The Experimental Research of Mechanical Properties of Rocks in Thermobaric Conditions

Abstract

Oil and gas account for 60% of the energy balance of Ukraine. These energy carriers have received the greatest public attention in recent years. The supply of fuel resources and their price level have a significant impact on the living standards of the population, considering that in Ukraine the consumption of natural gas alone makes up about 41% of all energy consumed, which is almost twice the European average. According to the Energy Strategy, the annual use of natural gas in Ukraine should be reduced to 49.5 billion m3 by 2030. The dynamics of natural gas consumption in Ukraine shows that the total annual needs for this type of fuel will remain at the level of 70-75 billion m3 for several years. This is due primarily to the adaptability of industry and utilities to the use of natural gas. Their conversion to consuming other fuels requires both long time and considerable costs.
 Historically, energy traditions also contributed to this. Ukraine was one of the first in the world to start producing oil and gas. In the 1920s, the first gas pipelines from Precarpathia carried the energy of life to Lviv, and later to Kyiv and Moscow. Thanks to the discovery of new fields and the use of efficient technologies, the maximum production of natural gas in Ukraine - over 68 billion m3 per year - was reached in the 1970s. At that time, the gas industry of Ukraine, in addition to its own needs, provided gas to Belarus, Moldova, partly to Russia and the Baltic republics.
 At present, Ukraine supplies only 25% of its own gas. It is possible to increase the production of own gas in Ukraine by developing of shale deposits. Their development requires the drilling of inclined and horizontal wells. The main complication which occurs when drilling such wells in clay deposits is a integrity damage of their wellbore. To prevent this, various methods are often used in order to increase the mechanical strength of the rocks that make up the walls of the wells and to increase their water resistance. It is suggested to inject fuel-bitumen fluid into the rock. Its effectiveness has been studied under thermobaric conditions on rock models and core samples. These conditions were simulated using the designed laboratory facility. The efficiency of the fuel-bitumen fluid use is due to the speed of its filtration, which is determined by the size and number of pores and cracks in which it occurs. Therefore, it is advisable to inject the fuel-bitumen fluid into clay rocks to strengthen the well walls.

Experimental studies of the carrying capacity of the drilling fluid

“…Typically, the string is close to the borehole wall and variations will occur. An incorrect location of the drill string leads to the formation of a stagnant zone in the annular space, uneven distribution of the drilling fluid velocity, an increase in the contact area of the drill pipe surface with the borehole walls and, accordingly, the torque for its rotation (Chudyk, 2009). This can be influenced by various factors, such as the diameter of the well and the drill string, the technical characteristics of the drilling pump, the parameters of the drilling fluid, the magnitude of the variation and its position in the plane of the annular section of the wellbore (Chudyk, 2008).…”