Horizontal Barriers Research Articles

Reservoir Description of a Sand-Rich Submarine Fan Complex for a Steamflood Project: Upper Miocene Potter Sandstone, North Midway Sunset Field, California: ABSTRACT

Nearly 650 m of cores from the upper Miocene Potter sandstone in Mobil's Alberta/Shale property, North Midway Sunset field, California, were examined to determine depositional facies, sand-body geometry, and reservoir quality for a proposed steamflood project. The Potter represents a sand-rich submarine fan complex with braided-channel, meandering-channel, levee, and crevasse-splay facies. The braided-channel facies (gravel and coarse sand) is thick (up to 100 m), sheetlike (> 500 m wide), and highly permeable (10,000 + md). The meandering-channel facies (coarse to medium sand) is up to 20 m thick, over 400 m long, lenticular in geometry, and exhibits an upward decrease in permeability (e.g., 9000 to 500 md) related to grain size that fines upward. The levee facies (in bioturbated sand) is up to 21 m thick, shows variable geometry, and is generally low in permeability (100-1500 md). The crevasse splay (medium sand) is up to 12 m thick, sheetlike (> 300 m wide), and shows moderately high permeability (2000-8000 md). The braided-channel facies was a product of density-modified grain flows, and the remaining three facies were deposited by turbidity currents. Steam flooding of the Potter reservoir should perform extremely well because the entire reservoir is composed of relatively clean sandmore » and the reservoir lacks both horizontal and vertical permeability barriers.« less

The Application of New Approaches for Shale Management in a Three-Dimensional Simulation Study of the Frigg Field

Summary The Frigg field is a major North Sea gas reservoir composed of turbiditic sediments. This paper describes the detailed geologic modeling and three-dimensional (3D) reservoir simulation of the field. A geologic model containing sand lobes and intercalating shales has been defined from seismic and well data. Special attention was paid to the realistic modeling of the shales. The more continuous (deterministic) shales between the turbiditic sand lobes of the reservoir were directly implemented in the model as horizontal flow barriers. The more discontinuous shales within the lobes were modeled with the method of Haldorsen and Lake1 and Begg and King.2 This method uses statistical geologic information and well data to calculate effective vertical permeability. The simulator was built as a 3D, two-phase (gas/water) model. Field data for 8 years of production were matched. A good match of both fluid levels and pressures was obtained. This reservoir study demonstrates that the impact of the shales on the reservoir behavior in general and the movement of the gas/liquid contact (GLC) in particular is essential.

Reservoir Description for Exploration and Development: What is Needed and When?: ABSTRACT

The biggest challenge for geologists, geophysicists, and petroleum engineers now and in the decades ahead is to significantly improve hydrocarbon recovery from all new and previously discovered reservoirs. Keystone of the methodology required to improve oil and gas production, as well as to evaluate and delineate new reserves, is a detailed reservoir description. This is a characterization of the reservoir and nonreservoir rock-fluid system that is appropriate in content and End_Page 1522------------------------------ detail for the particular stage of exploration and production. The type and amount of data required for a proper reservoir description are diverse, from several disciplines, and depend upon the stage of the reservoir's exploration and production cycle. The cycle is viewed as a continuous series of overlapping stages from discovery, through appraisal, planning, development, and reservoir management. The concepts and data needed to define and exploit reservoirs become more complex and quantitative as the production becomes more mature. Concepts, data, and models developed during the production phases, when reapplied to exploration, provide important guides to the explorationists for evaluating trapping elements, seals, reservoir quality, and risks in basin and wildcat evaluation. one looks at the question When is a reservoir description needed? the answer is simple. The need starts once a discovery is made and the discovery is being appraised as to the best estimates of hydrocarbon in place, recoverable reserves, and production rates. As a field or reservoir goes through its typical cycle of discovery, appraisal, planning, development, and reservoir management, a more complete description is both necessary and possible. A critical first step in the reservoir description process is recognizing any correlative reservoir subzones or layers and any intervening dense, impermeable, or low-permeability strata. Knowledge of the depositional/diagenetic processes controlling reservoir and nonreservoir rock is essential to determine one's ability and degree of confidence in correlating these units. Seismic sequence, lithologic, and fluid analyses, and well-documented outcrop studies can add significantly in establishing interwell correlations. Recognizing and mapping all vertical or horizontal fluid-flow barriers, as well as theif zones or zones of unusual permeability contrast and faults, are critically important to all recovery processes. Flow-test data dovetailed with knowledge of the reservoir and nonreserv ir framework based on geology/geophysics provide the best reservoir description of continuity/discontinuity. Structural and stratigraphic maps, cross sections, and fence-and-block diagrams convey the three-dimensional geometry, distribution, and continuity of the reservoir, nonreservoir, and aquifer. A variety of computer programs aid in preparing these illustrations. Isopach maps without the accompanying detail correlation sections have been the pitfall of many projects. Net-pay isopach maps drawn to provide the basis for determining hydrocarbons in place have tricked many petroleum engineers into believing a reservoir is more continuous, more homogeneous, and less stratified than it actually is. The importance of discontinuous shale barriers of limited areal extent on coning and the drainage of oil from a gas-invaded area illustrate the need to include shale dimensions in many types of recovery calculations and predictions. The recognition, selection, and description of reservoir units or layers, and the communication of this picture to the petroleum engineers are fundamental contributions and responsibilities of the geologists/geophysicists. A coordinated data-acquisition program can greatly improve the probabilities of correct assessments in discovery, appraisal, planning, development, and reservoir management. A good reservoir description designed to answer key reservoir performance questions is a fundamental tool. The incremental well costs to obtain adequate data for a reservoir description are very small compared with its value in improved recovery. The time to complete a reservoir description is before significant expenditures are planned and spent. Mathematical models and simulation of reservoir performance that do not have a realistic reservoir rock-fluid description are interesting, but are expensive exercises that potentially lead to inappropriate or incorrect management decisions. In exploration ventures, detailed reservoir-description studies made during the production stages provide the critical data needed by the explorationist to estimate reservoir and seal quality from seismic, well logs, and samples. End_of_Article - Last_Page 1523------------

Application of Facies Analysis to Improve Gas Reserve Growth in Fluvial Frio Reservoirs, La Gloria Field, South Texas: ABSTRACT

Geologically based infill-drilling strategies hold great potential for extension of domestic gas resources. Traditional gas-well drilling and development have often assumed homogeneous and continuous reservoirs; uniform gas-well spacing has resulted in numerous untapped reservoirs isolated from other productive sand bodies. Strategically located infill wells drilled into these undrained reservoirs may ultimately contact an additional 20% of original gas in place in Texas gas fields. Tertiary formations in the Texas Gulf Coast commonly exhibit multiple fluvial and fluvial-deltaic reservoirs that contain vertical and horizontal permeability barriers. For example, the Frio La Gloria field (Jim Wells and Brooks Counties, Texas) contains isolated and compartmentalized reservoirs that can be related to the irregular distribution of heterogeneous facies. Net-sand and log-facies maps in areas of dense well spacing delineate relatively continuous pay defined by lenticular point-bar and channel-fill deposits 1,500-2,500 ft wide. These point-bar deposits are flanked laterally by sand-poor levee and splay facies that isolate the reservoirs into narrow, dip-elongate bands.

Impact of Early Diagenesis of Eolian Reservoirs, Great Sand Dunes National Monument, Colorado: ABSTRACT

Dune and associated alluvial and playa deposits at Great Sand Dunes National Monument, Colorado, provide an excellent opportunity to study early diagenetic development of vertical and horizontal permeability barriers in recent eolian deposits (> 10 ka). Cements observed include calcite, aragonite, protodolomite(?), amorphous silica, iron hydroxide, smectite, trona, and halite. Cementation is controlled by the availability of water, with several hydrologic subenvironments producing different cements. Evaporative cementation in dunes adjacent to playas is commonly dominated by trona and halite, but calcite, aragonite, and amorphous silica also bind the sediment. These cements are generally most concentrated in fine laminations where capillary action has pulled water into dunes. Iron hydroxides, calcite, and amorphous silica precipitate at the interface between ground water and streams or lakes, where the pH gradient may exceed 5 pH units (pH 5.7-11.5). Subsequent movement of the ground-water table can result in cross-cutting cement zones. Early cementation in dunes prevents deflation and provides a mechanism for preservation of the reservoir unit. Intense cementation may permanently occlude porosity, or leaching may reestablish well-interconnected porosity. An understanding of the extent and composition of early cement zones can be used to improve hydrodynamic models for production and enhanced recovery. End_of_Article - Last_Page 276------------

The Polish Party in Crisis, 1980–1982

Over the last three years, the Polish United Workers’ Party has suffered a major crisis, the most substantial crisis of any Communist party in any Communist party state. The disintegration of the party was at least partly responsible for both the development of Solidarity in the summer of 1980 and the imposition of martial law in December 1981. The lack of trust in the party and its authoritarian and unrepresentative character led the workers to demand an institution more responsive to their own needs. But the growth of Solidarity during 1981 and the continuing disintegration and fragmentation of the party led the military to preempt the leading role of the party in 1982.The collapse of the party in 1980 and 1981 was due to a number of factors. The party leadership had to bear the burden of the economic failures of the late 1970s and the consequent decline in the standard of living. The party itself had grown rapidly in size during that period, even though the influence of ordinary party members and local party organizations declined in the face of increasing tendencies toward centralization in the second half of the decade. This development led to problems of morale even within the party and to the growth of horizontal barriers between the membership and its leaders. The population at large was increasingly annoyed and disgusted with the failure of the party to improve the economic situation and to allow a more honest and open discussion of Poland's problems. The dissatisfaction was compounded by the widespread perception that the elite was increasingly looking after its own interests only and that benefits and privileges were accruing only to those in power.

Studies on the Thermal Separation Column. V. Thermal Separation Column Having Horizontal Barriers

Abstract The performance of a hot wire type thermal separation column in which many horizontal barriers of Teflon or copper plates are installed has been examined. At the optimum spacing of barrier plates, the quality factor defined by (2AL)barrier/(2AL)open exceeds 3. This means that a barrier column constructed properly has a performance equivalent to that of an open column of three times taller in height. Visualization of a stream line in the barrier assembly indicates that a helical transverse motion takes place in the space partitioned by two adjacent barrier plates.

Mosquito Flight Paths in Relation to the Environment. Effect of Vertical and Horizontal Visual Barriers

The non-migratory flight behavior of An. crucians, An. quadrimaculatus, Ae. vexans, Coq. perturbans, C. nigripalpus, Cs. melanura, P. confinnis, and other species was studied in Central Florida. Frame and webbing barriers were placed on opposite sides of suction traps to simulate a trap located in a hedge. While appearing solid, open spaces between the strands of webbing permitted mosquito flight. Suction trap collections were also made beneath a 30 ft × 30 ft horizontal net of webbing that reduced light intensities by 80%. In a field location, nearly all species were taken in 2-3X greater numbers in traps equipped with vertical barriers than in traps without barriers. When the experiment was repeated in a wooded swamp possessing an understory of shrubs and ferns, traps with barriers failed to take larger numbers of any species except Cs. melanura. Raising the height of the vertical barriers on traps located in the field by 1 ft reduced their effectiveness. All species, Cs. melanura and C. salinarius excepted, were taken in reduced numbers in traps beneath the horizontal nets. During full moon periods, the response of mosquitoes to all barriers was reduced. The differing levels of response to the experimental conditions by various species are interpreted in relation to their normal flight habitats, visual perception, light intensities, and probable mode of response.

Doses Behind Vertical and Horizontal Barriers from a Plane Source of 1.25 MeV Gamma-Ray Photon

Calculations were performed by the Monte Carlo method to determine the dose at various detector locations behind a vertical barrier and below an adjacent horizontal barrier. Results were obtained, using two different Monte Carlo approaches, for a 1.25-MeV simulated ground source incident on 60, 40, and 20 psf of concrete. The results of the Monte Carlo calculations were used to calculate reduction factors. The above-ground reduction factors compared with those of Spencer to within 10%. The below-ground reduction factors were compared with those calculated from the OCD Engineering Manual, and the agreement in this case was found to be unsatisfactory. In some instances, discrepancies were found to be as high as a factor of 3. For the case of the open basement, agreement among the three methods was found to lie within 10 to 20%. The results obtained by the two Monte Carlo methods used were found to be in excellent agreement. These results also compared to within 10 to 15% with results of experiments performed at Technical Operations Research. The results indicate that further investigation is necessary to determine the amount of scattered radiation within a basement.

A theoretical and experimental investigation of the effects of horizontal barriers in thermal diffusion columns

AbstractA theoretical and experimental investigation of the effects of horizontal barriers on the separation of binary mixtures attained in thermogravitational thermal diffusion columns was undertaken in an attempt to further the understanding of these effects. The presence of horizontal barriers serves to reduce the internal convective flow and to divide tht column into a number of smaller columns with interconnecting end feeds. Equations developed from such a model serve to predict the effect of the number of barriers, temperature difference, barrier diameter, and other parameters on the steady state and transient behavior of a batch column and on the manner in which bulk flow through the column influences the steady state separation in continuous‐flow columns.Data were taken in both batch and continuous columns to test the theory. Parameters varied experimentally (with an ethanol‐water system) were number of barriers, (N = 0, 2, 4, 8, 16, 50), temperature difference, and diameter of the cylindrical barriers. It was found that the theoretical developments were entirely adequate to explain the observed influence of number of barriers for both types of column operation. The slight dependence of steady state batch separation on temperature difference that was observed is consistent with data of other investigations, and the independence of this type of separation on barrier diameter is in agreement with theoretical predictions. The theoretical predictions with respect to changes in temperature difference and a semitheoretical analysis of the effect of barrier diameter making use of isothermal hydrodynamic determinations proved satisfactory in predicting the influence of changes in these two parameters on both the transient batch and steady state continuous‐flow column operation.

Horizontal Barriers for Controlling Water Coning

Abstract This paper considers, from an engineering viewpoint, several factors involved in creating, designing and locating horizontal barriers for controlling water coning. This is an effort to consolidate new concepts with previous in formation so that a reasonable selection of barrier materials, dimensions and vertical position can be made. Coning theories previously developed are briefly reviewed and an effort is made to reduce the results of coning-theory calculations to a point where routine calculations can be made with a desk calculator. It is expected that these simplified calculations will give usable predictions of the amounts of improvement attainable with barriers of various dimensions. Apparatus and procedures used for testing the suitability of commercial cements are described and test results are presented. Introduction Just about as soon as the phenomenon of water coning was recognized as an oilfield problem, there were suggestions that the production of water coning could be controlled or completely suppressed by means of horizontal barriers. It was also suggested that natural barriers such as shale streaks were helpful in restricting bottom-water production. The implication was that wells not having the benefit of continuous shale streaks to suppress bottom waters should, in some way, be supplied with an artificial barrier. With regard to the selection of barrier materials, there are many references which give the merits of liquid barriers. These liquids include surface-active agents, precipitates and emulsions. There is no real need to review the merits of these materials again. This paper deals with the use of solid barriers which could be made from various cements. The two major restrictions placed on these barrier cements are thatthey must be commercially available in large quantities, andthey must be applicable by means of standard tools and equipment with techniques that have been fully developed and are in general use at the present time. THEORY AND DEFINITIONS A schematic drawing of a horizontal barrier in a reservoir is shown in Fig. 1. Two maximum stable water cones are illustrated--one for the wellbore diameter and the other for a barrier. A maximum stable cone is one that has attained its maximum volume at the critical production rate and is on the threshold of producing water. The volume displaced by each water cone and the rise in water table are indications of the amount of water-free oil produced. Corrections for porosity, connate water and residual oil, of course, must be applied. The water-oil interface which defines a maximum stable cone is called a free surface. It is a surface over which the pressure is constant. This free surface has the shape of a limiting streamline at and below which there is no movement or transport. The shape of the water cone describes the pressure drop in the reservoir. The effect of a completely impermeable barrier on the cone shape is essentially the same as extending the wellbore out to the barrier radius. The placement of a horizontal barrier requires that a horizontal fracture be created using a single-point entry technique. Two methods may be employed for filling this fracture. One method consists of propping the fracture before filling with cement. JPT P. 783^