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Drilling, mining

MECHANICAL SPECIFIC ENERGY AS A BASE LINE FOR ESTIMATION OF BEST DRILLING PARAMETERS

Set of drilling parameters is one of the key factors affecting the achievement of technical and economic factors during well construction. If the basic of design as well as drilling program are based on incorrect parameters it can lead to excessive loads on drill string and bottom hole assembly, decrease of rate of penetration and increase of well construction time as well it may affect the stability of wellbore due to loner time exposure and beating of drill string against the wellbore.

In case of directional drilling the process of selection of drilling parameters is more complicated compare to the vertical drilling due to additional parameters affecting the bottom hole assembly as well as drill string – friction factors, trajectory, depth of layers.

There are varieties of modes and systems exist in the world to forecast and approach best drilling parameters. However most of there have different limitations and there still a room for improvement. The acquisition, processing and evaluation of collected data provide a base for further estimation of best drilling parameters.

This paper approaches the practical application of the theory of selection of optimal drilling parameters based on mechanical specific energy for vertical rotary drilling mode.

APPLICATION OF CLUSTER ANALYSIS IN SELECTION AND DEVELOPMENT OF COMPLEX-ACTION DRILLING MUD ADDITIVES

Introduction of chemical compounds into drilling mud as complex-action additives is the most available, easy to implement and efficient method to improve technical-and-economic indexes of drilling. Selection and development of complex-action additives, as well as rapid selection of chemical compounds to be used as effective complex-action additives, are important tasks today.

The article presents the possibility of using electrochemical and multidimensional statistical data analyses to improve selection of the additives obtained on the basis of a wide variety of compounds enhancing drilling mud resistance to corrosion and tribotechnical characteristics.

Drilling mud tribotechnical characteristics were analyzed with the use of the modified AI-3M friction and wear testing machine manufactured in accordance with the “disk-rock” wear scheme.

Drilling mud resistance to corrosion was analyzed by electrochemical methods. The method is based on recording the steel cyclic voltammetric curves (cyclic voltammetry method) in the analyzed liquid medium. Local metal surface damage formation – repair dynamics was also monitored by galvanodynamic method.

To process the data obtained, cluster analysis was used making it possible to divide all the solutions into three groups (I, II и III). This significantly simplified the processing of the results, helped to reject the poorest additive compositions and identify unobvious relationship between drilling mud anticorrosion and tribotechnical characteristics in the groups.

Thus, the proposed method makes it possible to considerably reduce working hours of selection and development of complex-action additives, as well as improve the validity of the results obtained. The proposed methodological approach for selection and development of complex-action additives allows rejection of inefficient prototypes by the most rapid and natural way.

ESTIMATION OF TIME EFFECT ON SIZE OF WASHOUT OF LITHIFIED SHALE

Stability of wellbore is one of the main factors affecting the well construction process on every stage – staring from drilling and end run and cement casing. Instability of open hole lead to such problems as significant washouts, increase in torque and drag, stuck pipe, low quality of logging and cement job.

Lithified shale deposits create about 70% of all problems related to instability of open hole. Currently the description of the root causes of the instability of shale as well as different methods and methodic to solve this problem could be found in different open sources. Most of them reference to the time dependent wellbore instability in shale formations, meaning that longer hope keeps open – higher probability that shale will lose the stability.

As it was proven in several studies the shale stability problem is related mainly to penetration of drilling fluid into laminations / fractures (between bedding planes and through the microfractures of shale) causing the mechanical failure and thus the loading of the well with cavings. It was noticed that amount of cavings increase over the time and has been suggested that filtrate of a drilling fluid continue penetrating into the formation and bigger volume of a rock is affected.

The objective of this paper is to review the effect of time on the size of washouts in shale deposits and estimate the boundary values when shale loses the stability.

ON THE SOFTWARE OPTIMIZATION PROCESS OF DEEPENING WELLS

It is shown that to increase the stability of the drill string in order to use software control, it is necessary to introduce a correction in a consistent framework for reducing the order asterisms control object. Correcting such links should be the differentiator. Along with this, shows the block diagram of software-based control optimal control of deepening wells.

It is proved that input the PID automatic regulator control of penetration allows you to convert an unstable object control (DC) in a stable that is in the process of governance to eliminate failure in self-oscillating mode. At the same time, as a measuring device used dual-channel power meter and drive speed, made by the method of dynamic measurements. The functional diagram of the automatic control system optimal deepening wells.

It is shown that control of the process and its optimization is possible by stabilizing the control loop for inclusion in the feedback loop PID controller, and also that the optimal control of the drilling process is to manage the dynamic pounce torque on the drive shaft a drilling installation.

FEATURES OF DRY MIXTURES FOR OIL AND GAS WELLS CEMENTING

The article describes a relatively new and promising direction – the usage of dry cement mixtures in oil and gas wells construction. The key to the success of the cementing quality and is correctly selected for the specific conditions of tampon mixture. Until recently, the grouting mixture was made to cook directly in the field using mobile workshops, equipped, usually pneumatic supply and mixing of the components and then loads of ready mix in cement. In recent years, the method of producing cement mixtures in the factory, where the mixture is prepared in areas with better infrastructure and then delivered to the field, well established itself. The authors substantiate the possibility of dry cement mixtures at various downhole conditions using a mixture of appropriate additives, and describe the effect of additives on the parameters of the cement slurry. Despite a number of features that distinguish grouting mixture of traditional building, in their formulations, mainly used similar additives: water retention, pla-stifitsiruyuschie, accelerators, retarders, fiber, polymer powders. Widespread additives with special properties (materials, to prevent fluid loss, weights, oblegchiteli) due to the specific nature of downhole conditions. Special conditions of application of cement slurries and imply specific requirements applicable to the oil and gas industry in the traditional additives for dry construction mixtures. So, for polymer powders backfill material should consist of polymers with short chains and to be thermally stable when used at elevated temperatures. Many of the used oil and gas additives have complex effects on the backfill solution. Competent selection of additives, based on data about the geotechnical conditions at a specific field, provide qualitative dry grouting mixture, the use of which is the key to successful cementing operations.