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With environmental concerns playing a growing role in the drilling industry, drilling waste disposal has become on unavoidable and important component of a drilling team's scope of work. By end of year 2000, sea disposal of OPF (Organic Phase Fluid) will be phased out from the British North Sea area. Cutting Re-Injection or Ship-to-Shore for thermal, solvent or inerting treatments will be the only acceptable alternatives for oily cuttings disposal. The following paper presents an innovative approach to the complex problem of the separation of OBM from cuttings using Supercritical Carbon Dioxide technology (SCCO2). Above 73,8 bars and 35°C, Carbon Dioxide (CO2) exhibits special properties such as high density, high diffusivity and low viscosity, but above all, tremendous solvent properties regarding non-polar molecules such as hydrocarbons. This special state, sometimes referred to as the 4th state of matter, is widely known as the supercritical state. CO2 in supercritical conditions is already widely used in various industrial extraction processes, such as coffee bean decaffeination, fragrances and flavors selection or pharmaceutical molecules production. A pilot unit capable of handling up to 500g of cuttings per batch and allowing supercritical CO2 steady circulation, has been developed to study the efficiency of the process. Tests have been performed on oily cuttings coming from various locations and different OBM Cuttings. Best extraction conditions have been optimized and the efficiency of the separation has been very encouraging: Residual Oil Contents (ROC), as low as 0. 2% (by weight of dry cuttings) have been achieved. An evaluation on 2 larger scale units has also been made: a 6 kg static reactor and a 10 kg rotating autoclave (both dedicated to pre-industrial feasibility studies) enabled the evaluation of the efficiency of the treatment on North Sea OBM Cuttings. Residual oil contents below 1% have also been reached proving that scaling up the process, from hundreds of grams to several kilograms, is viable and practicable. The industrial potential of this promising technology is currently under study. The application of such a technology could constitute a major breakthrough in the drilling industry, both onshore and offshore. Introduction As a general trend in the industry, environmental legislation is becoming increasingly more stringent. The impact of drilling activity is nowadays carefully monitored and the drilling engineering teams have to take into account aspects that were not traditionally within their scope of work and competence. Reduction of air emissions, drilling fluid release or treatment, and final disposal of drilling cuttings are now systematically taken into consideration from the very beginning of a project. Of course, this has a growing impact on the overall cost of a project. In the last few years, specialized companies have proposed many improvements in WBM systems. However, no major innovation can compete with the performance of an OBM system. When a well is drilled to the limits of the existing technology (high deviation, horizontal drain) or when the drilled formation is too sensitive (bore hole stability), there is no other option than using an OBM system.

The discharge of waste containing OPF (Organic Phase Fluid including Low Toxicity Fluids and esters) such as drilling cuttings will gradually be banned from a number of regions throughout the world. In the North Sea, by the end of year 2000, dumping into the sea of OPF drilling cuttings will definitely be prohibited. Nevertheless, as wells are becoming more and more sophisticated, the use of OPF as drilling fluid is actually the only viable option to succeed. For the time being, cuttings re-injection and ship-to-shore appear to be the most probable options, but they involve a significant increase in operating cost, unless R&D efforts on new separation treatments enable cuttings to be cleaned to an extremely low residual oil content. If a major breakthrough that could decrease the final residual oil content to around 0.5% or less (0.5 g of oil by 100 g of dry cuttings) can be envisaged, what will be the position of the authorities regarding cuttings discharge? Is "zero %" OPF content on cuttings before discharge reasonable and achievable? But first of all, is such a very low content measurable with precision on the rig site? This paper provides answers regarding the sensitive problems of measuring a very low oil content on a mineral substratum. A comprehensive study has been performed aiming at comparing the performances of 2 different methods used in the oil industry: direct distillation with visual reading, and distillation/pyrolysis followed by an evaluation of the Total Organic Carbon (TOC) by a Flame Ionization Detector (FID). The conclusion is that the distinction has to be made between TOC and residual oil content (ROC). The method based on thermal extraction with control of the temperature slope, enables the determination of the different origins of the organic matter and clearly demonstrate the need for criteria: even Water Base Mud (WBM) cuttings can contain organic matter (from 0 to 3%), such as kerogen, that should not be taken into consideration when evaluating oil content by thermal methods. The authors hope that the presented results could help to define a set of standard procedures to evaluate the residual oil content on cuttings. Introduction As a general trend in the industry, environmental concerns are becoming more and more stringent. The drilling industry has now to take into account new factors such as reduction of air emissions, drilling fluid release or cuttings treatments and their final disposal. These new aspects, which were not traditionally included in the drilling engineers'scope of work, are now a full part of the pre-engineering phase of a well. Drilling teams must include them in their studies, both in the technical challenge and cost evaluation. As a side product of the drilling process, cuttings are very variable in quantity, density, size, mineralogy or TOC. All those parameters depend on where the well is drilled, but also, on how it is drilled. Technical choices have a very important impact on cuttings. A phase drilled with WBM or OPF will produce very different types of cuttings, with their own particularities. As far as impact on the environment is concerned, the classification of the cuttings must consider those parameters and try to group them into categories.

The saline geological formations often display facies that are very prospective for oil. When drilling such formations, management of salted cuttings generated in areas where disposal at sea is prohibited is a real challenge. A strong impact on the terrestrial environment can be expected from salt, either on the aquifers or on the soils. An adequate stabilisation process that is well controlled is therefore necessary. The paper presents an innovative approach to the complex problem of the stabilisation of salted cuttings. Several options have been investigated during a two years study to come up with a process that is efficient, reliable and easy to implement. Leaching tests and salt content determination of the leachates were carried out, to screen the efficiency of the different processes investigated. The last option is based on a compacting process followed by a cement coating. Whereas the first three options produced mixed results, in particular with regard to stability with time, the last one led to very encouraging results. This process is currently being optimised and will lead to an industrial scale test, based on 500 kg drill cuttings, in January 2002. The implementation of this technique could constitute a major breakthrough in the drilling industry both onshore and offshore. Introduction Drilling in saline geological formation could be a real environmental issue in areas where salted cuttings disposal is not possible. Salted cuttings have to be considered as a major source of pollution in two situations:onshore drilling campaign with the risk of having an environmental impact on soil quality or fresh aquifer for exampledrilling in closed protected sea (ex: Caspian Sea): the regulation applies the zero discharge philosophy of harmful components and the only option is to bring the cuttings back to shore and to manage their disposal. At present time, there is no available technique for treating salted cuttings efficiently. For this reason, an R&D project has been launched in 2000, with the objective of setting up a stabilization treatment for the onshore disposal of these products. This paper presents the scientific approach of the problem, the results obtained and the application that could be considered. Scientific approach Stabilization consists in the fixation of the pollutant in order to limit its dispersion in the environment by air or water diffusion. Regarding salted cuttings, because of the high solubility of the NaCl and KCl chlorides, the major vector of diffusion is water. Our approach is based on the study of all possibilities to avoid the reaction between salt and water. Three scientific strategies have been considered:solubility reduction with the reaction between salts (NaCl or KCl) and oxo-anions (phosphates, silicates) which develops complex and non-soluble crystal lattices.reduction of solubilizating process kinetic: the contact surface between salt grains and water is reduced by compacting method.mechanical and chemical barrier using a matrix of cement. Due to the property of salt on cement setting, this later solution should always be considered in association with one on the two previous options.

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