Effect Of Drill Cuttings Research Articles

ПРОБЛЕМА ОБРАЩЕНИЯ С БУРОВЫМИ ШЛАМАМИ ПРИ ИСПОЛЬЗОВАНИИ УГЛЕВОДОРОДНЫХ БУРОВЫХ РАСТВОРОВ

Petroleum is one of the main sources of energy in the world. Oil production is associated with generation a huge amount of drilling waste, which impacts the environment negatively. Oil-based drilling fluids are widely used nowadays, but they are more dangerous than waster-based drilling fluids. This research is devoted to management of drill cuttings, environmental legislation and new technologies for processing. Environmentally responsible actions for eliminating the effect of drill cuttings with oil-based drilling fluids on the environment are discussed.

Effects of drill cuttings on larvae of the cold-water coral Lophelia pertusa

Fossil fuel consumption is predicted to dominate energy needs until at least 2040. To make up for reduced production from maturing fields, oil and gas exploration activities on the Norwegian continental shelf have greatly increased over the past several years. Strict emission controls have resulted in a substantial reduction in the release of hazardous chemicals. However, because of the increased exploration the discharges of water-based drill cuttings and muds have increased substantially, temporarily increasing water column sediment loads. The stony coral Lophelia pertusa is the most widely distributed and well-studied of the structure forming cold water corals (CWC) and it thrives in Norwegian waters where many reefs are located in the vicinity of oil platforms or exploration areas. This species provides habitat for a diverse and abundant assemblage of invertebrates and fishes, including commercially valuable species. High sediment loads are known to negatively affect adult corals, but impacts on the early life history stages are unknown. We investigated the effects of a range of drill cutting concentrations (0.5–640ppm) on larvae of L. pertusa at ages five days and 15–20 days. One set of experiments was conducted in static experimental chambers that exposed larvae to decreasing concentrations over time, and the other maintained continuous drill cutting concentrations for the duration of the experiment (24h). Increased sediment load for a duration of 24h caused significant larval mortality, but there was an age-dependent difference in sensitivity of larvae. Younger larvae were significantly more susceptible to lower concentrations of drill cuttings than older larvae, while the older larvae were significantly more affected at higher concentrations. Five day old larvae were affected at treatment concentration 40ppm. The larval cilia became clogged, preventing the larvae from swimming actively and ultimately causing mortality. Larvae of many species use cilia for swimming and feeding, so negative impacts of increased sediment may not be limited to corals.

Environmental effects monitoring at the Terra Nova offshore oil development (Newfoundland, Canada): Program design and overview

An environmental effects monitoring (EEM) program was developed by Suncor (formerly Petro-Canada) in 1997/98 to assess effects of the Terra Nova offshore oil and gas development on the receiving environment. The Terra Nova Field is located on the Grand Banks approximately 350km southeast of Newfoundland (Canada), at approximately 100m water depth. The EEM program was developed with guidance from experts in government, academia and elsewhere, and with input from the public. The EEM program proposed by Suncor was accepted by Canadian regulatory agencies and the program was implemented in 2000, 2001, 2002, 2004, 2006, 2008 and 2010, with pre-development sampling in 1997. The program continues to be implemented every two years. EEM includes an assessment of alterations in sediment quality through examination of changes in sediment chemistry, particle size, toxicity and benthic invertebrate community structure. A second component of the program examines potential effects on two species of commercial fishing interest: Iceland scallop (Chlamys islandica) and American plaice (Hippoglossoides platessoides). Chemical body burden for these two species is examined and taste tests are performed to assess the presence of taint in edible tissues. Effects on American plaice bioindicators are also examined. A final component of the program assesses potential effects of the Terra Nova development on water quality and examines water column chemistry, chlorophyll concentration and physical properties. The papers presented in this collection focus on effects of drill cuttings and drilling muds on the seafloor environment and, as such, report results on sediment quality and bioaccumulation of drilling mud components in Iceland scallop and American plaice. This paper provides information on drilling discharges, an overview of the physical oceanography at the Terra Nova Field, and an overview of the field program designed to assess environmental effects of drilling at Terra Nova.

Annular-Pressure Losses While Casing Drilling

This article, written by Dennis Denney, contains highlights of paper SPE 166103, ’Evaluation of Annular-Pressure Losses While Casing Drilling,’ by Vahid Dokhani and Mojtaba P. Shahri, SPE, University of Tulsa; Moji Karimi, SPE, Weatherford; and Saeed Salehi, SPE, University of Louisiana at Lafayette, prepared for the 2013 SPE Annual Technical Conference and Exhibition, New Orleans, 30 September-2 October. The paper has not been peer reviewed. Casing drilling is a method by which the well is drilled and cased simultaneously. The small annulus from casing drilling can create a controllable dynamic equivalent circulating density (ECD). Casing-drilling technology enables obtaining the same ECD as with conventional drilling but with a lower (optimized) flow rate and lower rheological properties and mud weight. Frictional pressure loss during casing drilling was evaluated with computational fluid dynamics (CFD). Having accurate models for ECD, including the effects of pipe rotation and eccentricity in the annulus, is essential for success in these challenging jobs. Introduction Casing drilling builds on experience gained from drilling liners to bottom in troublesome holes. The technique was implemented for drilling a formation sequence of highly pressured shale followed by a depleted reservoir. The major problem when drilling depleted reservoirs is the narrow operational mud-weight window. With advances in top-drive systems, retrievable bottomhole assemblies, and polycrystalline-diamond-compact bits, the technology enables completing a well by use of casing as the drillstring. An often-reported benefit of casing drilling is significantly fewer lost-circulation problems. The wellbore-plastering effect that casing drilling offers can enable drilling depleted zones while causing less formation damage. Plastering also enhances pressure containment by smearing the smaller drill cuttings into the pore spaces. The aim of this study was to simulate the casing-drilling operation through CFD modeling to evaluate the combined effect of eccentricity and pipe rotation on the velocity profile of a non-Newtonian fluid. Approach Initially, the geometry of casing drilling was constructed for a given wellbore condition. Then, the domain was discretized such that the result would not be grid dependent. A series of cases was designed to compare the CFD model with the analytical solution and validate the discretization scheme. Then, the non-Newtonian-fluid (yield-power-law model) simulation was run. Thereafter, an effort was made to analyze the effect of eccentricity and pipe rotation on the yield-power-law fluid. Assumptions In drilling operations, continuous fluid circulation through the annulus results in steady-state flow. In the shallow top-hole section, the fluid can be treated as an incompressible fluid. The simulated laminar-flow regime verified the CFD results with the analytical solution. It was assumed that a single-phase fluid flows through the annulus and that the pipe geometry provides a uniform concentric annulus along the test section. For simplicity, the effects of drill cuttings were neglected in the simulation to be able to validate the CFD results with the analytical solution. Initially, the casing was treated as stationary (no pipe rotation) with a no-slip condition at the walls (both inner-pipe and wellbore). The pipe and the wellbore were assumed to be smooth. Also, the geometry was held uniform along the pipe (i.e., the effect of tool joints on pressure loss was neglected). The pipe section was considered to be 5 or 10 m long.

Effects of drill cuttings on biogeochemical fluxes and macrobenthos of marine sediments

Experimental work was performed on drill cuttings sampled from off-shore drilling operations. The cuttings contained remnants of two different types of drilling muds: a water-ilmenite based mud and an olefin-barite based mud. In a pilot experiment, a gradient of up to 65 mm thick layers of water-ilmenite based cuttings were added to 78 cm 2 core samples. In another set-up, 3 mm layers of water-ilmenite and olefin-barite based cuttings were added to replicate 1000 cm 2 box-core samples with natural benthic communities transferred from the Oslofjord, S.E. Norway. Boxes with no addition and addition of 3 mm “clean” sediment were used for control. Increased consumption of oxygen and nitrate indicated the presence of degradable organic phases in both mud systems. The release of silicate showed a general decrease with increasing thickness of the cuttings layer, but maximum rates in the 3.1 mm treatment indicated increased bioturbation at low and moderate doses. The initial (field) composition of the macrobenthic communities was maintained throughout the 3 months experimental period, and at community level, no significant difference was observed between the four treatments at the end of the exposure period. However, after grouping the treatments into “clean” (untreated control and 3 mm clean sediment) and “cuttings” (3 mm water-ilmenite and 3 mm olefin-barite based cuttings), multivariate statistical analyses revealed a significant difference in community composition between clean and cuttings treatments, and three taxa showed significantly reduced abundances in the cuttings treatments. Chemical toxicity of mud components is assumed to be small, and the observed effect was more likely a result of physical properties such as the size or shape of cuttings particles.

Brittlestars, Biomarkers and Beryl: Assessing the Toxicity of Oil-Based Drill Cuttings Using Laboratory, Mesocosm and Field Studies

Effects of drill cuttings on burrowing brittlestars (Amphiura chiajei and A. filiformls) were compared at different levels of response, from acute laboratory experiments to chronic field studies. Acute toxicity tests showed that drill cuttings containing oil-based muds had a very low toxicity (LC50 52,800 ppm total hydrocarbons in test sediment) but sub-lethal effects were detected at much lower levels using a variety of biomarkers and assays. Chronic sub-lethal effects were detected around the Beryl oil platform in the North Sea where the levels of oil in the sediment were very low (<3 ppm total hydrocarbons in sediment) and brittlestars were excluded from areas nearer the platform with higher sediment oil content. These results suggest that acute toxicity tests are a poor predictor of chronic response in these animals. the relationship between toxicity at different levels of response and the predictive power of laboratory studies is discussed.

The effects of drill cuttings on a model marine sediment system

An onshore tank system was used to model marine sediment contaminated with water-, diesel oil- and paraffinic oil-based cuttings from offshore drilling installations. The relative environmental impact of the different cuttings was assessed over a 12-month period in terms of changes in sediment microbiology and chemistry. Changes in hydrocarbon chemistry were also determined to provide information on oil composition and mechanisms of oil loss from the cuttings. Water-based cuttings proved least damaging to the sediment system, only depressing Eh levels below those of control sediments during the first 3 months of exposure. Both types of oil-based cuttings stimulated microbial activity, depressing sediment Eh levels and increasing sulphide concentrations. The effects were less severe in more lightly contaminated sediments. Oil losses were proportionally greater from more dispersed cuttings and were dependent on both physical and biological weathering. Sediments heavily dosed with oil-based cuttings became anaerobic and failed to support hydrocarbon biodegradation. More dispersed low dosage applications were more readily susceptible to microbial attack.