Design and Implementation of a CO(2) Flood Utilizing Advanced Reservoir Characterization and Horizontal Injection Wells in Shallow Shelf Carbonate Approaching Waterflood Depletion

The first objective is to utilize reservoir characterization and advanced technologies to optimize the design of a carbon dioxide (CO) project for the South Cowden Unit (SCU) located in Ector County, Texas. The SCU is a mature, relatively small, shallow shelf carbonate unit nearing waterflood depletion. The second objective is to demonstrate the performance and economic viability of the project in the field. All work this quarter falls within the demonstration project

Design and implementation of a CO{sub 2} flood utilizing advanced reservoir characterization and horizontal injection wells in a shallow shelf carbonate approaching waterflood depletion. Annual report, July 1, 1996--June 30, 1997

The work reported herein covers select tasks in Budget Phase 2. The principle Task in Budget Phase 2 included in this report is Field Demonstration. Completion of many of the Field Demonstration tasks during the last report period enabled an optimum carbon dioxide (CO{sub 2}) flood project to be designed, economically evaluated, and implemented in the field. Field implementation of the project commenced during late 1995, with actual CO{sub 2} injection commencing in mid-July, 1996. This report summarizes activities incurred following initial project start-up, towards the goal of optimizing project performance. The current project has focused on reducing initial investment cost by utilizing horizontal injection wells and concentrating the project in the best productivity area of the field. An innovative CO{sub 2} purchase agreement (no take-or-pay provisions, CO{sub 2} purchase price tied to West Texas Intermediate (WTI) crude oil price) and gas recycle agreement (expensing costs as opposed to a large upfront capital investment for compression) were negotiated to further improve the project economics

Macrophyte abundance in Waquoit Bay : effects of land-derived nitrogen loads on seasonal and multi-year biomass patterns

Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Estuaries and Coasts 31 (2008): 532-541, doi:10.1007/s12237-008-9039-6.Anthropogenic inputs of nutrients to coastal waters have rapidly restructured coastal ecosystems. To examine the response of macrophyte communities to land-derived nitrogen loading, we measured macrophyte biomass monthly for six years in three estuaries subject to different nitrogen loads owing to different land uses on the watersheds. The set of estuaries sampled had nitrogen loads over the broad range of 12 to 601 kg N ha-1 y-1. Macrophyte biomass increased as nitrogen loads increased, but the response of individual taxa varied. Specifically, biomass of Cladophora vagabunda and Gracilaria tikvahiae increased significantly as nitrogen loads increased. The biomass of other macroalgal taxa tended to decrease with increasing load, and the relative proportion of these taxa to total macrophyte biomass also decreased. The seagrass, Zostera marina, disappeared from the higher loaded estuaries, but remained abundant in the estuary with the lowest load. Seasonal changes in macroalgal standing stock were also affected by nitrogen load, with larger fluctuations in biomass across the year and higher minimum biomass of macroalgae in the higher loaded estuaries. There were no significant changes in macrophyte biomass over the six years of this study, but there was a slight trend of increasing macroalgal biomass in the latter years. Macroalgal biomass was not related to irradiance or temperature, but Z. marina biomass was highest during the summer months when light and temperatures peak. Irradiance might, however, be a secondary limiting factor controlling macroalgal biomass in the higher loaded estuaries by restricting the depth of the macroalgal canopy. The relationship between the bloom-forming macroalgal species, C. vagabunda and G. tikvahiae, and nitrogen loads suggested a strong connection between development on watersheds and macroalgal blooms and loss of seagrasses. The influence of watershed land uses largely overwhelmed seasonal and inter-annual differences in standing stock of macrophytes in these temperate estuaries.This research was supported by the National Oceanic and Atmospheric Administration (NOAA), Cooperative Institute for Coastal and Estuarine Environmental Technologies (CICEET-UNH#99-304, NOAA NA87OR512), NOAA National Estuarine Research Reserve Graduate Research Fellowship NERRS GRF, #NA77OR0228), and an Environmental Protection Agency (EPA) STAR Fellowship for Graduate Environmental Study (U-915335-01-0) awarded to J. Hauxwell. S. Fox was supported by a NOAA NERRS GRF (#NA03NOS4200132) and an EPA STAR Graduate Research Fellowship. We also thank the Quebec-Labrador Foundation Atlantic Center for the Environment's Sounds Conservancy Program and the Boston University Ablon/Bay Committee for their awarding research funds

Leaf nutrients, not specific leaf area, are consistent indicators of elevated nutrient inputs

Leaf traits are frequently measured in ecology to provide a ‘common currency’ for predicting how anthropogenic pressures impact ecosystem function. Here, we test whether leaf traits consistently respond to experimental treatments across 27 globally distributed grassland sites across 4 continents. We find that specific leaf area (leaf area per unit mass)—a commonly measured morphological trait inferring shifts between plant growth strategies—did not respond to up to four years of soil nutrient additions. Leaf nitrogen, phosphorus and potassium concentrations increased in response to the addition of each respective soil nutrient. We found few significant changes in leaf traits when vertebrate herbivores were excluded in the short-term. Leaf nitrogen and potassium concentrations were positively correlated with species turnover, suggesting that interspecific trait variation was a significant predictor of leaf nitrogen and potassium, but not of leaf phosphorus concentration. Climatic conditions and pretreatment soil nutrient levels also accounted for significant amounts of variation in the leaf traits measured. Overall, we find that leaf morphological traits, such as specific leaf area, are not appropriate indicators of plant response to anthropogenic perturbations in grasslands

Design and implementation of a CO{sub 2} flood utilizing advanced reservoir characterization and horizontal injection wells in a shallow shelf carbonate approaching waterflood depletion. Annual report, July 1, 1996--June 30, 1997

The work reported herein covers select tasks in Budget Phase 2. The principle Task in Budget Phase 2 included in this report is Field Demonstration. Completion of many of the Field Demonstration tasks during the last report period enabled an optimum carbon dioxide (CO{sub 2}) flood project to be designed, economically evaluated, and implemented in the field. Field implementation of the project commenced during late 1995, with actual CO{sub 2} injection commencing in mid-July, 1996. This report summarizes activities incurred following initial project start-up, towards the goal of optimizing project performance. The current project has focused on reducing initial investment cost by utilizing horizontal injection wells and concentrating the project in the best productivity area of the field. An innovative CO{sub 2} purchase agreement (no take-or-pay provisions, CO{sub 2} purchase price tied to West Texas Intermediate (WTI) crude oil price) and gas recycle agreement (expensing costs as opposed to a large upfront capital investment for compression) were negotiated to further improve the project economics

DESIGN AND IMPLEMENTATION OF A CO2 FLOOD UTILIZING ADVANCED RESERVOIR CHARACTERIZATION AND HORIZONTAL INJECTION WELLS IN A SHALLOW SHELF CARBONATE APPROACHING WATERFLOOD DEPLETION

The purpose of this project was to economically design an optimum carbon dioxide (CO{sub 2}) flood for a mature waterflood nearing its economic abandonment. The original project utilized advanced reservoir characterization and CO{sub 2} horizontal injection wells as the primary methods to redevelop the South Cowden Unit (SCU). The development plans; project implementation and reservoir management techniques were to be transferred to the public domain to assist in preventing premature abandonment of similar fields. The Unit was a mature waterflood with water cut exceeding 95%. Oil must be mobilized through the use of a miscible or near-miscible fluid to recover significant additional reserves. Also, because the unit was relatively small, it did not have the benefit of economies of scale inherent in normal larger scale projects. Thus, new and innovative methods were required to reduce investment and operating costs. Two primary methods used to accomplish improved economics were use of reservoir characterization to restrict the flood to the higher quality rock in the unit and use of horizontal injection wells to cut investment and operating costs. The project consisted of two budget phases. Budget Phase I started in June 1994 and ended late June 1996. In this phase Reservoir Analysis, Characterization Tasks and Advanced Technology Definition Tasks were completed. Completion enabled the project to be designed, evaluated, and an Authority for Expenditure (AFE) for project implementation submitted to working interest owners for approval. Budget Phase II consisted of the implementation and execution of the project in the field. Phase II was completed in July 2001. Performance monitoring, during Phase II, by mid 1998 identified the majority of producing wells which under performed their anticipated withdrawal rates. Newly drilled and re-activated wells had lower offtake rates than originally forecasted. As a result of poor offtake, higher reservoir pressure was a concern for the project as it limited CO{sub 2} injectivity. To reduce voidage balance, and reservoir pressure, a disposal well was therefore drilled. Several injection surveys indicated the CO{sub 2} injection wells had severe conformance issues. After close monitoring of the project to the end of 1999, it was evident the project would not recover the anticipated tertiary reserves. The main reasons for under-performance were poor in zone CO{sub 2} injection into the upper San Andres layers, poorer offtake rates from newly drilled replacement wells and a higher than required reservoir pressure. After discussion internally within Phillips, externally with the Department of Energy (DOE) and SCU partners, a redevelopment of South Cowden was agreed upon to commence in year 2000. The redevelopment essentially abandoned the original development for Budget Phase II in favor of a revised approach. This involved conformance techniques to resolve out of zone CO{sub 2} injection and use of horizontal wells to improve in zone injectivity and productivity. A phased approach was used to ensure short radius lateral drilling could be implemented effectively at South Cowden. This involved monitoring drilling operations and then production response to determine if larger investments during the second phase were justified. Redevelopment Phase 1 was completed in May 2000. It was deemed a success in regard to finding suitable/cost-effective technology for drilling horizontal laterals and finding a technique that could sustain long-term productivity from the upper layers of the San Andres reservoir. Four existing vertical producing wells were isolated from their existing completions and sidetracked with horizontal laterals into the upper layers of the San Andres. Overall average offtake rates for the four wells increased by a factor of 12 during the first four months after completion of Phase 1. Phase 2 of the redevelopment focused on current CO{sub 2} vertical injection wells. Techniques were applied to resolve near well conformance concerns and then either single or dual laterals were drilled in the upper layers. Additional work required conformance resolution with a horizontal injection well and additional lateral drilling from four existing producing wells. Although Phase 1 had provided a short-term boost to lease offtake, it was Phase 2, by ensuring in zone CO{sub 2} injection in all existing vertical wells, which would provide the longer-term reserve recovery from the upper San Andres. Phase 2 activities commenced in October 2000 with drilling a single lateral in an existing CO{sub 2} injector. Four dual lateral and one single lateral CO{sub 2} injection wells were completed from existing wellbores to replace the poorly performing CO{sub 2} vertical injection wells. Four additional single laterals from existing vertical production wells were also completed. Phase 2 was completed in April 2001

Increasing effects of chronic nutrient enrichment on plant diversity loss and ecosystem productivity over time

Human activities are enriching many of Earth’s ecosystems with biologically limiting mineral nutrients such as nitrogen (N) and phosphorus (P). In grasslands, this enrichment generally reduces plant diversity and increases productivity. The widely demonstrated positive effect of diversity on productivity suggests a potential negative feedback, whereby nutrient-induced declines in diversity reduce the initial gains in productivity arising from nutrient enrichment. In addition, plant productivity and diversity can be inhibited by accumulations of dead biomass, which may be altered by nutrient enrichment. Over longer time frames, nutrient addition may increase soil fertility by increasing soil organic matter and nutrient pools. We examined the effects of 5–11 yr of nutrient addition at 47 grasslands in 12 countries. Nutrient enrichment increased aboveground live biomass and reduced plant diversity at nearly all sites, and these effects became stronger over time. We did not find evidence that nutrient-induced losses of diversity reduced the positive effects of nutrients on biomass; however, nutrient effects on live biomass increased more slowly at sites where litter was also increasing, regardless of plant diversity. This work suggests that short-term experiments may underestimate the long term nutrient enrichment effects on global grassland ecosystems.DATA AVAILABILITY: Data are publicly available on the Environmental Data Initiative platform (Seabloom et al. 2020 https://doi.org/10.6073/pasta/d78e6e48df246a03129c85a6c1da00d6).National Science Foundation Research Coordination Network programs and University of Minnesota’s Institute on the Environment (DG-0001-13).http://www.esajournals.org/loi/ecolpm2021Mammal Research InstituteZoology and Entomolog

Temporal rarity is a better predictor of local extinction risk than spatial rarity

Spatial rarity is often used to predict extinction risk, but rarity can also occur temporally. Perhaps more relevant in the context of global change is whether a species is core to a community (persistent) or transient (intermittently present), with transient species often susceptible to human activities that reduce niche space. Using 5–12 yr of data on 1,447 plant species from 49 grasslands on five continents, we show that local abundance and species persistence under ambient conditions are both effective predictors of local extinction risk following experimental exclusion of grazers or addition of nutrients; persistence was a more powerful predictor than local abundance. While perturbations increased the risk of exclusion for low persistence and abundance species, transient but abundant species were also highly likely to be excluded from a perturbed plot relative to ambient conditions. Moreover, low persistence and low abundance species that were not excluded from perturbed plots tended to have a modest increase in abundance following perturbance. Last, even core species with high abundances had large decreases in persistence and increased losses in perturbed plots, threatening the long-term stability of these grasslands. Our results demonstrate that expanding the concept of rarity to include temporal dynamics, in addition to local abundance, more effectively predicts extinction risk in response to environmental change than either rarity axis predicts alone