Cleanup Period Research Articles

Case History: Lessons Learned From Retrieval of Coiled Tubing Stuck by Massive Hydrate Plug When Well Testing in an Ultradeepwater Gas Well in Mexico

Summary A well-testing operation was performed to confirm productivity potential in an ultradeepwater area where a 5,660-ft exploratory well had been drilled. This was a gas well drilled from a semisubmersible drilling rig. Because well testing from semisubmersible rigs is a critical and sensitive operation, all planning had been carefully reviewed by the operator to ensure a safe, environmentally friendly operation. The formation of hydrate plugs during ultradeepwater well testing is a critical concern because water can be trapped and form a solid crystalline structure around gas when there are low temperatures near the mudline. This hydrate formation is a common occurrence in deepwater drilling operations, particularly while using water-based mud. Thermodynamic inhibition may not be effective in these cases because several limitations in achieving the required injection rate exist. Oilwell testing operations in deep and ultradeep water have become common practice around the world, and vast experience with these types of operations has been acquired; experience with gas wells, however, has not been as comprehensive, and only a few gas wells have been tested under the conditions presented in this type of scenario. Because of the low number of gas wells tested in these deepwater conditions, best-practice information is limited. The intention of this paper is to present a case history and the lessons learned during a well-testing operation in which water production in the gas well was greater than anticipated during the cleanup period. A massive hydrate plug was formed while coiled tubing was being pulled out of hole, and the coiled tubing became stuck. The steps taken to free the coiled tubing will be discussed, and the discussion will include the following: Conditions that must be present to form hydratesHow the problem in this case was resolvedHow to help prevent hydrate formationBest practices for well testing in deepwater gas wells to maintain safety and economic viability This case history discusses a gas well being drilled with a semisubmersible drilling rig in ultradeep water, offshore Mexico.

Establishment and maintenance of a porcine circovirus type 2 (PCV2)-free breeding herd on a site that experienced a natural outbreak of PCV2-associated reproductive disease

An outbreak of reproductive failure associated with porcine circovirus type 2 (PCV2) occurred in a closed, PCV2-naive, specific-pathogen-free herd in Iowa in 2009. Elimination of infectious PCV2 from the breeding-herd site, the outcome after repopulation, and the attempt to derive PCV2-negative animals by offsite segregation are summarized. Clinical signs were limited to an increased incidence of mummified fetuses. After confirmation of PCV2-associated lesions in the fetuses and PCV2 viremia in dams, the herd was depopulated. Cleaning and disinfection of the premises prior to repopulation included removal of gross organic material, exposure of equipment to natural UV light, multiple applications of disinfectant, and application of paint or sealer to porous surfaces. During the 63-day clean-up period, no pigs were on the site. An improved biosecurity plan was implemented. The herd was repopulated and a PCV2-naive population had remained PCV2-negative for 20 months at the time of writing. Attempts to derive PCV2-negative pigs from the positive herd following offsite segregation were unsuccessful. The combination of a multistep cleaning and disinfection protocol with a strict biosecurity plan can result in the maintenance of PCV2-naive animals on a previously contaminated site.

Survival of cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae), through winter cleanups of commercial vegetable greenhouses: Implications for insecticide resistance management

Cabbage looper, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae), is a highly migratory and destructive pest of various crops in North America. Its infestations in vegetable greenhouses in western Canada are generally attributed to annual immigrations from southern overwintering areas, but whether it survives overwinter in western Canada is uncertain. Bioinsecticides based on Bacillus thuringiensis ( Bt) toxins are commonly used in southwestern British Columbia where some T. ni populations have developed strong resistance to Bt-insecticides. In this study, overwintering success of T. ni populations was monitored outside and inside three commercial greenhouses in British Columbia. In both years, T. ni pupae placed outside greenhouses did not survive although pupae placed inside the greenhouses survived the unheated cleanup period and exposure to organophosphate insecticides commonly used in the cleanup procedure in the greenhouses. During the cleanup period, no moths were caught inside the unheated greenhouses, but once the heating was restored for the new growing season, adults were captured in pheromone traps. No developmental stages of T. ni were detected on nursery seedlings and visual monitoring of transplants at the beginning of the season found no signs of previous feeding damage. This strongly suggests that T. ni were not introduced with the seedlings. Our findings are important for understanding the potential risks of inadequate winter cleanup and the potential carryover of resistance to Bt-insecticides in populations from one season to the next that could complicate pest management.

Liquid loading in wellbores and its effect on cleanup period and well productivity in tight gas sand reservoirs

Tight gas reservoirs normally have production problems due to very low matrix permeability and significant damage during well drilling, completion, stimulation and production. Therefore they might not flow gas to surface at optimum rates without advanced production improvement techniques. After well stimulation and fracturing operations, invaded liquids such as filtrate will flow from the reservoir into the wellbore, as gas is produced during well cleanup. In addition, there might be production of condensate with gas. The produced liquids when loaded and re-circulated downhole in wellbores, can significantly reduce the gas production rate and well productivity in tight gas formations. This paper presents assessments of tight gas reservoir productivity issues related to liquid loading in wellbores using numerical simulation of multiphase flow in deviated and horizontal wells. A field example of production logging in a horizontal well is used to verify reliability of the numerical simulation model outputs. Well production performance modelling is also performed to quantitatively evaluate water loading in a typical tight gas well, and test the water unloading techniques that can improve the well productivity. The results indicate the effect of downhole liquid loading on well productivity in tight gas reservoirs. It also shows how well cleanup is sped up with the improved well productivity when downhole circulating liquids are lifted using the proposed methods.

Containment wells to form hydraulic barriers along site boundaries

In the field, aquifer remediation methods include pump and treat procedures based on hydraulic control systems. They are used to reduce the level of residual contamination present in the soil and soil pores of aquifers. Often, physical barriers are erected along the boundaries of the target (aquifer) site to reduce the leakage of the released soil contaminant to the surrounding regions. Physical barriers are expensive to build and dismantle. Alternatively, based on simple hydraulic principles, containment wells or image wells injecting clear water can be designed and built to provide hydraulic barriers along the contaminated site boundaries. For brevity, only one pattern of containment well system that is very effective is presented in detail. The study briefly reports about the method of erecting a hydraulic barrier around a contaminated region based on the simple hydraulic principle of images. During the clean-up period, hydraulic barriers can considerably reduce the leakage of the released contaminant from the target site to surrounding pristine regions. Containment wells facilitate the formation of hydraulic barriers. Hence, they control the movement of contaminants away from the site that is being remedied. However, these wells come into play, only when the pumping operation for cleaning up the site is active. After operation, they can be filled with soil to permit the natural ground water movement. They can also be used as monitoring wells.

Microsatellite mutations show no increases in the children of the Chernobyl liquidators

We performed a study on Belarusian “liquidators”, exploring whether increase in the frequencies of germline mutations at microsatellite loci could be found in their progeny. The liquidators, mostly young males, were those involved (during 1986 and 1987) in clean-up operations in the radioactively contaminated area following the Chernobyl nuclear power plant accident in 1986. Many liquidators fathered children during the clean-up period and after the work had been terminated. The numbers of families studied were 64 (liquidators) and 66 (controls). A total of 72 loci (31 autosomal, one X-linked and 40 Y-linked) were used. DNA was isolated from peripheral blood lymphocytes and the microsatellite loci were amplified by the polymerase chain reaction with fluorescence-labelled primers. Mutations were detected as variations in the length of the loci. At the Y-linked loci, the mutation rates (expressed as number of mutations among the total number of loci for the individuals included) are 2.9 × 10 −3 (4/1392) and 2.1 × 10 −3 (3/1458) in the children of exposed and control parents, respectively. This difference is not statistically significant. At the autosomal loci, the corresponding estimates are 5.9 × 10 −3 (11/1862; exposed group) and 8.5 × 10 −3 (18/2108; control). Again, the difference is not significant. The possibility that the Belarusian population might have been unexpectedly exposed to some chemical contaminants in the environment appears unlikely in view of the finding that the spontaneous mutation rates at the same set of loci in several non-Belarusian populations were similar to those in Belarus. The estimated mean radiation dose to the liquidators was small, being about 39 mSv, and this might be one reason why no increases in mutation rates due to radiation could be found.

Assessing remedial effectiveness through the blood lead:soil/dust lead relationship at the Bunker Hill Superfund Site in the Silver Valley of Idaho

The 21 square mile Bunker Hill Superfund Site in northern Idaho includes several thousand acres of contaminated hillsides and floodplain, a 365-acre abandoned lead/zinc smelter and is home to more than 7000 people in 5 residential communities. Childhood lead poisoning was epidemic in the 1970s with >75% of children exceeding 40 μg/dl blood lead. Health response activities have been ongoing for three decades. In 1991, a blood lead goal of 95% of children with levels less than 10 μg/dl was adopted. The cleanup strategy, based on biokinetic pathways models, was to reduce house dust lead exposure through elimination of soil-borne sources. An interim health intervention program, that included monitoring blood lead and exposures levels, was instituted to reduce exposures through parental education during the cleanup. In 1989 and 2001, 56% and 3% of children, respectively, exceeded the blood lead criteria. More than 4000 paired blood lead/environmental exposure observations were collected during this period. Several analyses of these data were accomplished. Slope factors derived for the relationship between blood lead, soil and dust concentrations are age-dependent and similar to literature reported values. Repeat measures analysis assessing year to year changes found that the remediation effort (without intervention) had approximately a 7.5 μg/dl effect in reducing a 2-year-old child's mean blood lead level over the course of the last ten years. Those receiving intervention had an additional 2–15 μg/dl decrease. Structural equations models indicate that from 40 to 50% of the blood lead absorbed from soils and dusts is through house dust with approximately 30% directly from community-wide soils and 30% from the home yard and immediate neighborhood. Both mean blood lead levels and percent of children to exceed 10 μg/dl have paralleled soil/dust lead intake rates estimated from the pathways model. Application of the IEUBK model for lead indicates that recommended USEPA default parameters overestimate mean blood lead levels, although the magnitude of over-prediction is diminished in recent years. Application of the site-specific model, using the soil and dust partitions suggested in the pathways model and an effective bioavailability of 18%, accurately predicts mean blood lead levels and percent of children to exceed 10 μg/dl throughout the 11-year cleanup period. This reduced response rate application of the IEUBK is consistent with the analysis used to originally develop the cleanup criteria and indicates the blood lead goal will be achieved.

Self-regulation in young children: Is there a role for sociodramatic play?

This study tested Vygotsky’s assumption that sociodramatic play in early childhood contributes importantly to the development of self-regulation. It also explored whether the link between sociodramatic play and self-regulation differs for impulsive and nonimpulsive preschoolers. In a short-term longitudinal design, 51 middle-income 3- and 4-year-olds were observed in their preschool classrooms. Naturalistic observations of total dramatic play, complex sociodramatic (CSD) play, and solitary dramatic play and of self-regulation in two classroom contexts—clean-up periods and group circle time—were gathered at Time 1, in the fall of the school year. To assess development of self-regulation, clean-up and circle time observations were repeated at Time 2, in late winter and early spring. CSD play predicted development of self-regulation during clean-up periods, whereas solitary dramatic play was negatively correlated with improvement in clean-up performance. The CSD play/improved self-regulation relationship was particularly strong for high-impulsive children, nil for low-impulsive children. Findings are consistent with Vygotsky’s theory and suggest that sociodramatic experiences may be especially advantageous for impulsive children, who are behind their peers in self-regulatory development.

Individual Differences in Young Children's IQ: A Social‐developmental Perspective

From a sample of middle-class mothers and their 3-year-old children, a selected group of 36 mothers were divided into 2 groups according to the quality of their responses to the Adult Attachment Interview as a Questionnaire (Crandell, Fitzgerald, & Whipple, 1997). Twenty mothers provided coherent accounts of their early parent-child relationships (secure) and 16 mothers provided idealised, entangled, or otherwise incoherent accounts of their early parent-child relationships (insecure). The mothers were administered an abbreviated version of the WAIS-R and the children were given an abbreviated version of the Stanford-Binet Intelligence Scale. The quality of mother-child interactions was assessed by videotaping a 20-minute play episode and clean-up period, and by rating the degree of synchrony according to a modified version of the Belsky Parent-Child Interaction System (Whipple, Denburg, & Davies, 1993). The results were that children of secure mothers scored 19 points higher on the Stanford-Binet test compared to children of insecure mothers. (The adjusted mean difference was 12 points when maternal IQ, education, and family SES were taken into account.) The group difference in the children's IQ remained significant when comparisons were made between a subgroup of 12 secure and 12 insecure mothers who were matched for maternal IQ. Finally we examined the subgroup of 16 cases where child IQ scores were either 10 points higher or lower than maternal IQ. In all 6 cases where child IQ was at least 10 points below maternal IQ, the child had a mother who was insecure; in contrast, only 4 of the 10 children who had IQ scores 10 points higher than maternal IQ had an insecure mother. In terms of parent-child interaction patterns, there was suggestive evidence that the degree of parent-child synchrony was also related to child IQ. The results suggest important social-developmental contributions to young children's performance on standardised tests of intellectual ability.

Medical, Occupational, and Environmental Health Considerations for Oil Spill Response Personnel

ABSTRACT Oil spill response workers can face a variety of health concerns when a spill occurs in a remote area. Potential food, water, and disease hazards need to be addressed for both fly-in supervisory personnel and local cleanup crews. Pre-spill planning activities should consider a variety of scenarios covering a range of spills in the geographic areas of responsibility. Topics to address should include medical screening of oil spill response team members, vaccination/shots, travel kits, special clothing needs, disease control informational handouts, food and water sources, evaluation of medical personnel and facilities and identification of medical evacuation plans. Activities occurring during the spill cleanup period might include medical screening of food handlers and local workers, confirming the availability of local medical facilities and evacuation routes, conducting routine clinic operations, checking the sources and handling of food and water, checking housing conditions, implementing a disease vector control program, and providing training related to local environmental hazards. Post-cleanup activities would include safe disposal of medical and other waste, providing post-spill medical exams, and documenting lessons learned during the spill. Successfully controlling health issues during a spill may only be possible if an appropriate level of planning is conducted.

Reduced fertility after the crash of a U.S. bomber carrying nuclear weapons? A register-based study on male fertility

A register-based study was performed to elucidate whether workers employed on the Thule air base in the clean-up period after the crash of a U.S. B-52 bomber carrying nuclear bombs had reduced fertility, as measured by the numbers of liveborn children. The highest birth rates were among 25–34-year olds with 1–3 years of employment on the base, but who had not worked at the base the year before, who already had one child, with a 2–5-year interval since the birth of the last child. No difference was seen between the group of men who had worked at the base during the clean-up period after the crash—the possibly exposed group—and those people who had worked at the base only outside the clean-up period. Because of the massive media coverage and possible claims for damages a register-based study is the only practicable way of elucidating statements about infertility. The main conclusion is that the accident has not reduced fertility.

High mortality in the Thule cohort: an unhealthy worker effect.

The objective was to study mortality in the Thule cohort in order to clarify whether it is a selected population and to ascertain the possibility of misinterpretation when national mortality rates are used as reference in the analysis of occupational mortality. The cohort consists of 4322 Danish men who were employed between 1963 and 1971 at the Thule air base in Greenland. One part of the cohort were employed during the clean-up period after the crash, in 1968, of a US bomber carrying nuclear weapons, the other part had been employed only outside the clean-up period. The cohort was followed up until 1992. After 30 years of follow-up, SMR was 1.38 for all causes (95% confidence interval [CI]: 1.28-1.49), 1.25 for cancer (95% CI: 1.07-1.45), 1.17 for circulatory diseases (95% CI: 1.01-1.34), 1.58 for other natural causes (95% CI: 1.35-1.84), and 1.46 for violent deaths (95% CI: 1.22-1.74). Marked excess mortality measured by SMR was found from lung cancer 1.70, AIDS 3.55, alcoholism 4.04, cirrhosis of the liver 2.45, symptoms and ill-defined conditions 1.93, and suicide 1.63. The SMR was 1.09 for the age group 17-24 at entry, 1.42 for the age group 25-34, and 1.45 for the age group > or = 35. The high mortality and the mortality pattern in the Thule cohort shows strong evidence for selection and provides strong support for the suggestion that these workers constitute a group in poor health probably caused by lifestyle. The study demonstrates that an incomplete analysis (i.e., one limited to a subgroup of workers involved in the radiation clean-up) could lead to spurious conclusions about hazardous occupational exposures.

Occupational Health and Hygiene following a Fire in a Warehouse with an Asbestos Cement Roof

This paper deals with the occupational health and hygiene advice that was given in the immediate aftermath and clean-up period of a major fire in a large warehouse with an asbestos cement roof. Work on site was carefully monitored and we believe that no health hazards occurred subsequent to the fire, in particular only very low levels of asbestos were detected during the clean-up. In addition, the need to disseminate information as widely and as rapidly as possible to the workforce and others following such a disaster is emphasized.

The cost of eliminating pseudorabies from swine herds in Iowa

The costs of eradicating pseudorabies virus (PRV) from 23 swine herds participating in the Iowa Pseudorabies Eradication Pilot Project are reported. Three feeder pig finisher herds had PRV eliminated, using depopulation-repopulation, at a total clean-up cost of $0.39 per hog marketed over the course of the clean-up period. Clean-up costs for the single farrow-to-finish producer using depopulation-repopulation were $203.66 per sow; the largest expense to the producer being $106.60 lost per sow in inventory during downtime. In five herds using test and removal, the total cost was $7.78 per sow and 14 producers using offspring segregation eliminated PRV at a total cost of $40.87 per sow in inventory. This analysis excludes 17 infected herds for which complete data were not available during the study period.

Initial conditioning of the vessel wall and the graphite limiters in DIII-D

The Doublet III tokamak has been rebuilt as the DIII-D, to accommodate large cross-section ( a = 0.67 m), highly elongated ( b a ≳ 2 ) plasmas with either a dee-shaped limiter configuration or a single null, poloidal divertor. The new vacuum vessel has been conditioned by a combination of 400°C baking, Taylor pulsed discharge cleaning (TDC), and rf-assisted glow cleaning (RGC). Tokamak operation began in February 1986 with the attainment of an 0.5 MA discharge on the first day plasmas were attempted. Rapid achievement of high current ( I ≥ 2.0 MA) tokamak discharges in the DIII-D device underscores the importance of high temperature bakeout in shortening the initial cleanup period for a vessel with large amounts of graphitic armor.

Quake, Rattle, and Roll

A description is given of the Coalinga earthquake and of the damage done to the Coalinga District Library. Mention is made of the help, both literal and financial, offered the library during the cleanup period and later on. Hints are presented concerning earthquake preparedness and actions that should be taken when an earthquake hits.

Evolution of Fracturing the Cotton Valley Sands in Oak Hill Field

Summary Fracturing in the Oak Hill field has changed gradually as experience has been gained with data from openhole logs, prefracture pressure buildup surveys, and postfracture tracer logs. Prefracture pressure buildups are used with a computerized pressure buildups are used with a computerized reservoir simulator to predict production performance after stimulation. Fracture geometry performance after stimulation. Fracture geometry and pressure buildup analysis become increasingly important as the present infill drilling progresses. Introduction The Oak Hill field in northeastern Rusk County, TX, has several producing formations; however, this paper focuses only on the Cotton Valley Sand series paper focuses only on the Cotton Valley Sand series in the field (Fig. 1). The 28 wells on which data are presented (Table 1), starting with the first well presented (Table 1), starting with the first well completed in Nov. 1976, are operated by the same company. Results of another 30 wells in the field operated by others provided additional bases for improvement in fracture treatment procedures.Three broad aspects of the program are reviewed, including case histories, reservoir simulator studies, and considerations for improvement in future fracture stimulations. Several subject-related sections are presented with conclusions and/or reasons for change of procedures at the end of each section. Early History Completions of the first five wells included a series of two to four fracture jobs, separated with sand plugs, which extended over the entire Cotton Valley Sand series from the Bessier shale to the B limestone - a section of approximately 1,400 vertical ft. Each fracture job was performed on two to six sand members through 2 7/8-in. tubing with a minimum of two holes per sand for a total of 16 to 19 holes so that a strict limited-entry fracture treatment could be performed. The treatment was spearheaded with 2,000 gal of 10 or 15% HCl with balls on the bottom stage for perforation breakdown. No balls were used above a sand plug. Equal fluid volumes containing 1, 2, and 3 lbm/gal of 20-40 mesh sand followed the pad at injection rates of 15 to 25 bbl/min. Proppant pad at injection rates of 15 to 25 bbl/min. Proppant was tailed in with radioactive tracer material. Fifteen jobs were executed essentially as designed with only three screen-outs, all of which occurred after about 90% of the designed volume had been pumped.Although the deepest zone fractured often was allowed to flow a short time before performing the other fracture stages, the succeeding stages exposed the formation to full volumes of fracture fluid for several days--i.e., until two or three additional fracture jobs and sand washing could be performed. This procedure, in part, defeated the purpose of having a gas sales line ready for early fracture fluid flowback and continuous formation production until complete cleanup was achieved. Completion of the sixth well included plans for three fracture stages similar to those used in the first five wells. Concern about formation retention of fracture water prompted an extended cleanup period after the first fracture stage. Only the Taylor zone, the +/- 300 gross ft of the deepest Cotton Valley Sand series, was fractured. No further stimulation was performed because the Taylor zone treatment resulted performed because the Taylor zone treatment resulted in the best gas well to date with negligible water production. production. From fracture treatments of the first six wells the following conclusions and/or comments are offered.1. The Taylor zone appears to have the highest potential. Water production problems in the first potential. Water production problems in the first five wells may be coming from the middle and upper sands.2. The sand plugs have provided positive separation between the fracture jobs and have allowed multiple fracture stages without the necessity of killing the well. JPT P. 799

Shell thinning and reproductive impairment in black ducks after cessation of DDE dosage.

Captive black ducks (anas rubripes) were fed dietary DDE [1,1-dichloro-2,2-bis (p-chlorophenyl)ethylene] at 10 ppm (dry weight; about 2 ppm on a natural diet basis) for 2 breeding seasons, then untreated feed for 2 succeeding years. Residues of DDE in the carcasses of adults declined 90% during the 2-year clean-up period. Following 2 years of dietary DDE, mean residues in eggs reached 64.9 ppm. Even after 2 years on clean feed, DDE residues in the eggs averaged 6.2 ppm or 9.5% of the mean DDE level reached after 2 years on treated feed. Shells of eggs from treated hens were about 20% thinner than shells of eggs from controls. Stoppage of DDE dosage resulted in progressively thicker shells, yet even after 2 years on untreated feed hens laid eggs with shells about 10% thinner than control hens. After DDE was removed from the diet, DDE residues in the eggs decreased, shell thickness increased, and reproductive success improved. Hens previously exposed to DDE, but then fed clean feed for 2 years, still produced significantly fewer surviving ducklings than did control hens.