Reserve Pits Research Articles

Path to autonomous soil sampling and analysis by ground-based robots

Good site characterization is essential for the selection of remediation alternatives for impacted soils. The value of site characterization is critically dependent on the quality and quantity of the data collected. Current methods for characterizing impacted soils rely on expensive manual sample collection and off-site analysis. However, recent advances in terrestrial robotics and artificial intelligence offer a potentially revolutionary set of tools and methods that will help to autonomously explore natural environments, select sample locations with the highest value of information, extract samples, and analyze the data in real-time without exposing humans to potentially hazardous conditions. A fundamental challenge to realizing this potential is determining how to design an autonomous system for a given investigation with many, and often conflicting design criteria. This work presents a novel design methodology to navigate these criteria. Specifically, this methodology breaks the system into four components – sensing, sampling, mobility, and autonomy – and connects design variables to the investigation objectives and constraints. These connections are established for each component through a survey of existing technology, discussion of key technical challenges, and highlighting conditions where generality can promote multi-application deployment. An illustrative example of this design process is presented for the development and deployment of a robotic platform characterizing salt-impacted oil & gas reserve pits. After calibration, the relationship between the in situ robot chloride measurements and laboratory-based chloride measurements had a good linear relationship (R2-value = 0.861) and statistical significance (p-value = 0.003).

Alaskan North Slope Legacy Wells: Case Study

ABSTRACT Various State of Alaska agencies, including the Alaska Department of Environmental Conservation (ADEC), are currently investigating 136 legacy wells within the National Petroleum Reserve-Alaska (NPR-A) and surrounding lands. These legacy wells were drilled between 1944 and 1981 by federal agencies, including the United States Navy and United States Geological Survey, to explore oil reserve potential and to develop drilling techniques for Alaska's arctic. In 2004, 2010 and 2013 the Bureau of Land Management released preliminary studies describing potential environmental risks at each site. Many wells include historic reserve pits, flare pits, crude and diesel oil releases, and discarded solid waste. Tundra damage and potential residual contamination are of great concern. Due to their remote locations, information on the current status of waste is limited. Regulatory agencies are developing a cleanup plan that is appropriate for their remote, Arctic environment.

Analysis of Reserve Pit Sludge from Unconventional Natural Gas Hydraulic Fracturing and Drilling Operations for the Presence of Technologically Enhanced Naturally Occurring Radioactive Material (TENORM)

Soil and water (sludge) obtained from reserve pits used in unconventional natural gas mining was analyzed for the presence of technologically enhanced naturally occurring radioactive material (TENORM). Samples were analyzed for total gamma, alpha, and beta radiation, and specific radionuclides: beryllium, potassium, scandium, cobalt, cesium, thallium, lead-210 and -214, bismuth-212 and -214, radium-226 and -228, thorium, uranium, and strontium-89 and -90. Laboratory analysis confirmed elevated beta readings recorded at 1329 ± 311 pCi/g. Specific radionuclides present in an active reserve pit and the soil of a leveled, vacated reserve pit included 232Thorium decay series (228Ra, 228Th, 208Tl), and 226Radium decay series (214Pb, 214Bi, 210Pb) radionuclides. The potential for impact of TENORM to the environment, occupational workers, and the general public is presented with potential health effects of individual radionuclides. Current oversight, exemption of TENORM in federal and state regulations, and complexity in reporting are discussed.

Life-Cycle Impact Assessment of oil drilling mud system in Algerian arid area

The objective of this work is to assess the environmental impacts of the drilling mud system in Algeria's arid region. Water-based mud (WBM) and oil-based mud (OBM) are used during well drilling in Hassi Messaoud petroleum field, and have a considerable pollution potential particularly on the aquifer system which constitutes the single resource of drinking water in the Sahara. The Life-Cycle Assessment (LCA) approach is applied to evaluate the impacts of several drilling mud systems across all stages of their life cycle, e.g. use, treatment and disposal. Environmental impacts of five treatments scenarios corresponding to the drilling waste management applied in Hassi Messaoud are compared: reserve pit without treatment (burial option), secondary high centrifugation (vertical cuttings dryer), stabilisation/solidification online, stabilisation/solidification off line and thermal desorption. The impact assessment is carried on using the LCIA models of Impact 2002+ method in SIMAPRO7 software. This assessment identifies human toxicity and terrestrial eco-toxicity as the major impact categories in this specific arid context and quantifies the emissions contributions. The local environmental impact is the most important of the drilling mud life cycle and is mainly linked to emissions from reserve pits, treated cuttings, and drilling phase 16″ through the Turonian and Albian aquifer. The main contributing substances are aromatic hydrocarbons fraction and metals in particular barium, zinc, antimony, arsenic, and aluminium. Concerning the comparison of the treatment scenarios, it appears that stabilisation/solidification online is the best one; it has the lowest impact score in the two dominating categories because of the waste minimisation: mud storage avoided in the reserve pit. The second best scenario is the thermal desorption which obtains the lowest impact score in carcinogen effects due to hydrocarbons reduction (<1%) and avoided impacts of recovered oil. The toxic substances fate modeling will be improved by taking into account their site-specific impact.

The Use of Seedbed Modifications and Wood Chips to Accelerate Restoration of Well Pad Sites in Western Colorado, U.S.A.

Semiarid ecosystems of Western North America are experiencing a boom in natural gas development. However, these systems are slow to recover from the disturbances created. The purpose of this study was to develop improved restoration techniques on natural gas well pads in Western Colorado. This study examined effects and interactions of seedbed modifications, soil amendments, seed mixtures, and seeding methods. The experiment was conducted in pinyon‐juniper and semidesert shrub plant communities on five natural gas well pads beginning in 2006. Soil and plant cover data were collected to assess the effectiveness of 16 different treatment combinations. After two growing seasons, we found that patches of soil salinity (&gt;4 dS/m) reduced plant cover to less than 20% on 55 of our 240 experimental plots. These patches of salinity, such as where reserve pits were buried, may need to be treated to completely restore cover on the total gas pad area, although causes of salinity patches needs further investigation. After removing the 55 saline plots from our data analyses, we found that wood chips (WC) as a soil amendment increased organic matter content and reduced non‐native species. Rough seedbed modifications increased the establishment of native species, especially during years of below average precipitation. Island broadcasting resulted in an increase of noxious plant cover during the second growing season. From these findings we recommend that disturbed well pads in a similar environment be restored by seeding native species on sites that are amended with WC and physically modified to create a roughened seedbed.

Effect of Drilling Fluid Additives on the Niger Delta Environment: -A Case Study of the Soku Oil Fields

The effect of drilling fluid additives on the Soku oil fields environment has been examined. Soil and reserve pits in various locations were assessed for some physico-chemical characteristics and heavy metal content using standard methods for water and wastewater analysis. Plant growth and other biomass were also assessed. The result showed that the levels of most physiochemical characteristics are generally within the limits of guidelines by regulatory authorities. However, trace metal levels are generally below toxic levels, except Fe, Ca and Mg, which were higher than recommended values. These high values of Fe, Ca and Mg (17.70-220.2; 11.03-296.80; and 12.62-75.71 ppm) respectively are characteristic of the Niger Delta Swamp soils. Also a poor plant growth was observed in the immediate vicinity of location of drilling operations, an indication of the toxic effect of drilling fluids on the environment.

Environmental Control of Drilling Mud Discharge Through Dewatering In Cold Weather Climates: Effect of Ambient Temperature

Abstract This paper presents results of an experimental study into the effect of drilling mud temperature upon dewatering performance. Three temperature ranges were considered: from flowline temperature to room temperature, from room temperature to freezing point, and the freeze -20 ° C (-4 ° F) thaw 12 ° C (54 ° F) cycle. The tested drilling fluids included unweighted and weighted fresh water muds and a weighted salt water mud. A sealed laboratory batch reactor was used in the experiments to prevent rapid vapourization of separated water at temperatures above 60 ° C (140 °F). Also, ice or ice-salt baths were utilized for deep freezing. The dewaterability (net water removal) was measured with a bench-top plate press under constant expression pressure 207 kPa (30 psi). The freeze/thaw treatment greatly enhanced dewaterability by releasing 34 – 39% by volume of the mud water. Mechanical dewatering followed; it required half the chemicals and released an additional 36 – 43% of water. The process proved to be very effective, reducing waste mud volume by 64 – 72%. It is wellsuited for the Arctic with its natural freeze/thaw cycles. The results of experiments at temperatures above 21 ° C (70 °F) showed that there is little advantage to dewatering hot drilling mud diverted from active system. A 10% increase of water removal was observed above 60 ° C (140 °F). The experiments at temperatures below 21 ° C (70 °F) showed that in cold weather climates the waste drilling mud diverted from active system should be dewatered when its temperature is still above 40 °F. Otherwise, more chemicals will be needed for separation enhancement or the dewatering process will become entirely ineffective. Introduction The dewatering process has become increasingly popular in oilfield drilling practices. Its first field applications in the early 1980s were related to oilfield pit closure procedures, where drilling waste from reserve pits was processed by portable dewatering units. In this application, the dewatered pit solids can be directly disposed on-site using burial, trenching, or land treatment practices, or they can be initially solidified to prevent any potential leaching of toxicants. The dewatering effluent may be either directly disposed to the land or surface waters, or, when the effluent limitation guidelines are not met, can be injected underground. Several configurations of the pit dewatering processes commercially offered to the oilfield petroleum industry in the US and abroad have been reviewed in the literature(1). Later, the dewatering process was included into the active mud processing systems for separation and recycling of the mud water phase to minimize the drilling waste discharge volume(2–5). The dewatering of circulating active muds proved to be more difficult than the dewatering of reserve pit sludges, particularly when the mud systems contained high concentrations of surface-active solids(3) after being heavily treated with the suspension stabilitycontrol agents, as is the case for dispersed muds. Despite disadvantages, the dewatering of active mud offered an attractive alternative to drilling a well without a reserve pit, particularly in zerodischarge areas.

Selective-Placement Burial of Drilling Fluids: Effects on Soil Properties, Buffalograss and Fourwing Saltbush after 4 Years

A field study was established in 1986 to evaluate selective-placement burial as an alternative technique for on-site disposal of drilling fluids in arid and semiarid areas. Soluble salt and heavy metal migration in the soil, and establishment, yield and chemical composition of fourwing saltbush (Atriplex canescens (Pursh) Nutt.) and buffalograss (Buchloe dactyloides (Nutt.) Engelm.) were determined 44 months after simulated reserve pits were constructed to provide burial depths of 30, 90 (with and without a 30-cm thick, coarse limestone capillary barrier), and 150 cm, with sequential replacement of stockpiled subsoil and topsoil. Soluble salt concentrations increased most significantly in the 30-cm zone immediately above buried drilling fluids, regardless of treatment. Upward salt movement was greatest in the 90- and 150-cm treatments, with significant increases in Electrical Conductivity (EC) and Exchangeable Sodium Percentage (ESP) values observed as much as 60 and 30 cm above buried drilling fluid, respectively. Capillary barriers reduced the extent of upward salt migration, but had little effect in soil zones immediately overlying the drilling fluid. There was no evidence of upward migration of Ba, Cr, Cu, Ni, or Zn from buried drilling fluids into overlying soil, but concentrations of Cu and Zn were greater in saltbush stems grown on plots with buried drilling fluids on 1 site. Fourwing saltbush survival averaged 92 to 100% and was not affected by depth of drilling fluid burial. Significant reductions in saltbush canopy cover and yield on the 30-cm burial treatment were observed on 1 study site. Elevated Na concentrations in aboveground tissue of both species in the 30-cm burial treatment on 1 site did not adversely affect survival or plant growth. Differences between study sites in the extent of upward salt movement in the soil and in plant response were attributed to differences in soil clay type and content.

Six Strategies for Rehabilitating Land Disturbed by Oil Development in Arctic Alaska

Oil development in arctic Alaska has left a range of disturbed lands that will eventually require rehabilitation. These lands include gravel roads and pads, gravel pits and overburden stockpiles, drilling reserve pits, occasional accidental spills, and other minor disturbances to the tundra. A long-term research program investigating site-specific and cost-effective methods for rehabilitating degraded lands for fish and wildlife habitat has developed six general strategies that are applicable to the range of disturbed conditions. These strategies include 1) flooding of gravel mine sites for fish habitat, 2) creation of wetlands in ponds perched on overburden stockpiles, 3) revegetation of thick gravel fill and overburden to compensate for lost wildlife habitat, 4) removal of gravel fill to help restore wet tundra habitats, 5) restoration of tundra on less severely modified habitats, and 6) remediation of areas contaminated by oil spills, seawater spills, and drilling mud. Although most techniques are in the early stage of evaluation, preliminary results suggest that successful methods are available to create diverse, productive, and self-sustaining communities that are useful to a range of wildlife.Key words: Arctic, Alaska, disturbance, habitat, tundra, oilfield, rehabilitation, revegetation, restoration, wetlands

Closed-Loop Operation With Alternative Dewatering Technology

Summary The introduction of dewatering devices for closed-loop drilling-fluid circulating systems and reserve pits is derived from technology that has been used in the industrial- and sanitary-waste treatment industries for years. This paper describes an overview of the need for closed-loop systems and provides the optimum design layout, including the fit of a dewatering device, for a drilling location. The introduction of a nonconventional dewatering device, called a screw press/thickener, is reviewed. A case history describing use of this technology in a southern Louisiana inland-marsh-area well is analyzed for the technical and economic viability of operating in a closed-loop mode. Results from this effort include a viable alternative to hauling off waste fluids from drilling sites and the realization that use of this technology can be justified economically.

Selective‐Placement Burial of Drilling Fluids: I. Effects on Soil Chemical Properties

AbstractBurial of spent drilling fluids used in petroleum and natural gas exploration was evaluated for reducing soil contamination caused by conventional, surface disposal of these wastes on arid and semiarid rangelands. Simulated reserve pits at two locations provided burial depths of 30, 90 (with and without a 30‐cm capillary barrier of coarse limestone), and 150 cm below the surface, with sequential replacement of stockpiled subsoil and topsoil. The drilling fluids contained extremely high concentrations of soluble salts [electrical conductivities (EC) = 155–185 dS m−1], with Na and Cl being the dominant soluble ions. Upward migration of contaminants was evaluated over a 20‐month period. Soluble salts migrated upward 15 to 30 cm into the overlying soil, and salt movement appeared to be governed to a greater extent by diffusive rather than convective flow mechanisms. Capillary barriers of coarse limestone effectively reduced salt movement at one of the two sites. Sodium, Ca, and Cl were the dominant mobile ions. Exchangeable Na percentages did not increase in soil increments &gt; 15 cm above buried drilling wastes. Barium, Cr, Cu, Ni, and Zn in drilling fluids did not migrate into overlying soil. Movement of contaminants was similar where fourwing saltbush [Atriplex canescens (Pursh) Nutt.], a deep‐rooted shrub, and buffalograss [Buchloe dactyloides (Nutt.) Engelm], a hallow‐rooted grass, were used for revegetation. Selective‐placement burial of drilling fluids offers an effective and environmentally sound alternative to conventional surface disposal. The probability of upward movement of excessive soluble salts into the plant root zone appears greater for 30‐cm burial, compared to 90‐ or 150‐cm burial, because of greater soil water contents at the soil/waste interface and greater upward water potential gradients in the surface 30 cm.

Petroleum Drilling and Production Operations in the Gulf of Mexico

Decades of offshore and inland petroleum drilling and production in the Gulf of Mexico and on the Gulf coast have provided the much needed energy and chemical feedstocks to the nation, and also have made an impact on the environment in the area. Our study showed deposits of contaminated sediment on the ocean floor around offshore platforms, old reserve pits, and dump sites next to many surface facilities and compressor stations. The substances found on the ocean floor and in dump sites are simple or emulsified mixtures of silt, hydrocarbons, and water. The cleaning of the ocean floor and pits is an economic and technical challenge. Hydrocarbons are from crude oil and chemical additions for various operational necessities, including additions of biocides, corrosion inhibitors, antifreezes, and coagulants. When the new government regulations lower the allowable maximum total organic carbon level to the 50 ppm range, these hydrocarbons can no longer be ignored by drilling and production operators.

Transplanting shrubs for revegetation of salt-affected soils

Vegetation (secondary) succession is extremely slow on soils contaminated with soluble salts by petroleum exploration activities in arid and semiarid areas. Excessive salt accumulations interfere with seed germination and seedling establishment of most species used for revegetation. Establishment and growth of transplanted fourwing saltbush ( Atriplex canescens) seedlings and rooted stem cuttings, and seedlings of oldman saltbush ( Atriplex nummularia), winterfat ( Ceratoides lanata), and prostrate kochia ( Kochia prostrata) were evaluated on three saline-sodic (EC (electrical conductivity) = 23 − 93 dS m -1, ESP (exchangeable sodium percentage) = 13−46%) oil well reserve pits over a three-year period. Survival of fourwing saltbush seedlings from an accession not adapted to saline soils was only 32%, compared with ⩾ 73% for seedlings or stem cuttings from an accession adapted to saline soil. Oldman saltbush suffered 100% mortality subsequent to subfreezing temperatures during the first winter following planting. Survival of winterfat and prostrate kochia transplants was 61 and 48%, respectively, after three years, and growth of these species was acceptable on the saline-sodic soils. Selection or specific accessions of species adapted to the existing conditions of the site to be revegetated appeared most promising for revegetation under extremely harsh environmental conditions.

Statistical Assessment and Sampling of Drilling-Fluid Reserve Pits

Summary A field survey of four drilling-mud reserve pits associated with 14,000-ft [4267-m] exploratory wells onshore U.S. gulf coast is presented. Each pit was sampled with a three-dimensional grid base with 80 to 100 samples per pit. The samples were analyzed for solids, liquids, rheological properties, and such contaminants as oil, chlorides, and metals (Cr, Pb, Ba, and Zn). The statistical data were used to develop the recommended pit sampling procedure, which included the best sampling depth and the optimum number of samples to assess the metal toxicity within a given accuracy. Two example calculations are also presented.

Drilling Fluids and Reserve Pit Toxicity

Drilling fluids are now classified as exempt under the Resource Conservation and Recovery Act (RCRA) hazardous waste laws. Since 1986, however, the U.S. Environmental Protection Agency (EPA) has been studying reserve pit contents to determine whether oilfield wastes should continue under this exemption. Concerns regarding reserve pit contents and disposal practices have resulted in state and local governmental regulations that limit traditional methods of construction, closure, and disposal of reserve pit sludge and water. A great deal of attention and study has been focused on drilling fluids that eventually reside in reserve pits. In-house studies show that waste from water-based drilling fluids plays a limited role (if any) in possible hazards associated with reserve pits. Reserve pit water samples and pit sludge was analyzed and collated. Analyses show that water-soluble heavy metals (Cr, Pb, Zn and Mn) in reserve pits are generally undetectable or, if found in the total analysis, are usually bound to clays or organics too tightly to exceed the limitations as determined by the EPA toxicity leachate test. The authors' experience is that most contamination associated with reserve pits involves high salt content from produced waters and/or salt formations, lead contamination from pipe dope, or poorly designedmore » pits, which could allow washouts into surface waters or seepage into groundwater sources. The authors' analyses show that reserve its associated with water-based drilling fluid operations should not be classified as hazardous; however, careful attention attention should be paid to reserve pit construction and closure to help avoid any adverse environmental impact.« less

Drilling fluids and the arctic tundra of Alaska: Assessing contamination of wetlands habitat and the toxicity to aquatic invertebrates and fish

Drilling for oil on the North Slope of Alaska results in the release of large volumes of used drilling fluids into arctic wetlands. These releases, usually come from regulated discharges or seepage from reserve pits constructed to hold used drilling fluids. A study of five drill sites and their reserve pits showed an increase in common and trace elements and organic hydrocarbons in ponds near-to and distant from reserve pits. Ions elevated in water were Ba, Cl, Cr, K, SO4 and Zn. Concentrations of Cu, Cr, Fe, Pb, and Si in sediments were higher in near and distant ponds than in control ponds. The predominant organics in drill site waters and sediments consisted of aromatic and paraffinic hydrocarbons characteristic of petroleum or a refined product of petroleum. In 96-hr exposures in the field, toxicity toDaphnia Middendorffiana was observed in water from all reserve pits, and from two of five near ponds, but not from distant ponds. In laboratory tests withDaphnia magna, growth and reproduction were reduced in dilutions of 2.5% drilling fluid (2.5 drilling fluid: 97.5 dilution water) from one reserve pit, and 25% drilling fluid from a second. Growth and reproduction were not affected at these dilutions of fluid from the other three reserve pits. Additional regulations—such as an upper limit on aromatic hydrocarbon content and toxicity to sensitive organisms —are needed to improve safety for aquatic organisms in habitats receiving used drilling fluids.

Determination of Polycyclic Aromatic Hydrocarbons in Drilling Muds and Reserve Pits by Isotope Dilution GC/MS with Selected Ion Monitoring

Abstract Shale cuttings, spent fluids, and drilling muds from natural gas exploration were analyzed for extractable hydrocarbons including polycyclic aromatic hydrocarbons (PAH) and alkylated-PAH. Complex mixtures of aliphatic hydrocarbons with carbon numbers from 10 to 32 were found in three phases coexisting in waste pits where extractable hydrocarbons were 45–990 mg/L in wastewater and 265–59 000 mg/kg in drilling muds/pit sediments. Over 20 members of 2–4 ring PAH and alkylated-PAH were isolated using chemical prefractionation and quantified by isotope dilution GC/MS with selected ion monitoring. Concentrations of total PAH assessed at three sites including a central waste storage site followed the trend: hydrocarbon film > oil-based muds > water-based muds > shale cuttings > = phase and ranged from 15mg/L for reserve pit water to > 24000mg/kg for oil-based drilling muds. Inhomogeneity of large reserve pits due to mechanical dispersion of wastes was illustrated using solution/sediment distribution rat...

Comparison Study of Solid/Liquid Separation Techniques for Oilfield Pit Closures

Summary. Vacuum filtration, belt-press filtration, screw-press filtration, and centrifuging techniques were evaluated in full-scale experiments for use in oilfield waste volume reduction. Centrifuging and belt-press filtration proved applicable to oilfield pit cleanups. Also, an effective chemical conditioning (coagulation and flocculation) was found for deliquoring seven types of oilfield waste slurries before separation. Introduction Earthen pits have been the most commonly used impoundments for collecting oilfield wastes. Originally designed to serve as drilling reserve pits, they have been storing about 300 million bbl [47.7 Mm3) of drilling fluid wastes and cuttings each year. In most cases of water-based drilling fluids, these pits were closed by conventional methods, such as pit dispersing or pit pumping. In many cases. however, the drilling reserve pits were either abandoned or converted for oil production and testing and became suspected sources of long-term environmental contamination. There are, for example, about 12,000 abandoned pits in Louisiana that are suspected of chronic damage to the environment and to public health. A public survey reported environmental problems related to oil-waste disposal in Colorado, California, Texas, Nevada, Oklahoma, and Michigan. After the Solids Waste Disposal Amendments to the Resource Conservation and Recovery Act (RCRA) exempted drilling fluids and other associated wastes from the direct application of the federal RCRA rules, each state became responsible for regulating, the storage and disposal of oilfield waste. Regulations recently issued in Louisiana require that oil-waste pits be closed within 6 months by dewatering, followed by burial, trenching, land treatment, or solidification. Amendments to Texas Railroad Commission Rule No. 8 require closure of pits with chloride concentration levels below 6,100 ppm within one year and closure of pits with higher chloride concentration levels within 30 days after drilling operations end. Their recommended methods are dewatering, backfilling, burial, or land farming. Analysis of other local regulations regarding oilfield waste disposal indicates that reduction of a drillsite waste with solid/liquid separation (SLS) is the first and fundamental step toward solution of the disposal problem. Most literature on the environmental implications of oil exploration and production is dedicated to either an assessment of the environmental impact of oilfield waste and its characterization or the promotion of available cleanup systems. The environmental fate of oilfield offshore operations has been documented in more than 650 technical papers. Only within the past 10 years has emphasis been placed on the onshore environmental impact of oilfield waste disposal, sampling and characterization of drilling reserve pits, and pit closure procedures. Improvement in solids control and development of new techniques for oilfield-waste volume reduction are being investigated in several industrial laboratories. However, very little has been published to date. The research effort reported here is part of a continuing experimental program concerning the development and implementation of environmental techniques in petroleum engineering practices. The problems addressed are related to waste volume reduction resulting from SLS. Specifically, answers have been sought to the following questions.Is it possible to use typical oilfield solids-control equipment (centrifuges) for waste pit cleanup?Do other separation techniques-such as vacuum filtration, belt pressing, or screw pressing-provide a valid alternative to pit dewatering?To what extent is chemical conditioning (coagulation and flocculation) applicable to oilfield waste?How does the separation mechanism of oilfield waste differ from existing dewatering techniques (e.g., waste water treatment)? Experiment Design All experiments were performed at the Louisiana State U. Solids Control Environmental Laboratory. The laboratory consists of three units: a full-scale unit, an analytic unit, and a portable pit-sampling unit. The full-scale unit is designed for pilot experiments on SLS with handling, pumping, and chemical injection. Its capacity allows for a 200-bbl [31.8-m3] sample volume, a 110-gal/min [0.4 16-m3/min] feed rate, and an 8.4-gal/min [0.031-m3/min] on-line polymer injection rate. The analytic unit is designed for solid/liquid analysis and bench-scale simulation experiments. The pit-sampling unit is designed for field sampling and mapping of oilfield waste impoundments. JPT P. 845^

Revegetation of Oil Well Reserve Pits in West Texas

On-site dispod of drilling fluids frquently causes severe, longterm disturbance of rangeland soils. The effects of mulch on establishment and standjng crops of seeded kochia [Koch& swpar& (L.) sChrad.1, King Ranch bluestem [Bothhchftm is&emwn (L.) Ifen& Lebmann lovegrass (Erugros& &nau&na Nees), kleingrass ‘Selection 75’ (Punieum wkuarum L.), alkali sacaton [Sparobolus airoides (Torr.) Torr.1, and fourwing saltbusb [Atr@kx ~(III~~E~IL~ (Pursh) Nuttl, and transplanted founving saltbush were evaluated on 4, recently covered oil well reserve pits in Reagan County Texas, in 1981 and 1982. On-site disposal of drilling fluids resulted in substantfal to large increases in sodium adsorption ratios (SAR) and concentrations of soluble salts, primarily sodium chloride, in reserve pit soils. Mulching with 4,500 kg/ha of weathered hay had no effect, but irrigation was essential for establishment and growth of the seeded species on severely contaminated soils (EC* 71 to 114 dS m-‘, SAR 33 to 127). Mulching improved establishment and yields of seeded King Ranch bluestem and kleingrass on reserve pit soils with EC. values of 9 to 11 dS m-l and SAR values of 12 to 16. Appliation of 5.1 cm of supplemental water and mulching reserve pit soils with EC. values of 3 to 7 and SAR values of 5 to 9 stimulated establishment of competing vegetation, which tended to decrease establishment and yields of seeded and transplanted species. Establishment and yields of transplanted fourwing saltbush were acceptable with or without mulching or irrigation. Survival of fourwfng saltbusb transplants was near 199% on moderately contaminated soils and 26 to 39% on severely contaminated soils.