Romanian Carbonate Rocks Cuttability Assessment Using Linear Cutting Tester

The paper presents the state-of-the-art on the microwave assisted mechanical rock cutting by presenting actual findings and tendencies in the field in international literature, and the activities performed during the intermediate stage and the results obtained by the team from the University of Petroşani as partner within the ERAMIN-ERANET-MIWACUT research project.

A new method for roadheader pick arrangement based on meshing pick spatial position and rock cutting verification

This paper proposes a cutting head optimization method based on meshing the spatial position of the picks. According to the expanded shape of the spatial mesh composed of four adjacent picks on the plane, a standard mesh shape analysis method can be established with mesh skewness, mesh symmetry, and mesh area ratio as the indicators. The traversal algorithm is used to calculate the theoretical meshing rate, pick rotation coefficient, and the variation of cutting load for the longitudinal cutting head with 2, 3, and 4 helices. The results show that the 3-helix longitudinal cutting head has better performance. By using the traversal result with maximum theoretical meshing rate as the design parameter, the longitudinal cutting head CH51 with 51 picks was designed and analyzed. The prediction model of pick consumption is established based on cutting speed, direct rock cutting volume of each pick, pick rotation coefficient, uniaxial compressive strength, and CERCHAR abrasivity index. And the rock with normal distribution characteristics of Uniaxial Compressive Strength is used for the specific energy calculating. The artificial rock wall cutting test results show that the reduction in height loss suppresses the increase in pick equivalent loss caused by the increase in mass loss, and the pick consumption in this test is only 0.037–0.054 picks/m3. In addition, the correlation between the actual pick consumption and the prediction model, and the correlation between the actual cutting specific energy and the theoretical calculation value are also analyzed. The research results show that the pick arrangement design method based on meshing pick tip spatial position can effectively reduce pick consumption and improve the rock cutting performance.

Kinetic criteria for evaluating the performance of roller-cone drill bits

Research objective is to work out a method of evaluating the performance of roller-cone drill bits by kinetic criteria. Introduction. It is difficult to determine the absolute criteria for the performance of rock cutting tools. Therefore, the relative values of wear resistance of the cutting structure of roller-cone bits and their relative mechanical rates of drilling are adopted as process criteria. Methods of research. The calculation and analysis of kinetic criteria for evaluating the performance of drill bits have significant differences. Taking them into account is important when studying various modifications of rock cutting tools. The set of kinetic criteria gives a picture of the relative performance of the bit using the model of the well bottom close to the real one. The set of kinetic characteristics (criteria) is conventionally called the kinetic datasheet of the drill bit. The key points of constructing an analytical model of the drill bit operation on the deformable well bottom have been considered. Scope of results. This technique provides for a comparative evaluation of roller-cone drill bits of various modifications, allows for finding feedback, i.e. searching for the appropriate combination of geometrical parameters of the rock cutting tool according to given kinetic characteristics. The versatile approach intended for use in the study of the performance of rock cutting tools allows the most complete and accurate evaluation of the influence of one factor or another on the final result.

A New Method of Central Axis Extracting for Pore Network Modeling in Rock Engineering

Characterizing internal microscopic structures of porous media is of vital importance to simulate fluid and electric current flow. Compared to traditional rock mechanics and geophysical experiments, digital core and pore network modeling is attracting more interests as it can provide more details on rock microstructure with much less time needed. The axis extraction algorithm, which has been widely applied for pore network modeling, mainly consists of a reduction and burning algorithm. However, the commonly used methods in an axis extraction algorithm have the disadvantages of complex judgment conditions and relatively low operating efficiency, thus losing the practicality in application to large-scale pore structure simulation. In this paper, the updated algorithm proposed by Palágyi and Kuba was used to perform digital core and pore network modeling. Firstly, digital core was reconstructed by using the Markov Chain Monte Carlo (MCMC) method based on the binary images of a rock cutting plane taken from heavy oil reservoir sandstone. The digital core accuracy was verified by comparing porosity and autocorrelation function. Then, we extracted the central axis of the digital pore space and characterize structural parameters through geometric transformation technology and maximal sphere method. The obtained geometric parameters were further assigned to the corresponding nodes of pore and throat on the central axis of the constructed model. Moreover, the accuracy of the new developed pore network model was measured by comparing pore/throat parameters, curves of mercury injection, and oil-water relative permeability. The modeling results showed that the new developed method is generally effective for digital core and pore network simulation. Meanwhile, the more homogeneity of the rock, which means the stronger “representative” of binary map the rock cutting plane, the more accurate simulated results can be obtained.