Vol 57 Iss. 2

The beginning of scientific, pedagogical and production activity of Doctor of Technical Sciences, Professor F. A. Shamshev coincided with a remarkable historical period in the life of our country – its transformation into a powerful industrial power. The geological service, which before the October Revolution was only in its infancy, began to develop rapidly.

Until recently, the main way to combat the loss of flushing fluid, well wall collapses in rocky rocks broken by tectonic fractures, was casing. But, as it is known, the use of casing pipes is associated with loss of diameters, so under difficult geological conditions, multi-column well designs are obtained and initial diameters are increased. This leads to additional complications, as the basic rule of drilling is violated: the smaller the diameter of wells, the less wall collapses and the more productive the work is, all other things being equal. Currently, this provision is generally accepted, in connection with which in all countries are moving in the exploration of solid minerals to drilling with drill bits d 46-59 mm in one-stage design of wells, ie, fix the upper unstable rocks pipes, and then drilling is carried out without casing.

Until recently, quick‑setting mixtures (BSM) for permafrost rocks were virtually non‑existent. In this connection experiments were conducted at the Leningrad Mining Institute on the development of such mixtures on a single‑salt and double‑salt basis.

In recent years, when drilling wells for water, pipes made not of steel but of other, cheaper materials are increasingly used as a production string. When penetrating mineralized waters, refusal to use steel pipes is a necessary condition for normal operation of wells. For fixing well walls in this case, asbestos‑cement, plywood‑laminated and plastic pipes are used. At present, an electrochemical method of well wall fixing is being developed.

The problem of the rate of penetration in rotary drilling of hard rocks with a sharpened cutter is reduced to the establishment of the general dependence of penetration H on time t at given parameters of the drilling mode: axial load c₀ and the number of revolutions n, and to determine the initial rate of penetration v₀. ...

Permafrost is spread over about 49.7% of the USSR territory. Drilling boreholes in frozen rocks is connected with a number of specific difficulties. Weakly consolidated loose Quaternary sediments, as well as disintegrated bedrock cemented in the frozen state by ice, are very sensitive to disturbance of their temperature state. When ice thaws, such rocks lose cohesion and stability and may become fluid. Any frozen rocks, including massive and stable rocks, are accumulators of huge reserves of cold, which also significantly complicates the drilling processes.

Constant improvement of exploration well drilling technology, caused by increasing depths, as well as the ever‑increasing complexity and diversity of geological and technical conditions, has led to the creation of a large number of different drilling fluids. Currently used drilling fluids – from air and natural gas to weighted clay solutions – have very different physical properties which have a significant impact on the drilling process and the main indicators of drilling.

The intensity of rock destruction in rotary-impact drilling depends, as is known, on a number of factors, the most important of which are the energy and frequency of impacts, the magnitude of axial load and the speed of rotation of the tool. The joint action of these factors causes a very complex nature of the drilling process, which makes the study of its regularities very difficult. Insufficient study of the mechanism of rock destruction and the process of interaction of the tool with the rock during rotary impact drilling restrains the development of this effective method of drilling.

The purpose of simultaneous with the drilling process freezing of the passed thawed rocks is to ensure their monolithicity and strength, which makes it possible to avoid complications associated with the instability of loose wet rocks, and to obtain a high core recovery.

Due to increasing depths and intensification of drilling processes , there is a practical necessity to take into account thermal phenomena in drilled wells. The temperature of the drilling fluid becomes one of the main factors determining the success of drilling operations.

The area of the Deputatskoye deposit, where drilling was carried out, is composed of lithologically monotonous sediment strata dislocated in large gentle folds of sub latitudinal and northeastern strike. In terms of physical and mechanical properties that determine the choice of diamond tools, the rocks composing the deposit can be divided into three main groups: 1) heavily crushed, often sheared medium and fine grained sandstones and sandy clay shales cemented with calcareous material and ice, VIII IX categories of drillability; 2) sandy clay shales of VIII category of drillability; 3) dense silicified, in some places hornfelsed fine grained low abrasive sandstones of X XI categories of drillability.

The most important task of exploration core drilling is to ensure high recovery and quality of core – the source material for geological and engineering geological sampling. Analysis of production data of a number of organizations engaged in drilling in permafrost rocks shows that when drilling with flushing, the core recovery is 60 70% for bedrock with moisture content of 2 5% and 20 30% in rocks with moisture content of 15% and more. In production conditions, very often in order to increase core recovery, one switches to “dry” drilling. However, the core quality deteriorates sharply. Partial or complete thawing of the core occurs, with violation of its structural characteristics.

Due to the special sensitivity of diamonds to the temperature factor, compliance with the normal thermal regime of diamond bits during drilling is one of the main conditions for their efficient operation. The normal thermal regime should be considered to be such a thermal regime at which the diamond heating temperature does not reach the value causing their oxidation, graphitization or deformation due to temperature stresses.

At electrochemical consolidation of unstable rocks in boreholes, tubular and sliding electrode designs are usually used. Tubular electrodes are the most widely used.

Creation of cement pipes directly in the wellbore is an urgent problem. Cement casing pipes can act as a production string when drilling for water, as well as isolate certain trouble zones associated with wellbore collapse or loss of drilling fluid.

Nowadays in prospecting and exploration drilling, methods of driving loose rocks based on their compaction are becoming more and more widespread. Such methods include indentation and vibratory drilling. These methods are applied in penetrating rocks of I‑III categories on drillability for the classification of rotary drilling and have high penetration rates.

Successful testing of the technical means and technology of drilling wells with bottom‑hole cleaning by cooled compressed air, developed by the Department of TTBS of the LGI under the contract with the Dalstroyproekt Institute (Magadan), allowed this method to be used in production conditions and to give a preliminary assessment of its economic efficiency in comparison with the method of drilling wells in frozen rocks “dry”, i.e. without bottom‑hole cleaning by any circulating agent.