Shell (Germany)

The usefulness of the electrical resistivity log in determining reservoircharacteristics is governed largely by:the accuracy with which the trueresistivity of the formation can be determined;the scope of detailed dataconcerning the relation of resistivity measurements to formationcharacteristics;the available information concerning the conductivity ofconnate or formation waters;the extent of geologic knowledge regardingprobable changes in facies within given horizons, both vertically andlaterally, particularly in relation to the resultant effect on the electricalproperties of the reservoir. Simple examples are given in the following pagesto illustrate the use of resistivity logs in the solution of some problemsdealing with oil and gas reservoirs. From the available information, it isapparent that much care must be exercised in applying to more complicated casesthe methods suggested. It should be remembered that the equations given are notprecise and represent only approximate relationships. It is believed, however, that under favorable conditions their application falls within useful limits ofaccuracy. Introduction The electrical log has been used extensively in a qualitative way tocorrelate formations penetrated by the drill in the exploitation of oil and gasreservoirs and to provide some indication of reservoir content. However, itsuse in a quantitative way has been limited because of various factors that tendto obscure the significance of the electrical readings obtained. Some of thesefactors are the borehole size, the resistivity of the mud in the borehole, theeffect of invasion of the mud filtrate into the formation, the relation of therecorded thickness of beds to electrode spacing, the heterogeneity of geologicformations, the salinity or conductivity of connate water, and, perhaps ofgreatest importance, the lack of data indicating the relationship of theresistivity of a formation in situ to its character and fluid content. On the Gulf Coast it is found that the effects of the size of the boreholeand the mud resistivity are generally of little importance, except when dealingwith high formational resistivities or extremely low mud resistivities.Fortunately, little practical significance need be attached to the exact valuesof the higher resistivities recorded. Low mud resistivities are not common, butwhen this condition is encountered it may be corrected by replacing the mudcolumn. With the present advanced knowledge of mud control, invasion of mudfiltrate into sands can be minimized, thereby increasing the dependability ofthe electrical log. The effect of electrode spacing on the recorded thicknessof a bed is often subject to compensation or can be sufficiently accounted forto provide an acceptable approximation of the true resistivity of theformation. T.P. 1422

Abstract For several years the authors have felt the need for a source from whichreservoir engineers could obtain fundamental theory and data on the flow offluids through permeable media in the unsteady state. The data on the unsteadystate flow are composed of solutions of the equation (Equation). Two sets of solutions of this equation are developed, namely, for "theconstant terminal pressure case" and "the constant terminal ratecase." In the constant terminal pressure case the pressure at the terminalboundary is lowered by unity at zero time, kept constant thereafter, and thecumulative amount of fluid flowing across the boundary is computed, as afunction of the time. In the constant terminal rate case a unit rate ofproduction is made to flow across the terminal boundary (from time zero onward)and the ensuing pressure drop is computed as a function of the time.Considerable effort has been made to compile complete tables from which curvescan be constructed for the constant terminal pressure and constant terminalrate cases, both for finite and infinite reservoirs. These curves can beemployed to reproduce the effect of any pressure or rate history encountered inpractice. Most of the information is obtained by the help of the Laplacetransformations, which proved to be extremely helpful for analyzing theproblems encountered in fluid flow. The application of this method simplifiesthe more tedious mathematical analyses employed in the past. With the help ofLaplace transformations some original developments were obtained (andpresented) which could not have been easily foreseen by the earliermethods. Introduction This paper represents a compilation of the work done over the past few yearson the flow of fluid in porous media. It concerns itself primarily with thetransient conditions prevailing in oil reservoirs during the time they areproduced. The study is limited to conditions where the flow of fluid obeys thediffusivity equation. Multiple-phase fluid flow has not been considered. T.P. 2732

Abstract An apparatus is described whereby capillary pressure curves for porous mediamay be determined by a technique that involves forcing mercury under pressureinto the evacuated pores of solids. The data so obtained are compared withcapillary pressure curves determined by the porous diaphragm method, and theadvantages of the mercury injection method are stated. Based upon a simplified working hypothesis, an equation is derived to showthe relationship of the permeability of a porous medium to its porosity andcapillary pressure curve, and experimental data are presented to support itsvalidity. A procedure is outlined whereby an estimate of the permeability of drillcuttings may be made with sufficient accuracy to meet most engineeringrequirements. Introduction The nature of capillary pressures and the role they play in reservoirbehavior have been lucidly discussed by Levrett, Hassler, Brunner, and Deahl, and others. As.a result of these publications the value of determiningcapillary pressure curves for cores has come to be generally recognized withinthe oil industry. While considerable attention has been directed toward thesubject in an effort to provide a reliable method of estimating percentages ofconnate water, it has been recognized that capillary pressure data may prove ofvalue in other equally important applications. This paper describes a method and procedure for determining capillarypressure curves for porous media wherein mercury is forced under pressure intothe evacuated pores of the solids. The pressure-volume relationships obtainedare reasonably similar to capillary pressure curves determined by the generallyaccepted porous diaphragm method. The advantages of the method lie in therapidity with which the experimental data can be obtained and in the fact thatsmall, irregularly shaped samples, e.g., drill cuttings, can be handled in thesame manner as larger pieces of regular shape such as cores or permeabilityplugs. Based upon a simplified working hypothesis, a theoretical equation will bederived which relates the capillary pressure curve to the porosity andpermeability of a porous solid, and experimental data will be presented tosupport its validity. This relationship applied to capillary pressure dataobtained for drill cuttings by the procedure described provides a means forpredicting the permeability of drill cuttings. T.P. 2544

Fueling the future: Valeric esters can be produced by acid hydrolysis of lignocellulose to levulinic acid, followed by hydrogenation to valeric acid and its subsequent esterification (see scheme). Valeric biofuels are fully compatible for blending with gasoline or diesel, and have passed a road trial of 250 000 km. At the beginning of the 21st century mankind is facing an energy challenge as a consequence of the world’s increasing energy demand, the depletion of “easy” oil and gas fields, and the impact of CO2 emissions on the Earth’s climate (“three hard truths”).1 Much research is therefore being devoted to the exploration and development of new, carbon-lean energy sources. These include biofuels, which are the most promising option for the transportation sector in the coming decades.2 The first generation of biofuels is presently produced from sugars, starches, and vegetable oil. Although instrumental in developing the market, these biofuels are not likely to deliver the large volumes needed for the transport sector because they directly compete with food for their feedstock. A more promising feedstock is lignocellulosic material, which is more abundant, has a lower cost, and is potentially more sustainable.3 Lignocellulose is recalcitrant and, therefore, requires complex and expensive processes for upgrading to biofuels.4 Interestingly, it has been claimed that levulinic acid (LA) can be easily and cheaply produced from lignocellulosic materials by using a simple and robust hydrolysis process.5 Several LA derivatives have been proposed for fuel applications, for instance ethyl levulinate (EL), γ-valerolactone (gVL), and methyl tetrahydrofuran (MTHF).5, 6 However, these components do not exhibit satisfactory properties when blended in current fuels. Herein, we present a new platform of LA derivatives, the “valeric biofuels”, which we have been developing since 2004 and which can deliver both gasoline and diesel components that are fully compatible with transportation fuels. The manufacture of valeric biofuels (Scheme 1) consists of the acid hydrolysis of lignocellulosic materials to LA, the hydrogenation of the acid to gVL and valeric acid (VA), and finally esterification to alkyl (mono/di)valerate esters. One of these steps, the hydrogenation of gVL to VA (Scheme 1, step 3), has not been reported in the literature and was developed in our laboratory. All the other steps are known but were nevertheless revisited and, wherever possible, improved. This holds for the acid-catalyzed hydrolysis of lignocellulose to LA,5, 7 the hydrogenation of LA to gVL with the use of supported metal catalysts,8 as well as the familiar esterification of carboxylic acids. Herein, we present the main results of the hydrogenation of gVL to VA (Scheme 1, step 3), key improvements in the hydrogenation of LA to gVL (step 2), options for integrating steps 2–4, and finally a thorough evaluation of the fuel performance of the resulting valeric biofuels. Details of the experimental procedures and secondary results are available in the Supporting Information. Platform of valeric biofuels: reaction scheme and key performance factors for the individual process steps (selectivity [mol %], productivity [tproduct m−3reactor h−1], and concentration [wt %]). EV: ethyl valerate; EG: ethylene glycol; PG: propylene glycol; IER: acidic ion-exchange resin. gVL is a relatively stable product under hydrogenation conditions. It was, nevertheless, hydrogenated to VA in the presence of bifunctional catalysts that contain both hydrogenation and acidic functions. An evaluation of about 150 catalysts in a continuous high-pressure plug-flow reactor identified Pt-loaded SiO2-bound H-ZSM-5 as a very effective catalyst (Figure 1 a). However, good yields were also achieved with other zeolites and hydrogenation metals. Promising zeolites included the small-pore TON, the medium-pore PSH-3 (also called MCM-22), and the large-pore mordenite and Beta. The acidic zeolites can be replaced by other strong or weak solid acids, such as W/ZrO2 and amorphous silica–alumina (ASA). Clearly, the conversion of gVL to VA is not very demanding in terms of “shape selectivity” or acid strength. Pt, Pd, and Rh from among the noble metals are all particularly active; however, Rh was not desirable because it co-produced significant amounts of gas. Alloying Pt or Pd with other noble metals did not deliver measurable improvements. Conversion of gVL to VA over Pt/H-ZSM-5/SiO2 catalysts. a) Conversion and selectivity; b) long-term operation with multiple regeneration by hot H2 strips at 10 bar H2 and 400 °C (0.7 % metal loading; run conditions: 250 °C, 10 bar, H2/gVL molar ratio 9:1, weight hourly space velocity (WHSV)=2 h). C5−: C1–C4 hydrocarbons, PV: pentyl valerate, PeOH: 1-pentanol. The reaction mechanism of step 3 (Scheme 1) is believed to proceed by acid-catalyzed ring opening of gVL to pentenoic acid and subsequent hydrogenation to VA (Scheme 2). The production of VA requires a balancing of the acidic and hydrogenation functionalities of the catalyst: changing the metal/zeolite ratio either increases the co-production of pentenoic acid (low metal loading) or favors the formation of MTHF, pentanal/pentanol, and/or pentane/butane (high metal loading). Pentyl valerate (PV) was observed as a minor co-product (Figure 1 a) and is likely to have formed by the esterification of VA with an over-hydrogenation product, such as 1-pentanol or MTHF. For instance, co-feeding MTHF to the gVL feed resulted in a significant increase in PV production. Probable reaction mechanism for the conversion of gVL to VA over bifunctional catalysts. Catalyst extrudates of Pt/ZSM-5 bound with SiO2 (1.6 mm diameter) were operated with high activity (differential VA productivity of approximately 2 gVA gcat−1 h−1) and high selectivity (>90 mol %). This performance could be maintained for more than 1500 h with intermittent catalyst regeneration under hot H2 and/or airflow at 400 °C (Figure 1 b). Once unloaded, the spent catalyst showed marginal loss of Pt and Al (from the zeolite framework), marginal decrease in support surface area, and no measurable loss of mechanical strength of the catalyst extrudates. Pt/ASA catalysts were also very promising candidates. Although they had a lower initial activity, they showed no sign of deactivation over runs of 200–300 h. Their stability is tentatively attributed to their weaker acidity, which may facilitate the desorption of reactive intermediates, such as pentenoic acid, and thereby depress their tendency to form oligomeric deposits that poison the catalyst surface. The literature available on the hydrogenation of LA to gVL (Scheme 1, step 2) provides no information on the long-term stability of the catalysts or their resistance to leaching when operating in liquid LA.8 These issues were addressed through leaching tests of various supports, catalyst evaluation over >100 h, and analysis of spent catalyst samples. Carbon supports are known to resist aggressive aqueous media but do not survive frequent regeneration by coke burn-off. Preference was therefore given to SiO2, TiO2, and ZrO2 supports, which are stable to “decoking” conditions and appeared to retain their integrity after a week’s exposure to hot carboxylic acid (LA or VA). This contrasts with other oxidic materials (e.g., alumina, silica–alumina, and oxides of magnesium, barium, and antimony) that are leached or even dissolve under these conditions. Evaluation of some 50 catalysts showed the best performance was with Pt supported on TiO2 or ZrO2: LA was hydrogenated with high activity (differential productivity 10 ggVL gcat−1 h−1), high selectivity to gVL (>95 mol %), and marginal deactivation over 100 h (Figure 2). The main by-products, VA and MTHF, were formed with <0.5 mol % selectivity. Carbon and SiO2 supports provided a tenth of the activity observed with TiO2 and ZrO2 supports (see the Supporting Information). Pd-based catalysts also showed a much lower activity and selectivity than their Pt counterparts. Alloying the Pt with other noble metals did not improve catalytic performance (see the Supporting Information). Finally, the resistance to leaching was further confirmed by X-ray photoelectron spectroscopy analyses of spent Pt/TiO2 and PtRe/ZrO2 catalysts, which showed no significant decrease of Pt/Ti or Pt/Re/Zr ratios, and thereby no significant loss or sintering of active metal. Hydrogenation of LA to gVL over Pt/TiO2 (1 wt % metal, 200 °C, 40 bar H2, H2/LA molar ratio 5:1, WHSV=9 h). The four-step process discussed so far provides flexibility and robustness, which are invaluable in work toward deploying a novel technology. However, options for future cost reductions through process integrations have additionally been identified; for example, combining the LA and VA hydrogenation steps with the possibility of even integrating the esterification step. These schemes are described in the Supporting Information; however, one of them is worth presenting here. This is the single-step conversion of gVL to PV, which is a promising diesel component (see below). PV was indeed produced with 20–50 % selectivity upon passing gVL over Pt or Pd/TiO2 catalysts at 275–300 °C (see the Supporting Information). Pt-based catalysts tend to provide higher PV/VA ratios but also produce more undesired light hydrocarbons. VA can be recycled to the reactor for further conversion to PV. Note that PV can also be co-produced over bifunctional VA catalysts (e.g., Pt/ZSM-5) upon increasing the hydrogenation activity to produce more MTHF and/or pentanal, and recycling these co-products over the reactor for upgrading to PV. Beyond developing the manufacturing route, we also carried out a thorough study of the fuel properties of the “valeric biofuels”. In a first step, we focused on their compatibility with current fuels. The components that fail on these criteria would require modifications of vehicles and/or the distribution network and would, therefore, suffer from a slow and costly deployment. Fuel compatibility was assessed against a few basic properties such as polarity, (volumetric) energy content, boiling point, and ignition indices, for example octane or cetane number (CN) for gasoline and diesel, respectively (Figure 3). The components that successfully passed this screening were then evaluated against additional properties, such as oxidation stability, fouling tendency, corrosion, lubricity, water affinity, and response to conventional fuel additives. Screening parameters for fuel performance (MV, EV, PrV, and PV: methyl, ethyl, propyl, and pentyl valerates, respectively). The blending research octane number (BRON) values of PrV, PV, and fatty acid methyl ester (FAME) are estimated from a CN–RON correlation;10 gray shading represents the property windows of hydrocarbon fuels. Valeric biofuels passed all these tests (Figure 3). They have acceptable energy densities and more appropriate polarities than current and alternative candidate biofuels (ethanol, n-butanol, EL, gVL, and MTHF). Their volatility–ignition properties make them compatible for either gasoline or diesel applications, depending on their alkyl chain length. For example, regular gasoline splash blended with ethyl valerate (EV) at 10 and 20 vol % still meets the research (RON) and motor octane number (MON) specification for European gasoline (EN 228; see the Supporting Information). The relatively low polarity of EV makes it less sensitive to elastomer swell or water pickup than EtOH or EL (Figure 4). EV also offers the advantages of a higher energy density and lower blending volatility (dry vapor pressure equivalent, DVPE) than EtOH. This eliminates the need to remove light hydrocarbons from the base fuel prior to introducing the biocomponent. Interestingly, ethyl pentenoate (EP), which is readily produced from gVL,9 is also a promising gasoline component; it presented better octane properties than its saturated analogue EV without showing detrimental effects on other properties. Fuel performance of EV, ethanol (EtOH), and EL blended at 5 % in gasoline (the water affinity is measured for neat biofuel). RVP: Reid vapor pressure. Heavier esters, such as butyl and pentyl valerates, showed polarity, volatility, and ignition properties that are suitable for diesel (Figure 3). PV has better volatility and cold-flow property match with diesel than FAME. However, this is at the cost of a lower energy density. Di- and trivalerates, which can be produced by esterifying VA with ethylene and propylene glycols as well as glycerol, are compatible with diesel with respect to solubility and volatility. However, their modest cetane properties become limiting to the blend ratio at which they can be used in diesel. All these heavy valerate esters are soluble in diesel to high concentrations, a feature that does not apply to heavy levulinates (e.g., pentyl levulinate, PL). Valerate esters, such as FAME, provide lubricity benefits to diesel. The fuel evaluation was complemented by a road trial run on a blend of 15 vol % EV in regular gasoline. The trial was based on ten vehicles (both new and used cars) that are representative of current market technologies. Mileage was accumulated by contract drivers who followed a mixed driving pattern (500 km day−1) for a cumulative distance of 250 000 km. Attention was paid to exhaust emissions, performance, drivability, oil quality, status of engine and fuel lines, and information from the engine management system (see the Supporting Information). The presence of EV in gasoline showed no measurable impact on engine wear, oil degradation, vehicle durability, engine deposits, or regulated tailpipe emissions (EURO 4 and 5 specifications). Some power benefits were realized as a result of the good octane properties of EV. However, the lower energy density did result in a small loss in volumetric fuel economy compared to nonoxygenated gasoline. The 15 vol % EV blend was stable over the four-month period of the test and had no negative impact on the fuel storage and dispensing equipment (tanks, pipes, pumps, and filters). In summary, valeric esters represent a new class of cellulosic biofuels that can outperform previously identified candidate molecules in terms of both their manufacture and fuel properties. The initial production step, LA manufacture, is simple and robust. However, it is the advance in the conversion of LA to VA that has opened up the complete manufacturing process. The valeric platform potentially offers cellulosic biofuels that can be used as components in both gasoline and diesel up to high blend ratios. Note added upon revision: The potential of LA and gVL as intermediates for biofuel manufacture is further confirmed by a paper that appeared during revision of this communication. It reports the conversion of gVL to kerosene- and diesel-range hydrocarbons through decarboxylation to butenes and subsequent butene oligomerization.11 The catalysts were prepared by incipient wetness impregnation of various supports with soluble salts of noble metals, followed by drying at 120 °C and calcination at approximately 450 °C. The supports were commercial extrudates, where available, or based on commercial powders that were extruded in our laboratory. The catalytic tests were carried out in high-pressure steel or Hastelloy reactors equipped with liquid feed pumps, gas manifold, and cold gas–liquid product separators. The catalysts were loaded either as full extrudates or as 0.2–0.5 mm crushed particles, diluted with inert particles of SiC. The catalysts were reduced under H2 flow at atmospheric pressure and 300 °C prior to operation. The liquid product was collected and analyzed off-line by means of gas chromatography. The gaseous products were analyzed on-line by gas chromatography. More details of the procedures are reported in the Supporting Information. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

A time-tested classic, Pressure Buildup and Flow Tests in Wells presents a comprehensive study of the creation and analysis of transient pressure responses in wells. Basic principles are reviewed, and the applicability and limitations of the various techniques are critically discussed and illustrated with examples. With its detailed review of literature and extensive bibliography, this book serves as a useful guide and reference to engineers directly engaged in well pressure work.

Battery thermal management systems are critical for high performance electric vehicles, where the ability to remove heat and homogenise temperature distributions in single cells and packs are key considerations. Immersion cooling, which submerges the battery in a dielectric fluid, has the potential of increasing the rate of heat transfer by 10,000 times relative to passive air cooling. In 2-phase systems, this performance increase is achieved through the latent heat of evaporation of the liquid-to-gas phase transition and the resulting turbulent 2-phase fluid flow. However, 2-phase systems require additional system complexity, and single-phase direct contact immersion cooling can still offer up to 1,000 times improvements in heat transfer over air cooled systems. Fluids which have been considered include: hydrofluoroethers, mineral oils, esters and water-glycol mixtures. This review therefore presents the current state-of-the-art in immersion cooling of lithium-ion batteries, discussing the performance implications of immersion cooling but also identifying gaps in the literature which include a lack of studies considering the lifetime, fluid stability, material compatibility, understanding around sustainability and use of immersion for battery safety. Insights from this review will therefore help researchers and developers, from academia and industry, towards creating higher power, safer and more durable electric vehicles.

Summary The permeability, capillary properties. and m values of carbonate rocks are related to the particle size, amount of interparticle porosity, amount of separate vug porosity, and the presence or absence of touching vugs. Particle size. percent separate vug porosity, and the presence or absence of touching vugs usually can be determined visually. The amount of interparticle porosity is more difficult to determine visually and is done best by subtracting the visual estimate of separate vug porosity from the measure of total porosity obtained from wireline porosity logs or laboratory measurements. In the absence of touching vugs, the permeability, in values, and capillary properties can be estimated if the particle size, percent separate vug porosity, and total porosity are known. No acceptable method has been developed to estimate visually the permeability of touching vugs. A classification of carbonate porosity is proposed based on the data presented. This classification is intended to be used in the field or for routine laboratory description. Interparticle porosity is classified according to particle size and the dense or porous appearance of the interparticle area. Vuggy porosity is classified according to type of interconnection. Separate vugs are connected through the interparticle pore space and classified by percent porosity. Touching vugs are connected to each other and classified by presence or absence. Introduction The role played by the visual description of pore space in carbonate rocks in the field evaluation of a well has changed dramatically over the past 25 to 30 years. The change has been brought about by the development of new and improved logging techniques. The Archie classification, developed in 1952, was the only method at that time to estimate the amount of porosity in uncored wells. The development of porosity wireline tools (neutron, sonic, and density) has provided us with effective ways to measure wellbore porosity. The permeability of a carbonate rock, however, can not be measured directly by wireline tools and it is not directly related to total porosity. Visual descriptions of the pore geometry, therefore, still are needed to estimate permeability. While the Archie classification provides some insight into permeability relationships, new data presented here allow more accurate estimates. In addition, the relationship between pore types and Archie's m value and capillarity can be described. The role that the visual description of pore space can play in the evaluation is to describe factors that cannot be obtained from logging techniques but that are needed together with the logs to calculate saturations and productive capacities of the reservoir rock. This paper describes the basic geologic parameters that control the petrophysical parameters and shows how they are related. JPT P. 629^

Abstract Fluid pressure within the pore space of shales can be determined by using data obtained tram both acoustic and resistivity logs. The method involves establishing relationships between the common logarithm of shale transit time or shale resistivity and depth for hydrostatic-pressure formations. On a plot of transit time vs depth, a linear relationship is generally observed, whereas on a plot of resistivity vs depth, a nonlinear trend exists. Divergence at observed transit time or resistivity values from those obtained from established normal compaction trends under hydrostatic pressure conditions is a measure of the pore fluid pressure in the shale and, thus, in adjacent isolated permeable formations. This relationship has been empirically established with actual pressure measurements in adjacent permeable formations. The use of these data and this method permits the interpretation of fluid pressure from acoustic and resistivity measurements with an accuracy of approximately 0.04 psi/ft, or about 400 psi at 10,000 ft. The standard deviation for the resistivity method is 0.022 psi/ft, and for the acoustic method 0.020 psi/ft. Knowledge of the first occurrence of overpressures, and of the precise pressure-depth relationship in a geologic province, enables improvements in drilling techniques, casing programs, completion methods and reservoir evaluations. INTRODUCTION GENERAL STATEMENT Operators engaged in the search for and production of hydrocarbon reserves in Tertiary basins are more and more frequently confronted with complications associated with overpressured (abnormally high fluid pressure) formations. This is particularly true in the Texas-Louisiana Gulf Coast area. The problems associated with these formations are of direct concern to the combined activities of all phases of operations, i.e., geophysical, drilling, geological and petroleum engineering.1–2 Knowledge of the pressure distribution of a given area of operations would greatly reduce the magnitude of many of these complexities and in some cases would completely eliminate specific problems. This paper presents techniques developed for estimating formation pressures from interpretations of acoustic and electric log data. Specifically, the acoustical and electrical properties of shales, reflected by conventional acoustic and electrical surveys, can be used to infer certain reservoir properties, such as formation pressure, at any level in a well. It has been possible to develop these techniques because of a firm understanding of the basic principles that govern and apply to such overpressured provinces. NORMAL PRESSURES Normal pressures refer to formation pressures which are approximately equal to the hydrostatic head of a column of water of equal depth. If the formations were opened to the atmosphere, a column of water from the ground surface to the subsurface formation depth would balance the formation pressure. On the Gulf Coast, the shallow, predominantly sand formations contain fluids which are under hydrostatic pressure. These formations are said to be normally pressured or to have a normal pressure gradient.* Experience has shown that the normal pressure gradient on the Gulf Coast is approximately 0.465 psi/ft of depth. OVERPRESSURES Formations with pressures higher than hydrostatic are encountered at varying depths in many areas. These formations are referred to as being abnormally pressured, abnormally high pressured, or overpressured. Formation pressures up to twice the hydrostatic pressure have been observed. These formations require extreme care and much expense to drill and to exploit. COMPACTION-FLUID PRESSURE RELATIONS THEORY The generation of overpressured formations in Tertiary sections of the Gulf Coast and several other Tertiary sedimentary basins is, in general terms, considered to be primarily the result of compaction phenomena.1 This portion of the paper presents a brief review of the theory which associates compaction and fluid pressure relations, and should thus provide the necessary background for an understanding of the techniques presented. See Hubbert and Rubey4 for a more comprehensive treatment of this subject. GENERAL STATEMENT Operators engaged in the search for and production of hydrocarbon reserves in Tertiary basins are more and more frequently confronted with complications associated with overpressured (abnormally high fluid pressure) formations. This is particularly true in the Texas-Louisiana Gulf Coast area. The problems associated with these formations are of direct concern to the combined activities of all phases of operations, i.e., geophysical, drilling, geological and petroleum engineering.1–2 Knowledge of the pressure distribution of a given area of operations would greatly reduce the magnitude of many of these complexities and in some cases would completely eliminate specific problems. This paper presents techniques developed for estimating formation pressures from interpretations of acoustic and electric log data. Specifically, the acoustical and electrical properties of shales, reflected by conventional acoustic and electrical surveys, can be used to infer certain reservoir properties, such as formation pressure, at any level in a well. It has been possible to develop these techniques because of a firm understanding of the basic principles that govern and apply to such overpressured provinces. NORMAL PRESSURES Normal pressures refer to formation pressures which are approximately equal to the hydrostatic head of a column of water of equal depth. If the formations were opened to the atmosphere, a column of water from the ground surface to the subsurface formation depth would balance the formation pressure. On the Gulf Coast, the shallow, predominantly sand formations contain fluids which are under hydrostatic pressure. These formations are said to be normally pressured or to have a normal pressure gradient.* Experience has shown that the normal pressure gradient on the Gulf Coast is approximately 0.465 psi/ft of depth. OVERPRESSURES Formations with pressures higher than hydrostatic are encountered at varying depths in many areas. These formations are referred to as being abnormally pressured, abnormally high pressured, or overpressured. Formation pressures up to twice the hydrostatic pressure have been observed. These formations require extreme care and much expense to drill and to exploit. THEORY The generation of overpressured formations in Tertiary sections of the Gulf Coast and several other Tertiary sedimentary basins is, in general terms, considered to be primarily the result of compaction phenomena.1 This portion of the paper presents a brief review of the theory which associates compaction and fluid pressure relations, and should thus provide the necessary background for an understanding of the techniques presented. See Hubbert and Rubey4 for a more comprehensive treatment of this subject.

Abstract The pressure drop in a well per unit rate of flow is controlled by the resistance of the formation, the viscosity of the fluid, and the additional resistance concentrated around the well bore resulting from the drilling and completion technique employed and, perhaps, from the production practices used. The pressure drop caused by this additional resistance is defined in this paper as the skin effect, denoted by the symbol S. This skin effect considerably detracts from a well's capacity to produce. Methods are given to determine quantitativelythe value of S,the final build-up pressure, andthe product of average permeability times the thickness of the producing formation. Introduction Equations which relate the pressure in a well producing from a homogeneous formation with pressures existing at various distances around the well are generally used within the industry. The relation is quite simple when the fluid flowing is assumed to be incompressible. It becomes somewhat more complicated when the flowing fluid is considered compressible so that the duration of the flow can be considered. In each case the major portion of the pressure drop occurs close to the well bore. However analyses of pressure build-up curves indicate that the pressure drop in the vicinity of the well bore is greater than that computed from these equations using the known, physical characteristics of the formation and the fluids. In order to explain these excessive drops it is necessary to assume that permeability of the formation at and near the well bore is substantially reduced as a result of drilling, completion and, perhaps, production practice. This possibility has been recognized in the literature. A method to compute the pressure drop due to a reduction of the permeability of the formation near the well bore, which is designated as the skin effect, S, is given in the following paragraphs. To start, equations normally used to describe flow in the vicinity of a well are given without considering this effect. These equations then are modified to include the effect of a skin on the pressure behavior. Finally a method is given to estimate the effect of the skin on the pressure and production behavior of a well.

We describe droplet microfluidic strategies used to fabricate advanced microparticles that are useful structures for the encapsulation and release of actives; these strategies can be further developed to produce microparticles for advanced drug delivery applications. Microfluidics enables exquisite control in the fabrication of polymer vesicles and thermosensitive microgels from single and higher-order multiple emulsion templates. The strategies used to create the diversity of microparticle structures described in this review, coupled with the scalability of microfluidics, will enable fabrication of large quantities of novel microparticle structures that have potential uses in controlled drug release applications.

Abstract Displacement of oil by polymer solution has several unique characteristics that are not present in normal waterflooding. These include non-Newtonian effects, permeability reduction, and polymer adsorption. polymer adsorption. The rheological behavior of the flow of polymer solution through porous media could be Newtonian at low flow rates, pseudoplastic at intermediate flow rates, and dilatant at high flow rates. The pseudoplastic behavior is modeled with the pseudoplastic behavior is modeled with the Blake-Kozeny model for power-law model fluids. The dilatant behavior is modeled with the viscoelastic properties of the polymer solution. properties of the polymer solution. The reduction in permeability is postulated to be due to an adsorbed layer of polymer molecular coils that reduces the effective size of the pores. A dimensionless number has been formulated to correlate the permeability reduction factor with the polymer, brine, and rock properties. This polymer, brine, and rock properties. This dimensionless number represents the ratio of the size of the polymer molecular coil to an effective pore radius polymer molecular coil to an effective pore radius of the porous medium.A model has been developed to represent adsorption as a function of polymer, brine, and rock properties. The model assumes that the polymer is properties. The model assumes that the polymer is adsorbed on the surface of the porous medium as a monolayer of molecular coils that have a segment density greater than the molecular coil in dilute solution. Introduction Displacement of oil by polymer solutions has several unique characteristics that are not present in normal waterflooding. These include non-Newtonian effects, permeability reduction, and polymer adsorption. In principle, the effects could polymer adsorption. In principle, the effects could be measured experimentally for each fluid-rock system of interest over the entire range of flow conditions existing in the reservoir. However, there are seldom complete data on all systems of interest. A correlation that represents these effects as a function of the polymer, brine, rock properties, and flow conditions would result in a more accurate evaluation of systems that may not have been measured in the laboratory at the desired conditions. Moreover, if the dependence of these effects on the system properties were known, it would aid the search for an optimal system. A model is proposed for representing the effects as a function of the system properties. The model is consistent with a number of experimental observations but enough data have not yet been acquired to determine the extent of applicability of a correlation. It is hoped that the presentation of these models will encourage further research to verify or improve the models. MODEL FOR PSEUDOPLASTIC FLOW THROUGH POROUS MEDIA The Blake-Kozeny model represents the porous medium as a bundle of capillary tubes with a length that is greater than the length of the porous medium by a tortuosity factor, tau. The equivalent radius of the capillary tubes can be related to the particle diameter of a packed bed from the hydraulic radius concept or to the permeability and porosity by comparison with Darcy's law for Newtonian fluids.The modified Blake-Kozeny models represents the flow of a power-law fluid in the capillaries. The relationship between the pressure drop and flow rate can be expressed as a product of the friction factor and Reynolds number.(1) This expression can be related to the apparent viscosity and the rock permeability and porosity through the following relationships:(2) where(3) SPEJ P. 337

A description is given of a method for solving some nonlinear programming problems. The mathematics of this method are quite simple and are easy to apply to electronic computation. A numerical example, a model construction example, and a description of a particular existing computer system are included in order to clarify the mode of operation of the method.

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract An iterative method is proposed for the inversion of sparse band-structured matrices of the type that are common in numerical reservoir simulators. The method utilizes orthogonalizations and minimizations to achieve a fast convergence rate. Tests have shown that the method is highly competitive compared with other iterative techniques. The rate of convergence is insensitive to the use of iteration parameters, non-symmetry of the matrix, and ratios of off-diagonal bands in symmetrical matrices. 1. Introduction A time-consuming part of the calculation in numerical reservoir simulators is the inversion of a large set of simultaneous linear equations. (1) For example when effecting a solution by the Implicit Potential - Explicit Saturation method x would represent the pressure or potential field, whilst A would be a matrix of transmissibility coefficients describing the interflow of fluids between grid blocks. In the common finite difference approaches, A is a sparse banded matrix, as depicted in figure 1 for a five-point finite difference representation of a two dimensional system. Often, the diagonal element of A is approximately equal to the negative sum of the off-diagonal elements in a given row. Because of the sparseness of A, iterative methods appear at first sight attractive compared with direct methods. However, specialized direct routines with increased efficiency have become available in recent years. Of the iterative methods SIP (strongly implicit procedure) is possibly the most widely used. SIP has the possibly the most widely used. SIP has the disadvantage that its convergence rate depends strongly on a set of iteration parameters whose optimal values can be difficult to find. A new highly competitive iterative method for symmetric matrices, a minimization process conceptually based on the conjugate-gradient technique, has lately been developed. The numerical examples and proofs quoted in reference 4 indicate that minimization processes can be expected to offer the following advantages: Convergence more readily guaranteed. No need for iteration parameters. Insensitivity to number of equations. Insensitivity to transmissibility ratios (the ratios of the off-diagonal bands in figure 1).

By combining ultraviolet and x-ray photoelectron spectroscopy with inverse photoemission spectroscopy, we find that the conduction-band alignment at the CdS/CuInSe2 thin-film solar-cell heterojunction is flat (0.0±0.2 eV). Furthermore, we observe a valence-band offset of 0.8±0.2 eV. The electronic level alignment is dominated by (1) an unusually large surface band gap of the CuInSe2 thin film (1.4 eV), (2) by a reduced surface band gap of the CdS overlayer (2.2 eV) due to intermixing effects, and (3) by a general influence of the intermixing on the chemical state near the interface.

Efforts to restore the native oyster in the Chesapeake Bay enjoy enormous public support and have consumed and continue to consume vast, some would argue unreasonable and unjustifiable, amounts of funding. Despite this support the stated goals of restoration efforts are poorly defined and consequently provide no realistic measures of success in terms of time, space, or biomass. Quantitative approaches used successfully in management of and rebuilding plans for other marine and estuarine species have not been appropriately applied. Basic information in oyster population dynamics and ecology has been inadequately appreciated in defining the quantitative problem. Given these limitations it is not surprising that little success has been achieved despite the massive investment. We note a lack of ability to predict recruitment, and limit the ingress and impact of disease. Without control of both of these functions, populations cannot be managed in a self-sustaining rebuilding mode within the footprint that they either currently occupy or formerly occupied. Sustained expansion of that footprint through substrate provision is prohibitively expensive, beyond the limits set by availability of substrate material, and futile in the presence of disease and susceptible oysters. Without attaining a substantially increased and rebuilding population, ecological services will be limited. Water quality impacts will, in reality, be modest, local and seasonal, and still subject to being overwhelmed by periodic storm events. Coherent and rational evaluation of biological limitations will lead to more realistic, and indeed very modest goals for ecological restoration. We must accept the fact that efforts to date to restore native oyster populations have failed and the prognosis for improvement of this situation is continued failure. The argument is proffered that stabilizing the present bed footprint with a realistic and sustainable population and the promotion of aquaculture to increase commercial yield is a more predictable and stable economic investment. Each of these options is consistent with the most realistic ecological outcome and should take priority in future efforts.

The economic performance of a waterflood or a water disposal project can be significantly affected by suspended solids in the injection water. Here are methods and a theory that can be used to interpret water quality data obtained with membrane filters or cores and to predict well impairment caused by suspended solids. predict well impairment caused by suspended solids. Introduction In a waterflood or a water disposal project the possibility exists that suspended solids will cause the possibility exists that suspended solids will cause the injection wells to become impaired. Filtration can usually reduce the concentration of suspended solids; however, the cost of water treating should be balanced against the cost of other alternatives, such as periodic stimulation or replacement of injection wells. In some cases extensive water treating can be justified, but under other circumstances it will be more profitable to inject untreated water. Water quality is affected by several types of contaminants, including suspended silts, clays, scale, oil and bacteria. Any of these may be the predominant source of improvement in a particular injection water and environment. Formation cores, artificial cores. and membrane filters have been used in the industry to monitor suspended solids and to evaluate water quality. Some studies have defined water quality in terms of filtration rates or other experimental data. The disadvantage of these empirical definitions is that they cannot be directly related to well impairment. This paper proposes a measure of water quality that is defined as the ratio of the concentration of suspended solids to the permeability of the filter cake formed by those solids. The water quality ratio can be obtained directly from membrane or core filtration data and can be used to calculate the rate of formation impairment. Formation Impairment from Suspended Solids In considering the effects of suspended solids, some measure of the rate of impairment is needed. A convenient way to estimate how long an injector can be used before stimulation is required is to calculate its half-life. The half-life is defined as the time required for the injection rate to decrease to 50 percent of its initial value. The time required to reach some other fractional reduction in rate can also be calculated. Impairment from suspended solids is thought to occur by one of the following mechanisms (see Fig. 1): The solids form a filter cake on the face of the wellbore (wellbore narrowing); The solids invade the formation, bridge, and form an internal filter cake (invasion); The solids become lodged in the perforations (perforation plugging); and The solids settle to the bottom of the well by gravity and decrease the net zone height (wellbore fillup). Each of the four basic impairment mechanisms is modeled in Appendix A for a constant-pressure-drop process, Equations are derived that express the time process, Equations are derived that express the time required for the injection rate to decline to some fraction a of its initial value. For each mechanism, this time can be expressed as the product of the two function, F and G. P. 865

Tests with physical models have shown that sand production and pack impairment are minimized when the ratio of pack median grain size to formation median grain size is between 5 and 6. In a study of the inertia and viscosity effects of flow in gravel packed wells it was found that increasing the size and the density of the perforations should increase productivity. Introduction Gravel packs have been used extensively along the Louisiana Gulf Coast in an effort to reduce or avoid sand production from unconsolidated formations. Statistics show, however, that through 1966, gravel packs were only about 70 percent successful.*The early literature on gravel pack design is based primarily on the work of Coberly and Wagner and of Hill. Coberly's work in essence suggested that a gravel pack having granular particles of diameter 10 times the formation grain size at the 10-percent-coarse point on a cumulative sieve analysis would provide effective sand control. Numerous failures of this criterion were noted, especially in the Gulf Coast sands. Hill suggested that the ratio of 10 be reduced to 8. Failures were still noted in many applications, At least one writer suggested concentrating on the "fines" end of a cumulative sieve analysis. Winter-burn states that "actual experience in the field has shown that sand entry can virtually be eliminated by the use of gravel which is approximately 10 times the grain size of the 10 percentile of the finest sand to be screened." Clearly a finer gravel will be more effective in screening formation particles. However, it must be evaluated in the light of how the finer gravel affects permeability and reduces production.Depending upon the writer, recommended ratios of gravel to the 10-percent-coarse point may range from 4 to 13. Other suggestions appear in the literature; see, for example, the paper by Tausch and Corley for a summary of earlier gravel pack investigations.In more recent literature, Sparlin has discussed gravel placement rate and fluid viscosity in his recommendations for a "slurry pack." Schwartz recommends a size ratio of 6 at the 10-percent-coarse point and at the 40-percent point for uniform and nonuniform sands, respectively. Williams uses Schwartz's grain-size ratio of 6 and finer and discusses well productivity as a function of perforation size and density.In addition to the apparent disagreement on the geometrical basis for gravel pack design, a more subtle lack seems to exist. Few writers have explored the influence of flow parameters on the functioning of gravel packs. Sage and Lacy appear to be the first authors who attempt to take hydrodynamic (and other) factors into consideration. We supposed that under certain conditions, hydrodynamic factors could possibly outweigh geometric factors in the functioning of gravel packs. This investigation, begun in 1967, proceeds from that basic premise. Laboratory Test and Evaluation Program A large number of variables are involved both directly and indirectly in gravel pack behavior. Five were considered to be most significant and fundamental to the study. JPT P. 205^

Abstract When operated properly, in situ soil venting or vapor extraction can be one of the most cost‐effective remediation processes for soils contaminated with gasoline, solvents, or other relatively, volatile compounds. The components of soil‐venting systems are typically off‐the‐shelf items, and the installation of wells and trenches can be done by reputable environmental firms. However, the design, operation, and monitoring of soil‐venting systems are not trivial. In fact, choosing whether or not venting should be applied at a given site is a difficult decision in itself. If one decides to utilize venting, design criteria involving the number of wells, well spacing, well location, well construction, and vapor treatment systems must be addressed. A series of questions must be addressed to decide if venting is appropriate at a given site and to design cost‐effective in situ soil‐venting systems. This series of steps and questions forms a “decision tree” process. The development of this approach is an attempt to identify the limitations of in situ soil venting, and subjects or behavior that are currently difficult to quantify and for which future study is needed.

The Waxman-Smits physical model for describing conductivity in shaly sand has been extended to allow for oil-bearing sand, and the required assumptions have been confirmed by laboratory measurements. A conclusion from the tests is that the effective concentration of clay-exchange cations increases in proportion to the decrease in water saturation. The temperature coefficients of electrical conductivity for a group of shaly sands were measured and these data were treated by the same model. Introduction Waxman and Smits have recently advanced a simple physical model describing shaly sand conductivities. physical model describing shaly sand conductivities. The model assumes:a parallel conductance mechanism for free electrolyte and clay-exchange cation components,an exchange cation mobility that increases to a maximum and constant value with increasing equilibrating electrolyte concentration, andidentical geometric conductivity constantsapplicable for the contributions of both the free electrolyte and the clay-exchange cation conductance to the sand conductivity. The general equation for water-saturated sands is then obtained:(1) with(2) Co and Cw are the specific conductances of the sand and equilibrating brine, respectively (mho cm). F* is the shaly sand formation resistivity factor, related to porosity (0) according to an Archie-type relation:(3) where m* is the porosity exponent. 1/F* is the slope of the straight-line portion of the Co vs Cw, curve. Qv is the effective concentration of clay-exchange cations (equiv/liter or meq/mi) and can be determined independently from the ratio of cation exchange capacity (meq per 100 gm of rock) per unit pore volume of rock (ml per 100 gm of rock). B represents the equivalent conductance of the clay counterions as a function of Cw with units of mho cm2 meq -1. lambda Na (or B max) is the maximum equivalent ionic conductance of the (sodium) exchange ions, and a and lambda are empirical constants. Waxman and Smits report values (Group 1 samples) of a = 0.83, = 0.02, and lambda Na = 38.3 cm2 equiv- 1 ohm-1 at 25 degrees C. Somewhat different values of the a, y, and lambda Na were reported by Waxman and Smits for another and considerably smaller set of shaly sand samples (Group 2). These were a = 0.6, lambda = 0.013, and lambda Na = 46.0 CM2 equiv-1 ohm-1 at 25 degrees C. Further work reported here (Table 2) supports the values obtained for the Group 1 samples. The Qv values calculated from conductivity data and a value of lambda Na = 38.3 cm2 equiv-1 ohm-1 agree within experimental error with Qv values determined by independent laboratory procedures for the new group of shaly sands used for this study. JPT P. 213

Published in Petroleum Transactions, AIME, Volume 201, 1954, pages 182–191. Abstract A method has been developed for calculating the average pressure in a bounded reservoir. The reservoir is first divided into the individual drainage volumes of each well, by using the criterion that at steady state each individual drainage volume is proportional to a well's production rate. The average pressure in each drainage volume is then calculated by a method developed in the report. By volumetrically averaging these individual drainage volume pressures, the average pressure in the entire reservoir is obtained. To calculate the average pressure in each drainage volume, a correction is applied to the ordinary extrapolated pressure, i.e., the pressure obtained by extrapolating to infinite time the linear portion of the graph of closed-in pressure versus log [?t/(t + ?t)], where ?t is the closed-in time and t the production time. The correction, which is a function of the production time, is presented in graphical form for different shapes of the drainage area (horizontal cross section of the drainage volume). Introduction It is important to be able to find the volumetric average pressure in a reservoir so that the size of the reservoir may be determined from material balance calculations. It is also desirable to be able to find the approximate distribution of pressure within a reservoir for detection of fluid movement. The purpose of this paper is to present a method for calculating both the average reservoir pressure and the approximate distribution of pressure within a bounded reservoir that is, a reservoir with no water drive. In reservoirs where the pressure builds up rapidly after wells are shut in, the determination of average pressure generally poses little problem, for one often need only average the final buildup pressures. It is when pressure buildup is slow that difficulties arise. For practical and economical reasons, the time allowable for closing in wells is limited. If at the maximum allowable closed-in time the pressure has not reached a constant value (and this is more often the case than is generally realized), calculation of average pressure presents difficulties.