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

Surface Water Hydrology of the Proposed Low-Level Radioactive Waste Isolation Site, Hudspeth County, Texas

This report describes the surface-water hydrology at the proposed low-level radioactive waste isolation site in Hudspeth County, Texas. The objective of these investigations was to evaluate the flooding potential at the site based on computer simulation of runoff from observed and hypothetical rain events. Analytic techniques and assumptions used in this study are based on recommendations of federal and state regulatory agencies regarding flood insurance and dam safety criteria. Published topographic maps, aerial photographs, and site surveys were used for delineating drainage basins and surface-water pathways on the study area. Surface-water runoff volumes were calculated for rain events monitored at the site during the study period. Hydrologic computer models were employed to determine correlation of rainfall to surface-water runoff. These computer models were calibrated using rainfall and stream-flow data measured at the site. Flood profiles were calculated for 100-yr and probable maximum rain events, which were estimated from historical data. The following conclusions regarding the flooding potential at the study area were drawn on the basis of these studies: (1) Computer simulation indicates that floods resulting from hypothetical 100-yr and probable maximum precipitation events are contained within existing channels in the study area, leaving large interchannel areas unflooded. Some overland sheet flow is encountered over the flat area, but the velocities of flow are very small. (2) Rainfall events recorded during the 1988-1989 period were short and localized. The response of runoff to rainfall is rapid and the duration of the peak water flow after rainfall is relatively short. (3) Flow velocities range from 3 to 13 ft/sec (0.9 to 4 m/sec) in channels and are lower over flat areas. Maximum depth of flow due to a 100-yr flood in the better-defined channel on the central part of the study area is about 5 ft (1.5 m).Bureau of Economic Geolog

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

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

Bioassay of insecticides against three honey bee species in laboratory conditions

A study was conducted at the Eco-toxicology laboratory in the Department of Agricultural Entomology, University of Agriculture Faisalabad, against three species Apis florea, A. dorsata and A. mellifera of honey bees, to check long-term survival of honeybees when exposed to different insecticides. In this study, we used a modeling approach regarding survival data of caged bees under chronic exposure to seven insecticides (Carbosulfan, Chlorpyrifos, Bifenthrin, Spinosad, Indoxacarb, Emamectin benzoate and Imidacloprid), having three replicates and four concentrations (1000, 500, 250, 125 and 0 ppm). We demonstrate the chronic toxicity induced by these insecticides. Laboratory bioassay of these insecticides showed that carbosulfan and imidacloprid were the most toxic at their high dose (1000 ppm) with LT50 of 4 hours in each case for A. mellifera, chlorpyrifos and imidacloprid were the most toxic at their high dose (1000 ppm) with LT50 of 5 hours in each case for A. florea whereas chlorpyrifos was the most toxic at high dose (1000 ppm) with LT50 of 5 hours for A. dorsata. However, LT50 of spinosad was increased up to 18 hrs with decreasing concentrations at 125 ppm against A. mellifera, LT50 of spinosad was increased up to 15 hrs with decreasing concentrations at 125 ppm against A. florea as well as LT50 of spinosad and Emamectin benzoate was increased up to 20 hrs with decreasing concentrations at 125 ppm against A. dorsata. However, LT50 of all controlled species was 91-103 hrs

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

Careers work in higher education in Pakistan: current practice and options for the future

In this article we examine the development of career guidance in Pakistani higher education. The article is primarily based on a review of the existing literature on career guidance in Pakistan, but also includes the consideration of some new data gathered from a review of higher education institutions websites and five case study interviews. It considers both local and global influences as relevant contexts for understanding how the development of career guidance in Pakistani higher education is taking place. Concerns about alignment between skills supply and demand provide key drivers both for the development of career guidance and for wider higher education reform. However the practice of career guidance in Pakistani higher education is shown to be lagging behind the policy aspirations, both due to limited investment and due to more fundamental cultural challenges that have yet to be fully addressed. If career guidance is going to continue to develop within Pakistan it will need to be strengthened by new policy and resources but also through the development of indigenous theories.N/

Global overview of the management of acute cholecystitis during the COVID-19 pandemic (CHOLECOVID study)

Background: This study provides a global overview of the management of patients with acute cholecystitis during the initial phase of the COVID-19 pandemic. Methods: CHOLECOVID is an international, multicentre, observational comparative study of patients admitted to hospital with acute cholecystitis during the COVID-19 pandemic. Data on management were collected for a 2-month study interval coincident with the WHO declaration of the SARS-CoV-2 pandemic and compared with an equivalent pre-pandemic time interval. Mediation analysis examined the influence of SARS-COV-2 infection on 30-day mortality. Results: This study collected data on 9783 patients with acute cholecystitis admitted to 247 hospitals across the world. The pandemic was associated with reduced availability of surgical workforce and operating facilities globally, a significant shift to worse severity of disease, and increased use of conservative management. There was a reduction (both absolute and proportionate) in the number of patients undergoing cholecystectomy from 3095 patients (56.2 per cent) pre-pandemic to 1998 patients (46.2 per cent) during the pandemic but there was no difference in 30-day all-cause mortality after cholecystectomy comparing the pre-pandemic interval with the pandemic (13 patients (0.4 per cent) pre-pandemic to 13 patients (0.6 per cent) pandemic; P = 0.355). In mediation analysis, an admission with acute cholecystitis during the pandemic was associated with a non-significant increased risk of death (OR 1.29, 95 per cent c.i. 0.93 to 1.79, P = 0.121). Conclusion: CHOLECOVID provides a unique overview of the treatment of patients with cholecystitis across the globe during the first months of the SARS-CoV-2 pandemic. The study highlights the need for system resilience in retention of elective surgical activity. Cholecystectomy was associated with a low risk of mortality and deferral of treatment results in an increase in avoidable morbidity that represents the non-COVID cost of this pandemic

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks