Hydrologic Characterization of the Saline Frio Formation, Victoria County, Texas Gulf Coast: A Case Study

Pressure data gathered from drillstem tests (DSTs) and bottomhole pressure measurements in onshore oil and gas wells along the Texas Gulf Coast were used for evaluating pressure regimes and their influence on the migration potential of formation fluids. The data were used to construct potentiometric surfaces and residual potential surfaces and to assess the effects of depressurization caused by hydrocarbon production. This technique was utilized for preliminary geohydrologic characterization of the Frio Formation of the Texas Gulf Coast. Included in this report are the results of such an analysis for Victoria County, Texas, as a sample case study. Pressure data were evaluated for reliability, and a screening and classification system was applied to closely monitor the quality of data used for generating potentiometric surfaces. Preceding the hydrologic analysis, steps were taken to review the available geologic information in the context of Tertiary Texas Gulf Coast formations. An evaluation of the regional pressure-depth plots reveals multiple overlapping pressure regimes. Also indicated is an area of extensive depressurization attributable to hydrocarbon production. The potentiometric surfaces also reflect depressurization that results in local variations in flow directions and a general trend of flow toward the oil and gas fields. Potentiometric surfaces for the deeper sections of the Frio reflect the high equivalent hydraulic heads in the geopressured region.Bureau of Economic Geolog

HYTESS: A hypothetical turbofan engine simplified simulation

A users manual for a hypothetical turbofan engine simplified simulation is presented. This digital simulation exists as FORTRAN source code. The program is self-contained and was developed to offer those interested in engine dynamics and controls research an efficient, realistic, and easily used engine simulation. The engine is modeled using a state space formulation. Matrix elements within the linear state space structure are nonlinear functions of various engine variables

Abandoned Well Characterization: A Methodology to Evaluate Regional Hydraulic Controls on Flow From Hydrocarbon Reservoirs into Underground Sources of Drinking Water

Between 1859 and 1990, approximately 3.3 million wells for oil and gas exploration and production were drilled in the U.S., of which nearly 2.4 million have been shut-in, temporarily abandoned, or plugged and abandoned (World Oil, 1992). Several major petroleum basins in the country contain large populations of these wells. Because drilling, completion, and abandonment practices for wells have evolved over the years, older wells that were found to be unproductive (or dry), or which had to be permanently shut-in for mechanical problems or economic reasons, may not have been adequately plugged according to modern standards or regulations. In some instances, upward movement of saltwater in such abandoned wells may pose a risk of contamination to underground sources of drinking water (USDWs). Three main conditions must exist for contamination of a USDW to occur by fluid migration from an oil and gas production zone or a waste disposal zone: (1) presence of a USDW overlying the zone; (2) presence of unplugged or inadequately plugged abandoned wells (or natural geologic pathways) that penetrate both a production or disposal zone and a USDW; and (3) an upward-directed hydraulic gradient between the zone of interest and the USDW. The first condition exists in many of the petroleum-producing areas in the U.S. However, the second and third conditions may or may not occur. In particular, the third condition depends in part upon the changes in pressure due to fluid withdrawal and injection associated with enhanced recovery or salt-water disposal (Class II wells).Bureau of Economic Geolog

Sciatic Nerve Cut and Repair Using Fibrin Glue in Adult Mice

Peripheral nerve injury (PNI) is an excellent model for studying neural responses to injury and elucidating the mechanisms that can facilitate axon regeneration. As such, several animal models have been employed to study regenerative mechanisms after PNI, including Aplysia, zebrafish, rabbits, cats and rodents. This protocol describes how to perform a sciatic nerve injury and repair in mice, one of the most frequently used models to study mechanisms that facilitate recovery after PNI, and that takes advantage of the availability of many genetic models. In this protocol, we describe a method for using fibrin glue to secure the proximal and distal stumps of an injured nerve in close alignment. This method facilitates the alignment of nerve stumps, which aids in regeneration of both sensory and motor axons and allows successful reconnection with peripheral targets

Hydrogeology of Formations Used for Deep-Well Injection, Texas Gulf Coast

This research program was conducted to investigate fluid migration potential, fluid direction, and velocities in the regional hydrologic environment of the Texas Gulf Coast Tertiary formations in the context of deep-well injection of hazardous chemical wastes. The study focused on the Frio Formation due to its significant waste injection and the availability of a large database on formation pressures and water chemistry in the Frio. Pressure data collected from drill-stem tests and bottomhole pressure measurements in onshore oil and gas wells were used to evaluate pressure regimes. Pressure-depth profiles and potentiometric surfaces constructed from this data revealed three hydrologic regimes: a shallow section with fresh to moderately saline water in the upper 3,000-4,000 ft, an essentially saline hydrostatic section 4,000-5,000 ft thick, and a deeper overpressured section with moderate to high salinities. The hydrologic complexity is further compounded by extensive depressurization in the 4,000-8,000 ft depth interval, likely resulting from the production of over 10 billion barrels of oil equivalent and associated brines over the past 50 years. It was not possible to construct a composite potentiometric surface of the entire Frio to determine "natural" flow gradients or "natural" points of discharge. Potentiometric surfaces representing discrete depth intervals were mapped, and these values, along with flow gradients determined from potentiometric surfaces and published permeability and porosity data, were used to compute linear fluid flow velocities ranging from 0.01 ft/year to 105 ft/year in the lateral direction. The potential for vertical fluid migration was investigated using equivalent environmental hydraulic head maps. The presence of widespread pockets of depressured formations significantly affects the direction and value of fluid gradients, as these depressured oil and gas fields may become potential sinks for the injected chemical wastes. Published water chemistry data were supplemented by field sampling of waters from 32 oil fields. Active recharge of the Frio by continental waters does not seem to be occurring. All sampled waters appear to be in isotopic equilibrium with the rock matrix. Salt dome dissolution is the primary reaction controlling water chemistry in the northern section, while brines from the deeper geopressured section may be leaking into the hydrostatic section of the central and southern Gulf Coast Frio. The absence of organic acids and the alteration of Frio oils from samples shallower than approximately 7,000 ft suggest biodegradation, which has useful implications for the degradation of injected chemical wastes. A detailed analysis of the localized hydrodynamics in Victoria County, Texas, as a case study demonstrates the applicability of the developed techniques to injection facility siting and monitoring processes, particularly where depressurization was observed on a local, county-size scale.Bureau of Economic Geolog

High food prices: The what, who, and how of proposed policy actions

"The complex causes of the current food and agriculture crisis require a comprehensive response. In view of the urgency of assisting people and countries in need, the first set of policy actions— an emergency package—consists of steps that can yield immediate impact: 1. expand emergency responses and humanitarian assistance to food-insecure people and people threatening government legitimacy, 2. eliminate agricultural export bans and export restrictions, 3. undertake fast-impact food production programs in key areas, and 4. change biofuel policies. A second set of actions—a resilience package—consists of the following steps: 5. calm markets with the use of market-oriented regulation of speculation, shared public grain stocks, strengthened food-import financing, and reliable food aid; 6. invest in social protection; 7. scale up investments for sustained agricultural growth; and 8. complete the Doha Round of World Trade Organization (WTO) negotiations. Investment in these actions calls for additional resources. Policymakers should consider mobilizing resources from four sources: the winners from the commodity boom among countries; the community of traditional and new donor countries; direct or indirect progressive taxation and reallocation of public expenditures in the affected countries themselves; and mobilization of private sector finance, including through improved outreach of banking to agriculture. Because of countries' diverse situations, the design of programs must be country driven and country owned. Accountability for sound implementation must also rest with countries. At the same time, a new international architecture for the governance of agriculture, food, and nutrition is needed to effectively implement the initiatives described, and especially their international public goods components. Global and national action is needed, through existing mechanisms, well-coordinated special initiatives, and possibly a special fund." from TextFood prices, Food supply, Food demand, Social protection, Agricultural research, Agricultural policy, Agricultural subsidies,

Consolidation of Geologic Studies of Geopressured Geothermal Resources in Texas

The objective of the current studies at the Pleasant Bayou geopressured geothermal reservoir in Brazoria County, Texas, was to evaluate the resource base and long-term performance. The approach was to develop an integrated understanding of the hydrogeology of the reservoir and the hydrochemistry of the produced brine. Such an understanding would allow determination of the extent of lateral and vertical hydrologic continuity of the target zone and to identify the sources of brine being produced from the geopressured reservoir. The current phase of long-term production testing of the Frio C-zone at Pleasant Bayou Well No. 2 began in May 1988. During the past 16 months of production, nearly 6.8 million barrels of brine and 162.2 million cubic feet of gas have been produced, and a relatively small (less than 300 psi) drop in bottom-hole pressure has been observed at sustained producing rates of between 15,000 and 20,000 barrels per day. Earlier geologic studies have estimated the effective pore volume of the C-zone in the neighborhood of 6.2 to 6.6 billion barrels. Analysis of pressure and production data from current testing indicates that the limits of the geopressured reservoir at Pleasant Bayou have not been reached; that is, either the size of the reservoir could be larger than anticipated, or there could be a continuous influx of waters from other geopressured sources that sustains the reservoir energy at Pleasant Bayou. Geochemical testing has proved inconclusive in identifying other sources of water partly because of the variability of chemical composition within the produced zone. Evaluation of reservoir performance at active oil and gas fields in the immediate vicinity of the Pleasant Bayou fault block has not provided evidence of direct hydrologic communication between the geopressured aquifer and the overlying hydrocarbon reservoirs. The pattern of depletion in these oil and gas fields reflects some characteristic features that may become evident in Pleasant Bayou over a long period of production. Moreover, additional refinement of the integrated hydrogeologic-hydrochemical model is possible either through prolonged testing at Pleasant Bayou No. 2 well or through drilling and testing of additional wells in the Pleasant Bayou fault block. Determining the nature of bounding faults around the test well will require additional seismic data as well as multiwell testing of the reservoir.Bureau of Economic Geolog