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.
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.
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.
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.