This paper presents the results of studying petrophysical and geomechanical properties of rocks by conducting thick-walled cylinder core tests (TWCT) - triaxial compression with flushing by various fluids. Experiments were carried out for a limited number of core samples from the Ourinskoe Field, which is a part of the Western Siberia oil and gas-bearing basin. In the framework of the study, various core testing schemes were applied, the results of experiments using different fluids for flushing were analyzed, and the optimal testing parameters (including loading rate, washing time, sample relaxation time, etc.) were selected. The result of the research is a detailed analysis of rock fragments removed by different fluids as a result of triaxial compression and subsequent destruction of a thick-walled cylinder. The paper presents the qualitative relations of the particle size distribution on the prevailing deformation patterns (elastic or plastic), analyzes some petrophysical properties of the strata that control the behavior of the system "rocks – fluid", and consider typical scenarios for TWCT experiments. The obtained experimental data served as an important source of additional information for assessing the draw-down pressure that controlled sand inflow into the wellbore, to determine its particle size distribution, as well as to calculate the size of the wire-wrapped filter liner completion for sand preventing.

Two large identical 6-cylinder Ariel JGB/6 reciprocating compressors each of 7.5 MW, are used for an underground gas storage system in (UGS) plant located in Epe, Germany. The compressors can be operated at a wide range of operating conditions, e.g. variable suction and discharge pressures, 2-stage mode during gas storage, 1-stage mode during gas withdrawal, capacity control by speed variation and valve lifters. The system should operate efficient, safe and reliable for the complete range of the operating conditions, which can be guaranteed by an extensive optimization analyses during the design stage of the project. For that purpose TNO has carried out different dynamic analyses according the API Standard 618 to be sure that the system can operate efficient, safe and reliable for the long term. In the present paper a summary of the underground gas storage system is given and the different steps in the optimization process of the system have been indicated. Finally, the results of vibration measurements after start-up of the system are presented, conclusions and remarks are given.

Abstract This paper focuses on the benefits with using electrically powered drilling equipment compared with hydraulically solutions in cold and harsh environments. Improved operational performance with higher availability of the equipment, easier installation and maintenance as well as health, safety and environmental (HSE) issues will be discussed. The paper will especially focus on permanent magnet motor (PM-motor) technology, which has recently been introduced in lifting applications and in larger drilling machinery. The possibilities when designing a PM-motor application is related to reduced size and optimized shape of equipment, as well as an enhanced safety aspect in lifting operations. Abbreviations HSE Health, Safety and Environment HPU Hydraulic Power Unit PM Permanent Magnet AC Alternating Current DC Direct Current SCR Semiconductor Controlled Rectifier MCC Motor Control Cubicle VSFD Variable Speed Frequency Drive PLC Programmable Logical Controller DnV Det Norske Vertias EN European Norm NOV National Oilwell Varco Definitions AC-motor = Induction, squirrel cage motor controlled via a variable speed frequency drive PM-motor = Permanent magnet motor controlled via a variable speed frequency drive Introduction Commonly used drilling equipment and systems are usually designed for "normal" environmental temperatures and surroundings. During the last years, both exploration and production drilling is taking place in artic areas such as the Barents Sea, and onshore in global Northern territories. Therefore the drilling equipment must be designed to operate reliable and safely also in extreme, low temperatures. This may be a problem, especially for hydraulically powered equipment which is highly temperature dependant, compromising both the working availability of the equipment, and the safety and accuracy of the machine when in operation. Another issue with hydraulically powered equipment is the risk of oil leakages and pollution of the environment. Artic areas are very vulnerable to pollution due to the rich fauna and the long decay period of chemicals due to the low temperature. The focus on "zero emission" from drilling activities to the environment in these areas is therefore highly prioritized. Hydraulic versus electric solution Traditionally, hydraulic solutions on drilling equipment have been used in the drilling machinery for many years. However, also electrical DC-motors have been used for decades, but when more power was required in smaller envelopes hydraulic solutions were preferred on the drilling machinery itself. When AC-motor technology was introduced on larger drilling machinery several years ago, this improved the controllability of electrical solutions substantially compared with DC-solutions. AC-motor technology is now common in the industry, and currently PM-motor technology is about to enter the drilling market, for various reasons. In the following section several reasons why electrical solutions are replacing hydraulically operated machinery are discussed: Health, Safety and Environmental (HSE) The focus on "zero-emission" to the environment of oil spillage and other type of pollution from the drilling industry is increasing. The advantage with an electrical system compared with a hydraulic system is obvious: There is no risk for pollution of the environment due to oil spillage, and The employers are not exposed to any toxic or poisonous liquid or vapor due to the chemical composition of hydraulic oil, and The risk and safety issues related to high pressure accumulators are avoided.