlated with the porous medium characteristics and a good match was obtained.
A Mixing Rule Method for Calculating the Viscosity of CO2 and Low-Gravity Reservoir Oil
Authors: Emanuel A. S.
Published: December 2007

A mixing rule correlation has been developed for predicting the viscosity of CO2-reservoir oil mixtures from composition. The method is suitable for equation-of-state based calculations and is most useful for heavy oils. The parameters of the correlation were developed from 15 different CO2-oil mixtures. Mixture viscosity ranged from 0.2 to 5000 cp. The pressure-temperature range of the experimental data was 300-7000 psi and 70-250°F. The calculation requires the viscosity of the stock tank oil at reservoir temperature and atmospheric pressure. For best accuracy, this viscosity is measured experimentally, but it can be estimated from oil gravity. The correlation generally predicts absolute viscosity of the oil-solution gas-CO2 mixture within ±30% at reservoir condition. The percentage reduction of stock tank oil viscosity to reservoir mixture conditions is predicted on an average within ±5% of the stock tank viscosity. The accuracy of this correlation will usually be better than that of other general correlations, particularly for heavy oils at reservoir conditions. The proposed correlation may be calibrated to experimental data by adjusting one parameter.
Shale Stabilization Principles
Authors: Nesbitt L. E. , King G. P. , Thurber N. E.
Published: December 2007

Drilling troublesome shales successfully requires description and analytical tests of the shales, drilling fluid formulation, and field confirmation. This paper will point out strengths and weaknesses of our current approach and the need for better procedures.