Rock drillability evaluation method based on rock debris nanoindentation

Abstract

The invention belongs to the technical field of oil exploration and development, and relates to a rock drillability evaluation method based on rock debris nanoindentation, which comprises the following steps: carrying out nanoindentation test on a rock debris sample, collecting a displacement load curve of an indenter, and calculating the microhardness of the nanoindentation test; calculating the mineral composition of the rock debris according to the statistical distribution characteristics of the microhardness, and converting the microhardness of the rock debris nanoindentation test into macroscopic indentation hardness; and according to the relevance between the macroscopic indentation hardness of the rock and the drillability grade value of the rock, establishing the drillability grade value of the rock, which is represented by the microhardness of the rock debris nanoindentation test. Under the conditions that the number of underground rock samples is small and the cost is high, the method breaks through the limitation of a conventional test on the size and shape of the sample, solves the problem of testing the mechanical parameters of deep rocks in the field of oil and gas drilling, is a powerful supplement to a conventional test method, and provides a basic support for optimizing a drill bit and improving the drilling speed.

Description

technical field [0001] The invention belongs to the technical field of petroleum exploration and development, and in particular relates to a rock drillability evaluation method based on cuttings nano-indentation. Background technique [0002] In oil and gas engineering, rock drillability refers to the rock's ability to resist drill bit crushing under certain drill bit specifications, types and drilling process conditions. The important parameters of stratification and drill bit selection work are of great significance to oil and natural gas drilling and prospecting drilling. [0003] There are many factors affecting the drillability of rocks, and there are currently four different evaluation methods: [0004] (1) Use the physical and mechanical properties of the rock to evaluate the drillability of the rock: that is, use the corresponding measuring instrument indoors to measure one or several mechanical properties that can reflect the essence of the broken rock as an index ...

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Problems solved by technology

[0006] (3) Evaluate the drillability of rocks by using the actual drilling speed: it reflects the comprehensive influence of various factors such as different formation rocks and technical processes, and can only be evaluated by collecting data during the actual drilling process

Since the downhole formation rock is difficult to obtain directly, the cost of downhole coring is very high, and the physical and mechanical properties of the rock are greatly affected by factors such as rock shape and size, so it is not suitable for a large number of destructive tests; the micro drilling rate evaluates the drillability of rock The method is limited by the working conditions, and the drilling footage on site has reached hundreds of meters, even thousands of meters, and the formation is changeable and heterogeneous, so the micro drilling speed is not equal to the actual drilling speed, and it is difficult to reflect the actual effect ; Since the actual ROP is restricted by many factors, such as: drilling parameters, characteristic parameters of drilling tools, hydraulic parameters, drilling equipment and technical level of personnel, etc., the actual ROP index is used to represent the drillability of rock It is temporary and local; the breaking specific work can compare the effectiveness of various drilling methods for breaking rocks, but the rock breaking specific work of various drilling methods is not a constant, so the change of rock drillability is evaluated by using the breaking specific work The law needs to be further studied

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