bluuebunny/crossref_metadata_2025 huggingface dataset:
Extending the Application of Electric Analogy in Oil-reservoir Studies
Authors: Schaefer Henry
Published: June 2014

Solution by electric analogy of performance problems of reservoirs containingoil and gas has heretofore depended upon a process of successive approximationsbased on? material-balance calculations, because of variation in fluidcompressibility. By the addition or subtraction of electric condenser capacity, the analogy network can be adjusted automatically for changing compressibilitydue to evolution of gas in the reservoir. The addition of a condenser isaccomplished by an electronic circuit, which is described; subtracting acondenser is done by merely opening the electrical circuit by means of arelay.

Introduction

V. Paschkis and H. D. Baker first developed in this country a method ofapplying the analogy of flow of electric current in noninductive circuits tosolution of heat-flow problems and suggested its application for certain otherproblems, such as flow of fluids or mass transfer and chemical diffusion.Necessary details for applying the analogy to flow of fluids in porous mediawere developed by W. A. Bruce; he classified the types of analysis andpredictions that can be made by the analogy in class I, when the reservoircontains oil but no gas for the period under consideration; in Class 2, whenboth oil and gas exist in the free state in the reservoir sometime during theperiod under consideration.Duplication of bottom-hole pressure history andpredictions for class I reservoirs can be obtained directly by electricanalogy. Until now, the solution of problems pertaining to reservoirs in class2 was obtained by successive approximations along with material-balancecalculations. The object of this paper is to present a method for simplifyingthe application of electric analogy to class 2 reservoirs, resulting in asolution of these problems as direct as is possible for class I reservoirs.This is accomplished by an electronic control circuit, which adjusts theanalogy network for changing compressibilities of fluids contained in thereservoirs.

Analogy Network

In electrical phenomena the analogy to two-dimensional fluid flow in a porousmedia is that of current flow through an ideal conducting sheet. This sheet, perfectly insulated on both sides, has resistance and capacitance uniformlydistributed throughout its area but is of negligible inductance. The need forhaving the surface boundaries perfectly insulated is that good correspondencemay be had with a permeable fluid-conducting stratum bounded above and below byimpermeable media. In actual application the ideal conducting sheet, which hasdistributed parameters, is replaced by a network having lumped values ofresistance and capacitance--the resistances are series elements and thecapacitances are shunt elements.

T.P. 2125
Calculated Effect of Pressure Maintenance on Oil Recovery
Authors: Hoss Robert  L.
Published: June 2014

The application of Muskat's differential equations for predicting theperformance of a solution gas-drive reservoir to the Fullerton field indicatesthat a recovery may be expected of 14,030 bbl per acre under primary depletion, and 15,910 and 17,190 bbl per acre, respectively, under the twopressure-maintenance programs analyzed.

In this analysis it is assumed that fluid properties are the same throughoutthe reservoir, that the core data used are typical of the Clear Fork limestonein the locality, and that injected gas is completely diffused through the payzones.

The economic study of the three recovery programs considered indicates that theone in which 60 pct of the produced gas is returned to 'the formation is themost profitable.

Introduction

The purpose of this paper is to consider effect of pressure maintenance by gasinjection on the ultimate recovery of oil from a solution gas-drive reservoir.This prediction of reservoir behavior is the result calculations based on theequations presented by M. Muskat in the Journal of Applied Physics, March1945.

Reservoir

The reservoir analyzed is the Fullerton field in Andrews County, West Texas. Itsituated on a broad anticlinal structure with approximately 330'Ft of closure, and ends approximately eight miles north and south and five miles east andwest. The areal extent is taken as 16,642 acres.

The producing horizon is the Lower Clear Fork limestone of Permian age, occurring at depths from 6650 to 7350'Ft. It is divided into four zones. Forthe purposes of this study, the fluid characteristics in all zones are assumedto be the same. Therefore an equivalent zone is assumed of thickness equal tothe sum of the thicknesses of the four zones, or an average of 216 ft.

The reservoir contains 3,586,991 acre feet of producing limestone, with aninitial volume of stock tank oil in place of 918,403,100 bbl.

The average connate water saturation is 24.0 pct. The permeability ranges from6.7 md. to 12.6 md., and the porosity ranges from 7.7 pct to 11.4 pct, exceptfor occasional cavernous streaks. Based on these values, the limestone may beconsidered intergranular.

Production histories and material-balance studies have indicated that thedriving mechanism is solution gas. Water levels have been established.

Theory

It is possible to express mathematically the change in residual oil saturationwith pressure decline in a solution gas-drive reservoir as being equal to thechange in the physical properties of the fluids present in the reservoir asthis pressure decline occurs.

T.P. 2231
A Reservoir Study of the West Edmond Hunton Pool, Oklahoma
Authors: Littlefield Max , Gray L.L. , Godbold A.C.
Published: June 2014

The West Edmond pool of Central Oklahoma, a limestone reservoir, has an area inexcess of 29,000 acres and as of Sept. 15, 1946, had produced 53 millionbarrels of oil from 731 wells at an average depth of 6900'Ft. Water hasencroached into the reservoir along the west side of the pool and although thearea of water invasion is large the net volume of water influx is small, because encroachment has been primarily into a fracture system.

The most significant part of this study concerns the character of the Huntonreservoir. Geological study of cores of the producing section was made tosupplement core-analysis data. It was determined, that approximately 90 pct ofthe pore volume was contained in intergranular or sand-like porosity and 10 pctin fractures (intermediate porosity). The porous limestone is divided intoblocks by the fractures, although in the strongly dolomitic parts of theproducing section, fractures are less well developed. The low-permeabilityintergranular porosity, largely subsidiary to the high-permeability fractures, will produce oil into the fractures by evolution of solution gas. The fracturesin effect serve as drainage channels for production of oil from theintergranular porosity. Because of such a large difference in permeabilities ofthe two components, a high degree of by-passing will occur, and, accordingly, the economics involved in undertaking full-scale high pressure gas injectionoperations have been seriously questioned.

Introduction

The West Edmond Hunton pool, which covers portions of Canadian, Logan, Oklahoma, and Kingfisher Counties in Central Oklahoma, is this largestreservoir at an average depth of approximately 6900'Ft, and have yielded acumulative oil production in excess of 53 million barrels as of Sept. 15, 1946.in addition to wells completed in the Hunton limestone, 21 wells have beencompleted in the Bartlesville sand at a depth of approximately 6500'Ft, whichhave produced a total of 730,000 bbl of oil. One small producer has beencompleted in Cleveland sand at a depth of 5700'Ft. However, a study of only theHunton limestone reservoir will be presented in this paper.

The most significant phase of this study concerns the special type ofgeological core examination that was made in an effort to ascertain the typeand degree of porosity in the rock in accordance with lithologic types.

T.P. 2203
Calculated Recoveries by Cycling from a Retrograde Reservoir of Variable Permeability
Authors: Standing M.B. , Lindblad E.N. , Parsons R.L.
Published: June 2014

The recovery of the heavier components from a gas cap or retrograde pool isshown to be the greatest when the sand is cycled with a dry gas at a lowpressure. This conclusion is in direct opposition to the belief that the mostefficient production program is pressure maintenance and cycling at or near thedew point.

The results are calculated from:constant volume, variable compositionpressure-volume-temperature tests on a mixture of trap gas and liquid from aproducing well;published equilibrium constant data and the measuredcomposition of the dew-point material; andthe fact that in a sand sectionof homogeneous permeability, injected gas displaces reservoir gas nearlyquantitatively.

The results are based on the simplifying assumption that variable permeabilitysystems may be defined by the ratio of two statistical parameters, and that gasinjected into an actual sand will behave as though the sand were composed ofmany layers, each of constant permeability.

Introduction

Pressure decline in gas-condensate type reservoirs is accompanied by theformation of a liquid phase throughout the reservoir. Over the past ten yearsthe processing of the material from these types of reservoirs for the heavierhydrocarbon components and the return of the light fraction to the reservoir("cycling") has become increasingly popular. It has often been stated that thepurpose of such a program is to prevent the loss of the retrograde liquid phaseformed in the reservoir.

The purpose of this paper is to present the results of laboratory tests andcomputations concerned with several possible methods of producing a gas cap orcondensate type of reservoir.

The results show that the recovery of heavier hydrocarbons for this type ofreservoir is not a maximum under conditions of cycling at or near the dew-pointpressure. Instead, variations in permeability and the ability of the dryinjected gas to revaporize condensate, point to cycling at a considerablyreduced pressure as the optimum production-method. In addition the papersuggests a way of evaluating sands for their permeability variation.

The calculations presented in the following sections of the paper are in termsof the production of the butanes and heavier fraction from the gas gap of afield which had an original pressure of approximately 3000 psi.

T.P. 2200
Significance of World Petroleum Production Trends
Authors: Baker Warren  L. , Logan L.J.
Published: June 2014

By 1950 or soon thereafter facilities will be available in foreign countriesfor the production, transportation, and refining of about 4,305,000 bbl per dayof crude oil-a volume not far short of current United States output. This isindicated by announced plans for foreign expansion, some of the work beingalready under way. The projected potential production is about 1,500,000 bblper day or 50 pct above the record-setting foreign production of 2,810,000 bbldaily in 1946. The scheduled new foreign facilities are equivalent to almostone third of the present facilities of the United States.

Fears that so much additional foreign oil may flood world markets and disruptthe domestic industry of the United States are not justified. The projectedforeign expansion apparently has been planned on a sound business basis, withcareful consideration of the world's actual need for all the projectedadditional production. Materially increased world demand for petroleum promisesto absorb the increased supplies without ill effect upon the domestic industry.Even by applying conservative estimates of both foreign and domestic demand, itis indicated that world requirements can absorb the projected larger foreignoutput and still permit continued increase in United States production. Worlddemand would have to increase only 5.7 pct per year in the 1947 to 1950 periodto absorb the prospective supply. Such an increase may be conservativelyprojected, in view of past and current trends.

Introduction

Recent announcements of plans for expanding petroleum facilities in the MiddleEast and Venezuela foreshadow an unusually sharp increase in foreign productionin the immediate future. Therefore, the next few years will bring far-reachingchanges in world petroleum affairs, with foreign petroleum production and otheractivities assuming much greater importance than formerly.

Tabulation of figures on development already under way or planned indicatesthat in the next several years facilities will be available for producing, transporting and refining twice the prewar production of foreign fields andabout 50 pct or nearly 1,500,000 bbl a day above their record-level output of1946.

To say that foreign fields may be producing such an enlarged quantity by 1950is, of course, a statement of great significance to everyone connected with theoil industry and especially to those of the American petroleum industry. Aproduction of 1,500,000 bbl daily is equal to the combined yield of the statesof Oklahoma, Kansas, Illinois, Louisiana, Arkansas, Mississippi and New Mexico, This means that within the next several years foreign petroleum facilities willundergo a new expansion equivalent to one third of the present facilities ofthe United States.

To think of such an expansion in foreign production is to raise at this meetingthe question of what this prospective foreign development means for the UnitedStates, the American petroleum industry in general, and the American engineerand technologist in particular.

T.P. 2228
Planning a Multiple Well Directional Drilling Program for Offshore Locations
Authors: Jackson John G. , Murdoch J.B.
Published: June 2014

The many mechanical, geological, and economic factors which influence theplanning of a directional drilling program are thoroughly discussed andanalyzed. It is demonstrated that the planning of a directionally drilledmultiple-well artificial island location is a complicated undertaking and thatit is imperative that complete planning and engineering analysis be undertakenbefore the program is started. Complete planning is profitable because all ofthe factors influencing the directional work are in general interrelated andmany time compromises have to be made before a harmonious program results.

The engineering control necessary to accomplish a complicated directionaldrilling program is outlined. Various means by which engineering control can beincreased, such as cylinder drilling specifications, are given. A hypotheticalexample is developed for a complete offshore artificial island of ten wells todemonstrate the more important factors involved in the planning. Included withthis example are special charts and tables which make more rapid the draftingof directional drilling proposals and maps.

Introduction

A petroleum engineer must consider many and varied factors when planning along range directional drilling program for an offshore or inaccessiblelocation on an oil structure. The basic principles of directional drillingplanning and operation must be reconciled with his company's drillingpractices, and frequently special concessions to standard drilling andproduction practices should be made. The field techniques and tools used indirectional drilling are well known and widely used, but the deliberate, careful planning of a complete directional program is in the main a recentinnovation. This development, plus the increased demand for oil resources andthe consequent exploitation of inaccessible structures and offshore locations, has placed this problem before many engineering departments for the firsttime.

Directional drilling programs of a very complex and difficult nature havebeen successfully carried out in the Mid-Continent and Pacific Coast regions.The planning itself of a directional drilling project, however, has not had thecareful analysis it deserves and we can reasonably expect widespread futureprogress along these lines. Data and experience gained in these programs by thedirectional drilling service companies and the oil producers have been studiedwith the objective of giving the engineer a better conception of the factorswhich govern the various steps in planning a series of directional wells. Thenewest engineering procedures are the result of recent careful analysis ofyears of directional drilling work accomplished under the supervision ofdirectional drilling service companies working with the oil companies.

T.P. 2325
Oil-shale Mining
Authors: Ertl Tell
Published: June 2014

The term oil shale is defined. Foreign oil shale developments are outlinedbriefly. The richest and most extensive oil-shale deposits in the United Stateslie in western Colorado. The Bureau of Mines is opening two adjacent areas forunderground mining in western Colorado. From the first area the oil shale ismined selectively as required by the retorting plant. The second area is beingdeveloped as a unit of a full scale oil-shale mine to ascertain the mostpractical methods of mining oil shale and to determine costs. In both of thesemining areas, research will be carried on to develop new and improved practicesfor mining oil shale.

Introduction

Oil shale is a sedimentary rock containing a solid mineraloid of indefinitecomposition known as kerogen. On heating oil shale, the kerogen undergoesthermal decomposition and some of the vapor products of the decomposition canbe condensed as shale oil. Oil from shale can be a major source of liquid fuelssince extensive deposits of oil shale are known to exist throughout the world.The United States considers the establishment of an oil-shale industry onlywhen doubt exists of the adequacy of the domestic supply of crudepetroleum.

On the other hand, oil shale is not strange to foreign oil men. The industryis an old one in other parts of the world. The French industry has been inexistence since 1838, the Scottish since 1859, the Australian since 1860, theEstonian and Swedish industries since World War I, and the Manchurian industrysince 1929.

The most highly exploited oil-shale deposits are the Carboniferous shales ofScotland. About 20 seams ranging from 4 to 12 ft in thickness are worked. Theyield during recent years in Scotland has been 18 to 25 gal of shale oil perton, from 3,000,000 tons per year. The French and Swedish oil-shale depositsare of lower grade than the Scottish. The Estonian oil shale deposits are 7 ftthick, and the oil yield averages 50 gal per ton. Over 1,000,000 tons are minedeach year, half of which is used directly as fuel to substitute for coal andthe other half is used for the production of oil.

T.P. 2359
The S.P. Log: Theoretical Analysis and Principles of Interpretation
Authors: Doll H.G.
Published: June 2014

The S.P. log is shown to be a measurement of the potential drop along thedrill hole, caused by ohmic effect in the mud. The notion of static S.P. isbrought forward, and its relation to the S.P. log is discussed. Other factorsinfluencing the shape and amplitude of the log are considered; attention isgiven to conditions encountered in practice. Numerous figures are givenillustrating graphically the results; these figures are of particular interestfor comparison with field examples.

The S.P. log, although indicating permeability, is not an absolutemeasurement of permeability, nor of porosity, of the formations traversed by adrill hole. It is affected by several parameters, such as resistivity offormations and mud, thickness of formations, and others, which should beappraised carefully. Simple rules have been established for a betterdistinction of the boundaries of permeable sections, particularly in difficultcases, such as those encountered in highly resistive formations. A systematicapplication of the established principles will assist in obtaining moreinformation from the S.P. log than was possible thus far; for instance, underfavorable conditions, presence of oil may be detected, or amount of shale insands may be estimated.

Introduction

The S.P. log, or spontaneous potential log, has been known and widely usedduring the last 15 years for the location of permeable beds traversed by drillholes.

In electrical logging practice, the S.P. log is shown on the left hand sidetrack of the record (as may be seen in later examples) where it can be easilycorrelated and interpreted with the resistivity curves located to the right.Usually, the S.P. log consists of a base line, more or less straight, havingexcursions or "peaks" to the left. The base line frequently has beenfound to correspond to impervious beds, while the peaks are usually foundopposite permeable strata.

Measurements which will indicate positively the presence of permeability inthe formations, and which will give accurately the boundaries of the permeablezones, are of great importance in oil-field practice. Thus far, the S.P. log isthe best approach to such determinations; unfortunately, its interpretation isnot always evident.

With respect to the base line of the S.P. log, it may be noticed that thisline is not always at a definite location on the chart. Sometimes it may shiftabruptly, while other times a gradual drift is apparent.

As far as the peaks are concerned, their shape is not uniform; some arerounded while others are sharp. Also, from other data, it may be found thatoccasionally the peaks extend appreciably beyond the boundaries of permeablezones into zones which are not everywhere permeable.

A comparison with permeability measurements made on cores has oftenconfirmed that there was no definite correspondence between the magnitudes ofthe peaks and the permeability values.

T.P. 2463
Effect of Antifreeze Agents on the Formation of Hydrogen Sulphide Hydrate
Authors: Bond Donald C. , Russell Nelson B.
Published: June 2014

The effects of various antifreeze agents on the formation of hydrogensulphide hydrate have been studied. On a molar basis the relative lowering ofTM (the maximum temperature at which solid hydrogen sulphide hydrate can existin equilibrium with the given solution) for the various agents is: sodiumchloride 1.00, calcium chloride 1.71, methyl alcohol 0.57, ethyl alcohol 0.68, ethylene glycol 0.73, diethylene glycol 0.73, sucrose 0.87, dextrose 0.71. On aweight basis the relative lowering of TM is: sodium chloride 1.00, calciumchloride 0.91, methyl alcohol 1.08, ethyl alcohol 0.89, ethylene glycol 0.69, diethylene glycol 0.41, dextrose 0.23, and sucrose 0.15.

Introduction

The solid hydrate of hydrogen sulphide, H2S?6H2O1, is in equilibrium withwater and liquid hydrogen sulphide at 85?F at a partial pressure of hydrogensulphide approximately equal to the vapor pressure of hydrogen sulphide at thattemperature. At temperatures below 85?F, in the presence of excess hydrogensulphide (greater than the amount required to react with the water present) thehydrate is in equilibrium with liquid hydrogen sulphide at approximately thevapor pressure of hydrogen sulphide.

In the presence of excess water, the solid hydrate is in equilibrium withliquid water, containing dissolved hydrogen sulphide, at a pressure lower thanthe vapor pressure of liquid hydrogen sulphide at the same temperature. Thelower the temperature, the greater the difference between the decompositionpressure of the hydrate and the vapor pressure of liquid hydrogen sulphide atthat temperature.

Conditions conducive to the formation of solid hydrogen sulphide hydrate mayexist in wells producing a gas containing a high percentage of hydrogensulphide under high pressure, or in the lead lines from such wells. This papergives the results of tests made with various antifreeze agents which might beuseful in decomposing the hydrate or in preventing the formation of the hydrateof hydrogen sulphide.

Apparatus

Fig I shows a diagram of the apparatus used. The sample under observationwas contained in a glass tube 34 cm long, having a 6 mm id and a wall thicknessof 2.5 mm. The lower end of this tube was closed with a plug of butyl rubber.The upper end of the tube was connected to a diaphragm gauge, with a stainlesssteel diaphragm, a manometer, a vacuum pump, and a cylinder of hydrogensulphide.

The tube was held nearly horizontal, with the liquid resting along the lowerside of the tube. It was found that when the tube was held in a verticalposition, it broke with explosive violence as soon as it became filled withsolid hydrate. Presumably this was caused by the expansion which occurred onsolidification of the hydrate. The difficulty disappeared when the tube washeld in an inclined position during the tests.

T.P. 2450
Lance Creek Sundance Reservoir Performance - A Unitized Pressure-Maintenance Project
Authors: Elkins Lincoln F. , French R.W. , Glenn Wayne E.
Published: June 2014

The Lance Creek Sun dance reservoir provides a case history of 10 yearsperformance of a reservoir in which unit operation has permitted effectiveutilization of gravity drainage augmented by primary pressure control withinjection of gas in to top structural wells. Detailed performance of thereservoir is presented by means of maps of well status, reservoir pressure, individual well recovery, etc., and by pool-performance charts. Analysis ofreservoir performance indicates only minor water encroachment, so that gravity, injected gas, and expansion of gas are the main oil-expulsive agents.

A simplified theory of regional drainage of oil from upstructure location todownstructure location due to gravity is presented and checked by means of comparison of "reservoir" permeability and"well" permeability from the pool performance. Good order of magnitudeagreement was obtained.

Individual well performance and overall reservoir performance indicatepossibility that maintenance of pressure makes ineffective those parts of thereservoir in which permeability is too low to permit effective drainage of oilby action of gravity. Oil from these parts can be recovered only when pressureis reduced locally by selective withdrawal or when overall reservoir pressureis finally reduced.

Introduction

The Lance Creek oil field, Townships 35 and 36N, Range 65W, Niobrara County, Wyoming, was discovered in October 1918, when Ohio Well No. State I wascompleted in the Dakota horizon at a depth of 3665 ft, with an initialproduction of 1500 bbl daily.

T.P. 2401
A Note on the Application of the Capillary Pressure Method for the Determination of Oil Recovery
Authors: Rose Walter
Published: June 2014

Experimentation which measures differences in pressure across the interfacesof immiscible fluids in the interstitial spaces of porous media may be termed"capillary pressure experimentation". In the literature of petroleumtechnology since 1941 there have appeared twelve papers popularizing capillarypressure concepts and developing applications of these concepts for thesolution of problems of practical reservoir engineering importance, such as thedetermination of connate water, fluid distribution in transition zones, reservoir rock textural properties, and oil recovery from petroleumreservoirs.

Although a review of the literature would be justified at this time in order toreconcile the conflicting viewpoints which are contained in the cited papers, the object of this note will be of more limited scope. It is believed that therecent paper of Muskat calls sufficient attention to many of the uncertaintieswhich arise upon examination of the published literature, such that untilsatisfactory counter-proposals can be made it will serve our purpose only tomention some other like uncertainties. This will emphasize further the needconfronting petroleum technologists to reconsider and reformulate theapplication possibilities of capillary pressure experimentation. In particular, I suggest that we examine the thesis that capillary pressure experimentation asabove defined can lead to measurements reflecting the recovery of oil frompetroleum reservoirs, as was proposed first by Amyx and Yuster and was firstreduced to practice by the experimentation of Welge. In fact, I shall dealexclusively with the Welge papers since it is the principle one on this subjectwhich has appeared to date. I shall attempt to show that the possibility ofdescribing oil recovery features in terms of capillary pressure phenomena hasnot been established entirely.

The Welge paper was a pioneering effort to evaluate this recovery applicationpossibility. P. P. Reichertz comments on the Welge paper state that non-wettingphase discontinuities are developed occasionally in the Welge experiment, andrestate Muskat's argument that discontinuous fluid elements (partiallysaturating the interstices of porous media which are elsewhere saturated withsome other immiscible phase or phases) are not subject to the requirements ofhydrostatic equilibrium. It is the purpose of my comment to show that it isunnecessary to make Reichertz' postulation regarding nonwetting phasediscontinuities (however valid) when it is desired to criticize Welge'stheoretical treatment of his problem. It can be shown that Welge's method ofmeasuring values for "capillary pressure" is invalid in many instancesof application, such that his reported curves of capillary pressure versusfluid saturation often have no physical meaning, even throughout the intervalof fluid saturation where it might be otherwise suspected that no phasediscontinuities occur.
Control of Conventional and Lime-Treated Muds in Southwest Texas
Authors: Lancaster E.H. , Mitchell M.E.
Published: June 2014

A mud-conditioning program found to be very effective for drilling andcompletion operations on routine field wells requiring relatively shortdrilling time involves a moderate alkaline-tannate-bentonite treatmentresulting in an ultimate filtration rate of 10.0 cc or less (API test). Mudweight schedules are planned from pressure information on completed wells inproducing reservoirs and drillstem test data obtained on other zones not beingproduced at present. In general, terminal mud viscosities average 45 sec(Marsh). This value has been found to be sufficient to remove cuttings from thewell bore on the average well, with the slush pumps in general use on therigs.

On field wells requiring drilling times in excess of approximately 30 days, an alkaline-tannate-lime-bentonite treatment has been effective in maintainingdesirable viscosities and filtration rates with a substantial reduction inchemical costs. This system has shown particular advantage on heavily weightedmuds and those with abnormal flow-line temperatures.

For the most part, the chemical treatment utilized in wildcat drillingfollows closely the program used on field wells, depending on depth andduration of drilling operations. Wildcat mud programs are planned frominformation available from various geologic and operational sources, takinginto consideration the possibility of encountering mud problems of a specialnature in the wildcat area. Careful planning of wildcat mud programs has provedto have definite value in avoiding most serious mud problems.

An analysis and recommended treatment are presented on several special mudproblems which have been encountered in the area in the past. Those problemsdiscussed are lost circulation, blowouts, sloughing shale, excessive chloridecontamination, sulphate contamination, and prevention and correction of cementcontamination.

Introduction

Drilling-mud control in the Southwest Texas area, in general, does notinvolve the multiplicity of problems encountered in other coastal areas. Forinstance, it is rare that a mixture of problems such as lost circulation, abnormal pressure, severe sloughing shale, and others, occurs on one wellwithin close enough limits in vertical depth not to be taken care of by asensible casing program, together with a relatively clear-cut mud program.There are conditions such as the fairly widespread occurrence of abnormalpressure in the lower Frio and Vicksburg zones, and the tendency for sloughingshale in the Jackson section which make for rather expensive mud control.However, the availability of fairly accurate geologic and operationalinformation makes possible a reasonable degree of standardization on mudtreatment over a relatively large area. It may be said that, over most of thisarea where drilling is currently in progress, the natural mud made is very poorin quality, but responds readily to moderate chemical treatment to yield verygood wall-building characteristics.

T.P. 2457
Safety and Situation Awareness: "Keeping the Bubble" in Offshore Drilling Crews
Authors: Sneddon A. , Mearns K. , Flin R.
Published: June 2014

Research into human factors causes of accidents in the oil and gas industry has indicated lack of care and attention as a main cause1. One particular factor that may contribute is reduced situation awareness (SA) of those concerned. Despite the importance of SA in accident prevention, little research has investigated the effects of work factors upon awareness levels. This paper examines how the quality of drilling crews' SA can be affected by several job characteristics inherent to the offshore oil and gas industry, and the relationship with accident and near-miss rates.

A questionnaire developed to measure workload, stress and fatigue, and their impact upon SA, was distributed to offshore drilling crew personnel. Results indicated that those with increased stress and fatigue levels had poorer quality SA; however, SA was unaffected by workload. In addition, individuals who had experienced an accident during their offshore working history had significantly lower SA levels than those who had never experienced an accident.

A second study examined in more detail fatigue and shift pattern issues and their impact on SA. Here, increased fatigue was associated with poorer SA. However, while individuals working on split-shift and rotating shift patterns experienced more fatigue than individuals working all day shift, they did not experience significantly poorer SA, nor were any differences found between SA levels of individuals working shifts compatible with their circadian rhythms and individuals working incompatible shift schedules.

This paper clarifies with empirical evidence the theorised but previously untested impact of work factors such as fatigue and stress on SA. The SA questionnaire can also be used as a tool to highlight issues requiring organisational attention (e.g. sources of fatigue), and when deciding upon training programmes for individuals, targeting areas that may require additional focus (as highlighted by the scores).
Reducing Well Cost Utilizing Liner-Drilling Operations in South Texas
Authors: Billa R. , Watkins D. , Weissman M. , Clark L. , McClain E. , Sessions J. , Evans K.
Published: June 2014

Recent technological advances are driving casing and liner drilling from a niche market into the mainstream environment. Improved connections, tubulars, advances in rig technology and pipe handling have enabled operators to consider drilling with casing/liner as an option on many new wells1,2. Escalating deepwater costs and the need to further reduce onshore drilling expenses in low cost fields continue to push the technology forward.

In a mature South Texas field, an operator discovered the difficulties of drilling into formations with weak matrix strengths, loss circulation zones, and tight pore pressure/fracture gradient windows. These issues have deemed the field sensitive to aggressive drilling techniques and the operator has been forced into a conservative drilling program with reduced flow rates and lower weight-on-bit capacity. The operator needed to reduce trouble time, lower costs and make the wells more economically feasible.

A service company introduced a new liner drilling system solution to get through the extensive problematic zones. The system is engineered so the operator can ream to bottom and then continue drilling with the liner to the required target depth. The system is comprised of a drillable fixed cutter casing bit and a drill-in liner assembly designed to handle the rigors of a drilling environment (rotation, reciprocation and drilling torque). The liner system utilizes a running tool that allows the liner to be used in drilling mode handling all the required drilling loads without fear of release. Once at desired setting depth, the hydraulically balanced liner-running tool is released with a setting ball. The casing bit is manufactured from a specialized steel alloy that allows technicians to braze polycrystalline diamond compact (PDC) cutters directly to the one-piece bit ensuring a robust cutting structure capable of efficiently drilling new formation as well as reaming existing hole. The system allowed the operator to drill in the liner to TD, cement, and then drill out to the next casing point.

To date, nine intervals have been drilled with this system in South Texas. This paper will focus on the problems encountered in the field, the development work in establishing a solution for the operator, the results attained, and lessons learned through using this new technology.
Blowout Contingency and Risk-Reduction Measures for High-Rate Subsea Gas Wells in Mexilhao
Authors: Lage Antonio C.V. M. , Jacinto Carlos M. C. , Martins Francisco S. B. , Vanni Guilherme S. , Santos Otto L. A. , Moreiras Jose R. F.
Published: June 2014

The present study focuses on the description of a methodology that is used to elaborate a complete analysis of a blowout in the field of Mexilhao, which is the largest undeveloped gas accumulation in Brazil.

The methodology comprises a hazard and operability analysis (HAZOP) and a quantified risk assessment (QRA), which are necessary processes for identifying and prioritizing potential hazards. In addition, the combination of the HAZOP with the QRA makes easier the introduction of appropriate measures for reducing overall operational risks. Besides those activities, some details of a blowout contingency plan are presented, including bubble plume calculations, relief well planning, and dynamic killing design.
The entrepreneurship myth in small-scale service provision: Water resale in Maputo, Mozambique
Authors: Zuin Valentina , Ortolano Leonard , Davis Jennifer
Published: June 2014

About 20% of the urban population in sub-Saharan Africa relies on resellers of utility water for their water supply, yet the practice has received little attention either in the academic literature or in sector policy. This study uses primary data collected from more than 200 resellers in Maputo, Mozambique, through in-person surveys, participant observation and focus group discussions. Despite the widely held assumption that all small-scale water providers are profit-maximizing entrepreneurs, this study suggests that this model does not characterize resale behavior in Maputo. Instead, three non-mutually exclusive motivations provide more persuasive explanations for why households resell utility water: (1) earning cash to meet daily subsistence needs; (2) obtaining a form of informal social insurance to deal with future needs; and (3) solidifying embeddedness in social relationships by satisfying the social norms of their communities. These findings suggest that programs and policies typically designed for small-scale providers may be inappropriate for water resellers.
Analysis of water governance in Malawi: towards a favourable enabling environment?
Authors: Chiluwe Quinex W. , Nkhata Bimo
Published: June 2014

This paper examines the enabling environment for effective water governance in Malawi by specifically determining the extent to which the water acts and policies of Malawi reflect international water governance principles of participation, accountability and transparency. It is argued that governance issues determine the extent to which sound and equitable water sharing is achieved among competing uses. Despite the fact that Malawi has vast freshwater resources, the country experiences chronic water shortages in some parts; this is due to disparities in water distribution to the extent that the country has been classified to be going towards water stress by 2025. In this study, it was found that the Water Resources Act of 1969, which is currently being used by the country has not clearly set the scene for good water governance. This is despite a number of treaties on water resources management that the country has ratified. However, despite the failure to update the archaic Act of 1969, the country has taken some important strides such as the development of the National Water Policy of 2005. This policy attempts to espouse key governance prerequisites required to improve the country's capacity to deal with the impeding water crisis situation.
Processing of human faeces by wet vermifiltration for improved on-site sanitation
Authors: Furlong C. , Templeton M. R. , Gibson W. T.
Published: June 2014

The use of a vermifilter containing Eisenia fetida to degrade human faeces in a continuous wet system was explored. This paper aimed to understand the formation of vermicompost within the system, the quality of the effluent produced, and the effect of different bedding matrices. Eight filters were constructed, utilising four different bedding materials: four of these systems were seeded with 400 g of worms (vermifilters) while the others served as controls. The systems were flushed with 12 L of water per day and the experiment was split into five phases, each with different feeding regimes. Between 23.7 and 24.7 kg of fresh human faecal matter was added to the vermifilters over the 360 day period. The presence of the worms was found to increase the faecal reduction to 76% on average, compared to 17% in the control systems on average. Statistically significant reductions in phosphate, chemical oxygen demand and thermotolerant coliforms were achieved in the effluent of all vermifilters. The most suitable bedding matrix was a mixture of coir and woodchip. This study shows that there is potential for continuous treatment of human faeces using wet, on-site vermifilters.
Participation in sanitation planning in Burkina Faso: theory and practice
Authors: McConville J. R. , Kain J.-H. , Kvarnström E. , Ulrich L.
Published: June 2014

Stakeholder participation is commonly promoted as a means to boost outcomes of sanitation improvement projects, in particular in developing countries. However, there is little research on when or how this participation should occur during the process of planning a sanitation system in order to maximize the effect. This study develops a framework for analysing participation levels of different stakeholders throughout a planning process and applies it to sanitation planning guidelines and case studies from Burkina Faso. This analysis highlights that, particularly during designing of system options and selecting among these options, there exist potential weaknesses regarding who participates and how that participation may influence what type of sanitation is implemented.
Faecal sludge management in low income areas: a case study of three districts in the Ashanti region of Ghana
Authors: Appiah-Effah Eugene , Nyarko Kwabena Biritwum , Gyasi Samuel Fosu , Awuah Esi
Published: June 2014

The challenge of faecal sludge management (FSM) in most developing countries is acute, particularly in low income areas. This study examined the management of faecal sludge (FS) from household latrines and public toilets in three districts in the Ashanti region of Ghana based on household surveys, key informant interviews and field observations. Communities did not have designated locations for the disposal and treatment of FS. For household toilets, about 31 and 42% of peri-urban and rural respondents, respectively, with their toilets full reported that they did not consider manual or mechanical desludging as an immediate remedy, although pits were accessible. Households rather preferred to close and abandon their toilets and use public toilets at a fee or practise open defecation. For the public toilets, desludging was manually carried out at a fee of GHC 800–1,800 and the process usually lasted 8–14 days per toilet facility. The study showed that FSM has not been adequately catered for in both peri-urban and rural areas. However, respondents from the peri-urban areas relatively manage their FS better than their rural counterparts. To address the poor FSM in the study communities, a decentralized FS composting is a potential technology that could be used.
Risk perception, choice of drinking water and water treatment: evidence from Kenyan towns
Authors: Onjala Joseph , Ndiritu Simon Wagura , Stage Jesper
Published: June 2014

This study used household survey data from four Kenyan towns to examine the effect of households' characteristics and risk perceptions on their decision to treat/filter water as well as on their choice of main drinking water source. Because the two decisions may be jointly made by the household, a seemingly unrelated bivariate probit model was estimated. It turned out that treating non-piped water and using piped water as a main drinking water source were substitutes. The evidence supports the finding that perceived risks significantly correlate with a household's decision to treat non-piped water before drinking it. The study also found that higher connection fees reduced the likelihood of households connecting to the piped network. Because the current connection fee acts as a cost hurdle which deters households from getting a connection, the study recommends a system where households pay the connection fee in instalments, through a prepaid water scheme or through a subsidy scheme.
Turbulence transition threshold of a buoyancy-driven flow over an isothermal vertical wall
Authors: Polidori Guillaume , Hemmer Cédric , Fohanno Stéphane , Popa Catalin
Published: June 2014

The integral formalism has been developped in an attempt to predict the
mathematical transition threshold from laminar to turbulent regimes in a free
convection boundary-layer flow adjacent to an isothermal vertical wall and
also to gain a better understanding in the prediction of the turbulence
mechanism. The transition threshold is approached herein as the intersection
of the two fully developped laminar and turbulent flow regimes. The
transition for the isothermal wall condition is Prandtl number dependent and
occurs differently depending on whether the dynamical or thermal viewpoints
are considered. A change in the transition threshold behaviour is observed at
Pr=20.
Evidence on the Information Content of Text in Analyst Reports
Authors: Huang Allen H. , Zang Amy Y. , Zheng Rong
Published: June 2014

We document that textual discussions in a sample of 363,952 analyst reports provide information to investors beyond that in the contemporaneously released earnings forecasts, stock recommendations, and target prices, and also assist investors in interpreting these signals. Cross-sectionally, we find that investors react more strongly to negative than to positive text, suggesting that analysts are especially important in propagating bad news. Additional evidence indicates that analyst report text is more useful when it places more emphasis on nonfinancial topics, is written more assertively and concisely, and when the perceived validity of other information signals in the same report is low. Finally, analyst report text is shown to have predictive value for future earnings growth in the subsequent five years.
Effects of a Vigorous Gait on Mechanical Work and Oxygen Uptake during Treadmill Walking
Authors: Azuma Akihiro
Published: June 2014

This study was conducted to compare mechanical work during vigorous walking (which utilizes greater arm swings and step lengths) with that during normal walking and to examine whether individual differences (delta: vigorous walking – normal walking) in mechanical work during vigorous walking affected oxygen uptake (VO2). Six adult men ( M age = 28.5yr., SD = 3.9) performed normal and vigorous walking on a treadmill at 1.11, 1.53, and 1.94 m/sec. At all speeds, external work during vigorous walking was greater than that during normal walking, and the delta of total work was significantly correlated with that of VO2. Thus, it was suggested that increased mechanical work (particularly total work) in vigorous walking would increase the metabolic cost.