Robert J. Finley

WIND-GENERATED LONGSHORE CURRENTS

The equations describing conservation of mass, momentum and energy in a turbulent free surface flow are derived for a controle volume extending over the whole depth. The effect of the turbulent surface oscillations are discussed but neglected in the following analysis, where the equations are applied to the energy balance in a surf zone wave motion. This leads to results for the wave height variation and the velocity of propagation. The results cannot be reconciled completely with measurements and the concluding discussion is aimed at revealing how the model can be improved.A three-dimensional morphodynamic model of sequential beach changes Is presented. The model Is based on variations in breaker wave power generating a predictable sequence of beach conditions. The spectrum of beach conditions from fully eroded-dissipatlve to fully accreted reflective is characterised by ten beach-stages. Using the breaker wave power to beach-stage relationship the model Is applied to explain temporal, spatial and global variations In beach morphodynamlcs.The agents of initial damage to the dunes are water, which undermines them, and animals (including man) which damage the protective vegetation by grazing or trampling. Of these, man has recently assumed predominant local importance because of the popularity of sea-side holidays and of the land-falls of certain marine engineering works such as oil and gas pipelines and sewage outfalls. The need is therefore increasing for active dune management programmes to ensure that under these accentuated pressures, the coast retain an equilibrium comparable with that delicately balanced equilibrium which obtains naturally at a particular location.

Interpretation of surface-water circulation, Aransas Pass, Texas, using landsat imagery

Abstract The development of plumes of turbid surface water in the vicinity of Aransas Pass, Texas has been analyzed using Landsat imagery. The shape and extent of plumes present in the Gulf of Mexico is dependent on the wind regime and astronomical tide prior to and at the time of satellite overpass. The best developed plumes are evident when brisk northerly winds resuspend bay-bottom muds and flow through Aransas Pass is increased by wind stress. Seaward diversion of nearshore waters by the inlet jetties was also observed. A knowledge of surface-water circulation through Aransas Pass under various wind conditions is potentially valuable for monitoring suspended and surface pollutants.

Reservoir Architecture--A Critical Element in Extended Conventional Recovery of Mobile Oil in Heterogeneous Reservoirs: ABSTRACT

Sedimentological research during the last 20 years has defined models that support exploration and therefore focus on external geometry of reservoirs. These models understate the importance of the internal reservoir framework and are inadequate to explain internal reservoir seals and resultant compartmentalization as it controls hydrocarbon recovery. Development of models describing internal reservoir architecture, that is, facies composition, extents, three-dimensional geometries, orientations, and relations with surrounding facies, is critical for guiding well placement and completion interval to maximize hydrocarbon recovery from heterogeneous reservoirs. Reservoir architecture, a product of sedimentation style, governs mobile oil recovery efficiency. Wave-reworked depositional systems with simple architectures have high mobile oil recovery efficiencies. In contrast, strongly channelized systems with complex architectures, including fluvial, fluvial-dominated deltaic, and submarine fan reservoirs, have low to moderate mobile oil recovery. Carbonate reservoirs display a smaller range of mobile oil recovery efficiencies; however, large volumes of unrecovered mobile oil remain in highly stratified, laterally discontinuous platform carbonates in the Permian basin. In Texas reservoirs with complex architectures, 35 billion bbl of mobile oil will remain unrecovered at abandonment; nationally, this important and moderate-cost resource may be 80 to 100 billion bbl.

Depositional Systems and Productive Characteristics of Major Low-Permeability Gas Sandstones in Texas: ABSTRACT

Major tight gas sandstones in Texas range from lenticular to blanket geometry, from hydropressured to geopressured, and from Pennsylvanian to Eocene in age. The Cotton Valley sandstone (East Texas basin) includes barrier- and marine-bar sandstones (blanket) derived from prograding fan deltas with associated braided stream, delta-front, and pro-delta deposits. The overlying Travis Peak Formation contains a lower deltaic facies, a middle, dominantly braided fluvial facies (broadly lenticular), and an upper transgressive clastic-to-carbonate transition. Estimated gas in place varies from 53 tcf (Cotton Valley) to 25 tcf (Travis Peak); most wells initially produce from 500 to 1,500 mcf and few wells produce 2,500 mcf. Tight gas sandstones in the Wilcox and Vicksburg Groups (G lf Coast basin) are mostly geopressured delta-front, shelf, and slope deposits. These lenticular sandstones isolated in shale have pressure gradients up to 0.81 psi/ft (18.3 kPa/m). Initial well yields are mostly 300 to 2,400 mcfd; resource estimates for tight Wilcox and Vicksburg trends are not available. Canyon Group sandstones of the Sonora basin (parts of the Ozona arch, Concho platform, and Val Verde basin) contain 24 tcf of estimated gas in place and initial flow rates are commonly 100 to 1,000 mcf. These sandstones are broadly lenticular and are interpreted to be submarine fan and possibly shelf-margin deposits. The Olmos Formation (Maverick basin) contains gas within broadly lenticular delta-front deposits of high-constructive delta systems; liquid hydrocarbons in the Olmos are trapped in more proximal facies. Gas in place in the Olmos is estimated to be 5 tcf and initial well yields are 300 to 3,000 mcf. In 1980, 893 wells were completed in formations designated as partially or completely tight by the Railroad Commission of Texas. These completions represent 2.5% of new gas wel s in the state, but 28.0% of those completed in the 5,000 to 15,000-ft depth range in that year. End_of_Article - Last_Page 476------------

AN EVALUATION OF ONGOING CHANGE AFFECTING ENVIRONMENTAL GEOLOGIC MAPPING IN THE TEXAS COASTAL ZONE

Abstract: Although the Texas Coastal Zone, an area of some 51,800 sq km, includes 6 percent of the total area of the state, approximately 34 percent of the states economic resources are found adjacent to the Gulf of Mexico shoreline. This distribution of resources results, in part, from the abundance of hydrocarbon reserves, ground-water supplies, transportation facilities, fish and wildlife resources, and recreational opportunities in a region which includes 5,439 sq km of bays and estuaries. Industrial growth, residential development, agriculture, and other activities continue to increase, and to change the area. In order to evaluate these changes, basic mapping and periodic assessments of the map data are required. The Environmental Geologic Atlas of the Texas Coastal Zone, prepared by the Bureau of Economic Geology, includes environmental geologic maps dependent upon revised U. S. Geological Survey topographic maps, and upon black-and-white photographic mosaics dating from 1956–1959. These environmental geologic maps provide information on substrate materials, geologic processes, botanical zones, and man-made units. Comparison of the gulfward half of each map with 1975 color-infrared aerial photography located 1,105 changes. Nearly one-half of these alterations involved channel dredging and spoil disposal, while other man-induced and natural alterations of coastal ponds and marshlands accounted for 25 percent of the changes. Such results suggest that thorough, detailed mapping, even when based on older photography, provides a viable, open-ended document which can then be supplemented by an evaluation of ongoing change.